First Italian-Spanish Congress Seiano di Vico Equense and Amalfi ...

MINERALOGICA
ET
PETROGRAPHICA
ACTA
già "ACTA GEOLOGICA ALPINA"
First Italian-Spanish Congress
Seiano di Vico Equense and Amalfi
September 24-28, 1984
A. Pozzuoli, Editor
Volume XXIX-A
1985
Edito a cura dell'
ISTITUTO DI MINERALOGIA E PETROGRAFIA
DELL'UNIVERSITÀ DI BOLOGNA
direttore della rivista Gianfranco Simboli

MINERALOGieA
ET
PETROGRAPHICA
ACTA
gia "ACTA GEOLOGICA ALPINA"
Proceedings
CLAYS AND
CLAY MINERALS
First I talian':..Spanish Congress
Seiano di Vico Equense and Amalfi
September 24-28, 1984
A. Pozzuoli, Editor
Volume XXIX-A
1985
Edito a cura dell'
ISTITUTO-DI MINERALOGIA f. PETROGRAFIA
DELL'UNIVERSITA DJ BOLOGNA '
direttore della rivista Gianfranco Simboli

!
:!
~~------~------·-- -- Il--presente~volume-e- stato~-realizzato sotto
gli auspici e con il contributo finanziario:
del Consiglio Nazionale delle Ricerche
e dell'Universita di Bologna.
TIPOGRAFIA COMPOSITOR!- BOLOGNA~ 1986

PREFAC-E
This volume of Proceedings contains forty-five papers presented at the First
Italian-Spanish Congress on Clays and Clay Minerals together with eight General
Lectures and those extended abstracts (41) approved by the Scientific Committee
for presentation at the poster session.
The Congress was held in Seiano di Vico Equense and Amalfi (Italy) on
September 24-28, 1984, and organized by the Italian and Spanish clay groups.
Although a binational meeting, the Congress was also attended by clay scientists
from Czechoslovakia, France, Hungary, Israel, the Netherlands, Portugal and
Venezuela.
The Proceedings are an example ofthe Gruppo Italiano dell'AIPEA's policy to
establish useful contacts with individual European and non-European clay
groups in ·order to develop better relationships from both the personal and scientific
points of view.
The publication of these Proceedings was made possible mainly -through the
financial support of the National Research Council of Italy, the University of
Naples, the University of Bologna and the Vesuvius Observatory at Ercolano.
Other economic assistance, both direct and indirect, was received from Banco di
Napoli, Consejo Superior de Investigaciones Cientificas - Madrid, Dipartimento
di Geofisica e Vulcanologia ,dell'Universita degli Studi di Napoli, Ente Provinciale
per il Turismo di Salerno, Gruppo Italiano dell'AIPEA, the Moon Valley and
Scrajo Hotels in Vico Equense, Ideal-Standard SpA - Milano, Instituto Espafiol
de Santiago - Napoles, Istituto di Chimica Agraria dell'Universita degli Studi di
Napoli, Istituto di Ricerca per la Protezione Idrogeologica - Cosenza, Istituto
Sperimentale per la Nutrizione delle Piante - Roma, Istituto Sperimentale per lo
Studio e la Difesa del Suolo - Firenze, Italcementi SpA - Bergamo, Philips SpA -
Monza, Regione Calabria and Regione Campania. Valuable assistance was also
provided by the Mayors and local authorities of Amalfi, Casoria and Vico Equen­
. se in Campania, and of Spinazzola in Apulia.
I wish to express my deepest gratitude to Professor Jose Maria Serratosa,
President of the Scientific Committee, Professor Lorenzo Mangoni, Dean of the
Faculty of Science at the University of Naples, and the members of the Scientific
Committee for all their effort and cooperdtion in the more important scientific
and organizational aspects of the Congress.
Particular thanks are due to Doctor Vincenzo Rizzo and Professors Purificaci6n
Fenoll Hach-Alf, Jose Antonio Rausell-Colom, Jose Linares, Naris Morandi,
Luigi Dell'Anna, Fernando Ve.niale and Gianfranco Simboli for their fundamental
contributions in both key administrative and scientific questions related to the
Congress itself as well as the production of these Proceedings.
V

All the papers presented in this volume were critically read and the English
corrected by Doctor Sally Wentworth Rossi, an extensive work for which sincere
appreciation is expressed here. Thanks also are due to Professor Girolamo Pompameo
for his careful revision of the Italian version of the Memorial~to Professor-­
Juan Luis Martin Vivaldi. Almost the figures reproduced in the Proceedings were
redrawn by Antonio and Ferdinando Maria Musto.
This volume of Proceedings is dedicated to the memory of Professor Juan Luis
Martin Vivaldi.
Antonio Pozzuoli
Editor
VI
,,.

. SCIENTIFIC COMMITTEE
President
JOSE MARIA SERRATOSA
Secretaries
LUIGI DELL'ANNA and FERNANDO VENIALE
Members
EMILIO GALAN, JOSE LINARES, CARLO PALMONARI,
MARIA SANCHEZ-CAMAZANO, PIETRO VIOLANTE
REFEREES
The Editor is grateful to the following scientists who acted as referees
during the preparation of this volume
R. ALLMAN J. KONTA LTH. ROSENQVIST
S. DE AzA L KRAUS E. Rurz-HrTZKY
J.A. BAIN ,-B. KUBLER J .D. Ru'SSELL
E. BARAHONA G.'LAG_ALY M. SANCHEZ-CAMAZANO
J. BENAYAS J. LINARES J. SANZ
J. CORNEJO F. LoPEZ-AGUAYO R.A. ScHOONHEYDT
L. DELL' ANNA P. MATTIAS C.J. SERNA
E. GALAN M. 0RTEGA HUERTAS U. SCHWERTMANN
A. GARCIA VERDUCH C. PALMONARI A. SINGER
B.A. GOODMAN J .L. PEREZ RODRIGUEZ J. SRODON
J .L. GUARDIOLA A. PozzuoLI J. TORRENT
M.H.B. HAYES J .A. RAUSELL-COLOM F. VENIALE
L. HELLER-KALLAI G.G. RISTORI P. VIOLANTE
VII

CONTENTS
Page
Preface
Juan Luis Martin Vivaldi
V
XIII
GENERAL LECTURES
Do Clay Minerals Act as Catalysts in the Thermal Alteration of Organic Matter in
Nature ? Problems of Simulation Experiments,
b:y LISA HELLER-KALLAI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
The Process of Bentonite Formation in Cabo de Gata, Almeria, Spain,
by JOSE LINARES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Quantitative Determinations of the Fine Structural Features in Clays by Modelling of
the X-ray Diffraction Patterns, .
by CYRIL TCHOUBAR . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Crystalline Defects in Layer Silicates,
by MANUEL RODRIGUEZ GALLEGO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
High-Resolution MAS-NM"R Spectra of Layer Silicates. Ordering of Tetrahedral
Cations,
by JOSE MARIA SERRATOSA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
The Upper Basin of the Ofanto River: Some Grain Size, Mineralogical and Chemical
Factors which Show the Sedimentation Pattern and Mineral Source,
by LUIGI DELL'ANNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
The Role of Microfabric in Clay Soil Stability,
by FERNANDOVENIALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lOl
Crystalline Minerals and Chemical Maturity of Suspended Solids of Some Major
World Rivers, "-
by JIRI KONTA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
SECTION I: SURFACE CHEMISTRY AND INTERACTIONS
Measurements of Total and External Surface· Area of Homoionic Smectites by p­
Nitrophenol Adsorption,
by G .G. RrsTORI, E. SPARVOLI, P. Fusr, J .P. QUIRK, and C. MARTELLONI . . . . . . . . . . . . . . . . 137
Adsorption of Chloropropham (CIPC) by Clay Minerals and Soils,
by G. Dros CANCELA, J.A. GUILLEN ALFARO, and S. GONZALEZ GARCIA . . . . . . . . . . . . . . . . . . 145
Interaction of Chlordimeform with a Vermiculite-Decylammonium Complex in
Aqueous and Butanol Solutions,
by J.L PEREZRODRIGUEZ, E. MORILLO, andM.C. HERMOSIN . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Anion-Exchanged Forms of Lithium Hydroxide Dialuminate,
by G. MASCOLO ' ...... ··............................................................ 163
Interaction of Chlorthiamid with AI- and Ca-Morttmorillonite,
by P. Fusr, M. FRANCI, and G.G. RrsTORI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Abstracts
179
SECTION 11: GEOLOGY AND GENESIS
Hydrothermal Solutions Related to Bentonite Genesis, Cabo de Gata Region, Almeria,
SE Spain,
by E. CABALLERO, E. REYES, J. LINARES, and F. HUERTAS.............................. 187
IX

The Origin of Palygorski,te in Villamayor Sandstone, Salamanca, Spain,
by M.A. VrcENTE andJ. VICENTE-HERNANDEZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
Weathering Products of Vulture Volcanites, Lucania, Southern Italy,
by M. Dr PIERRO, M. MoRES!, and F. VuRRo ................... '· ._ .._.. '-"--·-~--~'-'-·-·~,-·" ,_____205_.,,._.__ ._
Compositional Characteristics of «Argille Varicolori» from Outcrops of Bisaccia and
Calitri, Avellino Province, Southern Italy,
by M. Dr PIERRO and M. MoRES! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Mineral Composition of the Jurassic Sediments in the Subbetic Zone, Betic Cordillera,
SE Spain,
by M. 0RTEGA HUERTAS, I. PALOMO DELGADO, and P. FENOLL HACH-ALI . . . . . . . . . . . . . . . . 231
Pelagic Cretaceous Black-Greenish Mudstones in the Southern Iberian Paleomargin,
Subbetic Zone, Betic Cordillera,
by A. LOPEZ GALINDO, M.C. COMAS MINONDO, P. FENOLL HACH-ALI, and M. 0RTEGA
HUERTAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
Clay Minerals of Miocene-Pliocene Materials at the Vera Basin, Almer-'ia, Spain.
Geological Interpretation,
by E. GALAN, M. GONZALEZ LOPEZ, C. FERNANDEZ NIETO, and I. GONZALEZ DIEZ 259
Clay Mineral Distribution in the Evaporitic Miocene Sediments of the Tajo Basin,
Spain,
byJ.M.BRELL,M.DoVAL,andM.CARAMES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
Fluvial Pelitic Supplies from the Apennines to the Adriatic Sea. I - The Rivers of the
Abruzzo Region,
by L. TOMADIN, P. GALLIGNANI, V. LANDUZZI, and F. 0LIVERI ......... :. . . . . . . . . . . . . . . . 277
Polygenesis of Sepiolite and Palygorskite in a Fluvio-L

Perturbation of V oH Infrared Frequencies by Inter layer-C~tions in Homoionic Vermiculites.
Structural Implications,
by J .A. RAUSELL-COLOM and J .M. SERRATOSA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
Abstracts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
SECTION IV: SOIL MINERALOGY AND GEOCHEMISTRY
Mineralogical Characteristics of the Fine Fraction of Soils from the Emilia-Rorhagna
Region, Northern Italy,
by G. FELICE, G.C. GRILLINI, N. MoRANDI, and G. VIANELLI . . . . . . . . . . . . . . . . . . . . . . . . . . 437
Quantitative Determination of Minerals in Clays from Profiles in the West of Central
Spain by Differential Scanning Calorimetry,
by M.T. MARTIN PATINO, C. TURRION, M .V. Roux, J. SAAVEDRA, and A. MILLAN . . . . . . . . . . 455
Mineralogical and Geochemical Relationships in Pedological Profiles of Soils,
by N. MORANDI, M.C. NANNETTI, and G.C. GRILLINI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461
On the Effectiveness of the Extractable Forms of Fe, Al and P in Identifying Soil
Chronosequence Terms,
by E. ARDUINO, E. ZANINI, E. BARBERIS, V. BoERO, and F. AJMONE MARSAN . . . . . . . . . . . . 473
Geochemistry of Available Micronutrients in Soils from Vega de Velez, Malaga,
Spain,
by A. Rurz, S. JAIME, A. AGUILAR, E. BARAHONA, F. HUERTAS, and J. LINARES . . . . . . . . . . . . 483
Geochemistry of Soils from Peridotite in Los Reales, Malaga, Spain,
by A. YUSTA, E. BARAHONA, F. HUERTAS, E. REYES, J .. YANEZ, and J. LINARES 489
The Effect of Gypsum on the Poral System Geometry in Two Clay Soils,
by A.B. DELMAS, C. BINI, and J. BERRIER ................................· . . . . . . . . . . 499
511
Abstracts ······ ········ ... ········. ······ ...... ······· ..... ······· ·············
SECTION V: CERAMIC CLAYS
Drying Properties of Ceramic Clays from Granada Province, Spain,
by E. BARAHONA, F. HUERTAS, A. PozzuoLI, and J. LINARES ........................... .
Clays and Complementary Raw Materials for Stoneware Tiles,
byB.FABBRiandC.FroRI ......................· ................................. .
Manufacture of Heavy-Clay Products with the Addition of Residual Sludges from
Other Ceramic Industries,
by C. PALMONARI and A. TENAGLIA .................... : . ......................... .
High Temperature Reactions and Use of Bronze Age Pottery from La Mancha, Central
Spain,
by J. CAPEL, F. HUERTAS, and J. LINARES ...... ········· ····· ............ ·········.
Firing Properties of Ceramic Clays from Granada Province, Spain,
by E. BARAHONA, F. HUERTAS, A. PozzuoLI, and J. LINARES ........................... .
Degradation of Ceramic Sculptures on the Cathedral of Seville,
by C. MAQUEDA, J .L. PEREZ RODRIGUEZ, and A. JUSTO ERBEZ ......................... .
Abstracts ................................................................... · .. .
521
535
547
563
577
591
599
SECTION VI: GEOTECHNICAL PROPERTIES AND APPLICATIONS
Mineralogical Composition and Geotechnical Properties of the Pelitic Antognola Formation
from the Baiso Area, Northern Apennines,
by A. CANCELLI, A. FAILLA, and N. MORANDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
XI

Geomorphological and Geotechnical Aspects of the Fissured Clays of Lucera, Apulia
Region, Southern Italy,
by C. CHERUBINI and A. GUERRICCHIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621
Geological and Mineralogical Aspects of and Geotechnical Approach to the _l:a!ldsliges_ ..
in the «Crete Nere» Formation in the Noce River Valley, Lucania, Souiliern Italy,
by L. DELL'ANNA, M. Dr PIERRO, A. GUERRICCHIO, and G. MELIDORO . . . . . . . . . . . . . . . . . . 629
Upper Miocene Clays from Vallone Salina, SW Cosenza, Calabria: Textural and
Compositional Characteristics with Geotechnical and Paleoenvironmental Aspects,
by F. BALENZANO, L. DELL'ANNA, M. Dr PIERRo, and V. Rrzzo ............... , . . . . . . . . 647
Techniques of Analysis for Lithostratigraphic Correlations in the Subsoil of'Milan,
by V. FRANCANI, L. ScEsr, F. VENIALE, A. CANCELLI, F. PREVITALI, A. FARINI, and I. Assr
............... ····· ..... ······ ············ .................... ······· ······· .. .
Paleontological, Mineralogical and Geotechnical Characterization of Nardo Clays,
by L. ALBANESE, C. CHERUBINI, M. Dr PrERRO, C.I. GrAsr, F.M. GUADAGNO, A. PEDE, and
F.P. RAMUNNI ................................................................. .
Effects of Particle Geometry on Treatment and Processing of Clays,
by R.A. KUHNEL ............................................................... .
On Some Characteristics of Compacted Cohesive Soils,
by G. DENTE and L. ESPOSITO .......... ': ........................................ .
Abstracts ............................................................. , ....... .
AUTHOR INDEX
SUBJECT INDEX
·········· ...... ··········· .. ········ ······· ................. .
········ ······ ····· ········ ............ ····· .. ······ ......... .
661
671
681
693
703
713
717
,I,
11'
I'
'
XII

Juan Luis Martin Vivaldi

Il Professore Juan Luis Martin Vivaldi nacque a Granada illO Maggio 1918
e mori prematuramente a Madrid il 7 Gennaio 1974, stroncato purtroppo da
un fulmineo infarto.
Dotato di eccezionale talento, compi con successo gli studi secondari, conseguendo
poi nel 1940 la laurea in Scienze Chimiche presso l'Universita di
Granada. Da allora ha inizio una feconda attivita di pensiero e di ricerca che
nel volger di pochi anni, lo porta ad affermarsi parallelamente nel campo
universitario ed in quello strettamente scientifico. Dopo il dottorato-in Scienze
Chimiche conseguito con la piu alta votazione ed il plauso della Commissione
nel 1949 a Madrid, difendendo la Tesi « Hidrataci6n de silicatos de
estructura laminar con cationes de cambio>>, ed un intenso periodo di studi
relativo all'ambito chimico-fisico dei minerali delle argille, svolto con zelo e
passione negli Stati Uniti d' America dal Maggio 1950 al Dicembre del1951 in
collaborazione con il Dott. S.B. Hendricks, Martin Vivaldi risulta vincitore
della cattedra di Cristalografia, Mineralogia y MineralotecrLia a Granada nel
1962, e vi insegna per sei,. anni ottenendo successivamente, per concorso di
merito, il trasferimento all'UJ?-iversita di Madrid dove continua a profondere
ai giovani con lungimiranza, impegno e rigore morale il meglio della sua
profonda dottrina.
Altrettanto intenso il suo curriculum scientifico in seno al Consiglio delle
Ricerche Spagnolo dove percorre, in rapida, brillante successione, tappe
fondamentali per la Sua carriera di studioso: borsista a Granada gia nel 1946-
47, assistente alla Sezione Chimico-Fisica nel1948-49, collaboratore scientifico
dall950 al1954 sempre a Granada e quindi ricercatore dal1955 al1971.
Significativi in questi anni tal~.mi delicati incarichi affidati alla singolare
competenza ed esperienza di Martin Vivaldi che dal 1957 al 1968 e responsabile
della Sezione di Mineralogia dell'Istituto di Ceramica e Vetro del Patronato
Juan de la Cierva di Granada nonche Vice Direttore della Stazione
Sperimentale del Zaidin e capp della locale Sezione -di Mineralogia delle
Argille, precisamente dal 1962 al 1968. Dall'Ottobre del 1968 la scienza ufficiale
ne sottolinea le grandi capacita scientifico-organizzative, ricorioscendo- _
lo ariche capo delle Sezioni ma~rilene di Mineralogia dell'Istituto Lucas
Mallada e del Museo di Scienze Naturali nonche di Mineralogia e Tecnologia
delle Argille del Dipartimento di Geologia Economica. Nel 1972 eccolo Profesor
de Investigaci6n, il piu alto dei riconoscimenti scientifici e Consejero
Adjunto, quest'ultima, alta e prestigiosa carica politico-scientifica.
XV

I I
'I
I'
L'attivita di ricerca del Professore Martin Vivaldi ando abbracciando nel
tempo numerosi campi delle Scienze della Terra. I suoi interessi riguardavano
tematiche di Mineralogia e Cristallochimica, la Geochimica, la Genesi
Minerale e la Petrogenesi, la Chimico-Fisica e la Reologia~delle Argille; il
campo dei Giacimenti e quello della Sintesi Minerale, quest'ultima estesa
anche all'approfondimento di ricerche specifiche condotte su alcuni fillosilicati
e zeoliti in condizioni di bassa temperatura e ciistallinita. Originale fu il
suo contributo alia Vulcanologia ed alia Geologia Sedimentaria, quest'ultima
comprendente anche tematiche di carattere pedologico. Vennero cosi affrontati
e risolti, per sua iniziativa, con ampia interdisciplinarieta, studi relativi
ai giacimenti caolinici e bentonitici di Spagna e Marocco, ai sedimenti triassici
e cretacici nonche a quelli argillosi di bacini endoreici spagnoli, ed ai suoli
delle Province di Granada e Salamanca. Attraverso tali studi si consolidava in
tempi brevi una Scuola agile e moderna nel campo della Geologia e della
Geochimica della Dinamica e dei Processi di Alterazione e di Neoformazione
della Superficie Terrestre, che degnamente si affiancava in Europa a quella
francese di Strasburgo. Martin Vivaldi si distinse, in particolare, per alcune
ricerche riguardanti il delicato settore dei minerali a strati misti, dando
particolare risalto a quelli di tipo corrensite. Nacque cosi l'esigenza del neces-
~~-·-~---~~.9:rjQ_erofonciimento della 11

Per la sua alta esperienza in campo geologico, nel 1964 tenne conferenze
negli Stati Uniti d'America sul Tema delle Bentoniti e nel1968 fu nominata
membro del Comitato Esecutivo Internazionale «Kaolin Correlation Program>>,
quest'ultimo operante sotto il Patrocinio della UNESCO. Per i suoi
contributi dati al campo dell'Analisi Termica Differenziale, svolse funzioni di
Liaison Officer per la Spagna, nell'ambito dell'International Confederation
for Thermal Analysis.
Quando ebbi la ventura di conoscere il Professore MartfnVivaldi, Don Juan
cosi come affettuosamente a pochi era concesso di chiamarlo, erano gli inizi
del 1970. Fui da lui accolto come un figlio, e come un figlio premuroso mi
accorsi subito che reagiva con estremo vigore alle tante difficolta che il nuovo
ambiente universitario di Madrid gli andava procurando di giorno in giorno.
Era troppo forte e troppo grande la sua personalita da evitargli problemi di
ogni genere. E reagiva cosi con illavoro, con l'organizzazione della Reunion
Hispano-Belga de Minerales de la Arcilla che si sarebbe celebrata di li a poco,
proprio a Madrid, con la preparazione della International Clay Conference del
1972 che, anche per. suo merito, avrebbe visto la Spagna fra le protagoniste di
tale importante manifestazione. Alle difficolta sopra accennate, egli reagiva
inoltre, favorendo il completamento delle Tesi dottorali da lui dirette, e
programmando le future linee di ricerca che dovevano abbracciare il decennia
1970-1980. Di Tesi dottorali ne diresse dieci.
Questa in sintesi la luminosa carriera di Martin Vivaldi, uomo di straordinario
sapere e di elevate d.oti umane, ricco di interessi e di problematiche, che
lo videro in rapporto con var:i Paesi del mondo tra cui l'Italia alla quale era
anche legato da vincoli affettivi per antica discendenza.
Infaticabile organizzatore di gruppi di ricerca non solo a Granada, ma
anche altrove, cultore per diretta esperienza di studio e di soggiorno in diversi
Paesi anglosassoni, della lingua inglese, sempre partecipe a congressi di ogni
livello, animatore di ogni iniziativa scientifica, Egli resta percio uno Scienziato
insigne - chimico, mineralogista, geologo - del nostro tempo, sempre
sorretto da illuminata intelligenza ed incisiva versatilita. La Sua valentia
scientifica si armonizzava con la bonta del carattere, aperto, gioviale, socievole,
anche se triste per natura, sempre pronto a cogliere e penetrare la psicologia
altrui, amante del bello in senso la to, in una continua ricerca della verita.
Da tale sintonia di valori emerge la forte personalita dell'Uomo che dedicando
una vita iritera alla scienza, e oggi, a buon diritto, universalmente rimpianto
ed ammira to.
A. Pozzuoli
XVII

Professor Juan Luis Martin Vivaldi was born in Granada, Spain on May 10,
1918 and died prematurely at the age of 55, struck down by a heart attack in
Madrid on January 7, 1974.
Martin Vivaldi was a man of exceptional talent. After successfully completing
his secondary studies, in 1940 he received his undergraduate degree in Chemistry
from the University of Granada. This marked the beginning of a long period of
fertile thought and research which in just a few years led to his parallel affirmation
in both teaching and strictly scientific endeavours. In 1949 he received his
doctor's degree in Chemistry with highest honours from the University of Madrid,
defending the thesis «H idrataci6n de silicatos de estructura laminar con cationes
de cambio». After an intense period of study relative to the physical-chemistry of
clay minerals carried out with enthusiasm and passion in the U.S.A. (May 1950
to December 1951) in collaboration with Dr. S.B. Hendricks, Martin Vivaldi was
(lppointed full professor ofCrystallography, Mineralogy and Mineral Techniques
at the University of Granada in 1962. After 6 years in Granada, he applied for and
received a transfer to the University of Madrid where he continued to dedicate his
time and boundless energy to the teaching of young people, imparting the best of
his profound doctrine with far-sightedness, care and moral exactitude.
Equally intense was his scientific curriculum as part of the Spanish Research
Council where in rapid, brilliant succession he occupied the following positions
at the Experimental Station of Zaidin in Granada, fundamental for the development
of his career as a scientist: research fe}low, 1946-47; assistant in the
Physical Chemistry Section of the Experimental Station of Zaidin, 1948-49;
s~ie~tific collaborator, 1950-54 and research associate 1955-1971. During these
years, various positions held by Martin Vivaldi were of particular significance,
·representative of his singular competency and experience. From 1957 to 1968, he
was Director of the Mineralogy Section of the Instituto de Ceramica y Vidrio del
Patronato Juan de la Cierva of Granada as well as the Vice Director of the
Experimental Station· of Zaidin and head of the Clay Mineralogy Section from
1962 to 1968. In October 1968, in recognition of his scientific and organizational
abilities, Martin Vivaldi was appointed head of the Madrid Section of Mineralogy
of the Lucas Mallada Institute and of the Museum of Natural Science as well as
Chairman of the Clay Mineralogy and Technology Section in the Department of
Economic Geology at the University of Madrid. Four years later, in 1972, he
received the titles of Profesor de Investigaci6n, the highest possible scientific
recognition and Consejero Adjunto, a prestigious, high-level, scientific-political
position.
XIX

i'
I
I'
I
The research activities of Professor Martin Vivaldi with time encompassed
numerous areas of earth science. His interests included topics in mineralogy and
crystal chemistry, geochemistry, mineral genesis and petrogenesis, physical chem-
. is try and rheology of clays, clay deposits and mineral synthesis. In particular,
Martin Vivaldi's work on mineral synthesis included thorough studies of several
layer silicates and zeolites at low temperature and crystallinity. His original
contributions to volcanology and sedimentary geology were exceptional and in the
latter area also included topics in pedology. Because of his initiative, widely
interdisciplinary studies were confronted and carried to completion regarding
kaolinite and bentonite deposits in Spain and Morocco, Triassic and Cretaceous
sediments and clay mineral deposits of Spanish endorheic basins, and the soils of
the Provinces of Granada and Salamanca. In a short time, these studies led to the
consolidation of an agile and modem school in the fields of geology, geochemistry,
dynamics of alteration processes and neoformation of the earth's crust,
which took its place in Europe alongside that of the French school in Strasbourg.
Martin Vivaldi stood out, in particular, for certain research regarding the complex
sector of mixed-layer minerals, with particular emphasis on corrensite type minerals.
This research served as the startingpoint for further important studies on the
nature of the interstratified clay minerals which could be distinguished on the
basis of their expansion characteristics and peculiar behaviours during various
-· ---------thermal treatments.
Martin Vivaldi was expert in many instrumental techniques, excelling, among
others, in X-ray diffraction, thermal analysis and electron microscope techniques.
He was one of the pioneers, in Spain, in the field of differential thermal analysis
where he was known for its application in the field of clay-organic complexes and
for his considerable contribution to the study and the characterization of minerals
such as sepiolite and attapulgite. Of particular value in the field of X-ray
diffraction analysis were the modifications he developed for the Philips Camera
which made it possible to distinguish and study the diffraction effects at very low
angles by some types of swelling clay minerals.
The didactic activity of Professor Martin Vivaldi was intense and profitable for
all those who had the fortune to know and follow him, both before and after
receiving their degrees. His courses on crystallography and mineralogy, geochemistry,
crystal chemistry and pedology were of the highest level. He also taught
fundamental and integrative courses on X-ray diffraction analysis, geology and
mineralogy of clays and differential thermal analysis. He was particularly clear in
discussion and presenting details of all topics, but especially so for those representing
starting points for wider and more interesting studies. Because of his
grand communicative ability, he gave to everyone, sooner or later, the possibility
to be included in always modem and constructive cultural discussions.
Because of his wide experience in the field of geology, in 1964, Martin Vivaldi
held conferences in the U.S.A. on the subject of bentonites and in 1968 was
XX

nominated a member of the International Executive Committee of the «Kaolin
Correlation Program» operating under the UNESCO. His contributions in the
field of differential thermal analysis, led to his role as Liaison Officer for Spain
within the framework of the International Confederation for Thermal Analysis.
I had the good fortune to know Professor Martin Vivaldi, Don Juan, as few
were affectionately permitted to call him, at the beginning of the 1970's. He
accepted me like a son and like an affectionate son, I soon became aware that he
reacted with extreme energy and vigour to the many difficulties arising from the
new university environment in Madrid. He was too strong and his personality too
powerful to allow him to avoid any type of problem. This was his reaction to work,
to the organization of the Reunion Hispano-Belga de Minerales de la Arcilla
which was soon to be held in Madrid and to the preparation of the 1972 International
Clay Conference, which, thanks to Martin Vivaldi, was held in Spain. In
addition to such activities as these, Professor Martin Vivaldi was also involved in
advising studens in their thesis research and programming future areas of
research for the 10-year period 1970-1980. Hewas advisor for 10 doctoral theses.
This, in synthesis was the luminous career of Martin Vivaldi, a man of extraordinary
knowledge and noble human qualities, with a wide range of interests that
brought him into contact with many people from many countries throughout the
world, including Italy, for which he had a particular affection because of ancestral
ties. ,
Untiring organizer of research groups not only in Granada, but also elsewhere,
skilled in English, through dir'ect experience during studies and visits to various
Anglo-Saxon countries, active participant in congresses of all types, leader of.
numerous scientific initiatives, for these reasons Martin Vivaldi stands out as an
illustrious scientist - chemist, mineralogist, geologist - of our time, always
upheld by an illuminated intelligence and incisive versatility. His scientific prowess
was in complete harmony with the goodness of his character, open, jovial,
sociable, even though sad by nature, always ready to receive and understand the
feelings of others, lover of the good in life, in continuous search for the truth.
From this syntony of values emerges the strong personality of Professor Juan Luis
Martin Vivaldi, a man, who, after dedicating his whole life to science, is today,
with reason, universally missed and admired.
A. Pozzuoli
XXI

General
Lectures

Miner. PetrQgr. Acta
Vol. 29-A, pp. 3-16 (1985)
Do Clay Minerals Act as Catalysts in the Thermal
Alteration of Organic Matter in Nature?
Problems of Simulation Experiments
LISA HELLER-KALLAI
Department of Geology, Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
ABSTRACT- A review of the literature on the evolution of kerogen in rocks of
different lithology, on bitumen associated with carbonates and silicates-in
the same rocks and on the effect of natural thermal events on the decomposition
of kerogen does not provide conclusive evidence for systematic catalytic
effects of minerals on kerogen catagenesis. In laboratory experiments with
kerogen in open systems two effects of clay minerals were distinguished:
retention and catalysis. It is tentatively concluded that with indigenous clays
retention of organic matter may be more important than catalysis. On
migration the organic matter encounters fresh mineral surfaces, which may
act as catalysts. Such surfaces may also be exposed in response to mechanical
effects.
Model experiments with carboxylic acids showed that. different features of
clay minerals cause retention, decarboxylation and cracking at elevated
temperatures. Conversion of the acidic into the ionic form, which occurs
more readily ··with trioctahedral than with dioctahedral minerals, causes
stronger retention of the organic matter by clays. Conversion of. montmorillonite
to an 'Organo-montmorillonite increases retention of carboxylic
acid but reduces catalytic activity ··of the clay and conversion of the acid to
the ionic form. Organo-clays may most closely resemble indigenous clays in
oil-prone. rocks. Oxidation-reduction reactions between the organic matter
and the mineral matrix are strongly dependent on the rate of removal of the
reaction products.
The experiments with carboxylic acids demonstrate that the interactions
between clay minerals and organic matter differ in open, semi-closed and
closed systems, which may simulate reactions in different types of pores in
rocks. No single set of experimental conditions can be expected to reproduce
the complex processes occurring in nature. Pooling the products obtained
under different conditions with mixtures of clay minerals may lead to improved
simulation experiments.
Introduction
It . is now generally accepted that
petroleum is derived from _kerogen,
insoluble macromolecules formed by
diagenesis of organic debris on burial
in a subsiding basin. The elemental
composition of kerogen, which depends
on the parent material, follows
different evolution patterns on burial.
These are conveniently expressed
in diagrams of the type shown in

--·----~-
4 L. Heller-Kallai
11,
11
11
, I
1.
i
I'
! ~
I
~
,l'!
u
.,.
.s 1.5
"'
..._
u
"' :::.11
1.0 -1--1~1--t-----f-----· -·-· ··-··
0.5
0 20 30
~-·a;·c-
il-tomic R"ai:io (x 1oo)
Fig. 1 - Elemental evolution of various types of
kerogen (After DURAND, 1980c.) The arrows
indicate increasing evolution.
Fig. 1. On maturation kerogen begins
to generate liquids and, at greater
depth, gas as shown in the figLJ.re. At
the oil-generating stage cleavage of
heterobonds in the kerogen produces
fragments, which may be converted
to petroleum hydrocarbons (HC's).
These HC's or their precursors migrate
from source rocks to reservoirs,
where they accumulate. To account
for the relatively low temperatures at
which cracking reactions occur
( > (A)

Do Clay Minerals Act as Cataly;ts in the Thermal ... 5
and «open pores>> (B). Lighter hydrocarbons
could move in and out of
pores B, but probably only out of A.
The presence of closed pores in natural
systems was demonstrated by
several investigators (e.g. SAJGO
et al., 1983) by comparing the solventsoluble
extract of total rock samples
with that from the same rock after
crushing. The difference was attributed
to bitumen in closed pores.
BRUKNER & VETO (1981) found
that this difference decreased with
increasing carbonate content of the
rocks, indicating that fractionation
was more efficient in marls than in
carbonates. In modelling such systems,
should an open scheme be
adopted, in which the products are
removed from the reactants and
secondary reactions are r~duced, a
not be reviewed here (e.g. FOSCO­
LOS & POWELL, 1979; JOHNS,
1979; 1982; PEARSON et al., 1982;
HURST, 1982). Although there are
consistent relationships between
changes in clay minerals and diagenesis
of the organic matter, a
causal connection has not been definitely
established.
In the present paper an attempt is
made to review the information
available on possible catalytic effects
. of clay minerals on the evolution of
kerogen in nature and in laboratory
simulation experiments. Some of the
conclusions will be discussed in the
light of results obtained in experiments
with carboxylic acids.
Natural systems
closed one or an interm~diate
arrangement in which products may
slowly diffuse or be transported away
from the reactants?
The problem of the transporting
medium is no less complex. It may
vary with the degree of maturation
of the kerogen. TISSOT & WELTE
(1978) suggest that in argillaceous
sediments the carrier is water at shallower
depths but on deeper burial
migration takes place in an oil or gas
, phase. The pores are water wet. The
nature of any organo-clay complexes
formed and the acidity of potential
clay catalysts will, of course, be.
affected by the fluid phase present.
The correlation of oil migration ··
and HC cracking with dehydration
If minerals catalyse the decomposition
reactions, the evolution path
of kerogen will depend upon the surrounding
medium. DURAND (1980b)
reported that a type Ill kerogen disseminated
in a clay matrix (predominantly
illite and kaolinite) was identical
with kerogen in coal beds intercalated
between these clays, suggesting
that kerogen composition and
burial history alone determined the
evolution path. WILLIAMS & DOUG­
LAS (1981) found that the organic
matter in carbonate, clay and shale
fractions of Kimmeridge clay was
similar, with minor variations in the
carbonate rocks. They attributed
these to catalytic effects of carbonates.
and diagenesis of clay minerals has
In contrast IVANOV &
been extensively discussed and will SHCHERBAR (1983) concluded that

~- -- ~-- -----~-===----------...... -
6 L. Heller-Kallai
-- 1 I· ,
l
lithology significantly influenced the
nature of the organic matter and that
more He's were formed in clay than
in carbonate rocks. They based their
conclusions on comparison of
kerogen from various basins,
irrespective of differences in the parent
material and in the physical
properties of the rocks. JONES (1984)
observed systematic differences between
oils derived from carbonates
and shales, but attributed these to
variations in the parent material and
in the porosity and permeability of
the rocks.
In natural systems it is always dif- .
ficult to distinguish between the
effects of the physical properties of
' -----~~--tlie-rocks-:-such as-po~osi ty' ~~cl-p~ssible
catalytic activity. This problem
was overcome in studies of SPIRO
(1980) and JEONG & KOBYLINSKI
(1983), who examined the bitumic
nous fraction associated with carbonates
and silicates of the same rock
samples (oil shales from Israel and
Colorado, respectively) by stepwise
degradation of the mineral components
followed by extraction with
organic solvents. The data in Table 1
demonstrate that there-are some resemblances
but also some differences
between the two occurrences, confirming
Spiro's view that, although
there is preferred adsorption by silicates,
it is limited by the availability
of the components during deposition
and early diagenesis. This concept received
further support from similar
studies on occurrences which had
been affected by natural thermal
events: oil shales from Israel which
were partly pyrolysed by heat derived
from subsurface oxidation and
bituminous shales from Greenland
into which a dyke had intruded
(SPIRO & AIZENSHTAT, 1981;
SPIRO, 1984). In both instances the
kerogen had been exposed to higher
temperatures for relatively short
periods of time and samples of the
same kerogen at different distances
from the thermal events could be
studied. Spiro detected some effect
of the minerals on the nature of the
organic matter, but noted that the
trends were frequently contrasting,
because catalysis could only take
TABLE 1
Comparison of bituminous fractions associated with carbonates and silicates in oil shales
(data from SPIRO, 1980, and JEONG & KOBYLINSKI, 1983). S =silicates; C =carbonates
Selected features
Colorado
Oil shale
Israel
I
I'
I
I
I
Amount of bitumen S>C Depends on sample, mostly S > C
Polar substances S>C S>C
C=O S>C Erratic
C = C (Aliphatic)
C-H
C>S
S>C
Aromatics S=C S>C

Do Clay Minerals Act as Catalysts in the Thermal ... 7
place when the mineral surfa~es were
available for adsorption.
Laboratory simulation experiments
of the thermal decomposition of
kerogen
Experiments in closed systems
Very few such experiments have
been reported. MITTERER & HOER­
ING (1966) found that the nC15-C31
HC's obtained from some Recent
sediments and from the corresponding
kerogens on heating in sealed
tubes were qualitatively and quantitatively
similar. The authors imply
that these results supplement earlier
ones (HOERING & ABELSON, 1962)
which showed that the presence of
the rock matrix did not affect the distribution
of light HC's from a wide
range of sediments. It should be
noted, however, that the earlier experiments
were performed under entirely
different experimental conditions,
with a Toeppler pump removing
the volatile products from the
reactants.
Experiments, in open systems
Many more experiments were carried
out in open systems ( « blilk
flow»), primarily for the practical
purpose of assessing the oil potential
of source rocks. In recent years instruments
of the Rock Eval type
(ESPITALIE et al., 1977) have been
widely used. For routine work with
these instruments It IS very important
to establish whether. the mineral
matrix affects the course of pyrolysis.
In early experiments (GIRAUD, 1970;
SOURON et al., 1975) no differences
were detected, but more recent studies
have shown that in the presence
of the rock matrix the total yield of
HC's was reduced and the proportion
of light He's was increased relative to
the heavier ones (CLA YPOOL &
REED, 1976; MONIN et al., 1979;
ESPITALIE et al., 1980; ORR, 1981;
DAVIS & STANLEY, 1982; DEMBIC­
KI et al., 1983; KATZ, 1983). This
was attributed to two effects: retention
of HC's by the mineral matrix,
particularly by clays, .and subsequent
cracking to. produce lower
HC's. Retention of some of the products
by the mineral matrix has been
established beyond doubt. It is greater
for types II and Ill kerogens (i.e.
kerogens with more oxygen containing
functional groups) than for Type
·I and decreases with increasing maturity
(decreasing oxygen content)
and increasing concentration of the
kerogen. Catalysis by indigenous minerals
seems to be less firmly established:
either only relative amounts of
the HC's were determined (e.g. HORS­
FIELD & DOUGLAS, 1980) or it was
found that the total yield was decreased
by the mineral matrix (ESPI­
TALIE et al., 1980). An increase in the
relative amount of light HC's may be
primarily due to preferential retention
of the heavier ones. It seems possible
that most catalytic sites of indigenous
minerals may have been deac- .
tivated in the course of catagenesis.

1 _ prod:t~:c:~s
8 L. Heller-Kallai
In contrast, when minerals were
mixed with kerogen or added to whole
rock samples, or when the thermal
decomposition products were percolated
through plugs of various minerals,catalyticeffectswereclearlydemonstrated,
in addition to retention.
ESPITALIE et al. (1980; 1984) showed
that the absolute yield of light HC's
increased in the presence of montmorillonite
and, to a lesser degree, with(
illite and kaolinite. Similar results
with montmorillonite were obtained
by HETENYI (1983). Retention by
clay minerals depended on the surface
area; of the minerals examined
palygorskite retained the volatile
__ .!ll

Do Clay Minerals Act as Catalysts in the Thermal ... 9
tions. Simultaneously some calcite
reacted with organically derived
sulphur to give anhydrite, whether
due to elevated temperatures only or
in part also to attack of calcite by
, acid gases is uncertain.
Other reactions which may occur
on pyrolysis of organic matter and
that do not seem to have received
much attention are oxidationreduction
reactions involving the mineral
matrix. KONCZ (1979) suggested
that the ratio of residual carbon
after pyrolysis to total organic carbon
may be reduced by metal oxides
of different valency present in clay
minerals, which promote formation
of carbon monoxide at elevated temperatures.
These examples show that in laboratory
experiments minerals,- can participate
in reactions with organic
matter or undergo other changes
which may affect the products obtained
from kerogen pyrolysis.
Whether such changes actually occur
in natural systems remains to be
established.
Burial causes diagenetic changes
in clay mineral~. It has been postulated
that, in addition to supplying water
for transporting organic matter,
diagenetic changes of clays. may increase
their' catalytic activity, but
this, too, requires· substantiation
(FRIPIAT & CRUZ-CUMPLIDO, 1974).
Simulation experiments with model
organic compounds
In general the object of such experiments
was to demonstrate that various
organic compounds, which may
be regarded as petroleum precursors
or thermal decomposition products
of kerogen, can be transformed into
petroleum HC's with the aid of min"
eral catalysts. The results obtained in
other experiments, not specially d~signed
for this purpose, were also u­
tilised. Various minerals have been >
employed together with model compounds
ranging from very complex
molecules like marine algae (EVANS
& FELBECK, 1983) to simpler molecules
with functional groups, e.g.
alcohols (GALWEY, 1970; 1972) to
long-chain HC's (TARAFA et al., 1983;
DEMBICKI et al., 1983; GOLD­
STEIN, 1983) and terpenes (FREN­
KEL & HELLER-KALLAI, 1977). Fate
ty acids are probably the most extensively
studied model compounds
(JOHNS, 1979; HELLER-KALLAI et
al., 1984 and references therein). It is
well established that clay minerals
" can retain organic matter and catalyse
a wide range of chemical reactions,
some of which may lead to petroleum
constituents, b~t the distribution
patterns obtained generally
- differ from those of natural oils. One
possible cause is the choice of the reagents,
another that of the experimental
conditions. It has been shown that
the HC's obtained from stearic acid
heated in the presence of cla:ys in
open and closed systems are very different:
in open systems saturated and
unsaturated cracking products were
obtained, with little skeletal isomerization;
in sealed tubes branched
chain hydrocarbons were formed and
unsaturated hydrocarbons were less

10 L. Heller-Kallai
abundant (WILSON & GALWEY,
1976; HELLER-KALLAI et al., 1984).
The purpose of the following sections
is to illustrate how experimental conditions
can affect the stability and
thermal decomposition reactions of
long-chain fatty acids in the presence
of clay minerals. The products obtained
will not be discussed in detail.
Experiments with fatty acids
Reactions in closed systems - Reactions
of fatty acids with clay minerals
in closed systems were reviewed by
JOHNS (1979), who concluded that
. ------~------- the formation of alkanes from fatty
acids proceeds in two stages: decarboxylation
catalysed by one type of
active· sites followed by cracking,
which is catalysed by other sites activated
at higher temperatures. The
extent of the decarboxylation was
inferred from the amount of fatty
acid consumed.
Reactions in open systems- In reactions·
carried-out under ,-bulk flow»
conditions the amount of C0 2 produced
by decarboxylation could be
directly determined. Three different
effects of clay minerals were distinguished:
decarboxylation, cracking
and retention (HELLER-KALLAI et
al., 1984). These may operate sim~ltaneously
but depend on different
properties of the clays.
-Decarboxylation and cracking-,
The data summarised in Table 2
show that trioctahedral minerals
cause more decarboxylation than the
corresponding dioctahedral ones. Catalytic
cracking is due to entirely different
features. Thus conversion of
montmorillonite into H+ montmorillonite
greatly increased its activity as
a cracking catalyst, but did not affect
the decarboxylation reaction.
- Retention- This depends on various
factors. Palygorskite and sepiolite,
which sorb fatty acids in the
structural channels (YARIV &
TABLE 2
Decarboxylation and cracking of stearic acid (data from HELLER-KALLAI et al., 1984)
Mineral
Pyrophy lli te
Talc
Kaolinite
Lizardite
Palygorskite
Sepiolite
Montmorillonite
H Montmorillonite ·
Nontronite
Saponite
Laponite
Decarboxylation
(% of maximum possible)
0
13.2
0
7.8
8.1
11.6
4.0
1.5
0.5
23.0
14.4
Cracking
w
s
VS

Do Clay Minerals Act as Catalysts in the Thermal ... 11
. HELLER-KALLAI, 1984) retained
them most effectively without causing
cracking, in agreement with the
results obtained by ESPIT ALIE et al.
(1984) with pyrolysis products of kerogen.
By adsorbing the acids, clay
minerals retain them in the pyroprobe,
thereby exposing them to a more
prolonged thermal treatment. The
delicate balance between stabilisa-.
tion of the acid by adsorption and the
enhanced thermal and catalytic decomposition
reactions is determined
by the nature of the clay mineral, the
chain length of the acid and the experimental
conditions (AIZENSHTAT et
al., 1984). In open systems the choice
of the homologue of . the acid for
model experiments is therefore expected
to be much more critical than
for experiments in closed 1)ystems.
Reactions in confined systems -
Thermal changes of fatty acids in
the presence of various clay minerals
were studied in alkali halide disks.
'These simulate a semi-closed environment
from which volatile products
are gradually lost. Under these conditions
the adsorption complexes
formed and the changes occurring
on heating could be studied by IR
spectroscopy, Some of the results
relevant to the present discussion will
be briefly s~mmarized.
In the confined space of alkali halide
disks the organic matter was 'retained
to higher temperatures than in
open systems. Carboxylic acids are
adsorbed on clays in the acid ·form,
but can be partially converted into
the ionic form, which is generally
more firmly retained. This was
brought about by grinding alkali haljde
disks of stearic acid associations
with any of the clays listed in Table 2.
With some minerals the ionic form
was also obtained on heating the carboxylic
acid-clay associations. In
open systems most or all of the organic
material was lost before the ions
could form. In alkali halide disks the
ionic form developed with some minerals
at elevated temperatures without
previous grinding, but not with
others e.g. with talc but not with pyrophyllite.
Accordingly, under the
conditions of the experiments, talc retained
organic matter more tenaciously
than pyrophyllite (Fig. 2) (HEL­
LER-KALLAI et al., 1986). In general
the ionic form was obtained more
readily in the presence of trioctahedral
than with the corresponding
dioctahedral minerals due to the
more basic nature of their edge surfaces.
These results illustrate how the experimental
conditions can affect the
conversion of carboxylic acid into
carboxylate ions, thereby changing
the amount retained under a particular
thermal regime. Whether decomposition
of the acidic and ionic forms
follows different reaction paths remains
to be determined. It is also unclear
whether the same property of
the clay minerals causes conversion
to the ionic form and decarboxylation,
both of which occur more readily
with trioctahedral than with dioctahedral
minerals.
Organo-montmorilloni te (beritone)
retained more stearic acid in alkali
halide disks than other montmoril-

L. H eller-Kallai
-CH -
1
-COOH
-COO-
)-__l
-CH -
~2
A
-coo-
-cooH +
J------
2
2900 1700 1600
Talc
2900
Pyrophyll ite
1700 1600
Fig. 2 - Selected features of FTIR spectra of stearic acid with talc or pyrophyllit'e in KBr disks
heated at 250°C (After HELLER-KALLAI et al., 1986). (Note conversion of acidic to ionic form
without loss of organic matter with talc in contrast to pyrophyllite, where no conversion occurred
and organic matter was steadily lost).

Do Clay Minerals _Act as Catalysts iiitlie Thermal ... 13
lonites, but, in contrast, carboxylate
ions were not formed, even on repeated
grinding of the disks (unpublished).
Oxidation-reduction reactions- Reduction
of structural iron of clay minerals
on heating with stearic acid
depends on the experimental conditions.
Mossbauer spectra showeq that ~
with nontronite and montmoi-illonite
Fe 3 + was partially reduced in
closed systems but not under «bulk
flow» conditions. In alkali halide
disks montmorillonite was reduced
but nontronite was not (unpublished).
Thes.e results demonstrate that
oxidation-reduction reactions involving
the mineral matrix depend on
the clay mineral and on the experimental
conditions: in sealed ampoules
in a nitrogen atmosphrre, and
in alkali halide disks which werebeat-
ed in air, some reduction occurred,
but on heating in an open system urider
inert conditions structural iron
was not reduced. It appears that reduction
of structural iron is a secondary
reaction between the clay and
the pyroproducts.
Conclusions
An attempt to integrate the
observations on natural systems with
the results obtained in laboratory experiments
with kerogen leads to the,
following, very tentative concepts regarding
the possible effect of clay
minerals on the decomposition reaction
of the organic material.
The first stage of the reaction is
'
partial fragmentation of kerogen due
to thermal effects. Clay minerals can
r-retain some of the products and cause
cracking. It seems that with indigenous
clays retention is more important
than cracking, due to partial or
complete poi~oning of the catalytic
sites by. preferentially adsorbed species.
Retention ofHC-like compounds
by indigenous clays may be envisaged
as adsorption by organo-clays,
- which do not act as cracking
catalysts. On migration of the organic
matter, or in response to mechanical
action, which exposes fresh
mineral surfaces (REED & OERTEL,
1978.) catalytic effects may become
more important. The HC's may be
generated in open or in closed pores
containing different amounts of wa- .
ter.
If these concepts are correct, they
lead to the conclusion that no single
set of experimental conditions can
simulate the complex pr-ocess of
formation of petroleum hydrocarbons.
The combined products from
several experiments may more closely
resemble the distribution observed
in natural samples, e.g. experiments
in open, semi-closed ·and closed systems
may emulate reactions in open
and closed pores or reactions before
and after expulsion, and experiments
with organo-clays and with variously
ground clay minerals may model
adsorption by indigenous clays and
freshly exposed clay surfaces. The-experiments
with fatty acids showed
how some of these variables affect the
model systems. Because retention,
decarboxylation and crac~ing de-

14 L. Heller-Kallai
pend on different features of the
minerals, the products obtained with
mixtures of clays are expected to differ
from the sum of those obtained in
separate reactions- one clay may retain
the organic material facilitating
decarboxylation or cracking caused
by another.
Various combinations of reagents
and experimental conditions may
lead to improved simulation,
although many variables will necessarily
be neglected and the basic
problems of substituting
temp~ratuJ:e~ .. focg~ological
of time will always persist.
Acknowledgements
higher
periods
I wish to thank Prof. Z. Aizenshtat
and Dr. Y. Nathan for helpful discussion,
Dr. B. Carlson for critical reading
of the manuscript and Dr. B.
Spiro and Dr. J. Trichet for preprints
of their papers.
REFERENCES
AIZENSHTAT Z., MILOSLAVSKI I., HELLER-KALLAI L., 1984. The effect of montmorillonite on the thermal
----------------tlecompositiorioffiilfYaC:las unaer ~

Do Clay Minerals Act as Catalysts tnthe Thermal ... 15
GIRAUD A., 1970. Application of pyrolysis and gas chromatography to geochemical characterization of
kerogen in sedimentary rocks. Buil. AAPG 54, 439-455.
GoLDSTEIN T.P., 1983. Geocatalytic reactions in formation and maturation of petroleum. Bull. AAPG
67, 152-159. .
HELLER-K.ALLAI L., AIZENSHTAT Z., MILOSLAVSKI !., 1984. The effect of various clay minerals on the
thermal decomposition of stearic acid under «bulk flow» conditions. Clay Minerals 19, 779-788.
HELLER-K.ALLAI L., ESTERSON G., AIZENSHTAT Z., PISMEN M., 1984. Mineral reactions of Israeli oil shale.
J. Applied Pyrolysis 6, 375-389.
HELLER-KALLAI L., YARIV S., FRIEDMAN 1., 1986. Thermal analysis of the interaction between stearic
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HETENYI M., 1983. Experimental evolution of oil shales and kerogens isolated from them. Acta Miner.
Petrogr. Szeged XXVI/I, 73-85.
HoERING T.C., ABELSON P.H., 1962. Hydrocarbons from kerogen. Carnegie Inst. of Washington Year
Book 1962, 229-234.
HoRSFIELD B., DouGLAS A.G ., 1980. The influence of minerals on the pyrolysis of kerogens. Geochim.
Cosmochim.Acta44, 1119-1131.
HuRST A., 1982. The clay mineralogy of Jurassic shales from Bora, N.E. Scotland. Pp. 677-684, in:
Proc. Int. Clay Conf. 1981, Bologna and Pavia (H. van Olphen and F. Veniale, editors), Developments
in Sedimentology 35.
IvANOV V .V., SHCHERBAR 0 .V., 1983. Mineral matrix influence on the dynamics and products of organic
matter catagenetic transformation. Org. Geochem. 4, 185-194.
JEoNG K.M., KoBYLINSKI T.P., 1983. Organic-mineral matter interactions in Green River oil shale.
Amer. Chem. Soc. Symposium 230, 493-512.
JEONG K.M., PA~ZER J .F. II, 1983. Indigenous mineral matter effects in pyrolysis of Green River oil
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JoHNS W .D., 1979. Clay mineral catalysis and petroleum generation. Ann. Rev. Earth and Planet. Sci.
7, 1983-1998.
JoHNS W.D., 1982. The role of the clay minerals matrix in petroleum generation during burial diagenesis.
Pp. 655-664, in: Proc. Int. Clay. Conf. 1981, Bologna and Pavia (H. van Olphen and F.
Veniale, editors), Developments in Sedimentology 35.
JoNES R.W., 1984. Comparison of carbonate and shale source rocks. (Abstract). Bull. AAPG 68,494.
K.ATZ B.J., 1983. Limitations of Rock-Eval pyrolysis for typing organic matter. Org. Geochem. 4,
19~1~. '
KoNcz 1., 1979. Examination of factors affecting the results of high temperature pyrolysis studies used
to characterize non-soluble disperse organic material in sedimentary rocks. Critical evaluation of
Gransch and Eisma~s method. Acta Miner. Petrogr. Szeged 24/1, 125-136.
MITTERER R.M., HOERING T.C., 1966. Production of hydrocarbons from the organic matter in a recent
sediment. Carnegie Institute Year Book 1966, 510-514.
MONIN J.C., DURAND B., VANDERBROUKE M., Hue A.Y., 1979. Experimental simulation of the natural
transformation of kerogen. Pp. 517-530, in: Advances in Organic Geochemistry (A.G. Douglas
and J.R. Maxwell, editors), Pergamon Press.
ORR W .L., 1981. Comments on pyrolytic hydrocarbon yields in source rock evaluation. Pp. 775-787, in:
Advances in Organic Geochemistry (M. Bjon!ly, editor), J. Wiley & Sons.
PEARSON M.J., WATKINS D., SMALL J.S., 1982. Clay diagenesis and organic maturation in Northern
North Sea sediments. Pp. 665-675, in: Proc. Int. Clay Conf. 1981, Bologna and Pavia (H. van
Olphen and F. Veniale, editors). Developments in Sedimentology 35.
REED W.E., 0ERTEL G., 1978. Is compaction a factor in organic diagenesis? Geo!. Soc. Am. Bull. 89,
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stages of prirrzary migration. Org. Geochem. 5, 65-73.
SouRoN C., BouLET R., EsPITALIE J., 1975. Etude par spectrometrie de masse de la decomposition
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(R. Gompes and J. Gen, editors).
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Hartrurim, Israel. Pp. 799-807, in: Advances in Organic Geochemistry (M. Bjor0y, editor), J.
Wiley & Sons.
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Schenck, J.W. De Leenw and J.W.M. Lijmbach, editors), Pergamon Press.
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16 L. H eller-Kallai
TrssoT B.P., WELTE D.H., 1978. Petroleum Formation and Occurrence. p. 293, Springer-Verlag, Berlin,
Heidelberg, New York.
WrLLIAMS P .F.V., DouGLAS A.G ., 1981. The effectoflithologic variation on organic geochemistry in the
Kimmeridge clay of Britain. Pp. 568-575, in: Advances in Organic Geochemistry (M. Bjor0y,
editor), J. Wiley & Sons. ,
WrLSON M.C., GALWEY A.K., 1976. Reactions of stearic acid, of dodecanol and of cyclohexanol on the
clay minerals illite, kaolinite and montmorillonite. J. Chim. Phys. 73 (4), 441-446.
YARIV S., HELLER-KALLAI L., 1984. Thermal treatment of sepiolite and palygorskite stearic acid associations.
Chem. Geol. 45, 313-327.

Miner. Petrogr. Acta
Vol. 29-A, pp. 17-33 (1985)
The Process of Bentonite Formation in
Cabo de Gata, Almeria, Spain
JOSE LINARES
Estaci6n Experimental del Zaidin; C.S.I.C., Profesor Albareda 1, 18008 Granada, Espaii.a
I am especially honoured to have this opportunity to pay homage to the memory of a man who was
not only a respected teacher but also a very dear friend, Professor J. L. Martin·Vivaldi, to :whose
-memory my lecture and this Congress are dedicated. .
I wish also to express my affection for Professor A. Pozzuoli, Chairman of the Congress and to thank
him and the Organizing Committee of the First Italian-Spanish Congress on Clays and Clay Minerals
for inviting me to present this Invited Lecture.
AB.STRACT- A genetic model for hydrothermal bentonites must include data
on the origin and nature of alteration solutions, ·physical system of solution
transport, aptitude of parent materials, temperature and pressure effects, the
whole frame of mineral-solution equilibria, reaction ti_me, etc.
Numerous mineralogical and geochemical results collected, over a long
period of time, from the volcanic region of Cabo de Gata now allow some
hypotheses to, be made regarding the pFocess that has given rise to the bentonite
deposits.
The region is a p'art of the volcanic complex of the SE of Spain, with a s.s.
calcalkaline volcanism, aged from 17 to 8 my. Several volcanic cycles can be
distinguished, characterized by the series: pyroclastics, agglomeratesconglomerates
and la vas. In some places two types of hydrothermal alterations
are recognized: one, with kaolinite, alunite and jarosite as principal
alteration minerals, and the other, whose characteristic mineral is a smectite.
Only in this case, the alteration produces big deposits of economic value.
The bentonitic alteration involves cinerites, ignimbrites, agglomerates and
conglomerates. All the alteration zones are associated with fractures, normally
with directions close to NE-SW. Field evidence suggests .that the
bentonites have not undergone any type of transport. or remanagement after
their formation, thus, the transformation rock-to-bentonite must be considered
to have taken place in situ.
The colour of the bentonites (due to trace elements) is variable: white, green,
blue, red and black, with all the intermediate colours. The main mineralogical
component is always a smectite accompanied by smaller quantities of
plagioclase, quartz, K-feldspar, disordered tridymite, amphiboles and
mordenite. The smectites can be ascribed to the ri:J.onfmorillonite-beidellitenontroniteseries.
Some variability in chemical compositfon, tetrahedral and
total charge is observed even within a particular deposit. The magnesium
content of smectites is.,always higher than that of the parent rock.
The bentonite formation process consists of the hydrolysis (hydrogen metasomatism)
of porous volCanic materials by solutions of meteoric origin with
temperatures close to 50°C, as shown by oxygen and hydrogen isotope
geochemistry, It is suggested that the main solution is a sodium-chloride
type, as deduced from the relationship between extractable anions and cations.
The enrichment in solutes must be a result of wall-rock alteration. The
magnesium content must proceed from the metamorphic basement of the

18 J. Linares
volcanic complex. In the process,-the VolCanic materials, essentially vitreous,
are transformed to bentonite, while silica and alkalines are removed in solution.
In some cases the losses of matter and volume are high.
The results of hydrothermal synthesis of smectites, although contradictory in
some cases, are useful to conlude that with increasing temperature of formation,
the range of chemical composition is restricted and the tetrahedral
charge also is increased. The pressure effect on the equilibrium is complex.
The presence of mordenite and disordered tridymite helps, to complete the
picture of the genetic process of bentonite.
Application of the phase rule to the process indicates that the presence of
great numbers of mobile components reduces the amount of phases, in such a
way that in some cases the product of the reaction is monomineralic. ·
The thermodynamics of irreversible processes allow the time needed for the
formation of a bentonite deposit to be calculated. Calculated times range
over a million of years for the biggest deposit of the region.
Finally, a physical model is suggested for the geothermal alteration system,
and a (P, T) tentative phase equilibrium diagram for 2:1 phyllosilicates is
proposed.
I
I
The bentonites of Cabo de Gata
The r~gion of Cabo de Gata is a part
of the volcanic complex located in the
southeastern corner of the Iberian
peninsula (Fig. 1) (ARANA & VEGAS,
1974). Here, the most extended type
of volcanism is calcalkaline, with
an age ranging from 17 to 8 million
years (BELLON & BROUSE, 1977;
LOPEZ & RODRIGUEZ, 1980). The
volcanic events have been cyclic and
are occasionally separated by fossiliferous
episodes (FUSTER et al.,
1965; COELLO & CASTANON, 1965;
PAEZ & SANCHEZ, 1965; SAN­
CHEZ, 1968; MELENDEZ et al.,
1964; ESTEBAN & GINER, 1980).
There is no evidence of recent
magmatic activity or important
geothermal anomalies.
Two definite geographical units
can be considered in the region: a)
The «Serrata de Nijar», located, at
the west and b) the «Sierra de Gata>>
that lies parallel to the coast. In both
areas there are zones of hydrothermal
alteration (LINARES, 1963; LI-
NARES et al., 1972). " Two types of alterations
can be distinguished: the
first one is acidic, with formation of
kaolinite, alunite and jarosite as alteration
products. The other i~ nearly
neutral, and has lead to the formation
of thick bentonite deposits.
Associated with these alteration 1 -
zones are the auriferous complexes of
Rodalquilar and some sulphide deposits.
This paper deals' only with the alterations
which gave rise to bentonite
formation.
The oldest and most alkaline rocks
of the region occur in the «Serrata de

The Process of Bentonite Formation ...
•
1
19
Zone 3
"'
Murcia
•
I
I.
/
I
I
I
I
I
/
/
I Vera
I e:
Z o n e 1
Zoo• Z {:::=
Zone 3
Q
C 1 llliiii!Ill]
Calcalkaline Volcanism
Potassic Volcanism
Basaltic Volcanism
Cabo de Gata
0
20 40
60 km
Fig. 1 -Volcanic complex of SE Spain (ARANA & VEGAS, 1974).
Nijar». Volcanism is related to faults • blue and occasionally white. The collying
in the direction N60E (MAR- , our hues are due to. the presence of
TINEZ, 1972). The bentonite deposits Mn, Fe 2 +, Cr, Cu, etc. (LINARES et al.,
are associated to amphibolic dacite 1973). Some deposits occur as diamaterials
and to vitrophyric tuffs pires, intruding through massive '
(CABALLERO, 1982). The bentonite rocks, or forming deposits differing a
colours are bright: red, green, black, great deal in size. In this zone, smec-

20 J. Linares
I'
I
tites are richer in Fe and Mg than is very high, smectites tending to
those from «Sierra de Gata» (CABAL- nonti"onite, --~-~~~--~--~·
LERO, 1982).
In several previous papers of the
In the «Sierra de Gata» the altered forementioned authors some ideas
materials were ignimbrites, tuffs, about the plausible process of bentonconglomerates
and volcanic ite formation have been suggested,
agglomerates. The alterations took mainly on the basis of the result of
place in situ, as in the«Serrata de HEMLEY et al. (1961). According to
Nijar», although occasionally there is these authors, an hydrothermal soluevidence
of some transport (AUGUS- tion, with a rather restricted corn-·
TIN, 1974). Most deposits are related position, can alter plagioclase, a chief
to NE-SW fracture and are very big component of volcanic material
in size. Bentonites show very pale (TRICHET, 1969), to montmorilloncolours,
ranging from green to yel- ite, at temperatures going from 325
low, but with predominance of white octo room temperature. As a matter
(REYES et al., 1980a,b). A type de- of fact, the absence of paragonite jus-
, posit is that occurring at «Morr6n de tifies the upper temperature limit.
______________ M~~o>~, P!"Odl.lc:ec.l_ by_ (llteration of The presence of zeolite of the
andesitic-pyroxenic tuffs. In other mordenite-clinoptilolite type, occurcases,
for instance at «Los Trancos», ring occasionally in bentonites, indibentonites
derive from amphibolic cates a lower temperature limit,
dacite agglomerates and tuffs. In this which must be close to the surface
case the smectites are of the beidel- temperatllre.
lite type.
Quite recently, it has been possible
to make more pretise statements on
The mineralogy of all these bentonthe
formation of bentonites, as well
ites is very simple. They consist
as on .the origins of hydrothermal
largely of smectite, accompanied by
solutions, on the basis of studies of
minor quantities of plagioclase,
light stable isotopes (LEONE et al.,
quartz, amphibole, biotite, K-
1983). Actually, it was shown that
fe_ldspar, zeolite and low temperature 1
isotopic data are in agreement with a
tridymite. The last three minerals are
formation temperature of about 70 oc
considered to be related to the profor

ta de Nijar» and at the southern zone.
These are the most important facts
known up to the present time, stated
in a very simplified way.
What follows will deal with some
comparative and even speculative
aspects, which may contribute to a
better understanding of the formation
process of bentonites and of the
environmental conditions of the hydrothermal
system.
Smectite synthesis
The first point to be known is the
data reported about smectite synthesis
in the laboratory.
A review of the literature confirms
a well knownfact: the difficulty of interpreting
results which are very
often contradictory.
'-
The synthesis experiments sometimes
do not allow equilibrium to be
reached either between the mineral
to be attacked and the solution or between
the components of a mixture.
The diversity of materials, grain size
distribution, experimental devices
used, and the rather short reaction
times employed, are the the reasons
why the results obtained are often
found lacking in coherence.
It has been possible to demonstrate
that reaction times as long as at least
a month are needed to achieve a cer'­
tain reliability in the relationships '
between phases and to obtain sufficient
material, so that satisfactory
crystallochemical identifications can
be made (VELDE, 1977).
By selecting the data that meet
The Process of Bentonite Formation ... 21
these specifications, some general
conclusions can be drawn. For instance,
ROY & ROY (1955) and SAND
et al. (1957) have shown that for the
system Si-Mg-Al-HzO, the field of
chemical composition of smectites
becomes smaller as temperature increases.
In our case we are dealing
with temperatures below 100 oc and,
consequently, the variability in chemical
composition of the smectites is
very great.
Other authors (VELDE, 1977, review)
have shown that potassium
dioctahedral smectites are more unstable
(250 oc as upper temperature
limit) than the Na and Ca ones (400
°C), and also that Mg-Fe-Al smectites
may form even at temperatures close
to room temperature.
A not yet well established fact is
that as temperatures increase, synthetic
smectite exhibits a higher
tetrahedral charge. This could be the
case for our zone in the «Los Trancos»
deposit mentioned above, where
the formation temperature is somewhat
higher than in the rest of the
deposits. However, other deposits of
similar formation temperatures show
a zero tetrahedral charge. Therefore,
other factors must also influence the
tetrahedral substitution, among
them, probably, the Al content and
the pH of the hydrothermal solution.
The influence of pressure upon
equilibria has been studied by several
authors (ROY & ROY, 1955; SAND
.et al., 1957; HEMLEY, 1959). It was
found in all cases that changes in
pressure, ranging from 100 to 2000
atm do not shift the equilibrium

22 J. Linares
temperatures by more than 30 °C:
Therefore, in this case, the effect of
pressure must be disregarded.
Briefly, the experimental synthesis
provides data supporting a stability
field for smectite always below 350
°C. If solutions contain potassium,
smecti tes are transformed to illi te/
montmorilloni te interstra tifica tions
and, finally, to illite, even at temperatures
under 200 °C, as will be seen
later. Besides, it is also patent that
further experimental work on smectite
synthesis must be carried out in
order to make clear the existent relationship
between formation temperatures
and composition of smectites.
A particular field of smectite
synthesis~is that~carried out strictly
from solutions at room temperature.
In this respect, we have contributed
with some results than can be very
illustrative (REYES et al., 1982a,b).
Shown in Fig." 2 are the compositions
of synthetic precipitates, as a
function of the composition of the
starting solutions, for several equilibrium
pH values. It can be observed
that smectite forms at any given pH,
and that a fixed smectite composition
may be req.ched at several pH values,
by only varying the composition of
the original solution.
These results evidence the vast
100
10
(!)
....,
....,
"'
·:;_
u
(!)
S-
a.
:;:
'-
::;;: "'
10
100
/
/
/
/
Mg/Al
starting solution
100 10
10 1 ()0
Fig. 2 - Compositional relations between starting solutions and precipitates. A = Beidellite -
Montmorillonite; B = Palygorskite; C = Talc; D = Saponite; E = Sepiolite.

possibilities in smectite compositions
and the great diversity of their formation
conditions.
Taking into account all the available
data on experimental synthesis,
as well as the observations under
natural conditions, the following parameters
governing the existence and
composition of smectite can be
enumerated:
1) nature and texture of parent rocks;
2) composition of mineralizing solution;
3) temperature during the formation
process;
4) presence or absence of Mg (HAR­
DER, 1972);
5) alteration degree of parent material.
Presence of disordered tridymite,
Other factors to be considered are
the conditions of formation of minerals
paragenetic with smectites. In
our case, we have, for instance, K­
feldspar, zeolites and disordered
tridymite. I will only refer to tridymite,
since the conditions of formation
of zeolites and K-feldspar at low
temperatures are well known.
The presence of disordered cristobalite
in behtonites has been reported
many times (GRIM &
GUVEN, 1978). As a matter of fact).
this component should be referred to
as u-tridymite, according to results of
WILSON et al. (1974). The crystalline
structure of this material may be described
as a turbostratic stacking,
with a random transversal shifting
The Process of Bentonite Foiiiiiiiion ... 23
normal to the axis. RENDER­
SON et al. (1971) were first to demonstrate,
from isotopic studies on oxygen,
that the formation temperature
of tridymites found in bentonites,
was close to 25 °C, and that tridymite
was singenetic with bentonite. This
fact has been corroborated later by
many authors. It can be stated, therefore,
that tridymite is not a primary
mineral, but an alteration mineral,
associated with bentonites.
MIZUTANI (1966) studied the diagenetic
evolution of these disordered
tridymites from a kinetic
point of view, and concluded that it is
a low temperature mineral, evolving
into guartz with time.
In our case, rto data are available
on isotopic fractionation of oxygen in
tridymites, but without doubt, their ·
formation temperature should be
similar to that of bentonites. On the
other hand, the formation of tridymite
is an almost necessary fact,
since during the bentonite formation,
important quantities of silica are released,
as will be seen later. Although
the solubility of this polymorph variety
of silica is high, its precipitation
may be triggered by temperature
changes taking place near the ground
surface (FOURNIER & ROWE, 1977;
CARR & FYFE, 1958).
The origin of solutions
It has been already mentioned,
that in the region studied, the solutions
contributing to the formation of
smectite were of meteoric origin. As

24 J. Linares
will be seen in another communica- caused by differences in hydrostatic
tion in· this Congress, the meteoric _.. head, litlw~tatic. pressures, osmotic
water should derive from aquifers pressure (membrane effects in shales,
recharged in metamorphic forma- etc.),_ density gradients and intrusion
tions located to the north of the zone . of magmatic or meteoric solutions.
· («Sierra Alamilla» and «Sierra Ca- In our case, the cinerite beds
brera>>) (CABALLERO, 1985). When should provide an excellent porous
meteoric water percolates through medium for the easy transport of
the rocks a light enrichment in so- solutions·. As will be discussed later,
lutes takes place, due to hydrolysis the meteoric water should come by
and extraction of soluble salts (CAR- gravity forces through fractures,
ROL, 1970; LOUGHNAN, 1969). Dur- down to volcanic cinerites. The soluing
the transport of solutions to deep tions, once heated, would alter this
levels, the temperature rises and the material during the process of infilconcentration
of solutes increases. tration, with a new enrichment in
From isotopic data, the possibility solutes (KHITAROV, 1957; TOVARof
contamination from magmatic OVA, 1958).
solutions cannot be excluded, Given the previously mentioned
·~-·--~-----a:IthouglnlriscontfibU.fion should be temperatures (40 oc and 70 °C) the
no greater than about 5%.
solution does not have to reach to
In order that these solutions be great depths in order to become heatable
to act, they should be brought to ed. Consequently, cinerite should
an appropriate temperature by some occur at shallow depths. Field
transport mechanism through ciner- obser~ations clearly indicate that the
ite beds.
maximum depth of emplacement of
pyroclastic material does not exceed
100 m in any case. Under these conditions,
Transport of solutions
the pressure of solutions
were subjected to, should not be over
a few tens of atmospheres. These data
are in agreement with those obtained
for other mineral deposits of hydrothermal
origin, which were subjected
to pressure under 1 Kb (SKIN­
NER, 1979).
Several conditions are recognized
as necessary for the existence of an
hydrothermal alteration process:
· a) a geological structure allowing the
flow of water at deep levels;
b) a slow flow of the solution and a
large contact area between solution
and rock;
c) a returning path towards the surface
through faults, fractures or
permeable strata.
On the other hand, the driving
force moving the solutions may be
Thermal characteristics of the process
For the existence of an hydrothermal
system, some type of geothermal
anomaly must be present. The ther-

mal energy of the earth's crust may.
be derived from any of the following
processes:
a) magma emplacement from subcrusta!
zones;
b) radioactive decay of 4 °K, 238 U and
232Th;
c) removal of stresses along faulted
zones;
d) exothermic reactions between
solutions and minerals.
In this case, none of the first three
processes needs to be invoked. Sim-
, ply, the existence of deep fractures,
together with a normal geothermal
gradient, would suffice for the heating
of meteoric water. However, the
'influence of a cooling magmatic
chamber is not to be discarded, since
some evidence exists, that the hydrothermal
alterations took place not
later than the regional volcani~m.
It has been feasible to calculate
(NORTON & CAl'HLES, 1979) the
temperature changes taking place
around an igneous intrusive body.
For a pluton, 2.55 km under the
ground surface with . an initial
temperature of 750 °C, the thermal
anomalies have been calculated as a
function of distance to the pluton, for
several cooling times. These calculations
have. shown that the thermal
halo lasts for extended periods of
time·, so that, for instance, 40000
years after the pluton emplacement,
temperatures at a depth of 700 m, ·
may be as high as 100 °C. This
temperature is fairly higher than that
corresponding to a normal geothermal
gradient.
The Process of Bentonite Form~tion ... 25
An energy source such as that described
above c0uld have heated the
solution which infiltra!ed through
fractures, caused by the pluton emplacement
or by subvolcanic rocks,
the latter being frequently found in
the Cabo de Gata region.
On the other hand, SCHOEN et al.
(1974) developed a model for hydrothermal
convection which is also
valid in our case. It can be briefly described
as a convection system originating
from the infiltration of
meteoric water along a thermal gradient
caused by a magmatic focus. I
want to stress that this focus is by no
means necessary, the presence of
deep cracks and of a normal geotherma1
gradient being sufficient. Water
penetrates deeply and its temperature
raises until a porous medium :
such as volcanic cinders, in our case
-is reached. The circulation of water
in this permeable zone proceeds
at constant pressure, and is accompanied
by a further increase in temperature.
If a fracture system is presentsuch
as the one with a NE-SW direction
existing in our zone - the solution
will begin to ascend. Eventually,
the heated fluid could pass to a
vapour phase and back again to a
liquid phase in zones where the adequate
pressure or fluid composition
is attained, but this process is not
necessary. Finally, the solution
reaches the surface, undergoing an
important drop in pressure and
temperature, and emerges as thermal
springs.
Whether such an intrusive body
existed or not in the zone of Cabo de
Gata is not clear on the basis of our

26 J. Linares
results. The only assertion that can
be made is that no contamination by
magmatic solutions is detected anywhere.
Now, I want to point out a subject
that has passed unnoticed by many
authors,namely, theadditionalenergy
input due to the reactions of hydrothermal
alteration.
According to NORTON & CATH­
LES (1979) the heat of hydrolysis
reactions may be caused by: a) irreversible
dissolution of primary minerals,
b) reversible precipitation and
dissolution heats of hydrothermal
minerals, c) association and dissociation
heats of aqueous complexes, and
d) heats of redox fractions between
~--~-~--- componentsin-soru-tion-.
In the hydrothermal system acting
at Cabo de Gata, the processes c) and
d) were, seemingly, of minor importance.
However, the heat of hydrolysis
of vitreous cinerites and that caused
by the precipitation of smectite must
be taken into a,ccount.
I have calculated the change in enthalpy
produced by the hydrolysis of
albite glass with the aid of thermodynamic
data reported by ROBIE &
WALDBAUM (1968). The results
obtained are -48.79 kcal per mol
of albite. Therefore, the reaction is
exothermic.
This is a very important fact, since
it implies that once started, the hydrolytic
reactions in a pyroclastic
bed, will continue spontaneously, releasing
energy and keeping or even
raising the temperature of the system.
In accordance with these data,
one cubic meter of cinerite, with
characteristics similar to those of the
Cabo~de,Cata region, will be enough
to increase in the temperature of 150
liters of solution 1 °C.
The calculated value for the hydrolytic
reaction of albite is in agreement
with others found by several
authors. Thus, HELGESON et al.
(1969) and HEMLEY (1959) calculated
an enthalpy of about several
tens of kcal per mol for other hydrolysis
reactions. As a general fact, it can
be stated that for silicate hydrolysis,
reaction enthalpies are in the order of
10 4 kcal per mol.
Account also must be taken of the
fact that hydrolysis enthalpies decrease
as temperature increases
(HELGESON et al., 1969). At low
temperatures, the mass ratio between
destroyed and neoformed
minerals is higher, and the high
values for the dissolution enthalpy
are. added to the total energy.
Therefore, the effect of hydrolysis
reactions on an hydrothermal system
will be that of enlargening the duration
of the thermal anomaly, specially
during low temperature stages.
This provides further supporting evidence
that an intrusive body is not
needed as an energy source in the
hydrothermal system working at
Cabo de Gata. A normal temperature
gradient, together with the hydrolysis
enthalpies were probably sufficient
to alter the pyroclastic beds to
bentonites.
Now, then, from a strictly thermodynamic
point of view, it is not sufficient
to know whether the reaction is
exothermic. More important is to

The Process of Bentonite Formation ...
27
know whether the change in free
energy is negative. In this way, not
only the enthalpy, but also the effects
due to enthropy will be taken into
account.
For the sake of simplification, the
type reaction for the system at Cabo
de Gata has been expressed as:
1.17 Sh OsAlNa + L04 H+ + 3.32 H20
~ 1.6ISi(OH)4 + Na+ + 0.5 Sb.67 Ah.33
Nao.33 010 (OHh
So, albite is hydrolyzed, with the
formation cif smectite and elimination
of sodium and silica in the solution.
First of all, the variation in free
energy under normal conditions was
calculated, and then recalculated as a
function of temperature (KERN &
WEISBROD, 1964; GARRELS &
CHRIST, 1965). To accomplish'-this,
the thermodynamic data derived by
ROBIE & WALBAUM (1968) and by
WEAST & ASTLE (1982) were used.
Thus, for the standard free energy of
reaction a value of -46.75 kcal was
obtained. The equation expressing
the variation of free energy with
temperature is as follows:
LlGP.T = -46750 + 1.39 (T - 298)
This result indicates that the
formation of smectite starting from
albite will be always spontaneous, at
practically any given temperature. ,
Hence, it can be stated that smectite
formation is a sort of a feed-back or
selfcatalized process that will lead to
complete destruction of the original
materials.
The phase rule
The dynamic aspect of hydrothermal
reactions has lead to the belief
that conditions of equilibrium cannot
be attained in an authentic thermodynamic
sense. Several authors suggest
the term «local or mosaic>>
equilibrium (KORZf~JNSKII, 1955;
THOMPSON, 1955). HELGESON et
al. (1969) termed it «partial equilibrium»,
which means that equilibrium
exists only between the solution
and the new forming phases.
A consequence of this controversy
was the modification of Gibb's phase
rule as follows:
where P is the maximum number of
phases present in a system at a determined
pressure, temperature and
solution composition, I is the total
number of« inert» components and M
is the number of «mobile>> components,
whose concentration or chemical
potential depends on the external
conditions of the system.
For this reason, in many hydrothermal
systems, where the number
of mobile components is very high,
the number of resulting phases is
minimal, or even a single one. This is
the reason why in our zone four
phases, at most, appear, as alteration
products. These are smectite, zeolite,
tridymite and some K-feldspar. As
mobile components, nearly all common
elements, Si, Mg, Ca, Na and
even Al, Fe and Ti can be considered.

28 J. Linares
The hydrolytic process on small and
large scales
The process on a small scale
should begin with the' hydratation of
feldspathic vitreous material in~
eluded in cinerite layers. This is followed
by devitrification, accompanied
by the appearance of nuclei of
growing neoformed crystals.
The hydration process consists of
the rupture of Si-0-Si groups, forming
part of more or less vitreous
structures, to form silanolic groups
-SiOH, which results in an expan- ·
sion of the Si0 4 network.
The speed of this process as a function
of temperature has been studied
. -~-~~---- --~---by-seVeraT___ 3ilthOrs (FRIEDMAN &
SMITH, 1960; MARSHALL, 1961) because
of its importance as an aid for
dating obsidiane artifacts through
the thickness of their hydration halo
or for the study of palagonite in submarine
igneous materials (MOORE,
1966; NOAK, 1981).
Devitrification is a far more complex
phenomenon, since it includes,
in our case, the nucleation and growth
of smectite crystals. LOFGREN (1970)
showed that hydration proceeds at
a faster rate (3 or 4 times in order of
magnitude) than devitrification.
LOFGREN also pointed out the great
influence of solution composition on
the process of devitrification. As an
example, the presence of minute
quantities of alkaline cations increases
the devitrification rate by 4
or 5 orders of magnitude.
It has been also shown that the net-
work expansion, taking place during
the hydration process, allows for a
_ gre_ater _interchange _between elements
contained in the vitreous
material and those in solution.
Therefore, the presence of electrolytes
in the hydrothermal solutions
must accelerate the hydrolysis reac~
tions. Since these are mass interchange
reactions between solution
and solid material, the solubility
product of smectite should be easily
attained, in our case.
From a macroscopic point of view,
the smectite formation promotes important
losses of matter, as can be
seen in this type of reaction equation.
For the case of smectite formation
from an albite rich material it can be
calculated that near 500 g of smectite
are formed per kg of albite, and
the remainder of matter is lost, including
Si and Na, in this case. Great
quantities of hydrothermal solution
are needed for the removal of silica in
soluble form. Now, then, given the
great instability of these solutions,
silica precipitates forming low
temperature tridymite when- the
temperature decreases slightly.
As for complete deposits, it was
feasible to calculate the loss of matter
taking place during bentonite formation,
by using a geochemical balance
such as that of BARTH (1948) and
taking into account the density of parent
rocks and bentonites. So, for the
«Sierra de Gata» the matter and
volume losses are 25% and 6%, respectively,
while for the «Serrata de
Nijar» they are are 40% and 25%.
Therefore, the formation of bentonite
maybe considered as one of the most

destructive processes existing in nature.
The higher volume loss in the
«Serrata de Nijar>> probably caused
the collapse of volcanic strata over-
. lying the bentonite level, and promoted
its extrusion through fractures,
giving place to diapiric structures.
Mass transfer and reaction rates
The process of hydrothermal alteration
is a typical example of an irreversible
phenomenon. As a conse-
\··
quence, the study of equilibria cannot
be made on the basis of methods of
classical thermodynamics. HELGE­
SON (1968; 1971) and HELGESON et
al., (1969; 1970a) were first in applying
the methods of thermodynamics
of irreversible processes to natural
systems, together with., the
theories of fluid mechanics, chemical
kinetics, transport theory and computer
technology.
The system utilized by HELGE­
SON is based on establishing the
reaction of alteration, as well as all
possible reactions between the
minerals and the species in solutions,
knowing the corresponding equilibrium
constant. In this way, a matrix
of stoichiometric reactions is
obtained. The corresponding system
of equations must be resolved as a
function of a parameter called «reaction
advancement>>. For each value oL
this parameter, the number of mols
of dissolved minerals or species in
solution, and that of minerals
neoformed by precipitation, if solubility
products have been reached,
The Process of Bentonite For;;_~tion ... 29
are calculated. In this way, the kinetics
of hydrolysis proce~ses can be
studied and the quantities of destroyed
and neoformed minerals can
be calculated for infinite stages of
evolution in the alteration process.
These studies have strongly aided
the understanding of the processe~
of hydrothermal alteration, not only
· in regard to problems of phyllosilicate
neoformation, but also; and
more important, in regard to the
formation of hydrothermal ore deposits
(HELGESON, 1979), whose
materials are transported in the complexed
form by solutions and precipitated
as a consequence of changes in
pressure, temperature or variations
in the chemical composition of fluids.
But this is a theme to be developed.
elsewhere.
A direct consequence of the study
of irreversible processes is the possibility
of calculating the time expended
in the formation of a bentonite
deposit. To do this, it was necessary
to use the equation derived by
HELGESON (1970b). The reacting
capacity of a solution is defined by its
H+ activity (HEMLEY & JONES,
1964). The more acid the solution, the
greater will be its reactivity. Thus, a
rate function can be derived
where:
ID; - n:tl = 2 ~T}Kt 1 / 2
m; = molatility of «i» species;
n:tl = molatility of «i>> species at zero
time;
~ ratio of the surface area of the
reactant mineral to that of the
rock exposed to the solution;

30
K
t
J. Linares
ratio of the surface area of the For porous media:
pores to the mass of water in
the system;
T]
rate constant;
Po
elapsed time. Ag mean surface of the grains;
Geothermal Gradient
1---------------;
15°C/Km
40°C/Km
4 Km
0
0
X
s...
.Cl
"'
8
3
s
6
2
Py
4
2
(S ML)
-------~-----
~ ---
100 200
Fig. 3- P,T diagram for 2:1 phyllosilicates (modified, after VELDE, 1977). S = Smectite; ML =
Mixed-layers, disordered; AI = Allevardite; I-Chl = Illite and Chlorite; Py = Pyrophyllite. Dotted
zone = Data from recent geothermal areas (ELLIS, 1979); Rectangle= Data from Cabo de Gata
bentonites.
'
300
oc

The Process of Bentonite Porfiiation ... 31
Ng = number of grains per liter;
Po = porosity.
If we suppose:
porosity = 0.25 (CABALLERO et al.;
1985);
radius of grains = 10- 3 cm;
s = 0.8 (according to mineralogical
and normative evidences);
K = 10- 9 (HELGESON, 1971);
mi - rrtl = 10- 3 (HELGESON et al.,
1969),
it can be concluded that:
t = 5·10- 3 days;
t for altering 1 kg of rock = 13 .3 days;
t for altering 5 ·10 5 Tm deposit
1.8·10 6 years;
water for altering the deposit
2.67·10 9 kg.
All these figures, although spe'Culative
are within the order of magnitude
of data reported for some other
well known deposits (SKINNER,
1979).
Phase diagram for 2:1 phyllosilicates
Finally, it will be oCinterest to
compare our set of data with others
derived for geothermal areas active
at present and to try to construct a
phase diagram for 2:1 phyllosilicates,
as a global result.
, Recently, ELLIS (1979) made a
compilation of existing data on
' geothermal areas. Some of them,
more directly related to our theme,
are summarized in Table 1.
The maximum temperatures of
persistence of montmorillonte and
mordenite are shown. In some cases,
the maximum depth is indicated.
Beyond these temperatures, smectite
is inexorably transformed to illite/
smectite interstratifications and then
to illite.
It can be concluded that the maximum
temperature for the existence
of montmorillonite is 200 °C, and the ..
maximum depth 400 m.
All these values can be compared
with those of VELDE's phase diagram
(1977) for diagenetized sediments
(Fig. 3); all data corresponding
to smectites plot into the smectite
field. However, it should be pointed
·out that the field of smectites should
be reduced in extension, since no
smectites are found in hydrothermal
environments at depths below 400 m.
, TABLE 1
Maximum temperature or depth for smectite and mordenite in modem geothermal areas
(data from ELLIS, 1979)
Locality
Hveragerdi, Iceland
Reykjavik, Iceland
Reykjanes, Iceland
Wairakei, New Zeeland
Yellowstone, USA
Hatchobaru, Japan
Salton Sea, USA
Smectite
100 m
200 m
400 m, 200°C
130 oc
100-200 oc
100°C
Mordenite
120°C
230°C
1oooc
170°C

J. Linares
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Miner. Petrogr .. Acta
Vol. 29-A, pp. 35-54 (1985)
Quantitative Determination of the Fine Structural Features
in Clays by Modelling of the X-ray Diffraction Patterns
CYRIL TCHOUBAR
Laboratoire de Cristallographie U.A. 810, U.F.R. de Sciences Fondamentales et Appliquees, BP 6759, Universite
d'Orleans, Rue de Chartres, 45067 Orleans Cedex 2, France
ABSTRACT- Actual structure of any clay mineral always shows important
departures from the ideal well-ordered structure which symbolizes each
group of microcrystallized phyllosilicates. Every departure forms a structural
defect in regard to the ideal structure. Structural defects in clays can be
classified in three categories: those affecting the layers themselves (cis- or
trans-vacancies, order-disorder in the isomorphous substitutions, etc.), those
specific of the interlamellar space (positions of the cation and of the intercalated
molecules) and stacking faults (including ~ change in the nature of
stacked layers): In addition, powder experimental patterns are generally
perturbed by a partial orientation of the particles in the powder. The paper
describes the influence of defects on the patterns and presents a general,
approach to the determination of the nature and abundance of defects in
clays with an indirect method of analysis. The intensities and shapes of the
diffraction bands are calculated for model structures and are fitted to the
experimental patt~rn. Such a method is applied to the determination of fine
structural characteristics of various clay minerals.
Introduction
It is obvious that the microcrystallized
lamellar silicates keep track,· in
their structural characteristics, of various
modifications of the physicochemical
and thermodynamical conditions
they have gone through dur-,
ing their geological «history». Therefore,
knowing the crystallochemical
specificities of these minerals enables

36 C. Tchoubar
the stacking of the layers within
particl~s. So we may observe, for in~
stance, modifications of the ion localization
in different crystallographic
sites, especially the octahedral sites
(for dioctahedral silicates). As well, a
degree, more or less important, of
order-disorder can exist in the distribution
of isomorphous substitutions,
or of the cations and of the
molecul.es intercalated in the interlamellar
space. Finally the structural
defects may affect the stacking mode
and the nature of the layers in every
particle, as well as the existence of
stacking faults of various types.
In order to obtain quantitatively
these various parameters, one often
-----------~--- -n.eeas-to--use-jOTntiY- the diffractometric
and spectroscopic methods
of investigation. Yet, the basic
method, while presenting its own
limits, remains X-ray diffraction.
Every attempt to interpret parameters
collected by means of other
methods of investigation has necessarily
to be backed by the results
achieved tl].rough the X-ray technique.
Thus, for a mineral with structural
defects, the diffraction pattern varies
considerably with the nature and
concentration of these defects as
well as with the shapes and sizes of
the interferential coherent domains.
These differences concern at once the
positions, the intensities and the
shapes of the reflections. This used
to make impossible, up to the last fe-w
years, the interpretation of such patterns
through the classical method of
direct analysis of experimental data.
Then one could usually just put for~
__ war.d some __)]ypgth,eses 0r1 the nature
of defects; but these hypotheses could
not be confirmed in a sufficient way
and, a fortiori, it was impossible to
determine either the concentration of
the defects or the rule of their distribution
in the crystal. BRINDLEY &
ROBINSON (1946) were among the
first ones to use this approach in the
study of clay minerals, to interpret
patterns of disordered kaolinites and
to explain the simultaneous appearance
of hkt reflections when k = 3n
(n integer) and of (hk) diffraction
bands when k i= 3n.
In fact, when dealing with poorly
crystallized minerals with an high
content of defects, the only way to
effectively obtain their actual structure
is to use an indirect method of
analysis· of the experimental patterns,
that we shall call the modelling
method.
This method consists in forecasting,
by means of calculation, the
effect of each kind of defect on the
diffraction phenomenon. Then, by
combining different defects in various
proportions in a mathematical
structural model adapted to each
clay mineral studied, one calculates a
synthetic diagram that will be compared
with the experimental pattern.
By modifying next the values of the
parameters characterizing each defect,
the theoretical diagram is fitted
to the experimental one, always looking
for agreement of the positions
and shapes of the reflections as well
as of their relative intensities. The
final structural model corresponding

Quantitative Determination of the Fi~~-Structural ... 37
to this agreement constitutes the actual
structure of the lamellar silicate
studied.
Such indirect approaches, as well
as the use of modelling methods, are
widely spread in various fields of
physics. As for the investigation of
phyllosilicates, this method has been
mainly developed in the French and
the Soviet laboratories of clay crystallography.
Principle of the mathematical formalism
for calculation of theoretical
diagrams
Depending on the authors and according
to the nature of the minerals
or to the kind of reflections, different
mathematical formalisms have 'been
put forward to calculate the diffrac- ·
tion phenomenon produced by powder
lamellar systems. These formalisms
gave an interpretation of the experimental
patterns, at first qualitative
and then quantitative. A good
survey of the corresponding papers is
given in the book edited by BRIND­
LEY & BROWN (1980). We shall just
point out a few fundamental works:
those of MERING (who was the first
to explain qua'Iitatively, by means of
a mathematical formalism, the main
features of powder patterns of clay~
and, in particular, of the diffraction
bands - MERING, 1949). In the
same way, MAcEWAN (MAcEWAN et
al., 1961), DRITS (DRITS & SAKHA­
ROV, 1976) and REYNOLDS (1980)
have given principles of calculation
of the OOl intensity distribution for
the intestratified clay minerals.
Yet we must point out that the
most powerful mathematical formalism,
to investigate the most general
cases, is the matrix notation. HEN­
DRICKS and TELLER introduced it
in 1942, for the study of lamellar systems·;
it was then completed and
adapted to clay studies and to different
kinds of reflections by various
authors (KAKINOKI & KOMURA,
1952; DRITS & SAKHAROV, 1976;
PLAN(:ON & TCHOUBAR, 1976;
1977; PLAN(:ON, 1981; SAKHAROV
et al., 1982a,b; PLAN(:ON et al.,
1983).
In the general case, for a powder
with particle orientation and various
thicknesses of the coh'etent domains,
the intensity diffracted at the· 28
angle by an hk rod is given by:
Ihk(s) = - 1 -
sQcr M
L a(M) J N(

38 C. Tchoubar
vectors and a plane normal to the hk
rod. Summation
systems can be distin-.
guished (PLAN> system, on the

Quantitative Detemzination qf the Fine Structural ... ~9
contrary, the concentration of defects
. of a given kind is only defined in average
for the powder, and varies from
a particle to another (Markovian model).
Most of the clays belong to this
latter case.
We can remark that the very principle
of the modelling method (to determine
the actual structure of a clay
by fitting of calculated and experimental
patterns) leads immediately
to a question:
- Wouldn't it be possible to obtain
virtually the same calculated diagram,
starting from several totally
different models?
For the purpose of answering this
question, a systematic analysis of
each possible model, based on the
crystallochemical viewpoint, has
been carried out for dioctahedral
phyllosilicates. This analysis investi-
./
gated the relationships between
structural characteristics and specificities
of diffraction patterns (DRITS
et al., 1984). This study has shown
that each kind of defect and structural
characteristic leads to a specific
feature in defined parts of the pattern,
and is insensitive in others.
Nevertheless, the uniqueness of solution
for determining the fine structure
of a clay will be reasonably
asserted, only if the investigation
process includes:
1. Successive considerations of al1
models which are crystallochemical-'
ly possible.
2. Calculations of intensity distribution
and profile variation in all accessible
domains of the reciprocal
space, obtained by changing only one·
parameter at a time that defines the
specific features and modifications in
the pattern, due to this parameter
(e.g., cation distribution in the individual
layers, nature of stacking
faults, etc.).
3. A systematic analysis of the calculated
patterns, to establish the diffraction
criteria which will help to
interpret the experimental data.
4. Agreement of the calculated and
experimental patterns, including the
position, shapes and relative intensities
of the various reflections used
- and this in a 28 angle range as
large as possible.
5. Finally, to make possible the comparison
between theoretical and experimental
data, it is essential to use
experimental patterns that have been·
obtained in very strict recording conditions,
as shown in the following
paragraph.
Recording conditions of the experimental
patterns
To be effective the modelling
method requires first of all the recording
of patterns in experimental
conditions in which all the functions
that can perturbe the diffraction phenomenon
itself are controlled: mainly
monochromatic radiation should
be used and the height and width of
the beam and slits, the thickness of
the sample and the orientation of
particles in the powder should be
controlled. Another point is to use a
detector with energy discrimination
that gives good accuracy in the in-

40 C. Tchoubar
tensity measurements and a strong
angular resolution. Therefore, it isessential
to use equipment with a
«step by step>> recording system or
with a linear detector.
Some of the perturbing functions
can be minimized so as to introduce
in patterns only modifications several
times smaller than those due to the
structural defects of the mineral studied.
This occurs, for instance, with
the optical functions (dimension of
the beam and slits, monochromaticity,
etc.).
Other perturbing functions, on the
contrary, cannot be minimized and
they have then to be included in the
_calculation to . establish their effect.
This is the case in particular with the
residual orientation of particles in
powder, that virtually cannot be
avoided with clay minerals.
The particle orientation function is
experimentally determined from the
OO.f reflections (TAYLOR & NOR­
RISH, -1966;· DE· COURVILLE et al.,
1979). Calculations prove that
orientation modifies relative intensities
as well as the profiles of every
reflection (PLAN(ON & TCHOUBAR,
1977; PLAN(ON, 1980). Figure 1
illustrates this phenomenon for the
case of a partly disordered kaolinite.
The curves in this Figure correspond
to the 002 and 003 reflections, and to
the (02,11) and (20,13) bands. The diagram
in dashed lines was calculated
for the case of a totally random
orientation of particles in powder
(ideal case of non-residual orientation);
and the curves in solid line
were obtained by introducing in the
calculation the particle orientation
function given in Fig. 2. This function
was experimentally determined for a
given partly disordered kaolinite. It
corresponds to a rather small particle
orientation in powder. In Fig. 2, the
1.000
500
(02, 11) band
n
'\ (002) reflection
h
11
11
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
,.,}
I
.,, (20, 13) band
0.21 0.25
0.30
0.35
0.40 s

Quantitative Determination of the Fine-Structural ... 41
Ne(~)
absorption on the experimental pattern.
Let us remember that intensity I
after absorption is related to the intensity
I 0 without absorption ,by
(GUINIER, 1964):
I= K IoSo
1 x . sin a sin y
J..LPX ·sin a sin a - sin y
[
exp( -~) -exp.( -~)]
sm a
sm y
~(deg)
o+--.--~-.--r--.-.--,-~~
0 10 30 50 70 90
Fig. 2 - N (~)function that characterizes· the
orientation of particles in the powder.
dashed line represents the orientation
function - after normalization­
-for a random distribution of parti- .
des. ~ is the angle between the (001)
plane of a particle and the plane of
the powder holder (~ = 90° corresponds
to particles perpendicular to
the plane of the holder); the dashed
line is horizontal because, for a random
orientation, the proportion of
particles at a given ~ angle is independent
of the ~value.
In the same way, effects due to
radiation absorption, beam polarization
and the presence of different
backgrounds due to air, to camera
windows and to sample-holders, etc.
cannot be avoided. So it is necessary:
1. To measure the absorption coefficient
and to correct the effects of
where:
K is a constant;
S 0 is the section of the incident beam;
a and y respectively the angles be­
, tween the incident beam and the
1sample plane, and between the scattered
beam and the sample. We have/
the following relationship:
y = a+29 (29 being the scattering
angle);
x is the thickness of the sample;
pis the volume density of the sample,
and
J..l is its coeffiCient of absorption per
mass unit.
This relationship corresponds to
·non-symmetrical 9,29 recording conditions
by transmission; J..LPX is experimentally
measured.
2 . .To correct the pattern of the effects
of X-ray beam polarization that results
from the beam reflection firstly
on the monochromator (for instance,
curved quartz) and secondly on the
sample. The total correction to be
brought to the experimental pattern
consists in multiplying each intensity

il
, I
'
42 C. Tchoubar
by a P factor given by (GUINIER,
1964):
where:
P=
1 + cos 2 28 0
8 0 is the angle of reflection on the
monochroma tor.
28 is the scattering angle.
such a fault between two adjacent
layers; ------------ -----
- Faults which we will name

Quantitative Detennination ofthe Firie_S-tructurai ... 43
ts.ooo
I
3000 I
10.000
5.000 1000
0.225 0.250
0.400 0.425
Fig. 3 - Calculed profiles of diffraction bands for a cis-vacant dioctaheqral smectite in two-waterlayer
homogeneous hydration state, containing random stacking faults (PA = 0.74). a: (02,11)
band; b: (20,13) band. Fig__:_3a corresponds also to (02,11) band profile calculated using standard
deviation 1? = 0.05 a 2 . The intensities are given in electron units.
for both types of stacking faults, in
the case of a two-water-layer dioctahedral
smectite (BEN BRAHIM,
1985). Figure 3 corresponds to the
presence of totally random faults
(due to arbitrary translations or rotations
of layers in their plane) 1
Whose
probability PAis 0.74; Figure 4 sh«ws
the calculated diagram in the case of
an average translation to (to
-0.3Ht), the same for all firstneighbouring
layers, but with an
3000 l
1000
0.400 0.425 stA- 1 J
Fig. 4 - Calculated profile of (20,13) diffraction
band for a cis-vacant dioctahedral smectite in
two-water-layer homogeneous hydration state,
containing stacking faits by fluctuation (8 2 =
0.05 a 2 ) around an average translation Cfo =
-0.311i') of the layers in their plane. The intensities
are given in electron units.
arbitrary fluctuation 8 = ~to around
this value such that the standard deviation
8 2 is 0.05a 2 • The values of 8 2
and PA were chosen so as to obtain an
identity of the calculated (02,11)
band profiles (Fig. 3a). So we can
observe that the presence of random
faults (Fig. 3b) gives a much more
modulated (20,13) band than when
faults exist with fluctuations around
to (Fig. 4).
On the other hand, if the mineral
contains only «partly defined» stacking
faults, the modifications on the
pattern differ according to the investigated
(hk) domains; moreover
some domains remain insensitive to
such stacking faults. Thanks to these
differences, it is possible to identify
each kind of these faults.
It is well-known, for instance, that
the (20,13) domain is modified very
,little (or not at all) by ±120° rotationb
al or ±- translational stacking
3
faults. On the other hand, both categories
of faults can be distinguished
by the e)):amination of the (02,11)

44 C. Tchoubar
130 100
65
80
60
40
20
0.22 0.24 0.26 0.28
Fig. 5 - Calcul::tted profile of the (02,11) band
for an anhydrous cis-vacant dioctahedral smectite
containing ±120° rotational stacking faults
(PR = 0.67). The intensities are given i) on the
left part in electron units x 10- 2 , ii) on the
_ :right part in arbitrary units.
bands. Indeed one can observe that
the presence of ± - faults is ex-
3
pressed by the appearance of a
b
steadily decreasing (02,11) band,
leading-~te~~an~-- effect---similar- to a
two-dimensional structure; on the
contrary the presence of ± 120°
rotational faults leads to a profile of
the (02,11) band where a minimum
of intensity, more or less pronounced,
can be found around s = 0.24A- 1 •
Figures 5 and 6 illustrate this fact
by giving the (02,11) band profiles
of an anhydrous dioctahedral
smectite with cis-vacant octahedral
positions and with the highest quantity
of faults (P = 0.67), respectively
b
of ± 120° and ± - types (DRITS et
3
al., 1984).
The same kind of distinction exists
too, though not as obviously, when
comparing the effects of n60° and
130 100
200-130
201-131
95 100
80
80
201-132
60
65 60
47.5
202-131
b
40
40
20
*
0.22 0.24 0.26 0.28 s ,;.:1)
0.38 .0,40 0.42 S(,~-1)
Fig. 6 - Calculated bands profiles for an anhydrous cis-vacant dioctahedral smectite containing ±
translation faults (PT= 0.67). a: (02,11) band; b: (20,13) band. The intensities are given i) on the left
part in electron ·units x 10- 2 , ii) on the right part in arbitrary units.
20

Quantitative Determination of the Ftize-Structural... 45
faults. Figures 7 and 8 show calculated
(02,11) and (20,13) bands for the
same smectite as in Figs 5 and 6, l;mt
with faults respectively of n60° and
types in equal quantities, e.g., p =
0.67 (DRITS et al., 1984). A superficial
qualitative examination of the curves
of Figs 7 and 8 seems to reveal a strict
analogy between the patterns corresponding
to n60° and
faults: for both types of faults there
exists only one modulation on the
two (20,13) bands at s = 0.415A- 1 ,
while both (02,11) bands show a
strong trend towards a: two-
dimensional structure. But in fact a
quantitative comparison .of both patterns
shows that the (20,13) band corresponding
to n60° faults presents a
more clearly pronounced minimum
at s = 0.4oA.- 1 than the one corresponding
to
faults. Furthermore, for this latter
kind of faults, the (02;11) band presents
an almost regular decrease between
s = 0.23A- 1 and s = 0.3oA.- 1 ,
while for the model with n60° faults,
the same band shows a minimum at s
= 0.2sA.- 1 and a modulation centred
on s = 0.30A - 1 • Besides, if we compare
only qualit~tively the (02,11)
bands on Figs 5 and 7, we might come
to the conclusion that the ± 120°
faults cannot be distinguished from
136 (20,13)
136 I
(02, 11)
68
68
0.22 0.24 0.26 0.28
0.38
Fig. 7- Calculated band profiles for an anhydrous cis-vacant dioctahedral smectite containing n60°
rotational stacking faults (PR =_0.67). a: (02,11) band; b: (20,13) band. The intensities are given in
electron units X 10- 2 . - . _

I
I'
46 C. Tchoubar
134
(20, 13)
134 I
67
67
0.22 0.24 0.26 0.28 0.38 0.42 s cA- 1 >
Fig. 8 - Calculated band profiles fo; an anhydrous cis-vacant dioctahedral smectite containing
-- - -- ---( -n 1 :c·m. 1-nn:·=--o-or 1; m = 0 or T) translational stacking faults (Pr = 0.67). a: (02,11) band;
b: (20,13) band. The intensities are given in electron units X 10- 2 .
the n60° faults, and that the ± -
3
faults cannot be distinguished from·
the
faults (Figs 6 and 8). In fact, the distinction
within both categories of
faults can be made immediately by
examining the (20,13) domain, which
is highly modified only for the n60° or
faults. This is obvious when comparing
the profiles of the (20,13) bands
in Fig. Sb and in Fig. 6b.
b
2. Determination of the defects inside
the layers
In a general way, in clays, defects
inside the layers are modifications
concerning either the position of
atoms in the unit cell, or the nature of
the cations (isomorphous substitu-.
tions, for instance). As a result of the
weakness of the X-ray atomic scattering
power, it is often difficult to detect
these categories of defects in the
patterns. obtained from natural, untreated
clays. Such samples generally
contain a large amount of stacking
faults which give intensity modifications
that are higher than those due
to the defects inside the layer. So, to
reveal these defects, the effects of
stacking faults have to be minimized
by reorganizing the stack. There are

Quantitative Determination. of the -pZ:r!e Structural ... 47
20 20
10 10
\~-·-
o·-.1-~""'o!;-.22-~--0,..-.24--r-_ -0.~26--,---~,-,,;--:"'- 1 1 _.
0.22
' '
..
'·
\'----
0.24 0.25 s ($.-11
Fig. 9- Experimental profiles of (02,11) bands of two anhydrous Na-beidellites. a: Black Jack Mine
beidellite; b: Rupsroth beidellite. The intensities are given in electron units.
two ways to obtain a better order in
the layer stackings: the first one is to
saturate the mineral with potassium
and to use several wetting and drying
cycles (MAMY & GAULTIER, 1976).
The second one is even more simple
and consists only in saturating the
clay with cesium (BESSON et al.,
1983).
For ir,tstance, if our objective"is to
determine the nature of octahedral
vacancies in a dioctahedral smectite,
the analysis of the non-saturated
mineral does not lead to any conclusion.
Figure 9 shows the experimental
(02,11) bands of the anhydrous Nabeidellite
from Black Jack Mine (Fig.
9a) and from Rupsroth (Fig. 9b): we
can see that both bands differ littie
from each other and that, moreover,
the slight differences appear in a part
of the patterns sensitive to stacking
faults. Therefore these recordings do
not permit any statement about
octahedral vacancy positions. But cal- '
culations show that the diffraction
(02,11) domain for a model of anhydrous
Cs-beidellite presents great differences
when the vacant sites are in
«trans>> positions (Fig.-10a) or «cis»
positions (Fig. lOb), or are statistically
distributed between all octahedral
sites (Fig. lOc). If we compare these
Fig. 10 ~-Calculated profiles of (02,11) bands
for Cs-beidellites with three different positions
of the octahedral vacancies. a: transvacant
beidellite; b: cis-vacant beidellite; c:
beidellite with statistical distribution of octahedral
vacancies between the three octahedral
site types.

48 C. Tchoubar
theoretical patterns with the experimental
ones obtained from Black
Jack Mine and Rupsroth anhydrous
Cs-beidellites (Figs 11a, b), we can
come to the conclusion, without any
ambiguity and on the single basis of a
qualitative comparison, that the
Black Jack Mine beidellite is a
«trans»-vacant mineral while Rup-
..
. .
20 ..
sroth beidellite has «cis»-vacant
octahedral-~sheets---(BESSON, 1980;
BESSON et al., 1983). A quantitative
study, based on the agreement of profiles
and intensities between the
calculated and experimental patterns,
shows that the presence of
faults in the octahedral vacancy positions
cannot be detected if the pro-
a
r...
•
10 I \
20
I
·. :..'
\ ..
.... ~
/
./'
;
.
. .
; '
0+--A~.----.-----.-----.----.-----.----.-----.--~
10
0.22
\
-~
0.24
,
· rol · i
........ . ;"-..;.,.,
•• jll
·~
.. .. .­;
;.
.
•
\
0.26 0.28
b
.
!' ..
\
....
s (fl.-1 l
i
0.22
0.24
0.26 0.30
s (A- 1 l
Fig. 11 -Experimental profiles of (02,11) bands of two anhydrous Cs-beidellites. a: Black Jack Mine
beidellite; b: Rupsroth beidellite.

Quantitative Detennination oftherlne Structural ... 49
portion of these faults is lower than
10% (because of the existence of residual
stacking faults in the Csminerals).
3. Determination of the distribution of
atoms and molecules in the interlamellar
space
guish: i) sites projected close to basic
oxygens of the layer (A1 sites), ii)
those projected close to the tetrahedral
cations (B sites), and iii)
those projected close to the centre of
the «hexagonal» cavities (C sites).
Having i:wticed that the two categories
of sites Band C can be deduced
one from another by changing their y
1
coordinates into y ± -, the authors
. . 3
have considered the simultaneous
presence of identical change of y­
cobrdinates of the A1 sites, leading to
two enantiomorphic site distributions
called Az and A3 (see Figs 12b, c).
The calculation of theoretical patterns
from these different models
leads to the following conclusions:
1. The (20,13) domain does not permit
one to distinguish A1, Az, A3 sites
from one another, orB sites from C
sites. In this domain, the profiles and
intensities of reflections an~ only
sensitive to the ratio (A1+Az+A3)/
(B+C), where (A1+Az+A3) and (B+C)
To illustrate this case, we want to
describe a work about the investigac
tion, by X-ray diffraction, of Rupsr6th
Na-beidellite in homogeneous
hydration states corresponding to a
two-water-layer hydrate (dool
15.2SA; BEN BRAHIM et al.;. 1984)
and to a one-water-layer hydrate (dooi
= 12.4A; BEN BRAHIM et al., 1986).
a) Three different categories of
sites are put forward in the literature
for clays with water molecules in
two-water-layer homogeneous,l:J.ydration
state.
Figure 12a shows the projection of
the possible positions of water molecules
on the {i,b) plane: we distina)
b)
Fig. 12 - Projection on the (a, b) plane of possible water molecule sites in a two-waterclayer
· ·homogeneous hydration state of smectite.
. c)

so
C. Tchoubar
are the total amounts of water molecules
in the A and (B+C) sites.
2. In the (02,11) domain, the diagram
is modified according to the
ratio B/C; but the pattern remains entirely
insensitive to the distribution
of water molecules between the different'
A-site types.
3. On the contrary, the (04,22) domain
shows significant modification
when the A1 sites or the Az sites are
occupied by water. Yet it is impossible
to distinguish the two enantiomorphic
occupations Az and A3.
Lastly when comparing the calculated
and experimental patterns in
the (04,22) domain, we can conclude
that the A 1 -sites are vacant and that
·---------- "--
the water molecules in the A-site are
situated only in the Az or A3 sites,
Moreover, this comparison shows
that the simultaneous occupation of
the Az and A3 sites in the same water
sheet must be excluded.
The number of water molecules
per ~-uni LcdLand~their_z-coordinates
are defined from the comparison of
the ratios Ioodloo3 and Ioodloos (BEN
BRAHIM et al., 1983). Lastly, the a­
mount of the water molecules distributed
on the B, C and Az (or A3) sites
are determined by fitting profiles and
intensities of the calculated pattern
with the experimental one, simultaneously
in the three (02,11), (20,13)
and (04,22) domains.
The final agreement is shown in
Figs 13 and 14 where the calculated
spectra are represented by solid lines
while the experimental intensities,
point by point, are represented by
triangles. Figure 13 corresponds to
the (02,11) band and Figure 14 to
both (20,13) and (04,22) bands; in this
latter Figure the curve represented
by squares corresponds to the calculated
(04,22) band, before superimposition
of the (20,13) band (dashed
46 I
23
0.225 0.250
0.275 s (.~-1)
Fig. 13 - Two-water-layer Na-beidellite in an homogeneous hydration state: final agreement
between the calculated (solid line) and experimental (triangles) profiles in the (02,11) band
domain. The intensities are given in arbitrary units.

Quantitative Determination of ihe-Fi~e Structural ... 51
9 I
0.375
Fig. 14 - Two-water-layer homogeneous hydrated Na-beidellite: final agreement between the
calculated and experimental profiles in the (20,13) and (04,22) band domains. The intensities are
given in arbitrary units.
line part). This agreement is obtained
with the following values of structural
characteristics:
- Basal distance door = 15.250 ±
o.oo5 A.
- Probability of arbitrary stacking
faults PA = 0.74.
- z-coordinates of water molecules z
=; ±6.3A (origin at the center of the
octahedral sheet).
-Total number of water molecules
per 1,1nit cell = 10.8.
- Number of water molecules per
unit cell, in the A2 (or A 3 ) sites: 7.5; in
B-sites: 2.6; in C-sites: 0.7.
b) A similar investigation was carded
out in the case of a one-waterlayer
homogeneous hydrate; the different
occupation sites of the water
molecules, still being the sites Ar, A2,
A 3 , Band C. It was proved that, once'
again, these molecules are distributed
between A, Band C-sites so as to
build an hexagonal insaturated plane
network. This water sheet is situated
in the middle of the· interlamellar
space, while the Na+ cations remain
inserted in the pseudo-hexagonal cavities.
The use of the modelling method
has put forward· a distinctive
feature in the structure of Na-beidellite
in the one-water-layer state, the
first-neighbouring layers systematically
show a translation along b,
b b
equal, arbitrary, to +-or--; this
.. 3 3
had not been observed either in the
·two-water-layer hydrate, or in the
anhydrous state of the Na-beidellite
(BESSON, 1980). The consequence of
the presence of such translations is
that, in each interlamellar space, the
basic oxygens and the Na+ cations,
situated on both sides of the water
molecules plane show an identical
configuration in regard to the water
molecules: this constitutes for the
latter ones a symmetrical and stable
configuration which could not be realb
ized without±- translations.
3
The final agreement between the

52 C. Tchoubar
90 I
0.225 0.250 o.m s !A·'>
Fig. 15 - One-water-layer homogeneous hydrated
Na-beide!lite: final agreement between
the calculated and experimental profiles in the
(02,11) band domain. The intensities are given
in arbitrary units.
b
_al stacking Jault_s equal to + -
3
b
or
3
- z-coordinates of water molecules:
z = ±6.2A (origin at the center of the
octahedral sheet).
-Total number of water molecules
per unit cell: 6.
-Number of water molecules, per
unit cell, in A sites: 4; in B sites: 1; in
C sites: 1.
experimental and the calculated patterns
is shown in Figs 15 and 16. This
agreement is obtained with the following
values:
- Basal distance doo1 = 12.400 ±
0.005 A.
- Probability of arbitrary stacking
faults: PA = 0.70.
-Systematic existence of translation-
Conclusions
The modelling. method of powder
patterns is the only way to solve a
significant part of the problems connected
with the determination of the
actual structure of clays by using X­
ray diffraction. It remains effective
27
0.400
0.425 0.450
Fig. 16 - One-water-layer homogeneous hydrated Na-beidellite: final agreement between the
calculated and experimental profiles in the (20,13) and (04,22) band domains. The. intensities are
given in arbitrary units.

Quantitative Determination of the Fine Structural ... 53
even when the experimental pattern
is reduced to a series of slightly modulated
(hk) bands. However, to obtain
the fine structural characteristics of
each clay as well as the proportion
and the nature of main structural defects,
it is necessary, in all cases, firstly
to use «good>> experimental patterns·
(e.g., recorded in strictly controlled
experimental conditions);
secondly to fit quantitatively the
calculated and experimental patterns,
not only on the basis of profile
and peaks position agreement, but
also by comparing the intensity
values. Obviously, the better the
ordering of each stacking the more
precise the final solution will be.
We emphasize the fact that devising
a model that contains structural
defects does not result from an arbitrary
choice between an infinite number
of possibilities. The choice of a
model must always be based on and
controlled by crystallochemical considerations.
It also depends on the various
independent parameters that
may be obtained through diverse
techniques, especially others than
diffractometric ones. In such conditions
the number of models which
must be taken into consideration is
considerably reduced; it is then fairly
easy to test them and find out which
one corresponds to the physical reality
of the mineral studied.
'REFERENCES
BEN BRAHIM. J., 1985. Contribution a /'etude des systemes eau-argile par diffraction de rayons X.
Structure des couches inserees et mode d'empilement des feuillets dans les hydrates homogenes a
une et deux couches d'eau de la beidellite-Na. Ph. D. Thesis, University of Orleans, France.
BEN BRAHIM J., ARMAGAN N., BESSON G., TCHOUBAR C.,.1983. X-ray diffraction studies on the arrangement
of water molecules in a smectite. I. Homogeneous two-water-layer Na-beidellite. J. appl.
Crystallogr. 16, 264-269. -
BEN BRAHIM J., BESSON C., TCHOUBAR C., 1984. Etude des profils des bandes de diffraction X d'une
beidellite-Na hydratee a deux couches d'eau. Determination du mode d'empilement des feuillets et
des sites occupes par I' eau. J. appl. Crystallogr. 17, 179-188.
BEN BRAHIM J., DRITS V.A., TcHOUBAR C., 1986. Determination, par diffraction X, des caracteristiques
structurales fines d'une beidellite-Na a l'etat d'hydrate homogene a une couche d'eau (d 001 = 12.4
A). To be published in Clay Minerals. .
BESSON G., 1980. Structur~ des smectites diocta.edriques. Parametres conditionnant les fautes d'empilement
des feuillets. Ph. D. Thesis, University of Orleans, France.
BEssoN G., GLAESER R., TcHouBAR C., 1983. Le cesium, reve[ateur de structure de smectites. Clay
Minerals 18, 11-19.
BRINDLEY G.W., BROWN G., 1980. Crystal Structures of Clay Minerals and their X-ray Identification
(G.W. Brindley and G. Brown, editors), Mineralogical Society, Monogr: no. 5, London.
BRINDLEY G.W., ME.RING J., 1951: Diffraction des rayons X par les st;ructures en couches desordonnees.
Acta crystal!ogr. 4, 441-447. ·
BRINDLEY G.W, RoBINSON, K, 1946. Randomness in the structures ofkaolinitic clay minerals. Trans.
Faraday Soc. 42B, 198-205. ·
DE COURVILLE J., TCHOUBAR D., TCHOUBAR C., 1979. Determination experimentale de la fonction d'orientation;
son application dans le calcul des bandes. J. appl. Crystallogr. 12, 332-338.
DRITS V.A., PLAN90N A, SAKHAROV B.A., BESSON G., TSIPURSKY S.l., TcHOUBAR C., 1984. Diffraction
effects calculated for structural models of K-saturated montmorillonite containing differen,t types
of defects. Clay Minerals 19, 541-561.

54 C. Tchoubar
DRITS V.A., SAKHAROV B.A., 1976. X-ray Structure Analysis of Interstratified Minerals. (In Russian).
Nauka, Monogr. 295, Moscow. . ·
GurNIER A., 1964. Theorie et Technique de la Radiocristallographie.,Dunod;-Paris,--
HENDRICKS S.B., TELLER E., 1942. X-ray interference in partially ordered layer lattices. J. chem. Phys.
10, 147-167.
KAKINOKI J ., KoMURA Y., 1952. Intensity ofX-ray diffraction by one dimensionally disordered crystal. I.
General derivation in cases of the «Reichweite» S = 0 and I. J. phys. Soc. Japan 7, 30-35.
MAcEwAN D.M.C., Rurz AMIL A., BROWN G., 1961. Interstratified Clay Minerals, in: The X-ray Identification
and Crystal Structures of Clay Minerals (G. Brown, editor), Mineralogical Society,
London.
MAMY J ., GAULTIER J .P ., 1976. Les phenomenes de diffraction des rayonnements X et electroniques par
les reseaux atomiques. Application a /'etude de l'ordre cristallin dans les mineraux argileux. II.
Evolution structurale de la montmorillonite associee au phenomene de fixation irreversible du
potassium. Ann. Agron. 27-1, 1-16.
MERING J ., 1949. Interferences des rayons X dans le systemes a stratification desordonnee. Acta crystallogr.
2, 371-377.
PLANt;:ON A., 1980. The calculation of intensifies diffracted by a partially oriented powder with a layer
structure. J. appl. Crystallogr. 13, 524-528.
PLANt;:ON A., 1981. Diffraction by layer structures containing different kinds of layers and stacking
faults. J. appl. Crystallogr. 14, 300-304.
PLANt;:ON A., DRITS V.A., SAKHAROV B.A., GILAN Z.I., BEN BRAHIM J ., 1983. Powder diffraction by layered
minerals containing different layers and/or stacking defects. Comparison between markovian and
non-markovian models. J. appl. Crystallogr. 16, 62-69.
PLANt;:ON A., TcHOUBAR C., 1976. Etude des fautes d'empilement dans les kaolinites partiellement desordonnees.
II. Modele d'empilement comportant des fautes par rotation. J. appl. Crystallogr. 9,
279-285.
Pl::A,I'It;:O_NA., TcHOUBAR C., _1977. Determination of structural defects in phyllosilicates by X-ray diffraction.
I. Principle of calculation of the diffraction phenomena. Clays Clay Miner. 25, 430-435.
REYNOLDS R.C., 1980. Interstratified Clay Minerals, in: Crystal Structures of Clay Minerals and their
X-ray Identification (G.W. Brindley and G. Brown, editors), Mineralogical Society, Monogr.
no. 5, London. · .
SAKHAROV B.A., NAUMOV A.S., DRITS V.A., 1982a. X-ray diffraction by mixed layer structures with
random distribution of stacking faults. (In Russian). Dokl. Akad. Nauk SSSR 265, 339-343.
SAKHAROV B.A., NAUMOV A.S., DRITS V.A., 1982b. X-ray intensities scattered by layer structure with
short range ordering parameters S > I and G > I. (In Russian). Dokl. Akad. Nauk SSSR 265,
871-874.
TAYLOR R.M., NoRRISH K., 1966. The measurement of orientation distribution and its applications to
quantitative X-ray diffraction analysis. Clay Minerals 6, 127-141.

Miner. Petrogr. Acta
Vol. 29-A, pp. 55-70 (1985)
Crystalline Defects in Layer Silicates
MANUEL RODRIGUEZ GALLEGO
Departamento de Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Granada, 18002 Granada,
Espafia
ABSTRACT- Sheet silicates contain a wide variety of deviations from perfect
crystalline periodicity. Such structural imperfections can be classified into
the following groups:
1) Point defects;
2) Line defects (i.e. dislocations);
3) Plane defects (i.e. stacking faults, etc.);
.4) Volume defects (intergrowths,Jamellar exsolutions, grain boundary, etc.).
'Since the early days much attention has been paid to plane defects (polytypism)
and volume defects (mixed-layers, intergrowths), due to the well known ,
fact that such kinds ofimperfections are easily treated, by X-ray diffraction
analysis, or more recently, by high resolution transmission electron microscopy.
Thanks to the latter technique, beautiful examples of detailed photographs
of these defects can be obtained. ·
Unfortunately, point defects suchs as: ordering, vacant sites, interstitial
atoms, and electron-holes, are less treatable by conventional X-ray diffraction
studies. For the most part, single-crystal techniques (the only reliable
method) can not be used, due to the frequent small crystal size of most of the'
layer silicates .(clays).
Other methods used for quantitative or semiquantitative work such as: X­
rays and neutrons'in powder profile-refinement, nuclear magnetic resonance
spectroscopy and ultJmately induced thermoluminescence, show potential
for qualitative and quantitative research work.
In fact, the technique of induced thermoluminiscence yields information
easily quantifiable, through de-excitation spectra (analysis of the glow curve
intensity) and electron trap activation energy, which can be related to both,
number of defects present and chemical composition of the clay mineral, as a
whole. Different examples of .the mentioned facts are shown.
Since extrinsic factors, such as impurities in the crystal and oxidation state
(when multivalence elements such as iron, titanitJ.m, etc., are present) can
affect the defective character of a mineral, it follows that the study of defects
can yield valuable information about the geological behaviour of the clay
minerals. Keeping in mind that the kind and number of crystalline imperfections
present in a certain structure is the result of its «geological history>>, it
can be concluded that the «correct reading» of such a

56 M. Rodriguez Gallego
rent degrees of ordering, altogether,
are familiar facts to the clay mineralogist
that early became familiar
with their defective character.
However, not allthe different types of
crystalline ·imperfections have been
object of the same attention by the
clay mineralogists. As a matter of fact
much attention has been paid to certain
kinds of defects (i.e. polytypism
intergrowths, etc.); on the other
hand, until recently, the most popular
techniques used in clay research,
such as X-ray diffraction, and electron
microscopy, often are not the
best ones to study some of them (i.e.
point defects).
Two well known facts related to
-----~-------------- --- ffi.e- most 'frequent-- crystallirle imperfections
in clay phyllosilicates are
easily detected in a powder diffracto- .
gram:
1.- The presence or absence(l) of a
rational sequence of higher orders of
reflection and
2. - The broadening of the reflections,
which in accordance to the well
known Scherrer's law, is related to
the crystal size or better, to the «crystallinity»
of the material (2). This
measure of crystallinity has ·been
related to the chemical composition
(RODRIGUEZ GALLEGO et al., 1964;
1969) and with genetical characteristics
such as diagenesis (ESQUEVIN,
1969).
Certainly, such diverse facts are included
in the relationship in such a
way that to obtain a useful analysis of.
the phenomepon, ~- systematic
approach to the different kinds of
crystalline defects present in clays,
has to be done.
Excluding quantum defects, re~
lated to lattice vibrations (phonons,
excitons, etc.), crystalline imperfec"
tions can be classified into the following
groups:
. 1. Point defects;
2. Line defects or dislocations;
3. Plane defects (polytypism, etc.);
4. Volume defects (intergrowth, exsolutions,
etc.).
Point defects
Since silicates are mainly of ioniccharacter;
the so-called intrinsic defects
i.e., vancancies and different
charge imperfections, are of outstanding
importance. Their only
limitation is that the global electrical
neutrality of the lattice be preserved.
Such defects play a fundamental role
in intrareticular diffusion, which
affects deeply mineralogenetical processes.
Certainly, the diffusion coefficient
is influenced considerably by
the kinds and energy of the point defects,
as far as an atom can move
from a certain lattice position to a
near by vacant site, provided that
enough energy (thermal) is available,
to surpass the potential barrier I
(activation energy).
(1) As REYNOLDS & ROWER (1970) have shown it can be due to the existence of very thin
crystallites. .
(2) Also, stress, microtwinning, dishomogeneities, bending, etc. can induce the same effect of
broadening.

Crystalline Defects in Layer Silicates 57
In general the diffusion coefficient
can be expressed by an equation such
as:
Equation (1) can be rewritten:
0 = !lo - RT ln (yX) then:
Do = D;v Xv exp ( - :T ) wher~: ln (yX) =
!lo
RT
and:
d = distance of displacement of the
atom;
Xv = fraction of vacant sities in the
lattice;
!l = potential barrier;
v = vibrational frequency (in general,
a fraction of the Debye crystal vibrational
frequency). ·
Certainly, the exponential term
and Xv are dependent on temperature
as will be shown. A thermodynamic
approach to the problem, provided
that certain premises can be
accepted, is the following: "
1.- A vacancy can be formulated
as a chemical equilibrium such as:
0 = Va• + Yx·
2.- A vacant structure can be expressed
as an ideal solid solution:
ideal structure-vacancies.
3.-A vacancy is a lattice site with
chemical potential null: !l = 0.
The classical expression of the
chemical potential is:
for:
!l = !lo- RT ln (y X) (1)
y X = fraction of vacant sites and !lo
the free energy of defect formation:
yX = exp
and sub~tituting
in (2),
yX = exp ( - :~x), and if
is the concentration of defects c,
and finally:
c = exp.
AHx -. ARSTx )
( RT
The calculated values for AHx in
oxides are 30-50 kcal!mol (i.e. 1 to 2
CV).
The double dependence of the
diffusion coefficient Do, on the
temperature is shown by the above
expression.
On the other hand the "energy of
migration measured in oxides is a­
bout 50-80 kcal/mol for cations.
The following empirical relationship
can . be used to calculate
diffusion
QD
D = Do exp - --· where
RT
y
X
(2) . QD = activation energy, directly re-

58 M. Rodrfguez ·Gallego
lated to the vacancy enthalpy AHx
(LASAGA, 1980).
Electron-ho?e
These kinds of defects have been
extensively studied in halides and
oxides, but until recently they have
not attracted the attention of clay
researchers.
Defects of such nature have been
studied by MARFUNIN (1979) in
quartz. If Si atoms are replaced by
multi-valence elements (Ti, Fe) orAl,
electrons can be identified with TP+
ions (Ti 4 ++e-) and «holes» by AP+ or
.. __ ~ -~-~ __ Ee 3 +. In order: to stabilize an «electron>>
(Ti 4 ++e-), a «compensator ion>> is required,
usually H+, Li+, Na+ K+; in
their absence the defect be> is stabilized by an oxygen
ion comparted by two silicon ions:
oz- ____,. o- + e-: o-Al orAl 0 4 -4. So
the quartz irradiation induces
«holes» Al 0 4 + 4 and a «compensator>>
ion (H+, Li+, Na+) changes to zero
charge.
In the case of Fe 3 + the

is the half-width of the thermoluminescence
curve at its half-height,
and T is the peak temperature of the
de-excitation curve.
LEEMONS & McATEE (1983) have
studied activated smectites with
different degrees of octahedral and
tetrahedral substitutions, and also
with different exchange cations. In
Na samples an excellent correlation
between glow intensity and
octahedral charge deficit, has been
found. The same authors detected an
increase in the number of «holes» in
Li and K samples. In the latter, the
number of «holes» is proportional to
the tetrahedral charge deficit. This
increment is proportional to the total
charge deficit for the Li samples.
These results are not valid for nontronite
whose high Fe content quenches
the thermoluminescence signal. '
In this way we have begun research
on thermoluminescence induced
by ~-radiation: on biotite, vermiculite,
chromium mica (mariposite)
and regular mixed layer illitebeidellite
(RODRIGUEZ GALLEGO ·
& ALIAS, 1965). The results are in
general in agreement with LEEMONS
& McATEE's (1983) mentioned
above.
Other methods
With respect to the mentioned,
mariposite (MARTIN RAMOS &
RODRIGUEZ GALLEGO, 1982) after
a structure refinement, we detected
ordering in the octahedral vacancies,
such that the symmetry of the lattice
Crystalline Defects in LaYer-Silicates 59
was inconsistent with the c character,
in accordance with the presence
of extragroup reflections h + k =
2n-1. On the contrary, no conclusion
was reached related to possible
ordering in the Si,Al tetrahedral replacement.
In this respect, NMR (Nuclear
Magnetic Resonance) has been much
more resolutive, thanks to the results
obtained by FYFE et al. (1983) and
more recently by SANZ & SERRA­
TOSA (1.984). Only the perturbing
effect induced by the Fe content, so
frequent in clay minerals, casts a shadow
on the possibilities of this technique.
On the other hand NMR yields
excellent results in studies of the Al
distribution, between the tetrahedral
and octahedral layers of clay phyllo-,
silicates with low Fe contents as
shown recently by THOMPSON
(1984).
Line. defects
Dislocations
In opposition to the previously
mentioned imperfections, line, plane,
and volume defects are irreversible
and difficult to quantify.
There are two main types:
a) Edge dislocations and
b) Screw dislocations.
The former occurs by the slip of a
reticular plane with respect to the
· next, for a few atomic positions. The
perturbation takes place along a row
of atoms. As a consequence the lattice
rests undistorted or unstrained,

60 M. Rodriguez Gallego
y
Fig. 1 - HRTEM photography of a dislocation
in goethite. The arrow indicates terminating
lattice fringe (from SMITH & EGGLETON,
1983).
Without them, they would not have
place.at the crystaLsurface.
Related to the screw dislocations,
they define a limit between a slipped
plane and the normal one (undistorted)
but in this case, the frontier
among them is parallel to the creep
direction.
The dislocations play an outstanding
role in the acceleration of the following
genetic processes:
a) Diffusion;
b) Heterogenous nucleation and exsolution
phenomena;
c) Crystal growth.
Closely related to the screw dislocation
are the Moiree figures, or
peculiar images in transmission electron
microscopy, in exceedingly thin
particles of layer silicates.
If the crystalline layers are
homogenously settled (Fig. 2a) the
except in the surroundings of the dislocation
(Fig. 1).
This dislocation needs a small
strain to be displaced, with the obvious
bonding breakage and rebonding.
Since the elasticity of the crystal
changes (by a factor of hundred!) the
role of such dislocations on the plas- .
ticity of the minerals is outstanding.
On the other hand, the possibility
of their displacement, adds a new
capacity for modification in the concentration
of point defects. Therefore,
they are a most important factor in
the maintenance of the thermal
equilibrium of such imperfections.
Fig. 2 - Model of: a) Crystalline layer homogeneously
settled. b) Crystalline layer homogeneously
perturbated by a screw dislocation
(from BOLLMANN, 1976).

phenomenon does not occur but if
screw dislocations are present (Fig.
2b) in the transmission electron
micrograph, alternate clearer and
darker areas are observed, as can be
seen in (Fig. 3) in a regular mixedlayer
illite-beidellite studied by ·us
(RODRIGUEZ GALLEGO, 1968),
with a layer thickness of about 100 A.
Plane defects
In this part defects related to
order-disorder in the stacking of
layers of identical nature will be examined.
Such defects are of two
kinds:
a) Translation and rotation defects;
b) Interstratification.
••
Fig. 3- Transmission electron microscope photography
of a regular illite-beidellite mixedlayer
(x 40.000) (from RODRIGUEZ GALLEGO,
1968). -
Crystalline Defects in LayerSil{cates 61
The first phenomenon causes that
no periodicity occurs in the lattice, in
the ao and bo directions. A multilattice
in the C 0 direction has to be
considered. As a consequence, the
(001) reflections are not affected but
the (hkO) and (hkl) reflections resolve
in asymmetrical bands or vanish.
Such facts induce subtle differences.in
the lattice free energy. Then,
the affected minerals can grow in
different geological environments. So
the 3T polytype muscovite seems to
be igneous only, although we (MAR­
TIN RAMOS & RODRIGUEZ GAL­
LEGO, 1980) have found this poly- ·
type in gneiss. But the most frequent
polytypes in white metamorphic
_ micas are the ZM1 and 1M.
In several cases, we (MARTIN
RAMOS & RODRIGUEZ GALLEGO,
1980) ·have found microcrystals of
metamorphic mica with the lM
and ZM1 polytypes coexisting.
TCHOUBAR (1980) has shown
beautiful pictures (Fig. 4) from High
Resolution Transmission Electron
Microscopy (HRTEM) of margarite,
with both polytypes coexisting in
contiguous crystalline dominions of
the same crystallite.
The second case to be examined results
from the stacking of layers with:
different chemical compositions.
Such an occurrence is a very common
one in clay phyllosilicates (but not
~xclusive to them). They are the
mixed layer or interstratified minerals.
Since early days two broad.
groups have been established:
1) Regular mixed-layer minerals and
2) Random mixed-layer minerals.

62 M. Rodriguez Gallego
Fig. 4- HRTEM photography of margarite. Polytypes !M and IM1 coexisting (from TCHOUBAR,
1980).
Regular mixed-layers
These kinds of materials have a definite
periodicity, and they are built
by layers, which alternate quite regularly,
with a lattice sum of both
«elemental» lattices. So, the mineral
chlorite can be defined as a regular
interstratification of talc layers and
brucite layers. BUSECK & VEBLEN
(1981) have obtained beautiful pictures
of clinochlore by High Resolution
Electron Microscopy, where it is
possible to detect the talc layer and
the brucite layer (Fig. 5).
In the majority of the described
materials, such elemental layers
show evident chemical and structural
similarities. Then, it can be
assumed that these slight differences
evolve from defects which have clustered
in alternate layers. Some facts
support this hypothesis. We have described
a regular mixed-layer (RO-
Fig. 5- HRTEM photography of clinochlore. Alternate
ofbrucite-like (B) and talc-like (T) layers
are visible (from BUSECK & VEBLEN, 1981).

DRIGUEZ GALtEGO &
Crystalline pefects in Layer sifi~~tes 63
GARCIA
CERVIGON, 1974) exceptionally well
crystallized (Fig. 6), built by alternate
layers of swelling chlorite and a
vermiculite like mineral with a (001)
basal spacing at 28 A, expandable
with ethylene glycol to 31 A, and after
heating to 500 oc collapsing to 22 A.
When a Li+ saturated sample was
heated to 200 °C, the (001) reflection
vanished and only a (002) reflection
at 13.3 A was observed (Table 1). It
can be assumed that the swelling
chlorite octahedral layers have
vacant positions, and Li+ migrates
into them. Such layers obtain analogous
electronic density with respect
to the vermiculite layers. Then, the
(001) reflection disappears, only un-.
mixed reflections i.e. (002) persist.
The circumstance that IIfOSt of
such minerals have Fe 2 +, m~kes
possible the creation of vacancy defects,
through the oxidation of Fe 2 +,
and the subsidiary expulsion of other
ions (Mg, Fe 2 +) as a function of the
oxidizing conditions. Such hypoth- .
eses have been verified (NIETO &
RODRIGUEZ GALLEGO, 1981) by
studying the oxidative attacks of iron
D.A.+SD~
D.A.+550 2 C
D.A.+EG
O.A.
N
"'
N
45 40 35 30 25 20 15 10 5 2
Degrees 29 CuKa
Fig. 6 - X-ray diffractograms of oriented
aggregates of a regular mixed-layer swelling
chlorite-vermiculite natural and after different
treatments (from RODRIGUEZ GALLEGO &
GARCIA CERVIGON, 1974). EG: ethylene
glycol.
rich chlorites with different oxidants
(Hz0 2 , bromide). We could check the
expulsion from the lattice of Fe and/
or Mg, depending on whether the
reactive solution was removed or not.
. TABLE 1
Spa~ings values (A) for the (001) reflection in < 2 J.trn fraction
Sample
OA
OA+EG
200°C+EG
28.84
28.75
27.20
28.11
31.30
30.76
13.3 31.3
22.6
OA, oriented aggregate; OA + EG, oriented aggregate treated with ethylene glycol; 200°C,
oriented aggregate heated at 200°C for one hour; 200°C+ EG, oriented aggregate treated with
ethylene glycol after heating at 200°C for one hour; 500°C, oriented aggregate heated at 500°C
for one hour. In the case of 0~+ EG the spacings values have been obtained by counting in a
scanning speed zero

v'
64 M. Rodriguez Gallego "
As a result of these attacks mixedlayer
structures developed.
Random mixed-layers
It is evident that these are highly
defective structures, whose growth
probably is controlled by:
1. Chemical composition;
2. Original structure (polytype);
3. Chemical environment.
Due to the aleatory character of
the defects and causes mentioned,
their variety can be practically infinite,
making their classification nearly
impossible.
Volume defects
Up to now, we have considered imperfections
related to elementary
structural units. The defects to be
considered in this section, deal with
several structural units from the
same material, or substance with
different chemical composition.
In the first case, we will review
grain boundaries and )n the second
one intergrowths,: lamellar precipitates,
and finally exsolutions.
The most frequent of the tridimensional
defects are grain boundaries
in polycrystalline materials.
They can be oriented or random. If
any symmetrical relationship (axial
or specular) between them exists, in
fact, a twin may be considered.
If the grain orientation is at ran~
dorn, the angles between grains, are
of outstanding importance. Their·
particular reactivity can make them
responsible for recrystallization and
sintering. In fact, they induce a characteristic
mobility of grain boundaries.
Such mobility seems conditioned
by grain orientation, in such
a way that when the angle between
the boundaries is small, the mobility
of the grain boundary i~ greater when
the degree of disorientation is lower.
Fig. 7- HRTEM photographies showing a low-angle grain boundaries in chlorite: a) a boundary
parallel to the crystal; b) low magnification view of an irregular boundary, 1, 2 and 3 crystals
with different orientation; c) a boundary nearly normal to the chlorite layer (from VEBLEN,
1983).

-.-
.
..
..
Crystalline Defects in Layer Silicates 65
boundaries with small angles between
grains of different nature, i.e.
chlorite-wonesite (Fig. 8). This latter
fact is discussed further in the next
section.
I ntergrowths
Fig. 8 - HRTEM photographies showing a lowangle
boundary between wonesite and chlorite
(from VEBLEN, 1983).
Recently, High Resolution Electron
Microscopy photographs (Fig. 7)
have shown that grain boundaries
are relatively frequent, at least in
chlorites (VEBLEN, 1983). The most
common being parallel to (001), but
not in micas where this angle is about
8°. Also, VEBLEN has observed grain
Intergrowths take place among
materials with similar chemical
characteristics and no necessary
lamellar habit. MARTIN VIVALDI &
LINARES GONZALEZ (1962) have
described a random intergrowth of
sepiolite and attapulgite.
Recently BUSECK & VEBLEN
(1981) described a talc-chloritelizardite
intergrowth (Fig. 9).
More striking are the intergrowths ··
among minerals with limited
structural similarities. The above
Tc
Chi
s
~
~-
~~-............... ~~ _....,.y.,
~ -~-~
¥-·~,.........---...~-~~ ..,, ..--~ ___.......,....... _____ ~~- ~- """'-" _
,..,__..- --
-~ ...
----.... _
.......,___ ~-- _, __
~-"--~-- ... ""- .. _.....,._ ,.,._~
""'~~...--~-..--,.--,.--~-
. -- __..._ --· - ~ - ~ -.--
,._,,.,__....,.. -....,... -- . " .. - .
--
- ~
~" ·- . -·--- - .'- - .. ... - --
.
-_.,.~ .-~
__ .. __ ~
~~ ---­
~~- ............_
- -=..~~ ..-.-.::..:=·:- V--::-:.:. : -' ..... - ~~ ~- :~ . <
-I'~ ,....--~--- ~ ,.,. + --- - _......,._._ -- --
. ~ ~
Fig. 9- HRTEM photography of a talc-chlorite-lizardite (serpentine) intergrowth (from BUSECK &
VEBLEN, 1981).

66
M. Rodriguez Gallego
mentioned authors, also described an
amphibole-talc intergrowth (Fig. 10).
However, it seems probable that such
an occurrence can be ascribed to
topotactic transformations. We have
found a diopside-saponite transformation
(unpublished) of this kind.
ILHIMA & ZHU (1982) have studied
the transformation muscovite-biotite
(Fig. 11) and incidentally, shown an
incipient chloritization of the latter.
Lamellar precipitates and exsolutions
Fig. 10 - HRTEM photography of an amphibole-talc
intergrowth (from BUSECK &
VEBLEN, 1981).
Such phenomena were postulated
many years ago: CAILLERE &
HENIN (1949) postulated interlamellar
precipitates of Fe and Mg hydroxides
in the chloritization process of
smectites. MARTIN VIVALDI & MAC
EWAN (1957) proposed analogous
processes, in order to explain the
Fig. 11 - HRTEM photography of a muscovite-biotite transformation. Inside a circle an incipient
chlorization of biotite is shown (from ILHIMA & ZHU, 1982).

Crystalline Defects in Layer Silicates 67
Fig. 12- HRTEM photographies of examples of microprecipitates lying in planes where biotite has
been altered to chlorite (from VEBLEN & FERRY, 1983).
-thermal and solvation behaviour of
swelling chlorites. Recently VEBLEN
& FERRY (1983) have described such
occurrences through HR TEM in the
alteration of biotite to chlorite (Fig.
12). BANOS et al. (1983) with the
same technique detected intercalations
of brucite layers between mica
layers (Fig. 13).
Exsolutions
Recently VEBLEN (1983) has
shown interesting pictures, by bright
field electron microscopy, of what
seems to be a talc-sodium-biotite
(wonesite) intergrowth (Fig. 14). It
may be pointed out that the intergrowth
does not take place along the
C 0 , but oblique to it, nearly along the
{269} or {135} planes. The fact that
such peculiarities were not related to
pores, fissures, etc. eliminates their
possible origin from weathering and
supports exsolution.
The existence of syngenetic talcmica
is a well known fact which supports
the hypothesis of an exsolution
mechanism, keeping in mind that an
immiscibility gap between talc and
sodium-biotite must exist. The peculiar
orientation observed must be due
to one of two possible causes:
1) Unmatching among the lattice
dimensions between talc and mica;
Fig. 13- HRTEM photography of the interlayering of a brucite-like sheet between mica layers (from
BANOS et al., 1983).

68 M. Rodriguez Gallego
Fig. 14 - Low-resolution, bright-field electron micrograph of lamellar microstructure in wonesite
(Talc: T) and Sodium Biotite (Na-Bi). Schematic diagram to show that lamellae are not parallel
to the structural layers. Solid circles represent interlayered alkali sites (from VEBLEN,
1983).
2) Kinetics of the process, where
migration parallel to the sodium
and potassium interlayers is much
easier than in the direction perpen-
Fig. 15- HRTEM photography showing a damage
by electron beam irradiation in 1M biotite
(from BANOS et al., 1983).
dicular to the layers.
Some of the above mentioned facts
are questionable. How many of these
phenomena are mere experimental
artifacts? Certainly the irradiation by
ions (in preparing thin sections of the
sample previous to examination) and
electrons (during observation) can induce
serious damage in the morphology
of the minerals studied (Fig. 15).
However, more positive conclusions
can be reached:
1) A critical review of the isomorphic
substitutions should be carried
out, since many of the mentioned
phenomena i.e. heterogeneities, impurities,
lamellar precipitates, etc.,
cast a shadow on the accepted chemical
composition of clay minerals;
2) In relation to the above mentioned
facts, the importance of X-ray
diffraction, and its ability to reach

Crystalline Defects in Layer- Silicates 69
the true chemical composition of the
minerals could be enhanced. Up to
now, it is the only available technique
that avoids many of the problems
mentioned;
3) «The last but not the least».
The possible correlation: mineral
imperfections-geological behaviour
of clays. Everyday new facts improve
our knowledge on the crystalline imperfections
as a result of geological
processes. During its complex history
the clay was not a mute and passive
witness. It only remains for us to decipher
information codified in the
form of mineral imperfections.
REFERENCES
BANOS J.O., AMOURIC M., DE FOUQUET C.H., BARONNET A., 1983. Interlayering and interlayer slip in
biotites as seen by HRTEM. Am. Miner. 68, 754-758.
BOLLMANN W., 1976. Crystal Defects and Crystalline Interfases. Springer-Vedag, Berlin.
BusECK P.R., VEBLEN D.R., 1981. Defects in minerals as observed with high resolution transmission
electron microscopy. Bull. Mineral. 104, 249-260.
CAILLERE S., HENIN S., 1949. Experimental formation of chlorites. Mineral. Mag. 28, 612-620.
EsouEVIN J., 1969. Influence de la composition chimique des illites sur leur cristallinite. Bull. Centre
Rech. Pau S.N.P.A. 3, 147-154.
FYFE C.A., THOMAS J.M., KLINOWSKI J., GOBBI G.C, 1983_ Magic-Angle-Spinning NMR (MAS-NMR)'
Spectroscopy and Structure ofZeolites. Angew. Chem. Int. Ed. Engl. 22, 259-275.
ILHIMA A.S., ZHU J., 1982. Electron microscopy of a muscovite-biotite interface. Am. Miner. 65,
1195-1205. ""
LASAGA A.C., 1980. Defect calculations in silicates: olivine. Am. Miner. 65, 1237-1248.
LEEMONS K.W., McATEE JR. J.L., 1983. The parameters of induced thermoluminescence of some
selected phyllosilicates: a crystal defect structure study. Am. Miner. 68, 915-923.
MARFUNIN A.S., 1979. Spectroscopy, Luminescence and Radiation Center in Minerals. Springer­
Ver!ag, New York
MARTIN RAMOS J .D., RODRIGUEZ GALLEGO M., 1980. Coexistencia de moscovitas 3T y 2M 1 en gneises de
la unidad de la Caldera (Cordilleia Betica). Estudios geol. 36, 201-204.
MARTIN RAMOS J .D., RODRIGUEZ GALLEGO M., 1982. Chromian mica from Sierra Nevada, Spain. Mineral.
Mag. 46, 269-272.
MARTIN VIVALDI J.L., MAC EwAN D.M.C., 1957. Triassic chlorites from the Jura and the Catalan Coastal
Range. Clay Miner. Bull. 3, 177'183.
MARTIN VIVALDI J .1., LINARES GONZALEZ J ., 1962_ A random intergrowth of sepiolite and attapulgite.
Clays Clay Miner. 9, 592-602.
NIETO-F., RoDRIGUEZ GALLEGO M_, 1981. Alteraci6n experimental de Cloritas_ Rev. Acad. Ciencias
Granada I, 108-124. ·
REYNOLDS R.C., HoWER J ., 1970. The nature of interlayering in mixed-layer illite-montmorillonite. Clays
Clay Miner. 18, 25-36.
RODRIGUEZ GALLE'GO M., MARTIN VIVALDI J.L., MARTIN POZAS J.M., 1964. Analisis cuantitativo de
filosilicatos de la arcilla por difraccion de ray os X. I IJ: I nfluencia de la sustituci6n isom6rfica y de
la cristalinidad. II Reuni6n Grupo Espaiiol Cristalografia Pura y Aplicada, Madrid, Octubre
1964, Abstract, pp. 17-18; 1969. An. R. Soc. esp. Fis. Quim. 65,25-29.
RODRIGUEZ GALLEGO M., ALIAS L.J., 1965. A regular mixed layer Mica-Beidellite. Clay Miner. Bull. 6,
119-123. .
RoDRIGUEZ GALLEGO M., 1968_ Una interestratificaci6n regular Mica-Beidellite. 11. An_ Ciencias Univ.
Murcia 16, 1-10.
RODRIGUEZ GALLEGO M., GARCIA-CERVIGON A., 1974. Interstratified minerals in ophites hydrothermally
alterated from NW Murcia province (Spain). 2eme Reun. Gr..Europ. Argiles, Strasbourg, Abstract,
p. 45.
SANZ J ., SERRATOSA J .M., 1984. Distinction of tetrahedrally and octahedrally coordinated Al in phyllosilicated
by NMR spectroscopy. Clay Minerals 19, 113-115.

70
M. Rodriguez Gallego
SMITH K.L., EGGLETON R.A., 1983. Botryoidal goethite: A transmission electron microscopy study.
Clays Clay Miner. 31, 392-396.
TcHOUBAR C., 1980. Determination des parametres d' ordre et aJsordre dans qiielques solids a structure
lamellaire (silicates, carbones). Bull. Mineral. 193, 404-418.
THOMPSON J .G., 1984. 29Si and 27 AI nuclear magnetic. resonance spectroscopy of 2:1 clay minerals. Clay
Minerals 19, 229-236.
VEBLEN D.R., 1983. Microstructures and mixed layering in intergrowth wonesite, chlorite, talc, biotite,
and kaolinite. Am. Miner. 68, 566-580. ·
VEBLEN D.R., FERRY J.M., 1983. A TEM study of the biotite-chlorite reaction and comparation with
petrologic observations. Am. Miner. 68, 1160-1168.

Miner. Petrogr. Acta
Vol. 29-A, pp. 71-83 (1985)
High-Resolution MAS-NMR Spectra of Layer Silicates.
Ordering of Tetrahedral Cations C*J ·
JOSE MARIA SERRATOSA
Instituto de Fisico-Quimica Mineral, C.S.I.C., Serrano 115 - dpdo., 28006 Madrid, Espaiia
ABSTRACT- High resolution 29 Si and 27 AI MAS-NMR spectra of layer silicates
has allowed a clear distinction between four and six coordinated AI and
identification of different environments of tetrahedrally coordinated Si. Chemical.
shifts of 29 Si and 27 Al signals depend on the nature of second neighbour
cations located in the tetrahedral and octahedral sheets and in the interlayer
space. Moreover, a quantitative analysis of the NMR components associated
to the different Si environments indicates that Si,Al distribution in the tetrahedral
sheet of phyllosilicates is mainly controlled by the electrostatic
requirement of homogeneous dispersion of charges. This requirement includes
as a partial aspect, the rule of Loewenstein which forbids the presence
of AI in contiguous tetrahedra.
Introduction
The general features of phyllosilicate
structures have been known for
many years, but there are certain
aspects concerning the distribution
of ions in the different structural sites
that have not been well established.
This distribution of isomorphous replacements
is an important crystallochemical
characteristic that controls
the stability of the structure and
the physico-chemical behaviour of
these minerals. However, its determination
by diffraction methods pr~sents
serious difficulties because iso-'
morphous replacements does not
necessarily follow a regular periodic
......
pattern. Moreover, in the case of the
analysis of ordering in tetrahedral
sites, the similarity of the atomic
scattering factors of Si and.Al, constitutes
an additional difficulty for the
determination of their distribution.
Spectroscopic methods provide
valuable information on these
structural aspects, since they permit
the identification of the different env;ironments
around certain ions forming
the silicate structures. For example,
the study of the infrared absorption
bands associated with structural
OH groups, and the analysis of 1 H and
19
F NMR signals, have allowed the
establishment of certain trends for
the cation distribution in the
octahedral sheet of micas
('') This general lecture is a summary of the results of recent studies by C.P. Herrero, J. Sanz and
J.M. Serratosa from the "Instituto de Fisico-Quimica Mineral", C.S.I.C., Madrid, Spain.

72
J.M. Serratosa
(RAUSELL-COLOM et al., 1979;
SANZ & STONE, 1983). Other examples
refer to the determination by
Mossbauer spectroscopy of the oxidation
state and location of iron in different
structural sites (tetrahedral and
M 1
and M 2
octahedral positions)
(SANZ et al., 1978). Recently, high resolution
MAS-NMR spectroscopy has
been applied to the analysis of several
aluminosilicate structures. This
technique permits a clear distinction
between 4- and 6-coordipated Al
(MULLER et al., 1981), as well as the
identification of different environments
of tetrahedrally coordinated Si
(LIPPMAA et al., 1980). Moreover, the
~---------analysis of the relative intensities of
the NMR components associated
with those Si environments, provides
useful information on the Si,Al distribution
in tetrahedral frameworks
(ENGELHARDT et al., 1981;
KLINOWSKl et al., 1982; FYFE et
al., 1983).
In the first part of this lecture we
will present the results of a systematic
study of well characterized phyllosilicates
by MAS-NMR spectroscopy.
Aluminium in tetrahedral and
octahedral sheets has been clearly
identified. Appropriate selection of
samples has allowed us to analyze
the influence of the nature of second
neighbour cations located in the
three different structural sites (tetrahedral,
octahedral and interlayer)
on the chemical shift of Si and Al nuclei
(SANZ & SERRATOSA, 1984). The
second part of this lecture is concerned
with Si, Al ordering in the tetrahedral
sheet. Several schemes of
Si,Al distribution have been considen~d-tanging
from--a random distribution
to models in which con~
straints imposed by crystallochemical
factors known to be operative in
this type of structure have been taken
into account. Comparison between
experimental and model-generated
Si NMR intensities has permitted us
to determine the model which gave
the best fit and consequently to determine
the factors which govern the
Si,Al distribution in phyllosilicates
(HERRERO et al., 1985a and b).
MAS-NMR spectra of phyllosilicates
27 Al MAS-NMR spectra.
27
Al MAS­
NMR spectra of phyllosilicates consist
of one or two principal components
and a series of side bands
associated with the spinning of the
samples (Fig. 1). According to previous
work (MULLER et al., 1981) the
central line at - 0 ppm must be
assigned to octahedral Al ions and
the line at- 70 ppm to tetrahedral Al
ions. These assignments are in agreement
with the structural compositions
of these samples. Thus,
pyrophyllite contains only Alocv
while muscovite has both Aloct and
Altet·
In principle, a quantitative determination
of the Altet/Aloct ratio seems
to be possible considering· the high
resolution of the spectra. However,
when we compared Altet/Aloct ratios
obtained from· NMR spectra and
from the mineralogical formulae, the
agreement was poor. In the case of

High-Resolution MAS-NMR Spectrao(Layer Silicates ... 73
Pyrophyllite
.Muscovite
100 0 -100 ppm 100 0 -100 ppm
Fig. 1 - 27 Al MAS-NMR spectra of pyrophyllite and muscovite recorded at 78.2 MHz, showirig the
lines corresponding to tetrahedral and octahedral Al. Chemical shifts are given from Al(H20)6 3 +.
muscovite, the NMR spectrum overestimates
the Altet content. The differences
observed must be .a conseq\.tence
of se'cond-order quadq~:tpolar
effects whose elimination in both signals
would require the use of higher
magnetic fields.
29Si MAS-NMR spectra. 29 Si MAS­
NMR spectra of the different species
of phyllosilicates are given in Figures
2 and 3. Talc and pyrophyllite have
only Si in the tetrahedral sheet, and
consequently all silicon ions have the
same tetrahedral environment, i.e.,
Pyrophyll i te ·
Talc
-60 -80 -100 -120
ppm
-60 -80 -100 -120
ppm
Fig. 2- 29 Si MAS-NMR spectra of pyrophyllite and talc, recorded at 59.6 MHz. Chemical shifts are
given from TMS ..

74 J.M. Serratosa
Phlogopite
1
Vermiculite
1
2
2
0
0
-60
-80
-100 -120
ppm
-60
-80
-100 -120
ppm
Muscovite
1
Margari te
3
0
-60
-80
-100 -120
pp m
-60
-80
-100 -120
pp m
Fig. 3 - 29 Si MAS-NMR spectra of phlogopite, vermiculite, muscovite and margarite recorded at
59.6 MHz. Chemical shifts are given from TMS. The number of AI around Si is indicated over each
peak.
Si surrounded by 3Si. The NMR spectra
of these samples show a single
component that appears at -97
ppm for talc and at -94 ppm for
pyrophyllite. The difference in chemical
shift between these samples, as
will be discussed later, is a consequence
of differences in composition
of the octahedral sheet.
In the micas phlogopite and
muscovite, approxima telyone{Ql,±_rt_b
of the Si in the tetrahedral sheet is
replaced by Al. For each composition,
all silicon atoms of the tetrahedral
sheet have the same second neighbours
in both the interlayer space
and the octahedral sheet. Therefore,
differences of environments for Si

High-Resolution MAS-NMR Spectfa-o(Layer Silicates ... 75
can be only a consequence of the Al,
Si distribution. There exist four
possible distinct environments for Si
within the tetrahedral sheet of micas,
i.e .., Si04 surrounded ·by 3Si04,
2Si04Al04, 1Si042Al04 and 3Al04.
By analogy to the case of zeolites
(KLiNOWSKI et al., 1982), they will
give signals with less negative values
for the chemical shift as the Al content
increases. The 29 Si MAS-NMR
spectra of these micas show three
well-resolved components at -91,
-86 and -82 ppm for phlogopite and
-89, -85 and -81 ppm for muscovite.
Considering that in these micas
the Si/Al ratios are near 3, the 3Al04
environment should have a very low
probability and consequently the
· observed lines should be assigned to
Si surrounded by 3Si, 2~i1Al and
1Si2Al, respectively. This assig~ment
agrees with the structural formulae
of the two samples. Thus, in the
phlogopite sample with a higher tetrahedral
Al content (Sh.84Alu6) than
that in muscovite (Si 3 .16Alo.s4), the
signal corresponding to the 1 Si2Al
environment has a higher relative intensity
than in the muscovite spectrum,
while the signal corresponding
to the Si(Si 3 ) environment follows
the reverse trend. :
In vermiculite with the same ideal
composition as phlogopite but in
which interlayer potassium has been
substituted by hydrated Mg ions, the,
spectrum shows also three lines that
appear at -92, -88 and -83.5 ppm.
The relative intensities of the three
lines are similar to those of phlogopites
as. one might expect from the
composition of the tetrahedral sheet
of vermiculite (Si 2 .89Al1. 11 ) which is
.close to that of phlogopite. Margarite
with a Si/Al near 1 shows a single line
at -73 ppm (Fig. 3), indicating the
existence of only one kind of environment
for the Si atoms. By its position
the line observed at -73 ppm in the
NMR spectrum should be assigned to
the Si(Ab) environment.
Influence of second neighbour cdtions
on the position of 29 Si and 27 Al
signals. The effect that second neighbour
cations located in different sites
of the structure, tetrahedral sheet,
octahedral sheet, and interlayer
space, exert on the chemical shift of
the Si and Al signals can be analyzed
separately by comparison of pairs of
samples with appropriate compositions.
The positions of Al and Si signals
for the samples analyzed in this
work are given in Table 1.
The influence of the nature of tetrahedral
cations on the Si and Altet
line positions has already been men­
. tioned in the case of phlogopite and
/muscovite. The several Si lines
observed in the mica spectra reflect
the different· tetrahedral environments
of this cation. The position of
these signals shifts by equal increments
toward less negative values as
the number of Al around Si increases.
On the contrary, the spectra show
only one Altet signal, indicating that
this cation has always the same tetrahedral
environment.
The second factor that influences
the position of the tetrahedral Si and
Al signals is the composition of the

76 J.M. Serratosa
TABLE 1
27 Al and 29 Si isotropic chemical shifts in ph~llosilicates *
Al signal
Si signal
mineral species Al,., Aloct Si(Si 3 ) Si(Si 2 Al) Si(SiAlz) Si(Al 3 )
pyrophyllite +1 -94
muscovite +67 +1.5 -89 -85 -81
margarite +71 +2 -73
talc -97
phlogopite PS +63.5 +6 -91 -86 -82
vermiculite +62.5 +5 -92 -88 -83.5
* Values are given in ppm from Al(H 2 0) 6
3 + and Me4Si, respectively
octahedral sheet. When we compared
samples having the same tetrahedral
and interlayer compositions (talcpyrophyllite,
phlogopite-muscovite),
it was observed that the.positions of
- ---- --------------equivalent tetrahedral Si and Allines
shift toward higher values when passing
from trioctahedral (three Mg) to
dioctahedral (two Al and one vacancy)
samples.
The effect of the nature of interlayer
cations on the line position is
ascertained by comparison of the Si
signal corresponding to the three Si
environment in samples with the
same octahedral composition. In
the pairs talc-phlogopite .and
pyrophyllite-muscovite the presence
of K+ as second neighbour shifts that
line to more positive values. A similar
shift is observed when interlayer
potassium is substituted by Ca 2 +
(margarite). For this mica, a single
line is observed a -73 ppm that corresponds
to -Si surrounded by 3A(
This value is more positive than the
value one would expect for the same
environment in muscovite, assuming
a constant shift for each Al incorporated
into the Si environment. The
same tendency is observed for the signal
of Altet when passing from muscovite
(67 ppm) to margarite (71 ppm).
With respect to the Aloe~ signal, it is
observed that its position is almost
-independent of the nature of interlayer
cations, which are too far to exert
a significant influence, and also of
the composition of the tetrahedral
sheet. Thus, in the dioctahedral phyllosilicates,
pyrophyllite, muscovite
and margarite, Aloct lines appear at
about the same value (1-2 ppm). On
the contrary, the composition of the
octahedral sheet modifies slightly the
position of the Aloct signal.- In trioctahedral
minerals that contain small
amounts of Al in the octahedral sheet
~ (phlogopite and vermiculite), each Al
ion must be surrounded by six Mg
ions and the Aloct line appears at S-6
ppm, a value which is higher than
those observed for dioctahedral
minerals where each Al ion is surrounded
by three Al and three vacancies.
In summary, the results show that
the line positions of tetrahedral Si
and Al depend on the nature of the
cations located as second neighbours

High-Resolution MAS-NMR Spectra of Layer Silicates ... 77
of these nuclei in the tetrahedral
sheet, the octahedral sheet and the
interlayer space. In the case of Alocv
the position of the NMR line seems to
depend only on the nature of cations
located as second neighbours in the
octahedral sheet.
Ordering of tetrahedral cations
(Si,Al)
The relative intensities of the different
components in the 29 Si NMR
spectra ofmicas are a consequence of
the Si,Al distribution for each particular
sample. In the case of margarite
(Si/Al= 1), the interpretation of
29Si NMR spectrum is straightforward.
The presence of a single NMR
component (-73 ppm) incj.icates the
existence of a unique envir~n~ent for
Si confirming the distribution model
found by X-ray diffraction analysis
(GUGGENHEIM & BAILEY, 1978),
i.e. strictly alternating Si and Al
occupying the tetrahedral sites.
For other micas and, in general, for
phyllosilicates with (Si/Al)tet ratios
smaller than 1 , the presence of several
components in the 29 Si NMR spectrum
is compatible in principle with
numerous Si,Al distribution patterns.
Information about the reliability
of a given model can be obtained
by two different approaches:
a) by the use of certain parameters
deduced from the NMR spectra th~t
give information about the nature of
first and second neighbouring.cations
of AI, and
b) by comparison -between the experimental
and model generated Si
NMR intensities.
Various distribution schemes have
been tested ranging from a random
distribution to models in which restrictions
of crystallographic or electrostatic
nature have been considered.
The restrictions which have
been introduced in successive steps
are: (i) avoidance of Al-0-Allinkages
(LOEWENSTEIN, 1954)· and (ii)
homogeneous dispersion of Al in
order to minimize the electrostatic
energy. For micas with Si/Al ratios
close to 3, this restriction implies also
local compensation of interlayer cations.
a) First approach - Informatiop a­
bout first neighbour cations of Al is
obtained by comparison of fractional
Al contents, x, calculated from the
structural formulae with those deduced
from the NMR spectra. x
values are calculated from the 29 Si
NMR spectra according to the expressions:
y 3Io + 2Il + I2
--------
for the random distribution and
Y
X
3 I
3
i=O
Il + 2I2 + 3I3
when the restriction of Loewenstein' s
rule is introduced. In these expressions
x and y are fractional contents of
Al and Si respectively and Ii are the
intensities of the components in the

78 J.M. Serratosa
29Si NMR spectra corresponding to
environments of Si with iAl. As
shown in Table 2, only the model in
which Loewenstein's restriction has
been introduced reproduces reasonably
well the x values deduced from
the structural formulae, thus confirming
the avoidance of Al in contiguous
tetrahedra. Small differences
observed in some cases are probably
a consequence of the uncertainty involved
in the method used to normalize
the analytical chemical data into
values of the structural formulae. The
fact that phyllosilicates comply with
the rule of Loewenstein allows a
quick and direct determination of tet-
----------~-----r_abeciral Sif!\!_rati~ f_!"Slll:l__ !!J.e 29 _Si
MAS-NMR spectra.
Information about second neighbour
cations of Al can be obtained
from the parameter P 2 :
Pz = -~I~ 2 ~+_3~I~ 3 _
I 1 + 2Iz + 3I3
which gives the probability that the
second neighbour of an Al be also an
Al. In this expression_II>h an,d_I 3 ar~.
the intensities of the components in
the experimental or simulated NMR
spectra corresponding to associations
of Si with 1, 2 or 3Al. I 2 + 3I3 is proportional
to the number of Al-Si-Al
associations and the denominator
takes into account the normalization
over the Al-Si-Si and Al-Si-Al triads.
Table 2 shows that P 2 values deduced
from experimental spectra are significantly
smaller that those calculated
from a random model in which
Loewenstein's rule has been introduced,
indicating that Al ions are, on
the average, more separated than
what is required by a model in which
the only restriction is the avoidance
of Al-0-Allinkages.
b) Second approach -A more complete
information on Si,Al distribution
is obtained by the second
approach in which all the experimental
intensities are compared
with those corresponding to the dif-
TABLE 2
Fractional AI contents (x) and probabilities (P 2 ) of the different models of Si, AI distribution
in the tetrahedral sheet of phyllosilicates. Values of x obtained from the structural formulae
and of P 2
obtained from the experimental 29 Si NMR spectra are given for comparison
Samples
Fractional Al Probabilities P 2
content x (ref. 10)
r. L.r. s.f. L.r. NMR
Natural(•)
Muscovite 0.28 0.22 0.21 0.28 0.14
Phlogopite 0.36 0.27 0.29 0.37 0.21
Vermiculite 0.38 0.28 0.28 0.39 0.27
Synthetic (b)
I 0.13 0.12 0.12 0.13 0.00
II 0.17 0.15 0.17 0.18 0.08
Ill 0.25 0.20 0.19 0.25 0.13
IV 0.35 0.26 0.27 0.35 0.23
(•) HERRERO et al. (1985a); (b) LIPSICAS et al. (1984);
r.: random distribution; L.r.: Loewenstein's restriction; s.f.: structural formula

High-Resolution MAS-NMR Spectri:OJf Layer Silicates ... 79
ferent considered models. Calculation
of the relative intensities of the. components
in the 29 Si NMR spectra can
be made directly from the AI and Si
fractional contents of each sample for
the random distribution model and
for the model in which the only restriction
is Loewenstein's rule. In
other cases, the models have been
simulated in a computer following a
Monte Carlo procedure.
I
For the random distribution model,
relative intensities of the components
in the 29 Si NMR spectra should
be reproduced by a statistical binomial
distribution. If x and y are respectively
the tetrahedral AI and Si
fractional contents, the calculated
probabilities for the four possible
environments of Si, i.e .. Si(3Si),
Si(2Si1Al), Si(1Si2Al) and ~i(3Al), are
respectively y 3 , 3y 2 x, 3yx 2 and x 3 •
Values obtained for this model "(Table
3) depart considerably from the experimental
ones, demonstrating that
a random distribution does not apply
to these minerals. From 1Jhe data of
Table 3 it is evident that in micas and
vermiculite, the environments 2Si1Al
and 1Si2Al are favoured at the expense
of the environment 3Si with regard
to a random distribution.
In the model in which the only restriction
is Loewenstein's rule, the two
possible associations of contiguous
tetrahedra are Si-0-Al and Si-O~Si.
Thus, if x and y are again the tetrahedral
AI and Si fractional contents,
the probability for Si-0-Al asso-·
dation will be 2x because the probability
for AI is x and the neighbour of
an AI is always a Si; consequently,
the probability for Si-0-Si will be
1-2x. If now, we restrict our analysis
to cases in which the first tetrahedron
in the pair contains Si, then
the normalised probabilities for Si-0-
Al and Si-0-Allinkages will be:
Psi-O-Al = x/[x + (1 - 2x)] = x/y = a
Psi-o-s; = (1 - 2x)/y = 1-x/y = s
On this basis, the probabilities of
the four possible environments of Si
will be given by the terms ofthe binomial
distribution:
The corresponding calculated intensities
for the phyllosilicate samples,
are given in Table 3.1t is evident
that the restriction of Loewenstein's
rule improves appreciably the fitting
between experimental and modelgenerated
intensities. However, there
are significant differences indicating
the existence of other factors, in addition
to this rule, which impose additional
restrictions for the Si,Al distribution
in the tetrahedral sheet of
these minerals. In particular, it is evident
that experimental intensities do
not follow a binomial distribution
and that in the tetrahedral sheet of
micas, the environment Si(2Si1Al) is
clearly favoured.
When the condition of homogeneous
dispersion of charges is
introduced, the intensities of the
components in the 29 Si NMR spectra
are calculated from models simulated
in a computer following a
Monte Carlo procedure as described

I
. TABLE 3 I
Experimental and calculated probabilities of the four possible environments of Si in the tetrahedral sheet of phyllosilicates for different Si, AI
distribution model~
Muscovite Phlogopite Vermiculite
Distribution
model'' 3Al 1 Si2Al 2Si1Al 3Si 3Al 1Si2Al 2Si1Al : 3Si 3Al 1Si2Al 2Si1Al 3Si
l
Random 1.0 11.1 40.0 47.9 1.9 15.5 42.9 :39.7 2.1 16.7 43.4 37.8
Loewenstein's restriction 2.2 16.7 43.5 37.5 4.7 24.9 44.2 !26.2 5.6 27.2 43.7 23.5
Homogeneous dispersion of 0.3 12.1 58.2 29.4 0.7 24.8 56.5 !18.0 0.8 29.5 53.1 16.6
charges I
Experimental''* 11.8 60.2 28.0 2D 62.1 :14.8 -,- 30.5 54.0 15.5
I (x=0.115) II (x=0.15) Ill (x=0.20) IV (x=0.26)
Distribution
model* 3Al 1Si2Al 2Si1Al 3Si 3Al 1Si2Al 2Si1Al 3Si 3Al 1Si2Al 2Si1Al 3Si 3Al 1Si2Al 2Si1Al 3Si
Random 0.2 3.5 27.0 69.3 0.3 5.7 32.6 61.4 0.8 9,6 38.4 51.2 1.8 15.0 42.7 : 40.5
Loewenstein's restriction 0.2 4.4 29.5 65.9 0.5 7.7 35.9 56.9 1.5 14.1 42.2 42.2 4.3 24.0 44.4 . 27.3
Homogeneous dispersion of 39.0 61.0 3.0 46.6 50.4 0.2 8.1 58.2 33.5 0.7 23.6 56.2 19.5
charges
Experimental** 39 61 - 4 44 52 10 55 35 24 57 19
'' Each model includes the restrictions of the preceeding schemes; ** Values from LIPSICAS et al. (1984)
00
0
:--.
~
(/)
"'
~
0
"' !:>
I
I
I
I
I
I
I
Natural samples)
Synthetic samples

High-Resolution MAS-NMR Spectra of Layer Silicates ... 81
by HERRERO et al. (1985a and b).
The condition of homogeneous dispersion
of Al is introduced by imposing
that the number of Al ions per
hexagonal ring should be as close as
possible to the average value corresponding
to each composition. Two
cases are considered:
a) For compositions 1!3

82
J.M. Serratosa
analysis of the data in this table, it is
evident that Loewenstein's restriction
improves only slightly the fitting
of the spectra, while when the condition
of homogeneous dispersion of Al
is introduced in the simulated models,
a significant drop in S values is
achieved. Also the fitting of experimental
P 2 values, a parameter
which reflects a partial aspect of Al
distribution, is considerably improved
for the simulated models
complying with the criterion of
homogeneous dispersion of Al.
The result of this analysis shows
that tetrahedral cation distribution is
mainly controlled by a requirement
-- ___________ oL ___ homogeneous ___ disper:_sion of
charges in order to minimize the electrostatic
energy. This requirement includes
Loewenstein's principle as a
partial aspect, with respect to which
it can be considered as an extension
in the sense that it conditions the Al
substitution in tetrahedral sites
beyond the first nearest neighbour.
Finally, it seems also clear from this
analysis, that the factors found to be
operative in Si,Al distribution do not
necessarily require that this distribution
follows a regular pattern. This
conclusiQIJ. ___ ~i!g:ree!§ with those
·obtained by diffraction methods
according to which there are only a
few cases giving clear evidences of
long range order (BAILEY, 1984).
Conclusions
The information obtained from the
29Si and 27 Al MAS-NMR spectra can
be summarized as follows:
1) Distinguish tetrahedral from
octahedral Al.
2) Quantitatively determine Si/Al ·
tetrahedral ratios.
3) Identify four different environments
of Si: Si(nAl), n = 0 to 3.
4) Confirm the avoidance of Al-0-
Al linkages; tetrahedral Al is always
surrounded by 3Si (Loewenstein's
rule).
5) Prove that tetrahedral Al is
homogeneously dispersed and longrange
disordered (meta/para - 2).
For Si/Al - 3 (common micas) hexagonal
rings contain 1 or-2 Al implying
a local balance of interlayer
K+.
REFERENCES
BAILEY S.W., 1984. Review of cation ordering in micas. Clays Clay Miner. 32, 81-92.
ENGELHARDT V.G., LOHSE U ., LIPPMAA E., TORMAK M., MAGI M., 1981. 29 Si-NMR-Untersuchungen zur
Verteilung der Silicium-und Aluminiumatome in Alumosilicatgitter von Zeolithen mit Faujasit­
Struktur. Z. Anorg. Allg. Chem. 482, 49-64.
FYFE C.A., THOMAS J.M., KLINOWSKI J., GOBBI G.G., 1983. Magic-Angle-Spinning NMR (MAS-NMR)
Spectroscopy and the Structure of Zeolites. Angew. Chem. Int. Ed. Engl. 22, 259-275.
GUGGENHEIM S., BAILEY S.W., 1978. Refinement of the margarite structure in subgroup symmetry:
correction, further refinemen,t and comments. Am. Miner. 63, 186-187.
HERRERO C.P ., SANZ J ., SERRATOSA J .M., 1985a. Si, AI distribution in micas: analysis by high resolution
29Si NMR spectroscopy. J. Phys. C.: Solid State Phys. 18, 13-22.
HERRERO C.P., SANZ J., SERRATOSA J.M., 1985b. Tetrahedral cation ordering in layer silicates by 29 Si
NMR spectroscopy. Solid State Comm. S3, 151-154.

High-Resolution MAS-NMR Spectriio(Layer Silicates ... 83
KLINOWSKI J., RAMDAS S., THOMAS J.M., FYFE C.A., HARTMAN J.S., 1982. A Re-examination of Si, AI
Ordering in Zeolites NaX. and NaY. J. Chem. Soc. Faraday Trans. 78 (II), 1025-1050.
LIPPMAA E, MXGI M., SAMOSON A., ENGELHARDT G., GRIMMER A.R., 1980. Structural Studies of Silicates
by Solid-State High-Resolution 29 Si NMR. J. Am. Chem. Soc. 102, 4889-4893.
LIPSICAS M., RAYTHATHA R.H., PINNAVAIA T.J., JOHNSON I.D., GIESE R.F. Jr., COSTANZO P.M., ROBERT
J.L., 1984. Silicon and aluminium site distribution in 2:1 layered clays. Nature 309, 604-607.
LOEWENSTEIN W., 1954. The distribution of aluminium in the tetrahedra of silicates and aluminates.
Am. Miner. 39, 92-96.
MDLLER D., GESSNER W., BEHRENS H.J ., ScHELER G., 1981. Determination of the aluminium coordination
in aluminium-oxygen compounds by solid-state high resolution 27 Al NMR. Chem. Phys. Lett.
79, 59-62.
RAUSELL-COLOM J .A., SANZ J ., FERNANDEZ M., SERRATOSA.J .M., 1979. Distribution of octahedral ions in
phlogopites and biotites. Pp. 27-36, in: Proc. 6th Int. Clay Conf. 1978, Oxford (M.M. Mortland
and V.C. Farmer, editors), Developments in Sedimentology 27.
SANZ J ., SERRATOSA J .M., 1984. 29 Si and 27 AI High-Resolution MAS-NMR Spectra of Phyl/osilicates. J.
Am. Chem. Soc. 106, 4790-4793.
SAN~ J., StoNE W.E., 1983. NMR study of minerals. Ill. The distribution of Mg2+ and Fe 2 + around the
OH groups in micas. J. Phys. C.: Solid State Phys. 16, 1271-1281.
SANZ J., MEYERS J., V!ELVOYE L., STONE W.E.E., 1978. The location and content of iron in natural
biotites and phlogopites: A comparison of several methods. Clay Minerals 13, 45-52.

Miner. Petrogr. Acta
Vol. 29-A, pp. 85-100 (1985)
The Upper Basin of the Ofanto River: Some Grain Size,
Mineralogical and Chemical Factors which Show the
Sedimentation Pattern and Mineral Source
LUIGI DELL'ANNA
Dipartimento Geomineralogico dell'Universita di Bari, Campus, Via G. Salvemini, 70124 Bari, Italia
This general lecture, delivered by L. Dell'Anna, was prepared by F. Balenzano, L. Dell'Anna, M. Di
Pierro and M. Moresi. -
ABSTRACT- Through a study of 220 samples coming from deposits of the
Lower-Middle Pliocene basin in the Valley of the Ofanto River (southern
Italy), it has been possible to point out that the sedimentation took place in
shallow sea-water which tends to deepen during deposition of the middle
part of the pelitic sequence examined. The clastic material is made up mainly
by clay minerals (illite, smectite, chlorite, kaolinite and rare mixed-layer
illite-smectite), muscovite, quartz, feldspars, calcite and dolomite originating
from the Irpinian Units and the so called «argille varicolori». Material
from the «(irgille varicolori» has been found chiefly in the central part of
the basin, whereas material from the Irpinian Units involved mainly the
Campania areas nearS. Angelo dei Lombardi, Lioni, Calitri and S. Andrea di
Conza. The textural and compositional trends and factors found are common
to other Lower-Middle Pliocene basins in southern Italy.
Introduction
The sediments examined are to be
found in rather extensive deposits
along the Ofapto River Valley from
Mt. Vulture to Ariano Irpino, within
the districts of Ruvo del Monte,
Rapo_ne, Calitri, Conza della Campa~
nia, Teora,, Lioni, Morra de Sanctis, S. '
Angelo dei Lombardi and Guardia
Lonibardi, in Campania (southern
Italy). The deposits cover an area of
approx 200 km 2 ; they are locally
several meters deep and date from
the Lower-Middle Pliocene. They witness
a foredeep sedimentary marine
basin (Fig. 1) which developed during
the Lower-Middle Pliocene, after the
Apulo-Gargano foreland subsided
and the Apennine chain arose. The
deposits were originally more exten­
.sive and in a different position, because
the Middle Pliocene tectonic
This research was carried out with the financial support of the Ministry of Public Education of
Italy (M.P.I. 40%). -

86 L. Dell'Anna
2
~
3
~
E5::53
6
lilllliilil
Fig. i - Geologic map of Ofanto River Valley (Campania Region, southern Italy). 1: Carbonate
platform Units (Upper Triassic-Lower Miocene); 2:

The Upper Basin of the Ofant6-Rive~ ... 87
coming from several outcrops of the
Ofanto River Valley showed a grainsize
and compositional behaviour in
accordance with the stratigraphic
and topographic position of the different
parts of the pelitic sequence.
Comparable behaviour has been
found also in other sediments of
southern Italy. This lecture attempts
to show the grain-size and compositional
features which have been
found in relation to their geologic significance.
Grain size and compositional data
reported in the following work were
used: DI PIERRO & MORES! (1982;
1984), DELL'ANNA & LAVIANO
(1982), BALENZANO & DE MARCO
(1984), BALENZANO (1984). They
also supplied detailed data of the various
areas of the basin, the analytical
methods, the location of samples
considered and the detailed geologic
setting of the Ofanto River Valley.
The present lecture aims at showing
the help which clay mineralogy
•% ~
30
20
10
a)
b)
E 'd" CO
_ "' I
.,. .,.
V
E
:>_
M
"' A
Fig_ 2 - Grain size composition of pelitic sequence from sediments of the Ofanto River Valley. a)
Average size frequency distribution (with graphic representation of ascertained maxima) with b)
range from maximum for each grain size grade; c) Average clay (63!lm) frequency distribution with d) range from maximum to minimum; e) Triangular diagram
showing the size distribution of the samples (n = 220) in form of sand-silt-clay percentages (after
- SHEPARD, 1954).
Sand
ilt

88
lends to geology and also the importance
of some analyses, such· as
the quantitative analysis of clay
minerals. Results from this analysis,
when they are reproducible, are scientifically
valid in spite of their being
occasionally inexact.
Grain size
L. Dell'Anna
The fine-grained sediments of the
Ofanto River Valley consist almost
exclusively of materials ranging from
63J.!m size grade; while the
positive correlations between the size
grades 2-4Jlm, 4-8J.1m and 8-16J.1m and
the negative correlation between the
size grades 8-l6J.1m and 32-63J.1m have
made it possible to determine the
other maximum in the 8-32J.1m grain
size grade. From the frequency distribution
(Fig. 2) and the correlations
which have .. beenfound (Jal:>kl),
three grain size grades of the clastic
materials can be pointed out: clay
(

fi"Ff' _ =•···"' ~o>hAAUA%» ->

90 L. Dell'Anna
40
%
30
a)
N
N
20
10
"' "
+
ea
+
c)
i
max.
med.
min.
0 0
N N
"" "'
Fig. 3 - Compositional characteristics of pelitic sequence from sediments of the Ofanto River
Valley. a) Average mineralogical distribution with b) range from minimum to maximum for each
mineral; c) Average chemical distribution with d) range from minimum to maximum for each
oxide. S: smectite; I + Mu: illite + muscovite; K: kao!inite; Ch: chlorite; Q: quartz; F: feldspars;
Ca: calcite; Do: dolomite.
groups can be pointed out through
the relationship between the main
minerals and the three grain size
grades above identified (Table 2). S
and K are positively correlated; to the
clay size grade; I and Ch to the silt
size grade; Q, F, Ca and Do to the
sand grade. Thus, concerning the
sedimentation behaviour, S and K
are connected to the clayey contribution,
I and Ch to the silty contribution,
Q, F, Ca and Do to the sandy
contribution; K is also connected to
the silty contribution. This relationship
was confirmed by the results
of a mineralogical analysis carried
out on the clay-silt-sand grain size
grades of the samples from deposits
of Cairano and Conza della Campania
(Table 3).
The chemical behaviour and the
statistical Table of the chemical data

.
TABLE 2
Relationships between main minerals and between each mineral and clay, silt, and sand grain size grades
s a = -0.0161 0.0584 -0.0540 -0.3889 -0.3790 -0.1564 -0.0564
x = 22% b = 21.3835 2.5225 8.3749 24.4891 16.1261 21.7509 5.0117
r = -0.0293 0.3256 -0.2735 -0.7086 -0.7103 -0.4054 -0.3552
I+ Mu a = 0.1504 0.1491 -0.4992 -0.2361 -0.3733 -0.1214
x = 21% b = 0.6653 4.0345 26.2896 12.6180 26.1031 6.3017
r = 0.4620 0.4159 -0.5008 -0.2437 -0.5329 -0.4205
K a = 0.3880 -1.4124 -1.7180 -1.0620 -0.4661
x = 4% b = 5.6831 21.2010 14.2298 22.3193 5.5340
r = 0.3524 -0.4613 -0.5772 -0.4935 -0.5258
~
Ch a = -0.2064 -0.1803 -0.5313 ~0.1445
x "'
= 7% b = 17.2748 8.9469 22.0627 4.7862 ~
'"

92 L. Dell'Anna
TABLE 3
Average mineralogical composition of clay, silt, and sand grain size grades from samples of
Cairano and Conza della Campania (DELL'ANNA~&TA:VIAN0T~t982) -~
% clay
smectite 49
I+ Mu 28
kaolinite 6
chlorite 5
quartz 4
feldspars 1
calcite 7
dolomite
I + Mu: illite + muscovite
support the observation related
above. Besides the carbonate components
and very small amounts of
Ti02, P 2 0s, CaO, MnO and Na20, the
main oxides are Si02, Alz03, H20+,
--~-~~-~- --~Fe-z03;KzO~and--MgO-,--with SiOz prevailing
over all, Alz03 quite abundant,
and all the others represented
by small quantities (Fig. 3). Si02 is
negatively correlated to all the other
· main oxides, and this agrees with the
reasonable amount of quartz. The
positive correlation between almost
all the possible couples which can be
formed from Alz03, H20+, Fe203, KzO
and MgO is in agreement with the
presence of clay minerals. The positive
correlation (Table 4) SiOz-sand
appears to be due to a large amount
of quartz in this size grade, while the
positive correlation between the
amount of each main oxide (Alz03,
Fe20 3, MgO, K20 and H20+) and the
amounts of clay and silt respectively
appear to be related to the almost
exclusive presence of clay minerals in
these two size grades. The positive
correlations between Alz03 and Fez03
and between each of these two oxides
and H20+ seem to support the pressilt
sand
17
26 17
6
9 5
13 24
6 25
20 25
3 4
ence of Fe-Al hydroxides in agreement
whit the results of X-ray analysis.
Origins
The proximity to the source shown
by the texture, and the scarce diagenesis
pointed out by mineralogy
indicate parent rock with lithofacies
consistent with the compositional
characteristics of the sediments of
the basin. The references (BOENZI et
al., 1968; OGNIBEN, 1969; HIEKE
MERLIN et al., 1971; PIERI &
WALSH, 1973; MAGGIORE &
WALSH, 1975; HUERTAS et al.,
1977; PESCATORE, 1978; PESCA­
TORE et al., 1980; LOJACONO, 1981;
1983; ORTOLANI & TORRE, 1981;
DI PIERRO & MORESI, 1982) suggest
that the source-rock of the Ofanto
Valley sediments could be found in
the Irpinian Units, as the «Serra
Palazzo Formation>>, «Castelvetere
Flysch» and «Gorgoglione Flysch».
The arenaceous and/or silty or/and
pelitic series of these units, which are
chiefly composed of quartz, feld-

TABLE 4
Relationships between main oxides and between each oxide and clay, silt, and sand grain size grades
Si0 2 a = -0.3309 -0.1988 -0.0807 -0.2692 -0.3545
x = 65.0% b = 38.6624 17.7744 7.6202 4.7958 27.9983
r = -0.8068 -0.6867 -0.7182 -0.4505 -0.8251
Al 2 0 3 a = 0.2838 0.1767 0.0769 0.4298
x = 17.2% b = -0.0106 -0.6532 1.7249 -2.4077
r = 0.4030 0.6485 0.5293 0.4111
Fez03 a = 0.1158 0.0053 0.8810
x = 4.9% b = 1.8181 3.0207 0.6873
r = 0.2993 0.0259 0.5935 ~
"'
MgO a = 0.2254 1.9611 ~
/ ~
x = 2.4% b = 2.5101 0.3015
"' ....
r = 0.4224 0.5113 bl
!'>
K 2 0 a = 1.5485 "' s·
x = 3.1% b = 0.2541 ~
r = 0.2154 s.
"'
HzO ~
~'>•
x = 5.0%
;:l•
0:
!:J:j
Si0 2 Al 203 Fe 203 MgO K 2 0 H 2 0
~·
CLAY a - -0.1044 0.0454 0.0225 0.0079 0.0027 0.0325
x = 39.1% b = 54.1330 11.4670 0.8720 1.5251 2.2399 2.5600
r = -0.4311 0.5260 0.4284 0.4115 0.2171 0.4468
SILT a = -0.0280 0.0155 0.0199 0.0086 0.0034 0.0335
x = 48.0% b = 51.4018 12.4947 2.7930 1.4227 2.1803 2.2180
r = -0.0910 0.1413 0.2985 0.3501 0.2170 0.3626
SAND a = 0.1115 -0.0500 -0.0319 -0.0121 -0.0044 -0.0487
x = 12.9% b = 48.6192 13.8845 4.1633 1.9911 2.4027 4.4981
r = 0.4834 -0.6083 -0.6367 -0.6572 -0.3707 -0.7009
Symbols as in Table 1
\0
w

'£.
TABLE 5
Compositional characteristics of samples from Calitri, Gor~oglione Flysch and «argille varicolori»
whole sample
I
Gorgoglione Gorgoglione «argille varicolori» (2)
Calitri (1) Flysch (1) Calitrii (1) Flysch (1)
clay minerals 49 51 Si0 2 51.0 50.9 smectite
quartz 18 19 Al 2 0 3 13.1' 15.1 I+ Mu
feldspars 10 10 Fe 2 03 3.4 5.0 kaolinite
calcite 19 18 M gO 2.9 2.6 chlorite
dolomite 4 2 CaO 12.1 9.1 quartz
clay fraction
Na 2 0 1.1 1.3 feldspars
smectite 58 18
illite 29 61 K 2 0 2.3 3.0 calcite
K+ Ch 13 13
other 8 H 2 0 + C0 2 13.5 12.4 dolomite
(1) from Dl PIERRO & MORESI (1982); (2) from ABBATICCHIO et al. (1981) and Dl PIERRO & MORESI (1986).
I + Mu: illite + muscovite; K + Ch: kaolinite + chlorite; tr: traces
60
12
13
6
5
2
2
tr
!:"""'
tl
:::::::
"'
;..:
;;
;;
~

The Upper Basin of the Ofa·ntoRiver ... 95
spars, muscovite, carbonates in
coarse size grade, and of clay minerals
(illite, smectite, chlorite and
kaolinite) in fine size grade, seem to
be the probable parent rocks. On the
other hand the compositional characteristics
of the pelitic sediments from
the «Gorgoglione Flysch» of the lrpinian
Units compared with those from
Calitri and S. Andrea di Conza of the
Ofanto basin (DI PIERRO & MORE­
SI, 1982) (Table 5), seem to support
this supposition. However, the pelitic
sediments from the Ofanto River Valley
which have been found (Table 5)
(DI PIERRO & MORES!, 1982), in
comparison with those from the Irpinian
Units, richer in smectite and
poorer in Ab03, Fe203 and K20, indi­
.cate the presence of clastic material
from rich-smectite pelitic sources, as
is to be found in the pelitic mernl?ers
of «argille varicolori>> (BELVISO et
al., 1977; AMICARELLI et al., 1977;
ABBATICCHIO et al., 1981). DI PIER­
RO & MORES!, 1985). This clastic
contribution seems to account for the
presence of Fe-Al hydroxides from
«argille varicolori» and also to explain
the large grain size range of
some minerals, such as K (Table 2),
whose presence is consistent both
with the detrital material from the
Irpinian basin and with that from
« argille varicolori ».
Such hypotheses agree with the re-\
gional geology. As a matter of fact the
Campania-Lucania carbonate platform,
the Lagonegro basin, the
Abruzzo-Campania carbonate platform
and the Molisano basin, which
made up the southern paleo-
Apennine, since the Lower Miocene
changed their original paleogeographic
setting because of various
tectonic events (ORTOLANI & TOR­
RE, 1981). Thus, during the Lower
Miocene in the Apennine area, which
at present includes the Ofanto Valley,
the Campania-Lucania platform
broke up and the «argille varicolori»
overthrust the broken-up platform
deposits and part of the Lagonegro
basin. A new sedimentary basin, the
Irpinian basin, set in on the overthrust
and the undeformed
Lagonegro Units; during successive
Miocenic and Lower Pliocenic events
the units of this basin shifted to their
present position. The successive
marine invasion over the eastern
Apennines gave rise to various
sedimentary basins and also the
basin of the Ofanto River Valley.
Therefore, because of their
paleogeographic and tectonicstratigraphy,
the Irpinian Units and
the

96 L. Dell'Anna
basin development and the distribution
trends of the minerals. However;
by using the statistical table bf data
from the grain size, mineralogical
and chemical analyses of samples
taken in series from the pelitic sequence,
and by detailed field observations
it was possible to place most
of the sample (n = 195) in an adequate
stratigraphic position. Thus, the
correct stratigraphic position of the
samples made it possible also to recognize
some grain size, mineralogical
and chemical trends (Fig. 4) and to
distinguish the bottom part, which
settled during marine invasion, from
the top one, which settled during the
-------retreat of the sea, and both from the
middle part of the pelitic sequence of
the Ofantosediments.'I'he grain size,
mineralogical and chemical characteristics
distinguishing the middle
part from the bottom and the top
ones are more sharply outlined than
those which distinguish the bottom
and the top parts. However, the middle
samples (n = 91) are richer (Table
6) in clay, smectite and Fe203, and
po~rer in sand, quartz and SiOz,
when compared to the other samples
(Student's t-test indicates statistical
significance P 2:99.9%). The bottom
samples (n = 43) contain more
sand than the top samples (n = 61)
and less clay, smectite, and Fe203
(Student's t-test indicates P 2:99.9%).
Sand 50
Silt
%
16
":>.
M
"'
'Ill ill~'
N b)
'
M
,
:;-_
0 0 15 63 I'-m
3,0 %
_§bottom
~middle
OJIIlll top
-
50
-
'if-=-
)f
/.I
~ ,;
80
0
~
Al203.
50
Fig. 4 - Grain size, mineralogical and chemical trends in three parts of pelitic sequence from
sediments of the Ofanto River Valley. a) sand-silt-clay, c) smectite-feldspars-quartz, d) Si02-Al20 3-
Fe203 trends and b) diagram of32-63flm size grade against >63flm one of samples from bottom,
middle and top parts of pelitic sequence. S: smectite; F: feldspars; Q:.quartz.
Fe 2 o 3
20
Al203

TABLE 6
Main .grain size, mineralogical and chemical characteristics distinguishing samples from three parts of the pelitic sequence
Parts Thickness Nomenclature after Clay Silt /Sand 63~m/ s Q c~i0 2 Al203
m SHEPARD (1954) 32-63~m
top -30 silty clay to sandy 38.1 46.4 15.5 2.0 21 17 66.2 17.3
(n = 61) clayey silt
middle -120 silty clay to clayey 45.0 51.3 3.7 0.6 34 13 63.3 17.5
(n = 91) silt
bottom -so silty clay to silty 32.5 49.3 18.2 3.6 17 18 66.3 16.9
(n = 43) sand
In parentheses number of samples from several parts; other numbers represent average values; symbols as in Table 2
Fe203
4.7
5.4
4.3
S;l
"'
~
,'

98 L. Dell'Anna
The behaviour of clay, smectite
and sand suggests a deepening of the
sedimentary basin during the settling
of the middle part of the pelitic sequence
and indicates that during
the sedimentation of the bottom part
the sea-water was more shallow than
that of the top part. The increase of
clay and smectite could have been
caused not only by deepening but
.also by the contribution of material
from >
found in the middle part of the pelitic
sequence outcropping in the area of
Calitri.
Concerning the areal distribution
of the main minerals in the middle
part, which is the most clearly recognizable
by grain size, mineralogical
and chemical characteristics, the following
areas were noted (Fig. 5): an
area located in the central part of the
present basin showing the highest
amountsofclay-minerals (C.m.)and
S associated with the lowest amounts
of Q + F and carbonates (C. a.); two
areas, one spreading from S. Angelo
dei Lombardi to Lioni, and the other
from Calitri to S. Andrea di Conza,
which show the lowest amount of C.
m. and S associated with the highest
amounts of Q + F and medium
amounts of C. a.; finally, three other
areas, the first SW of S. Angelo dei
Lombardi, the second spreading from
Guardia Lombardi to Teora, and the
third located E of Calitri, in which
the main minerals are present in
medium amounts. Therefore, the
seem to be the
chief parent rocks of the central part,
while the Irpinian Units contributed
to the other. two areas; the clastic
sediments of the last three areas seem
to come equally from the two sourceunits.
If these hypotheses are true, the
paleogeographic disposition of the
pre-Pliocenic units surrounding the
basin during sedimentation was not
ITIIIIIIl > 65% 25% > 5.0 < 15% < 20%
~
m; 55-65% 25% 3.0-4.5 16 - 20% 20 - 25%
20% 20 - 25%
0 10 15km
Fig. 5 - Main minerals pattern in middle part of pelitic sequence from sediments of the Ofanto
River Valley. C.m.: clay minerals; S: smectite; Q + F: quartz+ feldspars; C.a.: carbonates.

The Upper Basin of the OfantoRi1Jer ... 99
very different from the present one
(Fig. 1).
Conclusions
The grain size and mineralogical
trends found make it possible to
point out that:
a) the pelitic sequence sedimentation
of the Lower-Middle Pliocene
basin of the upper Ofanto River Valley
took place in shallow sea-water
with a deepening during the deposition
of the middle part;
b) the grain size and compositional
characteristics of the clastic material
indicate three main grain size contributions:
clay rich in $ and K, silt
rich in I (with Mu) and Ch, and finally
sand rich in Ca, Do, Q :;tnd F;
c) the source-areas are two: the
Irpinian Units and the «argille varicolori>>.
The former provided m\inly
clay minerals (I + Mu and subordinately
S, Ch and K) as well as Q, F, Ca
and Do, the latter mainly smectiterich
clay minerals and Fe-Al hydroxides;
d) the clastic material from «argille
varicolori» became more abundant
starting from the beginning of
the middle part sedimentation of the
pelitic sequence and was deposited
with more abundance in the central
part of the basin;
e) the clastic material from the
Irpinian Units prevailed in the areas
located nearS. Angelo dei Lombardi,
Lioni, Calitri and S. Andrea di Conza;
f) both types of clastic material are
equally abundant in the areas located
SW of S. Angelo dei Lombardi, near
Guardia Lombardi and Teora, and
finally E of Calitri.
The evidence collected from the
studies being carried out suggests
that much of the grain-size, chemical
and mineralogical behaviour found
in the upper Ofanto Valley basin is
common to other Lower-Middle
Pliocenic sediments of the southern
Apennines.
REFERENCES
ABBATICCHIO P., AMICAREiir V., DELL'ANNA L., Dr PIERRO M., 1981. Argille varicolori della zona di
Stigliano (MT): indagini mineralogiche, chimiche e granulometriche. Rend. Soc. It. Min. Petr. 37,
195-211. '
AMICARELLIV., DELL'ANNA L., Dr PIERRO M., GUERRICCHIO A., MELIDORO G., PETRELLA M., 1971.Alcuni
dati sulla composizione chimico-mineralogica e sui caratteri geotecnici delle argille varicolori dellli
Calabria. Atti 2° Congr. Naz. sulle Argille 1976, Bari, Geol. Appl. Idrogeol. 12, 429-451.
BALENZANO F., 1984. Caratteri granulometrici, mineralogici e chimici ed aspetti paleoambientali delle
«Argille azzurre» di S. Angelo dei Lombardi, Morra de Sanctis, Teora e Lioni (AV). Geol. Appl.
Idrogeol. (in press).
BALENZANO F., DE MARCO A., 1984. Caratteri granulometrici, mineralogici e chimici e aspetti paleoambientali
delle «Argille azzurre» di Guardia Lombardi (AV). Geol. Appl. IdrogeoL 19, 1-15.
BELVISO R., CHERUBINI C., COTECCHIA V., DEL PRETE M., FEDERICO A., 1977. Dati. di composizione
mineralogica delle argille varicolori affioranti nell'Italia Meridionale fra i fiumi Sangro e Sinni.
Atti 2° Congr. Naz. sulle Argille 1976, Bari, Geol. Appl. Idrogeol. 12, 123-142.
BoENZI F., CrARANFI N., PIERI P., 1968. Osservazioni geologiche nei dintorni di Accettura e di Oliveto
Lucano. Mem. Soc. Geol.- It. 8, 379-392.

100
L. Dell'Anna
DELL'ANNA L., LAVIANO R., 1982. Composizione mineralogica, granulometrica e chimica delle argille
grigio-azzurre inframesoplioceniche di Cairano e Conza della Campania. Rend. Soc.lt. Min. Petr.
38, 871-881. . - - -~--· ~· ~~.----~·---
DEL PRETE M., TRISORIO Lruzzr G., 1981. Risultati dello studio preliminare della frana di Calitri (AV)
mobilitata dalla scossa sismica del 23 novembre 1980. Geol. Appl. Idrogeol. 16, 1-13.
Dr PrERRO M., MoRES! M., 1982. Caratteri granulometrici, mineralogici e chimici dei sedimenti pelitici
inframesopliocenici di Calitri e S. Andrea di Conza (AV). Rend. Soc. It. Min. Petr. 38, 353-366.
Dr PrERRO M., MoRES! M., 1984. Caratteri granulometrici, mineralogici e chimici dei sedimenti pelitici
inframesopliocenici di Rapone e Ruvo del Monte. Geol. Appl. Idrogeol. 19, 107-120. ·
Dr PrERRO M.,-MORESI M., 1985. Compositional Characteristics of «Argille Varicolori» from Outcrops
of Bisaccia and Calitri, Avellino Province, Southern Italy. These Proceedings.
HIEKE MERLIN 0., LA VoLPE 1., NAPPI G., PICCARRETA G., REDINI R., SANTAGATI G., 1971.Note illustrative
della Carta Geologica d'Italia. Fogli 186 e 187 «S. Angelo dei Lombardi», «Melfi>>, 1-188,
Roma.
HUERTAS F., bNARES J ., PESCATORE T ., POZZUOLI A., 1977. Risultati preliminari sui depositi pelitici di
mare profondo nel Flysch di Gorgoglione (Appennino Meridionale, Italia). Atti 2° Congr. Naz.
sulle Argille 1976, Bari, Geol. Appl. Idrogeol. 12, 251-259.
LoJACONO F., 1981. Contributo alia ricostruzione paleogeografica del bacino di sedimentazione del
Flysch di Gorgoglione (Lucania). Boll. Soc. Geol. It. 100, 193-211.
LoJACONO F., 1983. Nuovi dati sui caratteri deposizionali del Flysch di Gorgoglione. Considerazioni
sulla paleomorfologia del bacino. Dipartimento di Geologia e Geofisica, Bari 1-37, Adriatica Ed.,
Bari.
MAGGIORE M., WALSH N., 1975. I depositi plio-pleistocenici di Acerenza (Potenza). Boil. 'soc. Geol. It.
94, 93-109.
OGNIBEN L., 1969. Schema introduttivo alia Geologia del confine calabro-lucano. Mem. Soc. Geol.lt.
8, 453-763. .
--- -~~----~-CJRTOLANI F.·; To-:R'RE M:;-t98 L Guida all'escursione dell' area interessata dal terremoto del 23 novembre
1980. Rend. Soc. Geol.lt. 4, 173-214.
PESCATORE T., 1978. Evoluzione tettonica del Bacino Irpino (Italia Meridionale) durante il Miocene.
Boll. Soc. Geol. It. 97, 781-805.
PESCATORE T ., POZZUOLI A., STANZIONE D., TORRE M., HuERTAS F., LINARES J ., 1980. Caratteri mineralogici
e geochimici dei sedimenti pelitici. del Flysch di Gorgoglione (Lucania, Appennino Meridionale).
Per. Min. 49, 293-330.
PrERI P ., WALSH N., 1973. Osservazioni stratigrafiche sulla formazione di Serra Palazzo nell'ambito del
po 187 «Melfi>>. Boll. Soc. Naturalisti in Napoli 82, 171-190.
SHEPARD F.P., 1954. Nomenclature based on sand-silt-clay ratios. J. Sediment. Petrol. 24, 151-158.

Miner. Petrogr. Acta
Vol. 29·A, pp. 101-119 (1985)
The Role of Microfabric in Clay Soil Stability·
FERNANDO VENIALE
Dipartimento di Scienze della Terra, Sezione mineralogico-petrografica, Universitit di Pavia, Via A. Bassi 4, 27100
Pavia, Italia
This general lecture, delivered by F. Veniale, was prepared in association with N. Augustithis 1 ,F.
Caucia, S. Cocito, A. Federico 2 and L. Vacchini.
1 Hymettou 89 - Pagrati, Athens, Greece
2 Istituto di Geologia Applicata e Geotecnica, Facoltit di Ingegneria, Universitit di Bari, Via Re David 200, 70125
Bari, Italia
ABSTRACT- Microfal;Jric analysis of clayey landslide bodies, as investigated
by scanning electron microscopy (SEM), is a suitable tool for helping to
understand the causes of soil movements and slope instability, as.well as
other mechanical properties and behaviour.
Clay shale type materials are frequently found in Italy (varicoloured shales,
interbeds in Flysch formations). The transitional character ·of their properties
between those of stiff clays and soft rocks is a cause of uncertainty with
respect to their behaviour in civil engineering works. The factors that control
the behaviour of clay shales are: a) the presence of.true clay minerals, b) the
grading of clay fractions, c) the type of clay mineral. d) the strength of bonds,
e) the permanence of bonds, f) the effective stresses and degree of saturation,
g) the density and geological stress history, h) the nature and strength of
discontinuities, and i) the influence of discontinuities on the in situ permeability.
Several field examples and laboratory experiments with mixtures of different
clay minerals illustrate various conditions: loose network and «domain>>
texture with microfissures in smectitic and kaolinitic soils, respectively; influence
of the variations ·of water content (drying/wetting cycles), and of
• electrolyte concentration in pore water solutions, on the fabric of soil composed
of swelling or inert clay minerals; rearrangement of clay particles
under shearing stress actions, and its influence on shear strength; as well as
the effect of precipitates (calcite, gypsum) on friction strength. Weathering
processes play an important role in modifying the particle arrangement and
weakening the bonding forces.
In the case of overconsolidated clays, the influence of fabric modification
(from iso-oriented packing to more open arrangement of the clay particles)
, due to ,«softening» by unloading, which is the cause of tension disturbance
and bonding relaxation, is suggested as a possible mechanism of development
of failure.

102 F. Veniale
Introduction
Clayey soils and their relevant
properties are of primary concern for
specialists dealing with landslide
problems. The considerable complexity
of these materials certainly warrants
separate treatments of the sub-·
ject, and a detailed knowledge of
their mechanical, hydraulic, geotechnical
and engineering parameters requires
a reasonably comprehensive
account of the relationship among
the wide range of factors governing
soil behaviour, i.e. its response to
different stimuli. A number of different
sequences of conditions and
___________ events can set the stage for failure.
There are still a number of unknown
and unexpected behaviours, and
their recognition and testing is fundamental
for understanding the
causes of strength loss and failure.
The conventional methods of
analysis do not satisfactorily model
the field behaviour of clayey soils; in
fact, although soil mechanics theory
is adequate to describe the occurrence
of soil mass movements in
mathematical terms, little is known
about the factors and processes involved
in natural slope stability and
how to predict or control their
occurrence, except in very specific instances.
Moreover, discrepancies exist
between geological and engineering
approaches. Geologists tend to
place greater emphasis on mineralogical
and textural analysis, while
geotechnical engineers rely more on
practical tests along with analytical
approaches. Therefore, even limited
to the interface problems between
geologicaLsciences __ and. geothecnical
engineering, here is a need for the
development of a common base of
knowledge and a common language.
In this interdisciplinary light,
when combined with mineralogy and
geological history, detailed information
concerning the soil microfabric
will help in understanding the nature
of the problems relating to slope instability,
susceptibility to erosion
and permeation, and also in devising
suitable remedial measures.
Scanning electron microscopy
(SEM) (now becoming routinely
available because of its increased
use) is a tool offering many possibilities
in the study of soil fabric, properties
and behaviour. Although the
usual observations with SEM do not
produce quantifiable results (in
terms of the engineering properties of
soils) that can be directly applicable
in practice, they can be very valuable
in soil mechanics research for qualitative
appreciation and confirmation
of soil properties. Namely, SEM
observations can visually illustrate
properties otherwise indirectly derived,
as well as provide an insight
into the behaviour of soils (compaction,
cohesion, permeability, drainage,
swelling conditions, strength, intact
and remoulded states, fabric induced
by shearing and by reconstitution,
etc.). At present there· is an increasing
trend towards quantifying
fabric analysis, renewing and stimulating
the interest in such a tool for.
the study of soil properties and behaviour.

The Role of Microfabric in Clay Soil Stability 103
Importance of micro-fabric in landslide
researches
Soils are «particulate media», i.e.
substances having a framework of
more or less easily separable solid
components (skeleton= sand- and
silt- size grains of quartz, feldspars,
carbonates, etc.; plasma = clays and
other colloidal particles), which enclose
interconnected voids of irregular
size and shape. The void spaces
may be wholly or partly filled with
liquids, generally water, and gases
(air, etc.). The nature,

104 F. Veniale
changes in the chemical composition
of pore solution favouring the dispersion
of the solid particles. The spontaneous
intake of moisture by cohesive
soils is associated with volume
increase. If this is prevented, pressure
develops. The swelling pressure decreases
with increasing moisture content
and porosity. Volume expansion
during water intake may be viewed
as reverse consolidation.
Plasticity is influenced by the characteristics
of the clay-liquid system
such as (clay) mineral composition,
specific particle surface, clay particle
shape and size, type and concentration
of the solution ions. Any funda-
____ ----~--mental inquiry into the mechanical
properties of soils requires a knowledge
of the changes in the chemistry
of the pore fluids accompanying
variations in applied stresses.
According to different points of
view there are different «kinds» of
water: pore(mobile), solvatation,
adsorbed (held) water. Different re"
taining forces act on the soil water
and govern its mobility; for example,
size and shape of pore voids influence
the value of the capillary forces.
Also, the adsorption of water molecules
on the particle surfaces (surface
tension forces), and the suction (work
for removal) of water from the soil
pores are to be considered. Moisture
transport (water flow under the influence
of a hydraulic gradient) is the
'mechanism most often of practical
interest in determining the condition
(degree) of saturation.
It should be emphasized that water
encountered in soils generally contains
electrolytes in solution, a fact
which- adds~ to--the_ complexities of
analysing its behaviour.
Pore size and shape, and the nature
and concentration of electrolytes in
interstitial pore solutions are factors
influencing drainage conditions (permeability
to water transport).
The coefficient of permeability is
dependent upon fluid properties (viscosity,
electrolyte concentration) and
medium properties (grain size, void
ratio, pore geometry); it is related to
the interaction between charged soil
particles and the ions of the soil water.
The process of drainage is accompanied
by dissipation of pore water
pressure and by volume changes, resulting
from simultaneous changes in
fabric.
Shearing resistance and failure,
and the resultant movements are
mainly determined by variations of
the moisture regime, and by the factors
_ influencing water transport
movement through the channel network
of the soild; resulting increase/
decrease of pore water pressure, water
uptake/release by swelling clay
minerals (and other matter),
dissolution/precipitation of intergranular
cement(s), change of pore
water composition, wetting/drying
and frost actions, all will. alt~r the interparticle
«bonding>> conditions.
Fabric rearrangement (as a consequence
of loading, sliding, etc.) to
closer/looser configuration with corresponding
reduction/increase of the
void ratio and water content will
modify the mechanical and hydraulic

. The Role of Microfabric in Clay Soil Stability 105
properties and the behaviour of the
soils.
Deformational responses such as
the process of consolidation (i.e. the
time-dependent dissipation of porewater
pressure after loading) and the
consequent volume changes are influenced
by the swelling capacities of
clay constituents.
· Consolidation processes in clay
soils can be active for a lgng time and
comprise aging effects; moreover, the
tensional history can give rise to
overconsolidation conditions. The
analysis of these phenomena should
account for the relative movement of
the soil skeleton-plasma when water
is extruded.
The swelling processes in clay soils
may be viewed as due essentially to
osmotic forces within the extremely
thin capillary voids functioning as
semi-permeable membranes. Reduction
of the amount of swelling by
hardening of clay soils may be attributed
to the time dependent reformation
of interparticle bonds, with concomitant
reduction of the final moisture
content.
The absence of swelling clay
minerals does not mean necessarily
that the probability of failure is substantially
less. Critical conditions
can occur also in soils devoid of
swelling clay minerals: changes in
the pre-existing interparticle «bond~
ing>> forces can be due to variations in
moisture content and electrolyte concentration
in pore water. Dramatic
movements may take place quickly, if
not suddenly, with catastrophic damages
( slides in periarctic,
glacial areas such as Scandinavia,
Canada, etc.).
Causes and consequences of fabric
modifications for slope stabilityfailure
Fundamental investigations have
shown the influence of different
mineralogy on the soil fabric, as well
as the effect of the nature and electrolyte
concentration of the interstitial
water on different aspects of clay
particle arrangement.
Several examples from the Oltrepo
area (Province of Pavia, northern
Apennines, Italy) illustrate the influence
of different clay mineralogy on
the soil fabric (Plate I).
The water content in soils may
have different effects on the microtexture,
depending on the predominating
kind of clay constitutents.
Soils mainly composed of «inert>>
clay minerals (such as kaolinite,
mica-illite, chlorite) tend to open the
voids with increasing moisture (Plate
II); on the contrary, when swelling
smectite is the dominant clay mineral,
pores and fissures seem to become
obliterated after high water contents.
In such a condition the soil is virtually
impermeable. Partially swelling
vermiculite has an intermediate behaviour.
On the other hand, drying
can give rise to shrinkage (thus increasing
the friction), cause collapse
of open particle arrangements, prevailing
development of domain type
aggregates in kaolinitic soils and

106
F. Veniale
Plate I - Soil derived from varicoloured shale (the most common constituents are kaolinite,
mica-illite and chlorite): the fabric is characterized by clusters («domains>>) of clay particles,
bordered by microfissures, and including larger cystals of carbonate (A) and of irregularly shaped
quartz (B). (C) and (D): soil composed also of vermiculite. (E) and (F): soil derived by weathering of
marls (largely composed of smectite, plus vermiculite and «Open>> illite) showing loose alveolate
(«honeycomb>>) network with «Onion-skin>> and curly appearance of the tactqides.
formation of tension cracks in the
smectitic ones (Plate Ill).
An other factor influencing the
space arrangement of the clay particles
is the concentration of electrolytes
in the interstitial water (see
Plates Ill and IV). Looser or closer
fabric will influence porosity and
drainage, pore water pressure and
swelling pressure, and therefore, hydraulic
and mechanical behaviour of
the soils. This also constitutes the

The Role of Microfabric in Clay Soil Stability 107
Plate 11- Weathered sandstone: (A) air-dried, and (B) wetted by suction of water at pF= I. Vermiculitic
soil constituting the weathering residue after leaching of the carbonate components from a
marly rock, respectively, (C) in air-dried and (D) in wetted conditions. The void obliteration is less
developed than in smectitic materials. Smectitic material derived from marly Flysch (gliding
surface of landslide body): (E) air-dried, (F) water content 30% (pF= 1.5). The fissures have been
· virtually obliterated by wetting. ~

108 F. Veniale
Plate Ill- Lateral slip surface in the main track of a mudflow in variegated clays (smectite is the
predominant component). (A): fabric with evident iso-oriented arrangement of the clay particles
(smoothed surface); (B): the same sample dried. Note shrinkage micro-fissures giving rise to
mechanical obstacles. Kaolin (relative liquid limit 63%) remoulded and moisted (saturated) with
distilled water at various consistency states: w=63% (C), 117% (D) and 159% (E). At lower water
content, particles are anisotropically associated face-to-face and clustered in large «domains>>; by
increasing water content, the size of domains is gradually reduced, until a discrete alveolate fabric
has been formed (which can be compared with the type) with larger porosity. Contacts via
connecting bridges are locally constituted by single particles only.
basis for stabilization treatments by
salt diffusion. Mechanical factors
such as loading and stress modify the
mutual spatial relations between
clay particles; at large strain (residual
conditions), it induces a pecu-

The Role of Microfabric in Clay Soil Stability 109
Plate IV- Effect of KC! diffusion on the fabric of a soil stabilized by such treatment: (A) before
treatment, (B) after 12 months, and (C) after 24 months of KC! diffusion (

110 F. Veniale
Plate V- «Scaly>> clay composed of mica-illite, kaolinite-dickite and chlorite. (A): cross-section
showing «domains» (clusters) and single particles arranged without preferential orientation, constituting
a matrix which includes larger platelets; (B): detail of the scaly surface (see also top of (A))
with iso-oriented and welded particles in a planar configuration, disturbed by packing of lamellae
(C) perpendicular to the scale surface. (D)-+(E)-+(F): gradual and progressive iso-orientation of the
clay particles along a slip surface (landslide).

The Role of Microfabric in Clay Soil Stability 111
Plate VI- Variegated shale with diagenetic dickite along scaly surfaces. (A): cross-section; the
action of shearing stresses has originated a smoothed iso-oriented coating film (see detail in (B))
with sub-parallel orientation (C), and/or curving and breaking (F) of dickite lamellae. (D): detail of
random fabric in the layer underlying the dickite film. When freely grown in «open» space, the
dickite particles are randomly deposited along the fissility surface (E).

112
F. Veniale
Plate VII- (A) and (B): pore spaces partially or completely filled with calcite crystals. (C), (D) and
(E): irregular grains of calcite and flakes of gypsum deposited within the interlayering of laminated
clays (cross-section). (F): detail of a laminated surface (parallel view).

The Role of Microfabric in-Clay Soil Stability 113
Plate VIII'--- «Val Luretta» Flysch formation, torrent Versa (PV), northern Apennines. Unweathered
clayey layer (A) showing an iso-oriented compact texture. (B) and (C) are incipient and deep
degrees of weathering of the same as observed at the root and within the debris flow (slide mass) of
a· landslide body, respectively. A more isotropic rearrangement and distancing of clay particles,
carbonate-quartz-feldspar grains, as well as increased porosity, are evident. (D) corresponds to an
intermediate stage: a lense remnant of unaltered scaly clay is sandwiched by weathered material,
looser and porous. (e) and (f) are analogous situations of an unaltered and a weathered carbonate
aggregate, respectively, as observed in a marly layer of the same sediment.

114 F. Veniale
Plate IX-Varicoloured shale (mainly illi te), Val Chiarone (PC), northern Apennines. (A) una! tered,
(B) weakly, and (C) deeply weathered scaly surface. Varicoloured shale (mainly kaolinite), Val
Tidone (PC), northern Apennines. (a)-+(b)-+(c): fabric modification with increasing weathering, as
observed on a sliding plane.
mentation has been identified as an
important cause of an apparent pre­
.. consolidation.
Weathering processes have a considerable
effect on the mutual
arrangement of the clay particles and
other mineral grains (see Plates VIII
and IX), which results in greater distances
between the grains of solid
particles, weakened, ~

The Role of Microfabric in Clay Soil Stability 115
Plate X- Overconsolidated clay, Santa Barbara quarry, San Giovanni Valdarno, central Apennines.
(A) compact iso-oriented fabric of a deep' (m 30) sample. (B) and (C) open loose texture
of

116 F. Veniale
Plate XI- Overconsolidated clay, Santa Barbara quarry, San Giovanni Valdarno, central Apennines.
(A, left) reddish film of Fe-oxyhydroxides coating fissure walls. (B) and (C) details of iron
oxyhydroxide films on fissure walls: «wet>> and partially stage, respectively, the. latter with
detached flakes. (D) and (E) progressive shrivelling of Fe-oxyhydroxide fissure coating with increased
drying: microspherules become spaced and cracks also form.
clays are involved. Tension disturbance
and bonding relaxation due to
by unloading have been
correlated with fabric modifications
of the clay mass and along fissure
sidewalls (see Plates X and XI), which
are suggested as a possible mechanism
of failure development.

The Role of Microfabric in Clay Soil Stability 117
Concluding remarks
Mineralogy and fabric analysis can
help. in establishing soil properties
such as sensitivity, cohesion, swelling,
anisotropy, etc., as well as contribute
to the understanding of the
mechanisms involved in the strength
and deformation behaviour. Moisture
content and drainage (transport) of
water (with electrolytes) are mutually
influenced by the spatial configuration
of void/solid phases. With
reference to deformability, the nature
of interparticle bonds may explain
how a clay soil behaves when it is
loaded or unloaded. For very soft
clays (and also for weathered shales),
chemical bonds between particles
seem to play a more important role
than frictional resistance, ,and this is
an aspect that only minerl:!:logical
and fabric analyses can fully explain.
In the case of overconsolidated clays,
the influence of fabric on possible
alternative mechanisms of development
of failure (progressive distension,
release of energy) has been suggested.
Acknowledgements
The authors are indebted to M.lle
J. Berrier and Dr. D. Tessier (Laboratoire
des Sols - INRA, Versailles,
France), Dr. A. Le Roux (Laboratoire
Central des Pontes et Chaussees,
Paris), Prof. J. Gillott (Department of
Civil Engineering, University of Calgary,
Canada), and Dr. W.J. McHardy
(Macaulay Institute for Soil Research,
Aberdeen, Scotland) for their
assistance during SEM investigations.
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•

The Role of M icrofabric in Clay· Soil Stability 119
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Miner. Petrogr. Acta
Vol. 29-A, pp. 121-133 (1985)
Crystalline Minerals and Chemical Maturity of
Suspended Solids of Sonie Major World Rivers
JIRI KONTA
Department of Petrology, Charles University, Albertov 6, Prague 2, Czechoslovakia
ABSTRACT- Clay minerals predominate in the lutite supensions of the Mackenzie,
the St. Lawrence, the Orinoco, the Caroni, the Parana, the Nile, the
Niger, the Orange, the Indus, the Ganges, the Brahmaputra and the Padma;
amorphous silica with cristobalite is the major solid constituent of the
Waikato. Dioctahedral mica is the principal and omnipresent sheet silicate
with the exception of the Niger, where kaolinite dominates over mica. Chlorite
and kaolinite occur in 9 rivers out of 13 rivers studied. Kaolinite is typical
in larger portions for the tropical rivers (Niger, Orinoco, Caroni, Parana).
Montmorillonite was found only in some tropical or subtropical rivers, i.e.
the Caroni, the Nile, the Niger and the Orange and also in the Waikato. Of the
nonclay minerals quartz, acid plagioclase and potassium feldspar are common.
Amphibole occurs rarely. Calcite and/or dolomite occur in seven rivers
draining either arid regions or those with high relief.
Suspended solids of the tropical rivers ( + the Waikatofdisplay the greatest,
chemical maturity (ChM), i.e. the ratio %Al:% (Na+Mg+Ca) calculated from'
the data obtained by EDAX, whereas the rivers draining typical arid basins
are characterized by low values of ChM. Chemical maturity has a slight
positive tendency'to a linear dependence on the annual rainfall, but a low
relief of the stream always contributes to an increase of ChM. The chemical
maturity of the suspended solids of rivers is primarily influenced by the
degree of continentality (climatic factor) and secondarily by the height of the
relief (tectonic and time factor). The specific amount of suspended solids
reflecting the rate of erosion largely increases with rising relief, and lack of
vegetation accelerates the erosion still further.
Introduction
The detrital material transported
by rivers into the seas and oceans
represents according to LISITZIN ·
(1972) about 70% of the sedimentary
matter, i.e. 12.696 x 10 9 tons yr- 1 • The
supply of terrigenous material due to
shore erosion is only about 0.15 x 10 9
tons (GILLULY, 1955). The rest
belongs to volcanoclastic (11.2%),
glacial (5.6%) and eolian material
(5.6%), whereas the small remaining
portion falls to biogenic and precipitated
material (LISITZIN, 1972).
The rivers carry in suspension 3.5
times more material than in solution
and 12.5 times more than in bed load
(LOPATIN, 1952).
Clay minerals predominate in river
suspended solids. Their association is

122 J. Konta
···~~~---------conditions,
greatly influenced by the composition
of the eroded soil horizons occurring
in the corresponding river basin.
The quality of the great soil groups of
the world (GRIM, 1953) and their influence
on the Recent oceanic clay
mineral sedimentation is well known
(RATEEV, 1960; GOLDBERG &
GRIFFIN, 1964; BISCAYE, 1965;
MILLOT, 1979). Some major rivers,
however, flow across several climatic
zones and intrazonal climatic regions.
This is especially valid for very
long rivers flowing in the meridian
directions, such as the Nile and the
Parana. Other rivers studied also
transect regions of different climatic
e.g. the -Nigei", Brahmac
putra and Ganges (see Fig. 1).
The quantitative ratios of clay and
nonclay minerals in the suspended
solids of any stream oscillate only
slightly with the seasons o.f the year.
The natur-al~homogenization of the
solid suspended matter in a river environment
is so profund that KONTA
(1983) could express the following
opinion: «Mineral association in the
aqueous suspension of each river is as
characteristic as a finger print for
man>>. It is understood that sampling
must be done under constant conditions
and at the same place. In contrast
the amounts of suspended solids
vary within large limits with the seasons
of tl).e year in each river.
The investigation of minerals in
suspensions of the river streams is
significant for 1) sedimentary pet-rology,
2) soil science (rate of erosion
and main inorganic nutrients), 3)
geochemical balance of the Earth's
surficial processes, 4) environmental
hydrology.
Fig. 1 -The basins of the rivers studied occur in different regions of the continents and in various.
geographic latitudes. The solid circles mean sites of the respected meteorological stations in the'
river basins.

Samples
Sampling on membrane or glass
filters was carried out in the thirteen
rivers studied by experts in the respective
countries. The samples represent
solid particles caught from
fine lutite suspensions taken from
water in each river stream approximately
0.1 to 1.0 m below the water
surface in various months and at various
dates at distinct stations (see
KONTA, 1983; 1985). The basins of
the rivers studied occur in different
regions of the continents and in various
geographic latitudes (Fig. 1).
Crystalline minerals in the suspensions
The determination of the crystalline
minerals in the river suspensions
was carried out by X-ray diffraction
of samples oriented on sampling filters.
The results were published by
KONTA (1983; 1985). The quantitative
or semiquantitative ratios of the
crystalline minerals, calculated as
average values of all samples studied,
are given in Fig. 2. The average ratios
for rivers with less than 5 samples
must be considered as preliminary.
The following numbers of samples
were studied from the rivers (with indication
of the sampling stations, Fig.
1): 9 the Mackenzie (before the con-,
fluence with the Arctic Red River); 14
St. Lawrence (position 46°45'34" N,
71°15'23" W); 2 the Orinoco (Puente
Angosture - Middle); 1 the Caroni
(Parque Cachamay); 23 the Parami
Crystalline Minerals and ChemicafMaturity ... 123
(Santa Fe); 10 the Nile (five stations:
'I, 2", Nile East, Nile West, Assiut
Nile); 34 the Niger (9 stations: Niger
Jebba, Kaduna, Benue, Malendo,
Kontagora, Niger Kotonkarfi, NSH
Shintaku, Sabongari, Eku, see more
in KONTA, 1983); 3 the Orange (stations
not given); 12 the Indus (Jamshoro);
8 the Brahmaputra (Nagarbari);
2 the Ganges (Kazirghat); 7 the
Padma (Kazirghat); 20 the Waikato
(Mercer). The sampling dates, mostly
at one month intervals, were in the
years 1981 and 1982, some also in
1983.
Figure 2 shows that dioctahedral
mica, i.e. illite + clastic muscovite, is
the principal and omnipresent sheet
silicate in the river suspensions studied.
Only ~he suspensions of the Ni"
ger contain more kaolinite than mica.
The Waikato (in Fig. 2 not given) is
extremely rich in amorphous silica
and cristobalite, and illite occurring
in small admixtures only along with
_quartz, acid plagioclase, potassium
. feldspar and montmorillonite.
Two other common clay minerals
are kaolinite and chlorite, kaolinite
being typical in larger portions in the
rivers flowing through tropical regions
(Niger, Orinoco, Caroni, Parana);
only the St. Lawrence, Orange,
Ganges and Waikato do not contain
kaolinite. An accessory admixture of
gibbsite in some samples of the Niger
is in good concordance with the predominating
portion of kaolinite in
the suspension of this river. Chlorite
was found in nine rivers out of the 13
rivers studied. Chlorite occurs especially
in suspensions poor in kaolinite

124 J. Konta
o/o
.,_-k:::::.::::J-G;
OK
-Mi
.mMi/l~o
§r~o
~K-F
.. Na-F
~Am
~ea
~§moo
so-
60-
40-
zo-
o-
Fig. 2 - The quantitative or semiquantitative ratios of the crystalline minerals in suspended
solids, calculated as average values of all samples studied for each river. Gi: gibbsite; K: kaolinite;
Mi: dioctahedral mica; Mo: montmodllonite; Q: quartz; Ch: chlorite; K-F: potassium feldspar;
Na-F: acid plagioclase; Am: amphibole; Ca: calcite; Do: dolomite.
or without kaolinite. If, however,
enough kaolinite along with chlorite
is present (Orinoco) then the suspension
contains no montmorillonite.
Montmorillonite is the fourth clay
mineral in the river suspensions investigated.
It was found only in some
tropical or subtropical rivers, i.e. the
Caroni, the Nile, the Niger and the
Orange; the suspension ofthe Waikato
contains only a very small admixture
of montmorillonite. In thre~ rivers
montmorillonite occurs along
with kaolinite (Caroni, Niger, Nile).
The association of the nonclay
minerals detectable by X-ray diffraction
of the lutite river suspensions is
surprisingly simple but· specifically
different. A considerable portion or
admixture of quartz is always present
in the suspensions of the rivers
with the sole exception of the Caroni
where, however, only one sample was
available. The remaining nonclay
minerals are: potassium feldspar,
acid plagioclase, amphibole, calcite,
dolomite (and in the Waikato, opal
with cristobalite). Quartz, acid pla-

gioclase ·and potassium feldspar are
the commonly occurring primary
clastic minerals in the suspensions of
the rivers studied from different regions
of the world. Amphibole is the
fourth primary silicate sometimes
occurring in the lutite suspension of
the rivers (St. Lawrence, Brahmaputra,
Padma). The reason for the common
occurrence of quartz, K-feldspar
and acid plagioclase in the river suspensions
is their strong prevalence
among the ten most common rockforming
.minerals in the plutonic
rocks of the uppermost part of the
Earth's crust (WEDEPOHL, 1969).
Amphibole. occupies fourth place.
Calcite and/or dolomite, two extremely
unstable rockforming minerals
during weathering, occur in seven
out of the thirteen rivers hitherto studied.
Their presence in the river suspension
is conditioned by the occurrence
of enough limestones and/or
dolomites in the drained basins, by
arid climatic conditions (Mackenzie,
Nile, Indus) and relatively high relief
(Ganges, Brahmaputra + Padma, Indus).
Calcite and dolomite also rank
among the main rock-forming minerals
of the uppermost zone, i.e. the
sedimentary lithosphere.
In the aqueous environment relatively
less· stable primary silicates
and strongly unstable carbonates
along with relatively unstable chlorite
occur in larger portions in t~e
suspensions of the rivers flowing
either through regions with lower
annual rainfall (Nile, Indus, Mackenzie,
St. Lawrence) or with high relief
(Ganges, Brahmaputra + Padma).
Crystalline Minerals and Chemical Maturity ... 125
"
The rivers Niger, Orinoco, Caroni, Parana
and Orange contain the lowest
amounts of unstable clastic minerals
and no clastic carbonates. 'fhe first
four of those rivers collect waters
from tropical regions where the .energy
of the chemical weathering is the
highest. The only exception is the suspension
of the Orange which contains
a low portion of relatively unstable
silicates despite its draining a region
of low annual rainfall and high relief.
Major chemical elements and chemical
maturity of the suspeJ1.ded solids
The contents of major chemical
elements in the suspended solids of
rivers were determined by EDAX
(Table 1). Only oxygen and hydrog~n
are not involved because their direct
determination by EDAX is impossible.
The extremely high contents of sili-
- con accompanied by the lowest contents
of aluminium in the suspended
solids of the Nile and the Waikato is
caused by the remarkably high concentration
of diatoms. The amorphous
constituents in the suspended
solids of the rivers studied, i.e. the
opal and iron oxide pigment part,
could not be detected by X-ray diffraction.
The opal skeletons of diatoms
were found by SEM in each
river but mostly in low concentrations.
The contents of major chemical
elements are in good accordance with
the average mineral composition of
the samples studied (Fig. 2).
The chemical maturity ( ChM), of the

~ ~~.....--
1
126 J. Konta
TABLE 1
Weight per cent of major chemical elements in the suspended solids of thirteen rivers,
calculated to 100% without oxygen and hydrogen and chemical maturity (ChM = %AI :
----o--o-
--~~----
. -~
%/Na+Mg+Ca/) of the suspended solids
River Na Mg AI Si s K Ca Ti Fe ChM
Mackenzie n.v. 3.36 17.99 56.32 0.35 4.54 3.97 0.40 13.07 2.5
St. Lawrence 2.91 5.24 17.73 51.80 n.v. 4.59 3.13 0.92 13.68 1.6
Orinoco 1.28 2.12 18.04 47.72 n.v. 3.79 0.38 1.02 25.65 4.8
Caroni 2.05 2.51 24.44 50.84 0.71 2.07 1.41 0.57 15.40 4.1
Par ami 1.06 1.87 18.92 55.11 n.v. 7.26 0.61 0.88 14.29 5.3
Nile n.v. 2.81 14.02 61.72 2.23 1.86 8.44 0.88 8.05 1.2
Niger 1.38 3.20 29.23 55.84 n.v. 1.45 0.70 0.58 7.63 5.5
Orange 5.21 2.85 17.27 57.69 n.v. 4.74 2.89 1.15 8.20 1.6
Indus 1.48 4.21 17.86 53.14 0.83 5.02 6.37 0.38 10.70 1.5
Ganges 4.00 2.37 14.22 54.44 n.v. 6.28 4.92 1.63 12.15 1.3
Brahmaputra 1.57 4.30 19.01 50.25 n.v. 6.56 1.47 0.85 15.99 2.6
Pa:dma 0.28 2.40 16.19 52.00 n.v. 6.90 4.06 0.74 17.42 2.4
Waikato n.v. 0.61 11.57 67.98 1.25 2.12 1.50 0.27 12.38 5.5
Remark: Waikato Cl 0.75%, Mn 1.57%; n.v. = no line visible
~---~-------su.s-periaed solids in the rivers studied
is expressed by a simple ratio% Al: %
(Na+Mg+Ca). The Niger and the Parana
with the largest values of ChM of
their suspended solids also contain
the largest portions of kaolinite +
dioctahedral mica of the rivers studied.
The Niger moreover contains a
small admixture of gibbsite. In contrast,
the rivers draining typical arid
basins are characterized by low
values of ChM. The high chemical
maturity of the suspended solids of
the Waikato river testifies to the
strong leaching of the rock material
in this river basin, probably due to
recent and subrecent postvolcanic
hydrothermal activity. The chemical
maturity values obtained are the
most characteristic and sensitive
material properties of the suspended
solids suitable for correlation with
the environmental factors of the rivers
studied and their basins.
Environments of rivers
Table 2 contains a numerical expression
of some of the most important
properties or suitable factors of
the rivers and their basins.
Theoretically, the chemical maturity
of suspended solids transported
by the rivers depends on the exposed
rocks and the intensity of the weathering
processes in the drainage
basins. The intensity of weathering
of the eroded rocks reflected in the
chemical maturity (ChM) of the
suspended solids depends on several
primary factors (KONTA, 1984):
ChM = f (R, E,, A+H, Em, t)', (1)
where ChM is the chemical maturity
of the crystalline and noncrystalline
solid particles in the aqueous suspension;
R represents the rocks exposed
in the drained river basin; E, is the
accepted solar energy; A denotes the
eomposition of the atmosphere, in-

Crystalline Mirzerals and Cherrizc;iMaturity ... 127
TABLE 2
Numerical expression of some of the most important factors obtained for major world rivers
studied
Rivers
River basins
1 2 3 4 5
River ChM Simple measure Suspended Continentality Annual
of the relief, solids, degree, rainfall,
(Sh:L) X 100 g·m-3 K= [1.7 XA/sin(cp+ 10°)] -4 mm
Mackenzie 2.5 10 184 68.0 282
St. Lawrence 1.6 6 9 60.3 796
Orinoco 4.8 58 178 10.6 1 990
Caroni 4.1 308 ? 0.2 1 716
Parana 5.3 49 49 22.0 1 240
Nile 1.2 32 1 371 31.3 506
Niger 5.5 34 26 30.5 1 250
Orange 1.6 151 1 681 32.1 466
Indus 1.5 167 2 879 51.5 399
Ganges 1.3 180 2 721 40.9 1 098
Brahmaputra 2.6 162 1 270 30.2 1 830
Padma 2.4 171 1 970 34.2 1 465
Waikato 5.5 53
Remarks to the columns: 2) Calculated from the data according to NETOPIL (1972) or
BALEK (1983) or GERASIMOV et al. (1964). 3) After DEGENS (1982), for the Orange after
LISITZIN (1972), for the Waikato after the recent samplings. 5) After GERASIMOV et al.
(1964); the number and sites of the respected meteorological stations are indicated in Fig. 1
by solid circles
eluding the soil atmosphere; His the
hydrosphere and denotes the amount
of water which has penetrated into
the surface rocks and its chemical
aggressiveness; Em denotes the energy
_of tectonic movements expressed
mostly by the relief; t is the duration
of the 'action.
It is very difficult or impossible to
express numerically the primary factors
in the above equation. It is
however possible to use for rivers and
their drainage basins other reliable \
values in which the primary factors
are involved. Table 2 contains some
accessible data for the rivers studied
and their drainage basins. In this
"table, column 1) ChM is the chemical
maturity, i.e. % Al: % (Na+Mg+Ca)
ratio based on the EDAX data. Column
2), (Sh:L) x 100, is a simple
measure of the relief, strongly depending
on Em, where Sh denotes
height of the spring area of the river
above sea level in metres and L is the
length of the river in km. Column 3),
suspended solids in g·m- 3 , involves
several primary factors, mainly Em, R
and also A+H and Es. Listed in column
4) is the continentality degree, K
= [(1.7 A)/sin (

128 J. Konta
Correlation analysis between all
and A+ H. Column 5), annual rainfall Correlation diagrams
in mm, involves the main value of the
primary factor H.
/ /
Other potential factors were also
examined, namely mineral maturity,
MM, expressed as% sum of relatively
stable minerals divided by % sum of
relatively nonstable minerals (from
Fig. 2 quartz+ clay minerals without
chlorite are the stable minerals
whereas chlorite + remaining minerals
below quartz are the nonstable
minerals); the discharge of rivers in
factors given in Table 2 has shown
that the chemical maturity has the
expected although only slight positive
tendency to a linear dependence
on the annual rainfall (Fig. 3). The increase
of water precipitations penetrated
into the exposed rock profiles
leads to a higher removal of sodium,
magnesium and calcium and to a relative
increase of aluminium. The experimental
m 3·sec-1 ; the relative portion of
points in this correlation
accepted solar energy (% Es); a simple
measure of aridity (/Es: annual
rainfall! x 100). Factor analysis ·and
.. ----~-- _]egr~ss_i_Oll._aJ:}

Crystalline Minerals and Chemical Maturity ... 129
maturity of the suspended solids.
The most sensitive correlation (Fig.
4) exists between the chemical
maturity and the degree of continentality.
The experimental points are
grouped into two separate fields.
There exists a strong tendency to an
indireCt dependence between the chemical
maturity and the degree of continentality.
The tropical rivers Niger,
Parana, Orinoco and Caroni carry
lutite suspended solids of high chemical
maturity. The low degree of continentality
connected with high rainfall
in their drainage basins is the
prevailing factor determining their
high values of ChM. It is of great significance,
however, that the ex­
_perimental points of these four tropical
rivers are linearly grouped in
100 .,.,
dependence on the secondary important
factor, i.e. the relief. The rising
relief of these rivers leads to a decrease
of the chemical maturity of the
eroded suspended matter due to
growing erosion.
The situation in the other group of
the rivers studied is not so simple.
First the experimental points of the
Brahmaputra and the Padma show
their distinct transitional position
between both linerar groupings indicated
by dotted lines. The drainage
basins of the Brahmaputra and the
Padma approach the basins of the
tropical rivers by the values of very
high annual rainfall and relatively
low to medium degrees of continentality.
Experimental points for the.
rivers Mackenzie, St. Lawrence, In-
80 -;::: LOfi/RELIEF
8 I
4- I
o
I
~ I
e Mackenzie
~ St. Lawrence /
60 o • I
40
Indus /
e I
I
· Ganges I
e I
I
Ni 1 e I Orange
• I •·
I
Padma
Brahmaputra
• •
HIGH RELIEF
• Niger
20
MIDDLE
RELIEF
Caroni Ch~ ,
1 % Al:% (Na+Mg+Ca)
o+-----T-----r----,r---~----~-----r•ee----r--~,,----~,----,,
1 .3 4
Fig. 4 -Correlation between the chemical maturity (ChM) of suspended solids and the degree of
continentality (K) of the river basins.

130
]. Konta
dus, Ganges and Orange, draining regions
of arid to mild humid climates
are also linearly grouped. This means
that the chemical maturity of finegrained
suspended solids in the rivers
draining basins with the lowest
values of the annual rainfall also decreases
with rising relief. The only exception
represents the material of the
Nile with the lowest ChM value
although the stream has a relatively
medium relief. This sole deviation
can be explained by the extreme
length of the Nile and the prevailing
source of the suspended mud in the
uppermost part of the stream. A simple
measure of the Nile relief, calcu-
- ~la-tea only -for . the actual -shorter
source region of the mud, would be
much higher than 32 (see Table 2)
and would conform with the values
for the Gangt!s, the Indus or the
-orange~----------~-- =~~-~--~~-~~~ --
The steeper slope of the dotted line
intersecting this second field of experimental
points belonging to the
rivers flowing through arid to mild
humid regions shows that the chemical
maturity of the suspended
solids rises with falling relief less
markedly than in tropical rivers. The
cause of this phenomenon lies in the
lower annual rainfall and less intense
chemical weathering in the river
basins of arid and mild humid zones.
The correlation diagram in Fig. 4
helped to show that the chemical
maturity of the suspended solids of
rivers is primarily influenced by the
degree of continentality (climatic factor)
and secondarily by the height of
the relief (tectonic factor).
300 0
~
"
::J
.

Crystalline Minerals and Chemical Maturity ... 131
Figure 5 demonstrates another correlation
that shows a strong tendency
to a linear dependence between the
specific amounts of suspended solids
(g·m- 3 as the annual mean) and a
simple measure of the relief of the
stream. The specific amount of suspended
solids reflecting the rate of
erosion largely increases with rising
relief which is in agreement with the
conclusions of SCHUMM (1963),
JUDSON & RITTER (1964),
AHNERT (1970) and FAIRBRIDGE &
FINKL (1979). Experimental points
for the Nile, the Indus and the Mackenzie,
most remote from the intersectional
dotted line in the lower part of
the field (Fig. 5), testify to ~nother
important factor which accelerates
erosion, although these river basins
rank among those with ,the lowest
annual rainfall. Lack of watc;r leads
to a lack of vegetation, the natural
protective cover against erosion in
the arid drainage basins whether hot
or cold. The influence of this secondary
factor on the rate of erosion, i.e.
the density of vegetation must never
be neglected.
Conclusion
The fine· particles of suspended
solids occurring in any river represent
fairly homogenized soil material
eroded in the drainage basins. This
follows from the X-ray identification
of the crystalline .minerals and the
EDAX analyses of the suspended
solids sampled under constant conditions
at distinct stations over a
period of several months. EDAX data
enable calculation of the chemical
maturity (ChM) of the suspended
solids.
ChM = f (K, Sh:L, R) (2)
that means that ChM can be realistically
expressed as a function of the
degreee of continentality (K), the relief
(Sh:L) and the source rock (R). K
and Sh:L can easily be calculated for
any stream or its drainage basin (see
Table 2). R is the most difficult factor
to be expressed quantitatively. But
the source rocks R determine the
final association of the subordinate
nonclay minerals and also the
chlorite/kaolinite ratio (i.e. 2:2 to 1:1
sheet silicates) in those regions wh~re
the energy of chemical weathering
is not extremely high. Chlorites
completely disappear in the tropical
or subtropical regions where extremely
intensive chemical weathering
exists (the Niger, the Caroni but
also the Waikato) or where only sheet
silicates with T:O ratio 2:1 occur (the
Orange). The present results reveal
that kaolinite is not the only clay
mineral poor in silica from the warm
humid climatic zones and chlorite
the only clay mineral poor in silica
from the cold and arid climatic
zones. Both these sheet silicates with
the same T:O ratio, either 2:2 or 1:1,
are the result of weathering in those
environments where the major
octahedral elements (AI, Mg, Fe 2 +·3+)
occur with the Si atoms in the ratio of
1:1. Thus the climatic conditions are
not the single factor determining the
occurrence of kaolinite and chlorite

132
J. Konta
in the soil profiles although magnesium
and iron chlorites are the-least
stable crystalline clay minerals in an
aqueous environment. The geochemistry
of the source rocks also influences
the final chlorite to kaolinite
ratio· in the solid suspensions of rivers.
The 2:2 and 1:1 sheet silicates
substitute each other in any river environment
with the exception of
some tropical rivers draining basins
having an extremely high energy of
chemical decomposition.
Only the most common original
rock-forming silicates can be detected
by X-ray diffraction, i.e. quartz, acid
plagioclase, potassium feldspar and
-- somet1mes-·accessory- ·a:mphibole in
the river suspensions. In rivers draining
arid regions or those of high relief,
calcite and/or dolomite occur as
· ·subord.inate-detrital-minerals of the
suspended solids ..
The above equation (2) is also a
more suitable expression of the intensity
of weathering in any place of
the world. The primary factors Es and
A+H from the first equation (1) are
involved in the factor K and the
primary factors Em (and t) are involved
in the factor Sh:L.)
The correlation diagram in Fig. 4
can be used for the investigation of
the continental clay and lutite sediments
or the fine-grained portions of
residual rocks. It can help to reconstruct
the geological history of continental
fine-grained silicate material
that has not undergone substantial
diagenetic change.
REFERENCES
AHNERT F., 1970. Functional relationship between denudation, relief and uplift in large mid-latitude
drainage basins. Amer. J. Sci. 268, 243-253. ·
BALEK J ., 1983. Hydrology and Water Resources in Tropical Regions. Developments in Water Science
18, Elsevier, Amsterdam.
BISCAYE I;' .E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and
.adjacent seas and oceans. Geol. Soc. Amer. Bull. 76, 803-832.
CoNRAD V., PoLLAK L.W., 1950. Methods in Climatology. Cambridge, Mass.
DEGENS E.T ., 1982. Riverine carbon- an overview. Mitt. Geol.-Palaont. Inst. Univ. Hamburg, SCOPE/
UNEP Sonderband, Heft 52, 1-12.
FAIRBRIDGE R.W ., FINKL CH.W ., 1979. Cratonic erosional unconformities and peneplains. J. Geol. 88,
69-86.
GERASIMOV l.P. ET ALII, 1964. Fiziko-geograficheskij atlas mira. 298 pp., Akad. nauk i·GGK SSSR,
Moskva. ·
GILLULY J.J., 1955. Geologic contrast between continents and ocean basins. In: Crust of the Earth (A.
Poldervaart, editor), Geol. Soc. America Spec. Paper 62, Waverly, Baltimore.
GoLDBERG E.D., GRIFFIN J .J ., 1964. Sedimentation rates and mineralogy in the south Atlantic. Jour.
Geophys. Res. 69, No. 20, 4293-4309.
GRIM R.E., 1953. Clay Mineralogy. McGraw-Hill, New York.
JuosoN S., RITTER D.F., 1964. Estimated rates of denudation for the United States. Jour. Geophys. Res.
69, 3395-3401.
KNOCH K., ScHULZE A., 1954. Methoden der Klimaklassifikation. Justus Perthes, Gotha.
KoNTA J., 1983. Crystalline suspended particles in the Niger, Parand, Mackenzie and Waikato Rivers.
In: Transport of Carbon and Minerals in Major World Rivers; Mitt. Geol.-Palaont. Inst. Univ.
Hamburg, SCOPE/UNEP Sonderband, Part 2, Heft 55, 505-523.

Crystalline Minerals and Chemical Maturity ... 133
KONTA .J., 1984. Supergenesis and sedimentogenesis: Transport and accumulation of sediments in
different environments. Sedimentology, 27th lnt. Geol. Congress (Moscow), p. 3-10, VNU Sci.
Press, Utrecht.
KoNTA J., 1985. Mineralogy and chemical maturity of suspended matter in major rivers sampled under
the SCOPEIUNEP Project (with 23 Figures and 5 Tables). Mitt. Geol.-Palaont. Inst. Univ. Hamburg,
SCOPE/UNEP Sonderband, Part 3, Heft 58, 569-592.
LISITZIN A.P., 1972. Sedimentation in the World Ocean, Society of Economic Paleont. and Mineralogists
Spec. Pub!. No. 17 (K.S. Rodolfo, editor), Tulsa, Oklahoma.
·LoPATIN G.V., 1952. River Deposits of USSR (in Russian). Ak. nauk, Moskva.
MILLOT G., 1979. Clay. Scientific Amer. 240, No. 4, 109-118.
NETOPIL R., 1972. Hydrologie pevnin. (Hydrology of Continents). Academia, Praha.
RATEEV M .A., 1960. Rol klimata i tektoniki v genezise glinistykh mineralov osadochnykh porod. Doklady
k sobraniyu mezhdunarodnoj komissii po izuch. glin. AN SSSR, 77-83.
ScHUMM S.A., 1963. The disparity between present rates of denudation and orogeny. US Geol. Surv.
Prof. Paper 154H, 1-13, Washington.
WEDEPOHL K.H., 1969. Handbook o{Geochemistry. Vol. I, Springer-Verlag, Heidelberg, New York.

Section I
Surface Chemistry and Interactions

M in~r. Petrogr. Acta
Vol. 29-A, pp. 137-143 (1985)
Measurements of Total and External Surface Area of
Homoionic Smectites by p-Nitrophenol Adsorption
G.G. RISTORP, E. SPARVOLP, P. FUSF, J.P. QUIRK 3 , C. MARTELLONP
1 Ce.ntro di Studio per i Colloidi del Suolo del C.N.R., Piazzale delle Cascine 28, 50144 Firenze, Italia
2 Istituto di Chimica Agraria e Forestale dell'Universita di Firenze, Piazzale delle Cascine 28,50144 Firenze, Italia
3 Waite Agricultural Research Institute, Glen Osmond-South Australia 5064, Australia
ABSTRACT- The adsorption of para-nitrophenol (pNP) was used for measuring
the external and total surface area of homoionic (Na, K, Mg, Ca) montmorillonite
and beidellite.
Adsorption isotherms at 20 oc from a pNP solution in Xylene, were obtained:
a) after heating the clay samples at 160 oc; b) after equilibrating at different
relative humidity (R.H.) (10%, 42%, 90%).
A plateau at the monolayer capacity on external clay surface was only
obtained for the heated clays saturated with monovalent cations. The derived
specific surface area.was in good agreement with the specific area obtained
by Nz sorption.
In contrast unheated clays with divalent cations have a plateau at high
equilibrium concentration after equilibration atJO% R.H. It is assumed that
the plateau indicates the completion of a monolayer coverage on the external
and internal surface. The specific area obtained from this plateau closely
approaches that calculated from the clay structure.
"
Introduction
The use of solute adsorption
isotherms for measurements of specific
surface area of soils (GREEN­
LAND & QUIRK, 1964) and of other
finely divided solids (GILES et al.,
1960; 1962; 1974) has been extensively
investigated.
According to GILES et al, the
adsorption of p-Nitrophenol (pNP) at
room temperature is suitable for specific
surface area determinations on a
wide variety of organic and inorganic
substances. Generally, good agree-
ment was found with BET -surface
areas, but few data are reported for
clay minerals. It is widely recognized
that the adsorption mechanism of
polar neutral organic molecules (such
as pNP) by 2/1 type clay mineni.ls
·depends primarily on the nature and
the polarizing power of the exchangeable
cation and, to a lesser extent, on
the physico-chemical properties of
the clay surface (MORTLAND, 1970;
THENG, 1974). From IR studies,
SALTZMAN & YARIV (1975) were
able to suggest some different ass.ociations
between pNP and the interlayer
cations of homoionic mont-

-.
138 G.G. Ristori, E. Sparvoli, P. Fusi, J.P. Quirk, C. Martelloni
morillonite, depending on the hydratation
status of the clay.
The adsorption of pNP by a vermiculite
and its acid activation products
have been investigated by
JIMENEZ LOPEZ & LLEDO RUIZ
(1981). The adsorption isotherms are
of the « L » type according to the classification
of Giles and the retention
capacity decreases with increasing
temperature.
Because water competes with pNP
for ligand positions around the cations
of the clay minerals, and little
· · or no adsorption takes place from dilute
aqueous solution, pNP must be
used in non polar organic solvents.
__ --------------~_____Ee_~rewrts are _

concentrations were rapidly· added.
b) The_ same procedures also were
employed for unheated clay samples
equilibrated at 10%, 42% and 90%,
relative humidity (in desiccators containing
saturated salt solutions) to
evaluate the influence of water on the
adsorption of pNP.
All tests were duplicated. For comparison,
the external surface area of
the homoionic clays was determined
by Nz sorption, at liquid Nz temperature
after degassing the samples
overnight at 70 °C, using C. Erba
Sorptomatic equipment, and the
classical B.E.T. equation for calcula-
. tions.
Measurements of Total and Exiein;;i Surface Area ... 139
The total surface area as calculated
from structural data is reported in
Table 1.
The variations of the basal spacing
with pNP adsorption were \ietermined
by X-ray powder diffraction
(28 = 3°-10°, Cu Ka radiation).
After adsorption, some selected
clay samples were centrifuged, the
supernatant decanted and the solid
dried at 50 °C. The X-ray analyses
were then obtained (i) at room conditions,
and (ii) immediately after heating
at 125 °C, in a controlled dry
atmosphere maintained by protecting
the heated sample holder with a
Mylar film.
Results and discussion
The most significant results of this
preliminary study can be summarized
as follows:
Samples heated at 160 oc. The smectites
are completely dehydrated, as
confirmed by the collapse of the basal
spacing to 10 A. The pNP adsorption
isotherms are reported in Fig. 1. For
both clays, different types of the
curves occur depending on the nature
of the exchangeable cation. The first
section of the curves always follows
an L (Langmuir) type isotherm. The
samples with monovalent cations
have a plateau followed by a C (constant
partition) branch. For clays saturated
with divalent cations, the
isotherms show only a change in the
slope (point X) after the L section,
and then follow a C type isotherm .
According to GILES et al. (1962) the
plateau could indicate the completion
of a pNP monolayer. Assuming
flatly adsorbed pNP molecules, the
specific surface area (S) of the clay is
calculated from S = Xm · N ·A, (Xm =
the monolayer capacity (moles/g); N
=Avogadro's Number, A= the area
occupied by a pNP molecule (52.5
A 2 )). In the absence of the plateau the
change in the slope (point X) was
used for calculating S.
Good agreement with the values
from Nz measurements was found for·
both smectites with monovalent cations,
and for Mg and Ca beidellite
(Table 1). The basal spacing of all
clay-pNP complexes, except Mg and
Ca bentonite, after heating at 125 °C,
collapsed to about 10 A, for adsorp-
. tion values corresponding to the
· plateau or point X. At point X, Mg
and Ca bentonites had higher spacings
(11.4-11.6 A) indicating penetration
of pNP into the interlayer region.

140 G.G. Ristori, E. Sparvoli, P. Fusi, J.P. Quirk, C. Martelloni
1000
a)
800
600
>, 400
"'
"
·s::
QJ
"
0
..... "'
c..
z:
c.
"'
QJ
200
---~---~-TOo-D - ..
0
s:...
u
800
600
400
200
• K
o Na
• ea
X (Point X)
10 20 30 ' 40
mmo 1 es pNP /1
Fig. 1 -Adsorption isotherms of pNP from Xylene at 20°C, clay samples heated to 160°C (referred to
weight after drying at 2_00°C). a) Wyoming bentonite; b)~Mondaino beidellite.
Penetration was also observed in all
samples with adsorption values corresponding
to the C linear branch of
the isotherms: the basal spacing increased
with the amount of pNP
adsorbed, to a maximum of 12.4-12.6

Measurements of Total and E~ternal Surface Area ... 141
TABLE 1
Specific surface area of homoionic sinectites determined by N 2 sorption and pNP adsorption
Specific surface area m 2 /g(•)
external
total
N 2 sorption pNP adsorption(h) calculated(~) pNP adsorption(d)
Na W. BENTONITE 36.0 34.5 740
K 44.4 43.7 723
Mg 28.2 (206)(•) 753 750
Ca 37.1 (115)(•) 742
740
Na M. BEIDELLITE 158
K
Mg
152
128
Ca 118
152
155
134
116
715
703
723
717
710
735
(a) related to the mass of oven-dried samples (at 200°C); (b) adsorption by 160°C heated
samples; (c) calculated from structural data; (d) adsorption by unheated samples, equilibrated
at 10% R.H.; (e) calculated for comparison ·
A. These data confirm that the
plateau obtained with monovalent
cations can be used foJ;"- calculating
the external surface area, while the X
point is not always significant, as
shown by Ca and Mg bentonites.
Unheated samples. The adsorption
isotherms of unheated samples,
stored at 10% R.H. exhibit a more
uniform shape (Fig. 2, a and b): for
all homoionic smectites the L branch
is immediately followed by the C
branch. In all samples the pNP largely_
penetrates the interlayer. This is
revealed by basal spacings which collapse
(on heating at 125 oc after
adsorption) to 13.2-13.4 A at\ the
plateau, and approach the 9.9 A value
of untreated clays as the amount of
adsorbed pNP decreases.
The difference in basal spacing of
about 3.5 A is close to the standard
thickness of aromatic rings; this
seems to indicate that the pNP mole­
~cule is adsorbed parallel to the silicate
layers.
It is assumed that the plateau indicates
total surface coverage. The surface
area is calculated according to
the formula: S tot. = S ext. + (Xm
tot. -Xm ext.)·N·A; it has to be
taken into account that the pNP
molecule in the interlayer covers two
silicate layers and the effective area
for a molecule of pNP is 2 ·52 .5 = 1 OS
A 2 • The surface area calculated from
the pNP adsorption closely
approaches the ideal surface area as
derived from the dimensions of the
unit cells. The isotherms obtained
from samples stored at higher R.H.
(42%, 90%) have the same shape, but
the affinity of smectites for pNP is reduced
by the presence of the water.
The influence of water seems to be
stronger in Mg and Ca samples and
the p-lateau is not attained.

142
G.G. Ristori, E. Sparvoli, P. Fusi, J.P. Quirk, C. Martelloni
1000
600
>,
u "'
-o
(I)
·;:::
-o
I
0
....... "'
200
. ---~~--~-----------C...- --- -- ------ --.
z
Cl.
"' (I)
0
E
0
S-
u
·e;
1000
b)
600
200
o Na
• K
c, Mg
• ea
10 30
mmoles pNP/1
Fig. 2 - Adsorption isotherms of pNP from Xylene at 20°C, unheated clay samples (R.H. 10%)
(referred to weight after drying at 200°C). a) Wyoming bentonite; b) Mondaino beidellite.
50
Conclusion
it seems possible to state that the
adsorption of pNP by homoionic
Although the results obtained smectites largely depends on the
merit further detailed investigations, polarizing power of the exchangeable

0
thus
the
Measurements ofTotal and External Surface Area ... 143
cations. The heated Ca and Mg
Wyoming bentonite exhibit the highest
affinity for pNP; it is not possible
to establish the pNP equilibrium concentration
at which the organic molecule
begins to penetrate into the interlayers,
as the coverage of the external
surface and the entering into the
interlayer spaces probably occur
simultaneously. The change in the
slope of the adsorption isotherms at
point X might be indicative of the
starting penetration in less ac- ~
0
cessible sites between the layers.
InCa and Mg beidellites the polarizing
power of the exchangeable cations
is reduced. T~is is ascribed to
the shortening of the distance between
the cation and the negative
charges of the tetrahedral layers. The
difference in the affinity of the external
and internal surfaC:es to pNP
0
molecules is more pro'iJ.Ounced.
The change in the slope of the adsorption
isotherms (point X) may be
ascribed, in this case, to the completion
of external surface c;overage.
In the case of monovalent cations
with lower polarizing power a well
defined plateau at adsorption levels
corresponding to the external clay
surface supports the above conception.
In the unheated samples pNP can
easily penetrate int~ the interlayer of
smectites, but only with divalent cations
and at low relative humidity is
a plateau attained that corresponds
to a monolayer on the external and
internal surfaces.
It is suggested that reliable values
of the external specific surface of
smectites can be obtained from clays
0
saturated with monovalent cations
and heated at 160 °C, and that it may
be possible to measure total surface
area for Mg and Ca samples using
pNP adsorption if the samples are
equilibrated at low water vapour
pressures prior to the adsorption
from a non-polar liquid.
Further studies on the nature of the
isotherms are now in progress to
ascertain in detail the role of clay
structure, of relative humidity, and of
individual cations.
REFERENCES
BoEHM H.P., GROMES W., 1959. Bestimmung d,er spesifischen Oberflache hydrophiler Stoffe aus der
Phenol-Adsorption. Angew."Chem. 71, 65-69.
GILES C.H., McEwAN Z.H., NAKHWA S.N., SMITH D., 1960. Studies in adsorption. Part XI. A system of
classification of solution adsorption isotherms, and its use in diagnosis of adsorption mechanisms
and in measurement of specific surface areas of solids. J. Chem. Soc., 3973-3993.
GILES C.H., NAKHWA S.N ., 1962. Studies in adsorption. XVI. The measurement of specific surface areas
of finely divided solids by solution adsorption. J. appl. Chem. 12, 266-272.
GrLES C.H., D'SILVA A.P., EASTON LA., 1974. A general treatment and classification of the solute
adsorption isotherms. Part I!. Experimental interpretation. J. Colloid & Interface Sci. 47, 766-777.
GREENLAND D.J., QUIRK J.P., 1964. Determination of the total specific surface area of soils by adsorp,
tion of cetylpyridinium bromide. J. Soil Sci. 15, 178-191.
JrMENEZ LOPEZ A., LLEDO Rurz F, 1981. Retenciqn de p-Nitrofenol sabre una vermiculita y su producto
de activacion acida. An. Edaf. Agrobiol. 40, 21-35.
MoRTLAND M.M., 1970. Clay-organic complexes and interactions. Adv. Agron. 22,75-117.
SALTZMAN S., YARIV S., 1975. Infrared study of sorption of Phenol and p-Nitrophenol by Montmorillonite.
Soil Sci. Soc. Amer. Proc. 39, 474-478.
THENG B.K.G., 1974. The Chemistry of Clay-Organic Reactions. Adam Hilger, London.

Miner. Petrogr. Acta
Vol. 29-A, pp. 145-154 (1985)
Adsorption of Chloropropham (CIPC)
by Clay Minerals and Soils
G. DIOS CANCELA, J.A. GUILLEN ALFARO, S. GONZALEZ GARCIA
Estaci6n Experimental del Zaidin, C.S.I.C., Profesor Albareda 1, 18008 Granada, Espana
ABSTRACT - The adsorption of Chloropropham (CIPC) by clay minerals
(montmorillonite, kaolinite, illite) and a peat sample was studied. Also the
adsorption of this herbicide by six characteristic soils of the Province of
Granada (southern Spain) was studied. All the isotherms of natural and
oxidized soils, as well as those from the clay minerals and the peat, fit well to
Freundlich's model.
High correlations were obtained between adsorption capacity of natural
soils and different physico-chemical characteristics of the soils such as
organic matter, and C.E.C. In the oxidized soils there are good correlations
between K' and C.E.C.,% illite and% montmorillonite plus kaolinite.
The thermodynamic parameters ~G 0 , ~S 0 , ~Ho and the isosteric adsorption
heats of the adsorption processes were .determined in order to elucidate the
mechanisms governing this process.
Introduction
The adsorption of herbicides by ac-
. tive soil surfaces is one of the main
processes controlling herbicide phytotoxicity,
its persistence in soil and
its resistance to degradation.
Although Chloropropham (CIPC) is
a herbicide used extensively in agriculture,
studies of its adsorption by
clay minerals and soils are very
scarce. In this context, the work of
BAILEY et al. (1968) may be cite~;
these authors studied the adsorption
of different herbicide families by
montmorillonite and found that
chloropropham is adsorbed following
Freundlich's equation. Subsequently
BRIGGS (1969) studied the adsorption
of carbamate herbicides and its
relationship with Hammett's, Taft's
. and Hansch's constants. Finally,
MOREALE & VAN BLADEL (1981)
showed the existent relationship between
adsorption capacity and solubility.
Since the information about CIPC
adsorption by soils is very scarce, we
thought it interesting to study the retention
of this herbicide by some clay
1
minerals, a peat sample and by some
soils of the Granada Province (south-
. ern Spain) in order to obtain in-
, formation about the retention capacity
of the herbicide by different
adsorbents and to determine the
thermodynamic parameters control-·
ling the adsorption process.

146 G. Dios Cancela, J.A. Guillen Alfaro, S. Gonzalez Garcia
Materials and methods
Adsorbents
The

Adsorption of Chioropropham ... 147
was analyzed for CIPC by spectrophotometry
at 235 nm.
Experimental results and discussion
Adsorption isotherms of CIPC by clay
minerals and peat
In Fig. 1 the adsorption isotherms
of CIPC, at 20 oc and 27 °C,, by three
clay minerals and peat are shown.
The amount adsorbed in !J.g/g of sample
is plotted against the relative.
equilibrium concentration, C/Co, in
order to eliminate the solubility
effect on adsorption. The isotherms
adjust to Freundlich's model X/M =
K' (C/Co) 11 n where K' is the amount
adsorbed when C/Co = 1 while 1/n is
a measure of the degrye of nonlinearity
of the isotherms. ~eat fit
well to an equation of the type x/m =
a+ K' (C/Co) 11 n which has an origin
intercept. As a consequence, the
adsorption of CIPC by these adsorbents
can be considered as an adsorption
on an heterogeneous surface.
The K' values, shown in Table 2,
are ordered in the following sequence:
kaolinite > montmorillonite
> illite which is the inverse of the relationship
to the specific surface of
these minerals; consequently, the
adsorption must take place in the
more active points of the surfaces,
namely exchange cations and broken
crystal bonds, to which the CIPC
molecules will be bonded by iondipole
type interactions. The greater
retention capacity of kaolinite may
be related to the presence .of -OH
groups on one of its surfaces, to
which the herbicide can be fixed by
hydrogen bonding (BRINDLEY et al.,
1963). It is also possible that inter-
8000 Peat
7000
6000
1000
Montmorill onite
5000
4000
0.2
0.4 0.6 0.8
0.2 0.4 0.6 0.8
3000
2000
1000 Ill ite
20'C
~27'C
~c~•
~~·~
C/Co 00o•- C/CO
01+---~---,--~--~---
0 0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8
Fig. 1 -Adsorption isotherms of CIPC by clay minerals and peat.

148 G. Dios Cancela, J.A. Guillen Alfaro, S. Gonzalez Garcia
TABLE 2
Freundlich's constants K', 1/n and a values for adsorption of CIPC by clay minerals, peat
and soils-··-
K' 1/n a
20"C 27°C 20°C 27°C 20°C 27°C
Tidinit Montmorillonite 739.1 730.0 0.86 1.0 0 0
Beavers Bend Illite 646.4 624.7 1.0 1.0 0 0
Lage Kaolinite 1179.6 1077.6 0.95 1.0 0 0
peat 12959.0 13122.0 1.0 1.0 162.4 151.0
P-8 2105.0 1808.0' 0.674 0.748 0 0
P-9 1308.0 1234.6
P-10 1246.0 1112.0
P-11 794.5 800.0
P-12 1877.8 1750
M-128 750.0 756.0
P-8 oxidized 1971.0 1648.4
P-9 oxidized 1011.0 942.0
P-10 oxidized 2269.0 2500.0
P-11 oxidized 885.0 813.0
P-12 oxidized 1080.0 940.0
a: y axis intercept
1.0 1.0 0 0
0.88 0.96 0 0
0.99 1.05 0 0
0.91 0.96 0 0
1.0 1.0 0 0
1.0 0.995 0 0
1.167 L202 0 0
1.367 1.65 0 0
1.004 0.97 0 0
1.05 0.973 0 0
:li
'' ,, !
•I
:I
I
'I I
'I
I
i:
I
crystalline pores intervene in the
adsorption process. The size and
shape of intercrystalline pores in
particle aggregates depend on the
crystallinity, uniformity and dimensions
of the particles.
Peat exhibits a great affinity for
CIPC at low equilibrium concentra-.
tions that may be explained by the
presence of hydrophobic groups by
which CIPC is strongly retained. It·
can be observed that the adsorption
power of peat is 10 times greater than:
that of the clay minerals; this is in'
agreement with that found by other
authors (SALTZMAN et al., 1972).
Thennodynamic parameters related to
adsorption
In order to know the thermodynamic,
parameters controlling the retention
process and to predict the possible
adsorption mechanisms, the
values of LlG 0 , LlS 0 and LlH 0 associated
with the adsorption ofCIPC by clay
minerals and peats, were calculated
following the methods of BIGGAR &
CHEUNG (1973).
The LlG 0
values are negative and
range from -6.2 kcal!mol, for the
peat, to -3.4 kcal!mol for illite, following
an order analogous to that of
the adsorption capacity. This negative
value of LlG 0 accounts for the persistence
and resistence to degradation
of this herbicide in soils.
The LlS 0 values are negative, except
for the illite, which suggests a lower
degree of liberty of this herbi~ide in
the adsorbed phase. In the illite,
these values are positive, possibly be-.
cause the adsorption of CIPC involves
the previous desorption of other·
molecules such as water.
All LlH 0
values are negative, this
implies that the adsorption process
for CIPC is exothermic. But the mag-

nitude of AH 0
is an average value for
the adsorption process, so that this
param~ter does not allow clarification
of the mechanism which governs
the process. For this reason, it is
necessary to calculate the isosteric
1000
,
2o•c / . /
.../ z· _.z:,id,,"
• /",..Xunoxidized
./
.....
j/ ,.....
7 / 0 / Soi 1 P - 8
,.
......
0 .
1000
0
1000
12000
12000
Adsorption of Chloropropham ... 149
0.4 0.8
1000
0.4 0.8
1 ODD
adsorption heats as a function of the
degreee of coverage using the expression:
AH =
0.4 0.8
12000 ./ .....
./ .,.., .......
/./ ,,o ... o
......... • .,.V" ... o"
/•/,..o_..o .. ""
,• ._.- Soi 1 P - 9
.... •::- .... -
0.4 0.8
E
-.._
X
0
1 DD 0
' Soil P- 1 D
0.4 0.8
0.4 0.8
0
1000
12000
0.4 0.8
,
~ '.·
,o'
..
/,9"·
o~•
,~soil P-.11
0.4 0.8
1 ODD / ./1000
12000 /• .,.,...,.o"" ,
(" _..--·/•
e.,.o'
/
·-- ----·
o/
_. Soi 1 P- 12
0.4 0.8
C I Co
0.4 0.8
Fig. 2 - Adsorption isotherms of CIPC by unoxidized and oxidized soils.

150 G. Dios Cancela, J.A. Guillen Alfaro, S. Gonzalez Garcia
In Fig. 2 the values obtained are
plotted against the amounts of adsorbent.
The q., values of montmorillonite
change exponentially with the coverage,
a characteristic of adsorption on
heterogeneous surfaces.
The q., range from 14.5 kcal!mol,
for low coverages, to 1.8 kcal!mol for
high X/m values. For low coverages,
these values can be interpreted on the
basis of ion-dipole type interactions
between the CIPC molecules and the
external exchange cations, or crystal
broken bonds. For coverage values
over 200 J..Lglg the herbicide adsorption
must be governed either by the
--~-~---------~layer: of oxygen atoms of the_ external
surface to which the herbicide will be
weakly linked by hydrogen bonds or
by the pores within particle aggregates
into which the CIPC will be
fixed by weak Van der Waals forces.
In the case of thekaolinite, the q.,
values also change in exponential
form with the degree of coverage, and
the existence of a first stretch of curve
at low coverage having high q.,
values, can be noted; this suggests
that the CIPC is retained on the exchange
cations by ion-dipole interactions
as in the case of montmorillonite.
Nearly constant values of qst (- 3
kcal!mol) were obtained for x/m
values over 400 J..Lg/g, indication that
the CIPC molecules are linked to the
-OH groups of the hydroxyl layer by
hydrogen bonds. The q., values for
illite are very low (about 1 kcal!mol),
suggesting that the exchange cations
in this mineral do not participate in
the retention process and that this
process is restricted either to the
bonding~ofCIPCmolecules to surface
oxygens of the layers by weak
hydrogen-bonds or to its retention in
intercrystalline pores by weak Van
der Waals forces.
In the peat, we can also observe the
existence of a first stretch for low
coverages showing high values of q.,
which must correspond to a strong
ion-dipole type interaction between
cations and CIPC molecules. These
values decrease abruptly and, over
980 J..Lg/g for the q., values, are more in
accordance with an interaction of
hydrogen-bonds or Van der Waals
type forces.
CIPC adsorption by soils
f'
In Fig. 3 the adsorption isotherms
of CIPC at 20 oc and 27 oc by different
natural and oxidized soils are shown.
All the isotherms fit Freundlich's
model expressed by the equation
x/m = K' (C/C 0 ) 11 n
so that the CIPC adsorption by these
soils can be considered as an adsorption
on an heterogeneous surface. The
values of K' and 1/n for the different
soils at two temperatures are shown
in Table 2.
The correlation between the K'
values at 20 oc for the natural soils
(unoxidized) and the physicochemical
characteristics of these
soils, included in Table 1, were studied
and the following facts found.
K' is significantly related to organic
matter content according to the equation:
K' = 696 + 92.5 (% OM) 2 ; (r =
0.92'"') and also is linearly related to

Adsorption of Chloropriipham ...
151
12 \
! Kaol inite
6 \.
: ........ .
: :·---·---·-,-
2 I I I
I I o
200 600
t
14 \
10 \
.,
6 ----~'t.,
Montmorillonite
: ·~
l ·,,
2 : ......... __
200 600
22
18
•\ Peat
...,
V>
14
10
6
2000
"" 16 \unoxidi z.ed
4000
16
10
llllte
\
.-- -----;,,
~ 2 ' --
"":::. I ·-·-·---•-•-
·-·.-·-·-·-
200 400 600
16
" .,
12
·~. Soil P-8 Soil P-9 12 SoilP-10
8
oxidized
...... ........
·-·-
4 _.1.-.-·-·-·--·-
500 1500
500 1500
500
1500
16 16
16
12 SoilP-11 12
Soil p- 12
12 Soil M-128
8 8
4 4
'•
'·
_o_o_o_o:=!:-8-e- --·-
8
4
500
x;m
1500 500
1500
Fig. 3- Isosteric adsorption heats of clay minerals,.peat, unoxidized and oxidized soils.
C.E.C. (r = 0.77), % illite (r = -0.78)
and %kaolinite plus montmorillonite
(r = 0.464). Taking into account the
existing relationship between K' and
soil organic matter content, an expression
for the adsorption of CIPC
.. by Granada Province soils can be
obtained. As a matter of fact, if we
substitute 696 + 92.5 (% OM}) for K'
in the equation x/m = K' (C/Co) 11 n, we

152 G. Dios Cancela, J.A. Guillen Alfaro, S. Gonzalez Garcfa
-
obtain the expression x/m = (696 +
92.5 (% OM) 2 ) (C/Co) 11 n, where 1/n can
take the mean value of this magnitude
for all the soils studied.
The data obtained through this
equation fit the experimental data
fairly well. An analogous equation
was found by WAHID & SETHU­
NATHAN (1978) for the adsorption of
parathion by soils.
The results obtained in this study
suggest that the organic matter content
is the most important single factor
governing CIPC adsorption by
this type of soils. This fact is not
strange if we take into consideration
that the organic matter can be associated
with clay minerals masking
- -·-~-~--- partJ.YtheeffedofilieEne.fraction on
the adsorpti_on process.
The role played by other fractions
on the CIPC adsorption by soils is
clearly made evident when the organic
matter is removed from the soils by
treatment with HzOz. In this case, the
K' values (Table 2) at 20 oc are linearly
correlated with C.E.C. (r = 0.92H),
% illite (r = -0.92~"') and % montmorillonite
plus kaolinite (r
0.97~'*''); this suggests that the
adsorption increases with the C.E.C.
and with montmorillonite + kaolinite
content, and decreases with illite
content in soils.
Thermodynamic parameters related to
adsorption
In order to elucidate the possible
mechanisms governing CIPC adsorption
by soils, values of ~G 0 , ~so and
~W~~et:(;! __ _£a}£1:1.l~!~llo"\Ving the
method of BIGGAR & CHEUNG
(1973). The values obtained are
shown in Table 3. ~Go is always negative
in both unoxidiz 0.05; '"'P = 0.01; '""'P = 0.001.

Adsorption of Chloropropham ... 153
TABLE 3
Values of AG 0 , AS 0 , and AH 0 associated with the adsorption by clay minerals, peat and soils
(oxidized and unoxidized)
Tidinit Montmorillonite
Lage Kaolinite
Beavers Bend Illite
Peat
P-8
P-9
P-10
P-11
P-12
M-128
P-8 oxidized
P-9 oxidized
P-10 oxidized
P-11 oxidized
P-12 oxidized
t°C
20
27
20
27
20
27
20
27
20
27
20
27
20
27
20
27
20
27
20
27
20
27
20
27
,· 20
27
20,
27
20
27
AG 0 AS 0 AH 0
-4.0
-4.0
-20.8
-20.3
-10.0
-5.3
-5.2
-12.6
-12.7
- 9.0
-3.4 + 1.7
-3.4 + 1.7
- 2.9
-6.2
-6.2 -
9.5
9.5
- 9.0
-4.9 -33.0
-4.7 -33.0
-14.6
-3.8
-3.8
+ 1.3
+ 1.2
- 3.4
-4.2 -24.5
-11.4
-4.1 -24.3
-3.8.
3.6
-3.7
+ 0.7
+ 0.3
-4.5 - 8.2
-4.4 8.3
- 6.9
- 1.9
- 4.0
-4.2
-4.2
+ 0.7
+ 0.6
-3.8
-3.8
+ 6.4
+ 6.3
-3.4
-3.2 -
1.4
1.3
- 3.8
-3.1
-3.0
-14.0
-14.0
- 7.2
-3.9
-3.8
+12.2
+12.0
- 0.3
-3.6 +23.0
-3.8 +22.0
+ 2.9
retained mainly by an ion-dipole type
interaction. For sample P-8 (oxidized)
these values are practically constant
between 3 and 4 kcal/mol, indicating
an adsorption mechanism of the hydrogen
bond type for CIPC adsorption,
although an ion-dipole interaction
can also take place for low coverages.
Taking into account the q., values
for samples P-9, P-11 and P-12 (oxi-'
dized and unoxidized), it seems that
the hydrogen bond mechanism for
CIPC adsorption is the predominant
one. Soil P-10 (natural and oxidized)
shows values close to those of sample
P-8, suggesting that in this case the
adsorption mechanism is of the iondipole
type for low coverages, and of
the hydrogen bond type for high
coverages.
REFERENCES
BAILEY G .W ., WHITE J.L., ROTH~ERG T ., 1968. Adsorption of Organic Herbicides by M ontmorillonite:
Role of pH and Chemical Character of Adsorbate. Soil Sci. Soc. Amer. Proc. 32, 222-234.

154 G. Dios Cancela, J.A. Guillen A/faro, S. G,onztilez Garcia
BrGGAR J.W., CHEUNG M.W., 1973. Adsorption ofPicloram (4-Amino-3,5,6-Trichloropicolinic Acid) on
Panache, Ephrata, and Palouse Soils: A Thermodynamic Approach to the Adsorption Mechanism.
Soil Sci. Soc. Amer. Proc. 37, 863-868. ·· ··· - ·····- - · ··· · ·· · --- ~···~···- -
BRIGGS G.G., 1969. Molecular Structure of Herbicides and theirSortpion by Soils. Nature 223, 1288.
BRINDLEY G.W., BENDER R., RAYS., 1963. Sorption of non-ionic aliphatic-molecules from aqueous
solutions on clay minerals. Geochim. Cosmochim. Acta 27, 1129-1137.
MoREALE A., VAN BLADEL R., 1981. Adsorption de 13 herbicides et insecticides par le sol. Relation
solubilite-reactivite. Revue de !'Agriculture 34, n. 4, 939-952.
SALTZMAN S., KLIGER L., YARON B., 1972. Adsorption-Desorption of Parathion as Affected by Soil
Organic Matter. J. Agr. Food Chem. 20, 1224-1226.
W AHID P.A., SETHUNATHAN N.J ., 1978. Sorption-Desorption of Parathion in soils. J. Agric. Food Chem.
26, 101-105.

Miner. Petrogr. Acta
Vol. 29-A, pp. 155-162 (1985)
Interaction of Chlordimeform with a
Vermiculite-Decylammonium Complex
in Aqueous and Butanol Solutions
J.L. PEREZ RODRIGUEZ, E. MORILLO, M.C. I:IERMOSIN
Centro de Edafologia y Biologia Aplicada del Cuarto, C.S.I.C., Apartado 1052, 41080 Sevilla, Espafia
ABSTRACT- The interaction of a vermiculite-decylammonium complex with
chlordimeform in aqueous or butanol solutions was studied. When the complex
is treated with an aqueous solution of chlordimeform, the degradation
of chlordimeform occurs in the interface of the interlamellar space through a
basic hydrolysis process, to yield a secondary amide which remains as a
neutral molecule in the interlamell~r space, together with the decylammonium
ions. If the complex is treated with butanol solutions of chlordimeform,
this organic cation does not interact with the clay mineral and the decylammonium
ions decompose to ammonium ions, because of the high acidity of
the residual water.
Introduction
The process of inorganic cation exchange
in clay minerals is, nowadays,
perfectly known. Likewise, clay
minerals can strongly adsorb organic
cations in their interlamellar spaces
through a cation exchange process
(MORTLAND, 1970; THENG, 1974).
Cationic pesticides are also adsorbed
by an ion-exchange process in the interlamellar
space of montmorillonite
and vermiculite (WEBER et al., 1965;
HAYES et al., 1978; PEREZ RODRI­
GUEZ & HERMOSIN, 1979; HER­
MOSIN & PEREZ RODRIGUEZ,
1981; MORILLO et al., 1983).
The intercalation of some organic
species by alkylammonium clay complexes
has been studied (THENG,
1974), but there is not much work devoted
to the behaviour of such alkylammonium
clay complexes versus
other organic cations (specially pesticides)
or to the effect of the solvent
on such process.
The present paper reports a study
of the interaction of chlordimeform,
an organic cationic pesticide, in
aqueous or butanol solutions with
decylammonium-vermiculite, in
order to investigate the mechanism
of such processes and the influence of
the solvents used.

156 J.L. Perez Rodriguez, E. Mor£llo, M.C. Hermosin
Experimental
The vermiculite used in this study
was obtained from the deposit (Huelva, SW Spain), and
it was in the Na+ form. The
vermiculi te-decy !ammonium complex
was prepared according to the
method proposed by LA GAL Y &
WEISS (1969).
Technical grade chlordimerform
(N'- ( 4 -chloro-2-methylphenyl)-N,Ndimethyl
methanoimidamide hydrochloride)
was used. This pesticide
is soluble in water (SO% by weight)
and ionizes completely giving the
chlordimeform cation (CfH+) and
·· ~--------~-chluri:d.-e-~aniorr;-ehtordimeform ·is
very stable in aqueous solution up to
pH 6.5, above which, it begins to hydrolize
according to the following
steps ((a~(b)-?(c~(d)):
CH 3
(a) Cl-QN~CH-N~ · CIH
· CH 3 CH 3
Chlordimeform chlorhydrate
pH> 5
N -F ormyl-4-chloro-o-toluidine
pH> 8 .
(d) Cl-QNH,
· CH3
4-chloro-o-toluidine
The vermiculi te-decylammonium
complex was treated with 25 mmol/1
of aqueous (pH = 4.8) or butanol
solutions of chlordimeform, at 60 °C,
shaking several times. The chlordimeform
solutions were changed
weekly.
The interplanar spacings were determined
by X-ray powder diffraction
using several orders of the (001)
reflections. The samples were examined
as oriented films supported
on glass slides.
The infrared absorption spectra
were recorded from 4000 cm- 1 to 400
cm- 1 using a Perkin Elmer double
beam spectrophotometer. Samples
were examined as KBr discs.
Results and discussion
Chlordimeform
pH> 6.5
The information about the interaction
of the decylammonium-vermiculite
complex with aqu~ous and
butanol solutions was obtained from
the study of the changes observed by
X-ray diffraction and IR spectroscopy
of the decylammonium-

Interaction of Chlordimeform with a Vermiculite~Decylammonium ... 157
vermiculite complex after several
treatments.
0

158 J.L. Perez Rodriguez, E. Morillo, M.C. Hermosin
"' u
.,_,
""'
.,.
.+'
V1
" E
1-
3500 3000 2800 1800
Wa venumber ( cm-1)
1600 1400 1250
Fig. 2 - IR spectra of the vermiculite-decylammonium complex treated with: a, water fot five
weeks; b, aqueous solution of chlordimeform for one week; c, aqueous solution of chlordimeform
for nine weeks.
,'
I
l
chlordimeform complex, because this
latter should have a basal spacing of
14.6 A (MORILLO et al., 1983). The
higher values of this basal reflection
suggest that decylammonium cations
remain in the interlamellar space
together with other organic species
which produce a change of arrangement
or disposition. of the alkylammonium
ions.
The study by IR spectra of this
vermiculite-decylammonium cornplex
without treatment and treated
with aqueous chlordimeform solutions
permits more direct information
of the species in the interlamellar
spaces of these complexes to be
obtained. These spectra are shown in
Fig. 2, for the regions 3500-2800 cm- 1
and 1800-1250 cm- 1 , where the more~.
interesting features appear.
The spectrum of the decylammonium
vermiculite complex (Fig. 2a)
shows the characteristic bands cor-

Interaction of Chlordirneform with a V e~~ulite-Decylarnrnoniurn ... 159
responding to the -CH3 (2950, 1450
cm- 1 ), -CHr(2920, 2850, 1460 cm- 1 )
and -NH3+ (3100, 1625, 1570, 1500
cm- 1 ) groups of the alkylammonium
ions. The vibrations at 1625 cm- 1 and
1500 cm- 1 correspond to the asymmetrical
and symmetrical NH deformation
of the -NH3+ groups. At
1570 cm- 1 a shoulder appears corresponding
to the symmetrical -NH deformation
of the -NH3+ groups
bonded to the basal oxygens by a
stronger H-bond (SERRATOSA et al.,
1970). The 1625 cm- 1 band also corresponds
to the OH deformation of
water, since at 3400. cm- 1 the OH
stretching band is observed, indicating
the presence of some interlamellar
water.
When the vermiculite-decylammonium
complex is treated with an
aqueous solution of chlordimeform
for one to nine weeks, the infrared
spectra show the vibrations of the
decylammonium ions at slightly
frequencies, together with others at
1675, 1523 and 1300 cm- 1 • These new
bands, appearing clearly defined after
nine weeks of treatment, do not
correspond to chlordimeform cations
and can be assigned to the amide I
(C = 0 stretching), amide II (NH deformation)
and amide Ill (combination
of C-N· and N-H vibrations)
bands of a secondary amide, besides
the 1600-1450 cm- 1 bands of the
aromatic rings. Since a secondary·
amide is the product of the irreversible
hydrolysis of chlordimeform
when the pH is higher than 6.5, this
process should occur when chlordimeform
begins to · enter in the
interlamellar space of the
decylammonium-vermiculite complex
from the aqueous solutions. The
pH in the interlamellar space should
be close to neutrality because of the
presence of alkylammonium ions,
whose hydrophobic character prevents
the entry of the bulk solution.
The 27.98 A final complex ·obtained
should be similar to the partially collapsed
complex described by JOHNS
& SEN GUPTA (1967). The alkylammonium
ions remain in the interlamellar
space with the same or less
inclination, in addition to the neutral
molecules of N-formyl-4-chloro-otoluidine.
The amide molecules can
be associated to the alkylammonium
ions by H-bonds between -NH3+ and
-C=O groups, as suggested by the
observed shiftings in the frequency of
the amide band from 1700 to 1675
cm- 1 (BELLAMY, 1975) and the 1620
cm- 1 band (N~H deformation of
-NH3+) to 1630 cm- 1 (DONER &
MORTLAND, 1969).
Interaction of the butanol solution of
chlordimeform with the vermiculitedecylammonium
complex
The X-ray powder diffraction
analysis of the vern;:ticulitedecylammonium
complex treated
with butanol and with butanol solutions
of chlordimeform for one and
nine weeks, are shown in Fig. 3. The
vermiculite-decylammonium treated
with butanol shows a basal spacing
of 21.19 A which, after one week of
treatment with the chlordimeform

162 J.L. Perez Rodriguez, E. Morillo, M.C. Hennosin
due to the solvent effect in which the
chlordimeform should be deproton- .
ated by the residual water of the clay,
since the H 3 0+ is the real interacting
species.
Conclusions
The interaction of chlordimeform
in aqueous or butanol solutions with
decylammonium-vermiculi te occurs
by different mechanisms as an effect
of the"'sG>lNent:~~-- ~-~
- in aqueous medium, the chlordimeform
is hydrolyzed yielding a
secondary amide which remains in
the interlamellar space together with
the alkylammonium ions;
-in butanol medium, the alkylan:imonium
ions are decomposed to
yield interlamellar ammonium ions,
as well as the aliphatic products of
such decomposition.
REFERENCES
-------BEbJoAMY-bJ~;-1975o-ThelnfraredSpectra of Complex Molecules. Vol. I, J. Wiley & Sons, New York.
DoNER M.E., MORTLAND M.M., 1969. Intennolecular interaction in montmorillonite: NH-CO systems.
Clays Clay Miner. 15, 259-271.
DURAND D., PELET R., FRIPIAT J .L., 1972. Alkylammonium decomposition on montmorillonite surfaces
i"n an inert atmosphere. Clays Clay Miner. 20, 21-35.
HA YES M.H.B., PrcK M.E., ToMs B.A., 1978.The influence of organocation structure on the adsorption
of mono and of bipyridilium cations by expanding lattice clay minerals. I and II. J. Colloid &
Interface Sci. 65, 254-275.
HERMOSIN M.C., PEREZ RODRIGUEZ J .L., 1981. Interaction of chlordimefonn. with clay minerals. Clays
Clay Miner. 29, 143-152.
JoHNS W.D., SEN GUPTA P.K., 1967. Venniculite-alkylammonium complexes. Am. Miner. 52, 1706-
1724.
LAGALY G., WErss A., 1969. Detennination of the layer charge in mica-type layer silicates. Pp. 234-277,
in: Proc. Int. Clay Conf. 1969, Tokyo, Vol. I, Israel Universities Press, Jerusalem.
MORILLO E., PEREZ RODRIGUEZ J.L., HERMOSIN M.C., 1983. Estudio del complejo interlaminar
venniculita-clordimefonn. Bol. Soc. esp. Min. 7, 25-30.
MORTLAND M.M., 1970. Clay organic complexes and interactions. Adv. Agron. 22,75-117.
PEREZ RODRIGUEZ J.L., HERMOSIN M.C., 1979. Adsorption of chlordimefonn by montmorillonite. Pp.
227-234, in: Proc. Int. Clay Conf. 1978, Oxford (M.M. Mortland and V.C. Farmer, editors),
Developments in Sedimentology 27. ·
SERRATOSA J.M., JOHNS W.D., SHIMOYAMA A., 1970. IR study of alkylammonium venniculire complexes.
Clays Clay Miner. 18, 107-113.
THENG B.K.G., 1974. Interactions with positively charged organic species. Pp. 211-238, in: The Chemistry
of Clay-organic Reactions, Adam Hilger, London.
WEBER J.B., PERRY P.W., UPCHURCH R.P., 1965. The influence of temperature and time on theadsorption
of paraquat, diquat, 2,4-D, and prometone by clays, charcoal, and an anion-exchange resin.
Soil Sci. Soc. Am'eJ:;. Proc. 29, 678-687.
'
I,

Miner. Petrogr. Acta
Vol. 29-A, pp. 163-169 (1985)
Anion-Exchanged Forms of Lithium Hydroxide Dialuminate
G. MASCOLO
Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli, Piazzale Tecchio, 80125 Napoli,
Italia
ABSTRACT Synthetic lithium, aluminium hydroxyde hydrate
[AhLi(OH)6j+oH-·2HzO, a hydrotalcite-like compound has been prepared
by hydrothermal treatment of alumina gel with LiOH solutions.
Through exchange react!oll_~J'_erforrned with various salts and acids, a different
behaviour has been evidentiated, according-to the selectivity of the
exchangeable anion. In the presence ofhighly selective anions (So,i-, Cl-), a
common exchange· reaction -takes place with the intedayer OH-, while with
less selective anions (CH3COO-), an antacid, rather than a true exchange,
reaction occurs.
Introduction
Mxed hydroxy structures ·have
general composition of the type
[Mt:!:,M~+(OH)zrx~~·yHzO where M 2 +
= Mg, Fe, ... , M 3 + = AI, Cr, ... , x-n =
C03, OH, ... , n = anionic charge. The
structure of these materials consists
of positively charged brucite-like
layers with a x positive charge due to
the substitution of M 3 + for M 2 +. These
layers are balanced by an equivalent
negative charge coming from inter'­
layer anions. Water molecules are
also present,
Numerous studies on the composition
and structure of minerals and
synthetic counterparts, especially for
Mg, AI systems have been reported.
The most sta:ble compounds show
M 3 + contents in moles- (x) ranging
between 0.25 and 0.33 (BRINDLEY
& KIKKAWA, 1979; MASCOLO &
MARINO, 1980; ALLMANN, 1970;
TAYLOR, 1973). The x value equal to
0.25, corresponding to the ratio Mg/
AI = 3, is commonly found in hydrotalcite.
When Mg/Al = 2 (x = 0.33),
the compound presents the highest AI
content compatible with Pauling's
rules, establishing that adjacent
octahedral sites may not be occupied
by AI couples (BRINDLEY, 1980).
Recently (SERNA et al., 1982) the
general formula for hydrotalcite-like
Financial support provided by M.P.I. (Ministry of Public Education of Italy).

164 . G. Mascolo
! '
compounds has been extended to Li,
Al hydroxy-carbonate: [AbLi(OH) 6 h
C03·nHzO, including monovalent Li
cations, where the ratio Al/Li equal to
2 represents the highest one found in
these compounds. Here the concomitant
presence of Al and Li is not due
to isomorphous replacement. In fact
Li+ occupies the interstitial sites of
Al(OH)3 layers, giving the positively
charged layer: [AbLi(OH) 6 ]+. According
to the postulate of BRINDLEY
(1980), this layer must be ordered in
such way to avoid adjacent positive
charges as found by SERNA et al.
(1982).
The ability of these layered structures
to give rise to exch~nge reactions
with different anions has been
demonstrated by BISH (1980), MARI­
NO & MASCOLO (1982), DANILOVet
al. (1977),MIYATA (1975) andBOEHM
et al. (1977).
In the present study, attention is
paid to the synthesis of Al, Li double
wholly hydroxyde also named
lithium hydroxide dialuminate
(LHDA) and to its interaction with
homocationic solutions at different
pH values:
Experimental
Alumina gel (Merck) and
LiOH · HzO (C. Erba), both R.C. grade,
were employed. Different suspensions
of alumina in LiOH solutions
(Li/(Li+Al) molar ratio ranging between
0.1 and 0.65) where prepared
employing boiled distilled water. The
· suspensions were kept in sealed Tef-
Ion containers and rotated for a week
at ~()l}.St!l!Jt Jem~E"!!!:l!"es.pf25, 60 or
90 oc in air. At the end of the hydrothermal
treatment, the products
were washed to eliminate excess
LiOH and dried over silica-gel. Exchange
reactions were carried out by
mixing 0.5 g of pure Li, Al double
wholly hydroxide with 250 ml of 0.2
or 2 N solutions at different pH
values and letting the mixtures shake
for 8 hours at 25 oc or sometimes at
70 °C.
The anions taken into consideration
were chloride, nitrate, acetate
and sulphate. As counter-cations H+
and NHt were choosen. The different
pH values of the solutions were
obtained in any case by the specific
salt or acid taken into consideration.
LizO and Ab03 were determined by
atomic absorption spectrophotometry
(Perkin-Elmer 300 s), after dissolution
of the solid . into acids. The
amount of Cl was determined following
Mohr's method and S04 gravimetrically
as BaS04. Nitrate and
acetate were not determined.
The heat-induced weight loss of
LHDA and the reacted treated materials
was determined through simultaneous
TG and DTA measurements
on 20 mg sample at a heating rate of
10 °C/min. The C0 2 content _was determined
by a calcimeter. X-ray powder
diffraction (XRD) patterns were
obtained using a Guinier de Wolff
camera with CuKa radiation. Accurate
d-spacings of selected reflections
from specimens were obtained by
measuring 28 values, with a scanning
rate of 1/8° per minute (Philips dif-

Anion-Exchanged forms of Lithium Hydroxide Dialuminate 165
fractometer). Pb(N03)z was used as
the internal standard.
Results and discussion
The crystalline phases formed after
the hydrothermal treatment of alu-
. mina gel in LiOH solutions are
summarized in Fig. 1. The dotted line
represents the boundary between the
zone containing a single phase and
that containing two phases. LHDA
corresponds to the composition
[AlzLi(OH)6]+. OH· 2Hz0, in agreement
with that reported by DANI­
LOV (1977) and by HENSLEE et al.
(1981). The concomitant presence of
y-Al(OH)3 (gibbsite), denoted with G
in Fig. 1, for XLi

166 G. Mascoio
TABLE 1
Results of the interaction between LHDA and homocationic solutions
Concentration of Temperature
the solution (N) oc
Counter-cation
Anion
cl- N03 cH3coo- soi-
(
0.2 25 H+ J D D B+D D
0.2 25. u+ NI NI NI NI
2.0 25 u+ NI NI+C c NI
2.0 25 NH.t E B+E B+C+E E
2.0 70 NH.t E+B B+E+C B+C E
D: dissolved sample; B: ba:yerite; E: exchanged form; C: carbonated form; NI: no significant
interaction
cept in the case of the CH3COOH solution
which promotes the formation of
bayerite (a-Al(OH)3). With solutions
containing Li+ as the counter-cation
(neutral or slightly basic pH) no sig-
--nificantl.ntera:ciion-takes place. Mor~
interesting results were obtained
with NH4 -containing solutions. By
treating LHDA with NH4Cl O!f
(NH4)zS04, chloride and sulphate exchanged
forms of LHDA were easily
obtained at 25 oc: The LbO:Alz03
ratio in these two solids remains the
.;ame as in LHDA, while a Cl:Alz03
ratio slightly higher than 1 and a
S04:Alz03 ratio equal to 0.5 were measured.
This involves a complete ex-.
change of the interlayer OH- anions
with Cl- and 112 soJ-. The nitrateexchanged
form of LHDA, obtained
starting from NH4N03 solutions, contained
some newly-formed bayerite,
while the acetate-form of.LHDA contained
bayerite and also some carbonated
form of LHDA. The treatments
carried out at higher tempera~
ture (70 oC) favour the formation of
bayerite and a carbonated form of
LHDA.
These results suggest two main
types of interactions:
a) [AlzLi(OH)6]+0H- · 2Hz0+ H+ +=±
2a· Al(OH)3+3Hz0+Li+;
b) [AlzLi(OH)6]+0H- · 2Hz0+ x- +=±
[AlzLi(OH)6]+X- · 2HzO+OH-
The reversible reaction a) exhibits
a typical antacid behaviour. This involves
a reaction between the H+ ions
of the contact solutions and most
likely the interlayer OH- groups of
LHDA. The corresponding change in
the electrical charge is compensated
by the removal of L{ cations from the
basic layer. Here the reaction rate increases
with decreasing either pH
values or Li+ content, in agreement
with the results of Table 1. On the
other hand at high pH values and in
the presence of Li cations, a-Al(OH)3
was easily transformed into the hydroxide
form by the hydrothermal
treatment at 60 oc of a-Al(OH)3 with
LiOH-containing solutions.
The reaction b) is a typical exchange
reaction, also favoured by low
pH values. Since reactions a) and b)
take place simultaneously, the presence
of a single phase as the interac-

Anion-Exchanged Forms of Lithium Hydroxide Dialuminate 167
tion produ~t involves different reaction
rates. The antacid behaviour of
LHDA prevails in the solutions containing
low selectivity anions, for instance
with acetate anions, giving
rise to an easy formation of bayerite.
The anion-exchange reaction on the
contrary prevails with highly selective
anions such as sulphate. The results
in Table 1 suggest the following
selectivity sequence: so]- > cl- >
N03- > CH3coo-. This sequence is in
agreement with the effects of ion size'
and charge on the rate of an ion exchange
reaction.
The presence of the carbonate-form
among the interaction products of nitrate
and acetate-containing solutions
suggests a simultaneous exchange
of both anions, which are
characterized by comparabfe selectivities.
The composition of th~carbonated
form of LHDA contains
!Coj- per [LiAlz(OH) 6 ]+ in place of
HCO_i as reported by BESSON et al.
(1973). In fact, this form, prepared by
hydrothermal treatment of alumina
gel with LhCOrcontaining solutions,
showed a C02:Ah03 ratio equal to 0.5
as reported by SERNA et al. (1982).
The possible existence of bicarbonate
and carbonate ions between the
brucite-like la:yers of the carbonateform
(SERNA et al., 1977), suggests
the following chemical equilibrium,
through a proton transfer, among the
various species of the interlayer:
Coj- + HzO +2: HC03 + OH-
Including also eo;- and/or HC03,
the selectivity sequence should become
as follows: so]-> cl- > N03 =
coj-(HC03) > C;H 3 Coo-. This order
is different from that found for takovite
and hydrotalcite (BISH, 1980).
, This may be related to a different
equivalent area per unit layer charge,
associated with the various materials
investigated.
The knowledge of the factors affecting
reactions a) and b) allows the
acetate-exchanged form to be
obtained in spite of the low selectivity
of the anion. This form was
obtained by treating LHDA with
solutions containing CH3C00Li and
CH3COOH.
The acetate-form of LHDA was
easily re~exchanged in other anion
forms.
The anion-exchanged forms of
LHDA show XRD patterns similar to
that of the original compound. The
value of the basal spacing c' of LHDA
is slightly smaller than those of the
carbonate and chloride-forms (Table
2). The higher c' values presented by
the nitrate and sulphate-forms suggest
an additional packing of oxygens
in the interlayer. A large basal
separation was found for the acetateform
(c' = 13.0 A).
Referring to the diffraction patterns
of LHDA and the various exchanged
forms, it must be empha-
TABLE 2
Basal spacing c' for variously anion-exchanged forms of LHDA
Anion t eo~- er- N03
d CA) 7.50 7.60 7.65 8.80 8.70 13.0

168 G. Mascolo
sized that the reflection corresponding
to d = 1.47 A is independent of the
layer stacking arrangement, in fact, ·
this reflection shows no shift in the
anion-exchanged form, compared to
the original compound. It may be in- ·
dexed as (hkO) with respect to hexagonal
axes. The value of this spacing,
affecting only the parameters of
the basic layer, depends of course on
the composition of the hydroxide
layer. The constancy of this value
means that the anion exchanged
forms maintain the same basic layer
composition [AbLi(OH)6]+ as in
Conclusions
.. The above-~esuits-Show the possibility
of obtaining a synthetic compound:
[AbLi(OH)6]+0H · 2Hz0 by
hydrothermal treatment of alumina
gel in LiOH solution. This compound
shows the very interesting feature of
giving rise to two different reactions:
exchange of interlayer OH- anions
and, in adgition, noticeable antacid
behaviour towards solutions containing
low selectivity-anions, not exchangeable
by the compound.
LHDA. This result and the observation
that bayerite is formed with a
Acknowledgements
.. -·----·---- __ type a) reaction (see above), suggest Thanks are due to Mrs. Palumbo
that the basic layer of LHDA derives and Mr. Annetta for the assistance in
from the introduction of Li cations . 1 carrying out some .of the experiinto
the bayerite layer.
ments.
REFERENCES
ALLMANN R., 1970. Doppelschichtstrukturen mit brucitti.hnlechen schichtionen
[Me(IIJ 1 -xMe(IIIJx(OHh]X+. Chimia 24, 99-108.
BESSON H., CAILLERE S., H:ENIN S., PROST R., 1973. Sur des hydrocarbonates voisins de l'hydrotalcite.
C.R. Acad. Se. Paris. 277, Serie D, 1273-1274.
BISH D.L., 1980. Anion exchange in takovite: Applications to other hydroxide minerals. Bull. Mineral.
103, 170-175.
BoEHM H.P., STEINLE J., VIEWEGER C., 1977. [Zn2Cr(OH) 6 ] X·2H20, New layer compounds capable of
anion exchange and intracrystalline swelling. Angew. Chem. Int. Ed. Engl. 16, 265-266.
BRINDLEY G .W., 1980. Lattice parameters and composition limits of mixed Mg-Al hydroxy structures.
Mineral. Mag. 43, 1047.
BRINDLEY G.W., KIKKAWA S., 1979. A crystal chemical study of Mg, AI and Ni, AI hydroxy-perchlorates
and hydroxy-carbonates. Am. Miner. 64, 836-843.
DANILOV V.P., LEPESHKOV I.N., KHARITONOV Yu.YA., ASHCHYAN O.T., GOEVA L.V., KOSTYLEVA O.F.,
1977. Physicochemical investigation of mixed hydroxide borate and mixed hydroxide phosphates
of aluminum and lithium. Russian J. Inorg. Chem. 22, 1137-1141.
HENSLEE ET AL., 1981. Dow. Chemical Co. Freeport, Texas, USA, JCPDS Inorg. Comp. file 31-704.
KoRITNIG S., SussE P., 1975. Meixnerite, [Mg~liOH)] 1 s·4H20, ein neues Magnesium-Aluminium­
Hydroxid Mineral. Tschermaks miner petrogr. Mitt. 22, 79-87.
MARINO 0., MASCOLO G., 1982. Thermal stability of Mg, AI double hydroxides modified by anionic
exchange. Thermochimica Acta 55, 337-383.
MASCOLO G., MARINO 0., 1980. Discrimination between synthetic Mg-Al double hydroxides and related
carbonate phases. Thermochimica Acta 35, 93-98. .
MASCOLO G., MARINO 0 ., 1980. A new synthesis and characterization of magnesium-aluminum hydroxides.
Mineral. Mag. 43, 619-621.

Anion-Exchanged Forms of Lithium Hydroxide Dialuminate 169
MrYATA S., 1975. The synthesis ofhydrocalcite-like compounds and their structures and properties.
Clays Clay Miner. 23, 369-375.
SERNA C.J ., RENDON J .1., IGLESIAS J .E., 1982. Crystal chemical study of layered [Al2Li(OH)6j+ X· nH20.
Clay Minerals 30, 180-184. · .
SERNA C.J., WHITE J.L., HEM S.L., 1977. Hydrolysis of aluminium-tri (sec-butoxide) in ionic and
monionic media. Clays Clay Miner. 25, 384-391.
TAYLOR H.F.W., 1973. Crystal structures of some hydroxide minerals. Mineral. Mag. 39, 377-389.

Miner. Petrogr. Acta
Vol. 29-A, pp. 171-177 (1985)
Interaction of Chlorthiamid withAland
Ca-Montmorillonite
P. FUSP, M. FRANCF, G.G. RISTORF
I Istituto di Chimica Agraria e Forestale dell'Universita di Firenze, Piazzale delle Cascine 28, 50144 Firenze, Italia
2 Centro di Studio per i Colloidi del Suolo del C.N.R., Piazzale delle Cascine 28, 50144 Firenze, Italia
ABSTRACT- Adsorption and decomposition of Chlorthiamid herbicide (2,6-
dichlorothiobenzamide) on Upton, Wyoming, bentonite saturated with
Al 3 + and Ca 2 + was studied using X-ray diffraction, infrared spectroscopy, and
thin layer chromatography. Chlorthiamid is adsorbed at room temperature
on Al-montmorillonite by protonation of the C=S group; while on Camontmorillonite
it is adsorbed by a coordination of the C=S group to the
exchangeable cation. This different behaviour can be ascribed to the lower
polarizing power of Ca 2 + in comparison with Al 3 +. When Ca- and Almontmorillonite-Chlorthiamid
complexes are stored at room temperature in
a desiccator or heated to 80 oc for 48 hours, Chlorthiamid partially decomposes
to 2,6-dichlorobenzonitrile (Dichlobenil, having herbicidal properties
like Chlorthiamid). This kind of non-biological degradation is typical of
montmorillonite surfaces as thiobenzamide gives benzoic acid, HzS a.nd NH3
on acidic hydrolysis and benzonitrile in alkaline medium. It should be
pointed out that Chlorthiamid is stable on heating for 48 hours in the absence
of clay. D'ichlobenil is adsorbed on Ca- and Al-montmorillonite by a
coordination of the hitrile group to the clay exchange cation through a water
bridge and the complexes are stable on heating at 80 oc for 48 hours.
Introduction
non biological decomposition to
Dichlobenil; the further degradation
of Dichlobenilleads to the formation
chlorthiamid (2,6-dichlorothiobenzamide)
of 2,6-dichlorobenzamide as a con­
is an herbicide used for weed sequence of a microbial activity
control in apples, blackcurrant, vinesand
(VERLOOP, 1972; BEYNON &
in certain ornamentals. The ma­
WRIGHT, 1972). According to FUR­
jor degradation products of Chlor-\ MIDGE & OSGERBY (1967), organthiamid
in soil are 2 ,6-dichlorobenzo..:­ ' ic matter seems to play the major
nitrile (Dichlobenil, having an herbicidal
· role in the adsorption of Chlor­
activity like Chlorthiamid) and thiamid by soil, but the reaction
2,6-dichlorobenzamide.
mechanism in this case and in clay
The initial step in Chlorthiaml.d degradation
minerals is not proposed.
seems to involve a rapid The aim of this preliminary work
is

172 P. Fusi, M. Franci, G.G. Ristori
to investigate the mechanism of
Chlorthiamid adsortpion and degradation
on montmorillonite saturated
with cations (AP+ and Ca2+)
having a different polarizing power.
It is known that this property determines
the degreee of acidity of the
water coordinated to the cation and
therefore its tendency to protonate
organic moleculesor to bind them by
hydrogen bonds (MORTLAND, 1970;
MORTLAND & RAMAN, 1968).
Materials and methods
1
Homoionic montmorillonites were
prepare~_ fr~l!?:!E~ .:::: ? J.l_ill fr-::tction of
----~---~--a~Wyoming Upton bentonite by
washing the clay three times with 1M
AlCl:i and CaCb solutions and then removing
excess salt by dialysis until a
test for cl- was negative.
Chlo~thiamid (M.P. = 151-152 °C;
purity 99.7%) and Dichlobenil (M.P.
= 142-144 °C; purity 98.4%) were supplied
by Shellitalia (Italy) and by
Fluka ($witzerland) respectively.
Self supporting clay films were immersed
in a saturated CC14 solption of
organic compound for 3 days, the excess
of the adsorbate was washed off
bycimmersion in the pure solvent and
the films air dried.
Absolute IR spectra of organic-clay
complexes were recorded with the
aid of a Perkin-Elmer model 283B
spectrophotometer in the 4000-2000
cm- 1 region while differential IR
spectra, obtained with the untreated
clay film on the reference beam, were
recorded in the 2000-1200 cm- 1 and
800-600 cm- 1 regions in order to enha:nc:e_tb_o_sLhandLthaL.in
the absolute
spectra would be obscured by
clay . water or lattice vibrations.
Three different sets of IR spectra of
the clay complex were recorded at
room temperature: i) original sam-_
ple, ii) after 3 months storage in a desiccator
at room temperature, and iii)
after heating to 80 oc for 48 hours,
then cooling in air.
The X-r;;ty diagrams of pure
homoionic clays and _ Chlorthiamid
clay-complexes were obtained using
a G.E.C. XRD-5 diffractometer with
Cu Ka radiation. The analyses, in the
range 3-15° 28, were carried out at
room temperature and on samples
heated at 110 oc for 3 hours and kept
in a dry atmosphere during the
analyses.
The original and treated organicclay
complexes were extracted with
acetone. The solution was then transferred
to 0.2 mm silicagel60 F254 plastic
sheets (Merck) and eluted with a
90:10 Chloroform-n-Exane mixture.
The spots of the components were revealed
by UV light. The Rt values of
pure Chlorthiamid and Dichlobenil
were 0.25 and 0.78 respectively.
Results and discussion
Results of X-ray diffraction analyses
of Chlorthiamid-Ca- and Almontmorillonite
complexes showed
that the organic molecule seems to
penetrate the interlayer spaces of the
clay. In fact, the basal d 001 spacings
(of about 15.22 A in both unheated.
pure homoionic clays and in Ca- and

Interaction ofChlorthiamid withAl- aiid Ca-Montmorillonite 173
Al-clay complexes) collapsed, after
heating, to about 12.6-12.8 A in
Chlorthiamid-clay complexes and to
10 A in pure clays.
The assignments of the main bands
in the IR spectrum of Chlorthiamid
are reported in Table 1 (JENSEN
& NIELSEN, 1966; RAY &
SATHYANARAYANA, 1974; BEL­
LAMY, 1980). In the solid state the
shifts towards lower frequencies of
NH stretching vibrations and towards.
higher frequencies of NH
,)ending . are due to strong intermolecular
associations.
The IR spectrum ·of the Al-mont-
TABLE 1
Assignment of the principal bands in the IR spectrum of Chlorthiamid
KBr
pellet
Band position (cm- 1 )
tetrachloroethylene
solution
Bimd assignment
3284
3138
1629
1577
1565 .
1458
1432
1410
1290
708
3498
3378
1595
1392
1316
711
" ---------,
~~~~~~------ \
v asym. N-H
v sym. N-H
8 PN-H (primaryly)
) Ring Vibcotioru
v C-N (primarily)
Skeletal vibration
v C=S (primarily)
/
I
I
I
I
I
I
I
I
I
I
I
I
I
I
/
Wavenumber ( cm-1)
L---~--r-------.--------.-------.--~--,-----,------.----~'r--.--~~
3500 3000 2500 2000
1600 1200 800 700
Fig. 1- IR spectra of Chlortliiamid-Al-montmorillonite complex: a) at room temperature, b) after 3
months storage in a desiccator at room temperature, c) after heating to 80 •c for 48 hours, then
cooling in air, d) IR spectrum of Chlorthiamid (KBr pellet). ·
I
I
I
I
l

174 P. Fusi, M. Franci, G.G. Ristori
morillonite-Chlorthiamid complex at
room temperature is reported in Fig.
1 (spectrum «a»). The appearance of
a band at 2545 cm- 1 assigned to S-H
stretching vibration (KUTZELNIGG
& MECKE, 1961; BELLAMY, 1980)
and the strong decrease of the C=S
stretching band, with a.shift to lower
i frequencies~ (a~~s~;n;.u-b~~~d b~~d remains
at 690 cm- 1 ), suggest that
Chlorthiamid is adsorbed on Aklay
by protonation of the C=S group:
r' [ r' [ Al(H,O). montmorillonite +
S
'I
c
.NH2
Cl~o Cl
V ---;.
NH 2
!.'
c·--sH--OH 2
CIOCI
+
3
[ montmorillonite] -
The formation of a thionium struc-,
ture rather than the ammonium form
(R-C-NHt) was also observed on protonation
of thioamides and thiourea
(KUTZELNIGG & MECKE, 1961;
JANSSEN, 1961).
Other features of this IR spectrum
seem to confirm the protonation of
the organic molecule and the formation
of the thionium structure:
(i) The strong band of the pure
compound at 1595 cm- 1 (solution)
and 1629 cm- 1 (solid state) assigned
to oNH2 coupled with vC-N, is
markedly reduced and this vibration
shifts to 1660 cm- 1 • A shift to higher
, frequencies of oNHz was observed on
S-alkylation and on S-protonation .
(JENSEN & NIELSEN, 1966; JANS­
SEN, 1961; KUTZELNIGG &
MECKE, 1961).
(ii) The band at 1392 cm- 1
(assigned to vC-N primarily) disappears
or shifts to higher frequen~
cies in this case being obscured by
ring vibrations. It has to be pointed
out that the shifted NHz bending lies
in the region of C=N stretching and
\ ±I
that the C=N stretching vibration
I \ .
is quoted at about 1680 cm- 1 (SO­
CRATES, 1980).
Protonation of amides on the oxygen
a tom rather than on the NHz

Interaction of Chlorthiamid with Al- and Ca-Montmorillonite 175
group was also found in acid montmorillonite
systems (TAHOUN &
MORTLAND 1966a).
Another significant feature is given
by the N-H stretching bands. In the
complex they are shifted to 3440 and
3340 cm- 1 from 3498 and 3378 cm- 1
(tetrachloroethylene solution). The
shift suggests an interactfon between
the NHz group of Chlorthiamid and
the oxygen of the silicate structure.
.The higher frequencies of NH2
stretching vibrations observed in the
clay-organic complex in comparison
with those in the solid state (where
asymmetric and symmetric NHz
stretching bands are at 3284 and
3138 cm- 1 ) could indicate that the
NH 2 group is involved in a lower degree
of environmental interactions.
The thin layer chromatography of
the extract of the Chlorthiamid-Al­
'-
montmorillonite complex revealed
the presence of Chlortiamid only.
On Ca-montmorillonite complex
the protonation ·of the C=S group
was not observed by IR analysis. The
most significant features of the IR
spectrum are (Fig. 2, spectrum «a»):
- the C=S stretching band shifts
from 711 cm- 1 to 7.02 cm- 1 • The shift
of vC=S to lower frequencies was
observed on S-methylation and on
formation of metal complexes of
thioamides (JENSEN & NIELSEN,
1966; FLINT & GOODGAME, 1968)
as a result of a reduction of the double
bond character of the C=S bond;
- the band at 1392 cm- 1 (C-N
stretching primarily) shifts to 1410
cm- 1 ;
- asymmetric and symmetric NHz
stretching bands are at 3440 and
3340 cm- 1 respectively as in the Al-
V
3500 3000 2500 2000
:Wavenumber (cm-1)
1600 1200 800 700
Fig. 2- IR spectra of Chlorthiamid-Ca-montmorillonite complexes: a) at r'oqm temperatilre, b) after
3 months storage in a desiccator at room temper.a,ture, c) after heating to 80 oc for 48 hours, then
cooling in air.

176 P. Fusi, M. Franci, G.G. Ristori
montmorillonite complex. The NH2
bending shifts to I626 cm- 1 from
I595 cm- 1 •
Therefore the Chlorthiamid seems
to be adsorbed on Ca-montmorillonite
by a coordination bond between
the C=S group and the exchangeable
cation.
The NH2 group of the organic molecule
seems to interact with the oxygen
of the silicate structure. The
absenc~ of protonation on Ca-clay
can be ascribed to the lower polarizing
power of Ca 2 + in comparison with
AP+. In metal ion-saturated montmorillonite
an ion-dipole interaction,
between the C=O group of amides ·
and exchangeable cation, was also
------- ObSe:fVeCf"(tAH6Ui~{ & M0RTLAN.D,
I966b).
Preliminary investigations on the
stability of all the Chlorthiamidmontmorillonite
complexes showed
that storage for 3 months at room
temperature in a desiccator affects
their IR spectra (Figs I and 2, spectrum
«b>>). A small but well evidenced
band, assigned· to a -C=N
stretching vibration of 2,6-
dichlorobenzonitrile, appears at
about 2250 cm- 1 • By contrast, no
change in the IR spectrum was
observed when the complexes were
stored for 3 months at room temperature
in an atmosphere with lOO%
R.H. These results show that Chlorthiamid
is partially and slowly decomposed
to 2,6-dichlorobenzonitrile
(Dichlobenil) in dry conditions and
seems to contrast with the findings of
BEYNON & WRIGHT (1972) suggesting
a rapid non biological decomposition
to Dichlobenil in soil.
The sample~studiecl.were-thenlieat~
ed in air to 80 oc for 48 hours. The
IR spectra of theCa- and Al-systems
are reported in Figs .I and 2 (spectra
«C>>): the C=N stretching bands are
well evidenced at 2250 cm- 1 for the
Al-complex and at 2258 cm- 1 for the
Ca-complex. The presence of the 2,6-
dichlorobenzonitrile (Dichlobenil)
and Chlorthiamid was confirmed by
thin layer chromatography of the
acetonic extract of the heated
organic-clay complexes as well as of
those dried and ~tored at room
temperature for 3 months (R£=0.25
for Chlorthiamid and R£=0.78 for
. Dichlobenil).
It should to be pointed out that the
pure Chlorthiamid is stable in the
absence of clay on heating to 80 oc for
48 hours and that an acidic hydrolysis
of thiobenzamide (hot HCl IN)
gives benzoic acid, H2S and NH 3
while an alkaline medium (hot KOH
IN) gives benzonitrile (HURD & DE
LA MATER, I961).
Therefore, in the acidic environment
typical of the montmorillonite
surface in our experiments, the decomposition
of Chlorthiamid to Dichlobenil
rather than to benzoic acid
was not expected.
IR spectra were also recorded to in2
vestigate the adsorption mechanism
of Dichlobenil on Ca- . and Almontmorillonite.
The C=N stretching
vibration of Dichlobenil (in the
solid state and in a tetrachloroethylene
solution at 2240 cm- 1 )
shifts to 2249 cm- 1 and 2250 cm-1

Interaction of Chlorthiamidwith Al- and Ca~Montmorillonite 177
when the organic molecule is
adsorbed on Al and Ca-clay respectively.
This shift indicates a coordination
of the nitrile group with.the clay
exchange cation through a water
bridge, Similar results were obtained
with benzonitrile (SERRATOSA,
1968).
On heating at 80 oc for 48 hours the
nitrile stretching band remains at
2250 cm- 1 in theIR spectrum of the
Al-system while shifts to 2258 cm- 1 in
the ea-system, probably indicating a
sttonger coordination of nitrile to the
cation. No degradation of Dichlobenil
was observed on heating the
respective AI- and Ca-clay complexes
at 80 oc for 48 hours.
REFERENCES
BELLAMY L.J ., 1980. The Infrared Spectra of Complex Molecules. Vol. II: «Advances in Infrared Group
Frequencies». Pp. 1-292, Chapman & Hall, London.
BEYNON K.l., WRIGHT A.N ., 1972. The fate of the herbicides chlorthiamid and dichlobenil in relation to
residues in crops, soils and animals. Residue Rev. 43, 23-53.
FLINT C.D ., GOODGAME M., 1968. Spectral studies of some transition-metal-thioacetamide complexes. J.
Chem. Soc. A, 750-752.
FuRMIDGE C.G.L., OSGERBY J.M,, 1967. Persistence of herbicides in soil. J. Sci. Food Agr. 18,269-273.
HuRD R.N., DE LA MATER G., 1961. The preparation and chemical properties of thioamides. Chem.
Rev. 61, 45-86. ·
JANSSEN M.J., 1961. The structure of protonated amides and ureas and their thi0 analogues. Spectrochim.
Acta 17, 475-485. ·"-
JENSENK., NIELSEN P.H., 1966. Infrared spectra ofthioamides and selenoamides. Acta Chem. Scand.
20, 597-629. .
KuTZELNIGG W., MECKE R., 1961. Spektroskopische Untersuchungen an organishen Ionen-Ill. Spectrochim.
Acta 17, 530-544.
MoRTLAND M.M., 1970. Clay-organic complex and interactions. Adv. Agron. 22, 75-119.
MoRTLAND M.M., RAMAN K.V ., 1968. Surface acidity of smectites in relation to hydration, exchangeable
cation and structure: Clays Clay MineJ;". 16, 393-398.
RAY A., SATHYANARAYANA D.N., 1974. A reinvestigation of the normal vibration of thioacetamide. Bull.
Chem. Soc. Japan 47, 729-731.
SERRATOSA J .M., 1968. Infrared study of benzonitrile-montmorillonite complexes. Am. Miner. 53, 1244-
1251-. . .
SocRATES G., 1980. Infrared Characteristic Group Frequencies. Pp. 55-56, J. Wiley & Sons, Chichester.
·
TAHOUN S.A., MoRTLAND M.M., 1966a. Complexes of montmorillonite with primary, secondary and
tertiary amides: I protonation of amides on the surface of montmorillonite. Soil Sci. i02, 248-254.
TAHOUN S.A., MoRTLAND M.M., 1966b. Complexes of rnontmorillonite with primary, secondary and
tertiary amides: II coordination of am ides the surface of montmorillonite. Soil Sci.·l02, 314-321.
VERLOOP A., 1972. Fate ·of the herbicides dichlobenil in plants and soils relation to its biological
activity. Residue Rev. 43, 55-103.

Abstracts
179
Interlayer Complexes of Lanthanide Vermiculite
with Organic Substances
P. OLIVERA, A. RODRIGUEZ
Departamento de Quimica Inorgfmica, Facultad de Ciencias, Universidad de Malaga, Apdo. 59, 29080 Malaga,
Espafta
The clay mineral used'in this work is vermiculite from Benahavis (Malaga) 1 •
The natural sample was pre-treated with 30% hydrogen peroxide'.
Lanthanide samples were obtained by a triple ionic exchange 3 monitored by
X-ray diffraction:
V-Mg--? V-Na--? V-nButNH 3 --? V-Ln
Exchange capacity values, and total amounts of lanthanides of the lanthanide
vermiculites, indicate that all lanthanide cations are localised in the
interlayer space as positive exchangeable cations:
Exchange capacity:
Total amounts o{lanthanides:
149 m.e. Ln
100 g V (900)
149 m.e. Ln
100 g V (900)
To determine the exchange capacity, lanthanides were extracted using
EDTA solutions•.
The complexes were obtained by placing the lanthanide vermiculites in
contact with organic substances in the vapour or liquid phase.
The organic substances were sorbed from the vapour phase, in appropriate
vacuum equipment 5 • The samples were previously dehydrated at 150°C for
5 hours. The complexes were obtained by sorption at 250°C with alkylamines,
aromatic amines, diamines, dimethylsulfoxide and other substances.
Sorption-desorption isotherms were made with n-alkylamines.
The composition of all the complexes was determined by the Kjeldahl
method, and elemental analysis of C,H.
The complexes were characterized using infrared and diffuse reflectance,
spectroscopy and X-ray diffraction.
Thermal stability was studied by differential thermal and thermogravimetric
analysis.
1
L6pez Gonzalez J. De D., Barrales-Rienda J.M., 1972. Caracterizaci6n y propriedades de una
vermiculita de Benahavis (Malaga). Ano Quim. 68, 247-262.
2
Gruner J.W., 1939. Ammonium mica sinthesized from vermiculites. Am. Miner. 24, 428-432.
3
Fripiat J.J. Personal communication.
4
Spirn P., Thesis D., 1965. MIT.
5
Gutierrez Rios E., Rodriguez Garcia A., 1961. Complejos interlaminares de montmorillonita con
acetona. An. R. Soc. esp. Fis. Quim. 57 (B), n. 2, 117-130.

180 Abstracts
Vermiculite-Organophosphorus Pesticides Interaction
M. SANCHEZ-CAMAZANO, M.J. SANCHEZ-MARTIN
Centre de Edafologia y Biologia Aplicada, C.Sl.C., Cordel de Merinas 40-52, Apdo. 257, 37008 Salamanca, Espaii.a
Previously, the interaction between organophosphorus pesticides (phosphates,
thiophosphates and dithiophosphates) and smectites in organic medium
was studied by X-ray diffraction and IR spectroscopy. A synthesis and
comparative study of the results obtained has recently been published 1 •
Kinetic and thermodynamic studies of the adsorption in aqueous medium
have been carried out 2 as well as on the catalytic hydrolysis process of some
pesticides by smecti tes 3 .
No references in the literature have been found concerning the interaction of
organophosphorus pesticides with vermiculite, a clay mineral also frequent
in soils. The present work studies the interaction between the organophosphorus
pesticides dichlorvos (0,0 dimethyl, 0-2, 2-dichlorovinyl phosphate)
and phosdrin (0,0 dimethyl, 0-(1-methyl-2-carbomethoxyvinyl) phosphate
and vermiculite. Studies were carried out in a) clay-liquid pesticide systems,
in order to discover the intercalation and interaction mechanisms (by X-ray
diffraction and IR spectroscopy), and b) clay-pesticide-water systems in
order to discover the effect of the clay on the evolution of the pesticides in
soil.
·-~~~------~~----------Ihe.Jollowing. Table includes the d(ooz) basal spacings of Beni-Buxera ho-
. moionic vermiculites treated with pesticides for periods of 15 days.
Samples
Dichlorvos
Phosdrin
d(Oo2)A I1A d(Ooi~ ~lA
Na 16.05 6.45 14.02 4.42
14.02* 4.42
K 10.77 1.17 10.77 1.17
Mg 16.05 6.45 16.05 6.45
Ca 16.05 6.45 16.05 6.45
Sr 16.05 6.45 16.05 6.45
Ba 13.08 3.48 13.08 3.48
13.08* 3.48 . 16.05'' 6.45
* After 2 months of treatment
The results shown in the Table indicate that the pesticide moiecules penetrate
into the interlayer space of vermiculite. The formation of complexes with a
defined d(ooz) spacing depends on the nature of the interlayer cation of the
silicate.
Studies on the adsorption of pesticides by homoionic vermiculites in
aqueous medium were begun with kinetic studies on their adsorption by Cavermiculite.
Equilibrium was reached at 72 hours. The data may be fitted to
a first-order kinetic process meaning that adsorption is a function of the
concentration of the solution.
Isotherms of the adsorption of the pesticides by homoionic samples were
obtained at 30°C and 45°C. All followed the empirical equation of Freundlich.
The values of the constants K and n, together with the distribution
constant Kd were determined. The values of the constant K and Kd were seen
to vary considerably as a function of the saturating cation of the adsorbent
and furthermore increased with the temperature of the system, while the
constant n only exhibited small variations.
From the adsorption isotherms obtained at both temperatures, the adsorp-

_ Abstracts 181
tion isosteric heats, ~Hiso. were obtained by applying the integrated equation
of Van't Hoff. The positive values obtained for ~Hiso in the adsorption of
both pesticides by the homoionic samples showed that in all cases the
process is endothermic.
1 Sanchez-Camazano M., Sanchez-Martin M.J., 1983. Factors influencing interactions organophosphorus
pesticides with montmorillonite. Geoderma 29, 107-118.
2 Sanchez-Martin M.J ., Sanchez-Camazano M., 1984. Aspects of the adsorption of azinphosmethyl
by smectites.J. Agric. Food Chem. 32, 720-725~ . . .
3 Sanchez-Camazano M., Sanchez-Martin M.J., 1983. Montmonllomte-catalyzed hydrolysis of
phosmet. Soil Sci. 136, 89-93.
Surface Acidity and Catalytic Activity
of a Modified Sepiolite
A. CORMA 1 , V. FORNES 2 , A. MIFSUD 2 , J. PEREZ PARIENTE 1
1
Instituto de Catft!isis y Petroleoquimica, C.S.I.C., Serrano 119,28006 Madrid, Espafla
2
Instituto de Fisico-Quimica Mineral, C.S.I.C., Serrano- 115 dpdo., 28006 Madrid, Espafla
"
Since the introduction of zeolites as catalysts, and based on the success and
unique properties related with their crystalline structure, several catalytic
groups have considered the possibilities of using clay minerals as catalysts.
Among the natural minerals there is an abundant crystalline magnesium
silicate (sepiolite) whose structure consists of flat laths (2: 1) joined together
at their edges. Channels of 11.5 X 5.3 A run the whole length of the fibre. In
some ways its channel structure is similar to that of mordenite, but natural
sepiolite has the big disadvantage with respect to zeolites that it is not able
to catalyze carbonium ion reactions due to the fact that its surface acidity is
negligible.
Here we present a modified sepiolite that has protonic acid sites which can
catalyze the isomer.ization and cracking of methylcyclohexene.
A natural sepiolite from Vallecas 1 , was used as the starting material. Procedures
for exchanging part of the cations located in the octahedral layer have
·.been reported 2·3 and in our case we have introduced Al 3 + cations (1.62 wt%
in Al 3 +) in part of the border octahe,dra.
To measure the acidity of the sample, wafers of 10mg/cm 2 were degassed for
2 hours at 200°C and a vacuum of 10- 4 torr in a grease-less conventional
pyrex IR cell. Subsequently;· 5 torr of pyridine were introduced in the cell at
room temperature, and five .minutes later the samples were degassed at
150°C under a vacuum of 10- 4 torr for 1 hour, and the spectra registered at
room temperature.
The natural sepiolite shows theIR bands of pyridine coordinated with Lewis
acid sites (1612, 1578, 1492 and 1450 cm- 1 )4, but no bands corresponding to
pyridinium ions. However, in the case of the aluminium exchanged sample,
besides an increase in the intensity of the bands associated with the presence
of Lewis acid sites, a band at 1550 cm- 1 characteristic of the pyridinium
ion-is observed. The stability and strength of the Br0nsted acid sites

182 Abstracts
generated is quite high since desorption temperatures up to 450°C at 10- 4
torr were required in order to completely desorb the pyridine.
The aluminium exchanged sample was-used-as-an-acidcatalystfoJ?-isomeriza-c
tion and cracking of methylcyclohexene (total conversion = 42.36%; crack
ing = 3.10). The acid sites generated in the sepiolite by exchanging Al 3 + for
the original Mg 2 + situated at the edges, are accessible to methylcyclohexene
molecules and strong enough to produce skeletal isomerization and cracking
at moderate temperatures. These results open a new possibility for the use of
such modified sepiolites directly as acid catalysts or as very convenient acid
supports for preparing bifunctional catalysts.
1
Fernandez T., 1972. Activaci6n de la sepiolita con acido clorhidrico. Bol. Soc. esp. Ceram. Vidr. 11,
365-375.
' Ioka M., Okkuchi Y., 1978. Supporting a metal on sepiolite in catalyst manufacture. Japan Kokai
53, 7592-7594.
3
Corma A., Fornes V., Mifsud A., Perez Pariente J., 1983. Procedimiento para la obtenci6n de un
silicato derivado de silicatos magnesicos cristalinos del tipo de la sepiolita. Sp. Pat. (in press).
4
Hughes T.R., Withe H.M., 1967. A study of the Surface Structure of Decationized Y zeolite by
Quantitative Infrared Spectroscopy. J. Phys. Chem. 71, 2192-2201.
Textural Modifications of Crystalline Magnesium
Silicates by Acid Treatment and
its Utilization in Catalysis
A. CORMA 1 , A. MIFSUD 2 , J. PEREZ', E. SANZ 1
1
Instituto de Catalisis y Petroleoquimica, C.S.I.C., Serrano 119, 28006 Madrid, Espaii.a
2 Instituto de Fisico-Quimica Mineral, C.S.I.C., Serrano- 115 dpdo., 28006 Madrid, Espaii.a
Some acid treated natural silicates have been used directly as catalysts in
the early stages of catalytic cracking. At present, the most common commercial
cracking catalysts are composed of 5-30% zeolite in a matrix of amorphous
silica-alumina or clay minerals. Recently, the processes treating high
boiling point hydrocarbons for which the catalyst life is very short, hav~
reopened interest for the development of low cost catalysts with special
textural characteristics.
In this work, we prepared a series of catalysts based on natural silicates
abundant in Spain.
A sepiolite (Vallecas) and two palygorskites of different composition and
origin (Serradilla and Torrej6n) were used. The samples were treated with
HCl at different conditions of pH, temperature and reaction time. Nickel
supported catalysts were prepared by impregnation with Ni(N0 3 ) 2 or
Ni(HC00) 2, calcined at 450°C for 3 hours and reduced in an H 2 atmosphere
at the same temperature for 16 hours; the average size of the Ni metal
particles was determined.
After the acid attack, t!J.e surface area increased up to 450 m 2 /g for the

Abstracts 183
- sepiolite and 100-200 mLfg for palygorskite. The latter is more stable under
acid attack. The rate equation for extraction of octahedral cations is: v =
k(H+)a; the activation energies are 16 kcal/mol for sepiolite and 4 kcal!mol
for palygorski te. The increase in metal dispersion and degree of reduction of
NiO with the amount of Mg extracted is related to the surface area of the
carrier silicate.
Interaction of Macrocyclic Compounds, Crown Ethers
and Cryptands, with Layer Silicates:
Adsorption Isotherms and Kinetics
B. CASAL, E. RUIZ-HITZKY
Instituto de Fisico-Quimica Mineral, C.S.I.C., Serrano 115 - dpdo., 28006 Madrid, Espafla
In a previous study 1 , it 'was shown that macrocyclic compounds, crown
ethers and cryptands, can be intercalated between the layers of smectites
and vermiculites saturated with different metal ions, including the alkaline
cations. The macrocyclic compounds replace water molecules and coordinate
directly with the interlayer metal cations. X-ray diffraction and infrared
studies 2 indicate that, in most cases, the intercalated ligands lie flat on
the silicate surface either in one- (

184
Abstracts
Na +-montmorillonite
Na + -montmorillonite
Na + -montmorillonite
Macrocyclic
compound
15-crown-5
18-crown-6
C(222)
Monolayer capacity Xm (mmol/100g)
____ J

Section 11
Geology and Genesis
. I
• I

---------
r

Miner. Petrogr. Acta
Vol. 29-A, pp. 187-196 (1985)
Hydrothermal Solutions Related to Bentonite Genesis,
Cabo de Gata Region, Almeria, SE Spain
E. CABALLERO, E. REYES, J. LINARES, F. HUERTAS
Estaci6n Experimental del Zaidin, C.S.I.C., Profesor Albareda I, 18008 Granada, Espaiia
ABSTRACT - In the Neogene volcanic region of Cabo de Gata (Almeria, SE
Spain) hydrothermal alterations are present, affecting tuffaceous materials,
ignimbrites and agglomerates, and giving rise to thick bentonite deposits.
Samples (219) were taken from 39 bentonite deposits spread along the Sierra
de Gata (north and south) and Serrata de Nijar. Extractable Na +, K+, Ca 2 +,
Mg 2 +, CC so~-, CO~- and HCO:l were analyzed in order to study whether
or not these species could reflect those of the original mineralizing solution.
From the statistical analysis of the data (Factor analysis - R-mode, and
multiple regression) the existence of the following associations were found:
Cl-- Na+, Soi-- Na+, HCO:l -Ca 2 +. Generally, the Cl- -Mg 2 + correlation
is negative.
These facts seem to exclude a marine origin for the alteration solution and
favour the idea that these solutions result from a system of meteoric waters
heated by a geothermal cycle, this being in accordance with stable isotope
geocherriistry of bentonites.
Solutes must derive from wall-rock hydrolytic reactions :previous to the entrance
of these solutions into the cinerite layers. Mg2+ and K+ must originate
from the metamorphic basement of volcanic materials and from normal
hydrolisis during infilt'ration of the solution through the Sierra Alhamilla
and Sierra Cabrera, collecting body of the local aquifers. Na +, Cl- and SO~must
derive, from the interaction between solutions and volcanic materials,
while Ca 2 + and HC03- must be related, partially, to volcanic and metamorphic
complexes.
'
The concentration ratios

188 E. Caballero, E. Reyes, J. Linares, F. Huertas
sive alteration to smectite, forming
thick bentonite deposits. In the first
case, the altering solution must have .
been slightly more acid than in the
second one (REYES, 1977).
Most authors relate the origin of
these bentonites to the action of a
hydrothermal solution, but few
attempts have been made to specify
the origin of the solutions. Recently,
LEON;£_ tq _aJJ12,~~),_EY._~t!,!gyi_I1g_the
fractionation of stable hydrogen and
oxygen isotopes in these bentonites,
concluded that the hydrothermal
solutions were of meteoric origin,
acting at temperatures of about 70 oc
in the Sierra de Gata and of 40 oc in
the Serrata di Nijar.
L~
CG
MM
•
e LHe
CL
•cAm
u•
E e
•
e LPN
LPe
c
Volcanic rocks
Miocenic limestones
Quatern~ry
Triassic
0
10 km
Fig. 1- Sampling location. LT: Los Trances; RC: Rinc6n de !as Caleras; PU: Pozo Usero; ML: Mata
Lobera; MA/B: La Valentina; V: Majada de !as Vacas; RM: Rambla Mendez; VR: Vieja Rambla;
PM: Palma del Muerto; PCl/2: Pecho de Ios Cristos; R: Rodalquilar; LA: Los Albacetes; CT: Cerro
Tostana; CA: Collado del Aire; CC: Cerro Colorado; CE: Cerro de Estrada; CL: Cortijo de la Loma;
CAm: Cerro Amatista; BF: Boca de Ios Frailes; MM: Morr6n de Mateo; LI: La Isleta del Moro;
LB: La Barranquilla; LC: La Capitana, E: Escullos; LH: Las Hermanicas; CG: Cortijo del Gitano;
T: Toril; LM: La Marranera; LPN: Loma Pelada Norte; LP: Loma Pelada; C: Caliguera; CM: Cerro
del Marchal; VB: Vela Blanca; EC: El Corralete.

Hydrothermal Solutions Related to Bentonite-Genesis ... 189
The purpose of this study was to
infer the composition of the hydrothermal
solution from the analysis of
ions extracted from bentonites,
assuming that the salts are the vestiges
left by solutions filling the interstitial
spaces of the pyroclastic
mass during the alteration processes.
Numerical analysis of the data was
performed with an HP 9816 Microcomputer.
Programs were prepared
by 'E. BARAHONA (pers. comm.) following
criteria and algorithms of
DRAPER & SMITH (1966), COOLEY
& LOHNES (1971), DAVIS (1973),
and JORESKOG et al. (1976).
Materials and experimental methods
Experimental results and discussion
Bentonite samples (219) were
selected from 34 localities (Fig. 1).
The samples located to the north of
Cabo de Gata, have been previously
studied by RE YES (1977); the rest
were purposely taken for this study.
The sampling sites do not always correspond
to important deposits, since
many times samples were collecte'd
from small outcrops of altered volcanic
material. The sampling sites were
chosen with a view to obtain a more
general insight into the nature of the
hydrothermal solutions.
Cations were extracted by percolation
with 1N ammonium acetate at
pH 7; before extraction, the ground
samples were mixed with , to
accelerate the leaching process. Na+
and K+ were determined by flame
photometry, and Ca:z+ arid Mg 2 + by
atomic absorption~ CEC was calculated
from the absorbed NH4, determined
by the Kjeldahl method.
Anions were extracted with distilled
water from another sample aliquot.
Cl- was determined by Mohr' s method,
so~- by turbidimetry and eo~- and
HC03 by acidimetry.
Listed in Table 1 are the mean
values of the variables analyzed for
28 sampling localities, totalizing 210
samples. The localities having a single
sample were excluded. Nevertheless,
these were included in the general
statistical analysis.
The data obtained were studied,
starting from the correlation matrix,
"-by R-rriode Factor Analysis with Varimax
rotation. Five factors, accounting
for 85.8% of the total variance,
were judged to be significant. A simplified
varimax loading matrix is
listed in Table 2.
The first facto:r has high loading on
eo~-, HC03 and Ca 2 +. This association
seems to be somewhat forced by the
particular chemism of the bentonites
from Cabo de Gata, which are a very
numerous subset of the total sample
set. The source of these anions should
be related to the metamorphic rocks
of the volcanic basement and to those
from, the Sierra Alhamilla and Sierra
Cabrera, to the north of the bentonite
deposits, these being the main
sources of aquifers forming the
hydrothermal solutions. HEM (1970)
points to these ions as major compo-

~- -~
··-
19Q
E. Caballero, E. Reyes, J. Linares, F. Huertas
TABLE 1
Mean values of the variables analyzed
Ca 2 + Mgz+ Na+ k""
so-:r=~~ ~ 'coj-
'~- -·.
C03H- cl- CEC
MA 36.13 47.20 36.13 2.73
MB 29.48 49.73 46.59 .3.54
V 35.32 35.68 44.68 3.08
PU 28.70 53.10 36.20 1.90
RC 17.58 40.42 31.50 1.75
LT 31.86 55.09 13.33 0.57
E 34.80 28.40 33.00 1.80
MM-1 32.80 14.60 40.60 2.60
MM-2. 32.87 20.87 42.75 1.62
LP 39.00 35.00 24.50 2.50
LH 35.50 27.50 31.50 1.00
CG 24.00 26.00 50.67 1.00
CM 45.75 29.25 46.25 1.00
c 24.50 22.75 58.75 1.50
EC 23.20 8.40 30.00 1.00
LC 23.00 16.50 29.50 1.50
VB 27.50 16.00 86.50 5.00
CAm 22.50 16.00 36.50 1.50
CL 61.50 13.50 36.50 2.50
T 22.00 18.00 21.00 1.00
R 25.50 13.50 26.00 0.50
LM 24.00 12.50 19.50 1.50
·- ~-~--~VR- -----~-E0"75 --19:50 . 19.75 1.50
RM 31.67 34.67 44.67 5.00
cc 13.20 27.40 53.80 4.00
CA 29.25 . 28.25 26.62 2.50
l CT 24.33 34.66 52.00 1.00
PC-1 19.00 16.60 32.40 2.20
PC-2 24.00 29.20 49.80 2.60
PM 16.60 19.60 48.60 3.60
0.76 0.00 8.58 0.54 110.07
0.46 0.00 15.36 0.59 110.02
2.66 0.88 19.81 1.12 90.80
1.71 1.24 21.62 0.76 101.60
1.10 0.09 1.84 1.27 84.00
0.52 0.14 10.30 0.17 93.14
0.36 0.04 1.14 3.80 94.20
0.30 0.26 4.02 0.88 . 83.00 .
0.84 0.06 1.54 7.62 86.87
0.05 0.00 0.70 4.00 99.50
0.60 0.00 0,25 16.30 81.00
1.40 0.00 0.97 13.13 88.67
0.85 0.20 2.30 6.80 112.25
1.10 0.05 1.17 24.07 79.25
1.16 0.00 0.64 31.88 24.80
1.20 0.00 0.35 17.80 57.00
1.70 0.00 0.45 12.90 125.50
0.65 0.15 2.35 1.05 75.00
0.00 0.15 2.05 0.00 112.00
0.75 0.10 0.25 8.60 58.00
1.80 0.00 0.20 10.00 58.50
2.30 0.00 0.60 8.85 45.00
1.15 0.00 0.60 7.00 48.50
1.13 0.00 1.53 26.97 85.00
1.04 0.08 1.48 6.22 95.80
0.77 0.12 1.16 5.06 76.37
2.03 0.00 0.57 34.47 76.00
1.32 0.00 0.42 13.66 58.60
1.08 0.00 0.78 6.24 99.00
1.34 0.00 0.86 8.28 82.80
nents in natural waters infiltrated
through mica schists.
The second factor is concerned
with Mg 2 + and cation exchange
capacity. This grouping is also influenced
by the samples from Cabo de
Gata, in which Mg 2 + is the chief ex-·
changeable cation, though the rest of
the samples also contain sizeable
quantities. A point to be stressed is
that in this factor, Mg 2 + and Cla'ppear
with opposite signs, probably
implying that they originated from
different sources. Mg 2 + likely derives
TABLE 2
Simplified varimax loading matrix
F1 Fz F3 F4
coj- 0.832 Mgz+ 0.872 K+ 0.916 Cl- 0.851
Ca 2 + 0.794 CEC 0.838 Na+ 0.798 Na+ 0.391
HC03- 0.712 cl- ~0.304 Hco3- ~0.373
Mgz+ -0.300
F1 = 20.58%, F 2 = 20.01%, F3 = 19.23%, F4 = 13.69%, F 5 = 12.28%;
Total Explained Variance = 85.78%
Fs
so~- 0.920
Hco3- 0.266
Na+ 0.242
Ca 2 + -0.273

Hydrothermal Solutions Related to Bentonite Genesis ... 191
from chlorites and
micas, present in metamorphic rocks
from the basement and from the Sierra
Alhamilla and Sierra Cabrera,
whereas cl- might come either from
salts ·impregnating the surfaces of
volcanic and metamorphic rocks, or
from glassy phases present in the
pyroclastic materials (ELLIS &
MAHON, 1964; HEM, 1970).
The third factor has strong loadings
in Na+ and K+. This is a typical
assemblage of hydrothermal systems,
especially in the case of rock wall alteration.
The fourth factor is loaded with respect
to Cl- an,d Na+. This is also a
typical association of hydrothermal
solutions. Cl- could come either from
metamorphic schists, outcropping to
the north, or from pyroclastic materials,
as mentioned above.
The last factor includes SOi- and
also, with lesser loadings, HC03 and
Na+.
Even though the results of factor
analysis are strongly influenced by
the samples of the Sierra de Gata,
some information about possible constituents
of hydrothermal solutions
Sierra Cabrera
Sierra Alhamilla
Las Negras .,
":J'lJ
10 15 km
Fig. 2- zo;es showing differences in ionic compositions.

192 E. Caballero, E. Reyes, J. Linares, F. Huertas
was obtained. Thus,· two types of
solutions must have. been acting, one
dominated by HC03 and the other by·
cl-. so~- seemingly appears to be
an accessory component.
In order to verify these differences
in the chemistry of the solutions, the
samples from the 30 most important
deposits were grouped into zones.
Three groups were made: Sierra de
Gata, Serrata de Nijar and the South
Zone, cited in order of increasing distance
from the Sierra Alhamilla and
Sierra Cabrera, probable recharge
. sites of the meteoric waters that
turned into hydrothermal solutions
(Fig. 2).
______ Jj~t{!d in_ Table _3 _are the mean
values of the variables determined
for .the three groups. Values for the
anions are to be ascribed to soluble
salts, but those for the cations correspond
to both, the soluble and the exchangeable
ones. A separate determination
of soluble cations was not
attempted so as not to disturb the exchange
complex. Nevertheless, the
statistical analysis of data allowed
both contributions to be separated. It
can be-also-observed· in-l'able·-·3 that
the sum of the cations is systematically
two or three units lower than that
of the anions plus the CEC. These differences
may be due to a small anion
exchange capacity.
The correlation matrices for
the three groups are. given in Table 4.
In the case of Sierra di Gata, the
following positive and highly significant
correlations are to be noted:
Ca 2 +-HC03,Na+-Cl-,Na+-SO~-,
K+- Cl- and Na+- K+. Based on
these correlations, soluble salts were
quantified by discounting as much
Na+ as Cl- plus SO~- were present,
and as much Ca 2 + as the existing
HC03. The contribution of K+,
although existing, was disregarded as
a minor one. The results so obtained
are listed in Table 5, where the ions
are divided into soluble and exchangeable
ones.
In the case of Serrata de Nijar,
strong correlations exist between
Ca 2 +- Mg 2 +, Mg 2 +- HC03, Na+ ~
K+, Na+- so~-, Na+- cl-, sm--
TABLE 3
Mean values of the variables determined for the Sierra de Gata, Serrata de Nijar and South
Zone groups
Sierra de Gata Serrata de Nijar South Zone
Ca 2 + 29.83 22.58 30.07
Mgz+ 46.87 27.20 19.90
Na+ 34.74 43.99 37.25
K+ 2.26 2.98 1.71
soJ- 1.20 1.24 1.01
eo~- 0.39 0.03 0.05
HC03 12.92 0.97 1.15
er- 0.74 14.41 10.27
CEC 98.27 81.93 78.18
L Cations 113.70 96.75 88.93
L Anions+ CEC 113.52 98.58 90.66

Hydrothennal Solutions Related to Bentonite Genesis ... 193
TABLE 4
Correlation matrices for the Sierra de Gata, Serrata de Nijar and South Zone groups
VI
V2
V3
V4
Sierra de Gata
vs
V6
V7
vs
V9
V1
V2
V3
V4
vs
V6
V7
vs
V9
1.000
-.223
-.094
-.113
-.007
.569
.644
-.132
-.OS2
-.223
1.000
-.11S
-.176
-.270
-.31S
-.26S
.6S1
-.2S3
-.094
-.11S
1.000
.7S7
.314
-.12S
.141
.442
.409
-.113
-.176
.7S7
1.000
.1S4
-.OS2
.OS1
.343
.206
-.007
-.270
.314
.1S4
1.000
.026
.09S
-.069
.439
.569
-.31S
-.12S
-.OS2
.026
1.000
.S73
-.37S
.041
.644
-.26S
.141
.OS1
.09S
.573
1.000
-.190
.039
-.132
.6S1
.442
.343
-.069
-.37S
-.190
1.000
.-.073
-.OS2
-.2S3
.409
.206
.439
.041
.039
-.073
1.000
V1
V2
V3
V4
Serrata de Nijar
vs
V6
V7
vs
V9
V1
V2
V3
V4
vs
V6
V7
vs
V9
1.000 .S23
.S23 1.000
-.390 -.021
-.334 . -.34S
-.297 -.19S
.277 .196
-.OOS .407
.16S. .:S16
.020 .096
V1
V2
-.390
-.021
1.000
.61S
.421
-.OSS
-.034
.634
.347
V3
-.334
-.34S
.61S
1.000
.11S
-.141
.039
.449
-.147,
V4
-.297
-.19S
.421
.11S
1.000
-.163
-.360
-.1SO
.6SS
"
South Zone
vs
.277
.196
-.OSS
-.141
-.163
1.000
.2S8
.106
-.140
V6
-.OOS
.407
-.034
.039
-.360
.2SS
1.000
.299
-.40S
V7
.16S
.S16
.634
.449
-.1SO
.106
.299
1.000
-.13S
vs
.020
.096
.347
-.147
.6S8
-.140
-.408
-.13S
1.000
V9
V1
V2
V3
V4
vs
V6
V7
vs
V9
1.000
.207
.111
.243
-,.242
.1S1
.193
.639
-.21S
.207
1.000
.113
-.174
-.092
.011
-.031
.460
.OS9
.111
.113
1.000
.303
.2S9
.032
.oso
.609
.301
·.z43
-.174
.303
1.000
-.1S2
-.040
.191
.3S3
-.193
-.242
-.092
.2S9
-.1S2
1.000
-.3S7
-.47S
-.17S
.SS3
.1S1
.011
.032
-.040
-.3S7
1.000
.SOS
.172
-.3SS
.193
-.031
.oso
.191
-.47S
.SOS
1.000
.. 218
-.441
.639
.460
.609
.3S3
-.17S
.172
.21S
1.000
-.313
-.21S
.OS9
.301
-.193
.SS3
-.3SS
-.441
-.313
1.000
Cl-. Moreover, all cations are significantly
related to CEC.
In the South Zone the following
correlations were obtained: Na+ -
K+, cm-- HC03, Na+- SOi-, Na+
- Cl- and Cl- -,- so~-. There is also a
significant correlation between cations
and CEC. On the basis of these
correlations both soluble and exchangeable
cations were calc~lated
using the same method as that used
in the case of the Sierra 'de Gata
group (Table 5). From the data in this
table it can be seen that two types of
cheml.sm actually occur. The first one
dominated by HC03 and Ca 2 + in the
Sierra de Gata, and the second one
ruled by Cl- and Na+, in the two remaining
zones.
As stated above, the soluble salts

194 E. Caballero, E. Reyes, J. Linares, F. Huertas
TABLE 5
Exchangeable cations an'!so!l!ble }~ll!_~al:?e~
Exchangeable C:ations (meq/100 g)
Sierra de Gata Serrata de Nijar South Zone
16.52 22.55
29.47
46.87 26.23
19.30
32.80 28.34
25.97
2.26 2.98 1.71
Soluble Ions (meq/100 g)
Ca 2 +
Mgz+
Na+
K+
cl­
so~­
HCO:l
cot-
Sierra de Gata Serrata de Nijar South Zone
0.60
0.60
11.28
13.37
t
1.94
t
0.74
1.20
12.92
0.39
0.03
0.97
15.65
t
14.41
1.24
0.97
0.03
t
10.27
1.01
1.15
0.05
Soluble Ions (g/1)
Sierra de Gata Serrata de Nijar South Zone
81.92
3.68
0.55
19.96
3.43
t
2.02
4.42
60.63
0.90
153.32
0.16
0.90
27.69
t
39.22
4.56
4.58
0.06
77.17
t
27.97
3.54
5.37
0.12
61.19
-Ca2 +
Mg2+
Na+
K+
Cl­
so~­
HCO:l
cott:
traces
are assumed to be the dried. vestiges
of solutions that filled the interstitial
pore space during alteration. If so, it
would be desirable to express the results
obtained as either mg or g per
liter ofsolution, rather than as meq
per 100 grams of sample weight. To
do so, the true particle density and
the bulk density of the undisturbed
bentonite samples were determined.
The average true particle density
found was 2.7 and the bulk density,
2.0. According to these values, the
average porosity was 26%, indicating
that 100 g of sample will contain a-
bout 13 cm 3 of pore space. Therefore,
the values in meq/100 g can be converted
to meq per !iter by multiplying
them by the conversion factor of
76.92; meq/1 are then easily transformed
to grams per li ter. The results
of these calculations are also shown
in Table 5. These results clearly are
not compatible with a real situation,
since a .direct precipitation of calcite
would have to occur in nearly every
case. Taking into account the solubility
of calcite at 60 oc (CLARK, 1966),
a dilution factor of 700 should be applied
to the values found for the Sier-

Hydrothermal Solutions Related to Be;;toniteGenesis ... 195
ra de Gata, so as to avoid the precipitation
of this mineral. For the
Serrata de Nijar and the South Zone,
the dilution factors would be 2 and
30, respectively.
After introducing the dilution factor,
the solution of the Sierra de Gata
happens to be the less concentrated,
and tends to resemble a natural water
having infiltrated through mica
schists (HEM, 1970). This solution
would be enriched in Cl- and Na+ by
reacting with volcanic materials in
the course of its displacement towards
the Serrata de Nijar. In the
South Zone, mixing with water of a
lesser ionic strength must have taken
place.
Assuming that exchangeable cations
were in equilibrium with this
solution, some interesting ,· conclusions
can be drawn. For instance, it
may be noted in Table 5 that Ca 2 + increases
from the Sierra de Gata towards
the South Zone, while the
opposite is true for Mg 2 + and Na+.
The increment in CaH may be due to
the hydrolysis of volcanic materials
as the solutions moved southwards.
Plagioclases in this region are mainly
calcic, and could provide enough
Ca 2 + to account for this increase. The
decrease in Mg2+ content is fairly significant
and seemingly indicates that
its source is to the north. The solution
is more impoverished in Mg 2 + as'
smectite is formed as a product of
hydrolysis. This decrease is even evidenced
by the total amount of Mg
present in the bentonites. Thus, their
MgO content is 5.44% in the Sierra de
Gata (REYES, 1977), 3.33% in Serrata
de Nijar (CABALLERO, 1982) and
1.77% in the South Zone (CABAL­
LERO, 1985).
Coming back to Table 5, it can be
noted that the composition of the
solutions for the Serrata de Nijar and
South Zone are mainly rich in Cland
Na+. However, Na+ tends to decrease
in the exchange complex towards
the south. This may be due to
the selectivity of Ca 2 + against Na+
(BOLT & BRUGGENWERT, 1978).
Thus, even though the solution is rich
in Na + and poor in Ca2+, the exchange
complex is progressively enriched in
the latter. In the Sierra de Gata, Mg 2 +
is absorbed in a specific way because
of its smaller ionic radius.
In order to verify if the composition
of these solutions is in accordance·'
with the average alteration temperatures
for each zone, we attempted to
use the Na-K-Ca geothermometer,
proposed by FOURNIER & . TRUES­
DELL (1973). The difficulty encountered
in our case was the lack of reliable
data for the very small K+ contents
found in our samples.
The selected option was to operate
in the opposite sense, calculating
how much K+ should be introduced in
the geothermometric expression so
that Ca 2 + and Na+ would be in equilibrium
with an average temperature of
70 oc for the Sierra de Gata and 40 oc
for Serrata de Nijar and the South
' Zone. The results of these calculations
show that the K+ contents would
be around 0.05, 0.08 and 0.05 meq K+f
100 g for the Sierra de Gata, Serrata
de Nijar and South Zone respectively.
The concentrations found are so

196 E. Caballero, E. Reyes, J. Linares, F. Huertas
small that they support the convenience
of their suppression and show,
on the other hand, that, as a matter of
fact, the inferred solutions should be
in equilibrium with the temperatures
previously inferred from . isotopic
fr::tctionation;
A final subject to be considered is
the overall dynamics of the solutions,
although it has already been treated
in part. It may be assumed that the
solutions came from meteoric waters
recharged at the metamorphic masses
of the Sierra Alhamilla and Sierra
Cabrera lying north of the bentonite
deposits. In addition to the previously
cited isotopic data reported by
_______ L~Q_NE__~L a_[ •.( 19_8~), _!l_lis ~!uciy provides
further evidence, such as the
negative correlation between Mg 2 +
and Cl-, sm- and HC03, that excludes
a mar1n~or:iginJ:or~these solutions,
since, if this were the case, the
correlations would be positive.
Finally, if we assume a pH value for
the solutions close to neutrality, then
the log Na/H would be close to 6.
When plotting these values in HEM­
LEY et al.'s diagram ( 1971), for
temperatures near to 60 °C, we find
that they fall into the stability field of
montmorilloni te.
It may be concluded that the
hydrothermal solutions operating in
the region of Cabo de Gata had compositions
in agreement with a
meteoric origin and with the alteration
temperature, and which were in
equtlibri~m with· montmorillonite.
REFERENCES
BOLT G.H., BRUGGENWERT M.G.M., 1978. Soil Chemistry. A. Basic Element. Elsevier, Amsterdam.
·CABALLERO E., 1982. Composici6n Quimica y Mineral6gica de les Bentonitdsde la Serrata de Nijar
(Almeria). Thesis, University of Granada, Spain.
CABALLERO E., 1985. Quimismo del Proceso de Bentonitizaci6n. Ph.D. Thesis University of Granada,
· Spain.
CLARK S.P., 1966. Handbook of Physical Constants. Geol. Soc. Amer. Inc. Mem. 97, 1-587.
CooLEY W.W., LOHNES P.R., 1971. Multivariate Data Analysis. J. Wiley & Sons, New York.
DAVIS J.C., 1973, Statistics and Data Analysis in Geology. J. Wiley & Sons, New York.
DRAPER N.R., SMITH H., 1966. Applied Regression Analysis. J. Wiley & Sons, New York. .
ELLIS A.J., MAHON W.A.J., 1964. Natural Hydrothermal Systems and Experimental Hot-Water/Rock
Interactions. Geochim. Cosmochim. Acta 28, 1323-1357.
FoURNIER R.O., TRUESDELL A.H., 1973. An EmpiricalNa-K-Ca Geothermometer for Natural Waters.
IGeochim. Cosmochim. Acta 37, 1255-1275.
HEM J.D., 1970. Study and Interpretation of the Chemical Characteristics of Natural Water. Geol.
Surv. Water-Supply Paper 1473.
HEMLEY J.J., MoNTOYA J.W., NIGRINI A., VINCENT H.A., 1971. Some alteration reactions in thesystem
CaO-Al 2 0TSiOrHzO. Soc. Min. Geol. Japan, Special Issue n. 2, 58-63.
J6RESKOG K.J., KLOGAN J.E., REYMENT R.A., 1976. Geological Factor Analysis (Methods in
Geomathematics-I). Elsevier, Amsterdam.·
LEONE G., REYES E., CORTECCI G., POCHINI A., LINAREO. J., 1983. Genesis of Bentonites from Cabo de
Gata, Almeria, Spain: A Stable Isotope Study. Clay Minerals 18, 227-238.
REYES E., 1977. Mineralogia y Geoquimica de las Bentonitas de la Zona Norte de Sierra de Gata
(Almeria). Ph.D. Thesis, University of Granada, Spain.

Miner. Petrogr. Acta
Vol. 29-A, pp. 197-203 (1985)
The Origin of Palygorskite in Villamayor
Sandstone, Salamanca, Spain
MA VICENTE 1 , J. VICENTE-HERNANDEZ 2
1
U .E.I. Mineralogia de Arcillas, Centro de Edafologia y Biologia Aplicada, C.S.I.C., Cordel de Merinas 40-52,
Apartado 257, 37008 Salamanca, Espana
2 Departamento de Quimica Analitica, Facultad de Ciencias, Universidad Aut6noma de Madrid, Canto Blanco,
28049 Madrid, Espail.a
ABSTRACT- The origin of palygorskite in Villamayor Sandstone (Salamanca,
Spain) was studied. Scanning electron microscopic observations on the morphology
and location of palygorskite fibres in the sandstone and the chemical
analysis of the water that flows through the quarry, indicate that the formation
of palygorskite occurs in situ, and after the deposition of coarse grained
components of the sandstone skeleton. The palygorskite was located mainly
in three sites: in intergranular pores, in joints and on the surface of coarse
grains,always with a preferred orientation indicating the manner in which it
was formed. Water that moistens the quarry is a medium in which palygorskite
is stable as indicated by its pH and chemical composition.
Introduction
Neoformation, and transformation
from other silicates are the two widely
accepted processes for the genesis
of palygorskite. MILLOT · (1964) reported
that palygorskite, abundant in
the French Tertiary, is a result of
neoformation from solutions derived
from continental weathering. This interpretation
agrees with that offered.\
by ROGERS et al. (1954) for certain
Australian palygorskites. MILLOT et
al. (1969), studying neoformed palygorskite
of eastern Morocco, indicated
the analogy between pedogenic
conditions and basic chemical sedimentation.
ISPHORDING (1973)
offers three possible origins for palygorskite
in lacustrine and marine
sediments, and suggests that. the
majority have been formed as a result
of neoformation. PEI-LIN-TIEN
(1973), SINGER & NORRISH (1974),
WATTS (1976), YAALON & WIEDER
(1976), HASSUOBA & SHAW (1980),
and SINGER (1981) also support
neoformation of palygorskite.
Acc~rding to TRAUTH (1977) the
'ratio of dissolved Si to available Mg
controls the precipitation of palygorskite
fibres. Palygorskite is found
in chemical sedimentation zones
where the detrital influence is considerable,
or in detrital zones where

198 M.A. Vicente, J. Vicente-Hernandez
the process of chemical sedimentation
exists.
GALAN & FERRERO (1982) attrib~
uted neoformation, and transformation
from detrital illites as a two fold
origin of the Lebrija Palygorskite,
while MARTIN POZAS et al. (1981,
1983) suggest that initial palygorskite
formation could be due to the
transformation of smectite in a
magnesium-rich medium, and the
subsequent growth of crystals by
neoformation. A detailed study carried
out by SANCHEZ-CAMAZANO
& GARCIA RODRIGUEZ (1971) on
soils of the same area reported in the
present paper, showed the presence
-----~------,cof detrit~l_:p~!ygo!"skite in soils de­
. veloped both from limestones and
sandstones. In addition, the analysis
of the < 2 f.Lm fractions of certain
sandstone and limestone materials of
the zone, als9 incl._if.

-
The Origin of Palygorskite in Villarnayor Sandstone ... 199
current activity (ARRESE et al.,
1965). They contain an abundance of
unstable minerals (feldspars, biotite
etc.) but the chemical weathering
which they have undergone is low, indicating
that the minerals have.
undergone relativtlly very little transport
and have been compacted under
conditions of low destabilization.
The sandstone is highly porous
with a predominance of the coarsegrained
fraction over the matrix
mineral, the latter never is greater
than 20%. Quartz (40-70%) and feldspars
(10-30%) are the major components,
while micas, tourmaline,
kyanite, and garnet occur in smaller
amounts. The cementing material is
mainly palygorskite with minor
amounts of smectite. Finely divided
micas and kaolini te occur in small
quantities, together with traces of
chlorites and Fe-hydroxides
(VICENTE, 1983). Analytical techniques
employed in the present study
were X-ray diffraction (using a Philips
diffractometer and Ni-filtered Cu
Ka radiation), scanning electron microscopy
(using a JEOL, model JSM
35) and chemical analysis by atomic
absorption. Sandstone samples were
gently ground and fractionated into
< 20 f.Lm and < 2 flm particle sizes.
Mineralogical identification by XRD
analysis was conducted following the
method reported by ROBERT (1975).
The interior of the quarries is
almost always humid, but the flow of
water through them is so slow that
water collection in situ is literally impossible.
This was done, t~erefore, by
collecting large quantitie-s of wet
samples and extracting the water by
suction, using a vacuum pump (0.2
mm vacuum). Si, AI, Mg, Ca, Na, Fe
and Mn contents of the· water samples
were determined as well as the
pH.
Results and discussion
X-ray diffraction patterns of the <
20 f.Lm and < 2 flm fractions showed a
diffraction effect at 10.4 A, as well as
weaker diffraction at 6.35, 5.40, 4.47
and 4.24 A which corresponded to
palygorskite. In addition to palygorskite,
the mineralogical composition
also revealed the presence of smectite
and, in lesser quantities, finelydivided
micas, kaolinite and other
minerals as observed in previous studies
(VICENTE, 1983). Scanning electron
microscopy of the sandstone revealed
the presence of abundant
fibres of palygorskite in three sites: in
joints, in pores and on the surface of
coarse grains, as can be observed in
Fig. 2. Microphotograph A represents
a zone covered by fibres. In spite of
forming' an irregular network, as a
whole they do have a preferred
orientation, from the top-right to the
bottom-left, following the fissure
which could serve for water circula-
·. tion. In the middle, a big pore can be
'seen, partly covered by bundles of
fibres. In microphotograph B a big
-pore can be seen, covered by a network
of fibres. The precipitation and
growth of these fibres may perhaps
be related to the water level changes
within the pore. With evaporation,

200 M.A. Vicente, J. Vicente-Hemtmdez
8
D
F
Fig. 2- SEM micrographs of sandstone samples. A single line indicates 10 J.lm, while a double line
(micrograph E) indicates 100 J.lm.

The Origin of Palygorskite in Villamayor Sandstone ... 201
the solution concentration within the
pore increases, thereby giving rise to
the formation of fibres on the inner
wall of the pore in a circular fashion.
In a weathered sandstone, only the
remains of these fibres can be seen, as
presented in microphotographs E
and F. In microphotograph C, a
weathered feldspar grain with palygorskite
fibres in its fissures, is presented.
In microphotograph D, a
quartz grain covered with fibres is
shown. These fibres are probably
oriented in the direction of solution
movement. Quartz and feldspar
grains were identified using a microprobe.
The point of attachment of palygorskite
to the sandstone skeleton
can be seen very clearly in microphotographs
E and F. They,.pertain
to a sampl~ collected from the upper
part of a building of the XVII century.
A study on the weathering process
of thes sandstone in buildings of
Salamanca City (VICENTE et al., unpublished)
revealed that one of the
characteristics of the weathered
sandstone is the presence of large
empty pores. The network of palygorskite
fibres covering these pores
prior to weathering, is destroyed as a
result of weathering processes wherein
the internal tensions developed as
a result .of the expansion-contraction
processes of the smectite, during the.
alternating wet and dry seasons,
constitute an important factor
(VICENTE, 1983). This could be
appreciated in microphotograph E,
where only three coarse fibres are
present in the fissure of a feldspar
grain. In the bottom-right of the same
photograph, the point of origin of
small fibres is ~hown. In microphotograph
F, the remains ofa fibrous net-
, work within a large pore (approximately
30 x14 Jlm) can be seen. This
fibrous networkprobably covered the
pore space prior to weathering.
Data on the analysis of the water
that moistens the quarries during a
large part of the year, are presented
in Table 1. SINGER & NORRISH
(1974) express the st?_tbility range of
palygorskite in terms of H+ and Mg 2 + ·
activity at different activity levels of
Si, based on the solubility data
obtained using palygorskite of Mt.
Flinders. According to the results of
these authors, the water ot" Villamayor
quarries is a medium in which
·palygorskite is stable. With a pH of
7.4 and log [Mg 2 +] of -2.55, palygorskite
would be stable down to as low a
concentration of Si as log [Si(OH)4]
equal to -3.4. The concentration of·
Si in the water samples of the quarry
is higher (log [Si(OH)4] = -2.98). In
other words, with the concentrations
of silicon and magnesium that exist
in the water samples, palygorskite
TABLE 1
pH and chemical analysis of water that moistens the quarry
pH log [Si(OH) 4 ] log [Mg 2 +] log [Al(OH)i] log [Ca 2 +] log [Na+]
7.4 -2.89 -2.5~ -5.00 -2.69 -3.08 -3.01

202 M .A. Vicente, J. Vicente-Herntmdez
would be stable down to a pH as low
as 6.8, or with the actual pH and silicon
concentration, the stability limit
would be fixed at a magnesium concentration
oflog [Mg 2 +] = -3.4.
From the morphology and disposition
of palygorskite fibres in the Villamayor
sandstone, it is clear that the
formation of palygorksite occurs in
situ, and later than the deposition of
coarser components of the sandstone.
Water that flows through the
initially-deposited materials, is enriched
with calcium and magnesium
owing to its filtration through car-
the Cuenca del Duero, probably during
the Upper Tertiary (NeQg~D?L
(JIMENEZ FUENTES, personal communication).
In the later humid
periods the development would have
been less, but the abundance of calcareous
materials in the zone has
contributed to the fact that this water
has a calcium and magnesium concentration
and pH that fall within the
stability range of palygorskite.
Acknowledgements
The authors thank Miss J. Berrier
bonates. Although the quarry water for the SEM observation~, Prof. Dr.
analysis, (Table 1), indicates that M. Sanchez-Camazano and Dr. J.
· palygorskite is highly stable in this Saavedra for critically reviewing the
~~---- ~ater~ its development occurred in a- manuscript and Dr. P. Subramanian
period drier than that present now in for the English translation.
REFERENCES
ARRESE F., LOZANO A., MARTIN-PATINO M.T., RODRIGUEZ J., 1965. Estudio de /as areniscas de Villamayor
(Salamanca). Acta Salmanticensia, VI, n. 5, 1-57.
GALAN E., FERRERO A., 1982. Palygorskite-Sepiolite Clays ofLebrija, Southern Spain. Clays Clay Miner.
3, 191-200.
HASSUOBA H., SHAW H.F., 1980. The occurrence ofpalygorskite in quaternary sediments of the coastal
plain of north-west Egypt. Clay Minerals. 15, 77-83.
lsPHORDING W.C., 1973. Discussion of the occurrence and origin of sedimentary palygorskite-sepiolite
deposits. Clays Clay Miner. 21, 391-401.
MARTIN PozAs J .M., SANCHEZ-CAMAZANO M., MARTIN-VrvALDI J .M., 1981. La palygorskita de Tabladillo
(Guadalajara). Bol. Inst. Geol. Min. 92, 395-402.
MARTIN POZAS J.M., MARTIN VIVALDI J.M., SANCHEZ-CAMAZANO M., 1983. El yacimiento de sepio/itapa/ygorskita
de Sacramenia, Segovia. Bol. Inst. Geol. Min. 94, 113-120.
MILLOT G., 1964. Geologie des Argiles. Masson et Cie, Paris.
MrLLOT G., PAQUET H., RUELLAN A., 1969. Neoformation de l'attapulgite dans les sols a carapaces
calcaires de la Baisse Moulouya (Maroc Oriental). C.R. Acad. Se. Paris, 268-D, 2771-2774.
PEr-LrN-TIEN, 1973. Palygorskite from Warrem Quarry, Enderby, Leicestershire, England. Clay Mineral
10, 27-34.
RoBERT M., 1975. Principes de determination qualitative des mineraux argileu:x: a 1' aide. des rayons-X.
Ann. Agron. 26, 363-399.
RoGERS L.E., MARTIN A.E., NoRRISH K., 1954. The occurrence of palygorskite near Ipswich, Queensland
(Australia). Mineral. Mag. 30, 534-540.
SANCHEZ-CAMAZANO M., GARCIA RqDRIGUEZ A., 1971. Atapulgita y sepiolita en sue/os sabre sedimentos
calizos de Salamanca, Espaiia. An. Edaf. Agrobiol. 30, 357-373.
SINGER A., NORRISH K., 1974. Pedogenic palygorskite occurrences in Australia. Am. Miner. 59, 508-
517 .
•

The Origin of Palygorskite in Villamayor Sandstone ... 203
SINGER A., 1981. The texture of palygorskite from the Rift Valley, Southern Israel. Clay Mineral's 16,
415-419.
TRAUTH N., 1977. Argiles evaporitiques dans la sedimentation carbonatee continentale et epicontinentale
tertiaire. These Docteur en Sciences, Universite Louis Pasteur, Strasbourg, France.
VICENTE M.A., 1983. Clay mineralogy as the key factor in;weathering of Arenisca Dorada (Golden
Sandstone) of Salamanca·, Spain~ Clay Minerals 18,215-217.
WATTS N.L., 1976. Paleopedogenic palygorskite from the basal Permotriassic of Northwest Scotland.
Am. Miner: 61, 299-302.
Y AALON D .H., WIEDER M., 197 6. Pedogenic palygorskite in some arid brown ( calciorthid) soils of Israel.
Clay Minerals 17, 73-81.

Miner. Petrogr. Acta
Vql. 29-A, pp. 205-216 (1985)
Weathering Products of Vulture Volcanites,
Lucania, Southern Italy
M. DI PIERRO, M. MORES!, F. VURRO
Dipartimento Geomineralogico dell'Universita di Bar), Campus, Via G. Salvemini, 70124 Bari, Italia
ABSTRACT - The weathering types of the Vulture volcanites, and the
chemical-mineralogical composition of weathering products were examined
on la vas and pyroclastics of trachytic-phonolitic and tephritic-foiditic composition.
Research shows that the effects of weathering are more evident on
the pyroc,lastics than on the lavas; chemical weathering prevails in the former,
physical disgregation in the latter.
The weathering products mainly consist of crystalline and paracrystalline·
minerals, of components in the colloidal state, and of a water-seluble fraction.
The crystalline and paracrystalline minerals are essentially represented
by Al-silicates such as lOA halloysite, 7A halloysite, a)lophane, imogolite,
and by Fe-hydroxides such as lepidocrocite, ferrihydrite, goethite. The Alsilicates
are always more abundant than the Fe-hydroxides. The components
in the colloidal state are amorphous silica and amorphous alumina. The
water-soluble fraction has a composition such as
(Na+ > Ca 2 + > K+ > Mg 2 +) =(Cl-> sd;n.
In conclusion, the res~lts show that the weathering of the Vulture volcanites
has a predominantly monosiallitic character with a low level of ferrallitization.
This, however, totally· contradicts the character of weathering which is
expected from studies of the chemical composition of the Vulture underground
waters, which, in fact, indicate a very clear bisiallitization. To explain
this divergence one can hypothesize that the analyzed weathering products
originate from the interaction of the volcanites with more dilute waters
than those circulating deeper underground.
Introduction '
The main type of weathering is rel~ted
to physical, chemical and biological
processes. Whether one process
prevails over another depends on the
comparative importance of factors
such as the type of parent rocks, climate,
morphology, and biological
activity. Major advances in understanding
the mechanism involved in
chemical weathering have been made
in studies on water-rock interactions
at the surface of the lithosphere.
More modern research carried out in
this field generally tries to characterize
the main trends of weathering in
terms of its geochemical and mineralogical
evolution from parent rocks
This work was carried out with the financial support of the Italian National Research Council
(C.N.R.): contract n. 82.02612/05.115:05357. · ··

206 M. Di Pierro, M. Moresi, F. Vurro
towards residual systems (e.g. CHES­
WORTH, 1973). It also aims at pointing
out the relationship between the
waters' geochemical nature and the
neogenesis of minerals defined as
bisiallitization, hemisiallitization,
allitization and/or ferralitization
(e.g. PEDRO, 1966; TARDY, 1971).
Laboratory experiments have made
·remarkable contributions to this research
(e.g. PEDRO, 1964), as have
developments in thermodyna~ics
(e.g. GARRELS & CHRIST, 1965;
HELGESON, 1970) and recent data
on mineralogical soil composition
(e.g. WADA & HARWARD, 1974).
ering types that develop on the volcanic
rocks of Vulture.---~----------------------
2) Characterization of the mineralogical
and chemical composition of
weathering products, also seen in relationship
to the water-rock equilibrium.
Morphology, geology, and petrography
of the Vulture volcanic complex
The Vulture volcanic complex (Fig.
1) is located between the eastern
slope of the Lucania Apennines and
the western margin of the (F"" 187 of the Carta
-----a-'s_£'-'-o-'11'-'-ows: _________(Je_Ql_ogi~a___ d'I_talia). It develops in
1) Investigation of the main weath- altitude from 500-600 m to 1326 m.
4D
I? I
4 r
I C
I 0 NI AN
50 100
Fig. 1 -Location of Vulture volcanic complex in southern Italy.

Weathering Products of Vulture Volcaiiites ... 207
The sedimentary basement of the
volcanic units consists of pre­
Pliocenic formations and Pliocenic
sediments;· the former are represented
by the «Flysch Rosso» (marls
with' interbedded calcarenites, calcirudites
and calcilutites), by the
«Flysch Numidico>> (quartz-arenites
with interstratified marls and siltstones)
and by the «Formazione di
Gorgoglione>> (intercalations ofsandstones
and silty clays); the latter are
represented, from the bottom upwards,
by marly clays, sands and
conglomerates.
The volcanic outcropping units,
from the earliest to the most recent,
can be referred to the products of the
trachytic-phonolitic cycle and the
tephritic-foiditic cycle (HIEKE MER­
LIN, 1967; LA VOLPE & PICCARRE­
TA, 1971; 1972; LA VOLPE & RAPI­
SARDI, 1977; DE FINO et al., 1982).
The pyroclastics are more abundant
than lavas; the most diffuse deposits
are represented by the pyroclastics of
the tephritic-foiditic cycle. The. main
minerals are feldspars (mostly plagioclases;
sanidine and anorthoclase
ar:e present only in trachyticphonolitic
products), feldspathoids of
the sodalite group, and pyroxenes.
. Some leucite, amphiboles, olivine
and garnet are present.
. K-Ar dating indica~s that the age
of the volcanic products is between
0.83-0.50 m.y. (CORTIN!, 1975).
The climate
The values from the meteorological station (652 m
in altitude) indicate that the mean
annual air temperature is 14.1 oc in
the Vulture area, and that the mean
annual rainfall is 792 mm (references
from the

The types of weathering that develop
on the volcanites, and the
chemical-mineralogical composition
of weathering products were examined
on 28 rock samples including
10 volcanites of trachytic-phonolitc
composition (4 lavas and 6 pyroclastics)
and 18 volcanites of tephriticfoiditic
composition (10 lavas and 8
pyroclastics). The samples, collected
as much as possible in uniform conditions
of climate, topography, vegetatlvecovering,
and-astronomic exposure,
were macroscopically sorted
into unalterated rocks, alterated
rocks, and very alterated rocks.
A weighed amount of every sample
was subjected to an ultrasonic treatment
in distilled water; then the
whole size fractions Cl->SO~-).
The waters which sometimes circulate
in contact with the sedimentary
substratum and which spring up to
the base of Vulture belong to the
second group. They have an acidic
pH, ~ mean saline concentration
higher than 1 g/1, and high contents of
free C0 2 • Their mean chemical composition
can be indicated by:
(Ca 2 +>Na+>Mg 2 +>K+) =
(HC03>SO~->Cl-).
All the waters analyzed have a
temperature which varies from 9.8 to
17.4 °C.
Vulture is characterized, at higher
altitudes, by the presence of typical
ando-soils that become gradually
less frequent as the altitude decreases.
In the more anthropic zone
Brown-soils also are present
(VIOLANTE & VIOLANTE, 1973;
LULLI & BIDINI, 1975).
The sandy fraction of these soils
consists of femic minerals prevailing
over felsic minerals; the former are
represented by pyroxenes, olivine
and amphiboles in order of decreasing
abundance; the latter by anorthoclase
and occasional sanidine.
Also well crystallized magnetite and
Fe-oxides-hydroxides are present.
The clay fractions consist of lOA halloysite,
7 A halloysite, allophane and
imogolite with considerable amounts
of some amorphous components
(VIOLANTE & VIOLANTE, 1973;
Field and laboratory methods

nents were analyzed by AA Spectrophotometry
(Na; Ca, K, Mg) and
by volumetric-gravimetric methods
(Cl, S0 4); amorphous components, removed
from some samples by NaOH
treatment, were analyzed by XRF
techniques,
In order to investigate the relationships
between the geochemical
characteristics of the underground
waters of Vulture and the neogenesis
of the weathering minerals, the
water-rock equilibria were studied
using two methods. The first utilizes
the equilibrium diagrams containing
the stability fields of secondary
minerals· such as gibbsite, kaolinite,
montmorillonite (references in TAR­
DY, 1971). The second utilizes the
geochemical balance based on the
comparison (PEDRO, 1964; 1966) ?f
8
-g4
>
0
E
s..
"'
E
:>..
"'

210 M. Di Pierro, M. Moresi, F. Vurro
rocks safely derives from the weathering
processes. On the other hand,
the mean values given in Table 1 indicate
that the whole size fraction <
63 J.Lm removed from pyroclastics is,
on the average, four times greater
than the same-size fraction removed
from lavas.
Concerning the main · type of
weathering, relevant data can be
obtained from checking the relative
amount of separated size fractions; in
fact it may be considered that physical
weathering produc,es relatively
sensitive to weathering effects than
lavas; chemical alteration prevails in
the former, physical 'ciisgregatiori·Tn:··--··-
the latter. This is definitely related to
the texture of the analyzed rocks; in
fact, the greater porosity of pyroclastics,
compared to that of lavas, increases
the surface exposed to weathering
factors.
Mineralogical composition
XRD analyses, performed on the
coarse-size fragments, whereas three size fractions removed from
chemical weathering essentially each sample, showed the presence of
leads to neogenesis of secondary neoformed minerals and of primary
minerals that concentrate in the fine minerals belonging to the parent
-------s-;i-z-e'fractions. The mean values given ---roc:KS:Tlieiornier are riiore abundant
in Table 1 show that the distribution in the finer size fractions, the latter in
of the size fractions removed from the coarser size fractions. The main
la vas may be indicated by: coarse silt primary minerals are represented by
>clay; and that removed from pyro- feldspars, feldspathoids, pyroxenes,
clastics by: clay> coarse silt. m

cially in the 4-16 J.Lm size fraction, a
considerable amount of micas, always
associated with quartz(!). The
feldspars are mainly represented by
plagioclases; K-feldspars also are
present in the samples of trachytic-:
phonolitic composition. The most
abundant feldspathoid is analcite
which m~st be included among the .
primary minerals because it derives
from the transformation of leucite by
autometamorphic processes which
occurred during volcanic activity
(HIEKE MERLIN, 1967). The feldspathoids
of the sodalite group are
rate: very alterated crystals of
hauyna are microscopically identified.
The pyroxenes have generally an
augitic-aegirinic composition. The
micas are represented by biotite and/
or phlogopite. With regard to ·the
ratios of abundance among the main
primary minerals, one can remark
that, according to the composition of
the parent rocks, feldspars distinctly
prevail over analcite, pyroxenes and
Fe-oxides, in samples of. trachyticphonolitic
composition. However,
analcite, pyroxenes and Fe-oxides increase,
whereas plagioclasesdecrease
in samples of tephritic-foiditic composition.
There are no substantial differences
between b:tvas and pyroclastics.
The secondary minerals mainly
consist of Al-silicates and Fehydroxides.
Among the Al-silicates
the well crystallized minerals such as
lOA halloysite and/or 7 A halloysite
Weathering Products of Vulture Volcanites ... 211
distinctly prevail over poorly crystallized
mineral such as allophane and
imogolite. Among the Fe-hydroxides
such minerals as lepidocrocite,
goethite and ferrihydrite were recognized.
Low amounts of Al-hydroxides
such as gibbsite and boehmite are
sometimes present. Moreover, hydrobiotite,
mixed-layer hydrobiotitevermiculite,
and vermiculite are present
when the samples contain primary
micas. Concerning the quantitative
ratio between Al-silicates and
Fe~hydroxides, one can note that even
though it remains higher than 1, it
tends to decrease in passing from the
samples of trachytic-phonolitic composition
to those of tephritic-foiditic
composition.
Finally, one must remark that, in
the< 4 J.Lm size fractions, amorphous
components are present in sometimes
considerable amounts. XRF
analyses performed on such colloids
(removed from some samples by
NaOH treatment) showed that the
main components are silicon and aluminium
with a ratio of abundance
close to one.
Therefore the mineralogical study
shows that the chemical weathering
of the samples analyzed is mainly
monosiallitic, with a tendency to be
ferrallitic, depending on the composition
of the parent rocks. The
neogenesis ofbisiallitic minerals (e.g.
vermiculite) is strictly limited to the
presence of primary micas.
(I) Quartz and micas belong to the rocks of the sedimentary substratum and were included i.n the
volcanic products at the time of magmatic effusion (LA VOLPE & PICCARRETA, 1972).

212 M. Di Pierro, M. Moresi, F. Vurro
Chemical composition of the watersoluble
components
The mean values given in Table 2
show that the water-soluble components
have a main distribution such
as: (Na+ > Ca 2 + > K+ > Mg 2 +) = (Cl­
> so~-); slight differences occur in
the samples of trachytic-phonolitc
composition. The lavas in fact show
K+>Ca 2 +and SO~->Cl-, whereas the
pyroclastic materials show Na+ =
Ca 2 +. Considerable amounts of Cl and
S suggest that the released ions largec
ly derive from the leaching of weathering
products of feldspathoids beleaching
of K also may derive from
the alteration oH~-feldspars·-that--are~present
in these rocks.·
Finally, the very low amount of Mg
among those water-soluble components,
indicates that most of this element
(which definitely derives from
the alteration ofFe-Mg-minerals such
as pyroxenes, biotite, olivine, amphiboles)
has already been removed
from the rocks by leaching solutions,
whereas iron tends to be concentrated
in Fe-hydroxides, according to
the mineralogical composition of the
weathering products.
longing to the sodalite group(2). The
in_tense_l~aching_of_K,~Ca_a,nd_S from_Water:~mck equilibrium
the weathering products ofvolcanites
of trachytic-phonolitic composition
agrees both with the hauynic character
of the feldspathoids belonging to
these rocks (HIEKE MERLIN, 1967),
and with the abundance of Ca, K and
so3 in the chemical composition of
the Vulture hau}rna (RITTMANN,
1931). On the other hand, the intense
At this point we can verify whether
or not the chemical composition of
Vulture underground waters agrees
with the monosiallitic and/or ferrallitic
weathering characteristics, as
found by mineralogical investigations.
Contrary to expectations, using
the stability relationships among
TABLE 2
Chemical composition of water-soluble components (values in equivalent weight %)
Ca 2 + M!f+ Na+ K+ cl- so~-
Trachytic- La vas x 0.236 0.025 0.790 0.404 0.661 0.783
phonolitic cr 0.083 0.016 0.347 0.208 0.521 0.400
products
Pyroclastics x 0.659 0.114 0.668 0.191 1.281 0.351
cr 0.438. 0.117 0.354 0.127 0.258 0.173
Tephritic- La vas x 0.459 0.075 0.841 0.198 1.004 0.567
foiditic cr 0.363 0.088 0.344 0.119 0.413 0.343
products
Pyroclastics x 0.371 0.066 0.883 0.202 0.780 0.742
cr 0.395 0.065 0.407 0.120 0.377 0.291
(2) This also agrees with the fact that the Si02/Al203 ratio i~ close to 1 bot~ in the feldspathoids of
the sodalite group and in the neoformed Al-silicates (lOA halloysite, 7A halloysite, allophane,
imogolite, amorphous components).

Weathering Products of Vulture Volcanites: .. 213
gibbsite, kaolii).ite and montmorillonite
(Figs 3 and 4), it results that
most of the water samples fall into
the Na-Ca-montmorillonite stability
field. The same conclusion can be
drawn from considering the geochemical
balance: water vs. weathered
rocks. In fact, as shown in Fig. 5, the
L water ratio is lower than the Rk
rock ratio; this means that an important
amount of released silica remains
in situ ai).d weathering has a
bisiallitic character.
To explain this divergence, one
may presume that the secondary
minerals of the weathering products
analyzed are in equilibrium with surface
waters which are more dilute
than the underground waters. In the
latter, the higher concentrations of
components in solutions, especially
Si0 2 , Na and Ca, may move the conditions
of equilibrium towards the
. stability of bisiallitic minerals.
Conclusion
This study has perm~tt~d a definition
of some weathering characteristics
of the Vulture volcanites. One
aspect concerns the influence of the
[Na+]
15 1 og~
10
Albite
5
Gibbsite
0.5
5
I
I
I
I
I
I
I
NI
~l
5-1
I
I
I
Kaol inite
I
I
10
IVl
1o '"'
1.

214
M. Di Pierro, M. Moresi, F. Vurro
20 log
Anorthite
15
10
Gi bbs i te
0.5
10
,:;::
I"'
I"' '"'
,_g
,c.
IB
,e
.. ..,cc
:
••
...,
~
:
•
•••• •••
• •
••
• I
I
50
I
I
~I I' \
I
100
'
ppm s;o 2
-5
-4
Fig. 4- Stability relations among anorthite, gibbsite, kaolinite, Ca-montmorillonite, at 25°C and 1
atmosphere as a function of [Ca 2 +], pH and [H4Si04]. Symbols as in Fig. 3.
-3
2.5
··@ x=2.04; a=O.B3
ALLITIZATION OR
FERRALLITIZAT!ON
HEMISIALLITIZA T!ON
Si 0 2
combined
Na 2 0+KzO+CaO+MgO
in rock
1.5
-@x=1.10;a=0.46
M0NOSIALL ITIZATION
B ISIALLITIZA T!ON
Si0 2
combined - 2Al 2 o
Rk-
3
NazO+KzO+CaO+MgO
in rock
0.5
--@ x = 0.30; a= 0.27
SiOz
NazO+KzO+CaO+MgO
in water
Fig. 5 - L, Rand Rk ratios. L values were calculated from 28 analyses of water reported in FIDELI­
BUS et al. (1981); R a,nd Rk values from 54 analyses of volcanites reported in HIEKE MERLIN
(1967) and DE FINO et al. (1982).

Weathering Products of Vulture Votcanites ... 215
parent rocks on the degree and type
of weathering. The results obtained
show that the effects of weathering
are more evident on the pyroclastics
than on the lavas; in the former,
chemical weathering prevails, whereas
in the latter, one finds physical disintegration.
Another aspect, related to waterrock
interaction, concerns the contrast
between the mineralogical composltlon
of weathering products
neoformed from surface rocks and
the chemical composition of the
underground waters. To explain this
divergence one may hypothesize the
presence of two.weathering zones in
the volcanic complex. The first takes
place on the surface: the rocks are in
contact with very dilute waters and
the neoformed minerals are monosiallitic
and/or ferrallitic. The s~cop.d
is deeper: the rocks are in contact
with more concentrated waters
whose chemical composition indicates
a foreseable neogenesis of
bisiallitic minerals.
It would be interesting to verify experimentally
whether or not deeper
rock. weathering reaLly leads to
neogenesis of bisiallitic minerals, examining
also the chemical evolution
of the waters with re~pect to depth
and underground permanence time.
At present, using available data, it
is possible to compare the chemical
composition of waters obtained from
laboratory-treated samples (all collected
at the surface of the volcanic
complex) with the chemical composition
of underground waters. The former,
which may be considered surface
waters, have a cationic composition
such as Na+ > Ca 2 + > K+ >
Mg 2 +; the latter, Ca 2 + > Na+ > Mg 2 +
> K+. This assumption aside, it
seems that, from the movement of
surface waters underground, the
mobility of Ca and Mg increases with
respect to that of Na and K. It is
possible to relate this chemical evolution
to changes in primary minerals
subjected to weathering. At the surface
of the volcanic complex, weathering
leads mainly to the alteration of
haiiyna; whereas in depth, it may
lead also to the alteration of plagioclases
and pyroxenes. These may be
responsible for both the enrichment
of Ca and Mg in circulating solutions,
and for the release of silica and alumina
with a ratio similar to that required
for the neogenesis ofbisiallitic
minerals. It is also possible to relate
the reduced K mobility, in the deeper
zones, to an increased absorption of
this element by the more abundant
clay minerals, hypothesized as bisiallites.
It would however be necessary to
check the above hypothesis experimentally
before drawing any defi­
.nite conclusions on these aspects of
~ea the ring.

216 M. Di Pierro, M. Moresi, F. Vurro
REFERENCES
CHESWORTH W., 1973. The residual system of chemical weathering: a model for the chemical breakdown
of silicate rocks at the surface of the earth. J. Soil Sci. 24, 69-81.
CrET P., TAzrou G.S.,, 1981. Dati sul regime idrogeologico e termico delle sorgenti del M. Vulture
· (Basilicata). Atti II Seminario Informativo, Progetto Finalizzato Energetica, CNR-PEG Ed.,
142-152.
CORTIN! M., 1975. Eta K-Ar del Monte Vulture (Lucania). Riv. Ita!. Geof. 2, 45-46.
DE FINO M., LA VoLPE L., PICCARRETA G., 1982. Magma evolution at Mount Vulture (Southern Italy).
Bull. Vulcanol. 45, 115-126.
FARMER V.C., FRASER A.R., TAIT J.M., PALMIERI F., VIOLANTE P., NAKAI M., YOSHINAGA N., 1978.
Imogolite and proto-imogolite in an Italian soil developed on volcanic ash. Clay Minerals 13,
271-274.
FIDELIBUS D., TAZIOLI G.S., TITTOZZI P., VURRO F., 1981. Chimismo delle acque sotterranee del M.
Vulture (Basilicata). Atti II Seminario Informativo, Progetto Finalizzato Energetica, CNR-PEG
Ed., 131-141.
GARRELS R.M., CHRIST C.L., 1965. Solutions, Minerals and Equilibria. Harper & Row, New York.
HELGESON H.G., 1970. Description and interpretation of phase relations in geochemical processes
involving aqueous solutions. Amer. J. Sci. 268, 415-438.
HIEKE MERLIN 0., 1967. I prodotti vulcanici del Monte Vulture (Lucania). Mem. Ist. Geol. Min. Univ.
Padova XXVI, 3-67.
LA VoLPE L., PrcCARRETA G., 1971. Le piroclastiti del Monte Vulture (Lucania). Nota I. Le «Pozzolane»
di Rionero e Barile. Rend. Soc. It. Min. Petr. 17, 167-186.
LA VoLPE L., PICCARRETA G., 1972. Le ignimbriti del Monte Vulture (Lucania). Rend. Soc. It. Min. Petr.
28, 191-214. '
LA VOLPE L., RAPISARDI L.; 197'7:05servazwnigeofogic/1.e su(versante meridioni:lle (iel M. Vulture;
genesi ed evoluzione del bacino lacustre di Atella·. Boil. Soc. Geol. It. 96, 181-197.
LULL! L., BIDINI D., 1975. Tendenze evolutive di alcuni suoli dell'edifico vulcanico del Vulture (Lucania).
Annali Ist. Sper. Studio e Difesa del Suolo- Firenze, VI, 87-105.
PEDRO G., 1964. Contribution a l'etude experimentale de /'alteration geochimique des roches cristallines.
Ph. D. Thesis, University of Paris, France.
PEDRO G., 1966. Essai sur la caracterisation geochimique des differents processus zonaux resultant de
!'alteration des roches superficielles (cycle alumino-silicique). C. R. Acad. Sci., Paris, 262-D,
1828-1831.
RITTMANN A., 1931. Gesteine und Mi_neralien von Monte Vulture in der Basilicata. Schweiz. miner.
petrogr. Mitt. 11, 240-252.
TARDY Y,., 1971. Characterization of the principal weathering types by the geochemistry of waters from
some European and African crystalline massifs. Chem. Geol. 7, 253-271.
VIOLANTE P., VIOLANTE A., 1973. Gli andosuoli del Vulture. Ann. Fac. Sci. Agr. Universita di Napoli
VII, 219-238.
VIOLANTE P., VIOLANTE A., 1977. L'halloysite sferoidale nei suoli del Vulture. Agrochimica 6, 513-522.
VIOLANTE P., PALMIERI F., VIOLANTE A., 1977. L'imogolite in alcuni suoli vulcanici italiani. Atti 2"
Congr. Naz. sulle Argille 1976, Bari, Geol. Appl. Idrogeol. 12, parte II, 325-336.
WADA K., HARWARD M.E., 1974. Amorphous clay constituents of soils. Adv. Agron. 26, 211-260.

Miner. Petrogr. Acta
Vol. 29-A, pp. 217-230 (1985)
Compositional Characteristics of «Argille Varicolori»
from Outcrops of Bisaccia and Calitri,
Avellino Province, Southern Italy
M. DI PIERRO, M. MORESI
Dipartimento Geomineralogico dell'UniversWt di Bari, Campus, Via G. Salvemini, 70124 Bari, Italia
ABSTRACT- The clays e~amined, coming from the «argi!le varicolori>> of the
«Complesso Sicilide» (OGNIBEN, 1969), outcrop near Bisaccia and Calitri
(Avellino Province, southern Italy). They have a variable colour (from darkgrey
to greenish-grey and reddish-brown) with whitish and yellowish concentrations
of dickite and of natrojarosite, respectively. Texturally they are
silty clays, clayey silts and clays proper. The silty clays and the clayey silts
show several maxima in the size-frequency distribution which indicate
shallow-sea sediments deposited after a slow transport of mass; while the
clays proper have only one dominant size grade which indicate a deep basin
and a deposition after a long transport in suspension.
The clays examined contain clay minerals, quartz, feldspars, carbonates and
traces of muscovite, biotite, chlorite and Fe-hydroxides. The clay minerals
consist of smectite (beidellite-montmorillonite series), Al-illite 2M, kaolinite
and/or dickite, Fe-chlorite, and mixed-layer illite-smectite. Quartz is present
as rounded grains with a glossy surface; the feldspars ai:e covered by weathering
products which prevented their accurate mineralogical identification.
The carbonates are composed of both inorganic and organic grains; the former
consist of both limestone fragments and calcite rombohedrals from
chemical precipitation, and the latter of shells and Foraminifera fragments.
The samples can be classified as shales and clay marls.
The chemical composition is in agreement with the mineralogical one.
On the basis of the data obtained we think that most of the components
present in the days derive from laterite soil. The mineralogical association,
the crystallochemistry of the main components, the presence of poorly crystallized
Fe-hydroxides and the relatively high amount of Ti, a component
which usually concentrates in lateritic products, are in agreement with this
hypothesis.
Introduction
The outcrop in
southern Italy, along the Apennines
(OGNIBEN, 1969; BELVISO et al.,
1977). These sediments, which generally
seem to be allochtho;nous, have
not been uniformly defined as to their
li thostra tigraphic characteristics,
and paleogeographic and tectonic
positions, nor as to their origin (COC-
This work was carried out with the financial support of the Ministry of Public Education of Italy
(M.P.I. 40%: grant n. 83/4914). ·

Samples were collected from existing
cutaways excluding the fragments
of interbedded sandy-gravel
and materials showing signs of mixr
218 M. Di Pierro, M. Moresi
CO, 1972; D'ARGENIO et al., 1973;
COCCO & PESCATORE, 1968; AMI­
CARELLI et al., 1977; ABBA TICCHIO .
et al., 1981; FERLA & ALAIMO, 1975).
The present work studies the textural
and compositional characteristics
of the «argille varicolori» from the
olistostromes near Calitri arid the
landslips near Bisaccia (A vellino
Province, southern Italy). The olistostromes
are in the lower-middle
Pliocenic pelites and have been pro-·
tected from weathering. The landslip
clays, which form a small anticline.
lying NS, are upset; this is also evident
from the fragmentation of the
interbedded sandy-gravel layers, but
they have been altered by_~!!!!_

Cornpositional Characteristics of «Argille-varicolori» ... 219
ing due to landslips. Samples containing
dickite and/or natrojarosite
were also excluded.
Forty five samples coming from
different places of the area under
study (Table 1) were examined; the
samples from 1 to 17C belong to the
olistostromic deposits near Calitri,
samples 18A to 23 belong to the landslip
area near Bisaccia. The samples
marked by the same number followed
by letters in alphabetical order
derive from a vertical series sampled
from bottom to top. The letters R, V,
TABLE 1
Colour and geographic coordinates of the analyzed samples
1 greenish 2°59'17" 40°54'07"
2 reddish 2°59' 17" 40°54'07"
3 reddish-green 2°59' 17" 40°54'07"
4 greenish-red 2°59' 17" 40°54'07"
5 greenish · 2°59' 17" 40°54'07"
6 greenish 2°59' 17" 40°54'07"
7a reddish 2°55'13" 40°55'33"
7b reddish-green 2°55'13" 40°55'33"
Sa greenish-red 2°54'24" 40°55'43"
8b reddish 2°54'24" 40°55'43"
9 reddish 2°58'34"' 40°56'30"
10 greenish-red 2°58'34" 40°56'30"
lla reddish 2°58'34" 40°56'30"
llb greenish-red 2°58'34" 40°56'30"
12 greenish 2°58'34" 40°56'30"
13 greenish-red 2°58'34" 40°56'30"
14 reddish ' 2°57'13" 40°56'57"
15 greenish-red
2°56'58" 40°56' 17"
16 greenish 2°55'00" 40°57'24"
"
17a greenish 2°53' 51" 40°59'12"
17b greenish 2°53' 51" 40°59'12"
17c reddish 2°53'51" 40°59'12"
18a reddish 2°54'08" 41°00'36"
18b greenish 2°54'08" 41 °00'36"
18c greenish 2°54'08" 41 °00'36"
18d reddish 2°54'08" 41 °00'36"
18e reddish 2°54'08" 41 °00'36"
18f reddish-green 2°54'08" 41 °00'36"
18g reddish 2°54;08" 41 °00'36"
18h greenish-red 2°54'08" 41°00'36"
18i greenish 2°54'08" 41°00'36"
181 reddish 2°54'08" 41 °00'36"
18m greenish 2°54'08" 41 °00'36"
18n reddish 2°54'08" 41 °00'36"
18o reddish,green 2°54'08" 41 °00'36"
19a reddish 2°54'32" 4eo2'0S"
19b greenish 2°54'32" 41 °02'08"
19c greenish 2°54'32" 41°02'08"
19d , greenish 2°54'32" 41°02'08"
19e greenish-red 2°54'32" 41°02'08"
20 reddish-green 2°54'27" 41 °02'34"
21 reddish 2°54'32" 41 °03'59"
22a greenish 2°53'04" 41°04'23"
22b greenish 2°53'04" 41°04'23"
22c reddish -green 2°53'04" 41°04'23"
The coordinates are referred to·Mt. Mario- Rome

220 M. Di Pierro, M. Moresi
R-V, V-R, indicate the dominant colour
of the samples (R = reddish; V =
greenish).
All the samples, excluding the colour
differences, were found in plastic
masses, which, when dried, assumed
a certain consistency, but which
readily became mushy in water. Dilute
HCl treatment showed a large
amount of carbonates only in samples
collected close to relics of marlylimestones.
Textural, mineralogical and chemical
analyses were performed on each
sample.
Grain-size analysis was carried out~
by wet sieving for the greater than 32
J..Lm size grades and by sedimentation
for Tl:le-01her-size-gra-des .. (Mti.tt:ER,'
1962).
""- The mineralogical studies were
carried out using a Philips powder X­
ray diffractometer with Ni-filtered
CuKa radiation. Some crystallochemical
characteristics were
obtained for smectite according to
GREENE-KELLY (1953), BISCAYE
(1965), BAILEY (1980) and DE­
SPRAIRIES (1983); for illite according
to WEBER et al. (1976), BROWN
& BRINDLEY (1980) and DI PIERRO
(1981); for chlorite according to
JOHNS et al. (1954) and BROWN &
BRINDLEY (1980); and for kaolinite
according to HINCKLEY (1963). The
illite-smectite mixed-layer minerals
were identified according to BOWER
(1981) and SRODON (1981). The relative
abundance of non-clay minerals
was determined according to RAISH
(1964) and SCHULTZ (1964) using
MgC0 3 as a standard. The relative
abundance of clay minerals was determined~
.-

Compositional Characteristics of «Argilte-Varicolori» ... 221
TABLE 2
Grain-size composition

222 M. Di Pierro, M. Moresi
Clay
.
• 50
SandL:.._ ___ 4 25
,-------. 5
1o 0
-----,: 75
;--------'Silt
__Eig._L~Grain"size. distribution. of-the samples in SHEPARD's diagram (1954).
fields of silt, sandy-silt and sansicl.
Assuming that diagenetic processes
have not changed the main grain-size
characteristics of the sediments
analyzed, some information on the.
sedimentary environment can be
obtained from a study of frequency
diagrams and of cumulative curves.
According to the advanced assumption,
the silty-clay samples and the
three samples classified as silt,
sandy-silt and sansicl were not consiqered
because optical and. X-ray
observations revealed the presence of
clay lithified and/or cemented by
secondary calcite.
Frequency diagrams (Fig. 2) denote
that several maxima are present in
the grain size distribution of clayey
silts, whereas in that of clays proper
only one maximum class is present.
The average cumulative curves show
(RIVIERE, 1977) that the clays originated
from a single grain-size
population made up of fine detrital
material deposited in calm water by
decantation in a deep basin after a
long transport in suspension. The
clayey-silts instead originated from
mixing of distinct grain-size populations
which underwent different
transport processes, since they wer-e
deposited by slow turbidity currents
in shallow basins.
Therefore, one can suppose, since
the parent rocks are invariant, that
during the deposition phase, the
basin underwent depth changes and
that the modality of material tran~port
possibly varied as well.

Compositional Characteristics of «Argille Varicolori» ... 223
Fig. 2- Frequency diagrams and cumulative curves of clays (a) and clayey-silts (b). Ranges x ± cr
are shown.
Mineralogical characteristics
The samples contain clay minerals
associated with moderate amounts of
quartz, feldspars and carbonates
(Table 3).
The clay minerals are represented
by smectite (S), mixed layer illitesmectite
(liS), illite (I), kaolinite and/
or dickite (K) and chlorite (Ch). The
dioctahedral smectite, which has Ca
and Mg as interlaye~ cations, belongs
to the beidellite-montmorillonite
series because of a moderate amount
of Fe + Mg in octahedral positions
(from 0.30 to 0.50; x = 0.44; there are
no differences between the two
groups of samples); the crystallinity
is lower in the Calitri samples (v/p
from 0.2 to 0.6; x = 0.4) than in the
Bisaccia ones (v/p from 0.7 to ·1.0; x =
0.8). The mixed-layer illite-smectite'
clay minerals are random and have
30-40% smectite layers. The dioctahedral
Al-illite, polytype 2M, has a
low paragonite grade and poor crystallinity
(10 A peak width at halfheight
from 0.45 to 0.90 29, x = 0.70
29; E from 95 to 160; x = 110.) There
are no differences between the two
groups of samples. The Fe-chlorite
has a low crystallinity; the kaolinite
is generally disordered and is sometimes
replaced by well-ordered dickite.
Optical observations showed that
the· carbonates consist of inorganic
grains prevailing over the organic
ones. The former, which are found as
grains of carbonatic rocks, are composed
of calcite and/or occasional
dolomite, while the latter grains are

224 M. Di Pierro, M. Moresi
TABLE 3
Mineralogical composition
Samples IIS s I K Ch Q F c D
1 V 14 53 10 6 6 8 2 tr
2 R 14 so 7 7 5 10 tr 7 1
3 V-R 10 23 4 4 5 12 1 39 1
4 R-V 14 35 5 17 6 8 2 14 1
5 V 11 40 7 12 5 13 1 10 1
6 V 18 44 10 8 5 9 1 3 2
7a R 14 30 8 12 2 4 tr 32 tr
7b V-R 15 47 7 16 5 3 tr 6 1
Sa R-V 14 27 5 10 3 3 4 32 1
8b R 17 49 7 12 5 6 tr 3 1
9 R 15 70 10 5 4 5 1 tr tr
10 R-V 15 so 9 9 6 10 1 3 tr
11a R 14 so 8 11 3 4 tr 10 tr
11b R-V 17 60 6 6 5 5 1 tr tr
12 V 21 40 9 14 5 5 tr 6 tr
13 R-V 15 60 5 5 5 7 1 2 tr
14 R 15 45 6 19 6 7 1 tr 1
15 R-V 32 35 11 7 6 6 2 tr 1
16 V 24 36 10 8 6 10 5 1 tr
17a V 16 15 8 7 4 4 tr 46 tr
17b V 20 30 9 12 4 5 1 19 tr
17c R 12 40 10 18 4 4 tr 12 tr
18a R 6 62 12 7 5 6 1. tr
18b V 7 69 5 7 5 5 1 tr 1
18c V 7 65 1 6 7 12 1 tr 1
18d R 4 67 1 7 4 10 2 3 2
18e R 2 84 1 5 2 4 1 1 tr
18f V-R 4 77 2 4 5 6 1 1 tr
18g R 5 70 2 9 5 8 1 tr tr
18h R-V 4 68 2 4 5 9 1 6 1
18i V 3 58 6 4 6 8 1 13 1
181 V 3 so 3 1 3 4 tr 36 tr
18m V 4 67 4 1 4 7 1 11 tr
18n R 3 38 2 3 4 5 1 44 tr
18o V-R 8 68 1 3 5 7 2 5 1
19a R 7 64 5 6 6' 7 2 2 ·1
19b V 6 66 5 11 7 10 1 1 2
19c V 5 48 4 6 7 20 7 1 2
19d' V 6 51 4 5 7 12 5 8 2
19e R-V 6 55 . 7 12 6 7 3 2 2
20 V-R 3 58 2 8 5 10 8 6 2
21 R 3 38 9 3 8 12 4 22 1
22a V 5 53 4 18 7 7 1 5 tr
22b V 4 37 2 22 12 10 1 10 2
22c V-R 6 49 5 13 6 10 1 8 2
All samples
x 10 so 6 9 5 8 2 10
cr 7 15 6 5 2 3 2 13
Samples from 1 to 17c
x 16 42 8 10 5 7 11
cr 5 13 2 4 1 3 14
Samples from 18a to 22c
x 5 59 4 7 6 9 2 8
cr 2 12 3 5 2 4 2 11
IIS: mixed-layer illite-smectite; S: smectite; 1: illite; K: kaolinite and/or dickite; Ch: chlorite;
Q: quartz; F: feldspars; C: calcite; D: dolomite .

Compositional Characteristics of «Argille Varicolori» ... 225
of unidentifiable Foraminifera composed
of calcite and Mg-calcite.
Sometimes calcite is of secondary
precipitation. Feldspars are represented
by K-feldspars associated
with Na-plagioclases;, often the
grains are covered by clay weathering
products which prevented their
accurate mineralogical identification.
Quartz is present as rounded
grains with a glossy surface.
The X-ray diffraction patterns of
the samples showed the presence of
Fe"hydroxides, of low crystallinity,
which appear more abundant in the
reddish samples.
Optical observation showed the
presence of some muscovite, biotite,
gypsum, pyrite, rutile, grains of sand-
stone, and unidentifiable ochre coloured
aggregates.
In regard to the relative amounts of
the main mineralogical components,
the results show that clay minerals
are the most abundant (X.= 80%), and
that quartz plus feldspars together
equal the carbonates. Among clay
minerals, smectite (X. = SO%) is more
abundant than mixed layer illitesmectite
and kaolinite, both represented
in comparable amounts (X. =
10% and X. = 9%, respectively). Illite
and chlorite are the least abundant (X.
= 6% and X. = 5%, respectively).
Among the non-clay minerals, quartz
prevails over feldspars (Q/Q + F =
0.80), and calcite over dolomite (often
present in traces). Mineralogical clas-
c
I
I
I
I
I
I
-- 2 ---------:-- 4
I
I
I
I
I
I
I
I
I
15 17
I
I
I
I
I
I
I
I
I
I
: ..
I
• 0
Fig. 3- Distribution of the samples in MALESANI & MANETTI's diagram (1970). C: carbonates; S:
sheet silicates; Q + F: quartz+ feldspars. 1: calcarenites; 2: carbonatic sandstones; 3: sandstones;
4: carbonatic siltstones; 5: siltstones; 6: marls; 7: shales. Open squares: clays; open circles: siltycfays;
full circles: silts and clayey-silts. ·

·----~---~---~~-------------. ------------
~~'
226 M. Di Pierro, M. Moresi
TABLE 4
Chemical composition
Samples .SiOz TiOz Alz03 Fez03 MnO M gO CaO NazO KzO PzOs H 2 0+ CaC03MgC03
1 V 53.51 1.24 17.92 6.63 0.13 3.40 0.32 0.54 2.57 0.17 10.53 2.20 0.36
2 R 54.40 1.28 17.34 7.37 0.09 3.38 0.32 0.49 1.67 0.17 5.08 7.65 0.58
3 V-R 36.22 1.03 12.00 4.50 0.08 1.62 0.46 0.34 0.96 0.10 3.37 38.98 0.58
4 R-V 48.59 1.46 19.24 6.80 0.09 1.87 0.39 0.56 2.35 0.16 3.70 13.98 0.87
5 V 50.29 1.38 20.50 6.38 0.08 2.12 0.25 0.60 2.17 0.17 5.38 9.99 0.89
6 V 56.16 1.34 16.47 6.63 0.07 3.34 0.49 0.53 1.48 0.19 8.17 3.49 1.09
7a R 38.90 1.06 14.37 6.75 0.11 1.37 0.75 0.47 1.80 0.13 2.97 31.48 0.29
7b V-R 49.72 1.47 23.30 6.74 0.07 2.17 1.07 0.48 2.56 0.17 6.10 5.48 0.79
Sa R-V 38.03 1.10 14.26 5.38 0.09 1.86 0.71 0.42 1.61 0.12 3.79 31.96 0.52
Sb R 53.07 1.58 21.38 8.76 0.13 1.77 0.44 0.56 2.33 0.16 6.68 2.82 0.44
9 R 53.98 1.44 20.94 8.94 0.06 2.29 0.31 0.56 1.54 0.17 9.76 0.14 0.37
10 R-V 52.76 1.46 22.86 7.06 0.08 1.51 0.35 0.57 1.32 0.16 9.11 3.00 0.44
11a R 49.80 1.28 18.81 7.32 0.12 1.80 0.23 0.57 1.71 0.13 6.39 11.34 0.35
11b R-V 53.31 1.58 25.37 7.60 0.10 1.69 0.22 0.56 2.20 0.19 7.08 0.15 0.40
12 V 51.89 1.42 19.88 6.57 0.05 2.05 0.46 0.56 1.92 0.20 8.52 5.74 0.69
13 R-V 54.95 1.49 19.98 7.53 0.06 2.23 0.85 0.61 2.26 0.20 7.77 1.10 0.72
14 R 54.71 1.74 24.35 8.62 0.11 1.69 0.25 0.56 2.01 0.19 5.27 0.18 0.69
15 R-V 56.94 1.38 21.74 7.80 0.13 3.14 0.28 0.83 2.34 0.18 5.06 0.22 0.53
16 V 57.20 1.22 19.81 8.87 0.07 1.41 1.27 0.72 2.63 0.21 6.38 0.43 0.29
17a V 29.66 0.74 11.14 5.75 0.07 0.94 0.27 0.29 0.99 0.09 4.21 45.95 0.34
17b V 43.36 1.24 15.26 6.70 0.11 1.74 0.92 .0.52 2.35 0.15 8.22 18.49 0.31
17c R 48.64 1.51 20.93 7.14 0.09 2.09 0.36 0.54 1.62 0.14 5.66 11.98 0.18
----- ---- . --
18a R 53.76 1.6.0 19.01 10.94 0.14 2.12 0.39 0.53 2.07 0.16 8.36 0.30 0.38
18b V 57.39 0.91 16.97 6.55 0.04 3.01 1.04 1.19 3.22 0.23 8.64 0.75 0.42
18c V 58.42 1.38 19.43 6.75 0.05 2.15 0.32 0.54 1.83 0.16 8.06 0.47 0.42
18d R 55.69 0.99 18.38 7.82 0.06 2.66 0.31 0.84 2.88 0.14 4.52 4.00 1.12
18e R 54.31 1.59 19.92 9.88 0.16 2.24 0.38 0.54 2.50 0.16 7.64 0.60 0.31
18£ V-R 54.66 1.66 21.13 7.04 0.09 2.26 0.44 0.59 2.17 0.16 9.24 0.64 0.48
18g R 54.30 L~6 20.10 9.60 0.15 2.10 0.57 0.64 2.34 0.17 7.89 0.10 0.44
18h R-V 52.83 1.14 16.45 7.00 0.07 2:86 1.05 0.70 2.48 0.16 7.68 6.99 0.73
18i V 49.94 1.01 15.29 6.22 0.06 2.80 0.78 0.70 2.50 0.14 6.22 13.98 0.87
181 V 37.80 0.71 12.04 4.46 0.03 1.95 0.65 0.43 1.67 0.10 ~ 3.76 35.96 0.29
18m V 51.44 1.04 16.07 6.51 0.06 2.85 0.75 0.68 2.56 0.16 5,74 11.48 0.74
18n R 34.66 0.56 9.43 4.70 0.11 1.73 0.53 0.30 0.96 0.08 2.65 43.66 0.24
18o V-R 58.04 1.31 16.73 7.78 0.10 2.63 0.52 0.67 2.26 0.15 4.10 4 .. 99 0.64
19a R 54.64 1.62 24.30 6.92 0.08 1.70 0.21 0.51 2.19 0.16 4.96 2.57 0.58
19b V 54.78 1.36 22.79 6.77 0.06 2.66 0.23 0.68 2.61 0.16 5.45 2.06 0.89
19c V 57.86 1.15 19.89 6.55 . 0.04 2.75 0.26 1.05 2.93 0.14 4.33 2.95 0.83
19d V 49.75 1.04 18.35 5.97 0.05 2.36 0.67 0.63 2.47 0.16 7.48 10.48 0.63
19e R-V 52.78 1.35 20.78 9.08 0.11 2.60 0.31 0.58 2.67 0.19 6.82 1.67 1.07
20 V-R 56.60 1.29 17.54 6.60 0.06 2.21 0.30 0.56 1.66 0.16 7.68 4.59 0.95
21 R 43.96 1.42 17.54 7.31 0.13 1.81 0.25 0.44 1.75 0.13 2.61 22.98 0.55
22a V 51.92 1.56 24.16 6.17 0.06 1.44 0.26 0.61 1.48 0.16 6.92 4.95 0.56
22b V 49.72 1.26 20.41 5.66 0.08 1.94 0.21 0.52 2.10 0.15 6.72 10.98 0.71
22c V-R 49.32 1.27 20.67 6.18 0.09 2.21 0.46 0.53 2.55 0.15 7.78 8.04 0.89
All samples
x 50.68 1.30 18.78 7.07 0.09 2.19 0.49 0.59 2.09 0.16 6.32 9.82 0.59
(J 6.82 0.27 3.61 1.35 0.03 0.57 0.27 0.16 0.53 0.03 2.01 12.49 0.25
Samples from 1 to 17 c
x 49.37 1.34 18.99 7.08 0.09 2.07 0.50 0.54 1.93 0.16 6.33 11.22 0.53
(J 4.47 0.22 3.84 1.11 0.02 0.68 0.30 0.11 0.49 0.03 2.13 13.70 0.24
Samples from 18a to 22c
x 51.94 1.26 18.58 7.06 0.08 2.31 0.47 0.63 2.25 0.15 6.32 8.48 0.64
(J 6.04 0.30 3.46 1.56 0.04 0.43 0.25 0.19 0.52 0.03 1.93 11.36 0.25
•"c--

Compositional Characteristics of i,Argille Vai-icolori» ... 227
TABLE 5
Comparison between chemical and mineralogical composition
Average mineralogical
Chemical composition
composition I s !IS K Ch F
(1) (2) (3) (4) (5) (6) (a) (b). (c)
Mixed-layer = 11% SiOz 50.7 59.6 54.6 45.5 25.7 63.4 58 .. 6 57.5 59.6
Smectite =55% Alz03 26.7 22.0 25.4 38.7 20.0 21.7 22.3 21.3 22.0
Illite = 7% Fez03 5.0 4.0 3.6 1.6 20.7 4.4 8.0 4.4
Kaolinite = 10% M gO 2.8 3.5 2.9 0.3 21.8 3.9 2.5 2.6
Chlorite 6% CaO 0.3 1.2 0.4 0.5 3.1 0.8 0.7 0.7
Quartz 9% ·K 2 0 7.1 0.8 5.9 4.9 1.7 2.4 2.5
Feldspars 2% NazO 0.2 0.3 0.2 6.9 0.3 0.6 0.6
Hzo+ 7.2 8.4 7.0 13.9 11.3 7.9 7.1 7.4
(1), (2), (3), (4) from WEAVER & POLLARD (1973); (5) from GRIM (1953); (6) from DEER et
al. (1963), using a 2:1 ratio between oligoclasic plagioclases and K-feldspars. (a): chemical
composition calculated from the mean values of the mineralogical data; (b): mean values of
the chemical analyses; (c): meari values of the chemical analyses corrected after elimination
of excess Fe 2 0 3. Symbols as in Table 3
sification (Fig. 3) indicates that 84%
of the samples are shales; the others
are marls.
The samples from Calitri, compared
to the Bisaccia ones, are richer
both in mixed layer illite-smectite (~
= 16% compared to x = 5%) and in
kaolinite (x = 10% compared to x =
7%), whereas they are poorer in
smectite (x = 42% compared to x =
59%).
Chemical characteristics
The samples analyzed (Table 4)
as well as the carbonate components
(CaC03 and MgC03), consist mainly
of SiOz, Ab03, FezO;, HzO, MgO, K 2 0,
and TiOz. The amounts of other components
are less than 1%.
The average chemical composition
agrees well with' that calculated by
the average mineralogical one (Table
5), excluding the excess of Fez03
which derives from the Fehydroxides
not detected by XRDCO.
Distributing this excess, estimated as
3.6%, among the other oxides, small
discordances are found only in MgO
and KzO. To explain these discordances
one can suggest that smectite is
overestimated with respect to illite
and mixed layer illite-smectite, or·
that K-rich smectite is present.
According to mineralogical data,
the reddish samples are richer in
Fez03 than the greenish ones; on the
contrary no differences occur between
samples from Calitri and those
from Bisaccia. Evidently, the mine-
(I) TiOz, MnO and PzOs are not considered in the comparison between chemical and mineralogical
analyses because of their low contents in clay minerals. In any case it is evident that the amount of
Ti0 2 in the clays examined is higher than that which one can expect from mineralogical composition;
thus the presence of Ti-oxides and! or Ti-hydroxides can be hypothesized.·

228 M. Di Pierro, M. Moresi
ralogical differences are not able to influence
the chemical homogeneity.
Concluding remarks
The «argille varicolori>> outcropping
near Calitri and Bisaccia consist
of pelites, with a quite fine grain-size,
that are classifiable texturally as clay
and clayey-silts, and mineralogically
as shales and clay marls; thus they
are similar to other «argille varicolori>>
from southern Italy (BELVISO
et al., 1977; AMICARELLI et al.,
1977; ABBATICCHIO et al., 1981).
The grain size distribution of the
clays indicates sedimentation in a
quite deep basin and gravitational
d-ep-osition- oCgraiD.s- a1ier -a long
transport in suspension. However, in
both olistostromic and landslip deposits
that represent two different
geological states, some poorly sorted
sediments are present that show a
grain size distribution with maxima
also in the silt and sand fields; thus
one can suppose that the basin underwent
depth changes and locally the
sedimentation occurred from a slow
turbidity current.
The mineralogical assooatwn
(smectite, kaolinite, mixed layer I/S,
Fe-hydroxides), the low crystallinity
of clay minerals, the relatively high
amount of Ti, and the almost complete
absence of secondary minerals,
all suggest, according also to ABBA-
TICCHIO et al. (1981), that grains de-
··· rive from the' ;>

Compositional Characteristics of

230 M. Di Pierro, M. Moresi
MALESANI P., MANETTI P., 1970. Proposta di classificazione dei sedimenti clastici. Mem. Soc. Geol. It.
9, 55-63.
MrLNER H.B., 1962. Sedimentary Petrography. J. Alien & Unwjn, L-o!!clQl!~ ~-~.-- _______ _ __
OGNIBEN L., 1969. Schema introduttivo alia geo/ogia del confine Calabro-Lucano. Mem. Soc. Geol. It.
8, fasc. 4, 453-763.
PESCATORE T., SGROSSO I., ToRRE M., 1970. Lineamenti di sedimentazione e tettonica ne/ Miocene
dell'Appennino Campano-Lucano. Mem. Soc. Nat. in Napoli, suppl. al Boll. 78, 1969, 337-406.
RArsH H.D., 1964. Quantitative mineralogical analysis of carbonate rocks. Texas J. Science 16, 172-
180.
RIVIERE A., 1977. Methodes granulometriques. Techniques et interpretation. Masson et Cie~ Paris.
ScHULTZ L.G., 1964. Quantitative interpretation of mineralogical composition from X-ray and chemical
data for the Pierre Shale. Prof. Pap. U.S. geol. Surv. 391-C, i-31. ·
SHEPARD F.P., 1954. Nomenclature based on sand-silt-clay ratios. J. Sediment. Petrol. 24, 151-158.
SRODON J ., 1981. X-ray identification of randomly interstratified illite-smectite in mixtures with discrete
illite. Clay Minerals 16, 297-304.
TREADWELL F.P., 1954. Trattato di chimica analitica. Vallardi, Milano, 2, 543-544.
WEAVER C.E., PoLLARD D., 1973. The Chemistry of Clay Minerals. Elsevier.
WEBER F., 0UNOYER DE SEGONZAC C., ECONOMOU C., 1976. Une nouvel/e expression de /a «crista//initb
de /'illite et des micas. Notion d'epaisseur apparentes des cristallites. C.R. Somm. Soc. Geol. Fr. 5,
225-227.

Miner. Petrogr. Acta
Vol. 29-A, pp. 231-243 (1985)
Mineral Composition of the Jurassic Sediments in the
Subbetic Zone, Betic Cordillera, SE Spain
M. ORTEGA HUERTAS, I. PALOMO DELGADO, P. FENOLL HACH-ALI
Departamento de Cristalografia y Mineralogia de la Facultad de Ciencias and Departamento de Investigaciones
Geol6gicas del C.S.I.C., Universidad de Granada, 18002 Granada, Espaiia
ABSTRACT- In this paper we present the mineralogical results of our study of
the External Subbetic sequences (Betic Cordillera, Spain) and establish an
initial comparative analysis with regard to the geological environment of
these deposits and the paleogeography of the Jurassic basin in both the
Median and External Subbetic realms.
The mineralogy consists of calcite, dolomite, quartz, K-feldspar, illite, chlorite,
kaolinite, smectite and mixed-layer illite-smectite.
In both realms the stratigraphic sequences are transgressive moving towards
the top and the most internal zones. From our study of all of the sequences
we have been able to conclude that no relationship exists between any particular
lithological facies and any one mineral association.
Introduction
The Betic Cordillera forms the
westernmost part of the Alpine
Mediterranean chains. Two main
geological realms can be distinguished
(Fig. 1): (i) the Internal
Zones, which consist mainly of overthrust
units of Triassic and
Palaeozoic materials, although in
some units, Mesozoic, Tertiary and
probably Precambrian ·terrains can
also be found, and (ii) External Zones
called Prebetic and Subbetic Zones
(BLUMENTHAL, 1927; FALLOT,
1948). In the Subbetic Zones it is
possible to identify thre~ sedimentary
realms through the facies
and the thickness of the Jurassic
materials: External Subbetic, Median
Subbetic and Internal Subbetic
(GARCIA DUENAS, 1967; FONT­
BOTE, 1970). In the External Zones,
Palaeozoic materials are not exposed.
The cover consists mainly of Mesozoic
and Lower Miocene materials.
Since 1980 the Authors have been
carrying out mineralogical research
within the grey marls and marly
limestone facies which make up part
of the Jurassic sequences of the Median
Subbetic Zone (PALOMO DEL­
GADO et al., 1981, 1985). The geological
and mineralogical importance
of this facies has been pointed out in
the above mentioned works.
In this paper we present the results

232 M. Ortega Huertas, I. Palomo Delgado, P. Fenoll Hach-Ali
of our mineralogical study of the External
Subbetic sequences and establish
an initial comparative analysis
between the geological environment
of this deposit and the palaeogeography
of th5!~-lP:r::

Mineral Composition of the JurassicSediments ... 233
Geological setting, lithological fades
and age of the materials studied
A scheme of the geological aspects
of greatest interest, such as the location
of the stratigraphic these sequences,
together with those of the
Median Subbetic, can be seen in
Fig. 1.
The spatial and temporal distribution
of the types of lithological facies
studied and their geological context
appear in Fig. 2. As can be deduced
from this figure we have not always
been able to collect specimens of
marly limestone and marls in the
field. The greater part of older materia]s,
below those which we have studied,
are non-detrital facies and ca~bonate
platform facies (bioclastic
wackestone, crinoidal grainstone,
mudstone with chert). In places,
SW NE SW-L~
~1edian Subbetic External Subbetic
SE CO z CM LC HU GU MAJ FV
B 4 4 4 5
MD 3 6 5
LD 3 6 5
uc 2 3 6 5
Fig. 2 - Spatial and temporal distribution of the types of lithological facies studied. B: Bajocian;
A: Aalenian; UT: Upper Toarcian; MT: Middle Toarcian; LT: Lower Toarcian; UD: Upper
Domerian; MD: Middle Domerian; LD: Lower Domerian; UC: Upper Carixian; 1: Bioclastic
wackestone; 2: Crinoidal grainstone; 3: Hiatus; 4: Radiolarites; 5: No outcrops; 6: Mudstone with
· chert. '

234 M. Ortega Huertas, I. Palomo Delgado, P. Fenoll Hach-Ali
either a hiatus exists or the materials
of these ages do not outcrop. The upper
limit of our sampling is determined
by the disappearance of the
detrital facies (presence of radiolarites,
bioclastic wackestone, «ammonitico
rosso», etc.) or by the lack of
the more modern material outcrops.
Nevertheless, we have been able to
collect sufficient mineralogical, stratigraphic
and paleontological data
from a sufficiently representative
area of the detrital facies in the
Subbetic Zone to present an
initial hypothesis concerning the
palaeogeography of this Jurassic
basin.
Methods and results
We analyzed the samples by X-ray
diffraction using a Philips
diffractometer, PW -1710, under the
following experimental conditions:
CuKa radiation, Ni filter and a speed
of zo 26 per minute. We prepared
several classes of samples: a) untreated
dry powder specimens, b)
oriented specim~ns, c) ethyleneglycol
and dimethyl-sulphoxide saturated
oriented specimens, and d)
heated to 550 oc oriented specimens.
For the oriented samples we chose
to. use clay J'S~J-LP1Cl.E.> 7 60 33
«Guarrumbre>> 7 59 34
«Majarazan>> 10 50 40
«Fuente Vidriera>> 11 50 39

Mineral CompositiQn of the Jurassic S~diments ... 235
/
C+D
C+D
Q+FdK •••
. ·.·· ...
- ... : .. :·· ·:·
CM
~
C+D
=
CM
Q+FdK
o HU
o GU
• LC
D FV
" MAJ
\
Q+FdK
... ..:: . . ·.
Q+FdK
"FV"
C+·f;D-----------~CI~
CM
C+D
CM
C+D
Fig. 3 - Triangular diagrams showing the mineral composition. The average composition of the
stratigraphical sequences is plotted in the central triangle. C: Calcite; D: Dolomite; Q: Quartz;
FdK: Potassium feldspar; CM: Clay minerals.
CM
LT
UD
-
~:::;::::::::::VZ/// //M
~:n:F/2//~
MD~~
LD
-
1 2 3 4 6 7 9
~~D~-
Fig. 4- Mineralogical composition of the sequence. 1: Calcite; 2: Quartz; 3: Clay
minerals; 4: Dolomite; 5: Potassium feldspar; 6: Illite; 7: Chlorite; 8: Kaolinite; 9: Smectite;
10: Mixed-layer illite-smectite; B: Bajocian; A: Aalenian; UT: Upper Toarcian; MT: Middle
Toarcian; LT: Lower Toarcian;. UD: Upper Domerian; MD: Middle D9merian; LD: Lower
Dometian; UC: Upper Carixian.

236 M. Ortega Huertas, I. Palomo Delgado, P. Fenoll Hach-Ali
opposed to «HU» and «GU».It is thus
possible to deduce that the external
sequences probably received mineral
contributions from several sources.
Clay minerals (

Mineral Composition of the Jurassic -S~irnents ... 237
Total
< 21'-
0 % 100 0 % 100
~mY?ZZZZZI ~~--------------~•
~~~~~~
------
------
~ -=-=-=~-=-
. ~M!Iili::f///7/J
t!Z?%?????£???i0MM!iJP7/Z/d
~i.~!tfT//2//'lJ
-
LT - - -
~JIMI7/Z~
- - -
T ~/i\UfZ/ZZ/1
-1
~~q=l15m
~~581 ~~~~~~~
Fig. 6- Mineralogical composition of the «Guarrumbre» seque~ce. Legend as in Fig. 4.
associations of clay minerals according
to whether or not they occur and,
if so, their relative abundance. Thus,
the following associations can be
distinguished:
Association A: I, Chl, K
Association B:'I, Chl, (Sm)
Association C: I, Chl, Sm
Association D: I, Chl, I-Sm (only
present in the Median Subbetic)
Association E: J, Chl
The italics indicate the presence of
certai'D. minerals considered to be indicative
and the brackets indicate
that, although the presence of a
mineral is constant through the sequence,
it is only present in small
proportions.
Spatial and temporal distributions
of these associations and their relationship
with the lithology of the various
sequences are shown in Fig. 9.
Comparative study of the sedimentation
in the Median and Extemal Subbetic
The bulk mineral composition at
both palaeogeographical realms is

238 M. Ortega Huertas, I. Palomo Delgado, P. Fenoll Hach-Ali
Total
< 2~J-
O % 100 0 %
t%'0'02{;:lWit\l!fT///J/~A ·I···--·.-----·-------~---
100
00
LT
UD
T
3m
1""~
77777777777777770·m.m:m""'111f,...2'"2'"/,__2,...,/,....,/1
1 2 3 6 7 . 10
-------- -~- D - -
Fig. 7 - Mineralogical composition of the «Majarazan» sequence. Legend as in Fig. 4.
very similar: calcite, quartz, dolomite,
K-feldspar and clay minerals
(illite, chlorite, kaolinite, smectite
and mixed-layer illite-smectite).
Nevertheless, the quantitative study
of the bulk mineralogy reveals significant
differences, which are expressed
graphically in Fig. 10. Figure lOa
shows clearly that the standard deviation
of percentage for any of the
minerals under discussion is greater
in the Median Subbetic sequences. In
fact, the coefficients of variation (V)
for quartz+ K-feldspar reach values
of between 30 and 43 in the Median
Subbetic, while in the External Subbetic
they range between 10 and 21.
Similarly the values of V for the carbonates
(calcite+dolomite) range
from 4 to 32 and 7 to 17, and for the
clay minerals from 7 to 34 and from
11 to 19 in the Median and External
Subbetic sequences, respectively.
According to our data, the stratigraphic
sequence which registers the
largest quantitative variations in
the three mineral groups is «Zegri»,
in the Median Subbetic, with V=
43 (quartz+ K-feldspar), V=32
(calcite+dolomite) and V=34 (clay
minerals). In the External Subbetic
the maximum values are to be found
in the

Mineral Composition of the Jurassic Sedifhents ... 239
-----::
------
------
rt~~~~~
Ill I
------
------
------
M T ~===~====
------
------
------
------
------
------
------
------
~--------­
.-------
Wm~J;AJWfZ/7d~ 0 ~i\111117/Z//111
0 ~~~~~~

240 M. Ortega Huertas, I. Palomo Delgado, P. Fe"'!oll Hach-Ali
Hues car
La Cerradura
UD :: ;,
-·. ~,;
LTII'
MD :: ii
"" " ;
• uc ~:
GRANADA
. l
0 -=-- 10 20 km
Fig. 9- Spatial and tempera! distribution of mineralogical associations and their relationship with
the lithology of the various sequences. A: I, Chi, K; B: I, Chi, (Sm); C: I, Chi, Sm; E: /,Chi. Ages as in
Fig. 2.
other hand, the deepening of the
basin and/or a distancing of the internal
zones from~the-continen.t, With a
corresponding variability in sedimentation,
and furthermore, the·
possible existence of emerging areas
(«Dorsal Medio-Subbetica», BUS­
NARDO, 1979) all go towards explaining
the high values for the
coefficients of variation which we
have encountered. An especially revealing
example of this occurs as we
have mentioned above, in the «Zegri».
sequence. We shall return to this
· palaeogeographical swell site later
on.
When we relate the different ages
of the materials studied to the coefficients
of variation (Fig. lOb) it is clear
that much greater variability is to be
found in the Median Subbetic sequences
than in the External ones.
In the latter sequences the highest
values of V (quartz+ K-feldspai- .
"SE
"CO
"Z"'
"CM
"LC
11
HU
"GU
"MAJ
Q+Fd
C+D
CM
5 10 16 20 40 50 60 25 45 55
+ +
I....,_ r-
--
+ """
I
_,.....
I
'!'
~
"oF
q,
...,...
......
c:p
~
of
UT
MT
c::P =F LT
9= t:P
q, q,
UD
MD
=P c:::p
9= c:::p
(a)
- median subbetic c::::J external subbetic
5
Q+Fd C+D CM
9 14 19 28 32 40 50 60 68 22 30 40 50 58
+ -;- .,.
+ --1- -1-
.,. I
q,+
I
q, cp
of:,
......
-I
....,_=!=
....,...
I
--,- q,
c:::p+
~
cP
~ cP
cb
Fig. 10 - Mineralogical composition. (a): in relation with the sequences studied; (b): in relation
with the age of the materials. The standard deviation is indicated by the bar and the arithmetic
average by the cross-bar. Legend as in Fig. 4.
(b)
c6
_.2
I
'fi
cp

Mineral Composition of the Jurassic Sediments ... 241
=26, calcite+dolomite=20, clay
minerals= 17) correspond to the Lower
Toarcian, while in the Median
Subbetic we have been unable to unequivocally
assign the materials to a
period with any precision. In any
case the Domerian-Toarcian limit is a
moment in geological history characterized
by a crisis in the development
of the fauna, with a disappearance
of benthonic organisms, evidence
of predominantly juvenile
forms and the existence of euxinic
conditions (BRAGA et al., 1982). All
these facts could be related to the
mineral characteristics described
above, such a variation in the mineral
content and a decrease in the proportion
of carbonate materials present.
The study of clay minerals and the
establishment of various mineraf
associations (PALOMO DELGADO et
al., 1985) has enabled us to carry out
a comparative study of the geological
environment of the deposits in the
Median and External Subbetic (Fig.
11). Our conclusions concerning its
temporal and spatial evolution
appear below.
We have found similar mineral
associations in the External Subbetic
and in the Median Subbetic. In the
External Subbetic, however, we have
SW NE SW-~~ NE-E
SE CM LC FV
B
MD
LD
uc
Fig. 11 - Relationship between the lithology of the sequences and the mineral associations.
Lithology: 1, Grey marls and marly limestone; 2, «Ammonitico Rosso» facies; 3, Red and pinky
limestones, sandy marls and grey marls; 4, Limestones and marls with chert nodules; 5, Nodular
limestones; 6, Brown marls. Clay mineral associations: A: I, Chi, K; B: I, Chl, (Sm); C: I, Chi, Sm;
D: I, Chi, I-Sm; E: I, Chl. Ages as in Fig. 2. .

242 M. Ortega Huertas, I. Palomo Delgado, P. Fenoll Hach-Ali
identified a new association E, made
up of illite+chlorite.
In both realms the stratigraphic
sequences are transgresive moving
towards the top. This might correspond
to the t;ransgression which began,
according to HALLAM (1978),
at the Carixian-Domerian limit of
the global curve of transgressionregression
during the Jurassic.
It is clear that, in any specific age,
the sequences are also transgressive
towards the most internal zones, that
is to say, toward~ the SW. Thus the

Mineral Composition of the Jurassic Sediments ... 243
were eroded, and which probably
also descended from the Variscan
Massif of the Meseta~.
As a final comment, the presence of
kaolinite in the sequence lying a long
way from the probable source rocks
(«Z» and «CM>> of the Median Sub betic
and only in the Lower Toarcian of
the sequence «HU >> of the External
Subbetic) suggests the possibility of
the existence of BUSNARDO's «Dorsal
Medio Subbetica>> (1979) situated
between the Median Subbetic and
the External Subbetic, which may
have been above water at some
period.
REFERENCES
BARAHONA FERNANDEZ E., 1974. Arcillas de ladrilleria de la provincia de Granada: Evaluaci6n de
algunos ensayos de materias primas. Ph. D. Thesis, University of Gr:;mada, Spain.
BLUMENTHAL M.M., 1927. Versuch einter tektonischen Clerederung der Betischen Cordilleren von Central
und Sii.dwest (Andalusien). Eclog. Geol. Helv. 20, 487-532.
BRAGA J .C., GARCIA GOMEZ R., JIMENEZ A.P., RrvAs. P., 1982. Correlaciones en el Lias de las Cordilleras
Beticas. P.I.C.G. Real Acad. Ciencias Exactas, Fisicas y Naturales, Madrid, 161-181.
BUSNARDO R., 1979. Prebetique et Subbetique del aen a Lucena (Andalusie). Introduction et Trias. Doe.
Lab. Geol. Fac. Sci. Lyon.
CABALLERO M.A., LOPEZ AGUAYO F., 1973. Estudio comparativo de la mineralogia de arcillas de
sedimentos triasicos Wealdenses espaiioles. Estudios geol. XXIX, 563-568.
FALLOT P., 1948. Les Cordilleres Betiques. Estudfos geol. VIII, 83-172.
FoNTBOTE J.M., 1970. Sobre la historia preorogenicq. de las Cordilleras Beticas. Cuad. Geol. Univ.
Granada I, 71-78.
GARCIA DuENAS V., 1967. Unidades paleogeograficas en le sector central de la Zona Subbetica. Corn.
Inst. Geol. Min. Espaii.a CI-CII, 73-100.
GARCIA HERNANDEZ M., LOPEZ GARRIDO A.C., RIVAS P., SANZ DE GALDEANO C., VERA J., 1980. Mesozoic
paiaeogeographic evolution of the External Zones of the Betic Cordillera. Geol. en Mijnbouw 59,
155-163.
HALLAM A., 1978. Eustatic cycles in the Jurassic. Palaeogeogr. Palaeoclimat. Palaeoecol. 23, 1-32.
LOPEZ GARRIDO A.C., VERA J., 1979. Mapa de distribuci6n de Unidades en la Zonas Externas de /as
Cordilleras Beticas. In: «La microfacies de Jurasico y Cretacico de !as zonas externas de !as
Cordilleras Beticas». University of Granada, L.S.B.N. 843380133.3.
PALOMO DELGADO I., 0RTEGA HUERTAS M., FENOLL HACH-ALI P., 1981. Los carbonatos de la facies
margosas /urasicas en las Zonas Externas de las Cordilleras Beticas (Provincias de Granada y
Jaen). Bol. Soc. esp. Min. 4, 15-28.
PALOMO DELGADO I., 0RTEGA HUERTAS M., FENOLL HACH-ALI P., 1985. The significance of clay minerals
in studies of the evolution of thelurassic deposits of the Betic Cordillera. SE Spain. Clay Minerals
20, 1-14.
SCHULTZ L.G ., 1964. Quantitative interpretation of mineralogical composition from X-ray and chemical
data for the Piere Shii.le. Prof. Pap. U.S. geol. Surv. 391-C.

Miner. Petrogr. Acta
Vol. 29·A, pp. 245-257 (1985)
Pelagic Cretaceous Black-Greenish Mudstones
in the Southern Iberian Paleomargin,
Subbetic Zone, Betic Cordillera
A. LOPEZ GALIND0 1 • 3 , M.C. COMAS MINOND0 2 • 3 , P. FENOLL HACH~ALI 1 • 3 ,
M. ORTEGA HUERTAS 1 • 3
I Departamento de Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Granada, 18002 Granada,
Espai\a "
2 Departamento de Geologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada, Espai\a
3 Departamento de Investigaciones Geol6gicas del C.S.I.C., Universidad de Granada, 18002 Granada, Espai\a
ABSTRACT- In the Betic Cordillera, the Prebetic and Subbetic Zones were a
part of the southern margin of the Iberian plate. In the light of recent
oceanographic and geological research, several authors have maintained
that the palaeogeographic evolution of this margin occurred during the
Jurassic in a transformant geodynamic setting, the maximum extension tak­
·ing place ·during the Cretaceous. ·
The pelagic Cretaceous mudstones here studied, argil!aceous, highly
siliceous and carbonate poor, belong to some of the trough realms originated
in the continental margin, from the Aptian to the Lower Senonian, in the
expansive regime outlined above. The Aptian-Cenomanian black and greenish
mudstones are interbedded with turbiditic limestones and chaotic conglomerate
facies, contaihing clastic materials from the adjacent pelagic
swell. The turbiditic and the pelagic pelites of these facies have been typified
and differentiated by their mineralogical characteristics. The clay minerals
in the pelagic mudstones are smectites (60-80%), illite (15-25%), and palygorskite
(10-20%) from the Southern Middle Subbetic (Fardes Formation),
and illite (70-85%), chlorite (15%), kaolinite (10-15%) and mixed-layer illitesmectite
(5-15%) from the Northern Middle Subbetic.
Introduction
It has traditionally been agreed that
the External Betit Zones made up ~f
Mesozoic and Cenozoic cover materials,
are subdivided into two main
palaeogeographical realms, to the
north the Prebetic Zone and, to the
south, the Subbetic Zone. These form
part of the southern margin of the
Iberian Plate, the geodynamic evolution
which has been interpreted in
many different ways (BOURGOIS,
1980; VERA, 1981; MALOD, 1982;
WILDI, 1983, among others). It has
been suggested recently that the
Mesozoic palaeogeographical evolution
of this margin took place in a
transtensive regime, which reached
its maximum extension during the
Cretaceous (GARCIA-DUENAS &

246 A. L6pez Galindo, M.C. Comas Minondo, P. Fenoll Hach-Ali, M. Ortega Huertas
COMAS, 1983; COMAS & GARCIA­
DUENAS, 1984). The pelagic, Cretaceous,
black-greenish facies investigated
in this paper would correspond,
according to this latter geodynamic
interpretation, to deposits laid
down in an age when the South Ibe­
-rian margin was at its maximum extension
(Aptian to Lower Senonian).
Palaeogeographically, these facies
belong to the Middle Subbetic subdominion,
of the Subbetic realm
(GARCIA-DUENAS, 1967; GARCIA­
HERNANDEZ et al., 1980), which, in
the Lower 'Cretaceous, was characterized
by the widespread creation of
thick, uniform sequences of marls
and greyish-white, pelagic, nanno-
------ -- -plankton::rich. 1iffiestones, ·- incl~ding
intercalated slump-beds.
· After the Aptian the facies show a
greater diversity of deposits, which
indicates that the physiography of
the basin was substantially modified,
almost certainly due to the
palaeogeographic reorganisation
which the South Iberian margin
underwent at that time (COMAS &
GARCIA-DUENAS, 1984). In this
new physiography several basinal environments
flanked by pelagic swells
were formed. Within these environments
singular types of pelagic facies
(clayey and cherty mudstones) and
redeposited facies (carbonate turbidites
and olistostromes) accumulated
in turn.
In this paper we intend to examine
the mineralogical characteristics of
the Aptian-Cenomanian black-shaletype
deposits of the basinal environments
within the Middle Subbetic.
We also classify and differentiate the .
minera.logicaLcompositionofthe turbiditic
pelites and hemipelagites
which have accumulated in this type
of sedimentation environment.
In order to carry out this investigation
we studied the facies found in
two of the basinal environments: the
first is located in the Northern Middle
Subbetic (NMS), and consequently
closer to the foreland, and the
second is located in the Southern
Middle Subbetic (SMS) (GARCIA­
DUENAS, 1967). The Cretaceous
sequences in which both types of pelites
are contained outcrop in the central
third of the Subbetic Zone, to the
N-NE of Granada, as shown in Fig. 1.
Sedimentological setting
In order to study the mineralogical
characteristics of the black-shaletype
facies in the Southern Middle
Subbetic we chose the sequences belonging
to the Fardes Formation
(COMAS et al., 1982). In this formation
various associations of pelagic
facies and deep-carbonate clastic
facies coexist. The pelagites are
clayey and/or cherty and are dark
green or red in colour. The clastic
carbonate lithologies (conglomerates,
calcarenites, calcilutites) are to
be found below different types of turbiditic
facies and in various associations.
According to COMAS MINON­
DO (1978) the nature of the associations
of the facies and the existence of
certain sequential units iri the Fardes
Formation indicate that deep-sea·

Pelagic Cretaceous Black-Greenish Mudsto-iies ... 247
0 100 200 300 km
'------'-----"----------' ..

248 A. L6pez Galindo, M.C. Comas Minondo, P. Fenoll Hach-Ali, M. Ortega Huertas
bined with gravity was instrumental
in the appearance of the clasts. Furthermore,
the pelagic sediments ~ere
also carried down from the swells to
form the turbiditic pelites. In this
formation, pelagic facies, poor or free
of carbonates, are variously associated
with turbiditic carbonates, depending
on the. different subenvironments
within this basin. COMAS
MINONDO (1978) has attributed the
·. ~'~aterials which make up the Fardes
Formation to the Albian-Lower Senonian.
In order to determine the character
of the NMS pelites, we studied materials
belonging to the Morales­
Carboneros sequence, located to the
SE ofValdepeiias de.Ja~n.-It is·~-ade
up of materials from the late Lower
Cretaceous and early Upper Cretaceous
(Vraconian). This Cretaceous
sequence belongs to the Ventisquero­
Sierra del Trigo Unit (SANZ DE GAL­
DEANO, 1973).
The Morales-Carboneros sequence
is composed alternatively of grey
marls and black clays, various types
of calcirudites and calcarenites, cherty
marls and radiolarites. The carbonate
clastic layers show turbiditic
facies, and several slump episodes
can be identified, thus some radiolaritic
facies represent resedimentation
episodes. The nature of the turbiditic
beds and the type of facies
which they show, together with their
organization all lead to the conclusion
that we are dealing with basinplain
deposits. The pelagic facies of
the NMS sequence show a greater
lithological variety than those of the
Fardes Formation since they normally
C()nt~ig li~ h_igl?:~r:J2L02Q!"_tj,9n_of carbonates.
One further point of importance
is that levels containing a large
quantity of bituminous material are
also present.
Mudstone mineralogy
We selected layers of special intere~t
within the sequences described
above, where there was a clear distinction
between the hemipelagites
and the turbiditic pelites, and took
samples of the sediments. We analyzed
a total of 60 samples by X-ray
diffraction using a Philips diffrac-
L tometer, PW-1710, under the following
experimental conditions: CuKa
radiation, Ni filter and a speed of 2°
26/min. We prepared several classes
of samples: a) untreated dry powder
specimens, b) oriented specimens,
c) ethylene-glycol and dimethylsulphoxide
saturated, oriented specimens,
and d) heated to 550 oc
oriented specimens. For the oriented
samples we chose to use clay fractions
(less than 2).l.m) and silt (between
2).l.m and 20).l.m). The semiquantitative
analysis was carried out
with reference to the reflecting powers
described by BRADLEY & GRIM
(1961), SCHULTZ (1964), BISCAYK
(1965) and BARAHONA (1974).
In order to simplify the picture, we
have grouped the relat~ve abundance
of the different minerals into five
categories: principal constituent
(>50%), abundant (20%),
common (10%), scarce
(5%) and traces (

Pe{agic Cretaceous Black-Greenish Mudstones~:. 249
Mineralogy of the total sample
The minerals that are present in
the pelites of these sequences are:
phyllosilicates, quartz, calcite, feldspar
and pyrite. The proportions of
these minerals vary in each of the two
palaeogeogn:tphic realms. The presence
of dolomite and barite has also
been detected, although only in the
SMS dominion (COMAS et al., 1982;
LOPEZ GALINDO, 1984).
Figure 2 shows the quantitative
variation of the various minerals
throughout the SMS sequence
(Fardes Formation) together with a
triangular diagram representing the
composition of the hemipelagites and
the turbiditic pelites.
. The following facts are noteworthy:
1) the almost total absence of,
carbonates and the predominance of
phyllosilicates in the hemipel.agic pelites;
2) the quartz and the feldspars
are more abundant within the
hemipelagites compared to within
tht: turbiditic pelites (up to a ratio of
4:1); 3) the hemipelagites are mineralogically
more heterogeneous.
For these reasons each group occupies
a different position in the compositional
triangle.
In the NMS realm, however, the
mineralogical differences, both qualitative
and quantitative, are much
less clearly defined (Fig. 3). The only
variations of note are that the turbiditic
pelites of the lower half of the
sequence contain a greater quantity
of calcite than the hemipelagites, and
these contain slightly more quartz.
It can be seen in both sequences
~ .
1
D
m D -
2 3
[23 ~
C+D
[ili].
4
-Fd
~
Q+Fd ,
I
I
Q+Fct.
\
: .
• Hemi pelagites
x Turbiditic pelites
Fig. 2- Qualitative and quantitative variation of the minerals in the Southern Middle Subbetic and
triangular representation of their different compositions. 1: Carbonates conglomerates; 2: Sandstones;
3: Marls and clays; 4: Olistostromes; 5: Limestones and marly limestones. Q: Quartz; Fd:
feldspar; C: Calcite; D: Dolomite; P: Phyllosilicates.

250 A. L6pez Galindo, M.C. Comas Minondo, P. Fenoll Hach-AU, M. Ortega Huertas
•• 1
D
p
Q+Fd
Q+Fd
' \
'
• Hemipelagites
x Turbiditic pel ites
Fig. 3- Variation of the different minerals in a typical Northern Middle Subbetic sequence, together
with a triangular representation of the composition of the pelites. 1: Radiolarites and siliceous
clays; 2: Sandstones; 3: Clays and roads; 4: Carbonate sandstones. Q: Quartz; Fd: Feldspar; C:
Calcite; P: Phyllosilicates.
that phyllosilicates, carbonates and
quartz are the principal constituents
of the pelites. In the carbonate samples
the greatest component is calcareous
plankton and the quantity of
carbonates decreases towards the
bottom of the sequences.
Detritic quartz tends to be concentrated,
although in variable quantities,
in layers formed by the intermittent
arrival of deposited materials in
the basin. Biogenic quartz, principally
derived from radiolaria, is also
present: It tends to be found more in
the hemipelagic layers, due in part to
the dissolution of carbonate components.
Detritic feldspars exist in proportions
lower than 5% and are normally
associated with detritic quartz.
Clay minerals
The proportions and associations
of the clay minerals in the sequences
which we investigated are clearly distinct.
The mineral associations which
we encountered are: smectite-illitepalygorski
te-( chlori te-kaolini te) in the

Pelagic Cretaceous Black-Greenish Mudstbnes ... 251
Fardes Formation and illite-chlorite
-kaolini te-(interstratified illi te-smectite)
in the Morales-Carboneros sequence
(Table 1).
The mineralogical differences between
the hemipelagites and the turbiditic
pelites are shown graphically
in Figs 4 and 5. In Fig. 4 appears the
quantitative and qualitative evolution
of the clay minerals in the SMS
sequence, together with a triangular
diagram showing the composition of
both types of pelites.
Worthy of note are the high quantity
of illite (I) in the turbiditic pelites,
the dominance of palygorskite (Pa)
and smectites (Sm) in the hemipelagites
and the scarcity of chlorite (Ch)
and kaolinite (K) in both types of pelites.
On the other hand, in the NMS
realm (Fig. 5) all the samples are of a
similar composition with a predominance
of illite (70%), between 10-15%
kaolinite, around 5% chlorite, and, in
the clay fraction, 10-15% of interstratified
illite-smectite (I-Sm).
Other associated minerals
The existence of pyrite and of organic
material in both sequences is important
as regards the nature and
chemical conditions of the environment
during the period of deposition.
The colour of the black-shale facies
with which we are dealing here is frequently
due to the presence of pyrite
and siderite. These minerals are
formed after deposition and reflect
the degree of the anoxic conditions in
z
......
0
z
......
::2:
0
Cl
r:IJ
~·
r:IJ
r:IJ
~
z
TABLE 1
Mineralogical composition of the hemipelagites and
turbiditic pelites in Northern and Southern Middle Subbetic
.~
+->

252 A. L6pez Galindo, M.C. Comas Minondo, P. Fenoll Hach-Ali, M. Ortega Huertas
Hemi pe 1 ag i tes
I+ Ch
K
Sm + Pa
T
10m
l
-
~ §
Sm Pa K+Ch
I
I
/r +Ch
• Hemipelagites
x Turbiditic pel ites
Fig. 4 - Evolution of the clay minerals and triangular representation of the composition of the
pelites in the Southern Middle Subbetic realm. Sm: Smectite; Pa: Palygorskite; I: Illite; Ch: Chlorite;
K: Kaolinite.
' \
\
K
the interstitial and the deepest waters.
We have found pyrite in the
form of ovoid nodules, which must
have originated from disperse pyrite
during the early sedimentationdiagenesis
stage. Microscopic analysis
reveals that these nodules are
made up of pyrite, gypsum, goethite
and calcite, with traces of natrojarosite
(LOPEZ GALINDO et al., 1983).
With regard to the organic matter,
our analysis of SMS samples resulted
in values of less than 2%, although
they were somewhat greater in the
Morales-Carboneros sequence.
Although not to be found extensively,
it is also worth mentioning the
presence of barite in the hemi-,
pelagites of the Fardes Formation.
It appears in more-or-less rounded
nodules with a radiate-fibrous texture
and a maximum of 20 cm diameter.
These nodules bear no concordant
relationship with the stratification
of the hemipelagites and their
«cone in cone» texture leads us to

Pelagic Cretaceous Black-Greenish Mudstones:.: 253
Hemi pe 1 ag i tes
I+ Ch
I-Sm
K
I+ Ch
X 0 X
• X X•
X
X•
I
I
/I-Sm
\
\
\
K \
D ..
T
10m
1
~
I-Sm Ch K
• Hemipelagites
x Turbiditic pel ites
Fig. 5 - Evolution of the clay minerals and triangular representation of the composition of the
pelites in the- Northern Middle Subbetic realm. I: Illite; Ch: Chlorite; I-Sm: Mixed-layers illitesmectite;.K:
Kaolinite.
believe that they probably evolved
during the early sedimentationdiagenesis
stage, originated by the
oxidation of previous pyrite (LOPEZ
GALINDO et al., 1983).
On the basis of all our experimental
results discussed above
we have been able to typify and differentiate
the turbiditic and pelagic pelites
of these facies, as shown in Table
2.
Discussion
The results of our mineralogical
study throw light on several aspects
of the nature of the environment in

254 A. L6pez Galindo, M.C. Comas Minondo, P. Fenoll Hach-Ali, M. Ortega Huertas
TABLE 2
Characteristics of the pelites in the cretaceous materials studied
Characteristics
Hemipelagites
Colour
Thickness bed
Bioturbation
Calcite
Quartz
Feldspar
Ca/Q+Fd
Pyrite
Organic matter
grey/dark/green
< 20 cm.
widespread
4% (SMS); 7% (NMS)
23% average
occasionally (5%)
0.2
nodules/disseminated
trace and abundant in
some beds
grey
3-70 cm.
at the top
70% (SMS); 17% (NMS)
8% average
Clay minerals 76% average 24% average
(SMS): Southern Middle Subbetic; (NMS): Northern Middle Subbetic; Ca: Calcite;
Q: Quartz; Fd: Feldspar
10
which the sedimentation of the Cretaceous
pelites took place. Furthermore,
as we have investigated exam-
-~-----plesohwo diffefentSu55etic suberivironments,
we have been able to
analyse the differences in environmen,tal
conditions which existed in
the basin throughout the Cretaceous
palaeomargin. It must be remembered
here, that, almost certainly,
these subenvironments took the
shape of a configuration of independent
troughs flanked by swells.
- The mineralogy of the facies pro-
. vides a true picture of the nature of
these subenvironments. Thus, the authigenic
minerals such as palygorskite
and smectites, give clues to the
chemical composition, the minerals
affected by depths, such as carbonates,
clues to the bathymetry, and the
inherited materials, such as illi te,
kaolinite, chlorite and feldspars,
clues to the nature of the source areas
of the hemipelagic materials. The
presence in these hemipelagites of
other minerals indicative of the chemical
composition of the environment,
such as pyrite and organic matter,
can be interpreted as the result of lo-
. cal, isolated currents which existed at
a given moment, when essentially reducing
conditions prevailed, with no
regard to depth.
Precise calculations about depth
can be arrived at by taking into
account the presence or absence of
carbonate deposits. The absence of
these deposits in the hemipelagic -
facies of the SMS realm and part of
the NMS realm may be explained by
the fact that the depth of the water
exceeded the calcite compensation
depth (CCD), remembering that in
this epoch of the Cretaceous (Albian­
Cenomanian) nannoplankton flour:­
ished abundantly and provided a continuous
source for carbonate deposits.
In fact, within the Subbetic realm,
lateral correlations have been made
between black-shale-type facies and
carbonate facies.
On top of this, it is necessary to
take into account the presence of

organic materials in these facies,
which might be included in the
«Oceanic Anoxic Events» reported by
SCHLANGER & JENKYNS (1976)
and by JENKYNS (1980). In the opinion
of COOL (1982) the variations in
the carbonate and organic material
content coincided with the evolution
of intermittent anoxic conditions in
deep basins during the Middle Cretaceous.
The different associations of the
clay minerals, both separately and,
taken as a whole (Sm-I-Pa-K-Ch in
the SMS and I-K-Ch together with
I-Sm in the NMS), are an important
indicator of the difference in the
palaeogeography and the different
types of source materials which these
basins received.
It is clear that some of these miner
rals were inherited from older foreland
rocks, from soils formed on top
of these and even from the contemporary
swells which delimited the
basins themselves. This must be the
case with the illite, the chlorite and
the kaolinite. The small quantity of
the last jwo minerals in the SMS
compared to the NMS can be explained
by the fact that the former
subrealm lays further from the continental
foreland, and by the transformation
ofkaolinite'into micaceous
terms as a consequence of the high
chemical activity in the area of the
basin. The presence of high percentages
of palygorskite and smectites
supports this idea of chemical activity
in the basin area and points to the
conclusion that it was at its highest
in the more confined zone of the
Pelagic Cretaceous Black-Greenish Mudstones: .. 255
Fardes Formation. Processes of
neoformation and/or alteration of
volcanic rocks located close to and to
the south of the Fardes Formation
could be the explanation for the presence
of high proportions of these last
two minerals, although we have been
able to find no evidence of volcanic
activity in the Subbetic contemporary
to the formation of the sequences
studied.
Although the smectites could have
"evolved in a different environment
·and been carried to the deposit site in
suspension at a later date, together
· with quartz, illite, kaolinite, etc., the
very high quantity present (up to 85%
of the total) leads us to believe that
their origin, at least in part, may
have been from solid, principally volcanic
materials, rich in Si and AI,
with the Mg brought to the site in
'solution. According to LOPEZ­
AGUAYO et al. (1985) they may originate
from the alteration of continental
basalts.
Palygorskite is a typical product of
chemical precipitation in alkaline
basins, with a high ionic concentration
associated with carbonate precipitation
(WEAVER & BECK, 1977).
This type of basin normally has a
very limited communication with the
open sea or is completely isolated, resulting
in a stratification according
to the density of the water column. It
is worth noting that organic matter
occurs with considerable frequency
in this type of basin. With regard to
the manner in which this mineral
precipitates, WOLLAST et al. (1968)
maintain that when the pH is above

256 A. L6pez Galindo, M.C. Comas Minondo, P. Fenoll Hach-Ali, M. Ortega Huertas
7, it can occur directly in the presence
of appreciable quantities of Si
and Mg. On the other hand, VON
RAD & BERGER (1972) suggest that
it arises from a transfomation qf
smectite in Mg rich solutions if the
materials contain a sufficient quantity
of silicon hydrogels in their pores.
These would derive from the devitrification
of volcanic glass at high pH,
or the dissolution of the shells of
siliceous organisms.
All of the above leads to the conclusion
that the precipitation of palygorskite
is brought about by local
concentrations of Si02 and Ab03 in a
saline environment, with pH between
8 and 9.
-- ---~~--- -- --rn:conclusiOn~we woul"d-like to provide
a tentative picture of the physiography
of the sedimentary environment
in which the materials
under discussion in this paper were
dep~~i!~~:_~ -~13-£IA_:p(J~NAS &
COMAS (1983) maintain that the
different formations of the Subbetic
Zone, dating from between the
Aptian to the Lower Senonian
accumulated in a suspended basin,
situated on an extensive continental
margin.
Within this general physiographical
scheme we think that the South
Middle Subbetic may correspond to
a more southerly, deeper realm of
black-shales and the North Middle
Subbetic to a shallower realm of
clayey pelagic limestone with bituminous
levels. Both troughs were to a
certain extent restricted, with anoxic
conditions, which might vary from
,_age to age, and were affected by turbiditic
materials brought down from
adjacent higher levels.
REFERENCES
BARAHONA FERNANDEZ E., 1974. Arcillas de ladrilleria de la provincia de Granada: Evaluaci6n de
algunos ensayos de rnaterias prirnas. Ph. D. Thesis. University of Granada, Spain.
BrscAYE P.E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and
adjacent seas and oceans. Geol. Soc. Am. Bull.76, 803-832.
BoURGOIS J., 1980. Pre-triassic fit and alpine tectonics of continental blocks in the western Mediterranean:
Discussion. Geol. Soc. Am. Bull. 99, 332-334.
BRADLEY W.F., GRIM R.E., 1961. Mica Clay Minerals. Pp. 208-241, in: The X-ray Identification and
Crystal Structures of Clay Minerals (G. Brown, editor), Mineralogical Society, London. .
COMAS MINONDO M.C., 1978. Sabre la geologia de los Mantes Orientales. Sedimentaci6n y evoluci6n
paleogeografica desde el Jurasico al Mioceno inferior (Zona Subbetica, Andalucia). Ph. D. Thesis,
University of Bilbao.
CoMAS M.C., Rurz 0RTIZ P.A., VERA JA, 1982. El Cretacico de las Unidades Intermedias y de la Zona
Subbetica. Pp. 570-603, in:

Pelagic Cretaceous Black-Greenish M.udstones ... 257
GARCIA-DUENAS V., 1967. Geologia de la Zona Subbetica al N de Granada. Ph. D. Thesis, University of
Granada, Spain.
GARCIA-DUENAS V., CoMAS M.C., 1983. Paleogeografia Mesozoica de las Zonas Extemas Beticas coma
horde de la Placa Iberica entre el Atlantico y la Mesogea. Pp. 526-527. in: Acta X Cong. Nac.
Sedim., Menorca.
GARCIA-HERNANDEZ M., LOPEZ GARRIDO A., RIVAS P., SANZ DE GALDEANO C., VERA J.A., 1980. Mesozoic
paleogeographic evolution of the External Zones of the Betic Cordillera. Geol. en Mijnbouw 59,
155-168.
JENKYNS H.C., 1980. Cretaceous anoxic events: from continents to oceans. J. Geol. Soc. London 137,
171-188. . •
LOPEZ-AGUAYO F,, SEBASTIAN PARDO E., HUERTAS F., LINARES J.;·1985. Mineralogy and Genesis of the
«Fardes Formation» Bentonite, Middle Subbetic, Granada Province, Spain. These Proceedings.
LOPEZ GALINDO A., SEBASTIAN PARDO E., SANCHEZ VINAS M., 0RTEGA HUERTAS M., 1983. Natrojarosita
en las hemipelagitas de la Formaci6n Fardes (Cretaceo, Cordilleras Beticas). Bol. Soc. esp. Min. 7,
69-79. ~
LOPEZ GALINDO A., 1984. Intercalaciones arcillosas en turbiditas: hemipelagitas y pelitas turbiditicas.
Interpretaci6n en base a su mineralogia (Cretacico media-superior, Cordilleras Beticas, Andalucia).
Tesis Licenciatura, University of Granada, Spain.
MALOD J.A., 1982. Comparaison de /'evolution des marges continentales au nord et au sud de la
Peninsule Iberique. These d'Etat, Mem. Se. Terre, Univ. Curie, Paris.
SANZ DE GALDEANO C., 1973. Geologia de la transversal Jaen-Frailes (Prov. de Jaen). Ph. D. Thesis
University Granada, Spain.
SCHLANGER S.O., JENKYNS H.C., 1976. Cretaceous oceanic anoxic events: causes and consequences.
Geol. en Mijnbouw 55, 179-184.
ScHULTZ L.G., 1964. Quantitative in,terpretation of mineralogical composition from X-ray and chemical
data for the Pierre Shale. Prof. Pap. U.S. geol. Surv. 391-C.
VERA J.A., 1981. Correlaci6n entre las Cordilleras Beticas y otras cordilleras alpinas durante el Mesozoico.
Pp. 125-160, in: «Programa Internacional de Correlaci6n Geol6gica PICG>>. Real Acad.
Ciencias Exactas, Fisicas y Naturales.
VoN RAD U., BERGER W.H., 1972. Cretaceous and cenozoic sediments from the Atlantic Ocean. Pp.
787-954, in: «Initial Reports of the Deep Sea Drilling Project, XIV>> (Ha yes D.E. et al., editors),
Washington (U.S. Gov. Printing Office).
WEAVER C.E., BECK K.C., 1977. Miocene of the, SE USA: A model for chemical sedimentation in a
perimarine environment. Sedimentary Geology 17, 1-234.
WILD! W., 1983. La chafne tello-rifaine (Algerie, Maroc, Tunisie): structure, stratigraphie et evolution
du Trias au Miocene. Rev. Geol. Dyn. Geogr. Phys. 24, 201-297.
WoLLAST R., MACKENZIE F.T., BRICKER O.P., 1968. Experimental precipitation and genesis of sepiolite
at earth-surface conditions. Am. Miner. 53, 1645-1661.

t
I

Miner. Petrogr. Acta
Vol. 29-A, pp. 259-266 (1985)
Clay Minerals of Miocene-Pliocene Materials
at the Vera Basin, Almeria, Spain.
Geological Interpretation
E. GALAN 1 , M. GONZALEZ LOPEZ 2 , C. FERNANDEZ NIETO 2 , I. GONZALEZ
DIEZ 3
I Departamento de Geologia, Facultad de Quimica, Universidad de Sevilla, Apartado 553, 41071 Sevilla, Espafla
' Departamento de Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza,
Espafla
3 Secci6n de Geologia de la Rabida, Universidad de Sevi!la, Huelva, Espafla
ABSTRACT - Clay mineralogy of marly materials of two sections from the
Vera Basin (western Mediterranean) have allowed to differenciate two types
of sedimentary environmental conditions during the Miocene-Pliocene transition.
At the end of the Messinian times, sedimentation occurred in a brack:
ish environment, lacustrine or perimarine, characterized by the following
clay mineral s.uite: illite + smectite ± palygorskite ± sepiolite ± chlorite/
kaolinite ± paragonite. Later these conditions were slowly changed and
finally during the Pliocene times sedimentation took place in an open marine
environment. These last materials are characterized by an assemblage of
illite + smectite + chlorite/kaolinite ± paragonite.
In the first environment illite was degraded to smectites, and palygorskite
(and sepiolite) was probably formed by neoformation, or by transformation
from illite or smectite. In the open marine environment detrital illite, coming
from a source area which supposedly underwent an anchimetamorphic
process, practically preserved its high crystallinity, and increased its percentage,
whereas transformed or neoformed clay minerals decreased.
Introduction.
The_ Miocene-Pliocene boundary at
the Vera Basin, western Mediterranean
(Almeria, Spain), has been interpreted
differently by various authors
on the basis of stratigraphical
and paleontological investigations
(BIZON et al., 1974; MONTENANT et
al., 1976; GONZALEZ DONOSO &
SERRANO, 1977; CITA et al., 1978-
1980; CARRASCO et al., 1979; ·etc.).
CITA et al. (1978-1980) have recognized
in this basin characteristics of a
brackish, shallow-water environment
for sediments that underlie Early
Pliocene open-marine marls, and
overlie Late Tortonian to Messinian
marine turbidites, while BIZON et al.
(1974) and CARRASCO et al. (1979)
found no evidence of marine sedimentation
discontinuity during the
Miocene-Pliocene transition.
The present paper is a contribution
to the determination of paleoenviron-

T
260 E. Galtin, M. Gonztilez, L6pez, C. Ferntindez Nieto, I. Gonztilez Dlez
mental conditions of the Miocene-
Pliocene boundary in the western c
Mediterranean basin, by means of the
interpretation of the clay mineral
assemblages found in Neogene materials
of the Vera Basin.
Materials and methods
The sections studied are situated at
«Los Palacios» and

Clay Minerals,of Miocene-Pliocene Materials-at the Vera ... 261
to methods and data of SCHULTZ
(1964), BISCAYE (1965), MARTIN
The clay minerals identified in the

a) Section
Samples Q c D F H y A
108 10 34 8 9 39
107 8 39 7 tr 43
106 8 36 6 tr 49
105 5 47 6 42
104 7 39 6 9 tr 38
121 7 42 6 tr 42
120 9 40 6 5 tr 39
119 5 44 6 45
118 11 46 6 tr 35
117 11 52 5 32
116 5 44 6 5 40
115 9 so 8 tr 32
113 9 38 6 tr tr 42
112 8 36 tr tr tr 46
111 7 46 tr tr 44
97 11 44 8 tr . 34
96 8 42 7 tr tr 38
95 8 44 tr tr 44
94 8 48 tr tr 40
93 7 46 5 tr 41
92 9 so tr tr 36
91 11 54 6 tr 28
90 8 53 4 tr 34
Q = Quartz; C = Calcite; D = Dolomite; F =; Felspars; H = Halite; Y = Gypsum· A =
Phyllosilicates · :

a) «Canada de Vera» Section
TABLE 2
Mineralogical composition of < 2 11m fractions
Sample I Pr Sm Ch+K Pa Sp
80 68 17 15
79 63 tr 21 16
78 38 53 8
77b 34 42 7 17
77 49 40 tr 7
76c 40 tr 55 5
76b 40 tr 39 tr 16
76 37 6 51 6
75c 47 43 10
7Sb 36 59 6
75 45 tr 47 8
74c 48 46 6
74b 29 so tr 20
74 34 tr 36 tr 25 tr
73c 26 52 tr 20
73b 31 tr 52 tr 13
73 27 tr 49 tr 20 tr
72c 27 59 tr 11
72b 26 tr 52 tr 20
72 25 tr 51 tr 15 tr
71 61 8 17 14
70 21 59 tr 19
69 29 49 tr 16 tr
68 41 tr 16 9 34
67 40 tr 22 36
66 41 54 5
65 45 46 9
64c 23 tr 63 tr 10
64b 41 52 tr 5
64 23 tr 57 tr 13 tr
b) «Los Palacios» Section
"
Sample Pr Sm Ch+K Pa Sp
108 65 11 13 10
107 69 6 13 12
106 52 5 41 7
105 62 5 28 10
104 51 5 40 9
121 48 6 40 6
120 62 tr 30 5
119 38 tr 57 5
118 43 tr 52 tr
117 60 tr 34 7
116 58 tr 35 7-·
115 so tr 41 5
113 -29 tr 56 tr 9
112 45 5 30 7 14
111 30 5 52 tr 13
97 34 45 tr 18
96 23 tr Si tr 20 tr
95 30 39 7 24
94 43 57
93 36 62 tr
92 28 tr 54 13 5
91 ' 39 42 19
90 22 78 tr
I= Illite; Pr = Paragonite; Sm = Smectites; Ch = Chlorite; K = Kaolinite; Pa= Palygorskite;
Sp = Sepiolite · '

264 E. Galan, M. Gonzalez, L6pez, C. Femandez Nieto, I. Gonzalez D!ez
sal
"' 79~
ffi 78
~ 77 b
.: 76c 77 ±::=..
76b76 ..____
?Se
E._
" "'~E_
~ .. ~
i: 67r--
66r---
65;--
64c L--
64b
64i----
~~-~---,
E= ER §;__
~ r:- ~ ~
~ ~ ~ ~
w~
t= =
==- F t ~
4 mm 7 9 11 13 a.1 a.2 a.3 a.4 a.s 125 175 22s 2is 325 A a.s a.s a.? a.8
( 1) (2) (3) (4) (5)
------~· -~--~Fig7~---Gaiiada-de-Vera. {1-) K:ublerlndex; (2) Height/half-height width of the peak at 10 A; (3) I 002 I
I 001 ratio for illite; (4) Crystal size of illite (on 001); (5) Biscaye Index.
r
!
' I
I
1a8
1a7
1a6
1a5
1a4
"' a;
g 121
12a
;;! 119
118
117
116
'
Approximate 115
113
boundary 112
111
~ r==. L----
I
I
'
~
E
E
~
~pproximate ~~ ~ 75 ~
bo~~;;y- ;j ~74 ~~~~
73 b 73 t::::------
72 c t::=:::-
"t=-
96
95 .
~
"'
"l
~
L
" 93
~I L_
92
L
m
j__
91 .
9a l=,
a 2 4 mm 7 9 11 13 a.1 a.2 a.3 a.'4 a:s 1 5 175 225 275 32s !\ at a.'s a.'7 a.8 '
(1) (2) (3) (4) (5)
J
Fig. 3 - Los Palacios.

Clay Minerals of Miocene-Pliocene Materials at the Vera ... 265
anchimetamorphic conditions (WE­
BER et al., 1976).
The intensity ratio of the 001 and
002 reflections is usually rather low
(

T !
266 E. Galtin, M. Gonzalez, L6pez, C. Fernandez Nieto, I. Gonzalez Diez
minerals found in these sections (clay
mineral suites, and crystal chemicaL
data of the principal clay minerals)
suggests a change of sedimentary environmental
conditions which occurred
during the Miocene-Pliocene<
bound;:try at the Vera Basin. At the
beginning sedimentation occurred in
.. _a_bracldslLemdronment,lacustrine.or
perimarine, and later these condi~
tions were slowly changed to open
marine ones. This change pra:ctically
coincides with the Miocene-Pliocene
transition at the Vera Basin.
REFERENCES
' BARAHONA FERNANDEZ E., 1974. Arcillas de ladrilleria de la provincia de Granada: Evaluaci6n de
algunos ensayos de materias primas. Ph. D. Thesis n. 49, University of Granada, 398 pp.
·BISCAYE P.E., 1965. Mineralogy and sedimentation of recent deep-sea clays in the Atlantic Ocean and
adjacent seas and oceans. Geol. Soc. Am. Bull. 76, 803-832.
BIZON G., BIZON J.J., MONTENANT C., RENEVILLE P., 1974. Exemple de continuite marine Mio-Pliocene
en Mediterranee occidentale: le bassin de Vera (Cordilleres Betiques. Espagne meridionale). Compt.
Rend. Congr. C: I.E.S.M. Monaco, 5 pp. · V
--------·-·--··--GARRASGQ f., GONZALEZ-DONOSO _J .M.,-LINARES D., RODRIGUEZ !'., SERRANO F., 1979. C ontribuci6n al
conocimiento dellimite Mioceno-Plioceno en el dominio del Mediterraneo accidental: las secciones
de Los Palacios y Canada de Vera. (Almeria, Espafia). Estudios geol. 35, 559-567.
CITA M.B., VISMARA ScHILLING A., BossiO A., 1978-1980. Stratigraphy and paleoenvironmental of the
Cuevas de Almanzora section (Vera Basin, Spain). A re-interpretation. Abstracts Messinian Seminar
4 (Roma) and Riv. Ita!. Paleont. 86, n. 1, 215-240.
CULLITY B.D., 1964. Elements ofX-ray diffraction. Addison-Wesley Pub. Co., London, 514 pp.
GALAN E., CASTILLO A., 1984. Sepio[ite-Pa[ygorskite in Spanish Tertiary basins: genetical patterns in
continental environments. Pp. 87-124, in: Palygorskite-Sepiolite. Occurrences, Genesis and
Uses, (A. Singer and E. Galan, editors), Developments in Sedimento\ogy 37, Elsevier.
GONZALEZ DoNoso J.M., SERRANO F., 1977. Precisiones sabre la bioestratigrafia del carte de Cuevas de
Almanzora. Cuad. Geol. Univ. Granada 8, 241-251.
GREENE-KELLY R., 1953. Identification ofmontmorillonoids. J. Soil Sci. 4, 233-237.
HUERTAS F., 1969. Minerales fibrosos de la arcilla. Su genetica en cuencas sedimentarias espafiolas y
sus aplicaciones tecnol6gicas. Ph. D. Thesis, University of Madrid, 284 pp.
KUBLER B., 1968. Evaluation quantitativedu metamorphisme par la cristallinite de l'illite. Bull. Cent.
Rech. Pau., S.N.P.A. 2/2, 258-307:
MARTIN PoZAs J.M., 1968. El antilisis mineral6gico cuantitativo de Ios filosilicatos de la arcilla por
difracci6n de rayos-X. Ph. D. Thesis, University of Granada, 244 p. ·
MONTENANT D., BIZON G., BIZON J.J., 1976. Continuite ou discontinuite de sedimentation marine
Mio-Pliocene en Mediterranee occidentale. L'exemple du Bassin de Vera (Espagne Meridionale).
Rev. Inst. Fran. Petrole 31, (4), 613-663.
SCHULTZ L.G., 1964. Quantitative interpretation of mineralogical composition from X-ray and chemical
data for the Pierre Shale. Geol. Surv. Prof. Paper 391c, 31 pp. ·
SEBASTIAN PARDO E., RODRIGUEZ GALLEGO M., LOPEZ AGUAYO F., 1980. Mineralogia de Ios inateria/es
plioceno-pleistocenos de la Depresi6n de Guadix-Baza. Ill. Formaciones de Baza y Ser6n-Caniles.
,Consideraciones generales y conclusiones. Estudios geol. 36, 289-299.
WEAVER C.E., BECK K.C., 1977. Miocene of the S.E. United States. A model for chemical sedimentation
inperi-marine environment. Sedimentary Geology 17, 1-234. ·
WEBER F., DUNOYER DE SENGOZAC G., EcoNOMOU C., 1976. Une nouvelle expression de la cristallinite de
l'illite et des micas. Notion d'epaisseur apparente des cristallites. C.R. somm. Soc. Geol. Fr. 5,
225-227.

Miner. Petrogr. Acta
Vol. 29-A, pp. 267-276 (1985)
Clay Mineral Distribution in the Evaporitic
Miocene Sediments of the Tajo Basin, Spain
J.M. BRELL 1 , M. DOVAU, M. CARAMES 2
I Departamento de Estratigrafia y Geologia Hist6rica, Facultad de Geologia, Universidad Complutense, 28040
Madrid, Espafta ·
2 Departamento de Cristalografia y Mineralogia, Facultad de Geologi,;:', Universidad Complutense, 28040 Madrid,
Espafta
ABSTRACT- The ba~in of the Tajo river is a Tertiary tectonic depression filled
by detrital material in its borders, evaporitic formations in the central part
and sediments of intermediate nature in between. Lateral changes of facies
are frequent and sudden which introduce many problems when stratigniphic
correlations are sought.
This paper establishes for the northermost zone of the basin, five stratigraphic
units with important mineraldgical differences. The_ clay mineral
assemblages corresponding to each one of these units are the following:
- Massive gypsum unit: trioctahedral illite and smectite with minor
amounts of kaolinite and seldom chlorite;
- Tabular gypsum and clays unit: illite mainly dioctahedral, smectite and
as minor constituents kaolinite and mixed-layer minerals;
- Greenish clays unit: trioctahedral smectite as the major constituent with
illite and small amount~ of kaolinite and mixed-layer minerals;
- Limestone, marls and clays unit: the same composition as the above unit;
- Arkoses unit: dioctahedral illite and smectite, and kaolinite.
The general mineralogical sequence is formed by illite and minor amounts of
Mg-smectite in the lower part. The clays in the middle part are mainly
Mg-smectite while in the upper part they are Al-smectite and illite.
The mineralogical characterization of these units allows correlations in
several areas of the basin to be formulated, as well as providing indications
of the sedimentary environments during the deposition of all these materials.
Introduction
The Tajo basin is a Tertiary depression
located in the central part of
the. Iberian Peninsula, bordered by
three mountain ranges (Fig. 1). The
northern and southern borders are
formed by igneous and metamorphic
rocks, and the boundaries are defined
by several tectonic events of late
Hercynian age, reactivated during
the Tertiary. Reactivation happened
during a compressive stage and gave
dse to normal and· reverse faults
which locally overthrust the igneous
basement over Tertiary sediments.
The eastern border is constituted by
the Iberian Range which is made up
of sedimentary rocks of Mesozoic and
Paleozoic ages. Sedil;nentation in the
basin occurred mainly during the

T
268 J.M. Brell, M. Doval, M. Carames
Fig. 1 - Location map. 1: Tertiary; 2: Mesozoic; 3: metamorphic rocks; 4: igneous rocks.
Miocene with materials derived from the basin evolution. For these
erosion of the surrounding mountains.
However, in depth, Cretacic
and Paleogene sediments are found
outcropping locally with small thicknesses
at the northern part of. the
basin.
The. Miocene · sediments, show a
more or less concentric setting, forming
zones roughly symmetrical with
regard to the central part. Laterally,
a transition between detrital and e­
vaporitic facies can be observed, from
the borders to the center of the basin
and materials of intermediate features
occur between both facies
(RIBA, 1957; BENAYAS et al., 1960).
In the vertical direction this arrangement
becomes complicated due to
the large variations of weathering
energy and support directions during
reasons, some of the facies become
extensive over the others giving rise
to complex suites. Generally speaking,
three Miocene megasequences
can be established for the whole of
the basin (TORRES et al., 1984) separated
by barely visible unconformities,
whose temporal significance is
doubtfoul. General mineralogical features
of clays from this basin have
been described by ALONSO et al.
(1961), HUERTAS et al. (1970; 1971),
and compiled by GALAN et al. (1984).
The area studied is located in the
northern part of the basin at the west
of the Madrid meridian. Five lithostratigraphic
units were established
after the present study. These units
follow each other in the vertical as
well as in the horizontal sense. The

Clay Mineral Distribution in the Evdpori.tic Miocene ... 269
passing from one to another unit is
realized through facies changes; all
the units are easily recognizable in
the field and can be used as cartographicones.
Their correlation with
similar more easternly located
formations, lets one attribute them to
a Middle Miocene (Aragoniense) age
(ALBERDI et al., 1983). In Fig. 2 the
geographical location of each unit is
shown.
Mineralogy
Massive gypsum unit
It is the lower unit found in the
northern part of the Tajo basin. It is
formed of thick layers of macrocrystalline
gypsum con tammg thin
clayey levels. Its bottom canr'iot be
observed and the thickness reaches
40 m. Gypsum layers show varying
colours due to the presence of notahle ·
impurities, mainly of clay minerals,
quartz, and micritic magnesite. The
assemblage has been affected by
strong recrystallization processes
masking its original texture. Towards
the basin center, layers ofanhydrite,
halite, and in some cases glauberite,
epsomite or thenardite are interbedded
between gypsum. Locally, these
salts are exploited (GARCIA DEL
CURA, 1979).
The clayey interbeddings are constituted
by phyllosilicates (80%),
quartz (10%) and feldspar minerals.
The main phyllosilicates ·are illite
mainly trioctahedral (70-100%),
trioctahedral smectites (20%) and
kaolinite (5%). Occasionally, minor
quantities of chlorite appear. Except
for illite, the phyllosilicates show a
very low crystallinity. Variations of
mineralogy along this sequence are
rare. Nevertheless, the illite ratio increases
towards the top at the expense
of the smectite content.
Fig. 2- Stratigraphic relationships of the Miocene units. 1: Massive gypsum; 2: Tabular gypsum
and clays; 3: Greenish clays; 4: Limestone, marls and clays; 5: Arkoses.

270 J.M. Brell, M. Doval, M. Carames
Tabular gypsum and clays unit
There is a continuous transition upwards
from the previous unit to a new
one constituted by an alternation
of tabular gypsum and clays whose
thiCkness reaches 40 m. In some
places of the basin an apparent unconformity
can be observed between
both units, although it cannot be
established for the whole area. Gypsum
appears as levels of varying
thickness ranging from a few centimeters
to about 2 m 'and shows nodular,
fibrous, tabular, selenitic, ... textures.
Alte-rnating with gypsum, there
are grayish clay layers with parallel
lamination and bearing vegetable deb-
- ··----- -----rrs.-There-are a1so several intercalations
of dolomicrite and magnesite.
The clay interbeddings are mainly
composed of phyllosilicates and
minor amounts of quartz and feldspar.
The ratios of different phyllosilicates
are rather varying. However,
it can be said that illite is the major .
constituent in the lower part (50-
70%) while in the uppermost part
smectite becomes more abundant
than illite. Minor constituents are
kaolinite and mixed-layer minerals,
chiefly illite-smectite and chloritesmectite.
Illite is mainly dioctahedral '
and shows low cristallinity and smectite,
also poorly crystallized is of the
trioctahedral type.
Greenish clays unit
This unit is made up of nearly 40 m
of green clays with some intercalations
of micaceous sands in its lower
... middle __ part,~ and~c:arbonates in the
upper one. In some cases they appear
as massive clays very rich in organic
matter, sometimes containing
nodules of barite and showing abundant
bioturbation marks. In other
cases they show a well developed paF
allel lamination. Sandy levels, composed
of biotite and chlorite, show
crossed or parallel laminations forming
fining-upward sequences with
bioturbation at the top. Carbonatic
rocks are mainly white marls or
dolostones and form fairly continuous
levels.
The clay mineralogy involves a
considerable abundance of phyllosilicates
with minor amounts of quartz
and feldspars. Dioctahedral and
trioctahedral illite together with
trioctahedral smectite are the main
clay minerals. The smectite content
reaches 90% in some samples, and
never is lower than 50% of the whole·
sample. Small amounts of kaolin:ite
and mixed-layer minerals are present.
A very significant feature of this
unit is the presence of some pinkish
clay levels which are very porous and
composed only of chlorite-smectite
mixed-layers (DOVAL et al., 1985).
In the northern part greenish clays
are covered by the arkosic leveJs of
the upper unit in a contact which is
frequently erosive. In the central part
(Cerro de los Angeles) its top is constituted
by siliceous rocks. Towards the
south and east, there is a gradual
transition from clays to carbonatic
materials. Carbonates are more developed
in the south. There they

Clay Mineral Distribution in the Evaporitic Miocene ... 271
spread towards the basin center,
where they lie directly over the gypsum
units.
Limestones, marls and clays unit
It is made ~p of nearly 35 m of
white carbonatic rocks with interlayers
of grey and green clays and
partly constitutes a facies change
from the clayey levels of the preceding
unit.
The carbonates show a . finemedium
bedding in the lower part of
the unit, In the upper part, they are
coarse-bedded and show a rather
massive aspect. At the top they occur
partly silicified and often contain
lens-shaped chert levels whose thickness
and continuity increase upwards
becoming a continuous bed. The carbonates
are constituted by mi~ritic
dolostones, or limestones. . In some " of
the beds, lens-shaped calcite pseudomorphs
can be observed as well as
bioturbation marks.
The clay interbedding is mainly
composed of trioctahedral smectite
(50-90%) with dioctahedral and trioctahedral
illite (up to 30%) and minor
amounts of kaolinite. Towards the
top of the unit there are some sepiolitic
and palygorskitic levels, fairly
related to the siliceous rocks: Their
thickness is quite variable and they
are exploited in some places as in
Cerro Batallones.
Arkoses· unit
This unit constitutes the detrital
. bordering facies of the Central System
characterized by its arkosic composition.
It is the same as the so
called

1
272 J.M. Brell, M. Doval, M. Carames
be found in these distal zones, representing
the transition to the Greenish
clays unit.
Sepiolitic layers are found at the
top of many sequences, often associ-.
ated with siliceous or carbonatic
rocks. Their extent and thickness
vary and in some cases are partly
eroded. The main features of these
sepiolite deposits have been pointed
out by GALAN (1979; 1984). In these
suites, although stratigraphically
lower, there are zeolitic levels,
formed manily of calcium zeolites
(mordenite, heulandite). Is is evident
that the mineralogy of these zones of
the basin is very complex and the reiationships--b-etween
the different authigenic
minerals have not yet been
established. In Fig. 3, the most representative
X-ray traces of the different
mineralogical assemblage are shown.
Discussion
The Tajo basin has been always rec
garded as an endorheic basin filled by
an active sedimentation process
occurring under semiarid climatic
62 60 29 25 21
17 13 2El
1.49 1.51 1.54 3.34 4.45 4.97
7.13 10.04 14.7
Fig. 3 A - X-ray diffraction patterns of unoriented representative clay fractions ( < 2 ~m) from the
different units. 1,2,3,4,5 as in Fig. 2.
0
A

20
Clay Mineral Distribution in the Evaporitic Miocene ... 273
16 12 8 4 28
4.97 7.13 1o.o4 14.7 17.6 $.
conditions. This view is supported by
the considerable development of e-
58 vaporitic materials as well as the immaturity
features of the bordering
arkosic facies.
The general log for the area studied
(Fig. 4) indicates that with the pas-
48 sage of time, a transition to a damper
climate occurred even though the
general classification as semiarid
conditions still is valid. The decrease
of evaporites in going up the se­
. quence, together with a simultaneous
increase of detritic materials, as well
as the presence of levels with abundant
organic matter and bioturbation
marks along with the spreading
38
out of arkoses towards the center of
the basin confirm this transition.
The arkose levels show a mineralogical
composition fairly similar to
that of the surrounding granitic rocks
of the Central System. It can be supposed
that dioctahedral smectites
proceed from muscovite or feldspar
minerals. The increase of smectite in
the more distal zones can be interpreted
as due to its smaller particle
size. A clear influence of igneous
rocks on the sedimentation is maintained
by the distal arkosic materials.
In these levels, there are often
interbeddings ~f high magnesium
minerals such as sepiolite, together
with· chert and carbonates, whose
chemical compositions seem very
.different from those of arkoses or
Fig. 3 B - X-ray diffraction patterns of oriented
representative clay fractions(< 2 IJ.ID) from the
different units. A: air dried; B: treated with eth-
ylene glycol. 1,2,3,4,5 as in Fig. 2.
granitic rocks, as shown by APAR­
ICIO et al. (1975) and LOPEZ RUIZ et
al. (1975). From this place and basinwards
all the units present a high
percentage in Mg-rich phyllosilicates

274
J.M. Brell, M. Doval, M. Carames
0 50 100
LITHOLOGY
ll
--'
I·.·.·.· .j
Biotitic sands
ll
-Clays
I
!I====~#H~~ttti~
~---
E~~~};~
Limestones/Marls
Tabular gypsum
e·lll•
..........
;
I
I
I
I·
I
lliilll.
~~

Clay Mineral Distribution in the Ew:iporitic Miocene ... 275
TABLE 1
Chemical analyses of smectite-rich clay fractions
2 3 4 5 6 7 8 9 10
SiOz 54.20 55.30 54.20 50.30 53.10 51.90 52.80 49.80 50.00 50.30
Alz03 3.80 2.70 2.50 5.50 3.80 2.40 21.70 26.60 18.90 5.80
Fez03 0.45 0.52 0.90 2.10 1.40 1.80 6.65 4.90 5.10 2.35
FeO 0.40 0.38 0.15 0.74 0.65 0.20 0.74 0.65 0.25 0.70
CaO 0.19 0.21 0.69 0.27 0.87 1.20 2.20 1.85 1.70 0.90
M gO 25.70 27.30 27.60 26.40 27.30 26.80 2.90 3.10 3.70 25.25
Na 2 0 0.21 0.24 0.16 0.17 0.32 0.61 0.85 0.70 0.64 0.47
K20 0.49 0.53 0.24 1.10 0.63 0.27 1.90 1.24 1.35 0.22
HzO ± 14.70 12.83 13.90 13.32 11.65 14.70 9.90 11.15 19.15 14.00
1,2: Tabular gypsum and clays unit; 3,4,5: Greenish clays unit; 6: Limestone, marls and clays
unit; 7,8,9,10: Arkoses unit
(Table 1). These assemblages must
represent a very different geochemical
environment, probably due to a
very diff~rent source area. High-Mg
minerals seem in many cases to have
a neoformation oiigin as observed in
the Cerro Batallones where fi,brous
clay minerals are found associat~d
with thick siliceous levels.
Trioctahedral smectites show a
more doubtful genesis, as sometimes
they are associated to detrital facies
but in other cases, they form more or
less continuous pure levels: In any
case, chemical analyses indicate a
very different composition of these
minerals from that of arkosic facies
(Table 1). The provenance of these
minerals must be searched for at the
westernmost zones of the basin. In
the area studied, it can be seen that
the green clays became progressively
sandy westwards (VEGAS, 1975)
changing around Pinto and Valdemoro
to biotite-chlorite sands, which
disappear under the arkosic facies
near the locality of Parla.
The occurrence in the green clays
of interbedding of pinkish levels basically
formed by a chlorite-smectite
mixed-layer mineral might indicate
that at least in part, smectite is a result
of chlorite transformation.
The question of the genesis of the
siliceous levels also arises. Sediments
from all the units indicate a very low
alteration of the source area, since
they contain considerable amounts of
feldspars, biotite and chlorite.
Edaphic alterations can only be
found in some of the arkosic levels,
and they always are limited in extent.
In the Central System traces of
noticeable alteration processes are
not seen. It is difficult under these
circumstances to think that the silica
originates from the alteration of
igneous minerals.
All these features allow the Tajo to
be considered as an evaporitic basin
with a very complex evqlution, showing
some peculiar characteristics
which make it very different from
others described in geological papers
all over the world. ·

276 J.M. Brell, M. Doval, M. Carames
r' I
~
I
!,
REFERENCES
ALBERDI M.T., HOYOS M., JuNCO F., LOPEZ MARTINEZ N., MORALES J.,- SESE C., SORIA M.D., 1983.
Biostratigraphie et evolution se:dimentaire du Neogene continental de l'aire de Madrid. Pp. 1.5-18,
in: «Mediterranean Neogene continental paleoenvironments and paleoclimatic evolution».
Interim-Colloquium, RCMNS, Montpellier. .
ALONSO J., GARCIA VICENTE J., RIBA 0., 1961. Sedimentosfinos del centra de la cubeta terciaria del Tajo.
Pp. 21-55, in: Proc. 2nd Reuni6n Gr. Espaiiol Sedimentologia, C.S.I.C., Madrid.
APARICIO A., BARRERA J., CARBALLO J.M., PEINADO M., T!NAO J.M., 1975. Los materiales graniticos
hercinicos del Sistema Central Espafzol. Mem. Inst. Geol. Min. de Espaii.a 86, 145 p.
BENAYAS J., PEREZ MATEOS J., RIBA 0., 1960. Asociaci6n de minerales detriticos en la Cuenca del Tajo.
Anal. Edaf. Agrobiol. 19, 635-670.
DoVAL M., RODAS M., RUIZ AMIL A., ARAGON F., 1985. !nterstratified Minerals in Spanish Sedimentary
F acies: Lower Part of the Keuper in the Siguenza Area and the Tajo Basin, Central Spain. Abstract,
These Proceedings. · .
GALAN E., 1979. The fibrous clay minerals in Spain. Pp. 239-249, in: Proc. 8'h Conf. Clay Min. and
Petrol., Teplice.
GALAN E., CASTILLO A., 1984. Sepiolite-Palygorskite in Spanish Tertiary basins: Genetical patterns in.
continental environments. Pp. 87-124, in: Palygorskite-Sepiolite. Occurrences, Genesis and Uses
(A. Singer and E. Gal

Miner. Petrogr. Acta
Vol. 29-A, pp. 277-286 (1985)
Fluvial Pelitic Supplies from the Apennines to the
Adriatic Sea. I- The Rivers of the Abruzzo Region
L. TOMADIN 1 , P. GALLIGNANF, V. LANDUZZF, F. OLIVERP
' Istituto di Mineralogia e Petrografia, Facolta di Scienze, Universita di Urbino, Via M. Oddi 14, 61029 Urbino,
Italia
2 Istituto di Geologia Marina, CNR, Via Zamboni 65, 40127 Bologna, Italia
ABSTRACT- The tributary rivers of the coastal belt between S. Benedetto del
Tronto and Punta Penna (Abruzzo Region, central Italy) were investigated in
order to characterize the composition and the sedimentological behaviour of
the suspended load. Three fluvial mineralogical facies emphasize a regional
differentiation of the sediments from north to south, and a different provenance
of illite and smectite, the most abundant day minerals. High amounts
of illite are carried by the Tronto River, whereas a high smectite content is
present in the suspended load of the Sangto River. The final composition of
the fluvial supplies entering the sea shows an which depends
on the .clay minerals inherited from the drained formations, or on their
enrichment due to the river hydrodynamics.
Introduction
A large part of the modern sediments
of the Adriatic Basin is made
of detrital pelitic materials, distrib.­
uted in belts parallel to the axis of
the basin (BRAMBATI et al., 1983).
The extensive literature on the pelitic
sediments emphasizes the main
supply from the Po River (NELSON,
1972; PIGORINI, 1968; TOMADIN,
1981; VENIALE et al., 1973; 1977).
Little is known instead on the minor
supplies debouching into the Adriatic
(BRONDI et al., 1982; QUAKER-
NAAT, 1968; TOMADIN, 1969).
Among these, particular attention
must be given to the Apenninic supplies,
which, even if of reduced
volume in comparison with those of
the Po River, play an important role
in shallow-water sedimentation close
to the Italian coast. In fact, the present
investigation on the pelitic supplies
of the ·rivers debouching between
S. Benedetto del Tronto and
Punta Penna (Abruzzo Region, centr-al
Italy) (Fig. 1) was begun in connection
with a research program on
the continental shelf near the Middle
Adriatic Depression.
Contribution n. 557 of the Istituto per la Geologia Marina - CNR, Bologna (Italy).

278 L. Tomadin, P. Gallignani, V. Landuzzi, F. Oliveri
S.Benedetto
5
[J
L' Aquifa
14
.._.
C Chieti
18
17
Avezzano
[J
Sulmona
[J
19
21
0 10 30 50 km
ci'Abruzzo • Samples of fluvial muds
Fig. 1 - Sample location along the rivers of the Abruzzo Region.
Field and laboratory methods
The research was performed on the
fine-grained deposits left in the river
channel after the streamflow of a
flood episode had receded. Samples
were collected 24-48 hours after a
seasonal flood in July 1982. The sediments,
a few millimeters thick, consist
of mud and correspond, according
to MONACO (1971) and POTTER
et al. (197 5), to the finest particles

Fluvial Pelitic Supplies from thelfp(mnines ... 279
transported by the rivers as suspension
loads. Two situations were frequently
recognized during sampling:
a fine mud layer deposited on sand
beds (A) or directly on gravel b~1.rs (B)
(Fig. 2).
For a correct recognition of the
drained materials, the sampling was
referred to the whole watercourse.
The number of sampling sites along
the rivers (Fig. 1) depended on the
geology and the erodibility of the
drainage basins. In fact, the grainsize
distribution of the alluvium
changes unsteadily landward depending
on the occurrence of argillaceous
to marly to calcareous formations
(Fig. 3). Consequently, we found
that headward of definite points, all
the alluvium is formed of calcareous
gravels without the former mud cover.
The analytical procedures follow
the routine already described previously
(TOMADIN, 1969). The mud
samples were analyzed by X-ray diffraction:
a) on oriented slides to determine
the clay minerals of the

280 L. Tomadin, P. Gallignani, V. Landuzzi, F. Oliveri
~1
ill2
I

Across the upper «Laga Formation>>
(sample 3) the clays are completely
composed of illite (>90%) and chlorite.
When the river flows through the
Plio-Pleistocenic terrains before debauching
to the sea, the composition
of the sediments becomes indeed
illite-chlorite, with lower quantities
of smectite and kaolinite.
The most important characteristic
of the Tronto River clays is thus a remarkable
abundance of illite (60-
90%). Among the non-clay minerals,
carbonates are scattered along the
whole watercourse. Feldspars instead
decrease from the Miocenic to the
Pliocenic terrains (from sample 3 to
sample 2).
The Vomano River flows from the
Gran Sasso Massif and collects waters
from its northern slope (Fig. I} It
crosses the same geologic formation~
of the Tronto River in a ,narrow belt
(Fig. 3). The typical clay mineral
assemblage of these fluvial sediments
is illi te-smecti te with minor amounts
of chlorite and kaolinite. In the
Vomano drainage basin the transition
.from the «Laga Formation» to
the clays of the Pliocene is also detectable
by clay mineralogy. Carbonates
and quartz are regularly distributed
along the watercourse. A considerable
increase of dolomite below
the confluence of the Tavone stream
(samples 10 and 9) (Fig. 1) is due to
supplies from the Gran Sasso Massif.
The Sangro River drains very different
terrains (Fig. 3). From the river
head to s~mple 23, it crosses Miocenic
marly sandstones and clayey
marls interstratified with Jurassic
Fluvial Pelitic Supplies from the Apem1Xn~s ... 281
dolomitic limestones of the Montagna
Grande and of the Monti della Meta.
The clay sediments of the upper Sangro
course are characterized by the
illite-smectite assemblage, with
minor amounts of kaolinite and chlorite
in decreasing order. The same
composition of the sediments is also
found through the Flysch terrains of
the Oligo-Miocene (Samples 22, 21,
20). A sharp compositional change
occurs when the Sangro River meets
the «argille scagliose» and/or «argille
varicolori>> (samples 19, 18), when
the typical assemblage is given by
predominant smectite-kaolinite and
lower illite and chlorite percentages.
In the lower Sangro course, across
the clays of the Lower-Middle
Pliocene (sample 17) and sands and
clays of the Pleistocene (samples 16,
15), the composition of the fluvial
clays becomes: smectite-illitekaolinite
with minor amounts of
chlorite. The differentiation of the
sedim~nts observed along the whole
Sangro course is marked by the nonclay
minerals of the coarser fractions.
While calcite is always present in
high amounts, dolomite is abundant
only in the Miocenic formations
(samples 23, 22, 21, 20). Dolomite is
completely absent downstream in the
river segment through the Aventino­
. Sangro «argille varicolori» (samples
19, 18), and then reappears in small
amounts in the terminal sediments of
the Sangro River. Quartz is generally
present in high percentages and
shows the highest amounts in samples
21, 20, 19, 18. This probably originated
from flint particles in nodu-

T
282 L. Tomadin, P. Gallign(mi, V. Landuzzi, F. Oliveri
lar cherts of the limestones of the
Molise and Umbria facies.
The sediments of Tordino, Tavo­
Saline and Pescara Rivers (Fig. 1)
show a mineral composition similar
to that of the Vomano River sediments.
On the contrary, the sediments
of the Sinello River are comparable
to the materials recognized in
the lower course of the Sangro River.
Discussion
The analysis of the flood-deposited
pelitic sediments evidences a succession
of different mineralogical
assemblages distributed~ along the
watercourse, directly linked to the
lithofacies of the geological formations
drained by the rivers. Such

-
Fluvial Pelitic Supplies from the Apennines~. 283
characterized by increasing smectite
. and decreasing illite contents. Comparable
amounts of chlorite and
kaolinite are a peculiar aspect.
c - The Sangro River facies ex~
hibits the highest smectite and the
lowest illite percentages. The
kaolinite/chlorite ratio is on the average
>1.
The variation of the clay mineral
percentages in the three facies is
given in Fig. 4.
The identification of horizontal
zoning along the watercourses, and
the recognition of mineralogical
facies which differ from north to
south, allow some regional remarks,
significant from the sedimentological
point of view. Thus the provenance of
the clay minerals supplied to the
Adriatic Sea: can be related to the
geology. In fact, considerable
amounts of illite from the «Laga
Format!on» are transported to. the
sea by the Tronto and Vomano Rivers.
Smectite-rich supplies from the
flysch deposits and from the

0
284 L. Tornadin, P. Gallignani, V. Landuzzi, F. Oliveri
affect the pelitic sediments, we can
consider the trend of smectite concentrations
downstream versus sampling
distance from the river mouths
(Fig. SA). It is easy to nC>tice that
smectite increases seawards.
Similar results have been already
observed both on minor watercourses
(MONACO, 1971) and throughout the
whole Mississippi basin (POTTER et
al., 1975). They depend on the higher
amount of transport by suspension of
smectite particles, characterized
(GRIM, 1968) by very small grainsize
if compared with other clay
minerals. The suspended load increases
seaward with the water
volume of the river, and the amount
---~--~ofsmectite-inthe load increases likewise.
Such an increase is. evident
along the Sangro River and the
Vomano River, whereas there .is an
opposite trend along the Tronto River.
For the comprehension of the phenomenon
it is necessary to remember
that the former rivers carry a
smectite-rich load and the latter
shows on the contrary a very high
ilfli:e content~" Moreover, since the
two most abundant clay minerals
(illite and smectite) amount to about
80% of the total, the «closing balance»
of the percent data comes into ·
effect. Therefore the illite concentrations
show an opposite trend in respect
to the smectite conc.entrations
along the watercourses (Fig. 6A).
In order to analyze the behaviour
of the crystallinity of smectites (v/p
ratio) and of illites (na. value) along
the rivercourses, other diagrams
have been considered. The general
trend of the v/p ratio shows smectites
characterized by medium to good
crystallinity, and referable to the
three mineralogical facies (Fig. SB).
The na. values show large fluctuations
in the fluvial sediments between
moderate to poorly organized illites
(Fig. 6B). The trends observed are
controlled by the chemistry of waters
an~ solutes (as natural ions, pollut-
80 A
Sm
0.2
~Landward
Seawar_d _
o+-~---.--,---r--.--.---~Km~f~r~om~s~ea
90 60
Fig. 5 -Trends of smectite amounts (A) and of smectite crystallinity (v/p ratio) (B) downstream of
the three main regional rivers.

Fluvial Pelitic Supplies from the Apenriines ...
285
9.6
30
10
- Landward
·-·"
17 16
I .
19 ___.18 15
Seaward- 1.0 - Landward Seaward ...:._
o+---.--,---.--~--~--.--.~Km~·~frrom~, ~se~a
90 60 30
Fig. 6- Trends of illite amounts (A) and of illite crystallinity (na value) (B) downstream of the three
main regional rivers.
ants, etc.), but at present they are
not comparable because of the, absence
of similar data in the literature.
. "
More extensive investigations should
permit better knowledge of the behaviour
of clay minerals transported
by river streams to be obtained.
In the end section of a rivercourse,
the suspended load acquires a fina1
composition, which remains, according
to the Authors, constant at least
for a single season. In the rivers of the
Abruzzo Region, the final composition
of the suspended load exhibits a
peculiar «imprinting» that may be
inherited from the clay minerals of
the drained formation (as for example,
the illite content of the Tronto
River sediments), or may depend on a
progressive clay mineral enrichment
toward the mouth of the rivers (as for
example, the smectite along the Sangro
River course).
Conclusions
The clay mineralogy of finegrained
sediments collected along
the main rivers of the Abruzzo Region,
characterizes the fluvial supplies
to the Adriatic Sea. Based on the
analytical data and sedimentological
remarks the following conclusions
can ne drawn:
1-- The sediments deposited from
suspension loads after the streamflow
of a flood receeds, show a succession
of different mineralogical
assemblages along the watercourse.
\ 2 -- This horizon tal zoning depends
on the li thofacies of the
drained formations and from the extension
of the corresponding belts
eroded by the rivers.
3 -- As a matter of fact, three
mineralogical facies recognizable in

286 L. Tomadin, P. Gallignani, V. Landuzzi, F. Oliveri
the fluvial sediments of the Region,
emphasize a gradual differentiation
of the composition of the sediinents ··
from north to south, and a variable
provenance of the most abundant
clay minerals (illite and smectite)
carried by the rivers to the Adriatic.
4 - The final composition of the
suspended load before entering the
sea~ ~shows an.-· «imprinting» due to
the clay minerals inherited along the
rivercourse, or to their enrichment.
seaward depending on the hydrodynamics.
REFERENCES
BELVISO R., CHERUBINI C., COTECCHIA V., DEL PRETE M., FEDERICO A., 1977. Dati di compos'izione
mineralogica delle argille varicolori affioranti nell'Italia meridionale tra i fiumi Sangro e Sinni.
Atti 2° Congr. Naz. sulle Argille 1976, Bari, Geol. Appl. Idrogeol. 12, parte II, 123-142.
BISCAYE P .E., 1964. Distinction between chlorite and kaolinite in recent sediments by X-ray diffraction.
Am. Miner. 49, 1281-1289.
BISCAYE P.E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and
adjacent seas and oceans. Geol. Soc. Am. Bull. 76, 803-832.
BRAMBATI A., CIABATTI M., FANZUTTI G.P., MARABINI F., MAROCCO R., 1983. A new sedimentological
- ·-textural-map·oftheNorthern··and--CentralAdriatic Sea. Boil: Oceanol. Teorica e Applicata 14,
267-271.
BRONDI A., ANSELMI B., FERRETTI 0., 1982. Studi sui parametri geologici rilevanti al fine della determinazione
della contaminazione ambientale del territorio nazionale. Rapporti fra litologia delle terre
emerse e composizione mineralogica della frazione argillosa dei sedimenti fluviali dei piu importanti
fiumi italiani (II Parte). Rend. Soc. It. Min. Petr. 38 (3), 1299-1313.
GRIM R.E., 1968. Clay Mineralogy. McGraw-Hill, New York.
MONACO A., 1971. Etude mineralogique des argiles fluviatiles du Roussillon. Bull. B.R.G .M. IV I, 33-45.
NELSON B.W., 1972. Mineralogical differentiation of sediments dispersed from the Po Delta. Pp. 441-
453, in: The Mediterranean Sea, a natural sedimentation laboratory (D.J. Stanley, editor),
Dowden, Hutchinson & Ross, Stroudsbourg.
PIGORiiu B., 1968. Sources and dispersion of recent sediments of the Adriatic Sea. Marine Geology 6,
187-229.
POTTER P.E., HELING D., SHIMP N.F., VAN WIE W., 1975. Clay mineralogy of modern alluvial muds of
the Mississippi River Basin. Bull. Centre Rech. Pau- SNPA, 9 2, 353-389.
Pozzuou A., MATTIAS P., GALAN-HUERTOS E., 1973. Mineralogia di sedimenti abruzzesi. I. -Relazione
fra depositi argillosi miocenici e quaternari. Per. Min. 41, 3, 611-655.
QuAKERNAATiJ., 1968. X-ray analyses of clay minerals in some recent fluviatile sediments along the
coasts of central Italy. Ph. D. Thesis, University of Amsterdam.
ToMADIN L., 1969. Ricerche sui sedimenti argillosi fluviali dal Brenta al Reno. Giorn. Geol. 36, 159-
184.
TOMADIN L., 1981. Provenance and dispersal of clay minerals in recent sediments of the Central
Mediterranean Sea. Pp. 311-324, in: Sedimentary basins of Mediterranean margins (P.C. Wezel,
editor), CNR, Italian Project of Oceanography, Tecnoprint, Bologna.
VENIALE F., SOGGETTI F., PIGORINI B., DAL NEGRO A., ADAMI A., 1973. Clay mineralogy of bottom
sediments in the Adriatic Sea. Pp. 249-258, in: Proc. Int. Clay Con£. 1972, Madrid (J.M. Serratasa,
editor), C.S.I.C.
VENIALE F., SOGGETTI F., SANTAGOSTINO C., 1977. La distribuzione dei minerali argillosi nei sedimenti di
fondo del Mare Adriatico. II- «Mesofossa» e «Fossa» centro-meridionali. Atti 2o Congr. Naz.
sulle Argille 1976, Bari, Geol. Appl. Idrogeol. 12, parte II, 287-298.

Miner. Petrogr. Acta
Vol. 29-A, pp. 287-301 (1985)
Polygenesis of Sepiolite and Palygorskite in a
Fluvio-Lacustrine Environment in the
Neogene Basin of Madrid
S. LEGUEY, M. POZO, J.A. MEDINA
Departamento de Geologfa y Geoqufmica, Facultad de Ciencias, Universidad Aut6noma de Madrid, 28049 Madrid,
Espaiia
ABSTRACT- The genesis of sepiolite and palygorskite bearing beds located in
the south of Madrid (Spain) were studied. Three stages of formation are
differentiated as a function of the climatic and tectosedimentary evolution:
Genesis in paleosoils
- Sepiolite genesis in vertisols from Mg-smectite that releases silica;
- Palygorskite genesis in calcretes. ·
Diagenetic genesis of sepiolite and/or palygorskite at the bottom and the top
of silcrete beds. ·
Lacustrine genesis of sepiolite or palygorskite.
The sizes of sepiolite and palygorskite aggregates are less than 1 ~m in
lacustrine environment whereas their sizes are 1-5 ~m in paleosoils. In diagenesis,
sizes of 2-6 ~m are found for palygorskite and sepiolite aggregates
reach 10-50 j.lm. '
Introduction
The Neogene basin of Madrid contains
sepiolite and palygorskite deposits.
Various quarries are present
where deposits are particularly abundant
(GALAN, 1979). Numerous authors
have studied the regional geology
of the Madrid 'Basin. Among the
latest studies mention should be
made of the works by ALIA & CA­
POTE (1971), LOPEZ VERA (1975),
.MARTIN ESCORZA (1976),
VAUDOUR (1977), MEGIAS (1980)
and MEGIAS et al. (1983). All these
authors agree that there exist three
principal facies in the basin: one
containing salts, a transitional
carbonatic-clayey one and an arkosiC
facies.
Sepiolite and palygorskite deposits
are found in the transitional facies,
between a bed of greenish clay materials,
rich in magnesium, and arkosic
materials of varying grain size at the
top. The mineralogical composition
of these materials_ has been studied
by BENAYAS' et al. (1960), ALONSO
et al. (1961), HUERTAS et al. (1971),
PEREZ MATEOS & VAUDOUR
(1972), BUSTILLO (1976; 1982),
ORDONEZ & GARCIA DEL CURA
(1983) and LEGUEY et al. (1984a).
The genesis of the sepiolite and
palygorskite deposits has been inter-

288 S. Leguey, M. Pozo, J.A. Medina
preted in several different ways, depending
on discrepancies in the
strategic position of the arkosic materials.
GALAN (1979) and GALAN &
CASTILLO (1984), assuming a refilled
model of the Neogene basin with
lateral changes of facies, distinguish
two types of deposits. The former of
these, the Vallecas-Vicalvaro deposits,
are found in distal zones of alluvial
fans with playa lake environments
and the principal mineral is sepiolite.
The second, the Esquivias-Cerro de los
Angeles deposits, contain larger proportions
of palygorskite and are located
in lacustrine environments.
MEGIAS et al. (1982), consider a compression
model of the Neogene basin
-~----- --~- Tri-whl.Ch the~ arkosic -n:iate~rii:lls ~ouid -
be erosive with respect to other materials.
The same authors, in the fi-
brous mineral genesis, distinguish between.
_.s~pm~Jmgh~_J:!!lcl __ ciistal «on
lap>> facies, precipitation in a lacustrine
environment and pedogenic
transformations.
The present study includes an
analysis of the influence of silicification
and calcretization on the genesis
of fibrous .clay minerals, in .fluvio-lacustrine
environments related
to seismic-tectonic activity and a
subaerial exposure.
Materials and methods
The materials studied are from a
zone 20 km south of Madrid, between
the villages of V aldemoro and Esquivias
(Fig. 1). The landforms consist
of residual reliefs with chert and
30Km
L----1
fill
L.!JJ~
1 Km
L-.J
EXPLANATION
C~rro Batollone'S
11 Malcovadero
~ Quarry
-{ Slope line
\ Lineot ions
f7
M
I .
1
M: Madrid
Fig. 1 -Location of investigated areas and quarries.

carbonate levels at the top (PEREZ
MATEOS & VAUDOUR, 1972). These
reliefs have several NW-SE and SW­
NE alignments caused by movements
of the Mio-Pliocene age (MARTIN
ESCORZA, 1976; PORTERO & AZ­
NAR, 1984). The visible part of these
materials contains layers of gypsum
and carbonate inserts in the upper
portion upon which there are laminated
green clays of 15 to 20 m.
Sepiolite and palygorskite deposits
are found on top of the green clays,
alternating with siliceous and carbonate
rocks of varying degrees of
compactness.
Two representative areas were
chosen for a detailed study. One,
close to Valdemoro, is known as Cerro
Batallones and contains a predominance
of sepiolite. The other ar~a,
called Malcovadero, is near Esquivias .. ,
and its main mineral is palygorskite.
Fieldwork consisted in extracting
li thologic columns and taking samples.
The mineral and chemical composition,
texture and fabric of each
sample were studied.
The mineral composition was studied
by means ofX-ray powder diffraction
analysis of the whole sample,
and of oriented aggregates of the less
than 20 Jlm after the elimination of
carbonates. Semiqu'antitative values
were calculated using reflective powers
(HUERTAS, 1969). The chemical
composition of the principal elements,
organic matter and the C/N
ratio were determined.
The texture was studied in thinsection
using a optical microscope.
Thin-sections were prepared after
Polygenesis of Sepiolite and Palygorskite ... 289
strengthening the samples by drying
them in liquid nitrogen and packing
them into methacrylate resin in a
vacuum chamber. The fabric was studied
by scanning electron microscopy
(Philips SEM-500), and an incorporated
EDAX analysis system.
Results.
CERRO BATALLONES ZONE
Lithology
Observations during fieldwork
allowed the differentiation of three
units from the base to the top, whose
thicknesses varied from 8 to 12 m.
Clayey Unit
This unit consists of clays and an
irregular distribution of siliceous
levels.· Throughout the profile, the
clays undergo changes in colour and
compactness. In the bottom, the clays
are laminated, compact and greenish
in colour. These gradually change to
brown and beige clays, depending on
the colouring effect of the Fe oxides.
These brown clays are sponge-like,
with a diffuse lamination, divided by
cracks filled with carbonates, and
with a remainder of thin levels of
green clay. The beige clays are mainly
lumpy in texture with a slight silicification.
In the top layer the clays are
dark-coloured with a scattering of
organic material, carbonate crusts
and siliceous lenses. Remains of sil-

290 S. Leguey, M. Pozo, J.A. Medina
icified roots and a pronounced prismatic
disjunction are observed.
The development and contact of
, the lenticular siliceous bodies are
very irregular, with thicknesses
varying between 0.3 and 1.5 m. They
are brechoid in aspect, with concretions
and pisolitic forms, containing
beige clay remains and with frequent
solution cavities.
Detrital Carbonated Unit
This unit contains detrital-carbonatic
sediments 3 to 6 m thick. The
detrital levels are found in the base
and the top of the unit and consist of
--- ------~----- ------greeii.iSh sail-dy and muddy materials,
( bl .,.

and silicification. Partially silicified
lutites appear in levels of 5 to 10 cm.
Mineral and Chemical Composition
' Polygenesis ofSepiolite and Palygorskite ... 291
chemical analyses made on the main
elements. The data indicate a similar
behaviour of the Al, K, Ti and Fe
whose incidence increases considerably
in the zones of the transition of
green clays to brown, and in the detrital
levels with prismatic disjunctions.
This incidence undergoes a
marked decrease in siliceous lenticular
bodies containing sepiolite imbeddings.
Worthy of mention is the
increase in the proportion of Na in
the upper lacustrine limestone levels,
and the relatively low incidence of
organic matter, oscillating between
1.7 to 2.2%, and a C/N ratio of 26:19.
Mineral Fabric
The results of the mineralogical
analysis of the overall sample appear
in Fig. 2(b). Clay minerals predominate
throughout the profile, except in
intercalated siliceous or carbonate
levels, where they coexist with
quartz, opal CT and calcite. Worthy
of mention is the presence of silica
(quartz and opal CT) and to a lesser
extent of feldspars(potassic and calcsodic),
in almost all samples.
In the transitional areas of green to
brown clay, calcite is found together
with small quantities of zeolites. Barite
is occasionally found in the green Thin sections of green clays,
clay.
observed under an optical micro-
Results for the fraction less than scope, display a laminar texture with
20 ).liD are given in Fig. 2(c). Mg- detrital imbeddings of muscovite,
smectites (reflection (060) at 1.522 A) .J quartz and feldspar. Under the scanare
the principal minerals found in ning electron microscope a general
··the green clays; mica appears to a glomerular structure produced by
lesser degree. The occurrence of these 1 mechanical deformations was
minerals progressively decreases in observed. The glomerules contain a
the transition to brown clays. Here, fabric that is partly laminar and
sepiolite predominantes and its partly turbulent, according to the
occurrence becomes exclusive in the classification of SERGEYEV et al.
upper zones of the beige clays. (1978), in which the smectite parti­
Sepiolite together with smectite, des are preferentially aligned (Fig.
mica and some palygorskite deposits 3a).
are found in the intermediate levels. The brown clays are irregular in
Sepiolite also appears in the clay in- texture with, microfissures filled
clusions of the siliceous lenticular with calcite, heterogeneous silicificaforms
and also in the inserts of clay tion and ochre tories. There is a tranlevels
in the upper unit of lacustrine sition in the fabric according to the
limestone.
smectite-sepiolite proportion. When
Figure 2(d) gives the results of the the smectites predominate, the fabric

292 S. Leguey, M. Pozo, J.A. Medina
a
b
Fig. 3 - Scanning electron micrographs of different fabric types of smectites and sepiolite aggregates:
a- glomerules of laminated smectite with mica inclusions (M); b- fibrous aggregates of sepiolite
in glomerules cracks; c- lumpy aggregates with roots and silica spheres (S); d- laminar
aggregates with oriented fibres (L) and radial fibre aggregates (R).
retains part of the characteristics of
that of the green clays, with fine
sepiolite crystals growing in the gaps
(Fig. 3b). With a predominance of
sepiolite, the fabric becomes globular
and the sepiolite aggregates cover
elongatedly semi-spherical surfaces.
The size of the crystals and fibrous
aggregates in both cases is close to
1-2 llm.
In the detrital levels with prismatic
disjunctions, a heterogeneous lumpy
mass of particles, with remains of
roots and with scattered silicification
was observed. Fibrous sepiolite
aggregates appear (Fig. 3c) which fill
pores and cracks. The same type of
aggregates, although more isolated,
are observed in the carbonate zones
where lumpy particles appear within
a micritic cement matrix. The average
size of these sepiolite aggregates
varies between 1-5 11m.
The sepiolite aggregates reach
their maximum size in the siliceous
lenticules. Two types of fibrous aggregate
are distinguished: one that is
laminar, measuring close to 10 11m,

(b) •t.

294 S. Leguey, M. Pozo, J.A. Medina
Detritic-carbonated Unit
This unit consists of detrital c ·­
carbonated sediments, of varying
granulation, and its thickness ranges
between 2-5 m. The materials in the
bottom are sandy-silt with soft green
clay imbeddings and limestone fragments,
which are impregnated by
yellowish carbonates and correspond
to debris flow type deposits. At the
upper part, the materials are finer
and are comprised of carbonate muds
and grey lutites that originate from
clay. Remains of vertebrates can be
seen in these deposits, which are of
the mud flat type. Of interest in this
unit is the presence of an inserted
.. -----------laminated, dark-coloured siliceous
level. This level shows evidence of
slumping and contains small compression
faults, which give folding
and fractures filled with white clays.
Carbonated Unit
It is 2-3 m thick. The bottom con"
tains lacustrine, laminated carbonate
levels, containing plant and ostracod
remains, which alternate between
dark striped siliceous levels, which in
turn towards the top become carbonate
muds with acicular morphologies.
Fine layers (2-3 cm) of silicified
clays are imbedded between the
carbonatic and siliceous levels.
Mineral and Chemical Composition
Results of the mineralogical analysis
are given in Fig. 4(b). From the
overall composition of these materials,
it is observed that the clay and
siliceous minerals (quartz and opal
CT), which predominate in the lower
and middle zones, display an antagonistic
effect with respect to the calcite
the main mineral in the upper
zon~. Dolomite appears among the
brown clays and lenticular carbonates
of the lower unit.
Results of the fraction of less than
20 !-LID are given in Fig. 4(c). The green
clay composition is similar to that
described in the results from Cerro
Batallones. Th~ smectite incidence
gradually decreases in the transition
towards the upper levels, where as
the sepiolite and palygorskite content
increases. Palygorskite is the main
mineral in the middle zone, but its
incidence progressively decreases towards
the upper zone, coinciding
with the zone of carbonate muds,
where it is found in equal quantities
with sepiolite, smectite, illite and
traces of kaolinite deposits. The very
fine clay layers, interbedded between
lacustrine siliceous and carbonate
levels, display a high palygorskite
content.
Results of the chemical analysis
made on the principal elements, are
given in Fig. 4(d). The behaviour of
Al, K, Ti and Fe is similar to that
observed in Cerro Batallones, :Vith
marked increases. coinciding with the
areas of transition of green clay to
brown and in the zones with. disjunction
and subaerial exposure.
Mineral fabric
Thin sections of clay ma'terials present
a brechoid aspect with general-

-
Polygenesis of Sepiolite and Palygorskiti.-.. 295
ized silicification and numerous
cracks and pores filled by carbonates.
The fabric is either glomerular or
globular, depending on the smectite
content. Fibrous aggregates, of 1-5
J..Lm, appear among the glomerules
and their number tends to decrease
when the carbonate content increases
(Fig. Sa).
The carbonatic lenticules embedded
in the clay are made up of amicrocrystalline
part containing eroded
quartz grains, pisolites and micritic
carbonate grains which, in agreement
with KLAPPA (1983), can be·
considered as globular calcretes.
In the detrital-carbonate levels,
lumpy micritic textures are observed
with development of gravelar morphologies.
A fenestra! porosity, with
sparitic cement filling and seldom of
a gypsum pseudo-morphology, is
observed.· Fibrous minerals, of no
more than 10 J..Lm, are found filling in
pores and cracks.
The maximum development of
sepiolite and palygorskite fibrous
aggre.gates is observed in the grey
Fig. 5- Scanning electron micrographs of different fabric types of palygorskite and sepiolite aggregates:
a- fibrous aggregates (Sp-P) and calcite grains (Ca); b- sepiolite fibres refilling voids; c­
globular and acicular aggregates of palygorskite (G and A) with calcite granes (Ca); d- bacillar
aggregates of palygorskite (B) between siliceous layers (S). ·

T
296 S. Leguey, M. Pozo, J.A. Medina
and white clay zones, which are the organic matter brings about the
found in the walls and at the top of ... _transformatiqn into_~b~ncied grey o­
the siliceous levels. In the case of grey pals, with their predominance of opalclays,
comprising predominant quan- CT. According to BERNER (1980) the
tities of sepiolite and some palygor- decomposition of organic matter proskite,
the fabric consists of irregular duces acidic conditions, favouring
particles with large holes where fine the dissolution of biogenic silica,
sepiolite crystals and aggregates de- which subsequently reorganizes into
velop, of 30-50 ).liD in size (Fig. Sb). In cristobalite.
the white clays, which are made up The composition of massive brown
exclusively of palygorskite, the fabric chert is complex. Opal-CT and quartz
is globular with acicula aggregates, appear in similar proportions and
which are shorter (4-6 ).lm) and thick- they generally contain considerable
er than the sepiolite aggregates (Fig. quantitites of sepiolite and/or paly­
Sc).
gorskite and sometimes smectites
The levels of laminated clays with and diatoms.
palygorskite when embedded in the Their texture is brechoid with a
.. -·--------- lacustrine unit, present a layered fah- · pseudo-globular fabric, made up of
ric. This fabric is made up of silica irregular nodules and petaloid forms
spheres whose surfaces have sepa- with traces of desiccation. The
rated. The resulting gaps contain nodules contain disordered silica and
bacillary fibrous forms, which are fibrous minerals, whereas the petalgenerally
very short, of approximate- oid forms have a leaf-like structure
ly 1 ).liD (Fig. Sd).
of cristobalite laminae and aureolas
of crypto-crystalline quartz.
The porous nature of these brown
Silcretes
chert favours the reaction with Mg,
which explains the noteworthy fibrous
minerals development over
and at the side of these materials.
The silica levels appearing between
the different materials of the
two zones under study, have been
classified into three types: black o­
pals, banded grey opals and massive
brown chert. For the degree of order
of the silica we have used the
nomenclature of JONES & SEGNIT
(1971).
Black opals are a mixture of opal­
A, opal-CT and organic matter.
Biogenic in origin, black opals are
formed from silicified plant stems
and diatoms. The decomposition of
Discussion of results
The genesis of minerals in sepiolite
and palygorskite type clays, has to be
analyzed by means of a series of complex
transformations beginning with
the subaerial exposure of green clays
rich in Mg. This is followed by deposits
of new detrital and lacustrine
materials that interact among them-

selves, during the climatic, tectonic
and sedimentary evolution of the
basin. Briefly, three stages can be
distinguished:
Stage 1. Subaerial Exposure
Subaerial exposure of green clays
with expansive properties gives rise
to soils with very similar characteristics
to those described by AHMAND
(1983) in his study of vertisols. Of
particular interest is the presence of:
a) Slickensides in the green clays, b)·
lumpy forms with desiccation cracks
filled with calcite and ochre tones in
the brown clays, c) dispersed organic
matter, average content of 2% and an
elevated degree of evolution (C/N
ratio 20-25), d) pronounced prisrr;tatic
unit structures dark clays, an

298 S. Leguey, M. Pozo, J.A. Medina
green clay. There is evidence, in all of notable quantities of palygorskite
these materials, of desiccation and _in zone_N is due to the lack of arkose
·remains and the Al fixation by the organic
levels.
During the lacustrine sedimentation
and coinciding with desiccation
phases, thin films of sepiolite or palygorskite
are interbedded between
siliceous and carbonate levels. Sepialite
appears with calcite, which possibly
precipitates first at pH = 7.8
(GARRELS & CHRIST, 1965) and
forms small crystals of approximately
1 Jlm. The sepiolite next precipitates
at pH 8.2 (WOLLAST et al., 1968) .
in the interstices of the calcite crystals,
in the form of very small aggregates
of less than 0.5 JliD. The palygorskite
coexists with detrital minerals
and it preferentially forms between
layers of silica spheres. The
palygorskite aggregates lie normal to
the lamination and are rarely more
than 1 Jlm. Both the calcite and the
silica spheres serve as a support in
the growth of sepiolite and palygorskite.
subaerial exposure, giving rise to the
formation of calcretes and dark horizons
containing organic matter and
with prismatic splitting. The latter
are more common to zone N, whife
the calcretes appear more frequently
in zone S.
·The composition of the detrital
levels differs considerably. In zone N
there is a predominance of sepiolite
with smectites, micas and traces of
palygorskite towards the top, all of 1
which to a great extent reflect the inherited
characteristic of these materials.
__________ _The predominance of palygorskite
in zone S is due to the activity of Al
from the distal arkoses. Gypsum
pseudomorphs indicate that the presence
of salts favours the release of Al.
The palygorskite w~s formed by
precipitation in pores a.nd cracks during
the stages of dryness, under similar
conditions to those described by
MILLOT et al. (1969), for Morocco,
and by SINGER & NORRISH (1974),
for Australia. TRAUTH (1977) suggests
that the diagenetic formation of
palygorskite is brought about by the
diagenetic alteration of smectites.
VELDE (1985, p. 245) proposes a model
with the simultaneous precipitation
with aluminium clays.
A high concentration of Ah0 3 ,
Fe 2 0 2 , Ti0 2 is found in the dark horizons
with organic matter. A similar
phenomena has been observed by
WEAVER (1984) in interbedded soils
between palygorskite levels in the
Camelia Mine of Florida. The absence
Stage 3. Remobilization
Seismo-tectonic activity produces
slumping and compression faults.
The former only affects the. clay
materials and debris flow deposits in
zone S, while faults with shifts of
0.20-0.50 m are found on a regional
scale. Slumping brings about important
deformations in the hard silcrete
levels. These faults increase the circulation
of carbonated waters, which
become enriched with Mg and Al in

Polygenesis of Sepiolite and Palygorskite ... 299
the detrital levels and react with the
silcretes, giving rise to dissolution
phenomena, cryptocrystalline quartz
and sparitic carbonates, and diagenetic
aureolae of palygorskite and/or
sepiolite. These aureolae are white in
colour, asymmetrical and reach a
maximum growth in the palygorskite
zone, their thickness increasing with
the slope of the siliceous levels. There
is a greater AI and Mg activity in the
siliceous levels with a predominance
of opal C-T. This fact is due to the
greater porosity and specific crista-
Cad
I E
~~~ M
Pa
X-RAY POWDER DIFRACTION
PATTERNS. Cu KaRADIATION
SM
p
SP
Qp
Q
D
PI
F
c ...
I
(•)
ABBREVIATIONS
IQ
F I
SMECTITE
PAL YGORSK I TE
SEPIOLITE
OPAL c- r
QuARTZ
DoLoMITE
PliCA
fELDSPAR
CALCITE
INTERSTRATIFIED
PIICA-SMECTITE
ETHYLENE GLYCOL
)
(•)
, G
'v.;v:
}~(JM
30 20 10 30 20 ', 10 30 20 10
DEGREES
2 e
Fig. 6- X-ray powder patterns of characteristics materials. Cerro Batallones Zone: A- transitional
green to brown clays; B- beige clays; C- white clays; D- dark clays in detrital materials; E-laminated
clays in lacustrine limestones. Malcovadero Zone: F and G- green clays; H- grey clays; 1- white
clays; J and K- clays in calcrete; L- laminated clays in lacustrine limestones with silica layers.

300 S. Leguey, M. Pozo, J.A. Medina
halite spherules surface in compa- tation. The sepiolite and palygorskite
rison to the biogenetic opals, where~ .. formeclj:n_each~~nvi:r:()J;Jme:nt are disthe
organic matter possibly acts as tinguished by the size of the aggrean
inhibitor. The availability of silica gates which are of 1 J..lm, whereas
with a large reaction surface is an im- their size is 1-5 J..lm in paleosoils. In
portant factor in the neoformation of diagenesis, sizes of 2-6 11m are found
palygorskite. This fact has been con- for palygorskite and sepiolite aggrefirmed
in proximal arkoses cemented gates reach 10-50 J..lm. The diffractowith
palygorskite (LEGUEY et al., grams in Fig. 6 show the different as-
1984b).
sociations of these materials. It is ob-
Summarizing, three types of genet- served that there is a correlation beic
environment can be considered for tween the size of the aggregates and
these materials: paleosoils, diagenetic the perfection of the structural order
mobilization and lacustrine precipi- of the crystals.
T
I !
REFERENCES
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Wrldmg, N.E. Smeck and G.D. Holl, editors). Developments in Soils Science llB, Elsevier.
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geol. 32, 451-498.
BusTILLO M.A., 1982. Ageing features in inorganic continental opals. Estudios geol. 38, 335-344.
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Teplice 1979, 239-249.
GALAN E., CASTILLO A., 1984. Sepiolite-Palygorskite in Spanish Tert_iary basins: genetical patterns in
continental environments. Pp. 87-124, in: Palygorskite-Sepiolite. Occurrences, Genesis and Uses
(A. Singer and E. Galim, editors), Developments in Sedimentology 37, Elsevier.
GARRELS R.M., CHRIST L.L., 1965. Solutions, Minerals and Equilibria. Harper & Row, New York.
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390.
HUERTAS F., 1969. Minerales fibrosos de la arcilla. Su genetica en cuencas sedimentarias espanolas y
sus aplicaciones tecno/6gicas. Ph.D. Thesis, University of Madrid (Complutense).
HUERTAS F., LINARES J ., MARTIN VIVALDI J .L., 1971. Minerales fibrosos de la arcilla en cuencas sedimentarias
espanolas. 1.-Cuenca del Tajo. Bol. Inst. Geol. Min. LXXXII, 534-542.
JoNES J.B., SEGNIT E.T., 1971. The nature of opal. I. Nomenclature and constituent phases. J. Geol.
Soc. Australia 18, 57-68.
KLAPPA C.F., 1983. A process-response model for the formation ofpedogenic calcretes. Pp. 211-220, in:
Residual Deposits (R.C:L. Wilson, editor). Geological Society; Special Publication n. 11.
LEGUEY S., 0RDONEZ S. GARCIA DEL CuRA A., MEDINA J .A., 1984a. Estudio geoquimic"o y minera/6gico de
/as facies arc6sicas de la Cuenca de Madrid. I Congreso Espaii.ol de Geologia, Segovia, Tomo 11,
355-371.

Polygenesis of Sep_iolite and· PalygorskiiL. 301
LEGUEY S., CASAS J., VIDALES J.M., 1984b. Diagenetic palygorskite in marginalcontinental detrital
deposits located in the south of the Tertiary Duero Basin. Pp. 149-158, in: Palygorskite-Sepiolite.
Occurrences, Genesis and Uses (A. Singer and E. Galan, editors). Developments in Sedimentology
37, Elsevier.
LoPEZ VERA F.C., 1975. Hidrogeo/ogia regional de la cuenca del rio Jarama en Ios alrededores de
Madrid. Memorias del I.G.M.E. 91, 227 pp.
MARTIN EscoRzA C., 1976. Actividad tect6nica durante el Mioceno de la fractura del basamento de la
Fosa del Tajo. Estudios geol. 32, 509-522.
MEGIAS A.G., 1980. Rupturas sedimentarias en cuencas continentales: ap/icaci6n a la cuenca de Madrid
.. Aetas IX Congr. Nac. Sedimentologfa, Salamanca, Abstract.
MEGIAS A. G., LEGUEY S., 0RDONEZ S., 1982. Interpretaci6n tectosedimentaria de fibrosos de la arcilla en
series detriticas continentales. 5° Congr. Latinoamericano de Geologfa, Buenos Aires, Aetas 11,
427-439.
MEGIAS A.G., ORDON:Ez S., CALVO J.P., 1983. Nuevas aportaciones a/ conocimiento geo/6gico de la
Cuenca de Madrid. Rev. Mat. Proc. G.eol. I, Univ. Complutense Madrid, 163-191. .
MILLOT G., PAQUET H., RuELLEN A., 1969. Neoformation de l'attapulgite dans /es sols a carapaces
calcaires de la basse Moulouya (Maroc Oriental). C.R. Acad. Sci. Paris 268, 2771-2774.
0RDON:Ez S., GARCIA DEL CuRA A., 1983. Recent and Tertiary fluvial carbonates in Central Spain. Spec.
Pub!. Int. Ass. Sediment. 6, 485-497.
PEREZ MATEOS J ., VAUDOUR J ., 1972. Estudio minera/6gico y geomorfo/6gico de /as regiones arenosas a/
sur de Madrid. Estudios geol. 28, 201-208.
PoRTERO J.M., AzNAR J.M., 1984. Evoluci6n mor{otect6nica y sedimentaci6n terciarias en el Sistema
Central y cuencas limitrofas. (Duero y Tajo). I Congreso Espaiiol de Geologfa, Segovia, Tomo Ill,
253-263.
PosT J.L., JANKE C., 1984. Ballarat sepiolite, Inyo county, California. Pp. 159-168, in: Palygorskite­
Sepiolite. Occurrences, Genesis and Uses (A. Singer and E. Galan, editors). Developments in
Sedimentology 37, Elsevier.
SERGEYEV Y.M., GRAVOWSKA B., 0SIPOV V .I., SOKOLOV V .N., 1978. Types of the microstructure of clayey
soils. Pp. 319-327, in: Proc. 3rd Int. Congr. I.A.E.G., Sect. II, 1.
SINGER A., NORRISH K., 1974. Pedogenic pa/ygorskite occurrences in Australia. Am. Miner. 59, 508-
517.
SuMMERFIELD M.A., 1983. Silcrete. Pp. 59-92, in: Chemical Sediments and Geomorphology (A.S.
Goudie and Pyc. Kenneth, editors), Acade~ic Press.
TRAUTH N., 1977. Argiles evaporitiques dans le sedimentation carbonatee continental et epicontinental
tertiaire. Bassin de Paris, Mormoiron et Salinelles (France), !bel Ghassoul (Maroc). Sciences
Geologiques, Mem. 49, 195 pp.
VAUDOUR J., 1977. Contribution ii ['etude geomorphologique d'zme region mediterraneenne semi-aride:
la region de Madrid. Alterations, sols et paleosols. These, University of Aix-Marseille.
VELDE B., 1985. Clay Minerals. A Physico-Chemical Explanation of their Occurrence. Developments in
Sedimentology, Elsevier.
WEAVER C.E., 1984. Origin and geologic implications of the palygorskite of S.E. Unites States. Pp.
39-58, in: Palygorskite-Sepiolite. Occurrences, Genesis and Uses (A. Singer and E. Galan,
editors), Developments in Sedimentology 37, Elsevier.
WoLLAST·R., MACKENZIE F.T ., BRICKER O.P ., 1968. Experimental precipitation and genesis of sepiolite
at earthsurface conditions. Am. Miner. 53, 1645-1662.

Miner. Petrogr. Acta
Vol. 29-A, pp. 303·311 ( 1985)
Mineralogy and Genesis of the «Fardes Formation»
Bentonites, Middle Subbetic,
Granada Province, Spain
F. LOPEZ-AGUAY0 1 , E. SEBASTIAN PARD0 2 , F. HUERTAS 3 , J. LINARES 3
I Departamento de Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza,
Espafta
2 Departamento de Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Granada, 18002. Granada,
~~ .
3 Estaci6n Experimental del Zaidin, C.S.LC., Profesor Albareda 1, 18008 Granada, Espafta
ABSTRACT- The bentonites of the «Fardes Formation>> (Middle Subbetic,
Province of Granada, Spain) occurring in the basal member (Member-!) were
studied by XRD, including the determination of several crystallochemical
parameters, chemical analysis and SEM.
The main mineralogical association found is smectite, palygorskite, mica
and quartz. In the more northern outcrops, palygorskite is absent. Calcite,
dolomite and gypsum also appear as accessory minerals.
The most probable genetic process leading to bentonites is an alteration of
volcanic materials, close to basalts. The variable presence of palygorskite
may be related to pH oscillations resulting from the existence of compartments
within the basin, where the materials were deposited.
'·
Introduction
1 the Middle. Subbetic domain of
the so-called

T
304 F. L6pez-Aguayo, E. Sebastian Pardo, F. Huertas, 1. Linares
•
Pozo AI con
_.....
...........
IC.// ~
.... ?:>
Baza
•
~
\
10 20
1 2 3 4 5 6 7 8 9 10
------··-··-----~-~-------~-L__J-tlJ.l.U r:-:-::lmTil~~~===~[illJ~ftiiDilTTI~.,
c:i:8 ~ t:::::::=l ~ ~ ~ l.!!!!J
Fig. 1 ~Generalized geologic scheme of the Betic Cordillera, Granada-Jaen transversal (simplified
from LOPEZ GARRIDO & VERA, 1979). 1: Neogene-Quaternary; 2: Internal Zones; 3: Guadalquivir
Units; 4: Paleogene; 5: Internal Prebetic; 6: Intermediate Units; 7: External Subbetic; 8: Middle
Subbetic-Parapanda Unit; 9: Betic Dorsal and Oltrainternal Sub.; 10: Tri.assic; ~·~: Jurassic volcanic
rocks. The square indicates the area studied.
11
*
Methods
All samples were systematically
studied by XRD and chemical analysis,
following the same methodology
and techniques described in SEBAS­
TIAN PARDO et al. (1984). Consequently,
only the new data are collected
in this paper. However, mean
values of the previously studied (BA)
samples are also reminded in several
Tables (Tables 1 to 5). These samples
were also observed with SEM (Fig. 3).
Mineralogical and chemical characterization
The main mineralogical association
found is smectite, palygorskite,
mica and quartz, although palygorskite
is absent in the most northern
outcrops (Table 1).
From the measurement of the
smectite bo axis (mean value 9.028 A)
it is concluded that this mineral
belongs to the montmorillonitenontronite
series. On the other hand,
the mica is very uniform, as evidenc::ed
by the bo axis measurements
(mean value 8.999 A).
In order to obtain the most likely
chemical composition of the phyllosilicates,
the chemical analyses were
recalculated (Table 4), by subtracting
the HzO+ and quartz contents,
where the quartz content was determined
by XRD. The results, includ-

-
Mineralogy and Genesis of the > area, Middle Subbetic (modified from COMAS,
1978). Pm, Mr, Ga, La, De, Tc, AI, Vt and Ba indicate the names of the villages in the area studied.
1: Quaternary; 2: Neogene; 3: Paleogene; 4: Orogenic materials of o.ther Formations; 5: «Fardes
Formation>>; 6: Outcrops studied.
TABLE 1
Mineralogical composition (XRD) for< 20 JliD fraction
Global Mineralogy
Clay Mineralogy
sample Quartz Phyllos. Calcite Others Smec. Palyg. Mica
BA 15 79 6 49 ~ 27 24
MP-1 9 84 7 61 21 18
MP-2 6 91 3 64 18 18
MP-3 7 72 21 51 32 17
MP-4 5 92 3 55 22 23
MP-S 9 80 11 80 tr 20
MP-S' 10 85 5 29 44 27
MP-6 16 75 9 74 26
MP-7 11 68 21 75 25
MP-8 17 83 72 28
MP-9 20 80 68 32
MP-10 20 80 72 28
MPB-1 5 54 25 Plag. 16 n.d. n.d.
MPB-2 13 87 64 36
MPB-3 5 43 30 Plag. 22 n.d. n.d.
MPB-4 18 59 23 52 '48
Smec.: Smectites; Palyg.: Palygorskite; Plag.: Plagioclases; Phyllos.: Phyllosicates; tr: traces;
n.d.: not determined

306 F. L6pez-Aguayo, E. Sebastian Pardo, F. Huertas, J. Linares
T
I
I ' 1
I
TABLE 2
Crystallochemical parameters (XRD)
Smectite
Mica
sample bo VIP ~001 004/002 ~0
BA 9.028 0.86 14.6 Q.32 9.002
MP-1 9.028 0.83 1S.2 0.38 8.998
MP-2 9.01S 0.87 1S.2 0.40 8.990
MP-3 9.044 0.84 1S.S 0.36 9.007
MP-4 9.02S 0.89 14.8 0.37 8.994
MP-S 9.033 0.78 1S.2 0.36 8.994
MP-S' 9.033 0.74 1S.2 0.40 9.004
MP-6 9.021 0.86 1S.2 0.49 8.992
MP-7 9.048 0.84 1S.2 O.S7 9.002
MP-8 9.020 0.80 1S.2 0.58 8.998
MP-9 9.033 0.8S 1S.O 0.4S 9.007
MP-10 9.020 0.84 15.2 O.S4 8.992
mean 9.028 0.8S 14.8 0.37 8.999
MPB-1 0.53 1S.S
MPB-2 9.002 0.77 15.0 0.55 8.996
MPB-3 0.50
MPB-4 9.031 0.59 15.8 0.50 9.004
--·· ·---··--~--·
MPB samples correspond to an altered volcanic outcrop
TABLE 3
Chemical analysis < 20 Jlm fraction
sample SizO Alz03 TiOz Fez03 CaO M gO Na 2 0 KzO Hzo+ Total
BA 61.65 17.29 0.99 S.58 1.62 2.46 0.63 2.00 . 7.37 99.59
MP-1 63.95 16.6S 1.36 S.38 0.62 4.09 0.57 1.31 6.05 99.98
MP-2 61.09 18.36 1.44 5.71 0.71 4.34 0.52 1.57 5.95 99.69
MP-3 60.59 20.03 1.08 6.12 0.67 4.10 0.49 1.32 5.74 100.14
MP-S 60.45 18.35 1.02 6.84 2.17 3.00 0.53 1.42 6.71 100.49
MP-6 62.93 17.83 0.80 6.71 0.99 3.31 0.73 1.51 5.81 100.62
MP-7 57.33 17.32 0.66 14.06 1.31 1.17 1.13 1.36 636 100.70
MP-8 63.73 17.61 1.11 S.73 1.03 2.9S 1.01 1.49 6.04 100.70
MPB-1 51.76 21.65 2.63 4.94 4.6S 3.76 2.96 1.82 S.82 99.99
MPB-3 S3.66 13.87 2.65 9.06 10.29 0.22 2.68 1.29 6.27 99.99
MPB-5 56.48 15.88 3.04 5.70 4.40 1.35 4.46 2.94 5.74 99.99
ing the percentage of octahedral
occupation of phyllosilicates, are
summarized in Table 6. A more detailed
study of the chemical composition
of these minerals was reported in
the previous paper above mentioned.
Genesis of the Bentonites
The pelagic and hemipelagic levels
of Member I of the Fardes Fm. are, at
the present time, considered to be
sedimentary, as stated by COMAS

Mineralogy and Genesis of the «Fardes Forrnation-,>Bentonites ... 307
TABLE 4
Recalculated chemical analysis, without H20+ and quartz
sample SizO Alz03 TiOz Fez03 CaO MgO NazO K 2 0 I.S.
BA 59.82 22.25 1.16 8.05 2.13 3.13 0.80 2.57 21
MP-1 64.70 19.60 1.60 6.33 0.73 4.82 0.67 1.54 36
MP-2 62.59 20.86 1.64 6A9 0.81 4.93 0.59 2.12 35
MP-3 61.32 22.92 1.24 7.00 0.77 4.69 0.56 1.51 34
MP-5. 60.69 21.64 1.20 8.07 2.56 3.54 0.63 1.67 25
MP-6 59.55 22.62 1.02 8.51 1.26 4.20 0.93 1.92 27
MP-7 55.59 20.78 0.79 16.87 1.57 1.40 1.36 1.63 7
MP-8 60.17 22.68 1.43 7.38 1.33 1.80 1.30 1.92 26
MP-9 52.56 27.75 1.27 9.14 0.90 4.82 1.21 2.34 27
mean 59.73 22.30 1.27 8.38 1.69 3.58 0.86 2.20 28
MPB-1 54.98 23.00 2.79 5.26 4.94 3.99 3.14 1.93 28
MPB-3 57.26 14.80 2.83 9.67 10.98 0.23 2.86 1.38 2
MPB-5 59.93 16.85 3.23 6.05 4.67 1.43 4.73 3.12 9
TABLE 5
Trace elements analysis (ppm)
sample V Cr Mn Co Ni Cu Pb Sr
BA 156 104 1573 "150 1071 74 79 128
MP-1 182 138 288 138 1327 52 83 188
MP-2 193 146 214 195 1407 55 88 100
MP-3 182 138 360 184 1328 69 187 94
MP-S 193 146 749 195 1409 73 133 100
MP-6 176 67 279 178 1285 67 141 91
MP-7 175 53 5059 177 1064 66 180 181
MP-8 183 139 188 185 1336 52 189 189
MP-9 170 128 188 171 1445 64 136 263
mean 168 106 1493 163 1185 69 107 138
MPB"1 169 256 295 171 1440 32 174 175
MPB-3 140 386 243 214 1489 32 117 176
MPB-5 172 65 395 217 1466 16 177 266
Basalts(*) 266 235 1318 50 50 90 3
(*)Mean values in WEDEPOHL (1969-1978)
(1978). However, even assuming that ited in a passive continental margin,
the final process had this character, during Cretaceous anoxic events.
the genesis of their main constituents GARciA-DUENAS & COMAS (1983)
must have been more complex. point out the existence of in this margin and think that
sider that these sedimen ts were-depos- the facies of the Fardes Fm. accumu-

308 F. L6pez-Aguayo, E. Sebastian Pardo, F. Huertas, J. Linares
T
I
2
3 4
Fig. 3- Scanning electron micrographs of smectites (photos 1 and 3) and palygorskites (photo 2 and
4). The palygorskite crystals are partially deformed.
lated in such a type of basin.
With regard to the origin of
sedimentary material, two hypotheses
may be proposed. The first one,
accor~ing to CHAMLEY & ROBERT
(1982) is based on the inheritance of
clay minerals -mica, smectite and
palygorskite- previously formed in
soils and marginal basins. The
second one, according to THIEDE et
al. (1982), postulates that these
minerals derived from the alteration
of volcanic materials, without discarding
their terrestrial origin in·
some places. SEBASTIAN PARDO et
al. (1984) conclude, from mineral-
TABLE 6
Mean data(%) of octahedral occupation in clay minerals
mineral
mica
palygorskite
smectite
78
58
61
6
3
2
10
14
21
6
25
16.

Mineralogy and Genesis of the «Fardes FormatTon» Bentonites ... 309
ogical and chemical data, that the latter
explanation is the most plausible.
The widening of this study to a
larger number of outcrops, together
with the possibility of determining,
in some cases, less mobile elements
such as Y, Nb and Zr, allow us to indicate
some facts, which can contribute
to the assessment of the origin of
these materials:
(a) Chemical composition of bentonites
is very homogeneous, for both
major and trace elements.
(b) The trace element content for
elements such as Cr, Co, V and Ni, as
well as Mn, is similar to that of basic
volcanic rocks (Table 5).
(c) Y, Nb and Zr contents in the
analyzed samples, are comparable
with the mean values of Subbetic
ophites (PUGA, personal communication)
and with those determined, by
PEARCE & CANN (1973) for c;ntinental
basalts (Table 7). The plotting
of these data in the PEARCE &
NORRY's ·diagram (1979) (Fig. 4),
allow us to ascribe these materials to
continental basalts, although on the
triangular diagram of PEARCE &
CANN (1973) they fall into the calcalkaline
basalt field, probably due to
a loss of Ti, present in silicates, during
the alteration processes.
(d) There is also a great uniformity
in the mineralogical composition of
samples, although in the more
northern outcrops palygorskite is
lacking. This absence does not produce
apparent changes either in the
smectite and mica parameters, or in
the trace element content (Tables 2
and 5).
If the scheme of «suspended
basins», consequently restricted,
proposed by GARCIA-DUENAS &
COMAS (1983), is accepted, the absence
or presence of palygorskite may
TABLE 7
Less mobile elements analysis (ppm) (XRF)
sample Zr y Nb Ti
BA-2· 198 39 16 3438
BA-5 192 44 12 7601
BA-ll 191 44 12 5991
BA-17 195 41 17 3890
BA-21 200 34 13 8389
BA-25 206 34 10 5152
MP-2 195 38 11 8758
MP-4 167 32 10 8747
MP-8 231 47 11 6650
mean 197 39 12 6513
MPB-1 143 35 7 16129
MPB-4 224 35 7 4986
Subbetk ophites(*) 150 33 15 9723
Continental basalts ( 0 ) 215 29 20 15150
Calc-alkali basalts( 0 ) 52 19 1.5 5150
('') PUGA, personal communication; ( 0 ) data from PEARCE & CANN (1973)

310 F. L6pez-Aguayo, E_. Sebasti6.r.z Pardo, F. lfuertas, J. Linares
10
8
>-
' s..
N
• CB
... so
6
•
• ••
4 ••
... • •
2
Zr (ppm)
1+-------,-------,----r--~~------,-------.---~~
10 60 100 600
Fig. 4- PEARCE & NORRY's diagram (I 979), including the bentonite data. A: Island-arc basalts; B:
Mid-ocean basalts; C: within-plate basalts. BF: Bentonites «Fardes Fm.>>; SO: Subbetic Ophites;
CB: continental basalts (PEARCE & CANN, 1973). .
-3
-2
y
::;;: "'
"' 0
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--- pH8
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I
I
I
I
I
I
I
I
I
I Log [H 4
s;o 1 4
-6
-5 -4
Fig. 5 - Stability fields of montmorillonite and palygorskite at pH=7 and pH=.8 (modifield from
WEAVER & BECK, 1977).
"·'
-3

Mineralogy and Genesis of the «Fardei Fo;;;_ation» Bentonites ... 311
be simply explained by pH oscillations.
According to WEAVER &
BECK's (1977) equilibrium diagram
(Fig. 5) small changes of this parameter
widely modify the palygorskite
and smectite fields.
From the above considerations, it
is possible to conclude that the bentonites
of the Fardes Fm. derive from
the alteration of volcanic rocks, probably
basalts. However, according to
THIEDE et al. (1982) the terrigenous
origin of some minerals in these
levels should not be discarded.
Accepting this hypothesis, the main
unresolved problem is to determine
the materials which undergo alteration.
In this regard, within the turbiditic
levels of this formation there
are relicts of basic volcanic rocks, derived
either from ophites or from the
Middle Subbetic Crest, whose mineralogy
and chemical character is very
similar to that of bentonites.
REFERENCES
CHAMLEY H., RoBERT C., 1982. Paleoenvironmental significance of clay deposits in Atlantic blacb
shales. Pp. 101-112, in: Nature and Origin of Cretaceous Carbon-Rich Facies (S.O. Schlanger
and M.B. Cita, editors), Academk Press, London.
CoMAS M.C., 1978. Sabre la geologia de Ios, Mantes Orient ales: Sedimentaci6n y paleogeografia des de el
Jurasico al Mioceno superior. Ph. D. Thesis, University of Pais Vasco.
GARCIA-DUENAS V., CoMAS M.C., 1983. Paleogeografia mesozoica de las zonas externas beticas coma
borde de placa Iberica entre el Atlantico y la Mesogea. Corn. X Cong. Nac. Sedim. Menorca.
5.26-5.28.
LOPEZ GALINDO A., CoMAS MINONDO M.C., FENOLL HACH-ALI P., 0RTEGA HUERTAS M., 1985. Pelagic
Cretaceous Black-Greenish Mudstones in the Southern Iberian Paleomargin, Subbetic Zone, Betic
Cordillera. These Proceedings.
LOPEZ GA_RRIDO A.C., VERA J., 1979. Mapa de Distribuci6n de Unidades en las Zonas Extemas de las
Cordzlleras Beticas. In: «La microfacies de Jurasico y Cretacico de las zonas exterhas de las
Cordilleras Beticas>>. University of Granada, I.S.B.N. 843380133.3. ·
PEARCE J .A., CANN. J .R., 1973. Tectonic setting of basic volcanic rocks determined using trace elements
analyses. Earh Planet. Sci. Letters 19, 290-300.
PEARCE J .A., NORRY M.J ., 1979. Petrogenetic implications of Ti, Zr, Nb and Y variations in volcanic
rocks. Contrib. Mineral. Petrol. 69, 33-47.
SEBASTIAN PAR~O E., LOPEZ-AGUAYO F., HUERTAS F., LINARES J., 1984. Las bentonitas sedimentarias de
la Formacz6n Fardes, Granada, Espafza. Clay Minerals 19, 645-652.
THIEDE J., DEAN yY.E., C~AYPOOL G.E., 1982. Oxygen-deficient depositional paleoenvironments in the
Mzd-Cretaceous tropzcal and subtropical central Pacific ocean. Pp. 79-99, in: Nature and Origin
of Cretaceous Carbon-Rich Facies (S.O. Schlanger and M.B. Cita, editors), Academic Press
London.
'
WEA~ER C.E:, BEe~ K.C., 1977. Miocene of the S.E. United States: A model for chemical sedimentation
zn a pen-marzne envzronment. Sedimentary .Geology 17, 1-234.
WEDEPOHL K.H. (editor), 1969-1978. Handbook ofGeochemistry. Vol. I., Springer-Verlag, Berlin.

T l
I

-
Miner. Petrogr. Acta
Vol. 29-A, pp. 313-338 (1985)
Argillogenesis and the Hydrolysis Index
J. THOREZ
Laboratoire de Geologie des Argiles, Institut de Mineralogie, Universite de Liege, 9 Place du 20 Aout, Liege,
Belgique
ABSTRACT - Argillogenesis is a global process that occurs at the contact
between the lithosphere and the hydrosphere. It proceeds through the progressive
hydrolytic weathering of an outcroping silicate mineral or silicatebearing
material. However, the transformation into clays and clay minerals
sensu stricto yields considerable variability in composition, relative abundance
and crystallini ties of the mineral species as well as in types of association.
The large fan of mineral heterogeneities now identified severs or impedes
any global appraisal for the multiple «weathering sequences» listed until
now and reported in the literature. After reviewing the role and importance
of the external and internal factors that govern and orientate the weathering
sequences, a is proposed in order to quantify within a
concise form the global and final weathering intensity that has affected the
parent material. Data for this mathematical device are provided by XRD
analysis of the less than 2 micron fraction ..
Introduction
The very process that leads to the
formation of clay minerals sensu
stricto at or near the surface of the
lithosphere can be summarized as
follows:
Pare-nt silicate(s)
(mineral,
rock)
+ Solution
(ions)
residual
parent
minerals
+ secondary
minerals
plus clays
+ solutions
(enriched
in ions)
Such a concise' formulation describing
a process generalized in
Nature is supported by a complex
background and by the interplay of
several external and internal «Stimuli».
In the scope of the present paper
there appears no need to once again
report all these «Stimuli» in detail;
some quotations will suffice to emph"'-size
the peculiarities of argillogenesis.
VELDE (1985, p. 359): «Clay
minerals are the major solid phases
present during the immense chemical
transfer process which occurs at
or near the earth's surface. In clay environments,
one finds the most ex-·
treme chemical segregation known in

T
314 J. Thorez
geological cycles. If we wish to interpret
the past (geology) we must ..
understand the reasons for the
appearance of clays which remain>>.
Figure 1 illustrates the participation
of the clay minerals in the geological
cycle.
MILLOT (1967, p. 355, translated
excerpt): «Within the main parts of
its surface, the crust is composed by
silicates assembled into rocks: granites,
gneiss, slates, shales and lavas.
When croping out at the surface and
able to escape a tob vigorous erosion,
these silicate-bearing rocks are
doomed to destruction. The normal
state at the earth's surface is the clay
state when thermodynamic equilib-
----rium-:nas·oeei1 reached with time. If
the lithosphere is essentially feldspathic,
the surface is essentially devoted
to clay. The clay minerals are
pecgJia,r- Qc:'!g.u~.t; __ they_ are __ the intermediates,
at the level oftheir crystallochemical
behaviour, between inert
minerals (such as quartz) which
remain stable throughout most the
crust's history, and the soluble but
highly mobile minerals (such as salts,
carbonates, sulphates, ... ) which are
readily modified. When croping out
the lithosphere undergoes a severe
evolution by becoming transformed
into clay. But the transformation is
not a simple operation completed at
once. On the contrary, the evolution
is gentle, variable, reluctant, progressive,
easily submitted to deviations
or reversals».
BRHART (1956) (translated excerpt):

Argillogenesis and the Hydrolysis liid~ 315
history which cannot be explained in
a simple way ... ».
LUCAS (1962; 1968) has clearly
(re)defined the very role of the
geochemical process in the evolutionary
behaviour of the interstratified
clay minerals in the hydrosphere by
recalling aspects concerning heri ~
tage, rejuvenation, degradation,
aggradation, neoformation (Fig. 1).
He particularly emphasized the place
of these random mixed-layers (his
«edifices») as a «printing mark>> in
the transformations: these «Structures>>
are a kind of crystallochemical
compromise in the form of an unstable
equilibrium between the composition
of the parent minerals and
the environmental conditions that
prevail during the transformation.
SUDO et al. (1962, p. 378) considered
indeed: «Normally the mixedlayer
minerals are found where there
has been successive attack under
different conditions of chemical environment
or in an area that is transitibnal
between two different chemical
environnien ts ».
TARDY (1969) demonstrated the
importance of «ion-chromatography
in the landscapeS>> which ventilates
laterally the elements removed
(le~ched) from the parent silicate
structures, and their transfer or successive
«blocking>> within and by environments
that bear either «confining
to confined>> or «leaching to
leached>> characteristics. Such a
«chromatography>> involves the action
of the climate (temperature,
rainfall, and drainage).
The reality of the
at the surface is nowadays wellsupported
by an explosive literature
which demonstrates the multiplicity
of pathways as well of clay products
(nature, abundance, associations) in
the vast chemical transfer cited by
VELDE (op. cit.). Therefore a certain
need ari:r:es for a globalization that
seems difficult to undertake because
'of the «kaleidoscopic>> character of
argillogenesis when taking into
account the interplay of all the vectors,
factors and parameters at work
simultaneously.
The weathering sequences
XRD analysis is and will remain
without any doubt the paramount
tool in the investigation of clay
minerals. This privilege is due to the
fact that this investigational method
can face the case of multicompositional
mineral phases whereas other,
more sophisticated methods better
suit when analysing monophases,
even rembering that XRD analysis
still lacks any standardized method
for sample preparation, mineral determination
and quantitative evaluation
(THOREZ, 1985). Now polymineral
phases are a general rule in
the argillogenetic process: an increasing
awareness of the great varie-.
· ty of clay minerals and of their nearly
infinite potentiality to be engaged in
multicomponent admixtures and interstratifications,
too, has resulted in
a greater number of clay scientists
(clay geologists, pedologists ... ) to become
concerned with the genetic and

316 J. Thorez
descriptive ways in which the complexity
of both the mineralogy and
association of these minerals (simple
clay minerals and mixed layers) can
be formulated within the best concise
form: the «weathering sequence>>.
The vastness of cases means that the
latter would better be considered in
the plural.
The investigation about the weathering
processes, and their understanding,
has involved a twofold
approach one purely mineralogical
and crystallographical, the other,
geochemical. The form took mainly
its interest in the «follow up» of the
variability of the minerals involved
inJh~ '\V~~!h~rjng se9.11«nc:es,_ of tht!ir
mode of succession and relays starting
with the parent silicate material,
and ending with either the clay
minerals or their pure withdrawal
from the system. The geochemical
approach has been the pathway of
Millot's school in Strasbourg, with
particular emphasis on the relationship
between the clay minerals
and landscape evolution, by integrating
the geochemical pathways (heritage,
degradation ... ). Here the scale of
the investigation encompasses the
meter (profile) up to the km 3 volume
Weathering of a granite in temperate conditions
FRESH MINERAL
I
CC>NTACT- . . I PLASMIC- SYSTEM
MICROSYSTEM PRESERVED MODIFIED
STRUCTURE
I
FISSURAL
SYSTEM
DEPOSIT
FRAGMENTATION DISSOLUTION
r:-::cc::-:-=-::= _......M 9 -sequence -dioct- vermiculite + kaolinite-montmorillonite + kaolinite
I MUSCOVITE! "'-AI _ sequence-illite + kaolinite + (intergrade J-beidellite + kaolinite
DEPOSIT
NEOFORMATION
I BIOTITE 1-(mica -vermiculite) +AI- vermiculite + kaolinite + Fe -Ti -oxides
w-
~ROFISSURE ! IN~~~:i FRACTURE
~
z /~ -~~~ICITE
1jj ~AOUNITE
CLOUDING
SERICITE FRACTURE FRAGMENTATION
r:=:-:-:::-=:-:--::::::1 .....,... kaolinite + AI - vermiculite + sericite
I ORTHOCLASE I ......_ kaolinite • smectite + sericHe
DISSOt.UTION
PLASMA
__. kaolinite + Al-vermiculite + sericite
I PLAGIOCLASEI "'- kaolinite + smectite + sericite
. FRACTURE WITH CUTANE
FRAGMENTATION
DISSOLUTION
Fig. 2- Sequences of weathering and associated transmineral modifications occurring during the.
weathering of a granite submitted to argillogenesis in temperate conditions (after MEUNIER,
1977, modified).

of clays and clayey materials in
geomorphological environments.
Other researchers (i.e. MEUNIER,
1977; MEUNIER & VELDE, 1979)
have started recently to try to decifer
the weathering processes at the scale
of the compositional minerals forming
a rock, by analysing both what
occurs in the mineral grain itself, and
in the immediate vicinities. This
punctual approach is, in the opinion
of the present author, very noteworthy
because, in place of a global and
«blind» qualitative evaluation (as
performed normally when studying a
whole sample), here a «mineralogic
particularism» can be reached and
also easily detected by the same
method (XRD). The «geochemical
Argillogenesis and the Hydrolysis bidex 317
.,__.INCREASINC OIMENSIONS
OF THE ~UNITS"
wounds» suffered by each mineral
grain can be evaluated separately
and firmly before a more global
analysis provides what occurs to the
rock itself. Each mineral can be
traced for itself, step-by-step, or
stage-by-stage. Figure 2 is a synthetic
illustration of MEUNIER's work in
1977, which displays simultaneously
the weathering sequences of common
minerals in a granite and the relationship
with the characteristics of
the micro-environment.
Finally an «all-scale approach»,
from the A of the compositionallayer
of the clay minerals towards the km 3
in volume of clayey bodies in the
landscape with a «zooming overview>>,
is the mutual integration of
'~~,m-

318 J. Thorez
the scales at which, each time, any
clay mineral can be looked at: thi~
has led the present author to introduce
the notion of a
(Fig. 3) (THOREZ, 1987). In the scope
of the weathering, an

Argil/ogenesis and the Hydrolysis IndeX 319
TABLE 1
Various clay mineral reactions in soils with indication for their weathering stability index
numbers (see Table 4) (JACKSON, 1963)
Micas
Biotite (4)
Muscovite (7)
Illite (7)
~ Vermiculite (8) ~ Montmorillonite (9) :::; Pedogenic 2:1-2:2
swelling 18 A
\/
Integrade
\
(Fe, Mg, Al) ~Secondary
Chlorite (4) Chlorite (8)
--+ Pedogenic 2:1-2:2
14 A intergrade
/Kaolinite and
~ Al-Chlorite (9) Halloysite (10)
teration from one mineral to another,
with possible reversals.
The reaction (Table 1) does not incorporate
allophane (stage 11), hematite
(12) and anatase (13). In its present
for the reaction has passed large;:_
ly in the text-books and other publications
as a kind of . Therefore it
seem worthwhile to recall the nature
of some of the most important
whose interplay conditions the
development of the reaction. The. list
is not exhaustive, and the is random:
1. The reaction is triggered only if
the parent material is a silicate or a
silicate-bearing material. The silicate
nature is thus a necessary premise
and the of the solutions
(percolating fluids) if the reaction is
to develop. Other parameters for the
parent material comprise: the grainsize
(decreas_ing size or minuteness of
the particle hastens argillogenesis);
the aggregaticm mode (structural
arrangement of the mineral grains),
the occurrence of (micro )fissures
which will favour percolation.
2. The composition of the fluids is a
st]\ict conditiQn in the matter of richness
in ions (saturation status), available
volume (importance of rainfalls,
in terms of volume, intensity, regularity)
and capacity of percolation
(occurrence of (micro)fissures in· the

-~~-~-----~--~----~--
320 J. Thorez
bedrock submitted to clay-transformation).
Thus the availability of solutions is
strictly dependent on the climate
(rainfall, temperature). Percolating
but de- or unsaturated solutions will
better deplete the parent minerals
from certain elements (alkalis, Fe,
Mg, Si) whereas saturated solutions
will induce a decreasing alteration.
The latter is a matter of reactivity of
the minerals towards fluids. The
reactivity, in turn, is triggered and
developed at three levels or scales as
substantiated by MEUNIER (1977).
The weathering occurs first in the
micro-environments, inside the
mineral grains, and is facilitated by
the presence of a « transmineral >>
microfissural system, and also develops
in the vicinities of the grains
thanks to an original micro-porosity.
The clay products are generally
monophase and are strictly under the
dependence of the percolating fluids.
The second level is associated with
the opening and widening of the
(micro) fissures, a condition for an increasing
Circulation of the solutions.
. The products of the reaction mineral
+ waters are multiphase. This latter
characteristic points to either the
cumulative effects of the reaction
operating inside the mineral grain
with a change of geochemistry (successive
clay products are generated
in situ and relay one another in the
microenvironment), or to a cumulative
mineral effect produced by the
alteration of several grains of the
same composition and/or different
nature, undergoing the alteration at
different rates. The multiphase composi!i9E~].2
___ ~ls

Argillogenesis and the Hydrolysis Index 321
completed. This means that, in addi- sive but moderate weathering. The
tion to the pursuit of the weathering, chlorite weathers first and as long as
time (in terms of duration) is also an some (fractions of the) mineral reimportant
parameter since the trans- mains intact, the companion muscoformation
is, generally speaking, a vite (illite) is not affected by the
slow process. . weathering. Here the chlorite plays
3. Among the external factors, one the role of a protective «shield>> for
should certainly emphasize the role the alteration of the illite which
of geomorphology (topography, re- starts to weather later after the «passlief),
bedrock geometry (tectonic set- ing over» of practically the whole
ting), altitude, tectonic· stability chlorite.
(which favours a deeper alteration 5 .. XRD analysis remains, besides
without erosion), heterogeneity of the its real potentialities as an investigasubstratum
itself (i.e. alternating tional method for multicomposional
beds with different compositions and materials, a kind of «blind» tool becohesiveness
...), and the role played cause it produces diffractogrammes
by the biosphere (influence of the consisting of a «more or less dense
vegetation). All the text-books about forest of peaks». If the material to be
physical and chemical weathering .analysed has been prepared as
stress the influence of these «stimuli» oriented aggregates, the X-ray patin
and on the «Carving» of the land- tern is simplified, and the number of
scape. " peaks (reflections) is lessened sensi-
4. Jackson's popular sequence bly as compared to the one of a ran­
(Table 1) displays the possibility of dom powder preparation. Every scireversals
in the reaction, and impli- entist familiar with this

322 J. Thorez
___ __
the X-ray pattern of the oriented
aggregate represents (reflects), with~
in a diagrammatic way, the crystallographical
properties of an entire
population of clay particles within
the less than ·two micron fraction,
which share a common basal d­
spacing at 10 A». All the particles
give reflections situated in the same
plane; consequently the intensity of
the basal 10 A (001) peak is high, the
peak itself being fairly narrow.
Things become tougher when dealing
with randomly interstratified structures
that ordinarily display a or a plateau in the
strategic (001) zone. These features
____testify about the presence of either
disorder existing only within the clay
particle or both in the particles and
in the whole examined material. The
plateau indicates that all the radiations
have the same intensity: no simple
or separate peaks appear in the
X-ray pattern; each particle. reflects
separately on its own, the global
effect giving rise to the diffraction
band especially at the level of the d-.
spacing. In addition, the nature of the
interlayer spaces and the mode of
layer stacking also determine the
value of the parameter d. It is.actually
this d-value which is measured
when analysing the X-ray diffraction
patterns. The variations in the d
value upon classic tests (solvation
with polyalcohols ...) make it possible
to determine the mineral group to
which the interstrafied structure belongs
and particularly the nature of
the layers and interlayer spaces involved
in building-up the random interstratified
structure. With an extending
diffr:action b

Argillogenesis and the Hydrolysis index 323
(1975; 1976) have introduced specific
connotations to describe and differentiate
regular interstratified
!llinerals (which are true minerals)
and randomly interstratified structures.
The complexity of interstratified
minerals and structures makes it
difficult to arrive at a suitable but
universally used nomenclature.
Hence the necessity for the notations
to be unequivocally understood by
any user. In brief, regular mixedlayers
should be' described by a notation
where the symbols (first letters)
of the associated minerals (layers)
linked by a hyphen are put between
parentheses: i.e. a regular mixedlayer
mineral composed of layers of
mica and layers of chlorite should be
written (Mi-C); when mica layers are
predominant, the name of the interstratified
mineral should be chloritic
(Mi-C) mica. When dealing with randomly
interstratified structures,
built up i.e. by layers of illite, and interlayers
behaving as a chlorite, the
notation should comprise the symbols
(the d-spacing) of the components
such as (10-14c); the predominance
of illite layers or of chloritic
TABLE 2
Complete weathering sequences, with their transitory stages (mostly represented by the
mixed-layers) derived by the vermiculitization, smectitization, chloritization ... of parent 10
A (muscovite, biotite, illite) and 14 A (chlorite) parent clay minerals ·
MUSCOVITE, BIOTITE, ILLITE
vermiculitization (VERM):
lv, Ism and le= open illites
I -7 lv-7 10-(10-14v) -7 (10-14v) -7 (1Cl-14v)-14v-7 V
smectitization (SMEC):
I -7 Ism -7 10-(10-14sm) -7 (10-14sm) -7 (10-14smH4sm -7 Sm
chloritization (CHL):
I -7 le -7 10-(10-14c) -7 (10-14c) -7 (10-14c)-14(; -7 C 2 (secondary chlorite)
CHLORITES
vermiculi tiza tion (VERM):
C ~ C-(14c-14v) -7 (14c-14v) -7 (14c-14v)-14v -7 V
smectitization (SMEC):
C -7 Csm -7 C-(14'c-14sm) -7 (14c-14sm) -7 (14c-14sm)-14sm -7 Sm
swelling chloritization (sw-CHL):
C -7 C-(14c-14csw) ,-7 (14c-14csw) -7 (14c-14cswH4csw -7 Csw
combined processes, i.e.:
vermiculitization-smectitization (VERM + SMEC):
V -7 (14v-14sm) -7 Sml (10-14v) -7 V -7 04v-14sm) -7 Sm
secondary chloritization (CHL-2):
V -7 VAl -7 CAl I (14v-14sm) -7 (14v-14smA1) -7 VAl -7 C 2 I (10-14v) -7 (10-
14c) -7 C 2 etc.
later stages (kaolinization, amorphization) (KAOL, AMORPH):
V -7 V Al = C 2 -7 K I amorph_. -7 K I Sm -7 SmAl -7 C 2 -7 K I amorph. -7 K

324 J. Thorez
interlayers should appear in the form ~ (14c-14v)-V/14v ~ V. In other
respectively of: 10-(10-14c) and (10~ __ wrQ.s,Jh~_Qrjg~pal_for!IJ.l,!latioi1 given
14c)-14c (as appearing in Table 2). by JACKSON (1963; 1964) could be
Other possibilities and explanations developed by incorporating more
are giveri in THOREZ (1976). The sys- stages or phases which are, in fact,
tern of notation proposed here (use of the obligatory «passages» from one
parentheses and hyphens, letters or stage to the next one. The transitory
numerals) seems to the present au- stages, represented by the mixedthor
sufficiently clear so as to avoid layers, are truly relatively labile and
any ambiguity in qualifying the replace one another rather quickly in
mixed-layers, and is suitable for the the process of the weathering; they
establishment of the «Hydrolysis In- are easily defined when dealing, for
dex>>, H.I. (see further).
instance, with the weathering of the
6. In its traditional presentation, sole chlorite in a monophase com­
·Jackson's sequence lacks some imc position, but the
portant «links»: the mixed-layers ·become difficult to extract in the case
which form theoretically and also of multicompositional clay mineral
-~-----~~-:r>r;:tc!i~ally d1:1ring the weathering associations particularly because of
-processes. For instance one knows the ovedapping of reflections.
that chlorite (C) passes (quickly or The same remarks could be formuprogressively)
to vermiculite (V) with lated for complete sequences of
the transitory phase represented by a weathering incorporating different
mixed-layer chlorite-vermiculite. types of mixed-layers (Table 2).
This stage is in the form either of a The passage from a chlorite to a·
regularly interstratified mineral, (C- vermiculite via the mixed-layer (14c­
V), or of a randomly interstratified 14v) implicates several but simulstructure,
(14c-14v). Both symbols r~- taneous mechanisms. The chlorite
fer to the occurrence of chloritic particle weathers progressively, layer
layers (C, 14c) and of either vermicu- by (after) layer; all particles do not
lite layers (V) or interlayers (14v) due . necessarily undergo weathering at
to the removal of some of the origi~af .. the sai:ne speed nor with the same inhydroxydic
layer.
tensity. When analysing the material,
The sequence chlorite to- mixed- no wonder then that in the X-ray patlayer
chlorite-vermiculite to, finally, tern shows an «association>> of pea~s
vermiculite should take the following i.e. at 14 A (chlorite + vermiculite +
notation: C ~(C-V)~ V or C ~ (14c- mixed-layer, in the dry state). After
14v) ~V. If one wants to emphasize heating, this unique 14 A peak gives
better, when possible from the study rise, i.e. to a (less intense) 14 A peak
of the X-ray diffraction pattern, the (= residual but intact parent chlo­
«relay» in predominance of the corn- rite), a broad 1i A peak ( = mixedponents,
the reaction can take the layer (14c-14v)) and a 10 A peak (verform
of: C ~ C-(14c-14v) ~ (14c-14v) miculite). The vermiculitization pro-

-
Argillogenesis and the Hydrolysis Index 325
ceeds, on the other hand, according
to the «clay integron>> (Fig. 3), that is
to say at different but integrated
scales: from the layer (A) to the micron
size of the clay particles obtained
through preparation of the material
as an oriented aggregate. This integration
goes further within the collected
sample and in the fi

326 J. Thorez
METAHALL.
c ..... C- (14c-14sml ..... (14c-14sm) ..... (14c-14sm)-14sm - Sm (al
c- C (14c-14v) ..... (14c-14v)- (14c-14v)-V -V
c- (14c-14v)- v-(14v-14Sm)-Sm
4 c - (14v -14c)-V- METAHALLOYSITE
5 c- Sm - Sm AI ..... C AI (C)
6 C- (14c-14v)- V - VAI-CAI I C)
c- C 2 ..... 14A INTERGRADE- CAl-K le)
a c- C2 ..... 14A ..... Sm..... 18A INTERGRADE ..... K le)
g c- c2- 14A - v-sm-18 A - K 1e1
10 c-(14c-14vl-VTRI-(14v-14Sm)-Sm-K .Id)
11 c- (14c-14v)- VTRI ..... INTERGRADE AI - Sm Id)
12 c- (14c-14v) ..... VTRI- INTERGRADE Al .... CA! ldl
13 c-·(14c-14v) ..... VTRI ..... K /d)
Fig. 6 - Diagramme block presentation for the weathering sequences of a chlorite mineral.
(b)
le)
Id)
chlorite alteration can lead to a vermiculite
as a (provisional or definitive)
end-product, the vermiculite
being generally trioctahedral, the
associated parent illite can similarly
produce a «vermiculitic structure»,
too. This latter vermiculite can be
either dioctahedral (generated from
muscovite) or trioctahedral (if the parent
mineral is biotite). This convergence
in the weathering products of
the original parent material, chlorite
plus illite, even if the weathering is
diphased as quoted before, cannot.be
extracted from the X-ray pattern because
of the similarity of d-spacing
(cf. (001) behaviours upon identification
tests). What could be stressed is
the general weathering trend: avermiculitization,
affecting both minerals
during the degradation of the
parent minerals.
Equally, the problem may arise for
smectite. Smectitization, as a weath-

ering process, can induce the degradation
.of a silicate (including
phyllosilicates and clay minerals
such as illite, biotite, chlorite) and
the production of a smectite (cf. degradation
smectite). However, the
smectite can be generated after an
entirely opposite process neoformation.
Both genetic. species may coexist
in the weathering products and
the XRD analysis cannot differentiate
them.
8. The composition of the mixedlayers
points to the geochemical processes
which are acting during the
weathering. These geochemical processes
are identified as vermiculitization
(VERM), smectitization (SMEC),
secondary chloritization (CHL), and
kaolinitization (KAOL) when the
mixed-layers show in their structur:e
(random mixed-layers) distended interlayers
which behave like respectively
a vermiculite (14v), a smectite
Cl4sm), a chlorite (14c).
For instance a parent chlorite
could weather towards a vermiculite,
smectite or swelling chlorite (14c 5 w)
state (or_ end-product) according to
the following weathering sequences:
C---+ C-(14c-14v)---+ C-(14c-14v)-14v---+
Cl4c-14v) ---+ Cl4c-14v)-14v ---+ V (=
VERMiculitization) ·
C ---+ C-04c-14sm) ---+ C-(14c-14sm)-
14sm ---+ Cl4c-14sm) ---+ Cl4c-14sm)-
14sm---+ Sm (= SMECtitization)
C ---+ C-(14c-14csw) ---+ (14c-14csw) ---+
Cl4c-14csw)-14csw ---+ Csw (swelling
chlorite)
Vermiculi tiza tion, smecti tiza tion,
Argillogenesis and the Hydrolysis Index 327
chloritization processes, expressed
within transitory mixed-layers, also
characterize the weathering of 10 A
material (muscovite, biotite, illite) as
illustrated in Table 2.
Moreover, combined but successive
processes exist whether caused
by a change in the weathering conditions
or by the «normal» paths: i.e. a
chlorite could become transformed
by degradation into a vermiculite,
the latter stage becoming further degraded
and reaching a smectite stage.
Briefly expressed, the latter combination
will take the form of: C ---+ Cl4c-
14v) ~ V ---+ Cl4v-14 5 m) ---+ Sm (=
VERM + SMEC).
Another way to present these
different geochemical-crystallochem-
'-ical pathways is with a diagramme
block (Fig. 5) where two «corners>>
are occupied by the parent minerals,
illites sensu lata, and chlorite. Lateral
and diagonal «pannels» support the
transitory (mixed-layers) products,
with the last two «corners» devoted
to vermiculite (V) and smectite (Sm)
as end-products. However, further
transformation can lead to either Alhydroxylation
of the vermiculite and
smectite (cf. external pannels) or to
swelling chlorite (C 5 w), and finally to
kaolinite. In reality, all these sequences
in their actual presentation
(Fig. 5) appear more complex in the
natural conditions. A global review
related to the different pathways and
by-products of the weathering of both
10 A and 14 A clay minerals as well as
that of non-clay minenils (feldspars,

--~~------~-~---~
TABLE 3
Schematic reconstruction of the various transformation pathways with their geothemical implications (vermiculitization, smectitization, ... )
for silicates ! -
I
Bio
c
ILLITE-MUSCOVITE
~ VERM---? CHL2
~ SMEC ---? KAOL
~ CHL2
~ SMEC ---? CHL2
~ KAOL
t
KAOL
- CHL2
BIOTITE
SMEC ---? KAOL
~ VERM---? KAOL
~ CHL ---? SMEC---? KAOL
~ ~ VERM---? KAOL
- ~ KAOL ~ SMEC ---? KAOL
t
KAOL
ILL
CHLORITES
r VERM---? CHL2 ---? SMEC
~ KAOL
SMEC---? KAOL
t
SMEC ---? CHL2
CHL2 ---? KAOL
SYMBOLS
SMEC = Smectitization
VERM = Vermiculitization
~ CHL2
~ CHL2 ---? KAOL
CHL
CHL2
F
FELDSPARS
r SER i---? SMEC---? KAOL
~ ~ CHL2 ---? KAOL ---? GIBBSITE
VERM---? SMEC ---? KAOL
""'~ ~ CHL2 ---? KAOL
~ CHL2 ---? KAOL
KAOL
CHL ---? SMEC ---? KAOL
~
VERM---? SMEC---? KAOL
SMEC---? KAOL
KAOL ---? AMORPHOUS
AMORPHOUS ---? KAOL
PYROXENES-AMPHIBOLES
PYR ---? KAOL + GOETHITE ..
~ AMPHIB ---? CHL ---? VERM---? SMEC---? KAqL
SEQUENCE---?
""- ' SMEC :1
~ ~ r
SMEC ---? AMORPHOUS ---? KAQL
Geochemical pathways for degradation,
aggradation and neoformation are represented
by simple clay minerals and/or mixed-layers
Chloritization
Secondary chloritization
KAOL = Kaolinitization
ILL = Illitization
"' N
00
:-...
~
~
N

pyroxenes ...) ('fHOREZ, in preparation)
demonstrates a more intricate
pattern in the weathering sequences,
with either stops or combined sequences.
Figure 6 exemplifies for instance
the behaviour of chlorite (C)
alone during weathering with at least .
13 different sequences. Table 3 provides
a synthetic approach for all the
weathering sequences regarding
illite-muscovite, biotite, chlorites,
Argillogenesis and the Hydrolysis fiib 329
"
TABLE 4
feldspars, pyroxenes-amphiboles.
The representative sequences are
illustrated here by referring only to
the geochemical pathway, arrows
providing the direction of the process.
In this way the high variability
of weathering sequences for each
parent mineral can be demonstrated;
each stage (i.e. VERM of illite(I)) incorporates
in reality a series of intermediates:
I__,. (10-14v) __,.V. Illustration
within separate diagramme
blocks is foreseen (THOREZ, in preparation).
It is noteworthy that all the sequences
reach kaolinization at the end
of the process, provided that the
weathering is continuous.
The weathering index
JACKSON and eo-workers (1948)
were well aware of the role of clay
minerals in the weathering processes
in soils. They proposed a graphical
method to trace the course of the
weathering (their «weathering sequence>>),
and to rank the weathering
(in intensity) and the associated
. weathering products (clay and non-
Weathering indexes of clay~size minerals in soils and sedimentary deposits (JACKSON,
. - 1948)
Weathering
Index and Symbol
Clay-size minerals
1 Gyp Gypsum (also halite, Na-sulphate, etc.)
2 Clt Calcite (also dolomite, aragonite, apatite, etc.)
3 Horn Hornblende (also olivine, pyroxene, analcite ... )
4 Biot Biotite (also glauconite, mafic chlorite, antigorite, nontronite, etc.)
5 Alb Albite (also plagioclases, microcline, volcanic glass, etc.)
6 Otz Quartz. (also cristobalite, tridymite, etc.)
7 Mi-d 1M~dioctahedral micas (also muscovite and 10 A zones of sericite ... )
8 Verm Vermiculite (also collapsible14 A interstratified zones)
9 Mont Montmorillonite (also beidellite, etc.)
9 Al-Chl Pedogenic dioctahedral chlorite (including interstratified 2:2 zones)
10 Allo Allophane (sesquioxidic, halloysitic, etc.)
11 Gibb Gibbsite (also boehmite, etc.)
12 Hem Hematite (also goethite, limonite, lepidocrocite, magnetite ... )
13 Ana Anatase (also rutile, ilmenite, leucoxene, zircon, corundum, etc.)

330 J. Thorez
clay minerals) in terms of successive
appearances and relative resistances ..
Their work led to a form of indexing
supported by a series of 13 successive
stages (Table 4).
By presenting this series of stages,
JACKSON et al. (1948) adopted the
views that: i) a «colloidal» size mineral
may in some cases be a parent
material of successive

Argillogenesis andthe Hydrolysis Index 331
besides the «routine» three tests
(natural-air dried, glycolated, and
heated preparation), in order to reach
a good discrimination among the different
clay components (some of these
sharing common reflections difficult
to separate if only the routine investigation
is completed).
After having established the real
composition of the clay phase, a
quantitative evaluation of their rela-
tive abundance must be reached
whatever the method (or better to
say: the lack of method). The essential
point is to work out the quantification
always following the same
whether the abundance is
translated as percentage or not.
The next step is to have appropriate
indexing for the stages presented
in Table 2. After several tests the indexation
was obtained as reported in
TABLE 5
Stages and stage numbers (between parentheses) in the complete weathering sequences for
· 10 A (illite sensu Jato) and chlorites
I~ lv ~ 10-(10-14v) ~ 10-(10-14v) ~ (10-14v) ~ (10-14v)-14v ~V
(1) (1.25) (1.5) (1.75) (2) (2.5) (3)
I ~ Ism ---'-7 10-(1 0-14sm) ~ 10-(1 0-14sm) ~ (1 0-14sm)
(1) (1.25) (1.5) (1.75) (2)
~ (10-14sm)-14sm ~ (10-14sm)-14sm'~ Sm
(3) (4) (5)
I~ le~· 10-(10-14c) ~ 10-(10-14c) ~ (10-14c) ~ (10-14c)-14c ~ C 2
(1) (1.25) (1.5) (2) (4) (4.5) (5)
C ~ C-(14c-14v) ~ (14c-14v) ~ (14c-14v)-14v ~V
(1) / ·(1.5) (2) (2.5) (3)
C ~ Csm ~ C-(14c-14srn) ~ (14c-14sm) ~ (14c-14sm)-14sm ~ Sm
(1) (1.25) (1.5) (2) (2.5) (5)
C ~ C-(14c-14c 5 w) ~ (14c-14csw) ~ (14c-14c 5 w)-14csw ~ C 5 w
(1) (1.5) (2) (3) (4)
... V~ VA 1 __,. C 2 __,. K ~ Gibbsite ~Amorphous
(3) (4.5) (5) (7) (8) (9)
... V~ (14v-14sm) ~ Sm ~ SmAI (= Al 17 A) ~ K ~ Gibb. ~ Amorph.
(3) (4) (5) (6) (7) (8) (9)

--
-- ---·------------- - - --~-----
332 I. Thorez
Table 5 (cf. numbers between parentheses
placed below each stage) .. -
The calculation of the H.I. for a
multicompositional phase (as obtained
from the XRD analysis) is
conducted as follows:
a - multiply the relative abundance
(A) of each identified mineral (simple
clay mineral or mixed-layer) by its
representative stage number (taken
from a specific sequence in Table 5),
b - sum up all the products (A X
S.N.) (S.N. for «Stage number>>),
c - identify the residual parent clay
mineral if (still) present (illite, chlorite,
talc), these having a S.N. of (1)
systematically,
- - . - -- --- -- --
d - multiply the A of the parent
mineral(s) by the S.N. (1),
e- divide the sum obtained in (b) by
the one obtained in (d); the result is
the H.I. of the analysed sample.
An example could better illustrate
the method. Suppose a clay composition
with Illite (I) (Abundance, A =
3.25) I (10-14v) (A = 1) I (10-14c) (A =
1.25) I Vermiculite (V) (A = 1.8) I
Smectite (Sm) (A = 1.2) I Kaolinite
(K) (A = 1.5). The H.I. calculation as
indicated above will be completed
step by step:
a- I = 3.25 X 1 I (10-14v) = 1 X 2 I
(1 0-14c) = 1.25 X 4 I V = 1.8 x 3 I Sm
= 1.2 X 5 I K = 1.5 X 7
b - sum of all the products (A x
S.N.) = 32.15
c + d - illi te (I) is the only (residual)
parent mineral: 3.25 x 1 = 3.25
e- 32.15 I 3.25 = 9.89 = H.I.
Some applications of the Hydrolysis
.. l.nd~~~A:o_cLiJs,_r~laJiQn with paleoclimatic
reconstruction
The various weathering sequences
(Tables 2 and 5) and their corresponding
geochemical pathways (Fig.
5) implicitly bear a kind of paleoclimatic
signature at both the level of
the clay minerals which appear in
those sequences, and at that of the
kind of sequence, whether these are
fully developed or not. Such a signature
results in particular. from the
direct influence and the cumulative
effects of i) the global temperature
(cold, temperate or warm), ii) the internal
and/or surficial drainage (intensity,
speed, regularity and duration)
in the weathering crust, and iii)
the relative humidity (dry, wet or
dry-wet) conditions to which the parent
rocks and minerals were submitted
during pedogenesis or deuteric alteration.
However, as discussed by
SINGER (1980) and THOREZ (in
preparation), only the more agressive
conditions will leave their crystallochemical
and geochemical «finger
prints» .within the final clay mineral
associations. Indeed, any temporary
or definitive reversal of the climatic
conditions, yielding milder character,
will usually not be expressed
within the clay assemblage, exception
in the case of polycyclism (i.e. a
later calcrete developement, with a
smectitic or palygorskite clay mineral
occurrence, surimposed on a
kaolinite-bearing latosoil). A synthetic
connection between the kinds and
trends of weathering sequences, and

Argillogenesis and the Hydrolysis l~dex
333
OJJJ]] STRONG RAINFALL . AND DRAINAGE
- WEAK RAINFALL AND DRAINAGE
I = ILL1TE
BIO : BJOT/TE
V = VERMICULITE
Sm = SMECTITE
\ J: MIXED LAYE !\
PARENT MINERAL
SEQUENCES OF TRANSFORMATION
~
I- (10~14V)- V VERM
C- (14C-14V)- V V.ERM
WET-DRY
I - (10-14V)- V VERM
......... (10-14C) CHL 2
810- (10-14C) .CHL 2
C - (14C-14V)-V VERM
~
I _('10_14Sm)- Sm SMEC
810- (10·14C)- C2 CHL2
C - (14C-14Sml-Sm SMEC
DRY-(DRY-WET)
I - (10-14 V) I {10-14Sm)
BIO- (10-14V)
C - (14C-14Sm)
~
C - (14C-14Sm)
I - Io(open)
810- (10•14Vl
VERM/SMEC
VERM
SMEC
SMEC
VERM
SMEC : SMECTITIZATION
VERM : VERMICULITIZATION
CHL2 : SECONDARY
CLHORITIZATION
GEOCHEMICAL
;:·(1(:.R;;~~i14V·14Sml- ·sm VERM- SM);,EC;---:,::PA::.;TH::,:W::;A::_Y --~
I- (10-14$m)- Sm SMEC'
C- (14C-14V)- V-(14V-14Sm)-Sm VERM-SMEC
Fig. 7 - Relation between sequences of transformation and paleoclimatic ~onditions.
TABLE 6
Stage numbers (S.N.) and corresponding'-clay minerals species (simple clay minerals and
mixed-layers) grouping
S.N.
Clay Mineral Species
1 Parent minerals: Muscovite, Illite, Biotite; Chlorite; Talc;
Sericite, ...
1.25 Illite with large peak, CM
1:50 Open Illites (Iv, le, Ism); 10-(10-14c); 10-(10-14v)
1.75 10-(1 0-14v ); 10-(1 0-14sm)
2 10-(10-14v)-14v I (10-14v); C-(14c14v)-V I (14c14v),
(14c-14M); (14c-14sw); (10-14c)
2.50 (10)4v)-l4v; (14c-14v)-V; Cl4c-14M)-14M, Csw
3 V; 10-(10-14sm)-14sm I (10-14sm)
4 (10-14sm)-14sm; (10-14c)-14c
4.50 VAI; (10-14c)-14c
5 Sm; C 2 ; (10-14sm)-14sm
6 AL17 V = Vermiculite
7 K Sm = Smectites
8 Gibbsite K = Kaolinites
9 Allophane, Amorphous I = or

i
334 J. Thorez
the inferred climatic conditions (S.N.) for the calculation of the Hy­
(drainage, humidity) is illustratedin __ dr2lysj_s_IJ:!_qex_f

Argillogenesis and the Hydrolysis Index 335
occurrence of the existing by- . and
end-products generated during the
weathering of the parent minerals,
and the stage(s) reached by these during
the weathering. Both data related
to the H.I. and to the stages reached
by the clay minerals during the
weathering can be further graphically
presented as in Fig. 8.
The detailed, critical and limited
application of the H.I. and of the
paleoclimatic parameters will be presented
in another paper (THOREZ, in
preparation). However, to better
emphasize here the usefulness of the
H.I., particularly in tracing back the
possible paleoclimates «printed» in
the clay assemblages, two examples
will be briefly provided.
The first example refers to the Upper
Pleistocene sequence of eoli:~mites
and paleosoils at San Giuseppe,
northern Sardinia (Italy) (OZER &
THOREZ, 1980) (Fig. 9). The vertical
evolution of the H.I. is provided by
the study of the clay associations
found in the various layers (eolianites
and paleosoils) and from which the
inferred paleoclimatic parameters
are extracted in terms of cold,
temperate or warm on the one hand,
and of dry, dry-wet or wet, on the
other hand. If the climatic signature
appears correct for the paleosoils,
some discrepancies, however, mark
both the nature of the clay mineral
associations (cement) and the reconstructed
paleoclimate for eolianites.
For instance, one knows that the
«normal» eolianites are built up during
dry and rather cold (cooler)
period at least during the last Inter-
Feldspar
contents
Relative proportions Hydrolysis index Climatic curve based on the clay analysis Based on the sedlments
ol clay minerals C;!______£,1'1 TL-.,!.d. WL-..!!.h

336 J. Thorez
glacial. Here, one can observe that
these cold and dry conditions are not
met from the study of the clay coin-­
position; the latter better points to
temperate and humid conditions!
These discrepancies are leveled if one
considers that the clay content of the
eolianites is composed, in part, by a
recycled material. The latter is removed
from the upper horizons of the
soils through erosion produced by the-- ·
wind, and becomes somewhat mixed
with fresh parent mineral coming
from another source. As a consequence
the global «picture» or «signature»
of the clay association may
be artificial at the point of view of
climatic interpretation and needs, for
a corrent reconstruction, an interdisciplinary
approach (stratigraphy,
-geomorphofOgy; sedimentology, clay
mineralogy).
The second example is that of a
multidisciplinary study carried out
on the Holocene to Recent sediments _
of the Taranto Gulf, southern Italy
(BELFIORE et al., 1982; PESCA­
TORE et al., 1985). From the palynology,
micropaleontology (Foraminifera)
and clay mineralogy, a new
integration of climatic data has been
set up and is presented in Fig. 10.
Good parallels can be observed between
the paleoclimatic trends
shown by the pollens and Forami-'
nifera (the first being generated- on -
INFERRED
PALAEO·
(14 0 -14v) CORE POLLEN{P) FORAM{F) CLIMATES
+ -
+ +
0 -
+ 0
- -
+ -
0 +-
+ +
0 0
0 0
0 0
+ +
0 -
+' 0
+ +
z
0
;:::
Cii
0
0.
0.
~
0
"' 0
..J
;::: "'
a:
~
+ +
+ -
0 -
"' 0
+
Fig. 10 - Paleoclimatic reconstruction (based on the study of pollen, Foraminifera and clay
minerals) of the Holocene to Recent sequence (cores 78, 137 and 210 organized in the stratigraphic
position) in the Taranto Gulf, southern Italy (BELFIORE et al., 1982, modified).

Argillogenesis and the Hydrolysis index 337
the neighbouring continent, and the
second living in the ocean waters),
and by the clay mineral associations
(from which theH.I.,andsomeparameters
such as the 17 All 0 A peak
ratio, the amounts of smectite, vermiculite
and (14c-14v) are here presented).
The discrepancies in the
climatic data provided by these two
separate criteria are marked in the
last column at the right hand of Fig.
.10; they can be explained by taking
into account, for instance, some dephasing
in the between the climatic
changes occurring on the continent
and the cooling or warming of the sea
water; or some packets of sediments
have been removed by density currents
and by slumping, the mechanical
process intervening during another
climatic environment as check~d by
the study of the -Foraminifera ~lone.
"
Conclusion
The transformation of silicates
into clays and clay minerals is not a
jerking process but a continuous one
comprising several stages; these are,
in. tu_rn, placed in succession and relays,
and take several forms governed
simultaneously by various external
and internal «Stimuli». Parent clay
minerals such as illite sensu lata and
ch.lorite are possibly residual products
of former non-clay minerals
(feldspars, pyroxenes, amphiboles,
olivine ... ) but act as parents anyway
when the weathering proceeds further
and induce the transformation
(degradation) in several by- and endproducts
(mixed-layers, vermiculite,
smectite, kaolinite). Different sequences,
thus, exist for illi tes and chlorites,
which deliver various kinds of
clay products having the «mark» of
the main geochemical process acting
during the transformation (vermiculitization,
smectitization ... ). The
different weathering sequences have
been reconstructed step-by-step and
their successive stages have been
numbered (stage number, S.N.). Even
if the actual clay composition no longer
presents together all the transitory
stages, these are not purely
theoretical and have once existed in
the process but have disappeared in
favour of later (better stabilized)
ones. These, in turn, may be detected
within the multicompositional clay
assemblage submitted to the XRD
analysis. After having completed a
detailed XRD analysis, and all the
clay components «quantified», it is
possible to reach a kind of «hydrolysis
influence>> within the actual composition.
The method is indicated
here after having been tested for
several examples to be published later.
The proposed H.l. (Hydrolysis Index)
intends to gather easily and
quickly a measurement of the final
but global effect of the weathering.
The appreciation of the H.I. must
take into consideration the geological
and pedological «background». The
problem of possible heritage of
.. already weathered phases can be
taken into account, too. XRD analysis
remains consequently a complementary
tool in the investigation
supported by other methods of study.
The H.I. proposed may complete the
study of the argillogenesis.

338 J. Thorez
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MEUNIER A., VELDE B., 1979. Weathering mineral facies in altered granites: the importance of local
small scale equilibria. Mineral. Mag. 43, 261-268.
MILLOT G., 1967. Les deux grandes voies de I' evolution des silicates a la surface de l'ecorce terrestre.
Rev. Questions Se. 138 (3), 335-357.
OzER A., THOREZ J., 1980. Les depots du Pleistocene Superieur de San Giuseppe (Sardaigne Septentrionale).
Pp. 255-270, in: Actes du Coll. Niveaux Marins et Tectonique Quaternaires clans l'Aire
Mediterraneenne, Paris, C.N.R.S., Univ. Paris II.
PEDRO G., 1976. Sols argileux et argiles. Elements generaux en vue d'une introduction a leur etude.
Science du Sol 2, 69-84. -- . ·
PESCATORE T., THOREZ J., SENATORE M.R., ABDEL GADIR S., MONTCHARMONT M., DAMBLON F.,
STREEL M., 1985. Clay Mineralogical Trends in the Holocene Sediments of the Gulf of Taranto,
Southern Italy. These Proceedings, Abstract. ·
SINGER A., 1980. The paleoclimatic interpretation of Clay Minerals in Soils and Weathering Profiles·.
Earth Se. Reviews 15, 303-326.
Suoo T., HAYASHI H., SHIMODA S., 1962:~Mineralogical Problems of Intermediate Clay Minerals. Pp.
378-392, in: Proc. Clays and Clay Minerals, 9th Nat. Conf. 1960, Lafayette-Indiana (E. Ingerson,
editor).
TARDY Y., 1969. Geochimie des alterations. Etude des arenes et des eau de quelques massifs cristallins
d'Europe et d'Afrique. Mem. Serv. Carte.geol. Als. Lorr. 31, 199 p.
THOREZ J., VAN LEeKwiJeK W., 1967. Les mineraux argileux et leurs alterations dans le Namurien
inferieur de Belgique. Ann. Soc. Geol. Belgique 90, 329-377.
THOREZ J ., 197 5. Phyllosilicates and Clay Minerals. A Laboratory Handbook for their X-Ray Diffraction
Analysis. G. Lelotte, Dison, Belgium.
THOREZ J., 1976. Practical Identification of Clay Minerals. G. Lelotte, Dison, Belgium.
THOREZ J., 1982. Claygeology, a paleoclimatic tool for Quaternary series. Striolae, IN QU A Newsletter,
1, 4, 10-16.
THOREZ J., 1985. Qualitative Clay Mineral Analysis biased by Sample Treatments. Pp. 383-389, in:
Proc. 5th Meeting European Clay Groups 1983, Prague (J. Konta, editor), Univerzita Karlova
Praha. ,
THOREZ J., 1987. Physico-chemical Studies of the Structures of the Solid Supports: X-ray Studies.
Chapter.b 4 , in: Preparative Chemistry Using Supported Reagents (P. Laszlo, editor) Academic
Press, New York (in press).
VELDE B., 1985. Clay Minerals. A Physico-Chemical Explanation of their Occurrence. Developments in
Sedimentology 40, Elsevier.

Abstracts
339'
Geochemical Aspects Related to Oxidation Phenomena
along some Jointing in Clayey Formations
F. ANTONIOLI, G. LENZI
Labonitorio ai G·eologia ambientale, PAS-SCAMB, ENEA-CASACCIA, Via Anguillarese Km 1+300, 00060 Santa
Maria di Galeria, Italia
The geochemical behaviour of clays outcropping in a quarry to the North of
Rome, near Monterotondo, is studied, where the cracking phenomenon is
very evident and where many yellowish or 'reddish oxidation strips are
present and very clear upon both sides of the fissures and which .stand out
against the remaning bluish-gray geologic formation.
Many samples were taken, at different distances around thoseJissures and
marked as follows:
1) very thin gray part corresponding to the central zone of fissure, sometimes
very rich in white or whitish salts;
2) oxidized yellowish part (or strip), sometimes with different intensity
shades (oxidized clay);
3) grey-bluish zone far from the fissure (reduced zone).
The following different an~lyses were carried out on the samples:
a) X-ray diffractometry on and clay fraction;
b) particle size analyses on three particular samples;
c) chemical analyses by X-ray fluorescence on the yellowish oxidized and
graysh parts, and by conventional methods (to determine ·the FeO and
· Fe 2 0 3 ); thermogra·x_imetry to determine the water and carbonate content;
analysis of salts present in the interstitial waters of clay samples;
d) physico-chemical analysis on some representative samples to determine
the properties of Cs and Sr under well defined conditions.
The X-ray mineralogical analyses showed the following: presence of quartz,
feldspars, calcite, dolomite and clay minerals (smectite, about 35%; illite,
about 50%; chlorite, about S%;.kaolinite, about 5%; vermiculite and of illitemontmorillonite
mixed layers) traces; their amount is practically constant
in every part of the sediment; zeolite (laumontite ?) and gypsum (central zone
of the fissure) away from the graysh parts of the geological formation.
Chemical analyses by X-ray fluorescence reveal a composition quite constant
for the main elements, in both the oxidized and reduced zones; whereas they
show a noticeable diversity for trace elements such as Cl, S, and Sr; that is to
say these elements in the oxidized zones are in smaller amounts than in the
reduced zones.
The conventional chemical analyses to determine the FeO and Fe 20 3 show,
in the gray samples, Fe2+ about 3.4% and Fe 3 + about 1%; on the contrary in
the yellowish ones Fe2+ is about 0.8 to 0.9 and Fe 3 + about 5.3%.
The analysis of the salts included in the interstitial waters showed that Na,
Mg, K, Zn and Co sulfate are present, as well as Na and K chlorides (and
phosphate traces) also supported by X-ray fluorescence analysis.
Finally, the physico-cheihical analyses carried out on the Cs and Sr
properties, using tap water with about 10 French degrees of hardness,
in the yellowish and graysh samples, by the
study, showed that the Cs and Sr takes place preferentially in the
oxidized samples, rather than in the reduced ones and all this, contrary to
all our expectation, because of the ratio of Kd(oxid.)/Kd(red.) about 2.1 for Cs;
and Kd(oxid.)/Kd(red.) = 1.7 for Sr.
In conclusion, along the yellowish oxidation strips existing in the fissures of
the clayey geologic formation outcropping near Monterotondo the Cs and Sr
sorption·is higher than in the reduced graysh zones, original of the sedimen-

-
340 Abstracts
tary rock. It is hypothesized that this phenomenon is not a result of diversity
in mineralogical composition (which was found to be more less constant)
but rather the result of a diversity~of··geochemieal-composition due to the
leaching to which the original clayey material had undergone and in which
clearly a physico·chemical equilibrium is re-established when Cs and Sr are
artificially added to the argillaceous sediment.
Interstratified Minerals in Spanish Sedimentary Facies:
Lower Part of the Keuper in the Siguenza Area
and the Tajo Basin, Central Spain
M. DOVAL 1 , M. RODA~ 1 , A. RUIZ AMIU, F. ARAGON'
1
Departamento de Cristalografia y Mineralogia, Facultad de Geologia, Universidad Complutense, 28040 Madrid,
-~-~---------Espai\a _____ ~:-c------ _
2
Instituto de Quimica Inorganica «Elhuyar>>, C.S.I.C., Serrano 113, 28006 Madrid, Espai\a
This paper deals with two cases of interstratified minerals from two quite
different geological series. The first one located in the Siguenza area (Guadalajara)
corresponds to the lower part of the Keuper. It is comprised within a
38 m thick unit of alternating silts and clays, interbedded with gypsum.
Mineralogically they are composed of quartz, gypsum and phyllosilicates,
mostly illite and chlorite. The interstratified mineral characterized here
(chlorite-vermiculite) is the main mineral found in the < 2 J.!m fraction of
some samples.
The second case appears in clays interlayered in the Miocene arkoses of the
Tajo basin. Mineralogically the clay levels are composed of quartz and
phyllosilicates, in which illite is dominating, although smectite and sepiolite
also are often found. A mineral whose behaviour under X-ray diffraction
differs from that of a smectite, being closer to an interstratified chloritesmectite,
appears related to the sepiolite.
In both cases the interstratification has been studied by treating the oriented
aggregates of the< 2 J.!m fraction with amines.
The mixing function has been calculated (I= I F 1 1 2 ); this factor defines
the interstratification and has been calculated according to the Fourier
method.
- First case:
the mixing function is applied to the systems: chlorite-(vermiculite + butylamine),
chlorite (vermiculite + pentylamine), chlorite-(vermiculite + heptylamine)
and chlorite-(vermiculite + octylamine).
The results obtained are given in the Table.
- Second case:
the characterization of this material's interstratification is difficult due to its
low crystallinity. The following pretreatments were applied: ·
1) sample homoionization with Na+ and K+;
2) solvatation with ethylene glycol for both cases;
3) thermal treatment at different temperatures;
4) infrared and chemical analyses.

Abstracts 341
On the basis of the results obtained the chlorite-smectite was chosen as an
interstratification model, and the interlayered compounds formed with the
amines were subsequently studied.
Theoretical (T) and experimental (Exp) data obtained from the interlamellar sorption of aliphatic
amines
mo PA = 0.1 PAA = 1
2/10 PA = 0.1 PAA = 1
Butyl14-14.84 Pentyl14-25 Heptyl14-28.72 Octyl14-31.63 Heating 550°C
T 1/10T2/10 Exp T 1/10 T2/10 Exp T 1/10 T2/10 Exp T 1/10 T2/10 Exp Tl/10 T2/10 Exp
20.25 20 20.85 24.61 24.61 25.2 28.57 28.57 - 32 31.37 - 22.80 31.25 23.05
14.81 14.81 14.89 19.51 19.28 19.61 14.28 14.28 14.28 10.52 10.52 10.47 14.08 13.88 14.01
8.60 8.55 8.66 12.40 12:40 12.60 9.52 9.52 7.92 7.92 7.90 9.90 10.00 9.88
5.44 - 10.88 10.88 10.60 7.20 7.14 7.13 6.35 6.32 6.36 5.02 5.00 5.03
4.93 4.93 4.84 8.25 8.24 5.75 5.75 5.74 5.26 5.27 5.26 4.36 4.34 4.42
3.98 6.7 6.9 4.79 4.79 4.74 4.52 4.51 4.54 3.34 3.35 3.34
3.70 3.70 3.68 5.78 5.78 5.71 4.10 4.10 3.51 3.51 3.55 2.81 2.81 2.79
3.56 3.53 4.93 4.93 4.85 3.58 3.58 3.55 3.16 3.16 2.50 2.50
3.49 3.25 3.53 3.54 3.54 3.18 3.18 3.20 2.87 2.87 2.85
3.13 3.06 3.08 3.08 3.06 2.86 2.86 2.86 2.63 2.63 2.59
2.96 2.96 2.95 2.74 2.74 2.61 2.43 . 2.43 2.42
2.58 2.79 2.82 2.46 2.46 2.49 2.39 2.39 2.50 2.11 2.11 2.12
2.47 2.47 2.49 2.00 2.00 2.00 2.00 2.20
1.90 1.90 1.90 2.05 2.05 2.00
Note: As PA = 0.1, PB = 0.9, therefore the ratio verrniculite/chloriteis 9il.
The PAA value (1) implies, for this interstratification, a strong tendency towards segregation.
The Uppermost Miocene of the Granada Basin,
SE Spain: Mineralogy
M. ORTEGA HUERTAS 1·3 , J. RODRIGUEZ FERNANDEZ 2 ·3 , I. PALOMO
DELGAD0 1·3 , J. FERNANDEZ MARTINEZ 2·3, P. FENOLL HACH-ALI 1·3,
A.C. LOPEZ GARRID0 2
1 Departamento de Crjstalografia y Mineralogia, Facultad de Ciencias, Universidad de Granada, 18002 Granada,
Espaii.a
2 Departamento de Estratigrafia, Facultad de Ciencias, Universidad de Granada, 18002 Granada, Espaii.a
3 Departamento de Investigaciones Geol6gicas, C.S.I.C., Facultad de Ciencias, Universidad de Granada, 18002
Granada,Espaii.a
'
The Uppermost Miocene of the Granada Depression is represented by several
detrital Formations corresponding to a fluvial environment s.l. interbedded
with another one of lacustrine environment, where gypsum and carbonate
materials make up the predominant lithology.
This Miocene is well represented in two stratigraphical sections wich are
studied iri this work. One of these is situated in the southern margin (

342 Abstracts
del Rey>>) and the other one in the northern margin (, ).
The vertebrate remains give an Upper Turolien age for these materials.

Abstracts 343
Neogene Sedimentation in the Granada Basin, SE Spain
M. OR'fEGA HUERTAS 2·3 , J. RODRIGUEZ FERNANDEZI.2, J. RODRIGUEZ
GORDILL0 2·3, P. FENOLL HACH-ALI 2·3
1
Departamento de Estratigrafia, Facultad de Ciencias, Universidad de Granada, 18002 Granada, Espana
2
Departamento de Cristalcigrafia y Mineralogia, Facultad de Ciencias, Universidad de Granada, 18002 Granada,
Espana
3
Departamento de Investigaciones Geol6gicas, C.S.I.C., Facultad de Ciencias, Universidad de Granada, 18002
Granada, Espana
Some outcrops of Neogene and Quaternary materials (Lower Miocene to
Upper Pleistocene) are found in the Granada Depression. In the Eastern area
several sequences were established, in order to analyse their stratigraphy,
sedimentology and mineralogy, and the following Units differentiated:
La Peza Formation (Rodriguez Fernandez, 1982). Made up of materials belonging
to the upper part of the Middle Miocene which were deposited before
the Granada Depression was formed. An initial member has been identified
in this Formation, containing marls and greyish sands with fibrous gypsum
and levels of calcite with chert nodules, Gastropoda and Charophyta
remains. Their mineralogy consists of calcite (10-75%), dolomite (0-20%),
quartz (20%), feldspars (5%), gypsum (0-10%), muscovite (20%), paragonite
(< 5%), chlorite (< 5%) and smectites (10%).
These results suggest a lacustrine environment with sporadic terrigenous
contributions more abundant at the top where they constitute a second,
clearly detrital member.
The compressive post-Serravallian stage folds the materials of this Formation
and gives rise to s•everal new depressions, one of them being the Granada
Depression; "
Quentar Formation (Rodriguez Fernandez, 1982). During the Lower Tortonian
a bioclastic sedimentation belonging to a carbonate platform took place
in the Granada Depression. It is made up ofbioclastic calcarenites which, in
the middle of the basin, pass to facies of greyish lutites with berithic and
planonic foraminifera, Dentalium and Amusium - like bivalves.
This Formation is characterized by the presence of calcite (10-90%), dolomite
(0-15%), quartz (10-55%), feldspars (0-15%), muscovite (5-15%), paragonite
(< 5%), chlorite (< 5%), and smectites (10%).
Generally speaking, the carbonate percentage decreases and that of the
inl).erited and neoformed phyllosilicates increases at the top of the sequence,
i.e. the Formation develops into a more open marine environment;
Dudar Formation (Rodriguez Fernandez, 1982). During the Upper Tortonian
the materials belonging to this Formation were deposited over the Quentar
Formation. They are composed of lutites interbedded with conglomerate
levels. These conglomerates are more abundant and thicker at the top. The
lutitelevels con~ain marine fauna (bivalves, gastropods, benthic foraminifer!i).
Their mineralogy is as follows: calcite (5-10%), dolomite (10-20%), quartz
(20-30%), feldspars (15-20%), muscovite (20%), paragonite (< 5%), chlorite
(< 10%), smectites (5%). The open marine character, first observed at the top
of the Quentar Formation, continues in this Formation; .
Block Formation (Von Drasche, 1879). The Pinos Genii Formation (Block
Formation s.l.) is discordantly deposited over Quentar and Dudar Formations
described above, or over the Betic Substratum. It is of a conglomeratic
character and is very thick in some zones.
The mineralogy of the fine detrital levels and that of the conglomerate
matrix is: calcite (5-40%), dolomite(< 10%), quartz (15-45%), feldspars (5%),
muscovite (10-30%), paragonite (5%), chlorite (5-20%), and smectites (5-
30%).
The percentage of kaolinite is very variable, but always less than 10%.

344 Abstracts
The mineral components are inherited and correspond, in general,. to a high
energy system of alluvial fans whose component materials had drained from
the Sierra Nevada reliefs. - ~- -·-----~ ..
As to the origin of the constituents of these Formations we have used mineral,
crystallocherpical data and trace element analysis to demonstrate that
they derive mainly from rocks belonging to the «Nevado-Fihibride Complex».
This work forms part of the Project "El borde mediterraneo espaiiol. Evoluci6n del
or6geno betico y geodinamica de !as cuencas ne6genas". (C.S.I.C.- C.A.I.C.Y.T.).
Rodriguez Fernandez J., 1982. El Mioceno del Sector Central de !as Cordilleras Beticas. Ph. D.
Thesis, University of Granada.
Von Drasche R., 1879. Geologische Skieze des Hochgebirsgsteiles der Sierra Nevada in Spanien.
Bol. Cam. Mapa Geol6gico de Espafza 6, 353--388.
Distribution and Evolution of Clay Minerals in Central
------~~----Facies,-nuero Basin, Valladolid Province, Spain
M. POZO, S. LEGUEY
Departamento de Geologia y Geoquimica, Facultad de Ciencias, Universidad Aut6noma, Canto Blanco, 28049
Madrid, Espaiia
The materials refilling the central facies at Duero basin (Province ofValladolid,
Spain) are characterized by a variegated lithology which has been differentiated
in three lithostratigraphic units. Their main features are as
follows:
Lower unit (Facies Tierra de Campos). Characterized by detrital materials,
usually sand and clays. The main clay minerals are kaolinite, illite and
smectite with good crystallinity. At the top of this unit levels are often found
with organic matter (0.5-1.7%) and palygorskite, illite and sniectites as the
clay minerals (Pozo et al., 1984; Garcia Ab bad & Rey Salgado, 1973; Ordoflez
et al., 1980).
Middle unit (Facies Cuesta). With a thickness between 60-80 m, the main
lithology of this unit is mar!, dolostone, limestone and in some areas
gypsum. Two zones were differentiated, with a clay minerals evolution as
. follows: ,
a) Lower zone. The gradual degradation of illite and kaolinite and the genesis
of smectite and palygorskite in alkaline environment were observed:·illitekaolinite-smectite
~ illite/hydromica-smectite-vermiculite-interstratified
minerals-palygorski te.
This mineralogy indicates the transition from a fluvial to lacustrine environment.
In some areas beside dolomite gypsum appears as well as clay levels with
illite, smectite, palygorskite and sepiolite (Ordoflez et al., 1981; Pozo &
Carames, 1983);
b) Upper zone. Related to edaphic and karstic processes (Pozo & Leguey,
1984), the clay mineral association was as follows: illitelhydromica-palygorskite-sepiolite.

Abstracts 345
Upper unit (Facies Paramos). With a thickness between 2-10 m, this unit was
composed of lacustrine limestones with t)J.in layers of sepiolite related to
karstic processes.
The different associations of clay minerals from bottom to top show us the
gradual evolution of the deposition environments from fluvial (lower unit) to
lacustrine (upper unit) with a middle unit of transition.
Garcia AbbadF.J., Rey Salgado J., 1973. Cartografia del terciario y cuaternario de Valladolid. Bol.
Inst. Geol. Min. T-84, IV, 213-227.
Ordoiiez S., L6pez-Aguayo F., Garcia del Cura M.A., 1980. Contribuci6n al conocimiento del sector
centro-oriental de la cuenca del Dtiero. (Sector Roa-Baltanas). Estudios geol. 36, 361-369.
Ordoiiez S., Garcia del Cura M.A., L6pez-Aguayo F., 1981. Chemical carbonated sedimimts in
continental basins: The Duero basin. JAS. 2nd. Eur. Mtg., Bologna, Abstract.
Pozo M., Carames M., 1983. Sobre la presencia de minerales fibrosos de la arcilla en el sector
central de la cuenca del Duero (Facies Cuesta). Bol. Soc. esp. Min. 7, 51-58.
Pozo M., Carames M., Fonolla F., 198.4. Estudio mineral6gico, geoquimico y paleontol6gico de los
materiales de transici6n de facies fluviales a evaporiticas en el sector central de la Cuenca del
Duero. Materiales y Procesos Geol6gicos V-II, II, 95-113.
Pozo M., Leguey S., 1984. Estudio mineral6gico y geoquimico de las Facies Cuesta en el sector
suroccidental de la cuenca del Duero. I Congreso Espaiiol de Geologia T-II, 267-283.
Lithium-Muscovites in Granitic Pegmatites
from Central-Western Spai:J?-
A. GARCIA-SANCHEZ 1 , M.T. MARTIN PATIN0 2 , J. SAAVEDRA 1
1
U.E.I. Minera!ogia y Geoquimica, C.S.I.C., Apartado 257, 37071 Salamanca, Espaiia
2
Instituto de Edafologia y Biologja Vegetal, C.S.I.C. and Departamento de Geologia y Geoquimica, Universidad
Aut6noma, Canto Blanco, 28049 Madrid, Espaiia
On the basis of a preliminary study directed towards a regional program of
searching for Li in micas from 22 different localities, mainly from granitic
pegmatites and some greisens, four of them were selected with a Li 20 content
greater than 2%; these micas are rich in Rb and Cs, and they show a pink
colour. Only one of. these pegmatites has a symmetrically-zoned structure in
several parts of its length (1.5 km); with a maximum of thickness of 6-8 m,
the following mineralogical distribution was observed (samples separated
by heavy liquids, etc., then X-ray diffraction and petrographical studies of
thin sections, etc.): a border zone with spodumene, amblygonite, lithiummuscovite,
albite and quartz; a central zone with quartz, lithium-muscovite,
albite and.lesser quantities' of amblygonite, bikitaite, eucryptite and tourmaline.
This pegmatite contains trace quantities of cassiterite, arsenopyrite,
chalcopyrite and sphalerite.ln the other three pegmatitic bodies there is no
zoned structure, but rather a centimetric bedding of, only, white and pink
zones and its mineralogical composition is very similar, with lithium-muscovite,
albite and quartz as main minerals, and cassiterite, amblygonite, topaz,
tourmaline, eucryptite and several sulphate and phosphate (of Mn, Fe, etc.)
minerals. All samples are mineralized in tin (about 800 ppm) and tantalum
(about 100 ppm).
The geoch:emical study of the lithium-muscovites shows that there are no

------------------~- ·---~--
346
Abstracts
systematic variations for Li, Rb, Mn, Cs, Fe and Ti with respect to their
position in the same pegmatite and the grain size and, probably, with respect
to the relative time of crystallization~ -In-:-generai;--there- is-a positive
correlation between Li, Rb and Cs and, also, their 'concentrations are increased
towards the core of the zoned pegmatite. The high con~ents of these
elements in the wall-rocks (up to several thousands of ppm in relation to
contents lesser that 100 ppm in the regional schists) show a big mobility with
infiltration of residual fluids rich in .these elements.
Five samples ofmicas were chosen for the study of polymorphism and
specific compositions. X-ray powder diffractograms and partial chemical
analysis gave the following results:
Sample
Structure type
LizO Rb Cs MnO FezOJ TiOz
wt% wt% wt% wt% wt% wt%
CA
Reddish lilac
VR
Pink
LN
Whitish pink
F
Pale pink
---·---
VF
Greenish yellow
!M» 2 M 1 4.40 0.52 0.16 0.25 0.24 0.17
!M=2MI 3.24 1.30 0.51 0.21 0.11 0.21
2M 1 >!M 2.63 0.80 0.14 0.15 0.1 0.17
2M 1 >!M 2.61 0.80 0.29 0.19 0.1 0.18
2MI 0.65 0.06 0.20 0.01 0.22 0.15
There is a good correlation between structure-type and Li 2 0 (%) (Levinson,
1953; Munoz, 1968; Rinaldi et al., 1972). Other authors also have considered
this controversial question. Our data do not agree exactly with that previously
proposed about the ra:nge of LizO for different structure-type. Also,
the observed basal spacings, the chemical composition and the fact that in
the same hand sample the micas show different structure-types, suggest the
existence of two distinct structures intimately intergrown or as separate
grains: the one rich in lithium (lepidolite) and the other Li-poor (Li-muscovite),
when the Li 20-content is intermediate (in this.case, between 2.61 and
4.40 Li 2 0, wt%).
There is clear a relationship between intensity of pink colour and Li 2 0
and/or MnO contents, but not with other transition elements such as Fe
and Ti. Thus, the ratio Fe/Mn (Deer et al., 1971), is not decisive. The probable
nature of this may be the Mn 3 + (crystal-field theory) or charge transfer
Mn+ 2 _, Mn 3 +, Mn 2 + _, Fe 3 +, without discarding the possibility of the
existence of a colour-center.
All the mineralogical, chemical, petrographical and field data strongly suggest
an origin of Li-micas through probably subsolidus reaction of spodumene
and feldspars (plagioclase, etc.) with fluorine-bearing aqueous gas.
Thus, the mechanism of formation of these pegmatites occurs in two stages:
the one on early magmatic stage (direct crystallization from a fluidgranite
derived inward), and the second a hydrothermal metasomatic stage, with
migration of Li-rich fluids towards the wall-rocks.
Deer W.A., Howie R.A., Zussman J., 1971. Rock-Forming Minerals. J. Wiley & Sons, New York.
Levinson A., 1953. Studies in the mica groups. Relationship between polymorphism and composition
in the muscovite-lepidolite system. Am. Miner. 38, 88-107.
Munoz J.L., 1968. Physical properties ofsynthetic lepido!ites. Am. Miner. 53, 1490-1512.
Rinaldi R., Cerny P., Ferguson R.B., 1972. The Tanco Pegmatite at Bernic Lake, Manitoba. VI.
Lithium-Rubidium-Cesium micas. Can. Mineralogist 11, 690-707.

-
Abstracts
Weathering Sequences of Acidic Volcanic Rocks,
Granites and Gneisses
347
F. VENIALE, U. ZEZZA, F. SOGGETTI, F. CAUCIA
Dipartimento di Scienze della Terra, Sezione mineralogico-petrografica, Universita di Pavia, Via A. Bassi 4, 27100
Pavia, Italia
The investigated formations are located in the region between Valsesia and
lake Maggiore (northern Italy). The climat is inland temperate continental,
with somewhat humid. seasons in spring and autumn.
Analyses have been carried out be means of X-ray diffraction, thermal
techniques, electron diffraction and microscopy.
The alteration products of acidic volcanic rocks (rhyolitic la vas, tuffo-lavas
·and ignimbrites) indicate the original texture of parent rock ground-mass
play an important role in controlling the (neo)formation of clay minerals
within the weathering profiles.
The following main sequences of alteration have been observed:
a) 11itreous texture:
allophane ---7 halloysite ---7 gibbsite
(spheric)
(proto) (meta)
~(lath)/
b) tuffaceous and crypto-rnicro-crystalline texture:
'
(allophane) ---7 halloysite ---7 gibbsite
(gibbsite)~--- ~
boehmite (fibrous) ---7 (platy) - kaolinite
(gibbsite)
As a general•rule, allophane is present in the early weathering products of
volcanic rocks having matrix with vitreous texture; the same is not always
the case for facies with tuffaceous ground-mass.It is absent when the texture
of the parent rock is crystalline.
Electron diffraction patterns of single particles showing fibrous-tubular
shape indicate they are halloysite and/ora boehmite. The presence of boehm­
. ite as an incipient phase of weathering (although questionable, because it
might also be a deuteric product) can be due to high amounts of Fe-oxyhydroxides
influencing the transformation boehmite ---7 gibbsite. Fibrous
boehmite may evolve into platy particle by ageing. The presence of gibbsite
as intermediate phase is not always certain; in some case it represents the
final breakdown product of kaolin minerals.
No amorphous materials have been detected within the alteration product of
feldspars (pheno-crystals in volcanic rocks, or constituents of granites and
gneisses). Detailed investigat.ions by SEM and microprobe support the existence
of imogolite as (proto) phase on the surface of weathered feldspar
crystals. ·

348 Abstracts
Characteristics of Clays from the Central Valley
of Costa Rica .,
A.G. LOSCHI GHITTONP, M. BERTOLANP
1
Istituto di Mineralogia e Petrologia, Universita di Modena, Largo S. Eufemia 19, 41100 Modena, Italia
2
Centro Ceramico di Bologna, Sezione di Modena, Italia
The clay formations of the Central Valley of Costa Rica were examined
during a research trip in April 1983.
The following were identified: a) clays of hydrothermal origin derived from
both volcanic and sedimentary rocks; b) clays of mixed origin, in part hydrothermal
and in part of subaerial alteration; c) residual clays with lateritictype
transformation; even these last clays derive from andesitic and basaltic
lava, from tuffs, and from sedimentary rocks, such as limestones, sandstones,
and siltstones; d) marine sedimentary clays, from the low valley of the Rio
Reventazon near Peralta; e) red and grey volcano-sedimentary clays near
Colon; f) lacustral sedimentary clays from the Plio-Pleistocene basin ofRio
Grande near Ramon.
Predominating among the clays of hydrothermal origin are the kaolinites,
which are always rich in quartz, substituted at times by cristobalite. Illite
may be present with kaolinite. The presence of sulphates, such as alunite and
jarosite, is rare. The principal deposits are at Tabl6n, Lourdes de Agua
Calienre;·cerfo-Mirias n.-ear-SarifaA.na, Ochomogo, and Santa Elena.
Above Turrialba, near Verbena Norte, the clayey mineral is halloysite, with
quartz and cristobalite extremely scarce.
Illitic clays of hydrothermal genesis are found at Ochomogo and Santa
Elena. In this locality the presence of vermiculite is probable.
At Llano Grande, hydrothermal processes produced amorphous silica, with
little kaolini te and cristobali te.
The residual clays of lateritic-type genesis are abundant in quartz and frequently
have large amounts of montmorillonite. They often contain disordered
kaolinite, such as those near Muii.eco, or illite and kaolinite which form
banks along the road to Jerico.
Marine sedimentary clays contain carbonates in the form of calcite with
quartz and feldspar. The prevalent clayey mineral is montmorillonite. Kaolinite
is scarce and often disordered.
The clays of Colon are generally illites, with very variable quantities of
feldspar.
Lacustrine sedimentary clays have frequently Often undergone hydrothermal
forces. They are kaolinites and montmorillonites. Cristobalite often is
associated with or replaces quartz.
Overall, the most widespread clay mineral in Costa Rica is kaolinite, often
disordered, which is prevalently formed hydrothermally, but also beginning
from lateritic transformation, in which case it is very disordered. Montmorillonite
is the typical clay mineral of lateritic products, but it is also abundant
in sedimentary clays, especially marine ones. Chlorite is very rare. ,
Part of the clays examined, and in particular those of hydrothermal origin,
may be of industrial use, particularly in the ceramic sector, limited however
to industrial products for flooring and facing.

Abstracts
349
Occurrence of Fibrous Minerals in the Tertiary of
La Alameda, Ciudad·Real, Spain
J.M. MARTIN-POZAS'. J.M. MARTIN-VIVALDP, J. NAVARRETE 1
1
Departamento de Cristalografia y Mineralogia, Facultad de Geologia, Uriiversidad Complutense, 28040 Madrid,
Espafia
. z Compafiia General de Sondeos, Coraz6n de Maria 15, 28002 Madrid, Espafia
The aim of the present work was to analyze and characterize mineralogically
the fibrous clays situated in Tertiary sediments in the Province of Ciudad
Real, close to the small villages of La Alameda and Belvis. These Tertiary
materials in transgression over the Paleozoic metasediments of Ossa Morena
are Miocene in age.
On a regional scale, the Tertiary sediments exhibit detrital episodes with
lacustrine and even saline environments. From the morphological point of
view, this succession gives rise to depressed reliefs as a result of the lack of
consistency in the materials. The stratigraphical section observable in the
zone studied is as follows:
- Marly clays, rather sandy, reddish in colour, composed of illite and
kaolinite clay minerals with a depth of about 5 m;
- Marly clays, compositionally similar to those mentioned above, though
less intense in colour (3 m);
- Absorbent clays composed mainly of palygorskite, accompanied by dolomite
carbonates and quartz (approximately 3 m);
- Terminal limestones of the series (2 m).
Apart from the characterization of the palygorskite-bearing materials, the
study also relates the presence of these materials to others similar in composition
situated in differ~t geographical zones of the Iberian Peninsula.
Huertas F., Linares J., Martin-Vivaldi J.L., 1971. Minerales fibrosos de la arcilla en cuencas
sedimentarias espaiiolas. I.- Cuenca del Tajo. Bol. Inst. Geol. Min. LXXXII-VI, 534-542.
Galan E., Brell J.M., La Iglesia A., Robertson R.H.S., 1976. The Caceres palygorskite deposit,
Spain. Pp. 81-94, in: Proc. Int. Clay Conf. 1975, Mexico City (S.W. Bailey, editor), Wilmette.
Martin-Pozas J .M., Martin-Vivaldi J .M., Sanchez-Camazano M., 1983. El yacimiento de Sepiolita -
Palygorskita de Sacramenia, Segovia. Bol. Inst. Geol. Min. XCIV-II, 113-120.

350 Abstracts
Clay ¥ineralogical Trends in the Holocene Sediments
of the Gulf of Taranto, Southern~Haly-~-
T. PESCATORE 1 , J. THOREZ 2 , M.R. SENATORE 1 , S. ABDEL GADIR 4 , M.
MONTCHARMONP, F. DAMBLON 4 , M. STREEL 4
1 Dipartimento di Scienze della Terra, Universita di Napo!i, LargoS. Marcellino 10, 80138 Napoli, Italia
2
Laboratoire des Argiles, Institut de Mineralogie, Universite de Liege, 9 place du 20 aout, 4000 Liege, Belgique
3
Istituto di Paleontologia, Universita di Napoli, LargoS. Marcellino 10, 80138 Napoli, Italia
4
Laboratoire de Palynologie et Paleobotanique, Universite de Liege, 9 place du 20 aout, 4000 Liege, Belgique
This contribution is a part of the «Oceanografia e Fondi Marini» programme
(contracts n. 79.1434.88 and 80.00674.88) set up by the Italian National
Science Research Council. It concerns the study of the Holocene to Recent
sediments of the Gulf of Taranto completed by subsurface (grab) samples
(down to a depth of 10 cm) and several cores (3m maximum in length)
located at different sites of the gulf. Seven of these cores have been selected
for detailed mineralogical, palynological (pollens and Dynoflagelates) and
micropaleontological (Foraminifera) analyses in addition to other techniques.
Such a combined interdisciplinary study has appeared, indeed, useful
and even necessary in order to assess the correct but relative stratigraphy of
the accumulated sediments. Moreover, this approach has been referred to in
view of a tentative paleoclimatic _reconstruction. . .
--------------------------- Tne mineraloglcafcomposiiion of the bulk sediments, apart from their relatively
high contents in the clay-size fraction, consists of quartz, carbonates
and feldspars. The< 2 Jlm fraction is generally characterized by the admixture
of ten clay components: illites and smectites - both with variable
crystallinities and crystallochemical compositions-; more or less fresh Fechlorite;
vermiculite and minor kaolinite as representative of simple clay
minerals. However, various types of mixed layers also occur: (10-14v), (10-
14c), (10-14sm) (with different states of swelling properties), (14c-14v) and a
naturally swollen (17 A) complex. All these clay components form admixtures
which, at a first sight, seem to exist with a global, uniform, qualitative and
quantitative composition. However, sensitive variations may be put forward
according to the geographical position and stratigraphical range of the
selected cores. These variations and trends are supported by complementary
mineralogical and micropaleontological data. Clay mineral changes ate
more evident when referring to a comparison of the minerals two by two
through intensity ratios of their basal spacings (001) as well as when following
the changes of crystallinities for illites and swelling components. These
variations and trends are themselves controlled and supported by the palynological
and micropaleontological contents of the sediments; these data
indicate, for instance, clear cuts (stratigraphical gaps), irregularities in the
deposition process and variable rates of sedimentation. In addition to the
periods of non-deposition, recycling processes have taken place due to the
activity of subsurface and density currents, a hypothesis which finds its
support from the study of the actual physiography and currents pattern-of
the Gulf of Taranto.
From the analysis of the clay compositions, a hydrolysis index (H.I.) has been
calculated (Thorez, these Proceedings) where numerical data are compared
with those obtained from the other techniques. Clay mineralogy, hydrolysis
index, palynology and micropaleontology allow the reconstruction of paleoclimatic
curves for each of the seven cores analysed, which further on may be
correlated, thus providing an indication about the climatic conditions occurring
on the continent and in the marine waters. Mean temperatures (warmcold)
of the latter are determined from the study of Foraminifera. An estimation
of the wet and dry conditions is sustained by palynological data and
from the results of the clay mineral studies, since both materials, pollens and
clays, were delivered contemporaneously to the gulf. However, caution is _

-
Abstracts 351
required for the interpretation of the climatic information gathered from the
study of the clay assemblages. Some of these may and are reworked from
older deposits-sediments and paleosoils which become intermixed with freshly
eroded minerals from the substratum and transported to the gulf
through rivers (western part of the gulf). There is also the existence of a
multisource potentiality within the surrounding continental - coast and
hinterland - formations. The clays are subjected, in the gulf waters, to
surface, subsurface and density currents, the latter yielding the existence of
mechanically reworked packets of previous sediments at several places,
according to the location in the Taranto Valley.
Despite all these restrictions at the level of the clay mineral interpretation,
but thanks to the information provided by the other studies, including the
geology and physiography of the whole gulf, it appeared worthwhile to seek
the reliability of all the sedimentary and paleoclimatic reconstructions proposed
here, in particular because they are supported by independent parameters
and factors (clays, pollens, Foraminifera) now found together within
the final deposits. Hence the necessary but useful interdisciplinary study.
This has allowed a control of the nature and sources of the clay minerals
(essentially inherited from the near continent, in their fresh and weathered
states), the relative stratigraphy of the accumulated sediments (with clues
about their regime of settlement), and the paleoclimatic reconstruction even
for series which occur within rather narrow periods of geological time.
Distribution and Behaviour of some Trace Elements
in the Gulf of Taranto Muds, Southern Italy
G.NUOVO
Dipartimento Geomineralogico dell'Universita di· Bari, Campus, Via G. Salvemini, 70124 Bari, Italia
Traces of Ba, Zn, Rb and Sr are present in 16 samples of marine muds
dredged in the Gulf of Taranto, at depths from 40 to 1500 m along the
Calabrian-Apulian coasts. The study of their distribution shows that Sr is the
only element related both to the carbonate phases and clay minerals; all the
others are linked to the non-carbonate phases. Statistical analysis of results
shows significant differences between samples from the western (Calabria)
ancj., respectively, north-eastern area (Apulia). The data obtained permite the
following preliminary considerations:
a) the distribution patterns of the four elements do not show any major
deviation when compared with, known data for infra-Pleistocene sediments;
b) strontium is chiefly related\to the carbonate fractions, showing higher
values in the north-eastern area samples, presumably because of the abundant
carbonate fraction contained in these sediments;
c) the Sr/Ca correlation coefficient, when estimated for all the samples, is
lower in comparison with the corresponding values, separately estimated for
each of the two sample series. This can be ascribed to different genetic
features of carbonates (clastic or biogenic contributions, chemical precipita-
~~- '
Since the carbonate fraction behaves as a diluent as regards both Sr and Ca,
we studied the-correlations among all the elements, including the trace ones,

352 Abstracts
after removal of carbonates with 0.5 N HCI. Most of the observed correlations
correspond to a probability level less than 1%, the value assumed as
critical in this work. Statistical-calculations-lead-however-to· the following
observations:
- even in carbonate-free samples Sr shows a positive strong correlation
with Ca, taking into account all the samples; while the correlation lacks
significance within each sample series. This can be ascribed to the small
number of samples from the north-eastern area (5 samples) and to the low
variability of both Sr and Ca contents among the samples from the western
area;
- rubidium appears positively linked to Kin each sample series, but the
significance disappears when all the samples are grouped. Since K-feldspars
are very scarce in all the samples, it is presumable that the Rb/K correlation
chiefly involves the exchangeable K contained in illite type 10 A minerals;
- barium shows more significant correlations in the north-eastern area
samples. With regard to the~ western samples, a positive correlation with K
and, to a lesser extent, Na is evident. Taking into account the origin of terrigenous
contributions, it seems that Ba is linked to the quartz-feldspathic
fractions;
- zinc shows, on the whole, a rather irregular behaviour; as regards all the
samples grouped, there are some strong correlations, both negative (Zn/Si,
Zn/K) and positive (Zn/Na, Zn/H 2 0+). A strong positive correlation Zn/illite
for the samples from the western area is also evident. It is also likely that
organic substances play an important role in the distribution of this element.
All these features lead to an overall distribution pattern very similar to the
behaviour of these elements in the infra-Pleistocene clays outcropping
------------------~~---- around the (;ulf of Taranto. This is consistent with the statement that the
---:G;lf o(Ta~anto-itself may be considered the actual «continuation» of the
ancient Bradano Foretrough.
Characteristics of the Hercynian Metamorphism
in the Pola de Gord6n Matallana Coal basin,
Le6n Province, Spain
E. GALAN 1 , A. APARICI0 2 , M. DOVAU
1
Departamento de Geologia, Facultad de Quimica, Universidad de Sevilla, Apdo. 533, 41071 Sevilla, Espai\a
' Institute de Geologia, C.S.I.C., Gutierrez AbascaJ 2, 28006 Madrid, Espai\a _
3
Departamento de Cristalografia y Mineralogia, Facultad de Geologia, Universidad Complutense, 28040 Madrid,
Espai\a
The Pola de Gord6n-Matallana coal basin forms part of a synclinal macrostructure
made up of Paleozoic rocks, from the Cambrian up to the Devonian,
in whose core are unconformable marine and continental Carboniferous
materials (Namurian-Westphalian, and Stephanian, in age, respectively).
Paleozoic materials have undergone an Hercynian very low or low grade
metamorphism. This paper deals with the metamorphism of these Paleozoic
rocks on the basis of the mineralogical assemblages found and some crystallochemical
features of phyllosilicates.
For this study, selected shales and lutites were sampled from the Cambrian,

Abstracts 353
Ordovician, Silurian, Lower and Middle Devonian, and marine Carbonifer- .
ous, in various typical sections of this basin.
The mineralogical study was carried out by X-ray diffraction and microscopic
analysis.
According to the age of the samples tested, the following mineralogical
assemblages were found:
-

Section Ill
Crystal Chemistry and Structures

Miner. Petrogr. Acta
Vol. 29·A, pp. 357-362 (1985)
Characterization of Naturally Occurring Iron Oxides
and Comparative Thermal Reactions with Glycerol
E. MENDELOVICI, A. SAGARZAZU, R. VILLALBA
Laboratorio Fisicoquimica de Materiales, IVIC, Apartado 21827, Caracas, 1020 A, Venezuela
ABSTRACT - The thermal reaction of lepidocrocite with glycerol led to a
complete transformation of y-FeOOH into iron glycerolato complex; whatever
the surface area of the starting material while the reaction of hematite is
strongly dependent on the surface area of the starting material. Goethite (-
5% in the samples studied) was completely· transformed by glycerol, but
magnetite (1.83% in the hematite sample) r7Plained unchanged.
Introduction
Experimental
The reaction with glycerol of different
pure iron oxides has been' described
by FULS et al. (1970) and by
RADOSLOVICH et al. (1970). Presumably,
the same iron glycerolato is
formed as an end product independent
of the initial iron oxide. According
to FULS et al. (1970) the general
mechanism. of iron alkoxide formation
involves glycerol condensation
and redox reactions of the iron oxides,
giving a product whose calculated
formula corresponds to
[(C3Hs03)4 Fez 3 + Fel+J.
Our general objective is to find out
the effects of the structure and sur-\
face area of natural iron oxides and of ·
associated impurities on the development
of this reaction. For this purpose,
natural iron oxides considered
here were previously analyzed and
characterized.
The chemical analysis of natural
hematite ore from El Pao, Edo. Bolivar,
was carried out by Atomic
Absorption Spectroscopy (AAS),
after crushing (::5 150 mesh) and dissolution
of the sample in hot cone.
HCl. Total iron and Fe2+ were determined
by classical dichromatometry.
Synthetic and natural lepidocrocite
(Wurtemburg, Lubeneck) used in this
work were previously described by
MENDELOVICI et al. (1982; 1984a).
Pure goethite was prepared from
Fe(N03h (SCHULZE, 1982). Pure
magnetite was synthetized from
FeS04 (SIDHU et al., 1978). These
iron oxides were characterized · by
XRD (random powders) employing
. FeKa radiation, IR absorption spectroscopy
(0-25% Csi disks) and sorptometry
for surface area determination
(BET). Each sample (3g) was
thoroughly reacted with water-free

358 . E. Mendelovici, A. Sagar;;azu, R. Villalba
glycerol (SOcc) at 245°C (reflux temperature)
for 16 hours in a flask fitted
with a large open condenser tube.
The resulting solids were separated
by centrifugation, washed with distilled
water until free of glycerol (eerie
ammonium nitrate test), finally
washed with spectroscopic grade acetone
and air dried. The reaction products
were. examined by X-ray powder
diffraction (Philips 1730 model
diffractometer), infrared spectroscopy
(Perkin-Elmer 567 model spectra-
photometer) and sorptometry (Quantasorb
apparatus1; -For--comparative
purposes, the same experimental
conditions and instrumental settings
were employed for each product.
Results and discussion
According to the XRD information
(Fig. la) the natural iron oxide sample
from Edo. Bolivar, which has a
"' . CO
N
"' CO
"" "' CO
~ "' c "!
N
N
M

Characterization of Naturally Occurring-Iron Oxides ... 359
surface area of < 5m 2 /g, is a crystallized
a-Fe 2 0 3 specimen containing
traces of quartz, goethite (- 5%),
magnetite (1.84%) and Alz0 3 (1.06%).
In order to find out the nature of this
aluminium, the sample was treated
with 1.25M NaOH in a shaking bath
at 75oC (MACKENZIE & ROBERT­
SON, 1961). After 24 hours practically
all the aluminium was extracted
by NaOH, indicating that AI is not
substituting for Fe in this natural
hematite.
The reaction of the natural hematite
with glycerol for 16 hours led to
the formation of a small amount of
iron alkoxide, the transformation of
a-Fe 2 0 3 being far from completion.
This can be inferred from the diffractogram
shown in Fig. lb, where
the strong lines due to hematite in
the original sample are clearly discernible
although somewhat less intense
than: in the starting material.
This diffractogram shows also the
main peak due to iron alkoxide at 8 A.
The analysis of Fe 2 + in the reacted
solid can be used as an indicator of
the progress of iron oxide transformation
into iron alkoxide.
When the surface area of natural
hematite was brought to 17 m 2 /g (by
controlled mortar grinding), the intensities
of the a-Fe 2 0 3 X-ray lines
were diminished. The reaction of this
material with glycerol resulted in
higher amounts of iron alkoxide formation
although it, too, did not proceed
to completion, since hematite
was always detected in the diffractogram
of the reacted solid (Fig. le).
Similar results were obtained when
the surface area of the natural hematite
was brought to 33 m 2 /g and this
material reacted with glycerol,
although in this case the transformation
proceeded to a greater extent. It
is not plausible here to calculate the
degree of transformation since, in '
addition to a-Fe 2 0 3 , the natural iron
oxide sample contains other iron oxides
which are susceptible to transformation
with glycerol. However, in
our reaction of natural hematite, the
relative degree of transformation into
an iron glycerolato compound could
be inferred from the data shown in
Table 1. This table shows a rough
correlation between the surface area
of the iron oxide, the Fe 2 + /total Fe
ratios and the integrated area of the
alkoxide X-ray peaks at 8 A.
FULS et al. (1970) reported that an
hematite which has a surface area of
39 m 2 /g was completely transformed
after 16 hours reaction with glycerol.
TABLE 1
Correlation between surface area (S 0
) of iron oxide with Fe 2 + /total Fe ratios and corresponding
alkoxide (X-ray peak) intensities

360 E. Mendelovici, A. Sagarzazu, R. Villalba
We employed such experimental conditions
to ensure an optimum degree
of transformation, that is, stirring the
reaction mixture for thorough contact
and 16 hours thermal reaction
time .. Even after 40 hours of thermal
reaction (at 245°C), the natural
hematite was not completely transformed
into iron alkoxide. The colour
of our hematite alkoxide was always
reddish-brown in contrast whh the
typical green colour of alkoxides resulting
from a complete transformation
of iron oxy-hydroxides.
. The small amounts of goethite
(estimated as 5%) originally present
in the hematite ore(!) are no longer
detected in the diffractograms of the
. ·~·-~-~-~·-glycerol·-reactea-proauct:s:·~ This
means that a-FeOOH has been completely
transformed. On the other
hand, magnetite (1.83%) was not.
affected here by the reaction with
glycerol, since the diffraction effect at
2.96 A is always detected in the X-ray
diffractograms (see Fig. 1). When
pure synthetic, crystalline magnetite
was reacted with glycerol we found
that only a small amount of iron alkoxide
was formed. The corresponding
XRD pattern shows that the positions
(I) It is common to find in the nature goethite
accompanying hematite (KAMPF &
SCHWERTMANN, 1982).
and intensities of Fe 3 0 4 lines remain
almost unchanged.Theother compo-
;~~ts ofthis··~a:1:ii~af hemaiite stated
in Table 2 do not seem to play any
particular role in the iron glycerolato
formation.
The diffractogram recorded in Fig.
le exhibits, besides the main reflection
at 8.063 A, other peaks attributed
to iron alkoxide (FULS et al.,
1970). The alkoxide derivative of lepidocrocite
gives a similar pattern, but
without the lines due to the starting
material. This means that in this case
y-FeOOH has been completely transformed.
Synthetic goethite (surface
area 22 m 2 /g) is also completely transformed,
although the pattern of the
goethite alkoxide is not the same as
those of iron glycerolato products derived
from a-Fe 2 0 3 _ or y-FeOOH.
Moreover, the X-ray diffractograms
of the latters, display both, weak
peaks at 7.45, 3.29 and 2.85 A, which
are not detected in the pattern of
goethite glycerolato. MURAD (1979)
attributed such reflections to synthetic
akaganeite, ~-FeOOH.
As stated before, the natural lepidocrocite,
which is a well crystallized
y-FeOOH specimen and has a surface
area < 5 m 2 /g was completely transformed
into iron alkoxide when
reacted with glycerol. The same results
were obtained with synthetic
TABLE 2
Chemical composition in % of iron oxide from El Pao
0.21 1.06 95.74 0.57 0.10 0.70 0.21 tr tr 0.20 1.06
tr, traces

Characterization of Naturally Occurring Iron Oxides ... 361
.-L---­
"'
4000 3500 3000 2500 2000 1500
cw1
1000 ,500 250
Fig. 2 -Infrared spectra (Csi disks) of iron alkoxides derived from: a, hematite; b, lepidocrocite.
H = hematite.
lepidocrocite, whose surface area is
72m 2 /g. This means that for the open,
orthorhombic structure of y~FeOOH,
the transformation is independent of
the surface area, hence of the particle
size. Also; the impurities contained in
this natural lepidocrocite (as 1.39%
quartz and 2.47% MnO) do not have
any specific influence on the iron
glycerolato formation. As expec.ted,
traces of goethite contained by natu':.
ral lepidocrocite were completely
transformed into iron alkoxide.
The hydrolysis by boiling H 2 0 of
the naturallepidocrocite alkoxide to
magneticspinels, which is a topochemical
reaction, has been comparatively
discussed with solid-state topotactic
conversions of y-FeOOH (MEN­
DELOVICI et al., 1984 a, b).
The infrared spectra, in the 4000-
250 cm- 1 region of the glycerolato derivatives
from lepidocrocite and
hematite, are represented in Fig. 2.
Beside the absorption bands due to
the iron glycerolato complex, the
hematite derivative spectrum exhibits
also those of a-Fe 2 0 3 . FULS et
al. (1970) and RADOSLOVICH et aL
(1970) reported the infrared spectra
of iron alkoxides prepared from
goethite, lepidocrocite and hematite.
According to these authors, the end
products are the same whatever the
starting iron oxide and the Fe 2 + /total
Fe ratio may explain slight differences
between their IR spectra. This
statement is probably valid for the
alkoxide of lepidocrocite and hematite.
The goethite derivative, which
according to our results has a different
X-ray diffraction pattern than
that ofhematite or lepidocrocite, will
be discussed in a further communication.
As expected from thermodynamic
considerations, the structure of iron
oxides plays an important role in explaining
the difference in reactivity
between FeOOH and a-Fe 2 0 3 • The
open (orthorhombic) structure of y­
FeOOH is easily transformed into
iron alkoxide, whereas the reaction of
the rigid (rhombohedral) structure of
a-Fe 2 0 3 is much more sluggish.

362 E. Mendelovici, A. Sagarzazu, R. Villalba
REFERENCES
FuLs P .F., RoDRIQUE L., FRIPIAT J .J ., 1970. Iron alkoxide obtained by reacting iron oxides with glycerol.
Clays Clay Miner. 18, 53-62.
KAMPF N., SCHWERTMANN U., 1982. Quantitative determination ofgoethite and hematite in kaolinite
soils by X-ray diffraction. Clay Minerals 17, 359-365.
MAcKENZIE R.C., RoBERTSON R.H., 1961. The quantitative determination of halloysite, goethite and
gibbsite. Acta Univ. Carol. Geol. Suppl. 1, 139-149.
MENDELOVICI E., SAGARZAZU A., VILLALBA R., 1982. Mechanochemical reaction effects on the structure
and surface of pure, synthetic lepidocrocite. Mat. Res. Bull. 17, 1017-1023.
MENDELOVICI E., VILLALBA R., SAGARZAZU A., 1984a. Topotactic conversions of y-F e00H and comparative
transformation methods of iron oxides in magnetic spinels. Materials Chemistry and Physics
10, 579-584.
MENDELOVICI E., NADIV S., LIN I.J., 1984b. Morphological and magnetic changes during mechanochemical
transformation of lepidocrocite to hematite. J. Mater. Sci. 19, 1556-1562.
MuRAD E., 1979. Mossbauer and X-ray data on [3-FeOOH (akaganeite). Clay Minerals 14, 273-285.
RADOSLOVICH E.W., RAUPACH M., SLADE P.G., TAYLOR R.M., 1970. Crystalline cobalt, zinc, manganese
and irdn alkoxides of glycerol. Aust. J. Chem. 23, 1963-1971.
ScHULZE D.G., 1982. Ph.D. Thesis, Technische Universitat Munchen, West Germany.
SIDHU P.S., GILKES R.J., POSNER A.M., 1978. The synthesis and some properties ofCo, Ni, Zn, Cu, Mn
and Cd substituted magnetites. J. Inorg. Nucl. Chem. 40, 429-435.

Miner. Petrogr. Acta
Vol. 29·A, pp. 363-370 (I 985)
The IR Spectra of Hematite-Type Compounds
with Different Particle Shapes
J.E. IGLESIAS, C.J. SERNA
Instituto de Fisico-Quimica Mineral, C.S.I.C., Serrano 115-dpdo., 28006 Madrid, Espaiia
ABSTRACT- A method is presented to account for particle shape effects in the
IR absorption spectra of powdered hematite. The necessary calculations
have been carried out and are presented for direct use in the form of graphs.
Application of this method to two different hematite samples permits a good
explanation of the observed spectra. ·
Introduction
The IR absorption spectra -~f powdered
samples has been widely used
for identification purposes under the
assumption that it represents a fairly
constant fingerprint of the phase to
be characterized. It is however well
established (RUPPIN & ENGLMAN,
1970; LUXON, 1969; GENZEL &
MARTIN, 1972; HAYASHI et al.,
1979; SERNA et al., 1982), though
perhaps not sufficiently recognl.zed,
that theIR spectra of particle aggregates
can be drastically dependent on
the shape of the constituent particles.
Failure to allow for this effect has'
even led in the recent past to the
erroneous description of new mineral
phases. Thus the terms

364 J.E. Iglesias, CJ. Serna
the ellipsoid semi-axes become infinite
(VAN DE HULST, 1957; SERNA
et al., 1982). The interest of such calculations
becomes clear when one remembers
that physico-chemical conditions
of formation frequently affect
crystal habit in mineral phases, and
consequently, genetic environmental
conditions can be often inferred from
a knowledge of crystallite morphology.
The purpose of this paper is to provide
a simple method of analysis of
hematite IR spectra which will permit
the recognition of shape effects
and estimation of the particle shape
responsible for them.
Theoretical considerations
The optical constants of a compound
in the infrared can be obtained
from the analysis of the reflectance
spectra of suitable single crystals of
adequate size (>2 mm). The reflectance
spectra of hematite have been
measured by ONARI et al. (1977) and
their results are summarized in Table
1. Data for the isostructural compounds
a-Crz03 (LUCOVSKY et al.,
1977), a-Ah03 (BARKER, 1963) and
a-Tiz03 (LUCOVSKY et al., 1978) are
also available. The wavelength dependence
of the complex refractive
index, ft(A.) can be computed once the
above mentioned optical constants
are known.
In the case when the spectrum is
observed in transmission for a sample
consisting of small (

TheIR Spectra of Hematite-Type Compo~nds ... 365
the three principal axes of the ellipsoid.
Ci~~ is linearly related to the
absorption coefficient, and hence Ci~~
(A.) is directly comparable with the
spectrum obtained in absorbance on
a spectrophotometer. The application
of these theoretical results to the
calculation of the IR absorption spectra
of corundum-type microcrysta,lline
oxides with different particle
shapes has been recently illustrated
(SERNA et al., J 982).
Method of analysis
Although in the general case a
complete calculation of the absorption
spectrum along the lines
summarized above will be necessary,
for a particular case such as hematite
\
in which the theory has been proven
to match well with the observations,
a procedure can be devised to interpret
the spectrum in terms of particle
shape effects. To this end the frequencies
at which the absorption maxima
occur, i.e. the maxima of Ci~~ (A.) for
the two principal polarizations, have
been plotted as a function of the
shape factor g, under the assumption
that the crystallographic c axis .is
coincident with one of the principal
axes of the ellipsoid. In Fig. 1 such a
plot is presented for KBr which is the
most commonly used matrix. Plots
for four other less common matrix
substances are given in Fig. 2. ·
We assume that a hematite spectrum
has been recorded in KBr. In
what follows we shall also assume
that the hematite particles have a
600
400
/
/
/
,.,.,.,.,.,..---
......
......
------
----- -----~1 _________ _
zoo+-----.---~r----.-----,----,-----~--~r---~S~h~ap~e~f~a~ctTo~r~(g~)~
0 0.1 0.5 0.9
Fig. 1 - Evolution of hematite absorption maxima in KBr (Em = 2.25) with shape factor (g); A 2 u
. (-- -); Eu (--).

j
I
I
366
J.E. Iglesias, CJ. Serna
700~--------------------------.---------------------------~
a) b)
600
500
400
-------------- ---------
300
I E
u
~
::0

TheIR Spectra of Hematite-Type C~rnpounds ... 367
appears to be reasonable since the c
axis of hematite is a crystallographic
three-fold axis of symmetry. If we call
g1 the shape factor associated with
the c axis, the condition g1 + 2gz = 1
implies 0:5gz:50.5, while the value of
g1 could lie anywhere between 0 and
1, with no additional restriction.
Examination of Fig. 1 allows one to
conclude that a band must appear between
437 cm- 1 (roT) and 494 cm- 1 (coL)
and in this frequency interval its
assignment is unique (cos). From the
actual frequency observed an estimation
of gz can be made from the plot,
and from this .value the frequencies of
ro 3 , ro 4 and ro6can be determined and
compared with the experimental
values. From the determined gz
value, g1 is computed by the relation
gl = 1-2gz and from this valu.e of gl
the frequencies expected for ro1 ancl COz
can be read off the graph and checked
against the observed values. The
values of g1 and g 2 thus found can be
corroborated by running the sample
in a matrix with a different dielectric
constant. Clearly the same g values
must be responsible for the different
absorption maxima found in both
matrices.
It is clear from Fig. 1 that the precision
of gz obtained from the observed
frequency of mode cos depends on the
actual value observed, and that it de-
creases as the frequen.cy of this mode
increases. In the low precision interval
the best value of gz requires some
trial and error.
A different approach to the determination
of g1 and gz would be the
application of the generalized
Frohlich formula for the case of anisotropic
ellipsoidal particles (LUX­
ON, 1969) (*)
where the product extends to all
modes associated with a particular
direction, Sm is the dielectric constant
of the matrix, So and s~ are respectively
the static and high frequency
dielectric constant of the crystal, and
g is the relevant shape factor. For the
particular case of hematite in KBr,
equation (4) gives, using the data in
Table 1, equation (5)
0)10)2 [ 18.35gl + 2.25] 112
299·526 = 4.45gl + 2.25
and equation (6)
0)30)40)50)6 [21.85g2 + 2.25] 112
227·286·437·524 = 4.75g2 + 2.25
('') LUXON's original formula
TI Oli = [ ceo-1)g + em ] 112
i OlTi (e~ -l)g + em
is in error since from this expression there is no way to obtain either Frohlich's relation (for the
casei= 1, g = 113, em= 1) or LST relation (i = 1, g = -1).

T
368 J.E. Iglesias, CJ. Sema
TABLE 1
Infrared optical constants of hematite
COT
COL
47tp y eoo eo
co1 299 414
COz 526 662
(J)3 227 230
co4 286 368
COs 437 494
(J)6 524 662
11.50 .050
2.20 .057
1.10 .017
12.00 .028
2.90 .046
1.10 .048
6.7 20.6
7.0 24.1
Examples
Reported in Fig. 3 are theIR spectra
of two hematite samples where
shape effects are clearly illustrated.
In each case the spectra calculated by
the theory outlined above are aiso included,
to show that a fairly accur~te
match in frequency and intensity can
be achieved. In Table 2 the frequencies
of the maxima estimated by the
method of analysis are presented. In
575
300
Sphere
Lath
440
'
,,
11
11
1 1 485
ri
r I
rl
I I
I I
I I
I \ ~
I \ A A Jl
I \ 1\ I'J\
/ \_, \ 1 \ 23o
___ .,.,. (cm-1) - .......,__,....,..
-/
/
I
I
I
I
j, J
I ._
525
800 600 400 200 800 600 400 200
Fig. 3 - Comparison between observed (--) and calculated (- -
microcrysta!s.
-) spectra of hematite

TheIR Spectra ofBematite-Type Compounds ... 369
. TABLE 2
IR absorption maxima for the two hematite samples with defined particle shapes
SPHERE
LATH
Observed Estimated Assignment Observed Estimated
585 C02 650 660
575
595 co6 52,5 525
485 485 COs 440 440
385 386 col 412*
360 358 co4 300 296
230''* co3 230''*
*This band is not observed here due to the very flat morphology (BARRON et al., 1984); for
not so flat oblate ellipsoids the band is observed (WILSON et al., 1981; BARRON et al., 1984)
· *" This band is not observed in this· study owing to the spectra having been run in KBr
matrix
the first case the cos mode lies in a
region of low sensitivity in g; but a
first estimation gives 0.3

370 J.E. Iglesias, CJ. Serna
ONARI S., ARAr T ., Kuoo K., 1976. Infrared lattice vibrations and dielectric dispersion in a-Fe 2 0 3 • Phys.
Rev. B 16, 1717-172I.
OsBORN V.A., 1945. Demagnetizing factors of the general ellipsoid:Phys":'Re\17"67; 351cJ57.
RENDON J .L., SERNA C.J ., 1981. IR spectra of powder hematite: Effects of particle size and shape. Clay
Minerals 16, 375-382.
RuPPIN R., ENGLMAN R., 1970. Optical phonons of small crystals. Rep. Prog. Phys. 33, 149-196.
SERNA J.C., RENDON J.L., !GLESIAS J.E., 1982. Infrared surface modes in corundum-type microcrystalline
oxides. Spectrochim. Acta 38 A, 797-802.
VAN DE HULST H.C., 1957. Light Scattering by Small Particles. John Wiley & Sons, New York.
WILSON M.J ., RusSELL J .D., TAIT J.M., CLARK D.R., FRASER A.R., STEPHEN I., 1981. A swelling hematite/
layer-silicate complex in weathered granite. Clay Minerals 16, 261-277.
WoLSKA E., 1981. The structure ofhydrohematite. Z. Kristallogr. 154,69-75.
YARIV S.H., MENDELovrcr E., 1979. The effect of degree of crystallinity on the infrared spectrum of
hematite. Appl. Spectrosc. 33, 410-411.

Miner. Petrogr. Acta
Vol. 29·A, pp. 371-379 (1985)
Effect of Perturbing Anions on the Nature of Short-Range
Ordered Precipitation Products of Aluminum
A. VIOLANTE
Istituto di Chimica Agraria, Facoltit di Agraria, Universitit di Napoli, 80055 Portici, Italia
ABSTRACT- The hydrolytic precipitation products of aluminum obtained in
the presence of some selected organic ligands were studied by X-ray diffraction,
electron microscopy, infrared and thermal analysis.
It has been found that hydroxy-carboxylic acids (salicylic, malic, citric, tartaric
or tannic acid) had a stronger influence in inhibiting the hydrolytic
reaction of Al than monodentate ligands (ketones, amines, acetic or formic
acid), dicarboxylic (phthalic, succinic or glutaric acid), tricarboxylic (tricarballylic
acid) or amino acids (glycine, aspartic or glutaric acid). The effectiveness
in suppressing Al(OHh crystallization depended on the affinity of
the ligands for Al 3 + and on how strongly they were adsorbed on the particles
of the initially formed Al precipitation products. Above critical ligand/Al
molar ratios, the individual presence of organic ligands promoted the formation
of defective and/or disordered boehmites (pseudoboehmites) or noncrystalline
precipitation products.
Al precipitation products noncrystalline to X-ray and IR appeared to consist
of spherical particles when examined by electron microscopy. The infrared
spectra of some samples showed that the bands of the ligands coprecipitated
withAl became stronger by increasing the initialligand/Al molar ratio and
by increasing the structural disorder of the final products.
Introduction
Auminum is a common structural
constituent of primary and secondary
minerals of soils. It is released to soil
solution and natural waters through
chemical and biochemical processes, ·
undergoes hydrolysis and may give
rise to precipitated Al-oxides (HSU,
1977). Clay minerals, pH, organic and
inorganic ligands are the most important
factors which influence the
phase transformation of Al and the
mineralogy, order, particle size, specific
surface and reactivity of the Al
precipitation products (VIOLANTE
& JACKSON, 1979; 1981; VIO­
LANTE & VIOLANTE, 1980; VIO­
LANTE & HUANG, 1984; 1985).
Many studies have demonstrated
that fulvic acids and low molecular
.,weight organic acids are very important
in the translocation of Al and Fe
and pedogenesis. Natural organic
acids in soils and freshwater environments
are derived from plant and
animal residues, microbial metabo-

__
372 A. Violante
lism and rhizosphere activity. They solution contammg AlCb and indiare
low and variable in their concen~ __ y~c:[~aJ _orJfa:r?:!~J!gaJJ.d~.. The concentration
(from 1 X w-s M to 6 X lQ- 3 tration of AI was 2 X lQ-3 M. The con­
M), because they are utilized by the centration of ligands was chosen to
majority of bacteria and fungi. give the ligand/Al molar ratios (R)
However, organic acids are con- ranging from 0.0025 to 15. The samtinuously
introduced to soils through pies were aged in polyethylene botfarming
and/or natural vegetation des. The materials were washed with
(STEVENSON, 1967). deionized water and examined by X-
VIOLANTE & VIOLANTE (1980) ray powder diffraction, electr;on miand
VIOLANTE & HUANG (1985) re- croscopy, and infrared spectroscopy
vealed the important role of organic using the procedures described by
ligands · in influencing the rate of VIOLANTE & HUANG (1985). Secrystallization
of Al-trihydroxides lected samples of 250 mg were heated
and the nature of the resulting solid in a Rikagu Differential Thermal
products. VIOLANTE. & HUANG Analyzer programmed from 25 octo
(1985) found that increasing ligand/ 900 oc at a rate of 10° min- 1 using
AI molar ratios influences the final alumina as the reference material.
- ------- ·precipinirion.--products-·or-Al" as fol:- ·
lows:
Al-hydroxide polymorphs ~ Pseudoboehmites
~ X-ray noncrystalline
materials
The aim of this work is to present a
detailed picture of the relative effectiveness
of selected organic compounds,
characterized by the presence
of different chelating groups,
namely carboxylic, hydroxyl, amino,
keto, in favouring the formation of
short-range ordered Al~hyd;oxides o~
oxyhydroxides over well crystallized
Al(OH)3 polymorphs.
Materials and method
Aluminum hydroxides were precipitated
at pH 8.0, 8.2 or 9.0 by the
slow addition of 0.05 M NaOH to the
Results and discussion
Precipitation occurs- when an AI
salt solution is neutralized with a
base. In the absence of foreign
ligands and at pH >7.0, Al-hydroxides
crystallize in a few days or even a few
hours after the sample preparation
(Fig. 2a).
Organic ligands vary in their ability
to perturb the hydrolytic reactions
of Al and to influence the nature
of AI precipitation products (Figs 1, 2
and 3).
At initial pH 8.0 and ligand/ AI ratio
of 0.1, bayerite (Fig. la), gibbsite (Fig.
lb), pseudoboehmite with distorted
_crystals of gibbsite (Fig. le) and rare
elongated crystals of nordstrandite
blended into a noncrystalline material
(Fig. ld) were found after 5
months respectively in the presence

Fig. 1 - Transmission electron micrographs of Al precipitation products formed at initial pH 8.0
and ligand/A! molar ratio of 0.1, after 5 months of aging. Bayerite formed in the presence of
oxybenzoate (a), gibbsite formed in the presence of tricarballylate (b), pseudoboehmite and distorted
crystals of gibbsite formed in the presence of oxalate (c), nordstrandite and noncrystalline
material formed in the presense of acetylacetone (d), noncrystalline materials formed in the
presence of salicylate (e) and tartrate (f).

374 A. Violante
Control
a
134
100 300 500 700 900
Temperature, cc
Fig. 2- DTA curves of AI precipitation products formed at initial pH 8.0 after 8 months of aging.
Al(OH)3 polymorphs formed in the absence of ligands (a); pseudoboehmites formed in the presence
of tannate (b; R=O.OI), citrate (c; R=O.Ol) and aspartate (d; R=O.l); noncrystalline lJ!aterial
formed in the presence of tartrate (e; R=O.l). R indicates the initial ligand/A! molar ratio.
of oxybenzoate, tricarballylate, oxalate
and acetylacetone. In the presence
of salicylate (Fig. le) or tartrate
(Fig. lf) noncrystalline materials
formed.
The noncrystalline products obtained
in the presence of didentate
(Fig. le) or tridentate ligands at R between
0.2 to 0.02 at initial pH 8.0
were shapeless colloids with fluffy
surfaces and reduced particles size.
At high magnification, noncrystalline
materials appeared to consist of
spherical particles linked together to

Effect of Perturbing Anions on the Nature ... 375
R•O. 003
R•O. 007
R•O. 02
3440
38 34 30 26 17 15 13 11 7x 100
Wavenumber (cm-1)
Fig. 3- Infrared spectra of Al precipitation products formed in the presence of tannic acid after 8
months of aging: a, bayerite and pseudoboehmite (R=0.003); b, pseudoboehmite with traces of
bayerite (R=0.007); c, stable pseudoboehmite (R=0.02); d, noncrystalline material (R=O.l).
~ .
form a disorder mosaic. On the contrary,
the noncrystalline materials
formed in the presence of polydentate
ligands were often heavy precipitates
consisting of small particles strongly
aggregated to each other (Fig. 1f).
Differential thermal analyses (Fig.
2) also show that organic ligands at
different . initial ligand/Al molar
ratios disturbed 'the final products.
The low temperature endotherm centered
at about 140 °C, attributed to
sorbed water, was an important feature
of all patterns. The sample prepared
ih the absence of ligand (Fig.
2a) showed a strong endotherm at
310 oc attributed to Al(OH)3 polymorphs.
The samples prepared in the
presence of tannate (R = 0.01), citrate
(R = 0.01) and aspartate (R = 0.1)
showed a very broad endotherm centered
near 450 oc (Figs 2b, c, d),
due to poorly crystalline boehmite.
Probably, the higher the intensity of
this endotherm the higher the crystallinity
of boehmite (Fig. 2c versus
Fig. 2b). The broad endotherms at
240 oc and 280 oc (Fig. 2d) indicated
the presence of strongly bound water
molecules. Finally, the amorphous
material formed in the presence of
tartrate (R = 0.1; Fig. 2e) showed a
gradual release of water strongly
adsorbed and/or occlused into the
aluminous particles.
The ability of organic anions to re-

376 A. Violante
tard crystallization or to perturb the
final products raised as pH decreased
and as their concentration· increased
(Fig. 3).
Figure 3 shows the IR spectra of the
Al precipitation products formed in
the presence of increasing concentrations
of tannic acid. At R = 0.003 (Fig.
3a) well defined bands of well crystallized
bayeri~e (3660, 3560, 3470, 3440
cm- 1 ) were detectable. By increasing
the initial tannate/A! molar ratio to
0.007 (Fig. 3b) the bands of bayerite
became barely detectable and disappeared
completely at the initial
tannate/A! molar ratio of 0.02 (Fig.
3c), whereas the bands of pseudoboehmite.
-~became mere distinct
(-3340, 3120 cm- 1 ). At R = 0.1 a
broad asymmetrical band at 3440
cm- 1 indicated the presence of noncrystalline
material (Fig. 3d). The
bands of the tannate anions coprecipitated
with Al between 1710 to
1210 cm- 1 became stronger by increasing
the initial concentration of
the organic ligands and by increasing
the structural disorder of the f!nal
products.
Chelating organic ligands favoured
at certain critical ligand/Al molar
ratios the formation of oxo linkages
0
6.11 A
1.31
1.85
I
2.35 3.16
b
c
f
I '
I
I
!chloride
I
I '
I
I
I
I
:aspartate
75
65 55
45
2B CuKa
35 25 15 5
Radiation
Fig. 4- X-ray diffractograms of pseudoboehmites formed at initial pH 8.0 after 1 month of aging in
the presence of tartrate (a; R=O.Ol), citrate (b; R=O.Ol), tannate (c and d; R=O.Ol and 0.02),
chloride (e; R=700) and aspartate (f; R=0.2).

Effect of Perturbing Anions on the-Nature ... 377
over that of ollinkages. Fig. 4 shows late structures so that their influence
the formation of short-range ordered on the Al-hydrolytic reactions is relboehmites
(the so-called pseudo- atively poor. At pH 1.0
of broad lines at -6.6, 3.2, 2.3 and 1.8 (McHARDY & THOMSON, 1971;
A. It appears obvious that the lower VIOLANTE & VIOLANTE, 1978).
the affinity of an anion for Al (as di- The p-oxybenzoic acid is more
scussed below) the higher the ligand! common in soils than the benzoic
Al molar ratio at which pseudo- one. It has been identified in PodzolB
boehmite formed. In fact, pseudo- horizon. It had a behaviour almost
boehmite formed at R = 0.01 in the similar to monodentate ligands bepresence
of tartrate, citrate and tan- cause it cannot form a chelate ring
nate (Figs 4a, b, c), but at R = 0.2. in with aluminum. At pH 8.0 and p­
the presence of aspartate (Fig. 4f). oxybenzoic acid!Al molar ratio of 0.1,
Hydroxy or amino mono-, di- or tri- bayerite crystallized (Fig. la).
carboxylic acids favoured the forma- Keto and alcoholic groups are pretion
of poorly crystallized or dis- sent in compounds which have been
torted boehmites much more than separated from soil organic matter.
)
dicarboxylic or monocarboxylic ALDCROFT et al. (1969) found that
acids (Figs 1-5). Chloride, ions, very high concentrations of acetone
used as control, which showed the " or ethanol reduced the rate of formapoorest
affinity for Al, promoted the tion of Al(OH) 3 polymorphs. In an
formation of pseudoboehmite only at aqueous alkaline medium containing
R = 700 (Fig. 4e).
20% wt/vol of acetone or ethanol, the
From the experiments, herein re- induction period for the formation of
ported (Figs 1-5), and from in- Al-trihydroxides increased from 5 to
formations already available 20 hours. We have ascertained that
(ALDCROFT et al., 1969; HSU, 1977; ketones, alcohols and amines had a
VIOLANTE & JACKSON, 1979; 1981; much lower influence than monocar­
VIOLANTE & VIOLANTE, 1980; boxylic acids in retarding Al(OH) 3
VIOLANTE & HUANG, 1984; 1985}, crystallization (data not shown).
it is possible to co~pare the perturb----
ing power of selected monodentate,
didentate, tridentate and polydentate Didentate ligand
ligands on Al precipitation products.
Monodentate ligands
Monocarboxylic acids (acetic, formic,
benzoic acid) cannot form che-
Dicarboxylic acids (glutaric, succinic,
phthalic, malonic or oxalic acid)
had a stronger efficacy in retarding
the hydrolytic reactions of Al than
monocarboxylic acids. A decreasing

378 A. Violante
perturbing power has been found in
the order oxalic > malonic > succinic
phthalic acid (VIOLANTE -& glu-tarater-~~ --~- ----- ~-
VIOLANTE, 1980; VIOLANTE &
HUANG, 198S). This corresponds to a
decrease in chelating stability as one
goes from a five- to a sevenmembered
ring. The carboxyl groups
in glutarate are too far apart, hence
glutarate anions behaved like monocarboxylate
ligands (Fig. Sa).
Whereas ketones are very poor perturbing
lingands, diketones (acetylacetone)
strongly complex Al. Acetylacetone
may enolize and form stable
six-membered rings with metal
atoms. Acetylacetone inhibited the
hydrolytic reactions of AI much more
-- --- -- --rhan-srrccinicorphthalic acid (Figs
1d and S) (VIOLANTE & VIOLANTE,
1980).
tri carba llyl ate
oxalate
4.3~
4.72
6.75A
Tridentate and polidentate ligands
All the tridentate ligands studied
(glutamic, aspartic, malic or tricarballylic
acid) showed a perturbing
power higher than succinic, phthalic
or malonic acid (Figs 2d, 4f and
Sb). Tricarballylic acid showed a retarding
power on AI crystallization
lower than glutamic or aspartic acid
but higher than glycine (Fig. 1 b and
fig. Sb). Only malic acid was stronger
than oxalic acid in retarding or
inhibiting AI crystallization (Fig. Se
versus Fig. Se).
Hydroxy di-, tri- or polycarboxylic
acids (tartaric, citric or tannic acid)
had a tremendous influence on perturbing
the structural organization of
ma 1 ate
29 25 21 17 13
2B CuKa Radiation
Fig. 5- X-ray diffractograms of AI precipitation
products formed at pH 9.0 and ligand/A! molar
ratio of 0.2 after 1 year of aging. Bayerite
formed in the presence of glutarate (a); bayerite
+ pseudo-boehmite formed in the presence of
tricarballylate (b); gibbsite + pseudoboehmite
formed in the presence of oxalate (c); a small
amount of gibbsite formed in the presence of
acetylacetone (d); pseudoboehmite formed in
the presence of malate (e) and noncrystalline
material formed in the presence of citrate (f).
the hydrolytic precipitation products
of AI (Fig. lf; Figs 2b, c, e; Fig. 3; Figs
f

Effect of Perturbing Anions on the Nature ... 379
4a, b, c, d; Figs Se, f). The fact that
tartrate complexes were more stable
than. succinate complexes and that
citrate complexes were more stable
than tricarballylate complexes indicates
the involvement of the -OH
groups in the chelation process.
The strong influence of tannate_
(and fulvate, as reported by KODA­
MA & SCHNITZER; 1980) in inhibiting
Al crystallization (Fig. 3) must be
attributed to their high molecular
weight which aided their physical
adsorption on the surfaces of Al precipitation
products.
Our research data reveal that the
sequence of the relative effectiveness
of organic ligands in retarding or inhibiting
Al(OH)3 crystallization is as
follows:
ketones = alcohols = amines <
monocarboxylate anions< glutarate

382 C. De Sousa Figueiredo Comes
high temperature crystalline phases
mullite and cristobalite and also to
the glass formed. Such properties depend
on both the number, dimensions
and texture of the crystals and
the amount of glass.
Nowadays, considering that energy
is very expensive, great concern is
directed towards energy savings.
Therefore, in recent years, with the
use of suitable mineralizers to encourage
the anticipated formation of
mullite, cristobalite and vitreous
phase has been tried.
The effect of mineralizers on the
temperature, rate and products of
kaolinite thermal reactions has been
------~---!he_subject of intensive research (particular
emphasis for: KUPKA, 1974;
LEMAITRE et al., 1976; BULENS &
DELMON, 1977; BULENS et al.,
1978; OAKLEY & SHARP, 1983). In
all these studies the minetalizers
both in the solid and in the liquid
state were facing or fixed at the external
surfaces of the kaolinite crystals.
However, it appears quite logical
that the mineralizer efficacy will be
better in all the kaolinite thermal
reactions if the mineralizer could be
intercalated in the kaolinite interlayer
spaces. This has never been
tested up until now; therefore this paper
is particularly concerned with the
action of intercalated mineralizers
in the formation and development of
mullite and tristobalite.
It is important to point out that the
existent literature does not explain
clearly the efficacy and the mechanisms
of the mineralization process.
But, in any case, mineralizer is defined
as any chemical compound
which-eitheF~pmmotes,-anticipates or
accelerates a chemical reaction by
catalytic, reactive or melting action.
For some mineralizers more than one
mechanism might contribute to its
mineralizing action. The melting and
the reactive actions should be more
effective if the mineralizers have low
fusion temperatures in order to provide
a liquid phase which would
facilitate atomic diffusion.
Materials and methods
Kaolinites
Two kaolinites, one residual and
structurally well ordered (Supreme
kaolinite from EEC, England) and the
other sedimentary and structurally
very disordered (Pugu D kaolinite,
Tanzania) were used. The granulometric
separates of these kaolinites with
e.s.d. less than 1 ).liD have been extracted
and characterized chemically
(X-ray fluorescence, flame spectrophotometry,
cation exchange
capacity), structurally (X-ray diffraction,
infrared spectrophotometry)
and granulometrically (particle size
distribution estimation using particle
size measurements on transmission
electron microphotographs).
Supreme kaolinite (SUPK)
Chemical analysis(%):
Si02-46.77; Ab0 3 -39.25;
FeO+Fe20 3-0.l8; Ti02-0.09;
Mg0-0.11; Ca0-0.08; K20-0.17;

-
The Effect of Mineralizers, Intercalateirin ... 383
Na 2 0-0.09; Hz0+-13.85.
Hinckley crystallinity index (HINC­
KLEY, 1963): 1.04.
Cation exchange capacity: 3.8 meq/
100 g.
Intercalation degree: 96%.
Particle size distribution (Jlm): 1.0-0.8
-30%; 0.8-0.6-40%; 0.6-0.4-20%;
0.4-0.2-8%; 0.2-0-2%.
Pugu D kaolinite (PUGK)
Chemical analysis(%):
SiOz-46.35; Alz03-38.90;
.FeO+Fez03-0.28; TiOz-0.20;
Mg0-0.05; Ca0-0.25; K 2 0-0.26;
Naz0-0.18; Hz0+-13.75.
Hinckley cristallinity index: 0.
Cation exchange capacity: 6.9 meq/
100 g.
Intercalation degree: 45%. . .
Particle size distribution (Jlm): 1.0-0.8
-5%; 0.8-0.6-8%; 0.6~0.4-20%;
0.4-0.2-55%; 0.2-0-12%.
M ineralizers
The following mineralizers have
been used: Mg(N03)z·6Hz0 (10%);
Ca(N03)z·4Hz0 (10%); MgClz·6HzO
(10%); CaClz·6HzO (10%); Mg(C3H30z)z
·4Hz0 (10%); Ca(C3H30z)z·l/2Hz0
(10%); NHN03 (5%).
The figures inside the parenthesis
represent the molar percentage corresponding
to kaolinite with a molecular
weight of 258.
Intercalating agents
Hydrazine hydrate: NH 2·NH 2·H 2 0;
Dimethylsufoxide: CH3·SO·CH3,
"
Preparation of the intercalated and mineralized
kaolinites
a) 1.5 g of kaolinite + mineralizer are
mechanically mixed and ground in
an agate mortar;
b) transference of the mixture into a
platinum crucible;
c) addition of the intercalating agent
(5 cm 3 );
d) heating of the suspension formed
to 80 oc on a sand bath for 10 minutes;
e) ultrasonic dispersion of the suspension
during 5 minutes.;
f) heating of the suspension to 80 oc
on a sand bath for 10 minutes (time
usually sufficient for the formation of
a paste);
g) spreading of a small part of the
paste onto a glass slide for XRD intercalation
examination; the intercalating
degree is estimated by the index
ID= (I 10.4 A)/(I 10.4 A+ I 7.15 A) for
hydrazine.
Heating temperatures
600, 650, 700, 800, 900, 950, 1000,
1050, 1100, 1200, 1300, 1400 °C. At all
of these temperatures the kaolinite
specimen was quenched for 20 minutes.
Quantification of mullite and cristobalite
Mullite and cristobalite contents
were estimated assuming that at
1400 oc either mullite or cristobalite
attain maximum development. The
areas of peaks corresponding to 3.39

384 C. De Sousa Figueiredo Games
A (mullite) and 4.1 A (cristobalite) in
the specimens heated at certain
temperatures were compared with
those of the same specimens heated
~t 1400 oc taken as equivalent to
100%.
Results and discussion
Kaolinites not mineralized
Mullite- The metaphase mullite I,.
which, according to WAHL (1962)
corresponds to 3Alz0 3 • 2Si0z is detected
at 950 oc approximately and
develops up to about 1100 °C. Its X­
ray diffraction lines are initially
broad but gain better definition as
~heJe:!!l:pe!"f!:t~r~)~

The Effect of Minera/izers, Intercalated in ... 385
TABLE 1
High temperature metaphases and phases developed in a well-ordered kaolinite (SUPK)
either not mineralized or mineralized with Mg(N0 3 h·6H 2 0 (10%)
I~
600
650
700
800
900
950
!000
1050
SiOz-AizOJ
amorphous
or
cryptocrys·
talline
appearance
maximum
SUPK
e.s.d.:;; I ~m
HCI = 1.04
Mullite I
3%+"spinel"
SUPK
e.s.d.:;; I ~m
HCI = 1.04
HYD+Mg(N03)z·6H 2 0(10%)
ID= 96%
Si0 2 -Aiz03
amorphous
or Mullitei
cryptocrys·
talline
appearance
j
maximum
..0
U N
·eo
5

386 C. De Sousa Figueiredo Gomes
TABLE 2 .
High temperature metaphases and phases developed in a disordered kaolinite (PUGK) either
not mineralized or mineralized with Mg~N03h·6H20-(-l0%)"--··- -
Si0z-Al 2 0 3
amorphous
or
cryptocrystalline
PUGK
e.s.d.,; 1 ~m
HCI = 0
Mullitel
PUGK
e.s.d.,; 1 ~m
HCI = 0
HYD+Mg(N0 3 )z·6H 2 0(10%)
ID= 45%
SiOz-AlzOJ
amorphous
or Mullitel
cryptocrystalline
PUGK
e.s.d.,; 1 ~m
HCI = 0
Mg(N0 3 )z·6H 2 0(10%)
Si0 2 -Alz0J
amorphous
or
cryptocrystalline
Mullitel
600
650
700
800
900
950
maximum
"spine!"
5%t"spinel"
1000
"spine!"
7%t"spinel"
5%+"spinel"
1050
4%+"spinel"
10%
8%+"spinel"
Cristobalite
Mullite 11
Cristobalite
Mullite 11
1100
8%+"spinel"
5%
40%
5%
25%
Cristobalite
Mullite 11
1200
5%
50%
150%
80%
40%
60%
1250
60%
70%
75%
90%
70%
80%
1300
80%
85%
90%
100%
90%
95%
1400
100%
100%
100%
100%
100%
100%
For symbols see Table 1
gated during and after y-Ab0 3 orAl-Si
spinel and mullite I development.
The relative enrichment in «amorphous>>
or cryptocrystalline Si02 can
be followed by the observation of the
diffuse XRD band localized in the interval
16-32° 28 (CuKa radiation)
which has developed immediately after
dehydroxylation. Its maximum
intensity moves from 23° 2Hat 900 oc
to 21 o 28 at 1200 oc and in this position
the diffraction maximum characteristic
of cristobalite becomes
visible (Fig. 1).

The Effect of Mineralizers, Intercafitd in ... 387
Kaolinites mzneralized
The efficacy of the mineralizer
fixed at the external surface of the
kaolinite crystals is manifest. The
mineralizer allows the anticipated
formation of the kaolinite high
temperature metaphases and phases.
No significant differences were found
when the effects of salt radicals N03,
C3H302 and Cl· were co~pared.
However, VO~- yields superior efficacy
(Table 4).
Nevertheless, the nature of the
TABLE 3
High temperature metaphases and phases developed in a well-ordered kaolinite (SUPK)
either not mineralized or mineralized with Ca(N0 3 )z·4H 2 0 (10%)
SUPK
e.s.d.,;; 1 ~m
HCI = 1.04
SUPK
e.s.d.,;; 1 ~m
HCI = 1.04
HYD+Ca(N0 3 ) 2 -4H 2 0(10%)
ID=. 96%
SUPK
e.s.d.,;; 1 ~m
HCI = 1.04
Ca(N0 3 ) 2 -4H 2 0(10%)
SiOz-AlzOJ
amorphous
or
cryptocrystalline
Mullite I
Si0z-Al 2 0 3
amorphous
or
cryptocrystalline
Mullitei
Si0 2-AlzOJ
amorphous
or
cryp tocrystalline
Mullite I
600
650
700
800
900
950
1000
1050
1100
1200
1250
1300
1400
J
appearance
maximum
Cristobalite
5%
10%
70%
100%
For symbols see Table 1
3%+"spinel"
appearance
j
maximum
appearance
3%+"spinel" maximum
~ ~
,...C:: O.:.:::
8%
·CO "cnca
~en _g~
~ -= e- g
.~ ~ s 15. c
7%+"spinel" ::: E ,"' 6' 10% E 5%+"spinel"
10%
15%
Mullite 11
35%
60%
80%
100%
~------~r-------~ ~ ·c:
Cristobalite Mullite 11 ""'
1----------lr-----------1 .?: c5'
5%
25%
15%
45%
60%
90%
100%
30%
70%
85%
100%
100%
~C/3
~-=·
j
Cristobalite
5%
30%
60%
80%
100%
8%
Mullite 11
35%
55%
75%
90%
100%

388 C. De Sousa Figueiredo Games
cation provides remarkable distinctive lar to that in the specimens not
effects. Mg helps the formation oL~):PJ:Q~I;:tlj~~"d·~-~~,-~,,
y-Ab0 3 or Al-Si spinel metaphases
whereas Ca favours the formation of Kaolinites intercalated a71d mineralized
mullite I (Tables 1 and 3). The effect
of kaolinite structural order-disorder The mineralizer adsorbed simulin
the mineralized specimens is simi- taneously both in the external and in
TABLE 4
High temperature metaphases and phases developed in a well-ordered kaolinite (SUPK)
either not mineralized or mineralized with NH 4·V0 3 (5%)
-----~
600
650
700
800
900
950
1000
1050
1100
Si0z-Alz03
amorphous
or
. cryptocrystalline
appearance
maximum
SUPK
e.s.d . .;; 1 J.lm
HCI = 1.04
Mullitei
3%+"spind"
7%+"spinel"
10%
15%
SUPK
e.s.d.

The Effect of Mineralizers, Intercalated in ... 389
the internal kaolinite crystal surfaces
facilitates much more clearly
the nucleation and the growth of the
high temperature metaphases and
phases regardless of the genetic type
or the structural order-disorder of the
kaolin'i.te. Nevertheless, since the intercalation
is complete or nearly
complete in the well ordered kaolinite
and very incomplete in the disordered
kaolinite, the better accessibility
of the mineralizer into the internal
surfaces in the former makes
its effect more efficient.
The .intercalated mineralizer, for
instance Mg(N03)z · 6Hz0, favours the
anticipation in 100-150 oc approximately
of the kaolinite high temperature
phases mullite II and cristahalite
comparatively with the specimen
not intercalated and mineralized
(Tables 1 and 2).
'-
If the mineralizer has the ability of
promoting early modifications in the
kaolinite tetrahedral or in .the
octahedral sheets, case of NH4V03,
the high temperature phases are
formed at much lower temperatures
(Table 4). The crystallochemical
similarity between SiO~-and VO~groups
and the higher acid character
of V as compared with Si, favours a
" n~at and appreciable anticipation of
the kaolinite thermal reactions. V
substitutes Si in the kaolinite tetrahedral
sheets and promotes the
anticipated disrupture of these
sheets. This helps the segregation of
Si04 groups and their reaction with
Al04 groups and consequently facilitates
. the anticipated formation of
cristobalite and mullite. A metastable
form of cristobalite is formed at
650 °C. It has maximum development
at 800 oc approximately, diminishes
continually up to 1050 oc and disappears
at this temperature. Cristobalite
reappears in a stable form at
1200 °C. Mullite I is formed at 650 oc
simultaneously with the metastable
form of cristobalite, but soon, at 800
oc approximately, it recrystallizes in.
mullite II. The mullite II content increases
continually and acquires its
maximum development at 1100 °C.
Five percent of NHN03 confers a
yellow colour to the fired kaolinite
specimens. However, if the mineralizer
content does not exceed 2%,
the yellow colour is very pale and the
mineralizer efficacy at the 2% level is
nearly as good as at the 5% level.
Tests still going on show that, for
instance in porcelain formulations,
the expected yellow colour confered
by 5% NHN03 is very much attenuated
in comparison with the mineralized
and fired kaolinite specimens.
REFERENCES
BuLENS M., DELMON B., 1977. Kinetic control of the formation of high temperature phases in the
kaolinite~mullite reaction sequence. Bull. Soc. Chim. Belg. 86, 405-411.
BULENS M., LEONARD A.J., DELMON B., 1978. Spectroscopic investigations of the kaolinite-mullite
reaction sequence. J. Am. Ceram. Soc. 61, 81-84.

390 C. De Sousa Figueiredo Games
HINCKLEY D.N., 1963. Variability in «crystallinity» values among the kaolin deposits of the Coastal
Plain of Georgia and South Carolina. Clays Clay Miner. 11, 229-235.
KUPKA F., 197 4. Thermal decomposition o~ kaolinite~ with-TiCh .-and~~20 5 - admixtures, Acta U niv.
Carol., Geol. 1, 25-44.
LEMAITRE J., LEONARD A.J., DELMON B., 1976. Influence of mineralizers on the 950 oc exothermic
reaction ofmetakaolinite. Pp. 539-544, in: Proc. Int. Clay Conf. 1975, Mexico City (S.W. Bailey,
editor), Appl. Pub!. Ltd., Wilmette.
0AKLEY M.J ., SHARP J .H., 1983. The effect of vanadium pentoxide on the thermal reactions ofkaolinite.
Trans. J. Br. Ceram. Soc. 82, 177-182.
WAHL F.M., 1962. Effect of impurities ori kaolinite transformations as examined by high temperature
X-ray diffraction. Advances in X-ray Analysis, Denver, Colo., 5, 264-270.

Miner. Petrogr. Acta
Vol. 29·A, pp. 391-397 (1985)
Infrared Spectra of Nordstrandite
F .. PALMIERI, A. VIOLANTE, P. VIOLANTE
Istituto di Chimica Agraria, Facolta di Agraria, Universita di Napoli, 80055 Portici, Italia
ABSTRACT- Synthetic pure nordstrandite, one of the three polymorphs of
Al(OHh, obtained in the presence of citric or malic acid in alkaline systems,
was characterized by infrared spectroscopy. IR spectra of gibbsite and bayerite
were determined for comparison.
The spectra of nordstrandite exhibited hydroxyl streching bands at 3653,
3621, 3563, 3524 cm- 1 comparable to that found in bayerite at 3653 cm- 1
and to those found in gibbsite at 3623 and 3529 cm- 1 •
A large difference between nordstrandite and gibbsite was observed in the
OH-bending region.
IR spectra of nordstrandite showed evidences that this Al(OH) 3 polymorph
has an intermediate structure between gibbsite and bayerite.
Introduction
Nordstrandite, one of the three
polymorphs of Al(OH)3,_ was found as
a synthetic product mixed with
bayerite and gibbsite (VAN NORD­
STRAND et al., 1956). Later it was·
found in natural environments by
many authors (VIOLANTE et al.,
1982; references herein).
Recently, notdstrandite synthe­
. sized in the absence and in the
presence of montmorillonite
(VIOLANTE & JACKSON, 1979) was
characterized by X-ray and electron
microscopy (VIOLANTE et al., 1982).
The general similarity of the diffraction
patterns of Al(OH)3 polymorphs
and the limited diagnostic value of
their differential thermal curves have
given difficulties in identifying the
synthetic and natural forms of nordstrandite
that probably is «an unrecognized
constituent» in many natural
environments.
The aim of the present work was
the characterization by infrared spectroscopy
of essentially pure synthetic
nordstrandite in order to better identify
this Al(OH)3 polymorph in soils
or sediments as well as to clarify its
\ structural characteristics still imperfectly
known. In view of the suggestion
that nordstrandite consists of a
combination of bayerite and gibbsite
layers sequences, the IR spectra of
these Al(OH)3 polymorphs were determined
for comparison.

392
F. Palmieri, A. Violante, P. Violante
Materials and methods
tigation were pure gibbsite, bayerite
and nordstrandi te. Rectangular paral-
Aluminum hydroxides were pre~ ~ -l~I~pTp~de-~ or;;:~;:ci;t:~~ndite ·.(up ~0
cipitated by adding 0.1 M NaOH with 500 nm) formed in the citrate system
stirring to AlCb solutions in the ab- (Fig. 2), whereas in the malate system
sence or presence of organic acids. the crystals were 350 nm· in size
The final concentration of aluminum (not shown).
was 0.01 M.
Figures 3 and 4 report infrared
Nordstrandite was obtained in the spectra of natural gibbsite, synthetic
presence of citriC acid (Al!citric acid bayerite and nordstrandite.
molar ratio of 10.0) at pH 10.3, and The infrared spectrum of gibbsite
in the presence of malic acid (All (Fig. 3a) exhibits frequencies in the
malic acid molar ratio of 10.0) at pH region between 3623 and 3380 cm-1
10.0. similar to those observed by RUS-
.1
Bayerite was synthesized in the SELL et al. (1974), that are assigned
absence of organic ligands at pH 10.0. to distinct types of hydrogen bond­
Gibbsite was a well crystallized nat- ing: the OH band near 3460 cm- 1 to
urally occurring phase from British hydrogen bonding between adjacent
"--~-··----- Guyana;-- - · layers, the high frequencies at 3529
The samples were aged for 12 cm-1 and at 36l3 cm- 1 to longer bymonths
in polyethylene bottles. drogen bonding between hydroxyls in
Oriented aggregate specimens for X- the same plane. The infrared specray
diffractograms were obtained by trum ofbayerite (Fig. 3b) shows three
drying washed aliquots of suspension bands that correspond to those of
on glass slides. XRD was carried out gibbsite although they are shifted to
with a Rigaku Unit Geigerflex D/MAX higher frequencies, at 3467, 3545 and
II A instrument using CuKa radiation 3653 cm-1 respectively. This can be
and operating at 30 Kv and 20 mA. related to the weakly polarized- by­
Electron micrographs (TEM and Pt/C · droxylionsin bayeriteresultinginlonshadowed
replicas) were obtained ger OH-OH bonds (ROTHBAUER et
with a Philips model EM300 micro- al., 1967). The spectrum of nordstranscope,
according to the procedures dite (Fig. 3c) exhibits hydroxyl
described by VIOLANTE . et al., stretching at 3653, 3621, 3563, 3524
(1982). IR spectra were obtained on a cm-1 comparable to that found_ in
Perkin-El_mer 567 IR grating spec- bayerite at 3633 cm-1and to those
trophotometer after samples prepa- found in gibbsite at 3623 and 3529
ration using the KBr technique. cm-1. In the same spectrum the band
occurring at 3460 cm- 1 in gibbsite
Results and discussion
(Fig. 3a), assigned to hydrogen bond­
. ing between adjacent layers, is
X-ray diffraction patterns (Fig. 1) shifted to a lower frequency (3423
show that the materials under inves- cm- 1 ). This frequency shift can be in-

-- .. --
Infrared Spectra of Nordstrandite 393
4.79
4.33
4.21
Nordstrandite
3.07
45 35 25 15
20 CuKa Radiation
Fig. 1 - X-ray diffraction patterns of synthetic nordstrandite (Al!malic acid molar ratio of 10.0;
pH = 10.0), bayerite and gibbsite.
terpreted as due to an increase in
hydrogen bonding of inner hydroxyls
to those in superimposed layers as
polymer size grows to form a more
stable polymorph with a higher degree
of polymerization. This band
should be considered to arise from inner
hydroxyl groups (ELDERFIELD
& HEM, 1973; FARMER & PAL­
MIERI, 1975).
The OH-bonding frequency of
amphoteric hydroxides depends significantly
on the energy of OH-bonds
linking OH groups. In this region
there is a large difference between
gibbsite (Fig. 4a) and nordstrandite

394 F. Palrnieri, A. Violante, P. Violante
,J40RDSi RANDI TE
~ 40 ru:n
Fig. 2 -Electron miCrographs (TEM and Pt/C replica) of nordstrandite synthesized in the presence
of citrate (Allcitrate molar ratio of 10/0; pH = 10.3).

Infrared Spectra of Nordst~a~dite 395
c
~
b
QJ
u

396 F. Palmieri, A. Violante, P. Violante
c .
b
a
1022
12 10 8 6 4 2 X 100
Wavenumb~r
(cm-1)
Fig. 4- Infrared spectra in the OH-bending region of aluminum hydroxide polymorphs: a, gibbsite;
b, bayerite; c, nordstrandite (Al!malic acid molar ratio of 10.0; pH = 10.0).
OH plane in one unit is superimposed
on another such plane in the
adjacent unit. SCHOEN & ROBER­
SON (1970) suggest that nordstrandite
has an intermediate structure
which is probably a regular interlayering
of the gibbsite and bayerite
modes of stacking containing both
strongly and weakly polarized hydroxyl
ions.
There is a fair measure of agree.­
ment between infrared observations
on nordstrandite and features ex­
. pected from the proposed structur.e.

Infrared Spectra of Nordstra~dite 397
Thus the positions of the two high
frequence bands, at 3653 and 3621
. cm- 1 , are consistent with the presence
of weakly polarized hydroxyl
ions. The decrease of the low frequen~
cy band from 3460 cm- 1 in gibbsite,
to. 3423 cm- 1 should be related to
increased polarization of hydroxyl
ions in the formation of a stable polymorph
such as nordstrandite.
REFERENCES
ELDERFIELD H., HEM J.D., 1973. The development of crystalline structure in aluminum hydroxide
polymorphs in ageing. Mineral. Mag. 39, 89-96.
FARMER V.C., PALMIERI F., 1975. The Characterization of Soil Minerals by Infrared Spectroscopy. Pp.
573-670, in: Soil Components, vol. 11, Springer-Verlag, New York. ·
ROTHBAUER R., ZIGAN F., O'DANIEL H., 1967. Refinement of the structure ofbayerite, Al(OHh, including
some proposals for H-position. Z. K.ristallogr. 125, 317-331.
RUSSELL J .D., PARFITT R.L., FRASER A.R., FARMER V.C., 1974. Surface structure of gibbsite, goethite
and phosphated goethite. Nature 248, 220-221.
ScHOEN R., RoBERSON E.C., 1970. Structures of aluminum hydroxide and geochemical implication.
Am. Miner. 55, 43-77.
VAN NoRDSTRAND R.A., HETTINGER W.P., KEITH C.D., 1956. A new alumina thrihydrate. Nature 177,
713-714.
VroLANTE A., J ACKSON M.L., 1979. Crystallization of nordstrandite in citrate systems and in the presence
of montmorillonite. Pp. 517-525, in: Proc. lnt. Clay Conf. 1978, Oxford (M.M. Mortland and V.C.
Farmer, editors), Developments· in Sedimentology 27.
VIOLANTE P., VIOLANTE A., TAIT J .M., 1982. Morphology of nordstrandite. Clays Clay Miner. 30, 431-
437. ~

Miner. Petrogr. Acta
Vol. 29-A, pp. 399-408 (1985)
Dehydroxylation of Micas and Vermiculites.
The Effect of Octahedral Composition
and Interlayer Saturating Cations
J.M. SERRATOSA, J.A. RAUSELL-COLOM
Institute de Fisico-Quimica Mineral, C.S.I.C., Serrano 115-dpdo., 28006 Madrid, Espaiia
ABSTRACT - Structural OH groups in phyllosilicates have a parti~ular
environment constituted by the octahedral cations to which they are coordinated,
plus the interlayer cation compensating the negative charge of the
silicate layers. In vermiculites and micas (trioctahedral) dehydroxylation
temperatures depend on the OH environment, and the dependance may be
asessed by following the evolution with temperature of the infrared bands
corresponding to the stretching frequencies of the OH groups. ..
Our res).llts show that for vermiculites saturated with K+, Rb+, cs+ and
Ba 2 + (ionic radii >1.3 A), OH groups from unoccupied ditrigonal cavities are
lost at lower temperatures that those from cavities occupied by an interlayer
cation. For vermiculites saturated with Na., Sr". or Ca"' (ioniC radii

400 J.M. Serratosa, J.A. Rausell-Colom
present as Fe 3 +. Llano and Malawi 2. Clear brown phlogopite from
vermiculite have compositions partic- Mannum (Australia)
ularly suited: in these minerals OH 3. Brown phlogopite &;~M~~=-·--
groups are mainly associated to two grave Ranges (Australia)
different environments, i.e. 3Mg and 4. White vermiculite from Llano
2MgAl for the former and 3Mg and County, Texas U.S.A.
2MgFe 3 + for the latter. Therefore, 5. Dark brown vermiculite from
their infrared spectra consist, simply, Kapirikamodzi (Malawi)
of two v H 0
bands assigned to the cor- Chemical analyses for samples 1, 2
responding environments. Upon sat- and 4 have been reported by RAUuration
with different monovalent SELL-COLOM et al. (1965) and by
and divalent cations and subsequent BRADLEY & SERRATOSA (1960).
dehydration,silicatelayersarebrought Samples 3 and 5 were analysed, reto
contact, a mica-like structure is spectively, by AMDL laboratory
· · formed and OH groups are perturb- (South Australia) and by K. Norrish,
ed by the interlayer cations. For the Division of Soils, CSIRO (South Auslow
charge Malawi vermiculite about tralia). Table 1 gives the corresponone
third of OH groups remain un- cling mineralogical formulae.
--~------perturbecf(:RAlYSELCc6L6Met-a.r--_-_-B-otn-vermfciifites have fu11 octahe-
1980; RAUSELL-COLOM & SERRA- dral occupancy. Uano vermiculite
TOSA, 1985).
has Al as the main, and practically
the only, isomoiphous substitution
The aim of this work is to study the -
for octahedral Mg. Malawi vermiculite
has Fe 3 + replacing Mg. The struc­
influence on dehydroxylation resulting
from exchanging interlayer cations
(homoionic vermiculites) while
tural layer charge is high for Llano
vermiculite (0.9 e- per formula unit)
the octahedral environment of OH
and is low for Malawi vermiculite
groups remains constant. For the case
(0.66 e- per formula unit). Octahedral
vacant sites are high for mica 1,
of mica-like K-saturated vermiculites
the observed effects will helpto
medium for mica 3, and'very low for
clarify the sequence of OH loss in·
mica 2. Micas 2 and 3, have nearly
_phlogopites and biotites whose octahedral
composition are more corn-
identical contents of octahedral Mg
and Fe, the former being free from
plex.
octahedral Al. Mica 1 is high in Fe
and Al, and very low in Mg. Ti is high
in micas 1 and 3, and lower in mica 2.
Mineral specimens
Mineral specimens used in this
study were
1. Brown biotite from Quebec
(Canada)
Experimental
Sections 1 cm X 1 cm were cut
form large cleavage flakes, -50 I-LID in

TABLE 1 ~
!}
Mineralogical formulae for micas and vermiculites.
Calcinated samples, 11 oxygen atoms per half formula unit ~
~
Tetrahedral Octahedral Interlayer 6·
;:!
Sample
" .Q,
MICAS
1 2,65 1,35 0,48 0,08 0,17 0,68 1,33 0,02 0,02 2,78 0,04 0,91 0,06 0,01 1,93 R.
2 3,06 -0,88 0,06 0,02 0,09 2,26 0,48 0,02 0,06 2,93 0,02 0,07 0,87 1,01 0,01 0,98 ~
3 2;81 1,19 0,09 0,06 0,16 2,16 0,40 0,01 - 2,88 0,02 0,92 1,12 0,01 0,87 ~
c;·
VERMICULITES
4 2,89 1,11 0,13 0,01 0,03 2,83 - - 3,00 0,45H - - - (2,00) "'
;1
5 2,89 1,04 0,07 - 0,31 0,06 2,63 - - 3,00 0,34H - - - (2,00)
tl1 "'
(H) Ca - saturated ~
("")
;
\:::1
"'
Si 4 + AP+ Fe 3 + Al3+ Fe 3 + Ti 4 + Mg2+ Fe 2 + Mn~+ u+ L oct. Ca 2 + Na+ K+ Mg2+ p- cl- oHis::
c;·
"'
"' ;:!
:::
~
tit
....
~

402 J.M. Serratosa, J.A. Rausell-Colom
thickness, of the different micas, and rated from the membrane and, as for
were used for i.r. absorption determinations
after being heated for 12 temperatures prior to i.r. examination.
hours to temperatures from 300 octo
1000 °C. They were coated with i.r. The i.r. spectra were recorded between
3000 and 4000 cm- 1 with a
transparent fluorolube oil to prevent
the presence of interference bands o­ double beam Perkin Elmer spectro~
verlapping with the absorption bands meter at low recording rates (8
from the specimens.
cm- 1 /min), large time constants (10
Self supporting oriented films of sec), and using wide aperture slits
vermiculite, approximately 100 )liD (0.45 mm). Specimens were placed
in thickness and 2-3 cm in diameter, inclined at 40° to the incident i.r.
were prepared from powdered Nasaturated
samples which were ex­
to particle orientation.
beam to enhance dichroic effects due
changed with propylammonium hydrochloride
solutions and dispersed
in water by ultrasonic shaking. The
dispersion was then filtered in a 0.1 ~m Results
---micropore membrane~the gel allowecr-·--- --------- --- ---
to dry at room temperature and Figures 1, 2 and 3 show the spectra
the resulting vermiculite film made of Llano vermiculite saturated with
homoionic by repeated treatments monovalent and with divalent catwith
1 M solution of the respective ions, after being heated at the tempehydrochlorides,
followed by washing ratures indicated. The evolution with
with distilled water. Upon drying at temperature may be summarised as
50-60 ac vermiculite films were sepa- follows:
3711
V-LlanoK
3708
V - L 1 a no Rb
V -·Llano Cs
3703
3672
3000
3672
Fig. 1- I.R. spectra of oriented films ofV-K, V-Rb and V-Cs heated at various temperatures. Llano
vermiculite.

Dehydroxylation of Micas and Vermiculites~ The Effect ...
403
V- Llano Na
3708
V - Llano Sr
3672
V - Llano Ba
3672
3672
Fig. 2- I.R. spectra of oriented films ofV-Na, V-Sr and V-Ba heated at various temperatures. Llano
· vermiculite.
(i) A decrease of the broad absorption
at the lower frequency side
(vH,o band at 3550-3650 cm- 1 ). The
temperatures at which this band is
finally lost increase as the hydration
energies of the interlayer cations decrease.
(ii) A progressive decrease of the
V- Llano Li
V - Llano Mg
3630
3668
.3750 3700 3650 3600 cm-1
Fig. 3 - I.R. spectra of oriented films of V-Li and V-Mg heated at various temperatures. Llano ·
- vermiculite.

404 J.M. Serratosa, J.A. Rausell-Colom
intensity of the bands in the region
3650-3800 cm- 1 (voH absorption
bands) for temperatures above 650 oc.
At temperatures above 700 oc the
bands at higher frequency (>3900
cm- 1 ) have reduced their intensity
less than the bands at lower frequency
(

Dehydroxylation of Micas and Vermicuzties. The Effect ... 405
goooc
800°C
700°C
600°C
500°C
400°C
3800 3600 3400 3800 . 3600 cm- 3400 3800 3600 cmcm-
1
1 1
3400
Fig. 5 -·I.R. spectra of mic~ flakes heated at various temperatures: q., Mica 1; b, Mica 2; c, Mica 3.
sent, being finally lost at 1000 oc. Mi­
. ea 3 shows an evolution intermediate
between mic;:t 1 and mica 2. At temperatures
between 500~800 oc the in-
.,
tensities of the I and V components
are progressively reduced in an
evenly manner', both bands being lost
at -900 oc. Next, the NA component
is lost at T -1000 oc.
Discussion
Dehydroxylation in vermiculite is
the last stage of thermal-dehydration.
At temperatures of 600-1000 oc one
water mo.lecule is eliminated out of
every two OH groups from the silicate
structure. The morphology of the
mineral is preserved but other properties,
i.e., interlayer hydration, are
irreversibly lost on dehydroxylation.
According to FRIPIAT et al. (1965)
itrri.ay be postulated thatdehydroxylation
takes place by dissociation of
protons from OH groups, followed
by migration to neighbouring OH positions
where they react to form H 2 0,
which is then released from the lattice
by diffusion. At. the temperature of

-,..
I
406 J.M. Serratosa, J.A. Rausell-Colom
reaction protons can migrate within temperatures at which perturbed or
the layer structure but water mole- unperturbed OH _gr()'lJ.~~-yre b_~igg_
culesshoulddiffusealongtheinterlay- lost. It should be pointed, however,
er volume displacing interlayer cat- that the temperature of total deions
from their positions within the hydroxylation is, for u+ saturated
ditrigonal cavities.
vermiculite, at least 150-200 oc lower
According to such scheme the va- than for other homoionic vermiculence
and ionic radii of interlayer cat- lites. This could result from penetraions
become relevant with regards tion of Li+ ions into the ditrigonal
to the ease or difficulty with which cavities towards the OH site what
water migration can occur: cations of would facilitate, both, proton dissolarge
ionic radii should cause greater ciation ~nd water diffusion. Such
steric hindrance than smaller cations process would resemble that of u+
and, for equal ionic radii, divalent penetration at temperatures of 3oocations
should cause less hindrance 400 oc into the layer structure tothan
monovalent cations since there wards vacant octahedral sites in diocis
twice the number of the latter in tahedral phyllosilicates (GONZALEZ
the interlayer volume.
GARCIA, 1949; HOFMANN & KLE-
Our results are consistent with t:he-:MEN,-19"50;--GlAESER & MERING,
above reasoning. As shown clearly in 1967; PROST & CALVET, 1969).
Figs 1 and 2 for vermiculite saturated The octahedral composition of verwith
K+, Rb+, cs+ and Ba 2 ~, OH miculite has also an influence on degroups
not perturbed by cations are hydroxylation. This is best illustralost
at lower temperature than those ted by comparing the spectra of Ma-
1
perturbed by cations: This is more lawi vermiculite and ofLlano vermicevident
in the spectra of V-Ba, where ulite (Figs 1 and 4). In conditions of
only one half of the existing cavities same steric hindrance due to interare
occupied by Ba 2 + ions. The same is layer cations (both K+ saturated) OH
apparent when comparing vermicu- groups are selectively lost at progreslites
of different layer charge (Figs 1 sively increasing temperatures: OH
and 4): OH groups in 3 Mg environ- groups with 2MgFe 3 + environments
ments (unperturbed) are lost in K- from ditrigonal cavities ncit occupied
saturated Malawi vermiculite at tern- by K+ are lost at the lowest temperaperatures
of -500 oc, against 650- ture, followed by the same QH
700 oc for Llano vermiculite where groups from occupied cavities, next
unperturbed OH groups are less by OH with 3Mg enviro~ments from
abundant.
unoccupied cavities and, finally, the
Steric hindrance is less effective same OH from occupied cavities. It
upon saturation with cations of small- may be appreciated that OH groups
er ionic radii (Li+, Na+, Mg 2 +, Sr 2 ~). with 2MgFe 2 + environments in Mala­
From the spectra of Figs 2 and 3 there wi vermiculite are totally lost at ternis
no indication of differences in the peratures of -700-750 oc, in contrast

Dehydroxylation of Micas and Vermiculft~. The Effect ... 407
to OH groups with 2MgAl environments
in Llano vermiculite that
withstand temperatures of 840 oc or
higher, which is consistent with the
known fact that ferric phyllosilicates
have lower dehydroxylation temperatures
than magnesium or aluminium
phyllosilicates. This would indicate
a weakening of the force constant
of OH bonds induced by Fe 3 +
ions, which would allow dissociation
of the proton at lower temperature.
The presence of Fe 2 + in the octahedral
composition of phlogopites and
biotites is of special relevance because
thermally induced oxidation to Fe 3 +
may take place at the expense of OH
groups, with liberation of H2 as reaction
product (VEDDER & WILKINS,
1969):
,·
Fe 2 + +OH-~o= + Fe 3 + + H'-
In view of the low oxidation potential
of Fe2+, dehydroxylation of Fe 2 +
phyllosilicates should proceed at
temperatures lower than for magnesium
or aluminium phyllosilicates
be

i
408 J.M. Serratosa, J.A. Rausell-Colom
termines the ease or the difficulty
with which water molecules formed on
dehydroxylation may diffuse ·along
the interlayer volume. Large interlayer
cations cause more hindrance
than small cations, and monovalent
cations more than diyalent cations
of equal ionic radii, thus resulting
in higher dehydroxylation temperatures.
For u+ saturated vermiculites
lower dehydroxylation temperatures
result, possibly, from thermally activated
migration of the small u+ ions
toward~ OH sites within the cavities,
thus favouring diffusion of the water
molecules formed. Dehydroxylation
in micas proceeds either by Fe 2 + to
by H 20 formation at the expense of
neighbouring OHgroups,-Dr-by-bCJthmechanisms
acting simultaneously.
Thermal dehydroxylation proceeds
selectively according to octahedral
composition. For trioctahedral environments
(N and I) OH stability follows
the sequence
N,I

Miner. Petrogr. Acta
Vol. 29-A, pp. 409-423 (1985)
Perturbation of VoH Infrared Frequencies by
Interlayer Cations in Homoionic Vermiculites.
Structural Implications
J.A. RAUSELL-COLOM, J.M. SERRATOSA
Institute de Fisico-Quimica Mineral, C.S.I.C., Serrano 115-dpdo .• 28006 Madrid, Espafta
ABSTRACT- The position occupied by interlayer cations in vermiculite,
relative to the ·a,b plane has been inferred from the perturbation that they
cause in the stretching vibration of structural hydroxyls.
Replacement by ion exchange of interlayer Mg 2 + by monovalent cations,
followed by dehydration, results in variations of OH stretching frequencies
indicating that interlayer cations are located within the ditrigonalcavities of
the silicate structure in interaction with the octahedral OH groups.
A correlation exists between the observed frequency shifts and the ionic radii
of the interlaye'r cations. For cations of ionic radii larger than 1.3 A, the
frequency shift decreases as the ionic radii increase.
The observed behaviour is best explained by the following assumption relating
the manner in which silicate layers are stacked together: i) large cations
(K+, Rb+, cs+) cause vermiculite layers to be stacked so that ditrigonal rings
of adjacent lay"rs ex'actly superimpose around the interlayer cations. Each
cation occupies the centre of a cavity, immediately above and below two
structural OH grolips. The stretching frequencies of these are perturbed
inversely to the Me-OH distance, and ii) small cations (Li+, Na+) cause
lateral displacements of stacking layers, in order to satisfy their coordination
requirements with oxygen atoms of adjacent surfaces. Cations are still midway
between layers, but occupy positions away from the 0-H bond direc- ·
tion. The stretching frequencies of OH groups above and below are perturbed
depending on both the cation-proton distance and the inclination of the
0-Me vector relative to the OH bond direction.
Introduction
It is well known that the i.r. stretch­
·'ing .frequencies of hydroxyl groups
in mineral structures are affected\
by short range interactions with the
elements that constitute their closet
~nvironment, hence OH groups
are a suitable probe for ascertaining
the chemical nature of such environment
and exploring ordering trends
in the distribution of its components.
In 2:1 phyllosilicates, OH groups
are one third of the anions which
build up the octahedral sheet of the
layer structure. In trioctahedral vermiculites
OH bond directions are perpendicular
to the layer plane; v 0 H
frequencies are, thus, affected by cations
in any of three following categories:
- Interlayer cations compensating
the negative layer charge.

l
410 J.A. Rausell-Colom, J.M. Serratosa
- Cations at the centres of three Materials and methods
Me04 (OH)z octahedra sharing each White vermi~ulite~fcor_n ____ Llano ______
OH group (Me=Mg 2 +, Fe 3 +, AP+, County, Texas (U.S.A.) and dark
Ti 4 i).
brown vermiculite from Kapirikam-
- Cations at the centres of six odzi (Malawi) were selected for the
Me04 tetrahedra forming the ditrigo- experiments because they have chemnal
cavity around each OH group ical compositions that allow a
(Me= Si 4 +, AP+, Fe3+). straightforward interpretation of
Hydroxyl stretching frequencies re~ their (unperturbed) i.r. spectra. Their
suiting from particular octahe&al oc- structural formulae are the followcupancies
have been extensively stud- ing:
ied in micas, kaolinite, talc. and chlorite
by several authors, and the _

Perturbation of voH Infrared FrequencieS by Interlayer ... 411
placed flaf in a specimen holder con:
sisting of a heating stage allowing
measurements at constant temperature
in the range 20-350 oc. Preheatments
at higher temperatures
(500-600 °C) were necessary in occasions
to eliminate interlayer water,
these being performed externally in
an oven. The heating stage in the X­
ray diffractometer was used during
recording to maintain temperatures
sufficiently high to prevent sample
rehydration. In vermiculite, replacement
of interlayer Mg 2 + for K+, Rb +
or cs+ often gives rise to poorly organised,
randomly stacked sequences of
silicate layers, due to residual water
being trapped irregularly in the interlayer
space. The same holds for
Na-vermiculite upon dehydration,
Li-vermiculite retaining wafer even
at temperatures close to deh~droxylation.
In the present study, recording
temperatures and heating pretreatments
were carefully experimented
and selected to yield phases
(anhydrous or hydrated) with rational
dcool) sequences up to high values
of 29 (dcool) ~1 A).
X-ray data from homoionic vermiculites
(anhydrous and hydrated
phases)refertorationaldcool)spacings:
peak positions wererecorded and, for
those phases where electron density
profiles had to be calculated, the corresponding
integrated intensities
were also measured. These were converted
to structure factors Fobs by applying
the appropriate corrections for
absorption and for diffraction geometry
(BRINDLEY . & GILLERY,
1956). A first set of signs for the Fobs
was obtained from the atomic coordinates
(z) and temperature factors (B)
reported by SHIROZU & BAILEY
(1966) for the atoms in the layer structure
of Mg-vermiculite.
I.R. spectra were recorded in the
spectral region 3000-4000 cm- 1 with
a double beam Perkin-Elmer 225
spectrometer, using wide slits (0.45
mm) and slow recording rates (8
cm- 1 /min). A special cell with transparent
CaF 2 windows was used as
specimen holder (ANGELL &
SCHAFFER, 1965) allowing heating
to -600 oc as well as evacuation
(p beam to enhance dichroic effects
due to particle orientation. Also, specimens
may be kept at the desired
state of hydration while spectra are
being recorded by appropriate temperature
pretreatments. Such pretreatments
were always identical to
those applied to' specimens for x~ray
measurement. In order to prevent o­
verlap of V oH and VH 2
o bands, spectra
of hydrated vermiculite phases were
obtained after replacing interlayer
water for D 2 0. When dehydration
required heating at elevated temperatures
(T>200 °C) such replacement
was not allowed because simultaneous
deuteration of structural OH
groups also takes place (RUSSEL &
FRASER, 1971).
Results
Table 1 gives the basal spaCings o£
the various homoionic vermiculites,

I
412 J.A. Rausell-Colom, J.M. Serratosa
TABLE 1
Basal spacings, water content, number. of_d

Perturbation ofv 08 Infrared FrequenCies by Interlayer ... 413
z=5.07 A fbr V-K, z=5.36 A for V-Cs
and z=4.90 A for V-Na is quite unequivocal.
Electron density profiles
for the 11.8 A monolayer hydrate of
Na-vermiculite and for the 12.2 A
monolayer hydrate of Li-vermiculite
have been reported by BRADLEY et
al. (1963) and by MAMY & LE
RENARD (1970). They report the position
of cations at the mid-plari.e of
interlayer space, at z=5.9 A for V-Na
and at z,;; 6.1 A for V-Li. Water molecules
are split in two planes at
z 1 = 5.75 A and z 2 = 6.45 A from the
origin for Li-saturated vermiculite,
and at z 1 = 5.6 A and z 2 = 6.2 A for Nasaturated
vermiculite. The water to
cation ratio is equal to 2 for V-Na and
equal to 2.4 for V-Li.
Figure 2 shows the i.r. spectra from
Mg saturated vermiculite, room tern-
\
p~rature stable hydrated phase~ of
14.3 A for Llano vermiculite and of
14.4 A for Malawi vermiculite. Inter-
layer water has been replaced for
D 2 0. Only two bands are present in
the spectra, one at 3675 cm- 1 and a
second, less intense band, at 3636
cm- 1 for Llano vermiculite and 3620
cm- 1 for Malawi vermiculite. Both
sets of bands show strong dichroism
indicating OH bonds oriented per- ·
pendicularly to the plane of the aggregate,
at right angles to the a,b
plane of the silicate structure. These .
two spectra will serve as reference for
interpreting the changes observed in
the remaining spectra (homoionic
vermiculi tes).
Replacement of Mg 2 + for K+, Rb+
or cs+' followed by dehydration, results
in the following changes: in Llano
vermiculite (Fig. 3) the more intense
band has shifted to 3 711 cm - 1
for V-K, to 3708 cm- 1 for V-Rb and
3703 cm- 1 forV-Cs, with a less intense
band at 3672 cm- 1 dissymmetrically
deformed towards the low frequency "
3675
3675
a
3620
3636
375.0
cm-1
Fig. 2 - Infrared spectra of Mg-verrriiculite (d(Ool)= 14.3 A) in the OH stretching region. D20
replacing interlayer H 2 0 oriented films inclined 45° to the incident beam. a: Llano vermiculite;
· b: Malawi vermiculite.
3750
cm-1

414
3711
J.A. Rausell-Colom, J.M. Serratosa
and 450 oc for V-Li (d(oo 1 )-10A) the
band at .3675 cm- 1 is less intense,
and a new ban

Perturbation of V oH Infrared Frequencies1iy- Interlayer ... 415
3668
Fig. 4- Infrared spectrum K-saturated Malawi vermiculite. Oriented film preheated to 500°C.
to interlayer occupancy. According to
SHIROZU & BAILEY (1966) int~rlayer
Mg 2 + ions in vermiculite (14.3 A
phase) are located over the bases .of
Si0 4 tetrahedra, separated from the
silicate surface by one layer of.water
molecules, and, therefore, too distant
apart from the OH groups . to influence
their vibration. The fact that the
v 0 H frequency assigned to OH associated
to 3Mg coincides with that in
the spectrum of talc, a mineral with-
3675
11
I'
I * I
I I
I
I I
3695/ \ _,....._~
...V ~.
' I .£"3636'-·-
V I \J \ - ....... ~....... .
i : ' .......___ ........_,
_j_ I
-------~--'::.::::_·-·-·-·-
3800 3500 3400 3300
3100 cm-1
Fig. 5 -Infrared spectra of Li-saturated Llano vermiculite.
--;--oriented film preheated to 450 oc;
-·-·-·oriented film preheated to 550 oc (dcoo1)=9.4 A);,
----oriented film at room temperature (dcool)= 12.2 A);
0 2 0 replacing interlayer H 20.

416 J.A. Rausell-Colom, J.M. Serratosa
.
1 I
\ i i 3636
V "!A ....--....-----.....
I ,, it."' . .......................,_
I. '· ....................
------------ ..... ._...
. ------ ...........
~ - ---
3800 3700 3600
c
Fig. 6- Infrared spectra of Na-saturated Llano vermisulite.
---oriented film preheated to 80 ·c (d(Ool)=9.8 A);
-·---oriented film preheated to 550 oc (d(ool)=9.8 A);,
-·-·~·oriented film at room temperature (d(ool)= 11.8 A);
D20 replacing interlayer H20.
out interlayer cations in the structure,
is consistent with the above reasoning.
The influence of interlayer cations
is best felt by OH groups in the absence
of interlayer water when the
size of the cations, relative to the dimensions
of the ditrigonal cavities in
the silicate structure, predisposes layer
stacking arrangements as in phlogopite,
where every K+ is located
within two ditrigonal cavities in
adjacent layers (STEINFINK, 1962).
This is the case for V-K, \'-Rb and V­
Cs: the electron density profiles of
Fig. 1 show the ions at the mid-plane
of the structure, and with the thickness
of the interlayer volume (dcool)
= -9.4 A) being in every case smaller
than twice the dimension of the respective
ionic radii (Table 1) there is
no space to accomodate the interlayer
cations otherwise. Each cation is,
thus, located immediately above and
below two OH groups, in condition to
perturb the valence vibration of the
same. This is apparent from the spectra
of Figs 3 and 4. In Llano vermiculite
the band from OH in 31\1g environment
appears now at 3711 cm-1,
at the same frequency as that reported
by VEDDER (1964) and WIL­
KINS (1967) for OH groups with 3Mg
environment in phlogopite (v 0
H =
3712 cm- 1 ). The band has shifted ,1v
= + 36 cm- 1 relative to the uqperturbed
band in Mg-vermiculite. Because
of the high layer charge of this vermiculite
(0.9 e/half unit cell), the perturbation
affects to-.90% of the structural
OH so that a weak unperturbed band
at 3675 cm- 1 should remain in the
spectrum overlapping with the band
at 3672 cm- 1 from OH groups in

Perturbation of voH Infrared Frequenczes by Interlayer ... 417
2MgAl environment perturbed by
K+. The shift resulting from perturbation
by Rb+ and Cs+ are of Llv =
+33 c;m- 1 and Llv = +28 cm- 1 , respectively.
The same is observed for
Malawi vermiculite: with a smaller
layer charge than Llano vermiculite
(0.66 e!half unit cell), only two thirds
of the OH groups are perturbed by
K+, and the spectrum in Fig. 4 shows
a band from unperturbed OH groups
with 2MgFe 3 + environments at 3620
cm - 1 , ~ second band from perturbed
OH groups with 3Mg environments
at 3712 cm- 1 and a third band at
3668 cm- 1 resulting from the overlap
of those from unperturbed 3Mg and
from perturbed 2MgFe 3 + hydroxyl
groups.
Figure 7 gives the relationship between
the observed frequency shifts
and the distance from the i 1 ~terlayer
. ~
catiOns to structural OH groups, de-
,_ rived from the X-ray data (Table 1).
Included are frequency shifts from
VoH frequencies reported by SERRA­
TOSA et al. (1970) for oetylammonium
vermiculite complexes with
dcool) spacings of 19 A and 28.1 A, and
NH! ... HO distances ·reported by
JOHNS & SEN GUPTA (1967) from
electron density profiles of the same
complexes. The same Llano vermiculite
material as for the present study
was used.The inclusion of this data is
justified from the fact that in such
complexes, - NH! radicals at the end
of alkylammonium chains, have the
same ionic radii asK+ and are keyed,
too, into the ditrigonal cavities of the
silicate structure. It is apparent from
Fig. 7 that, for ions of the same charge
occupying identical positions on
the silicate surfaces, the perturbation
induced on the VoH vibration is in~
versely related to the cation-OH dis 1 -
tance, such distance being determined
by the ionic radius of the saturating
cation.
A full interpretation of the i.r. spec-
' E
u
:I:
.,.o
3. 5
4.0 4.5
Distance OH-- Me+ (A)
Fig. 7 - Relationship between V oH wave numbers and Me+ ... OH distances for Llano vermiculite
saturated with various monovalent cations.

418 J.A. Rausell-Colom, J.M. Serratosa
tra of the dehydrated phases of Li+ found in differences in the manner
and Na+ saturated vermiculite is not with which adjacent layers stack tostraight
forward due to overlap ofthe gether to trap~i:Iie-ions within'i:h.e cav­
VoH bands with the strong absorp- ities at the midplane of the struction
bands of residual water. Never- ture. The radius of the cavity being 1.3
theless, the perturbation due to the A, cations of the same or larger ionic
interlayer cations is quite conspic~ radii would rest upon the oxygen
uous at the high frequency side of atoms in positions centered to the
the spectra (Figs 5 and 6), resulting in r:ing, facing directly the OH groups
frequency shifts of Liv= +33 cm- 1 for belowandabove.Forcationsofsmall­
V-Na (dcoo1=9.8 A) and of Llv=+lO · er ionic radii (Li+, Na+) the volume
'cm- 1 for V-Li (dcoo1 = 9.2 A) for OH available within two cavities is larger
groups in 3 Mg+ environments. than the cation volume, so one would
It is apparent from Fig. 5, ,spec- expect displacements of opposite
trum of sample heated at 550 oc, that layers to accomodate the interlayer
the ratio of the intensities at 3708 cations in the manner best suited
and 3675 cm- 1 is, approximately, the to satisfy the coordination requiresame
as for the spectra of V-K: V-Rb ments of the cation with oxygen
~- -----~- -and-V-Cs-in-Fig;-3-:-This=wou-I-d-rn-di=----atoms-from the two surfaces. Accordcate
that as for the latter vermiculites ingly, cations would be laterally diseach
Na+ ion in V-Na perturbs the placed relative to the 0-H bond divibration
of two OH groups which, in rection of hydroxyl groups above and
turn, is indicative of Na+, ions being _ below and, even with smaller dcool)
located within the space formed by spacings, the effective repulsion expairs
of ditrigonal cavities in adja- erted on the proton by the interlayer
cent layers. Again, the recorded dcool) cation can be considerably reduced
spacings prevent alternative arrange- depending on cation inclination and
ments. Measured in terms of the screening by surface o:x.ygens.
induced frequency shifts the magni- Obviously, the sma1ler the cation the
tude of the perturbation shows, how- larger the displacement and the
ever, a trend opposite to that ob- smaller the perturbation on voH·
served forthe large interlayer cations Figure 8 illust.rates layer stacking
(K+, Rb+, Cs+) i.e., despite of the modes for the different anhydrous
smaller dcool) spacings and, there- phases, consistent with the observed
fore, of smaller expected cation-OH v 0 H perturbation. In Fig. 8a (V-k, V­
distances, the small Li+ ions perturb Rb and V-Cs) ditrigonal cavities in
OH vibrations less than the large adjacent surfaces are stacked face to
Na+ ions, the values for Llv increasing face. Such disposition is actually
now with ionic radii.
found from crystal structure determi-
The reason why cations with appar- nations in phlogopites and biotites
ently identical locations cause per- (STEINFINK, 1962). For Na+ satuturbations
of opposite trends may be ratedvermiculiteadisplacementofdi-

V-K,V-Rb
V - Cs
a
b
V - L i
.::1 = - a/3
c
Fig. 8- Layer stacking modes for anhydrous phases of Llano vermicu!ite .
. a: V-K, V-Rb and V-Cs; .
b: V-Na;
c: V-Li.
/ .0. = Displacement of ditrigonal cavities in adjacent layers
----Upper layer;
---Lower layer.

420 J.A. Rausell-Colorn, J.M. Serratosa
trigonal cavities ofa/3 (Fig. Sb) leaves dom sequence of translations of
Na+ ions in six-fold coordination +0.307b,Oand_=Q_J()7'1£_The_r:s:.sult::_
with three oxygen atoms from each. ing interlayer configuration is illussurface,
with resulting Na ... o= dis- trated in Fig. 9a, showing Na+ ibns
tances of 2.52 A and of 2.64 A. For in six-fold coordination with two sur­
Li+ saturated vermiculite, a displace- face oxygen atoms and four water
ment of -a/3 (Fig. Se) leaves Li+ molecules, with Na ... OcH
2
o) distances
ions in four-fold coordination with of 2.59 A. The location of Na+ ions is
two oxygen atoms from each surface, sufficiently distant apart from the OH
the Li...o= distances being 2.06 A. groups at the centres of the cavities
The last two configuratiOJ?.S are equiv- to prevent V oH perturbation.
alent to those proposed for vermicu- For the 12.2 A phase of Li-vermicu-_
lite saturated with divalent cations of lite, X-ray diffraction data by MAMY
equal ionic radii (9.78 A phase ofV-Sr &"LE RENARD (1970) consisting of
byRAVSELL-COLOMetal., 1980; 9.02 integrated intensities for 24 observed
A phase of V-Mg by WALKER 1956). (001) rational reflections have afford-
Upon.·hydration, interlayer cations ed those authors an electron density
in V-Li and V-Na are extracted from proyection along z* allowing resolu-
-----------------their-:[5osi1ionsw11nin.·r:nedilfigonar· -ii0il-0fo.51 ~r better, in which two
cavities and placed away from the_ well resolved peaks are shown, 0.6 A
vicinity of OH groups. The absence of apart, for the surface oxygen atoms
v0 H perturbation in the corn~spon- and for tetrahedral Si,AL Despite
din~ monolayer hydrates prevents that, a broad peak at z = 6.1 A was
any conclusion to be drawn from i.r. interpreted by the authors as due to
data with respect to the positions oc- four water molecules in ·two planes,
cupied by cations and water mole- 0.7apart,atz=5.75Aandz=6.45A,
cules in the a,b plane of the structure. and to Li+ ions at the mid-plane of
Crystal structure determinations by the structure. One would expect Li+
conventional X-ray methods are im- ions to be in four-fould coordination,
practicable because the absence of with Li ... O distances of 2 A, which
long range regularity in the layer can hardly be achieved from the restacking
sequence is a characteristic ported positions for water and catof
these hydrated phases (DE LA ions unless a considerable flattening
CALLE et al., 1985). of the Li coordination polyhedr~ is
For the 11.8 A hydrate of Na-ver- admitted. Alternatively, the electron
miculite DE LA CALLE et al. (1984) density peak at z = 6.1 A could be inreport
diffuse layer lines for all reflec- terpreted by allocating all water moltions
other than (h 0 1) in Weissen- ecules in one plane at z = 6.1 A and
berg diagrams. By analysing the in- Li+ ions in two planes at z = 5.3 A and
tensity modulation along those lines, 6.9 A. In fact, the electron density
the above authors propose a layer profile to be expected from such disstacking
model consisting of a ran- position would match very closely

Perturbation of VoH Infrared Frequencies7)y Interlayer ... 421
V - Na
L1 = - a/3. o.3o7b'
V - L i
J = D.32 b
Fig. 9 - Layer stacking modes for one layer hydrates of Llano vermiculite.
a: Na-saturated (Dcooi) = 11.8 A);
b: Li-saturated (dcooo = 12.2 A);
~ ~ Displacement of ditrigonal cavities in adjacent layers
---- Upper layer;
--- Lower layer.
to the one reported. See for comparison
the shape of the peak for 3H 20 at
z = 6 A in the electron density projections
for the expanded phases of
V-Li, V-Na and V-Ca by the same
authors.
Should the second interpretation
be the right one, i.e., water in one·
plane at 6.1 A. and u+ in two planes
at 5.3 A and 6.9 A, then the configuration
of molecules and cations in the
interlayer volume would be straight

T
422 J.A. Rausell-Colom, J.M. Serratosa
forward. Figure 9b shows Li+ ions
tetrahedrally coordinated to one
oxygen a tom from one surface and to
three water molecules, on top of
oxygen atoms from the adjacent surface,
arranged in the same manner as
each one of the water layers in the
14.3 A phase of Mg-vermiculite (SHI­
ROZU & BAILEY,J5L6_6J._Acl1ac::em_di-___
trigonal cavities are displaced 0.32 b.
Distances Li...O are of 2 A, and distances
Li ... OH 2 are or 2.1 A. No perturbation
of OH groups should result
from such disposition.
REFERENCES
ANGELL C.L., ScHAFFER P.C., 1965. Infrared spectroscopic investigations of zeolites and adsorbed
molecules. Structural OH groups. J. phys. Chem. 69, 3463-3470.
BASSETT W.A., 1960. Role of hydroxyl orientation in mica alteration. Geol. Soc. Am. Bull. 71, 449-45.6.
BRADLEY W.F., WEISS E.J., ROWLAND R.A., 1963. A glycol-sodium vermiculite complex. Clays Clay
Miner. 10, 117-122.
BRINDLEY G.W., GILLERY F.H., 1956. X-ray identification of chlorite species. Am. Miner. 41, 169-186 .
. CHAUSSIDON J., 1973. Le spectre infrarouge des~biotites: Vibrations d'elongation basse frequence des
OH du reseau. Pp. 99-106, in: Proc. Int. Clay Conf. 1?72, M_adrid(J.M. Serratosa, editor),
--------- ----------·cs:I:c:,""Maarill:--- ---------- ------ ---- ·· -- · ··
DE LA CALLE C., PLAN«;:ON A., PoNs C.M., DUBERNAT J., SuouET H., PEZERAT H., 1984. Mode d'empilement
des feuillets dans la vermiculite Na hydratee a une couche. Clay Minerals 19, 563-578.
DE LA CALLE C., SUQUET H., PEZERAT H., 1985. Vermiculites hydratees a une couche. Clay Minerals 20,
221-230.
FARMER V.C., 1964. Infrared absorption of hydroxyl groups in kaolinite. Science 145, 1189-1190.
FARMER V.C., RussELL J.D., 1967. Infrared absorption spectrometry in clay studies. Clays Clay Miner.
15, 121-142. r
JoHNS W.D., SEN GuPTA P.K., 1967. Vermiculite-alkylammonium-complexes. Am. Miner. 52, 1706-
1724.
Juo A.S.R., WHITE J .L., 1969. Orientation of the dipole moments of hydroxyl groups in oxidized and
unoxidized biotite. Science 165, 804-805.
MAMY J., LE RENARD J., 1970. Contribution a I' etude de la structure de l'espace interfeuillet des micas
alterees. Pp. 17-20, in: Proc.R.euni6n Hispano-Belga de Minerals de la Arcilla (J.M. Serra:tosa,
editor), C.S.I.C., Madrid. ' v
RAUSELL-COLOM J.A., SANZ J., FERNANDEZ M., SERRATOSA J.M., 1979. Distribution of octahedral ions
in phlogopites and biotites. Pp. 27-36, in: Proc. Int. Clay Conf. 1978, Oxford (M.M. Mortland and
V.C. Farmer, editors), Developments in Sedimentology 27.
RAUSELL-COLOM J.A., FERNANDEZ M., SERRATOSA J.M., ALCOVER J.F., GATINEAU 1., 1980. Organisation
de l'espace interlamellilire dans des vermiculites monocouches et anhydres. Clay Minerals 15,
37-58.
ROUSSEAUX J.M., GOMEZ LAVERDE C., NATHAN Y., ROUXHET P.G., 1973. Correlation between the
hydroxyl stretching bands and the chemical composition of trioctahedral micas. Pp. 89-98, in:
Proc. Int. Clay Conf. 1972, Madrid (J.M. Serratosa, editor), C.S.I.C., Madrid.
RussELL J.D., FRASER A.R., 1971. I.R. spectroscopic evidence for interaction between hydronium ions
and lattice OH groups in fnontmorillonite. Clays Clay Miner. 19, 55-59.
SERRATOSA J.M., BRADLEY W.F., 1958. Infrared absorption of OH bonds in micas. Nature 181, 111.
SERRATOSA J.M., HIDALGO A., VINAS J.M., 1962. Orientation of OH bonds in kaolinite. Nature 195,
486.
SERRATOSA J.M., JOHNS W.D., SHIMOYAMA A., 1970. Infrared study of alkyl-ammonium vermiculite
complexes. Clays Clay Miner. 18, 107-113.
SERRATOSA J.M., VIN:As J.M., 1964. Infrared investigation of the OH bonds in chlorites. Nature 202,
999.
SHIROZU H., BAILEY S.W., 1966. Crystal structure of a two layer Mg-vermiculite. Am. Miner. 51, 1124-
1143.
STEINFINK H., 1962. Crystal structure of a trioctahedral mica: phlogopite. Am. Miner. 47, 886-896.

Perturbation of VoH Infrared Frequenci-es- by Interlayer ... 423
VEDDER W., 1964. Correlations between infrared spectrum and chemical composition of mica. Am.
Miner. 49, 736-768.
WALKER G.F., i956. The mechanism of dehydration of Mg-vermiculite. Clays Clay Miner. 4, 101-105.
WrLKINS R.W .T ., 1967. The hydroxyl-stretching region of the biotite mica spectrum. Mineral. Mag. 36,
325-333.
WILKINS R.W.T., !To J., 1967. Infrared spectra of some synthetic talcs. Am. Miner. 52, 1649-1661.

Abstracts
425
Dependence of Chemistry on Genesis in Zeolites:
Multivariate Analysis of Variance and
Discriminant Analysis
A. ALBERTI, M.F. BRIGATTI
Istituto di Mineralogia e Petrologia, Universita di Modena, LargoS. Eufemia 19,41100 Modena, Italia
This work was undertaken in order to establish the presence of correlations
between genesis and chemical composition in zeolites. It is a well known fact
that the chemical composition of a mineral depends on thermodynamic
conditions and genetic environment of growth, while it is a problem to
establish which chemical elements and to what extent, are affected during
growth, and how they interact. Multivariate analysis of variance and discriminant
analysis were used to tackle this problem. Three hundred and three
chemical analyses of the mineralogical families: heulandite, chabazite, erionite,
phillipsite and analcime, 164 of hydrothermal and 139 of sedimentary
genesis respectively were considered. For each of them, 10 chemical elements
(Na, K, Mg, Ca, Sr, Ba, Fe 3 +, AI, Si, H 2 0) were taken into account. The
results indicate that for the five families considered a strong chemical boundary
exists between hydrothermal and sedimentary zeolites, and, in fact, '
only 5% of the samples were incorrectly classified with regard to their 1
genetic groups .. Conversely, these results show the power of these statistical
methods for problems of classification and discrimination. The ability of the
elements to discriminate between the two genetic groupings differs for the
different families. For example, while the Si/A! ratio is generally an important
discriminating factor, the weight of the other elements, in particular
Ca, H 2 0, and Mg, varies for the different families. Among the 10 elements
considered in this study, there is no proof of influence by genesis in Na only.
Discriminant analysis for the s'amples classified into two groups on the basis
of genesis only, disregarding the different families, classifies 83% of the
samples correctly. The analysis of variance justifies this high number of
incorrectly classified samples compared with the number found when the
families are considered separately as the presence of a strongly significant
interaction between geneses and families shows. Only Sr does not seem to be
affected. Finally, the high significance of the discriminant functions provides
a satisfactory criterion in identifying the genetic grouping of new unclassified
samples.

426 Abstracts
Differences of Crystal Chemistry in Al-Rich
Smectite Types: Multivariate A:nalysis~uf~,
Variance and Discriminant Analysis
A. ALBERTJI, M.F .. BRIGATTJI, L. POPPF
1 Istituto di Mineralogia e Petrologia, Universita di Modena, LargoS. Eufemia 19, 41100 Modena, Italia
2 Istituto di Mineralogia e Petrografia, Universitadi Bologna, Piazza di Porta S, Donato I, 40127 Bologna, Italia
It is well known that the physico-chemical properties of smectites (such as
cation exchange capacity, thermal behaviour, reactions to physico-chemical
treatments, etc.) can differ widely; these differences have been used to characterize
the different species and/or types of smectites. The end members of
montmorillonite-beidel!ite series, for example, were distinguished by the Li~
test proposed by Greene-Kelly (1953). Grim & Kulbicki (1961) emphasized
the presence of two different montmorillonites (Cheto- and Wyoming-type)
on the basis of cation exchange capacity, thermal behaviour, reaction to K­
and Mg-treatments, and firing products. Schultz (1969) keeps the term Wyoming-type
as jn Grim & Kulbicki (1961) but subdivides Cheto-type samples
into Otay-, Tatatilla-, and Chambers-type having different DTA curves, firing
products, and behaviour after K- treatment; the same author also introduces
_the, term, .o

Abstracts
427
The Influence of Chromium (Ill) on the Crystallization
of Iron Oxides at Low Temperature
J. BARRIOS, J. TORRENT
Departamento de Edafologia, E.T.S.I.A., Alameda del Obispo, Apdo. 3048, 14071 C6rdoba, Espafta
Plants grown in soils having low amounts of available Cr have a low content
of this element and, consequently, animals feeding on them can develop
some deficiency symptoms because Cr has been shown to be essential for the
glucose metabolism in animals.
Chromium is present in soils in both Cr (Ill) and Cr (VI) compounds, whose
relative proportions depend on several factors including, especially redox
conditions. Plants seem to take Cr as the Cro~- ion, thus the formation of the
highly insoluble Cr (III) compounds renders Cr relatively unavailable to
plants unless some supply of Cro~- is assured.
Inasmuch as Cr (Ill) seems to be usually occluded in iron oxides we undertook
research to see the effect of Cr (Ill) on crystallization a:t low temperatures
(t :5 100°C) of synthetic Fe oxides as well as to know the form in which
Cr (Ill) is present in the synthetic er-containing Fe oxides. We report here the
effect of Cr (Ill) on the crystallization of Fe oxides.
In our experiments we started by coprecipitating protoferrihydrite and Cr
(Ill)-hydroxide (from the nitrates, using NH 3 ) such that the molar ratio Cr/Fe
+ Cr ranged from 0 to 30%. The precipitates were stored for 50 days at 55 or
100°C and at pH 7 or pH 10. In the final products we calculated the proportions
of goethite and hematite by comparing the areas of the peaks of their X­
ray diffractog,ams with the areas of appropriate external standards.
As the ratio Cr/Fe + Cr increased the crystallinity of the final crystalline Fe
oxides, as evaluated from the width at half height of their X-ray diffractograms,
decreased and the proportion of crystalline Fe oxides in the final
product also decreased. ·
The goethite/hematite ratio increased with increasing Cr content. At this
point the effect of Cr (Ill) seems to be the opposite to that of AI (Gastuche et
al., 1964) even though both cations have ionic radii smaller than that of Fe
(Ill).
Increasing the temperature of storage favoured hematite over goethite. Hematite
was favoured over goethite by increasing the pH from 7 to 10, in contrast
with pure Fe systems (Schwertmann & Murad, 1983).
Gastuche M.C., Bruggenwert T., Mortland M.M., 1964. Crystallization of mixed iron and aluminium
gels. Soil Sci. 98, 281-289.
Schwertmann U., Murad E., 1983. Effect of pH on the formation of goethite and hematite from
ferrihydrite. Clays Clay Miner. 31, 277-284.

I
I
428 Abstracts
Mossbauer Study of the Spontaneous
Alteration of H-Bentoriite--
i
C GESSA 1 , P. MELIS 1 , V. SOLINAS 1 , N. BURRIESCF, M. PETRERA 3
1 Istituto di Chimica Agraria, Facolta di Agraria, Universita di Sassari, Via E. De Nicola, 07100 Sassari, Italia
2 Istituto di rucerche sui Metodi e Processi Chimici per la Trasformazione e l'Accumulo deli'Energia, C.N.R., Via
Salita S. Lucia 39, Pistunina, 98!00 Messina, Italia
3 Laboratorio Montedison «G. Donegani», Via Fauser 4, 28!00 Novara, Italia
Mossbauer spectroscopy was used to study the displacement by protons of
Fe 3 + from the octahedral layer of H-montmorillonites. Two clays collected
from quarries at Costa Paradise, Sardinia, and the well known Wyoming
bentonite were subjected to dialysis and the Mossbauer spectra were recorded
on the samples after different dialysis times. The observed decrease of
the relative trans- to cis-Fe 3 + resonant absorption area was interpreted as a
preferential displacement of the trans-coordinated form. This effect can be
connected with different bond-strengths for the two sites but different stabilities
of the intermediate iron forms during the substitution process also
could play a role.
The selective substitution of trans-Fe 3 + supports the model based on H+
diffusion through the planar surfaces proposed by Shainberg et al. ( 197 4) for
------meTransforhiafior'i'ofH- and Nacmontmorillonite to Al-montmorillonites in
water. The hydrolysis of two clays follows a parabolic rate law, indicating a
prevalence of the Fe 3 + substitution reaction by protons. The third clay
exhibits a more complex behaviour which is attributed to a lower structural
stability.
Iron distribution in H-bentonites before'and after 155 days of dialysis
sample Fe Fetrans Fecis
0
sample Fe, Fetrans Fecis ~etrans .6.Fecis ~Fe
A1/A 2
A1/Az
mg mg mg .mg ~Fe ~Fe Fe 0
Wyoming 250 6.87 0.78 3.01 3.86 212 4.88 0.34 1.24 3.64 0.89 0.11 0.29
White C.P. 250 6.27 0.58 2.30 3.97 218 4.93 0.28 1.08 3.85 0.91 0.09 0.21
Red C.P. * 250 7.40 0.70 3.05 4.35 235 5.8o+ 0.36 1.54 4.26 0.94 0.06 0.22
* after 40 days of dialysis
+ determined after extraction of the oxide fraction by sodium dithionite both before and after
dialysis
AI and Mg distribution in Wyoming clay before and after dialysis
before dialysis
after dialysis
--
sample Alo M go sample AI, Mg, M! llMg
mg mg Alo M go
250 31.15 4.85 212 24.86 3.10 0.20 0.36
x 0 (x = Fe,Al,Mg) = amount of the cation at zero days of dialysis
x, (x = Fe,Al,Mg) = amount of the cation at t days of dialysis; t = !55 d
~
Shainberg I., Low P.F., Kafkafi U., 1974. Electrochemistry of sodium-montmorillonite suspensions:
I. Chemical stability of montmorillonite. Soil Sci. Soc. Amer. Proc. 38, 751-756.

Abstracts 429
Grinding Effects on Crystallinity and
Standard Free Energy of Kaolinite
A. LA IGLESIA
Divisi6n de Elementos Combustibles y Estructurales, Junta de Energia Nuclear, Ciudad Universitaria, 28040
Madrid, Espafta
~G 0 f values for several kaolinite samples are reported as a function of particle
size and crystallinity. The results are discussed in the light of several
processes originated by the grinding.
For the present study two different kaolinite samples from Province of Cuenca
(Spain) were used: samples PS and V corresponding to Perpetuo Socorro
and Valdecabras Wealden deposits, respectively. Following the Murray &
Lyons (1956) classification, the former can be considered as a well crystallized
kaolinite showing crystals of an average size of about 1 Jlm, specific
surface (ES) of 7.4 m 2 /g and a Hinckley (1963) index (H) of 1.2. On the other
hand, sample V was an ordered kaolinite with an irregular morphology and
whose average crystal size was.0.3 Jlm; the rest of the above parameters were
as follows: ES = 8.0 m 2 /g and H = 1.0. Each of these two samples was treated
with a (tungsten carbide) ballon-grinder up to twelve hours.
Particle size measurements \Vere made by X-ray diffraction (Scherrer
method) and electron microscope analyses. Crystallinity was monitored by
X-ray diffraction using two methods: (a) Hinckley index and (b) internal
standard.
~Gof values were obtained measuring the silica and aluminium concentration
and the pH of solutions in equilibrium with (normal or ground) kaolinite
samples at T = 298°K.
Figures 1 and 2 show:_ ~G 0 f as a function of the crystallinity percentage
(%C) and specific surface (SE), respectively. Note how both samples increase
their ~G 0 f as SE diminishes accompanied by an amorphous behaviour to
X-ray diffraction. It should be noted that the present ~Gl value of -897
kcallmol agrees well with that of Hem et al. (1973) for an amorphous gel with
a composition similar to that of kaolinite. Fig. 1 also shows how crystallinity
only appears within a narrow range of ~Gl, i.e., from -902.5 +1.1 and
-896.5 +1.1 kcallmol and consequently a short range of SE values would.
-902
0 :900
~
~
u ""
~
'-' ~893
04-
(!}
""'
10 40 60
Crystallinity (%C)
Fig. 1

T
430 Abstracts
also correspond to this crystallinity interval. This is shown in Fig. 2 from 7 to
25 m 2 /g. The last SE value is close to other poorly crystallized, almost
amorphous, kaolinite determinations.
-~~--~-~-___ ..... ___
(
-902
0 -900
E
---...
"' u
~
04- -898
'

Abstracts 431
Raman Spectra of Layer Silicates
A.HIDALGO,M.SANTOS
Instituto de Optica «Daza de Valdes>>, C.S.I.C., Serrano 121, 28006 Madrid, Espaii.a
Raman spectroscopy has developed rapidly in the last years. The fact that a
stable high-energy coherent source of radiation - the laser - is now a
routine part of Raman instrumentation, more than any other single factor,
has provided new impetus for continuing rapid growth in this area of
spectroscopy.
Although Raman spectra give new and complementary information to infrared
spectroscopy, no much attention have received by clay scientists.
In this work we present the Raman spectra of natural samples of talc,
kaolinite, dickite, muscovite, lepidolite, pyrophyllite and margarite.
In the high frequency OH stretching vibration region quite good spectra are
obtained, confirming the assignations done from the infrared data. Some of
the samples give also good spectra in the 30-200 cm- 1 region which are
complementary to those obtained recently by far infrared specfroscopy.
X-ray Diffraction Intensity of Mixed Layer Clay Minerals.
Some Theoretical Considerations on Mixing Function

432 Abstracts
The diagram shows the relationships existing among C1, C 2 , p and D.
0.5
I
\
\
\
\
\
'o
I \1
,o ,..,
\,.
\
I
\
\
I
5b
\"r5'
\
\
I
------
a;
'
.,._
' '
' '
' '
' '
' ' ' ' '
-- ........ ,,
----.:-.:-_:: ~~~
' 0
' 11
-- .................. ~,~'
0.5
C1 values are taken into account as follows:
1) 17.8 A= smectite glycerol treated;
2) 15.0 A = smectite with two water layers;
~ 14.2 A = chlorite;
4) 12.5 A = smectite with one water layer;
5) 10.0 A = illite or dehydrated smectite.
C 2 values are constantly changed:·
1) from 0.0 to 17.0;
2) from 0.0 to 14.0;
3) from 0.0 to 12.5;
4) from 0.0 to 11.0;
5) from 0.0 to 9.0.
I .
Kaolinite with a translation of 7.15 is taken as C 2 •
Graphs show curves of migration of maxima switching from a rectangular
hyperbola to a sinuxoid to a straight line. ,
In the graphs we can note two zones: the first called «unreal zone>> and the
second «real zone». The second one comprises all the true interstratifications,
but the two zones are strictly bounded since the curves of the real zone
are the continuations of the unreal ones.
Figure 1 shows that in the case. of p = 0.1, the curves are independent of D
and are branchs of a rectangular hyperbola with equation sC 2 = K. ·
In Fig. 2 (p = 0.5) the equation of the hyperbola is instead (C1 + C 2 )s = K.
When D ~ 1.0 the curves become sinuxoidal, mostly for low values of s as
shown in Fig. 3.
Lastly (Fig. 4), when p = 0.9 the curves are independent of D and are parallel
to the abscissa (C 2 ).

-
c 1 :17.8 p:O .. 1 0:0.0+1.0
q:r7.8 p:0.5 0:0.2
.5
s
Unrea 1 Zone
I
I
:Rea 1 Zone
s Unreal Zone
.5
I
I
:Rea 1 Zone
I
s
.5
.4
.:3
.2
.1
• 0
0 5
Fig. 1
p:0.5
D:1.q
I I
I I
Unreal Zone Real Zone
-.....
':-......
~ ~ .......... ........
- - "'-."f"--,. ..... ..........
'
......
----
r--- / -...........l ............... ........... ......
I.
I
I
.-..
/"--..... ~--~--
I
I
r----
!.- -.L--
I
1----t-1--
~ t-f---
-
I
I
- I
-...!.. ../
I
-
.......
1----
1---
Fig. 3
I
I
I
:
.0+------+--~--~--L-~--~
s
.5
.4
.3
.2
.1
.0
0
c 1
:17.8
Unreal
5
Fig. 2
p:0.9 0:0. 0;.1. 0
I I I I
I
Zone
1 Rea 1 Zone
5
Fig. 4
/1 I
I
I
I
I
I
I
!
I
I
I
I
I I I

434 Abstracts
Figures 2 and 3 show how the reflections react each with other: the (001)
with (002), the (002) with (004), the (003) with (006), etc.
Furthermore, the graphs clarify the already expFessed-questions-about -the
meaning of different basal reflections with various C 1 - C 2
- p and D.
Allegra G., 1964. The calculation of the intensity of X-ray diffracted by monodimensionally disordered
structures. Acta crystallogr. 17, 579-598.
Cesari M., Morelli G.L., Favretto L., 1961. Identification d'un mineral a interstratification partiellement
reguliere d'illite-montmorillonite dans les argiles noires de la Sicile du Sud-Est. Acta
Univ. Carol., Geologica, Suppl. 1, 257-262.
Cesari M., Morelli G.L., Favretto L., 1963. Determination of the type of stacking in mixed layer clay
minerals. Acta crystallogr. 18, 189-196.
Morelli G.L., 1966. Intensita della diffrazione dei raggi X da parte di minerali argillosi a strati
misti. I- Calcoli per vari modelli strutturali. Rend. S.M.l. Anno XXII, 175-186.
Morelli G.L., Favretto L., Asklund A.M., 1967. Determination of the type of stacking in a mixed
layer clay mineral from Kinnekulle. Clay Miner. Bull. 7, 113-115.
Morelli G.L., Cesari M., 1967. Intensita della diffrazione dei raggi X da parte di minerali argillosi a
strati misti. 11- Caso di inter!aminazione di due strati aventi differenti fattori di struttura. Atti
Soc. It. Sci. Nat. CV!, Fasc. III, 209-216.

Section IV
Soil Mineralogy· and Geochemistry

Miner. Petrogr. Acta
Vol. 29-A, pp. 437·453 (1985)
Mineralogical Characteristics of the Fine Fraction of Soils
from the Emilia-Romagna Region, Northern Italy
G. FELICE 1 , G.C. GRILLINP, N. MORANDP, G. VIANELLF
I Istituto di Mineralogia e Petrografia, Universitil di Bologna, Piazza di Porta S. Donato 1, 40127 Bologna, Italia
2 Regione Emilia-Romagna, Ufficio Cartografico, Via Galliera 21, 40121 Bologna, Italia
ABSTRACT - Forty six soil profiles variously distributed through the entire
Emilia-Romagna Region, for a total of 156 horizons were examined as a part
of the research program relative to the study of the mineralogical composition
of the fine fraction of soils in this Region.
The extensive data collected have lead to the following concluding considerations:
- Jndependent of type of parent rock lithology and of the soil evolution it
was observed that the mineralogical components, chlorite and kaolinite, are
not significant and that the whole range of illite and smectite variation is
found, with higher frequency in the range of ratios 1:1 to 3:2.
-The profiles characterized'by high acidity show the regular presence of

438
G. Felice, G.C. Grillini, N. Morandi, G. Vianelli
tions of the fine fractions of the various
horizons of the same profile, between
those of the various profiles
formed on analogous lithological
substrates or between those obtained
from profiles formed on different
types of substrates.
related to the nature of the substrate
and they_ S_ll

«Hill soils»
Mineralogical Characteristics of the Fine Fraction of Soils ... 439
MA - Soils found on substrates
consisting of flyschioid sediments
(sandstones, marls and siltites) of the

440 G. Felice, G.C. Grillini, N. Morandi, G. Vianelli
way it is possible to identify the various
types of interlayers present in
the profiles and to · determine the
characteristics of some particular
phases previously studied in detail by
the authors (MONGIORGI &
MORANDI, 1970; FELICE et al.,
1981).
The semi-quantitative data relative
to the clay minerals were obtained
following the method of BISCA YE
(1965), modified according to the suggestions
of other authors (WALKER,
1957; THOREZ, 1975; MEZZETTI et
al., 1980; FELICE et al., 1981). These
modifications were used for the determination
of the phases defined in
this work as « 14 A mineral» and
.,,-clay=Verniiculite» and of. the
amounts of serpentine.
The pedological data were
obtained according to the methods
which are presently in use at the
laboratories of the «Servizio Cartografico>>
of the Emilia-Romagna Region.
The determination of the percents
of sand (S) (2-0.05 mm), silt (L) (0.05-
0.002 mm) and clay (A) (

Mineralogical Characteristics of the Fine Fraction of Soils ... 441
have «vertic» characteristics. They
were used as reference soils for comparison
purposes. The mineralogy of
the

TABLE 1 I
Pedological characteristics and clay components of FA rnd TF soils (for abbreviations see text)
Hori-
DEPTH TEXTURE I
Sample Classification
CaC03 CLAY COMPONENTS (to 100%)
zons
(cm) (%) I pH total
from to s L A! % Sm I I-Sm Cl K Se 14 A
I
I
FA1 Entic Chromoxererts Ap 0 60 21 30 491 7.9 13 45 43 6
AC
6
1 60 80 15 32 531 7.9 14 30 33 25 6
AC2g
6
80 140 23 26 51 i 7.9 14 21 46 21 6 6
N
""'
FA2 Entic Chromoxererts Ap 0 so 25 26 49, 7.6 14 25 28 30 9 8 0
AC 1 so 80 26 26 48i 7.7 13 23 33 27 9 8
"lj
AC -
2 80 115 20 31 49: 7.7 14 23 39 19 10 9 - - "'
c,g 115 150 24 26 so: 7.8 15 24 38 19 11 8 -
~~
C2g 150
i
210 - - :
- 17 38 28 11 6 - C'l
I
FA3
h
Entic Chromoxererts Ap 0 so 19 34 47! 7.8 7 33 24 34 9 - C'l
AC, so 110 18 30 52 i 7.9 3
;:!,
28 19 46 - 7 -
~
AC2g 110 190 n.d. n.d. n.d.i n.d. n.d. 24 27 42
Cg
7
190 250
-
n.d. n.d. n.d.i n.d. n.d. .:-·
43 18 29 10 -
~
FA4 Entic Chromoxererts Ap 0 50 .17 30 53 8.0 11 25 42 - 18 15 - ~
ACg so
0
80 13 34 53 8.3 8 19 55 - 14 12 - - i:1
C,g 80 120 15 24 61 . 8.5 4 23 53
;:s
13 11 - _!:::
FAS Entic Chromoxererts Ap 0 40 15 26 59 7.9 3 23 47 16 14 - :
0
ACg 40 70 15 24 61 8.5 5 17 57 - 13 12 - - $
Ctg 70 140 11 36 53 ~
9.0 19 19 63 10 9 -
;:s
Cjg 140 200 p 32 51 8.9 14 10 58 17 14 "'
-
C3g 200 220 17
-
26 57
E::
8.5 4 13 55 - 17 15 -
,I
FA6 Entic Chromoxererts Ap 0 70 18
I
29 53 7.7 10 17 52 - 17 14 - ;
AC 1 g 70 ~50 18 29 53 8.0 14 22 49 - 17 12 -
AC2g 150 205 14 25 61 8.0 16 21 55 - 13 11 -
FA7 Entic Chromoxererts Ap 0 45 15 32 53 7.8 13 43 33 - 14 10
ACg 45 80 15 22 63 8.1 5 42 44 - 8 6
C,g 80 100 17 20 63 8.1 - 36 44 11 9
C2g 100 165 17 30 53 8.3 12 46 31 - 12 11
C3g 165 230 17 26 47 8.0 2 29 35 - 10 8 18
I
l

~-~-1
TABLE I
Pedological characteristics and clay components of FA and TF soils (for abbreviations see text)
DEPTH TEXTURE CaC0
Hori-
3 CLAY COMPONENTS (to 100%)
Sample Classification (cm) (%) pH total ~
zons
from to s L A % Sm I I-Sm Cl K Se 14 A ;s·
;:; "'
FA8 Entic Chromoxererts Ap 0 so 17 . 24 59 7.7 7 46 34 11 9 - ~
1)'
ACg 50 85 17 48 65 7.9 5 39 42 10 9 - - f2..
Ctg 85 110 17 23 60 8.2 8 42 40 9 9 - (')
;::;-
C2g 110 180 17 38 45 8.5 3 59. 21 7 7 6
!'>
IIC 3 g 180 240 17 44 39 8.8 19 43 34 - 12 11
;:;
FA9 Ap 0 50 16 / 30 54 7.9 10 so 20 20 5 5
FAIO Entic Chromoxererts Ap 0 so 14 36 so 7.9 13 40 26 24 5 5 -
"'
~-
FAll Ap 0 so 15 40 45 7.8 12 65 12 16 tr. 7 - .Q,
TF1 Typic Haploxeralfs Ap 0 40 38 46 16 7.5' 30 23 40
s.
7 -
Bt 40 75 34 42 24 7.6 - 32 25 31 12 -
"' "lj
;s·
B21t 75 105 32 42 26 7.6 57 36 - 7 -
IIC 1 g 105 150 36 35 29 7.7 - 95 - - 5
"''
..... "ll'·
IIC2g 150 190 n.d. n.d. n.d. n.d. - 95
!'> ',
- - - 5 -
-~
IIC 3 g 220 240 23 32 45 8 2~ 72 17 - 41 - - 6'
IIC4g 240 265 39 14 47 7.8 78 14 - - 8 -- -
;,:
.Q,
TF2 Typic Haploxeralfs A2 1 16 42 44 14 4.1 - 36 33 10 7 - 15 en
0
Bt 16 42 34 40 26 5.0 12 40 36 6 6 - -
F
B 21 t 42 88 34 40 26 5.6 - 18 37 34 12
B 2 ~t 88 95 38 34 28 6.1 - 90 ' 10
B 23 t 95 145 25 32 43 7.5 - - 90 10
IIC 1 g 180 205 n.d. n.d. n.d. n.d. - - 90 - 10
~
•(\>
;:t
..,.
w

444 G. Felice, G.C. Grillini, N. Morandi, G. Vianelli
- Even though formed on qualitatively
different starting materials, it
cannot be excluded that the alkaline
pH of TF 1 favoured the formation of
swelling minerals; whereas, the acid
pH of TF 2 would favour the conservation
of the non swelling phase
(14 A mineral, high illite content) in
the upper part of the profile. With a
sufficiently neutral pH, abundant
amounts of swelling phases have
been formed in TF 2.

Mineralogical Characteristics of the Fine- Fraction of Soils ... 445
nent, in agreement with FELICE et al.
(1981). MA 2-3 are less acid than the
others and are richer in illite.
- MA 1, the profile with the highest
pH values of the whole group,
shows a characteristic «comma» 'behaviour
determined by the presence
of aB horizon (the most acid with the
highest percent of 14 A mineral) with
traces of the accumulation of illuvial
clay (sand = 29%, silt = 35%, clay =
36% in the Bzt horizon).
-The shape of the compositional
areas (oriented along the I-14 A axis)
and the particular abundance of interstratified
minerals indicate a
. rather extensive mineralogical evolution
confirming the pedological data
(presence of a B horizon, complete
Jack of carbonates and low desaturation).
MA (8-12)
'-
MA 9 is slightly differentiated from
the substrate and has not evolved
very much because of erosion. The
other profiles have a B horizon and
are well provided with basic cations.
There are traces of the accumulation
of illuvial clays in MA 8.
The mineralogy of these soils is
characterized by dominant illite and
clay-vermiculite (V) which sometimes
are accompanied by chlorite.
Both types of minerals are considera
b 1 y disordered. Based on ~ the information
reported in Fig. 3, the fol-\
lowing considerations can be made:
- The mineralogical composition
is concentrated in a restricted area
(In Vz3 - b Vn) with quite wide
variations in the chlorite content.
This is indication of a certain degree
of homogeneity in the lithological
substrates but with some local variations.
-The shape of the compositional
areas, oriented along the I-V axis, is
indication of a certain mineralogical
evolution within the individual profiles.
An examination of the two MA
groups shows that they are characterized
by two different minerals (14 A
mineral for the first group and clayvermiculite
for the second) even
though there is considerable superimposition
of their respective areas
in the ternary diagram. This demonstrates
their dependence on the same
type of substrate and a pedogenetic
evolution tied to different physicochemical
factors.
b) MC (Table 3)- MC 1 and 2 are·
poorly developed because of erosion.
MC 3 and 4 have a B horizon and are
moderately desaturated; they show
traces of accumulation of illuvial
clay. MC 5 and 6 show incipient podzolization.
There is a progressive differentiation
from substrate in going
from MC 1 to MC 6. With the exception
of MC 6 (described in FELICE et
al., 1981), the mineralogical composition
consists of 14 A mineral, I, I-14 A
(in MC 4-B 21 t and Bzzt, the interstratified
minerals are of the Cl-Sm type)
Cl and sometimes K.
Observation of Fig. 3 leads to the
following considerations:
-With the exception of MC 6, the
areas for these profiles are concentrated
in a restricted zone of the
triangle, indicating a relative
homogeneity of the substrates.

_J
TABLE 2 I
Pedological characteristics and clay components of MJ\ soils (for abbreviations see text)
. I
DEPTH TEXTURE ·j
Hori-
CaC03 CLAY COMPONENTS (to 100%)
Sample Classification (cm) (%) I pH total
zons
from to s L AI % 14 A V I I-Sm Cl K
i
MAl Typic Hapludalfs At 3 10 44 44 12 5.7 - 9 39 41 11
A3 10 40 45 39
6.9 17 28 38 17
Bt 40 70 55 27 ~~ 6.2 - 18 24 44 14
B 2 t 70 115 29 35 3q 6.6 - 9 33 53 5
0
'>:1
c 115 140 n.d. n.d. n.1. 6.5 8 - 42 43 "7
I
MA2
t
J
Umbric Dystrochrepts At 1 30 42 45 q 5.0 - 22 21 57 -
;s
"'
MA5 Typic (

,
TABLE 1
Pedological characteristics and clay components of FA and TF soils (for abbreviations see text)
DEPTH TEXTURE CaC0 3
CLAY COMPONENTS (to 100%)
Hori-
Sample Classification (cm) (%) pH total
zons
from to s L A % Sm I I-Sm Cl K Se 14 A
MA7 Typic («Spodic) Hapludults AI 2 7 63 28 9 3.8 11 17 64 8 "' ;::;
A2 7 20 63 25 12 4.4 - 53 - 6 41 tr. - ,g
B2 20 60 62 21 17 4.6 65 6 29 tr. c:;·
B'2t 60 110 35 35 30 4.9 - 18 - 40 42 tr. - ~
(')
;s-
MA8 Typic Hapludalfs AI 1 5 60 28 12 4.9 20 70 10
I'>
;::;
B1 10 30 58 -25 17 7.0 - - 56 44 - - - ()
(li
B21 70 90 58 25 17 8.3 3 52 48 - -
MA9 Lithic Xerorthents 15 58
B22tca 120 140 57/ 30 23 8.5 34 48 52 - - - a·
"'
AI 2 29 13 8.0 17 - 30 so - 20 a
......,
;;,;.
MAlO Lithic Xerochrepts AI 1 5 42 39 19 8.0 15 38 52 10
"'
B1 5 25 36 45 19 8.3 7 39 52 9 '>1
~·,
B2 25 45 34 47 19 8.4 26 - 30 58 - 12 -
'>1,
MAll Typic Eutrochrepts Ap1 0 20 so 31 19 8.0 3 - 47 53
Ap2 20 40 so 31 19 8.1 3 - 52 48 5·
~-
B1 40 80 52 29 19 8.2 5 - 47 53 - a
B2 80 180 53 28 19 8.3 5 42 58 - - -
......,
(/)
c 180 225 62 27 11 8.2 5 48 52 - - ::1.
r
MA12 Dystric Eutrochrepts Ap 20 40 52 31 17 7.9 - 27 73
B 70 90 54 29 17 7.8 23 77
B2 110 130 60 23 17 7.8 - 28 72
c1 180 200 54 26 20 7.9 35 65
C2 210 230 56 26 18 7.9 38 62
u c3 230 280 70 19 11 7.6 27 73
is:
;:i•
~-
~1
"'
+>
+>
--.]

i
I
I
TABLE 3 I :
Pedological characteristics and clay components of MC, AS and PV soils (for abbreviations see text)
-!'>-
-!'>-
00
I
I
Sample Classification
Hori-
DEPTH TEXTURE! CaC03 CLAY COMPONENTS (to lOO%)
(cm) (%) I
zons
pH total
from to s L 1A % 14 A I I-Sm Cl K
MC1 Lithic Udorthents AI 0 23 70 15
MC2 Lithic Udorthents AI 0 15 40 48
115
112
7.3 16 53 16 10 5
5.2 - 20 40 20 20
MC3 Ultic Hapludalfs AI 0 30 42 40 118 4:8 - 16 34 44 6 tr.
B2t 30 70 40 34 126 5.0 15 37 31 12 5
c 70 120 40 37 \23 4.7. 11 55 17 17 - 0
'lj
MC4 Typic Hapludalfs AI 0 20 47 35 :18 5.1 31 49 20
~
1
- ()•
B21t 45 80 46 30 z4 6.3 - 62 38 - .!'>
B 22 t 80 120 48 30 122 6.9 - 69 31 -

TABLE 4
B:::
Pedological characteristics and clay components of GE soils (for abbreviations see text)
;s·
"'
DEPTH TEXTURE CaC03 CLAY COMPONENTS (to 100%) i:l
Hori- 0
Sarriple Classification (cm) (%) pH total
zons
"" c;·
from to s L A % 14 A V I I-Sm Cl K ~
()
GEl Typic Xerorthents c, 8 30 60 36 4 7.4 7 36. ;:s-<
- 24 33 7 tr. .,
c2 30 60 57 -.40 3 7.5/ 7 45 23 24 8 tr. i:l
"(;;
GE2 Typic Xerorthents c, 8 25 75/ 18 7 6.3 37 30 33 tr. tr. ;:!.
c2 80 100 75 18 7 5.5 - - "'
~-
GE3 Typic Eutrochrepts A12 4 30 25 39 36 .7.6 32 27 36 tr. 5 .Q,
B2 30 60 18 44 38 7.8 17 26 - 28 36 5 5 ~
B3 60 85 22 42 36 8.1 6 24 28 38 5 5 "lj "'·
c" 85 150 21 41 38 8.2 15 21 39 34 tr. 5 ~·,'
IIC2 150 250 34 60 6 7.4 11 20 - 43 25 6 6 "lj,
.,,
... ,
GE4 R 0 15 n.d. n.d. n.d. 34 28 24 9 5 "' 6·
;s
GE5 R 0 15 n.d. n.d. n.d. 42 - 35 16 7 .Q,
GE6 Lithic Xerorthents A12ca 4 20 32 38 30 7.4 16 57 30 - 7 6 ~
c 20 40 29 65 6 7.8 30 85 - 10 5 tr.
c 20 40 27 45 28 7.7 8 90 10 - tr. tr.
(/)
0
t
'D

450 G. Felice, G.C. Grillini, N. Morandi, G. Vianelli
- The compositional areas of MC
3-4-5 are oriented along the I-14 A
mineral axis and,Jrom a mineralogical
point of view,. indicate a considerable
evolution.
-MC 6 is distinctly different from
the other profiles; the mineralogical
composition puts. it nearer the 14 A
mineral vertex (in this case also
smectite), indicating a particular
mineralogical-pedological evolution
of the profile (podzolization).
-The pedological data relative to
the state of differentiation from the
substrate is confirmed by the variable
I/14 A mineral ratio, a mineralogical
index of the state of evolution of
the soil.
<
·------~---- -~- Tlle--cl1Torl1:e--coii1en.-t-1n.- thesesoils
is among the highest found in
the present study. This is sometimes
linked to the high acidity of these
soils (FELICE et al., 1981) as well as
to the peculiar composition of the parent
rock.
c) PV and AS (Table 3) - The soils
have a B horizon and they are well
provided with basic cations. The differentiation
from the substrate is
moderate. The mineralogical compositon
consists of I (distinctly predominate
in PV), I-14 A mineral, 14 A
mineral, Cl and K.
The observation in Fig. 3 of profiles
PV and AS leads to the following considerations:
- These two mineralogically similar
groups occupy distinctly different
areas of the diagram, confirming on
the one hand, that each group is
formed on the sarrie substrate and on
the other, that the two types of substrates
are distinctly different even if
they belo:gg_tl2!h~ sam(;! «f()~~~tion».
- The subcircular shape of the
compositional areas confirms in both
cases the moderate evolution of the
profiles (high contents in illite and
chlorite).
d) GE (Table 4) -. GE 1-2-3 are
slightly differentiated profiles with
little evolution, due to erosion; GE 3
has aB horizon. GE 6- represents
pockets of material with a finer texture
present in the C horizon.
The mineralogical composition is
as follows: disordered Sm, degraded
I, disordered I-Sm, Cl and sometimes
K. GE 2 differs from the others in that
it contains V in place of the Sm. In all
the. profiles~ howeve~, a part of the
smectite does not completely expand
after treatment with KCl, leading to
the supposition that the mineral is
mixed with a clay-vermiculite.
Examination of Fig. 2 leads to the
following considerations:
~The compositions are quite different
even if it seems evident that
there is a strong predominan~e of
smecti te in these soils.
-The anomalous nature of GE 6
probably can be· attributed to particular
formation mechanisms (note
the presence of pockets) rather than
to mineralogical and/or chemical
variations.
- Considering GE 4-5 as the most
probable parent rock for these soils,
it seems clear that from the mineralogical
point of view, the exten.t of
evolution in all these profiles is low.
-Because of both its sand content
and the presence of clay-vermiculite,

Mineralogical Characteristics of the Fi~eFraction of Soils ... 451
GE 2 seems to have been formed on a
different substrate from that of the
other soils in this group or, at least, to
have undergone a peculiar pedogenetic
process.
e) OF- These soils are found on
ophiolitic rocks of various nature
(gabbro, hydrothermalite and predominantely
serpentinite); they have
the common characteristic of being
only slightly developed in depth. It
often is difficult to distinguish between
the various horizons of an individual
profile. The~ mineralogical
study of the fine fraction of the hori-
. zons sampled in these 5 profiles
showed the presence of trioctahedral
smectite (d (060) = 1.53 A), chloriter
and interstratified · chloritetrioc.tahedral
smectite (both disor-
. c
dered and ordered) as well as small
amounts of primary minerals of ' the
parent rock. Quantitative information
on these components was not
obtained because of the absence of
illite which must be utilized as the
reference mineral.
Soils with similar compositions derived
from serpentinite have been reported
recently in the literature
(ROBENHORST et al., 1982) but the
mechanism of formation and the type
of evolution involved in the development
of these chlorite-type structures
. derived from serpentines by simple\
pedogenetic action, still are not clearly
understood. (At present, some of
the authors are involved in completing
further research directed towards
obtaining a better understanding of
the chemical and physical parameters
on :which these transformations
are based).
The OF soils were included in this
research for the purpose of increasing
the range of data but they are completely
different from all the other
soils previously described here.
Concluding remarks
The extensive data collected have
lead to the following concluding considerations:
1) Illite is present in variable proportions
but, with only the exception
being the soils found on ophiolitic
rocks, its percentage in all the soils,
derived from an especially wide variety
of parent rock, was concentrated i
in the range 30 to 50%. The comparison
of the compositions of the hori-.
zons of each individual profile gave
evidence of the strong evolutive
tendency to the alteration of illite toward
swelling structures (smectite,
clay-vermiculite or interstratified
minerals) or to non swelling minerals
having Al-hydroxy interlayers (14 A·
minerals).
2) Chlorite and kaolinite, especially
'the former, were components almost
always present in the numerous soil
profiles studied; in general, the
amount of these minerals was around
15%. In cases where an enrichment of
chlorite or kaolinite was found, it al-.
ways could be attributed to the particular
lithology of the substrate.
3)-0nly the plain soils (FA and TF)
and those related to the Messinian
evaporitic succession (GE) were dis-

1
452 G. Felice, G.C. Grillini, N. Morandi, G. Vianelli
tinctly smectitic which seems to be
due i) to the presence of a lithological
substrate already rich in degraded
clay minerals which have not yet
undergone diagenesis or ii) to conditions
where, there is considerable
availability of basic exchangeable cations.
This particular chemical environment,
was favoured by the geographic
and geomorphologic situation
of the Po Valley and by the considerable
mobilization of Ca within the
lithotypes related to the «Gessoso­
Solfifera>> succession.
4) All the hill soils related to the
sedimentary lithological successions
of the «Marnoso-Arenacea>>, the
-~-~---~---- ____«MacignO>> __ or __:the_ -~Caotic_o_jndif­
ferenziato>> contain either clayvermiculite
or more frequently the 14
A mineral. Similar characterizations
seem to be related mainly to chemical
factors: the type and amount of
ions mobilized in the profile and the
pH, respectively (c.f., the interdependence
found between acid pH
and the presence of the 14 A mineral).
5) The horizons within individual
profiles tend to be differentiated,
from a mineralogical point of view,
by the pedogenetiC phenomena to
which they _are subjected (c.f., the
elongated shape of the areas which
represent the.compositions.~of the individual
profiles). The extent of this
effect is sensibly reduced when the
sediment of the substrate itself is the
product of intense elaboration during
the depositional phase (c.f., many of
the FA soils on fluvial sediments with
fine grained textures and the AS and
. PV soils on the «Caotico Indifferenziato>>).
This mineralogical differentation
can be considered as being an evolutive
process involving the gradual
tr~nsformation of crystalline phases
into other more swelling phases.
Observing Figs 2 and 3, one will note
that_ \Vhen the compositional areas
tend to be elongated, they are always
elongated parallel to the illitesmectite-type
side of the triangle;
this leads to the following conclusions:
a) the chlorite and kaolinite
phases represent stable components
in the soils; b) illite tends to evolve
towards clay-vermiculite, towards
the 14 A mineral or towards smectite
depending mainly on chemica.l variables
(pH and ionic concentrations),
geographic variables (valley or hill
areas) and, less frequently, on variables
related to the parent rock.
REFERENCES
BrsCAYE P .E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and
adjacent seas and oceans. Geol. Soc. Am. Bull. 76, 803-832.
BouYoucos G.J., 1962. Hydrometer method improved for making particicle size analyses of soils.
Agronomy J. 54, 464-465. ·
FELICE G., GRILLINI G .C., MO RAND I N., 1981. Characteristics of a 14 A clay mineral in podzolic soils of
Lizzano.in Belvedere (Bologna). Miner. Petrogr. Acta 25, 79-90.

Mineralogical Characteristics of the Fine Fraction of Soils ... 453
MEZZETTI R.', MO RAND! N., PIN! G A., 1980. Studio mineralogico delle porzioni pelitiche nelle «Mame di
Antognola» della zona di Zocca (Modena). Miner. Petrogr. Acta 24, 57-75.
MoNGIORGI R., MO RAND! N., 1970. Al saponite e strati misti clorite-Al saponite nelle idroterrnaliti di una
breccia a contatto coi diabasi di Rossena nell'Appennino reggiano. Miner. Petrogr. Acta 16,
139-154: .
MO RAND! N., PoPPI L., GRASS! G., 1976-77. Semplice apparato riscaldante per la tecnica diffrattometrica
di preparati orientati di argille. Miner. Petrogr. Acta 21, 145-148.
RABENHORST M.C., Foss J.E., FANNING D.S., 1982. Genesis of Maryland Soils Formed from Serpentinite.
Soil Sci. Soc. Am. J. 46, 607-616.
SocrETA !TALIANA ScrENZA DEL SuoLO, 1976. Metodi norrnalizzati di analisi del suolo. Tipolitografia G.
Capponi, Fininze.
SOIL SuRVEY STAFF, 1975. Soil Taxonomy. A Basic System of Soil Classification for Making and
Interpreting Soil Surveys. USDA Agric. Handbook, no. 436, 754.
THOREZ J., 1975. Phyllosilicates and Clay Minerals.Ed. G. Lelotte, Dison, Belgique.
VAI G.B., Rrccr LucCHI F., 1976. Algae-bearing and clastic gypsum in a «Cannibalistic>> evaporite
basin: a case history from the Messinian of northern Apennines. Messinian Seminar no. 2,
Gargano, 1976, Field Trip Guidebook, 1-16.
WALKER G.F., 1957. Differentiation ofverrniculites and smectites in clays. Clay Miner. Bull. 3, 154-
163.

Miner. Petrogr. Acta
Vol. 29-A, pp. 455-460 (1985)
Quantitative Determination of Minerals in Clays
from Profiles in the West of Central Spain
by Differential Scanning Calorimetry
M.T. MARTIN PATIN0 1 , C. TURRION 2 , M.V. ROUX 2 , J. SAAVEDRA 3 ,
A. MILLAN 4
1 Instituto de Edafologia y Biologia Vegetal, C.S.I.C. and Departamento de Geologia y Geoquimica, Universidad
Aut6noma, Canto Blanco, 28049 Madrid, Espafia
2 Instituto de Quimica Fisica «Rocaso!ano», C.S.I.C., Serrano 119,28006 Madrid, Espaiia
3 Centro de Edafologia y Biologia Aplicada, C.S.I.C., Cordel de Merinas 40-52, Apartado 257, 37008 Salamanca,
Espafia
4 Departamento de Geologia y Geoquimica, Universidad Aut6noma, Canto Blanco, 28049 Madrid, Espafia
ABSTRACT- Differential Scanning Calorimetry (DSC) was used for the quantitative
determination· of gibbsite and halloysite contents. The endothermic
peak areas determine the heat of reaction changes (LlrH) and therefore the
mineral quantities.
The method has been utilized for the study of two alteration profiles developed
on granites. It is considered suitable in cases such as these, without
the need of selective separation of the accompanying minerals and without
needing the pu;.e mineral as a standard.
Introduction
, This study is part of one on the origin
of economically interesting alumini
urn minerals in the Provinces of
_Salamanca and Avila (Spain).
In previous' studies, SAAVEDRA
ALONSO & MARTIN PATINO (1983)
and MARTIN PATINO et al. (1985);
determined the mineralogy of two
· profiles developed from deeply
weathered granites situated in midwestern
Spain. The authors consider
some of the factors that affect the
formation of aluminium hydroxides
and oxy-hydroxides. Gibbsite is the
main component of clays from the
soils and granitic saprolites. The
mineral is relict and is formed in the
weathering process directly from
mica and indirectly from feldspar
through hydrolysis in an alkaline environment.
Halloysite (10 A) is found
filling the water-circulation cracks in
one of these profiles.
Research carried out with the financial support of the Spanish «Comisi6n Asesora de Investigaci6n
Cientifica y Tecnica>>.

456 M.T. Martin Patino,.C. Turri6n, M. V. Roux, J. Saavedra, A. Millan
The purpose of this study was to
determine the amounts of gibbsite
and hall~ysi te (1 0 A) from the soils
and the saprolite cited. The problems .
of the origin of the gibbsite and of its
distribution at different depths also
have been examined.
Materials and methods
Eight clay samples, two from soils
and two from weathered rock from
each profile, I and II were analysed
employing Differential Scanning
Calorimetry (DSC). A Perkin-Elmer,
Model DSC-2C, was used, connected
······---------to.a Model 3600-Data Bank··-
Experimental technique
Samples of different mass, but always
less than 5 i:ng, were analysed,
in N2. atmosphere, in covered pans of
aluminium for gibbsite (heating from
110 octo 427 oq and of gold for halloysite
(10 A) (heating from 380 octo 680
°C). The temperatures were increased
at 5 °C/min.
The gibbsite and halloysite (10 A)
contents were calculated from the
changes in their corresponding heats
of reaction (LlrH) determined for the
endothermic peak area (Figs 1 and 2) ..
Gibbsite and halloysite (10 A) show
DSC endothermic peaks at about 250
oc and 500 oc respectively. The information
obtained was stored in the
1-.8 1-1 WT = 2.82 m9
SCAN RATE • 5.00 de9/min
1.6
1.4
1.2 ~
1.0 ~
0.8
0.6
PEAK· .FROM= 466.49
T0=583.5
0.4 ONSET= 508.15
CAL/GRAM = 121.48
0.2
temperature (K)
0.0
390 450 510 570 630 690
1.8-
1.6
1.4
1.2
~
1.0
~
0.8
0.6 PEAK FROM= 463.49
TO= 809
0.4 ONSET= 505.98
CAL/GRAM = 182
0.2
min = 535.00
0.0
temperature (K)
390 450 510 570 630 690
1.8
1.6
1.4
1.2
1..0. ~
0.8
1-2 WT=2.56m9
SCAN RATE= 5.00 deg/min
Ol
"'-
0.6 PEAK FROM= 472.99
T0=631.5
0.4 ONSET= 513.75
CAL/GRAM = 190.6
0.2
0.0 '"- temperature (K)
390 450 510 570 630 690
1.8
1.6
1.4
1.2
1.0
0.8
1-4 WT=L75m9
SCAN RATE= 5. 00 de9/mi n
~
~
0.6 PEAK FROM= 472.99
TO= 613
0.4 ONSET= 504.82
CAL/GRAM = 182.53
0.2
tempera tu re ( K)
0.0
390 450 510 570 630 690
Fig. 1 - Endotherm peak areas of gibbsite from DSC curves, profile I.

Quantitative Determination of Minerals in Clays from Profiles ... 457
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
PEAK FROM • 505.99
TO • 547.51
ONSET • 517.92
CAL/GRA/1= 6.13
390 450 510 570
1.6
2·2 WT= 4.43m9
SCAN RATE • 5.00 de9/min
1.4
1.2 !
1.0 "'
min = 531.26
0.8
0.6
0.4
PEAK FROM=502.49
TO= 544.0'1
ONSET= 515.21
CAL/GRAI~ = 6. 5
0.2
390 450 510
1.8
2·3 WT = 3.91 m9
SCAN RATE=S.OOdeg/min
1.6
1.4
1.2
:.l
1.0 ::::.
0.8 ~
0.6
PEAK FROM= 471.49
0. 4 TO= 615.5
0 · 2 ~~~;~;A~ 1 = 2 ;:; .94
570
390 450 510 570
630 690
630 690
. 630 690
Fig. 2- Endotherm peak areas of gibbsite from
DCS curves, profile JI.
Data Bank and, with the help of the
standard programme, the ex-
_perimental enthalpy ~rH (exp.), of
the dehydroxylation reaction and the
peak temperature was established
(Table 1). The percentage of each
mineral was determined by the
known ~rH ofthepure mineral (gibbsite
= 257.0 cal·g- 1 , halloysite (10 A)
= 157.0 cal·g- 1 ). These values are reported
by KARATHANASIS & HA­
JEK (1982).
A temperature calibration was
made for the DSC using indium, tin,
lead and zinc with a high degree of
purity and known fusion temperatures.
The calibration constant (f) =
6.80/6.92 was obtained with indium
(6.80 cal· g- 1 is the ~rH standard and
6.92 cal· g- 1 is the MH obtained in
our DSC-2C).
Results and discussion
The results for gibbsite are shown
in Table 2. In the upper horizon ()f the
soil (sample 1-1) the amount of this
mineral decreases noticeably. This is
due to its destabilization and coincides
with the presence of boehmite,
which is associated with the high i
concentration of fulvic acid within
the present-day edaphic level (MAR­
TIN PATINO et al., 1985). In the other
clays of profile I and in the clay of
weathered rock of profile II, the
amount of the mineral, was considered
to be similar. These similarities
contrast with the apparent differences
observed in the study of the
whole undisturbed samples by scanning
electron microscopy, in which
the amQunt of mineral appears to increase
with depth. However, it is consistent
with the fact that on the surface
the rock loses its primitive structure,
while the gibbsite crystals that
are released to become part of the
fine fraction remain attached to the
minerals from which they originated
at deeper levels (Figs 3 and 4). This
demonstrates the validity of these results.

458 M.T. Martin Patino, C. Turri6n, M.V. Roux, J. Saavedra, A. Milltin
TABLE 1
El(perimental results
- -~-~c~·~--~-~-~-~~-
Experiment m ,irH(exp) ,irH
num. mg oc cal c- 1 cal g- 1
Sample 1-1
1 2,93 265 126,7 124,6
2 2,07 255 119,8 117,8
3 2,82 262 121,5 119,4
4 5,36 270 120,1 118,0
Aveq~ge value: 120,0
Standard deviation: ±1,6
Sample 1-2
1 3,83 272 192,5 189,2
2 3,05 271 191,8 188,5
3 1,22 256 185,4 182,2
4 2,56 270 190,6 187,4
5 4,63 273 189,9 186,7
Average value: 186,8
Standard deviation: ±1,2
·--~-·· ·-----·-··-···------ -------- -- ----- -- -- ----- -
Sampl~:n-3
1 2,33 267 181,5 178,4
2 2,52 266 187,7 184,5
3 2,87 261 182,0 178,9
4 3,82 270 180,2 177,1
Average value: 179,7
Standard deviation: ±1,6
Sample 1-4
1 2,74 265 187,5 184,3
2 2,01 261 187,8 184,6
3 1,75 257 182,5 179,4
4 3,19 268 179,8 176,7
Average value: 181,3
Standard deviation: ±1,9
Sample 2-3
1 6,00 21'3 189,9 186,7
2 3,91 268 183,9 180,8
3 2,80 279 174,2 171,2
4 3,18 263 173,7 170,7
5 4,19 270 192,2 189,0
Average value: 179,7
Standard deviation: ±3,8
m = sample mass; t c= the corrected peak temperature; ,irH(exp) = the reaction enthalpy in
the experiment; ,irH the reaction enthalpy = ,irH(exp) X f
In the soil samples of profile II (2-1
and 2-2), the total removal of organic
matter before clay exctraction was
practically impossible. The reaction
of these samples to heat. treatment
was also different. Two endother-

Quantitative Determination of Minerals in Clays from Profiles ... 459
TABLE 2
Percentage of gibbsite in clay samples
Clay
% Gibbsite
1-1
1-2
1-3
1-4
2-1
2-2
2-3
120,0 ± 1,6
186,8 ± 1,2
179,7 ± 1,6
181,3 ± 1,9
6,03 ± 2,0
6,39 ± 2,3
179,7 ± 3,8
46,7
72,7
69,9
70,5
2.34
2.48
69,9
mic peaks (Fig. 2) appear in the
DSC analysis of material from the
top horizon (sample 2-1). The first
peak corresponds to the free mineral,
and the second may be due to the
effect of organic matter attached to a
fraction of gibbsite or to free aluminium.
This, however, remains to be
confirmed. In sample 2-2 (Fig. 2) the
first endothermic peak corresponds "
to gibbsite. There are other energy
changes due to non-eliminated organic
matter. Parallel treatments show
that energy is released at temperatures
below 400 oc as a result of the
loss of constitutional water from carboxyl
and phenolic hydroxyl groups.
Energy is also released aoove 450 °C,
but it is of a different kind and comes
from humic aromatic nuclei
(SCHNITZER & KHAN, 1972).
For halloysite (10 A) (sample 2-4,
Fig. 5), 146.4 cal· g- 1 was obtained for
the dehydroxyhttion reaction and the
mineral percentage calculated was
88 per cent.
The results give a high content of
these minerals in the clay fraction,
but it must be remembered that such
fractions are low in these sandy samples.
The technique is considered suitable
for quantitative determinations
in cases such as the above without.
Fig. 3 - Gibbsite crystals between the swelling
plates of mica: saprolite profile I, 2.500 ic.
Fig. 4 - Last one micrograph at high magnification:
saprolite profile I, 5.000 x.

T
460 M.T. Martin Patina, C. Turri6n, M. V. Row:, J. Saavedra,·A. Millan
S.OO~H7a~ll~o-ys~i7te~2--~4--------------------------------------~
0
UJ
"'
j
WT 1.50mg
Scan rate 20.00 deg/min
Peak from 702.3
to 820.26
Onset 720.62
Cal/gram 170.27
2.50
min. ·769 .96
O.OO~r-----~----.-----,------r-----,----~t=em~p~e~ra~t~u~re~(~K~)~DS~C~~
610 650 690 730 770 810 850 890 930 970
Fig. 5 . Endotherm peak area of halloysite from DSC curve, profile II.
either the need of selective separation
of the accompanying minerals or the
requirement of having a pure mineral
as a standard.
REFERENCES
K.ARATHANASIS D., HAJEK B.F., 1982. Revised Methods for Rapid Quantitative Determination of Minerals
in Soil Clays. Soil Sci. Soc. Am. J. 46, n~ 2, 419-425. ·
MARTIN PATINO M.T., SAAVEDRA J., MILLAN A., 1985. A mineralogical study of aluminium hydroxides
and oxyhydroxides in profiles of granitic alterations in Spain's Mid-West. Pp. 181-186, in: Proc.
5th Euroclay Meeting 1983, Prague (J. Konta, editor); Univerzita Karlova Praha.
SAAVEDRA ALONSO J., MARTIN PATINO M.T., 1983. Consideraciones sabre factores que afectan a la
formaci6n de oxihidr6xidos e hidr6xidos de AI en perfiles de alteraci6n del Centro-Oeste de Espaiia.
Bol. R. Soc. esp. Hta. Nat. 81, 1-4.
'
ScHNITZER M., KHAN S. V., 1972. Humic Substances in the Environment. Marcel Dekker, New York.

Miner. Petrogr. Acta
Vol. 29-A, pp. 461-471 (1985)
Mineralogical and Geochemical Relationships in
Pedological Profiles of Soils
N. MORANDI, M.C. NANNETTI, G.C. GRILLINI
Istituto di Mineralogia e Petrografia, Universita di Bologna, Piazza di Porta S. Donato 1, 40127 Bologna, Italia
ABSTRACT- The present study was directed towards verifying whether or not
the action of weathering, even though starting from parent rock of different
composition, tends to lead to the formation of soils with similar mineralogical
and geochemical characteristics in the fine fraction.
For this purpose, 25 horizons, grouped in 7 profiles of soils sampled in the
Emilia-Romagna Region (northern Italy) were examined. The

-
462 N. Morandi, M.C. Nannetti, G.C. Grillini
distinguish between characteristics
inherited from ancient weathering
cycles and/or diagenesis from those
related to true pedogenetic processes
(BELLANCA et al., 1980). ,
With this background in mind, the
present study was directed towards
determining what correlations exist
between the physical characteristics
and the mineralogical composition of
the complete soil profiles with the
corresponding distribution of the major
and trace elements within the fine
fraction. The specific objective of the
work was to reconstruct the existing
relationships between soil and parent
material. (of s.~dim.e}:;tJ150
7.6 2.5 y 5/2
7.7 2.5Y 4/2
8.2 2.5 y 6/2
8.2 5 y 513
8.1 5 y 6/2
Caste! Nuovo
Rangone
CR3 (MO)
Alluvial
deposits
(Pleistocene-
Olocene)
Alluvial
plane
43-1
·2
-3
-4
-5
A1
B2t
B3
cl
C2
0-14
14-29
29-45
45-80
>80
6.8 2.5 y 4/2
7:5 10 YR 4/3
7.8 2.5 y 5/2
8.1 2~:S y 5/2
8.0 5 ·y 5/3
Savignano
sul Panaro
S.239 (MO)
«Caotico
indifferenziato»
stde exposed
to North;
inclination
14"
36-1
-2
-3
46-1
-2
-3
-4
A1;
A13
c
Ap
B 21 t
B22t
Bca
0-13
13-34
34-50
0-50
50-90
90-120
>120
7A 2.5 y 4/2
8.1 2.5 y 512
8.2 2.5 y 5/2
5.9 10 YR 5/6
7.2 10 YR 4/2
7.3 2.5 y 5/6
8.2 10 YR 5/4
8.3
8.3
Palazzo di
Prada- 17
(BO)
Caste! Nuovo
Rang one.
CR1 (MO)
Savignan~
sul Panaro
S.240 (MO)
Dark grey
marls
(Miocene)
Paleosoils on
alluvial dep. ·
(Pleistocene-Olocene)
«Caotico
indifferenziato»
Side of a
level ridge-
Alluvial
plane ·
Crest

ols used for their identification,
their thicknesses, pH and colour (estimated
by comparison with the American
code of the «MUNSELL SOIL
COLOR CHARTS>>).
In all cases, the samples were taken
from soils developed on sedimentary
materials (fine and larger grained
alluvial material, clay, marls and
« Caotico Indifferenzia to>>) belonging ·
to formations of variable age, from
the Miocene to the Interglacial Riss­
Wurm, distributed in a wide area of
the Emilia-Romagna Region (northern
Italy).
Samples 56-1R and 56-1V correspond
to two fractions (reddish and
greenish in color, respectively) from a
B horizon sampled at Savignano sul
Panaro in soil developed on .
The samples collected from e_ach
horizon were first repeatedly washed
and wet screened to remove nearly
all of the organic matter and then the

.....,..
'[
464 N. Morandi, M.C. Nannetti, G.C. Grillini
TG and DT A curyes after subtracting
the values of C02.
The analyses of major, minor and
trace elements were carried out on
samples previously heated in an oven
at 850 oc for around 12 hours. This
was done in order to avoid weighting
errors which are quite frequent in'
samples having high percents of
adsorbed water as well as to facilitate
the preparation and maintenance of
the ~pellets for X-ray fluorescence
(XRF) analysis. Spectrographic tests
for some elements on samples before
and after drying did not show any
significant variations in the chemistry
of the more volatile elements.
··----~--·· J'!I

cm 0 .------..--
40
64
Clay
Horizons
A11
A/B
c
:=. Ka Il
u
40- 1
- 2
-3
15
cm 0 ..---------.r--
Ap
c
0 "'
u,
~~ ll
1 /s Sm Q Cc
49- 1
-2
D
1 I
-3
47- 1
- 2
Bca
B
Ka
-3
.::4
Bg
- 5
43- 1
- 2
- 3
c,
Il
Sm
cq
-4
-5
Il
Il
46- 1
Ve
50
..; 2
- 3
Cc - 4
100
Fig. 1- Mineralogical composition and clay fraction of horizons of 40 1 49,47,43, 36 and 46 profiles.

466 N. Morandi, M.C. Nannetti, G.C. Grillini
tion being that of profile 46, in which
the three «B» horizons are almost
totally vermiculitic with a sharp passage
towards the «A» horizon, characterized
by the presence of 4 clay
minerals among which illite predominates.
This heterogeneity between
the surface Ap horizon and the
3 underlying horizons can be attributed
to the superimposition of two
different soils, as seen from pedological
studies. The amount of kaolinite
increases in the horizons characterized
by low pH values.
The mineralogical compositions
(%) of the fine fractions of profile 56
(lR and 1V) are the following:
- 56-1R: chlorite 11, kaolinite 7,
·-~-----·---~-- -iUite-58;illite•smectite 15, quartz 6,
dolomite 3.
- 56-1V: chlorite 12, kaolinite 9,
illite 50, illite-smectite 15, quartz 6,
calcite 4, dolomite 4.
It can be noted that even though
the compositions of the two samples
differ, they both have a dominant
illite content with the unusual presence
of dolomite. From the point of
view of mineralogical composition,
there are strong similarities between
profiles 40 and 49 which along with
profile 56 are the only cases where
chlorite is present.
Geochemistry
Reported in Tables 2, 3 and 4 are
the results of the chemical analyses
carried out on the fine fractions of
each horizon of the individual profiles
examined.
The following observations can be
made based
--
on the overall data
---~---~-·- ~-. --·-
obtained:
l. Profiles 40 and 49 had high SiOz
contents (around 49%) accompanied
by low Alz03 contents (around 22%)
as compared with the average values
for the other profiles (46% and 24%,
respectively). In the same two profiles,
the MgO content is more than
4%, a value greater thah the MgO
content in any of the other profiles.
The amounts of these oxides can be
correlated to the mineralogical compositions
of the respective profiles,
characterized by the presence of
abundant amounts of I/S mineral
and Sm mineral and by the presence,
although not in great amounts, of
chlorite.
2. The oscillations of total Fez03
(from 8% to 12%) in the various profiles
can be related to variations in
the content of poorly crystalline hydroxides
which can not be seen by
X-ray diffraction analyses.
3. The Ti02 contents, from 0.7% to
' 1%, do not vary sensibly within the
various horizons of an individual profile
and only in profile 36 is the TiOz
content as low as 0.6%.
4. The percent of K 2 0 varies from
2.5 to 5.2, depending on the illite content
of the individual horizons.
5. Overall, there were no sensible
variations in the main chemistry
within the various profiles nor within
the various horizons of, individualf
profiles.
The data relative to the minor elements
(Li, V, Cr, Co, Ni, Cu, Zn, Ga,
Rb, Sr, Y, Zr, Ba, Pb) determined in

Mineralogical and Geochemical R~l-;tionships ... 467
TABLE 2
Chemical composition (weight% and ppm)
40 49 56
% 2 3 2 3 1R 1V
Si0 2 48.19 50.84 48.41 48.85 49.31 49.23 45.05 46.25
TiOz 0.88 0.90 0.98 0.89 0.83 0.87 0.97 0.65
Alz03 21.80 21.71 23.06 22.09 21.54 21.07 24.41 25.23
FEz03 10.00 8.76 8.05 10.02 9.98 9.21 12.38 10.86
MnO 0.12. 0.13 0.13 0.18 0.17 0.17 0.11 0.14
MgO 4.22 4.07 4.99 4.10 4.40 4.59 3.10 3.91
CaO 1.90 1.37 0.87 1.22 0.97 1.67 0.78 0.61
Na 2 0 0.24 0.44 0.52 0.38 0.58 0.65 0.37 0.34
K 2 0 3.58 3.65 4.35 4.53 4.66 4.21 5.60 5.59
PzOs 0.21 0.20 0.19 0.20 0.18 0.17 0.11 0.14
HzO+ >2S0°C 8.86 7.93 8.45 7.54 7.38 8.16 7.12 6.28
pp m
198 197
Li 96 146 153 216 237 206
V 240 241 246 240 247 241 236 274
Cr 361 279 282 224 229 233 164 174
Co 30 27 33 29 29 31 25 29
Ni 169 135 140 138 138 142 76 90
Cu 28 29 17 45 60 52 56 126
Zn 156 148 164 169 173 170 136 161
Ga 26 28 28 37 29 23 28 28
Rb 167 162 202 195 184 208 194 229
Sr 255 291 365 474 462 517 132 175
y 33 34 36 36 33 35 30 37
Zr 123 120 ,·139 119 106 122 114. 130
Ba 279 349 29~ 498 273 504 396 402
Pb 30 15 16 36 29 18 32 15
the layer silicate portion of the fine
fraction of the individual horizons
provide the following indications:
-a) Variations in the amounts of
these elements in the various horizons
of the same profile are limited,
with the exception of Pb which usually
increaseq to the point of doubling
in amount in the surface horizon as a
consequence of biogenetic processes
or because of pollution.
b) In the various profiles, striking •
variations in the content of these elements
are found which can be correlated
to the dominant type of clay
mineral present. In particular, sensible
increases of Cr, Co and Ni are
found in profile 40 and to a lesser extent
in profile 49. This d?ta; clearly
related to the mineralogical composition
(presence of chlorite and enrichment
in MgO), probably indicates
that the profile derives from parent
material which tends to be basic
in nature. The Cu content, medium
high, increases in profiles rich in
smectite or vermiculite. Finally, the
variations in Rb content are directly
related to the variations in illite and
KzO content.
c) Some minor elements (Li, V, Zn,
Sr, Ba) show variations which have
little relationship to the mineralogical
content and, therefore, may well

e determined by the type of parent
rock.
-0.5
Statistical analyses
Cluster analysis of the samples (Qmode)
and of the variables (R-mode)
was carried out using the mineralogical,
chemical and pH data for all
the horizons examined. The dendragram
resulting from the cluster analysis
of the samples (Fig. 2) shows that,
for all the variables examined, the
horizons of the individual profiles are
strongly correlated among them-
+o.s
Fig. 2 - Dendrogram of the single horizons (Qmode).

Mineralogical and Geochemical Rela"iionships ... 469
TABLE 4
Chemical composition (weight% and ppm)
43
% 2 3 4
Si0 2 44.42 47.46 47.39 47.16
TiOz 0.87 0.64 0.69 0.69
Alz03 24.80 23.72 23.73 23.87
Fez03 10.03 10.06 10.42 9.89
MnO 0.13 0.12 0.12 0.14
M gO 2.82 3.30 3.80 4.00
CaO ·1.62 2.27 1.79 1.58
Na20 0.28 0.21 0.12 0.47
KzO 3.98 3.74 3.86 3.85
PzOs 0.14 0.11 0.17 0.18
Hzo+ >zso 0 c 9.21 8.37 7.91 8.17
Org. mat. 1.70
pp m
Li 73 77 64 80
V 183 217 208 107
Cr 143 168 192 180
Co 20 18 14 14
Ni 63 93 120 111
Cu 45 49 61 49
Zn 159 155 158 172
Ga 23 21 26 19
Rb 187 178 191 186
Sr 114 109 124 129
y 28 33 32 31
Zr 95 106 108 'J02
Ba 365 281 212 204
Pb 21 9 11 7
46
5 2 3 4
45.89 45.45 45.83 46.98 47.12
0.74 1.00 0.87 0.82 0.79
24.58 23.34 24.94 24.23 22.55
10.74 11.84 11.87 11.50 11.00
0.11 0.12 0.11 0.11 0.12
3.78 2.57 3.00 2.88 2.90
1.94 1.36 1.78 2.03 3.30
0.23 0.27 0.24 0.20 0.32
4.05 2.80 2.55 2.56 2.88
0.18 0.24 0.10 0.12 0.15
7.76 9.51 8.71 8.57 8.87
1.50
84 112 104 88 87
381 203 202 203 190
245 184 179 171 155
15 22 20 20 20
131 98 116 103 89
70 85 62 53 58
382 212 173 152 156
24 24 24 24 26
189 187 165 160 168
130 87 113 121 145
31 32 37 40 32
105 77 104 106 116
171 592 416 398 338
9 26 13 19 14
selves. Exception to this is the surface
horizon of profile 46 which pedologists
describe as soil developed on
transported and heterogeneous materials,
characterized, among other
things, by limited values of pH and
considerable anomalies in mineralogical
composition. In addition, profiles
49 and 40 are strongly correlated
with each other: these two profiles
can be referred to the same lithological
substrate.
The correlations with high significance
(2::: 99.9%), obtained from the
cluster analysis of the variables, are
reported schematically in Fig. 3 (the
negative correlations are indicated
with a dashed line). It can be seen
that only two clay minerals have significant
correlations: illite with K
and Rb, and chlorite with Co, Li and
Zr. Of the two, the first is to be expected
(SAWHNEY, 1972) and the
second indicates a mixed derivation
for chlorite, from acid rock (with
... biotite) and from basic rock. The
highly significant correlations between
Mg-Ni-Cr, Co-Ti and Fe-Cu indicate
that the clay minerals in the
soil examined were derived from
basic rock.
In the dendrogram of Fig. 4,

~
470 N. Morandi, M.C. Nannetti, G.C. Grillini
8---
Fig. 3 - Schematic representation of positive
and negative (dashed lines) correlations among
the chemical and mineralogical variables.
obtained from the cluster analysis of
the variables, significant correlations
can be noted, some of which already
have been discussed and others for
which some __ com.ments~_are ~worthwhile.
Indeed, the positive Tikaolinite
correlations, combined
with the observation that Ti also is
always present in the absence of
kaolinite, are in good agreement with'
what has been reported in the literature
and may indicate either that Ti
is present in a separate phase which
associates easily with kaolinit.e _
(WEAVER, 1976) or that the Ti substitutes
for Al in the kaolinite structure
itself (RENGASAMY, 1976).
The V-Zn-smectite correlation
clearly indicates the preference of
these two elements for the expandable
structures; such a result is in
good agreement with MOSSER et al.
(1974). The high Fe-Cu correlation
and the less significant correlation of
these two elements withAl would indicate
the presence of poorly crystalline
iron and aluminium hydroxides
which always show a high geochemical
affinity with Cu, V, Ni, and Co,
some of which are present in large
amounts in the soils examined. Finally,
the positive high correlation between
PzOs and disordered interstratified
I/S may be indication for a
preference of phosphorus for 2: 1
layer silicate structures characterized
by structural disorder.
Conclusion
Based on the results obtained, the
following conclusions can be drawn:
Fig. 4 - Dendrogram of the variables (R-mode).
1. The statistical analyses of the
mineralogical and chemical data of

the fine fraction of the soils provides
useful indications for the characterization
of the profiles and for the determination
of anomalies in the succession
of the horizons of an individual
profile. Indeed, soils deriving
from lithologically different substrates
seem to be distinctly different
as regards the mineralogical composition
and chemistry of the fine
fractions. In addition, within individual
profiles, the various horizons
do not show profound diversification;
however, especially through use of
the chemical data, it is possible to determine
easily those horizons which
have developed on transported and
Mineralogical and Geochemical Relati~~ships ... 471
vertically heterogeneous material or
on material which has been subjected
to anthropic activity.
2. The minor elements related to
the clay minerals or to the poorly
crystalline hydroxides do not undergo
significant vertical movem~nt
during the pedogenetic process.
3. The mineralogy of the soils
, seems to have only a slight effect on
the geochemical behaviour of many
minor elements, as indicated by the
poor individual correlations, but
does have a somewhat greater effect
on the main "chemistry of the fine
fraction.
REFERENCES
BELLANCA A., Dr CACCAMO A., NERI R., 1980. Mineralogia e geochimica di alcuni suoli della Sicilia
Centro-Occidentale: Studio delle variazioni composizionali lungo profili pedologici in relazione ai
litotipi d' origine. Miner. Petrogr. Acta 24, 1 c 15.
BISCAYE P.E., 1965. Mineralogy and sedimentation of recent deep sea clays in the Atlantic Ocean and
adjacent seas and oceans. Geol. Soc. Am. Bull. 76, 803-832.
BocCHI G., LUCCHINI F., MINGUZZI V., MbRANDI N., NANNETTI M.C., 1982-83. Significato del chimismo
delle porzioni pelitiche nelle «Marne di Antognola» della zona di Zocca (Modena). Rend. Soc. It.
Min. Petr. 38 (2), 839-847.
BoCCJ:II G., MINGUZZI V., 1979. Dosaggio del boro nei silicati mediante spettrografia d'emissione.
Contributo alia conoscenza di rocce Standard Internazionali. Miner. Petrogr. Acta 23, 175-187.
CHESWORTH W., 1973. The parent rock effect in the genesis of soil. Geoderma 10, 215-225.
FABBRI B., GAZZI P., ZUFFA G.G., 1973. La detemzinazione della componente carbonatica nelle rocce.
Miner. Petrogr. Acta 19, 137-154.
FELICE G., GRILLINI G.C., MoRANDI N., 1981. Characteristics of a 14 A clay mineral in podzolic soil of
Lizzano in Belvedere (Bologna). Miner. Petrogr. Acta 25, 79-90.
FRANZINI M., LEONI L., SAITTA M., 1975. Revisione di una metodologia analitica per fluorescenza
basata sulla correzione completa degli effetti di matrice. Rend. Soc. It. Min. Petr. 31 (2), 365-378.
LEONI L., SAITTA M., 1976. X-ray fluorescence analysis of 29 trace elements in rocks and mineral
standards. Rend. Soc. It. Min. Petr. 32 (2), 47.9-510.
MossER C., WEBER F., GAc J.Y., 1974. Elements tfaces dans des kaolinites d'alteration formees sur
·granite et schiste amphiboliteux en Republique C,entrafricaine. Chem. Geol. 14, 95-115.
RENGASAMY P., 1976. Substitution of iron and titanium in kaolinites. Clays Clay Miner. 24, 265-266.
SAWHNEY B.L., 1972. Selective sorption and fixation ofcations by clay minerals: a review. Clays Clay
Miner. 20, 93-100.
WALKER G.F., 1957. Differentiation ofvermiculites and smectites in clays. Clay Miner. Bull. 3, 154-
163.
WEAVER C., POLLARD L.D., 1973. The Chemistry of Clay Minerals. Elsevier, Amsterdam.

Mi~er. Petrogr. Acta
Vol. 29-A, pp. 473-481 (1985)'
On the Effectiveness of the Extractable Forms of Fe, AI and P
in Identifying Soil Chronosequence Terms
E. ARDUINO, E. ZANINI, E. BARBERIS, V. BOERO, F. AJMONE MARSAN
Istituto di Chimica Agraria, Facolta di Agraria, Universita di Torino, Via P. Giuria 15, 10126 Torino, Italia
ABSTRACT - Four soil profiles were sampled on three terraces forming a
chronosequence originated from a high plain fan in the Po Valley in northern
Italy (45°27' to 45°31' N; 8°10' to 8°12' E). For the horizon of each profile the
following data were determined: forms of inorganic P; forms of Fe; forms of
AI; loam; clay and cation exchange capacity. The data were subjected to
analysis of variance and principal component analysis. Forms of Fe and AI
associated with cation exchange capacity and fine material supplied an
index which discriminated between soils of terraces of different ages.
Introduction
1 the study of the soils which represent
the terms of chronosequence
attention is concentrated on those
properties which depend on the time
involved in the formation of the soils.
To this aim numerous parameters
have been considered and used as indexes
of pedogenesis, sometimes correlated
with the age of the soils. Those
most used are certainly (i) the ratio
oxalate-extractable· Fe/dithionite-extractable
Fe (FeJFed) (ALEXANDER;
1970; ALEXANDER & HOLO­
WAYCHUK, 1~83; BRUNNACKER,
1970; TORRENT et al., 1980),.(ii) the
ratio Fed"Fe 0 /total Fe (NAGATSUKA
et al., 1983; ARDUINO et al., 1984),
and (iii) the relative proportions of
calcium bonded phosphorous and
easily reducible phosphorous
(BAUWIN & TYNER, 1957; GOD­
PREY & RIECKEN, 1954; HAWKINS
& KUNZE, 1965; SMECK NEIL,
1973; WESTIN & BUNTLEY, 1967).
YAALON (1975) suggested the application
of statistical. functions to
pedogenetic problems when the reactions
are very complex or when independent
factors cannot easily be pinpointed.
On this basis various authors
have developed regressiop
equations which relate the formation
time of soils to their characteristics
(RUXTON, 1968; SONDHEIM et al.,
1981; 1983). The statistical methods
used are normally analysis of
variance, factor analysis and nonlinear
regressions.
In this study numerical and statis-

1
474 E. Arduino, E. Zanini, E. Barberis, V. Boero, F. Ajmone Marsan
tical methods were applied to a chronosequence
with the aim of verifying
whether the extractable forms of Fe,
AI and P can be utilized as indicators
of the differing ages of soils developed
on fluvial terraces. To this
aim, the results of Principal Component
Analysis were interpreted (BAR­
MAN, 1967; WEBSTER, 1979), and
the principal factors . whose indexes
discriminated the success.ive terms of
the chronosequence were identified.
The soils· of chronosequence
The chronosequence studied (Fig.
1) consists of three fluvial terraces de-
nominated A1, Az and B, originated
from a p~g£1 -el~in f~n. i~~~ll~'Yestern
part of the Po Valley in the North of
Italy (45°27' to 45°31' N; 8°10' to 8°12'
E). The terraces overlie the same substratum
and are . at an elevation
above the present bed of the river
which originated them of 20-24 m for
A1, 12-16 m for A 2 and 3-4 m for B.
Although an absolute dating is not
available, it was possible to establish,
consistently with the international
scale of chronological correlation
(RICHMOND, 1982) that the terraces
A1 and Az were formed during the
Middle Pleistocene, that is between
0.73 and · 0.13 million years ago,
and specifically that A 1 is npt before
1
~ '
'
3
c=J
4
~
~ •
Fig. 1 -The area studied and sampling localities. 1: A1 Terrace; 2: A3 (reworked A2 sediments);
" 3: A2 Terrace; 4: B Terrace; e: Location of the profile.
km 3

On the Effectiveness of the Extractao[e-Forms of .. 475
0.30 m.y. ago, whereas terrace B originated
during the Upper Pleistocene,
that is between 0.130 and 0.010 m.y.
(CARRARO & FORNO, 1982). On
the three terraces, four profiles were
sampled, of which one was on A 1, one
on Az and two on B.
Materials and methods
Laboratory methods
The analytical data relative to the
profiles have already been published
(ARDUINO et al., 1982); from these,
together with the morphological
characteristics of the various horizons,
a classification emerged; Aquic
Fragiudalf, fine-loamy, mesic (A 1);
Aeric Haplaquept, loamy, mesi.c (Az);
\
Psammentic Udifluvent, loa~J.Y,
mesic (B) and Typic skeletal Udifluvent,
loamy, acid, mesic (B).
The data reported here concern Fe
and Al soluble in dithionite-citratebicarbonate
(Fed, Ald) obtained with
the MEHRA-JACKSON method
(1960), Fe and Al soluble in. oxalate
(Feo, Alo) obtained with the
SCHWERTMANN method (1964) and
the fractioning of inorganic P into P
bonded to Ca (Pea), to Al (PAJ), to Fe
(PF.) and lastly easily reducible or
occluded P (Po) (WILLIAMS, 1971).
The data concerning loam, clay
and cation exchange capacity were
obtained with the SISS (SOCIETA
ITALIANA DELLA SCIENZA DEL
SUOLO) method (1976). All the
analyses were performed on the

TABLE 1
Analytical data
I
I
I
-..j
""
""'
. !(
Depth PAl PFe Pea Poc Fed Fe 0 Alct Ala Silt Clay C.E.C.
Profile Horizon
~
cm pp m pp m pp m pp m % % % % % % meq/100 g ;J>.
i
it
!::
Al Ap 0- 30 52.9 122.0 70.2 96.1 1.90 I 0.43 0.41 0.16 41 26 11.2 s·
Blt 30- 56 21.6 19.6 10.9 52.4 2.24 0.28 0.52 0.13 so 30 8.8 $>
A'2g 56- 93 7.0 77.4 20.0 87.0 2.55 0.35 0.51 0.14 35 29 9.2 ~
B'21t 93-113 16.4 74.1 19.9 134.6 3.32 0.37 0.82 0.16 37 41 17.2 ., N
B'22x 113-146 15.8 60.1 22.0 130.0 3.59 0.30 0.60 0.15 46 36 21.4 ;s
B'23x 146-183 23.9 103.0 27.7 126.6 4.32 I 0.34 0.73 0.15 41 35 21.2 .,.... s·
B'24x 183-224 22.8 94.2 35.7 193.9 3.12 0.46 0.52 0.14 37 38 17.8
B'25x 224-165 57.7 165.4 36.7 156.2 3.36 0.94 0.66 0.22 35 38 21.8 ~
tJ:j
B'3 265-309 63.9 186.8 38.2 218.1 4.09 0.82 0.70 0.18 27 31 19.0 .,
Cl 309-337 144.7 230.0 126.4 194.4 3.29 0.80 0.61 0.19 36 25 15.9 ;;.
(I)
C2 337AOO 200.4 199.2 243.6 123.6 2.10 0.73 0.39 0.25 22 18 15.3 ;:!,
~
A2 Apl 0- 9 46.9 115.9 42.2 69.9 1.61 0.44 0.28 0.14 44 20 11.0
Ap2 9- 30 32.4 77.6 81.3 62.5 1.30 0.45 0.25 0.13 44 21 10.9 :.
~.
B Al 0- 20 39.1 109.7 143.7 34.9 1.97 0.66 0.29 0.20 34 18 18.4
Cl 30- 55 9.3 50.8 153.1 14.9 1.66 0.71 0.25 0.17 29 15 14.6
:::
0
;s
C2 60- 90 43.1 33.6 179.2 30.2 1.40 0.85 0.18 missing 23 10 )9.4
(I)
C3 90-115 35.0 72.1 182.8 0.0 0.82 0.47 0.16 0.11 18 9 i 7.6 ., ;s::
C4 115-140 30.0 58.8 223.2 0.0 0.49 0.28 0.11 0.07 11 4 14 6
CS 140-156 16.8 72.1 202.3 18.9 1.20 0.71 0.08 0.07 7 4 ! 4:5
.,
B' Ap 0- 30 134.4 156.8 125.4 6.0 1.02 0.46 0.19 0.10 44 15 I 9.6
Cl 30- 60 91.4 149:4 137.1 7.4 1.10 0.45 0.19 0.10 29 17 8.7
C2 60-150 133.9 156.6 126.0 5.7 1.40 0.50 0.26 0.13 23 18 0.0
~
;s

On the Effectiveness of the Extraefiible F onns of .. 477
capacity -Whereas the quantity of
particles below 50 Jlm increases in the.
more developed and less recent profiles,
the exchange cation capacity
does not always increase in correspondance
with the amount of clay,
due to the diversity of the clay minerals
present.
Fonns of Fe and Al- The quantities
extracted in dithionite, which
correspond to the elements no longer
in the crystalline lattices of silicates
increase in the older soils. The oxalate
is able to discriminate the forms
of Fe sufficiently well, showing that it
is the B horizons which are ;poorer in
the more «active» forms, but is less
efficient in this respect in the case of
Al.
Fonns of P - The quantity of P
bonded to Fe and to Al is greater in
the A and C horizons of the'pr~files;
quantities of p bonded to ea' and
occluded P differ widely among the
profiles, consistent with the situation
often described in the literature: as
pedogenesis progresses the occluded
forms of P increase and the more
soluble forms diminish.
Principal Component Analysis (PCA)
- PCA was performed on the parameters
listed in Table 1 and on the
differences Fect-Feo and Alct-Al 0 , taking
each horizon as an independent sample.
This analysis was performed
separately on two sets of variables: 1)
forms of P, fine particles, cation exchange
capacity, and 2) forms of Fe
and of Al, fine particles and cation
exchange c;;1pacity.
For the first set of variables (PCA 1)
two principal components were
found with eigenvalues greater than 1
and accounting for 83% of the total
variance, whereas for the second set
(PCA 2) only one component exceeded
the above mentioned threshold and
accounted for 80% of the variance
(Table 2).
The factor 1 scores for the two
analyses were found to be highly
correlated (r = 0.915; P = 0.001) and
TABLE 2.
Results from Factor Analysis (Principal components extraction)
COMPONENT LOADINGS
ANALYSIS: PCA.1 PCA.2 PCA.3
FACTOR: I II II
PAl -0.204 0.924 '"**''(* -0.138 0.931
PFe 0.133 0.955 **'~** 0.149 0.943
Pea -0.874 0:316 ****

I
478 E. Arduino, E. Zanini, E. Barberis, V. Boero, F. Ajmone Marsan
therefore it was decided to apply PCA
to all the available variables, again
taking each horizon as an independent
sample. This analysis (PCA 3)
produced two factors accounting for
83% of total variance. Except for PAl
and PFe, all the other properties were
. str~mgly corre!~ te_c:t~i!!J.. fac:!or 1.
The first factor of each analysis
tends to be the most explicative and
generalizing one, and this is confirmed
by the efficiency of variance
TABLE 3
Oneway analysis of variance of factor I from PCA.l by profile
ANALYSIS OF VARIANCE
Source DF ss MS F F PROB.
between groups 3 I6.972 5.657 I5.50 ~ 0.000
(profiles)
within groups 22 8.028 0.365
Total 25 25.000
SNK MULTIPLE RANGE TEST:(*) denotes pairs of groups significantly different at the 0.05
level.
PROFILES
B B' A2
AI mean (FACTOR I)
PROFILES
B
B'
A2
AI
,, ,,
*
*
*
*
-1.24
-0.78
0.40
0.67
TABLE 4
Oneway analysis of variance of Factor I from PCA.2 by profile
Source
between groups
(profiles)
DF
3
ANALYSIS OF VARIANCE
ss
MS
I6.573 5.524
F
F PROB.
I5.62 0.000
within groups
2I
7.427
0.354
Total
24
24.000
SNK MULTIPLE RANGE TEST:('') denotes pairs of groups significantly different at the 0.05
level.
PROFILES
B B' A2 AI mean (FACTOR I)
,
PROFILES B * * -1.13
B'
,,
* -0.89
A2
,,
* -0.15
~·:
AI
*
0.84

On the Effectiveness of the Extractable Forms of .. 479
TABLE 5
Oneway analysis of variance of factor I from PCA.3 by profile
ANALYSIS OF VARIANCE
Source DF ss MS F FPROB.
between groups 3 17.220 5.740 17.78 0.000
(profiles)
within groups 21 6.780 0.320
Total 24 24.000
SNK MULTIPLE RANGE TEST:('') denotes pairs of groups significantly different at the 0.05
level.
PROFILES
B B' A2 A1 mean (FACTOR I)
PROFILES
B
B'
A2 *
A1 *
,,
*
,,
~·:
-1.19
;,
-0.89
;,
-0.09
0.84
2 Factor I
200
300
•
-1
Data fitting to polynomial trends
.. A1: Y=0.02*X-5.3*10-S*X 2 -0.41;
• A2: Y=0.02*X-7.7*10-S*X 2 -0.65;
-2
0v 8: Y=-7.5*10- 3 *X-0.48;
Fig. 2- Polynomial trends of Factor I from PCA.2 with mean horizon depth of the profiles studied.

480 E. Arduino, E. Zanini, E. Barberis, V. Boero, F. Ajmone Marsan
analysis in differentiating groups of
horizons (profiles). In particular, the
factor 1 score of PCA 2 differentiated
better than did that of PCA 1, whereas
the factor 1 score of PCA 3 was as
effective as that of PCA 2.
In Tables 3-5 are shown the results
of the above analysis of variance
and the a posteriori Student­
Newmann-Kneuls Multiple Range
Test. As can be seen, factor 1 of PCA 1
differentiated the profiles of the most
recent terrace from those of terraces
A1 and Az taken together; factor 1 of
PCA 2 was more effective and differentated
also between profiles A1
and A 2·• The same effectiveness was
shown by factor 1 of PCA 3.
The conclusion which may be
drawn is that forms of Fe and Al
associated with cation exchange
capacity values and fine material·
quantities are able to supply an index
which discriminates between
soils of terraces of different ages.
This also appears evident observing
the factor 1 scores of PCA 2, plotted
according to the mean depth of
the horizons in the four profiles (Fig.
2). The behaviour of the single values
in the profiles of the three terraces
are neatly differentiated and well interpretable.
REFERENCES
ALEXANDER E.B., 1974. Extractable iron in relation to soil age on terraces along the Truckee River,
Nevada. Soil Sci. Soc. Amer. Proc. 38, 121-124.
ALEXANDER E.B., HoLOWAYCHUK N., 1983. Soils on terraces along the Cauca river, Colombia: I. Chronosequence
characteristics. Soil Sci. Soc. Am. J. 47, 715-721.
ARDUINO E., AJMONE MARSAN F., ZANINI E., BARBERIS E., 1982. Classificazione dei suoli della Baraggia
di Verrone (Provincia di Vercelli). Ann. Fac. Sci. Agr. Torino ~2, 297-328.
ARDUINO E., BARBERIS E., CARRARO F., FORNO M.G., 1984. Estimating relative ages from iron-oxides!
total-iron ratios of soils in the western Po valley, Italy. Geoderma 33, 39-52.
BAUWIN G .R., TYNER E.H., 1957. The distribution of nonextractable phosphorous in some Gray-Brown
Podzolic, Brunizem and Planosol soil profiles. Soil Sci. Soc. Amer. Proc. 21, 245-250.
BRUNNAKER J., 1970. Kriterien zur relativen Dtitierung quartarer Palaboden. Z. Geomorphol. Neue
Folge 14, 354-360.
CARRARO F., FoRNO M.G., 1982. Carta geologica della Baraggia di Verrone. Consorzio di Bonifica della
Baraggia Vercellese, Vercelli.
GooFREY G.L., RIECKEN F.F., 1954. Distribution of phosphorous in some genetically related loessderived
soils. Soil Sci. Soc. Am. Proc. 18, 80-84.
HARMAN H.H., 1967. Modern factor analysis. University of Chicago Press, Chicago. ,
HAWKINS R.H., KuNZE G .W ., 19.65. Phosphate fractions in some Texas Grumusols and their relation to
soil weathering and a,vailable phosphorous. Soil Sci. Soc. Amer. Proc. 29, 650-656.
KAISER H.F., 1958. The Vahmax criterion for analytical rotation in factor analysis. Psichometrika 23,
187-200.
KAISER H.F., CAFFRY J., 1965. Alpha Factor Analysis. Psichometrika 30, t'-14.
LAWLEY D.N., MAXWELL A.E., 1971. Factor Analysis as a statistical method. 2nd Edition. Butterworths,
London.
MEHRA O.P., JACKSON M.L., 1960. Iron oxides removal from soils and clays by a dithionite-citrate
system buffered with bicarbonate. Clays Clay Miner. 7, 317-327.
NAGATSUKA S., KANEKO S., IsHIHARA A., 1983. Soil genesis on the raised coral reef terraces of Iohigaki
and Okinawa-Islands in the Ryukyu islands, Japan. I. Relations among soils and geomorphic
plains and chronosequential change of soil chemical properties. Soil Sci. Plant Nutr. 29, 343-354.

On the Effectiveness of the Extractable Forms of .. 481
RicHMOND G.H., 1982. Il pleistocene media in !talia. Geogr. Pis. Dinam. Quat. 5 (1), 242-243.
RuxTON B.P., 1968. Rates of weathering of Quaternary volcanic ash in northeast Papua. Int. Congr.
Soil Sci. Trans. 9th (Adelaide, Austr.) 4, 205-213.
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'

Miner. Petrogr. Acta
Vol. 29-A, pp. 483-488 (1985)
Geochemistry of Available Micronutrients in Soils
from Vega de Velez, Malaga, Spain
A.RUIZ 1 ,S.JAIME 1 ,A.AGUILAR 1 ,E.BARAHONA 2 ,F.HUERTAS 2 ,J.LINARES 2
1 Estaci6n Experimental «La Mayora», C.S.I.C., Algarrobo-Costa, Malaga, Espaiia
2 Estaci6n Experimental del Zaidin, C.S.I.C., Profesor Albareda !, 18008 Granada, Espaiia
ABSTRACT- The Valley of the Velez River is located in the SW part ofthe
Malaga Province (Spain). The zone is used extensively for growing avocado
trees. This paper is a part of a more extensive study connected witn tne
availability of micronutrie'nts for this crop. The soils are mainly calcareous
Fluvisols with minor inclusions of calcic Cambisols and Luvisols.
Ninety soil samples were taken on a stratified random sampling scheme and
were studied for mineralogical and physicochemical properties. Available
Cu, Fe and B were chemically extracted.
The soils are rich in quartz and phyllosilicates and show a great homogeneity
in composition. Carbonates are generally under 10% and organic matter is
lower than 3%. Most soils are sandy loams. Available K increases with clay
content and diminishes with whole phyllosilicate content due to the presence
of the coarse fractions of phengite and paragonite micas.
Statistical analysis reveals that the extractable Cu (mean value 0.7 ppm)
depends mainly on the clay, carbonate and organic matter content. A fraction
of Cu must be'associated with Fe-oxyhydroxides since there is a significant
correlation between extractable Fe and Cu.
The extractable Fe (me~n value 3.3 ppm) is associated with carbonates. T~e
correlation with·organic matter and other mineral components is negative.
Finally, e'xtractable B (mean value 2.5 ppm) is related to organic matter,
carbonates and phyllosilicates. Part of the extractable B must be present as
soluble salts.
Infroduction
The Valley of the Velez River is located
on the southeastern part of the
Malaga Province (Spain). It occupies
an area of about 30 km 2 and is entrenched
between materials of the
Malaguide Complex (Cambrian to
Carboniferous), consisting of limestones,
greywackes, quartzites and
phyllites, 'and those from the ~lpujarride
Complex (Cambrian to Permo­
-Triassi.c) constituted by marbles,cmica
schists and quartzites.
The Velez River transported part of
these materials and deposited them
'in an extensive valley floor (vega)
which is the location selected for the
present study.
The soils derived from these materials,
are mostly used to grow subtropical
crops, especially avocado.
The present paper is part ofa more

484 A. Ruiz, S. Jaime, A. Aguilar, E.' Barahona, F. Huertas, J. Linares
extensive study of the factors governing
the mineral nutrition of the
crop.
A still little known subject, in this
respect, is the role played by micronutrients.
In this communication
preliminary results on available Cu,
Fe and B content in the soils as related
to- theiF-miner:alogk:al-GompGsition
are presented.
Materials and experimental methods
The soils formed from recent flood
plain deposits are mainly Fluvisols ..
A I p u jar r i de eo ri1 pIe X
M a I a g u id e Co m pI ex
MEDITERRANEAN
SEA
0 5 10 15 km
Fig.· i -L~c~ti~n of the sampling zone (dotted area)_

Geochemistry of Available Micronutrients in Soils ... 485
On some ondulating, and geomorphologically
older surfaces, more
strongly developed soils also occur,
such as calcic Cambisols and even
Luvisols.
Ninety samples of the plow layer
were tak~n, following a stratified random
sampling procedure (Fig. 1).
Mineralogical analyses were carried
out on the bulk samples by XRD
(powder method), using a Philips
1730 diffractometer. A semiquantitative
analysis was made using the reflecting
factors reported by BARA­
HONA (1974).
The available elements were extracted
with an aqueous acetiC acid
solution at pH 2.5 (ROMERO, 1981).
Organic matter was determined by
wet oxidation with potassium dichromate
(ANAL. METH. WORK.
GROUP, 1973). The mechan~cal
analysis was carried out with the
hydrometer method (BOUYOUCOS,
1951). Also, the conductivity of the
saturation extracts (CHAPMAN .&
PRATT, 1973) and the pH of the saturated
paste (ANAL.' METH. WORK.
GROUP, 1973) were determined as
well as available P (CAPITAN &
MARTINEZ, 1954), K(ANAL. METH.
WORK. GROUP, 1976) and total nitrogen
contents (ANAL. METH.
WORK. GROUP, 1973).
Experimental results and discussion,
The mean values and standard deviations
of the variables studied are
reported in Table 1.
The dominant textural class is sandy
loam. The mineralogical composition
of the soils is very homogeneous.
They are rich in phyllosilicates and
quartz, in agreement with the nature
of the parent materials. The carbonate
content is, generally, under 10%,
TABLE 1
Mean values (x) and standard deviations (s) of the variables studied (90 samples)
Extractable Cu pp m 0.66 0.28
Extractable Fe pp m 3.30 1.78
Extractable B pp m 2.55 1.24
Phyllosilicates % 58.64 8.42
Quartz % 30.44 7.37
Plagioclase % 4.24 1.65
K-feldspar % 0.31 0.72
Calcite % 5.17 4.20
Dolomite % 1.29 2.32
pH 7.41 0.25
Conductivity 2.68 1.39
Equivalent carbonate % 5.41 4.49
Organic Matter % 1.69 0.55
Nitrogen mg/100 113.95 31.98
PzOs mg/100 50.76 28.74
KzO mg/100 34.75. 21.61
Clay % 18.42 8.40
Silt % 28.82 9.95
Sand % 52.91 15.40
x
s

l
486 A. Ruiz, S. Jaime, A. Aguilar, E. Barahona, F. Huertas, 1. Linares
and calcite more abundant than dolomite.
Taking into account the correlation
between grain size separates and
mineral constituents, it .may be deduced
that the sand fraction (53%)
consists of 30% quartz, 4% plagioclase,
1% K-feldspar and 1% dolomite.
The silt fraction (29%) is constituted
by 27% phyllosilicates and 2% calcite.
They clay fraction is constituted
by 15% phyllosilicates and 3% calcite.
The pH values vary very little and
are governed by the assemblage
phyllosilicates-carbonates. The conductivity
of the saturation extract is
---------~ __ jnyersely_related to pH, probably because
as ionic strength increases,
more H+ ions are displaced from the.
exchange complex to the sGil solution.
The organic matter content is never
above 3% and is highly significantly
related to theN, P and B contents.
Available P and K are related to one
another. The latter depends mainly
on clay content but is independent of
the total amount-of-phyllosilicates in
the bulk sample, since these consist
partly of coarse mica fractions of
phengite and paragonite, ·derived
from metamorphic mica shists.
In order to study the relationships
between available elements and the
rest of the variables, a multiple linear
regression analysis was carried out.
Some selected results are summarized
in Table 2.
Extractable Cu is related to organic
matter, clay and carbonate content;
hence the Cu in the soil must occur
chiefly in the form of chelates, exchangeable
ions and carbonates.
Probably, Cu must also be associated
with Fe oxyhydroxides (not determined),
since there is a significative
correlation between extractable Cu
and Fe. From the partial regression
coefficients it may be deduced that
organic matter contributes 5.4, clay
1.3, calcite 3.1 and dolomite 1.3 ppm
per unit weight to the total extractable
Cu. By weighted adding of all
TABLE 2
Selected results of multiple linear regression analysis
Ext. Cu = 0.333 + 0.054 Organic Matter + 0.013 Clay
R = 0.404
Ext. Cu = 0.479 + 0.031 Calcite + 0.013 Dolomite
R = 0.495
Ext. Fe = 2.183 + 0.191 Calcite + 0.099 Dolomite
R = 0.474
Ext. B
Ext. B
-0.968 + 1.300 Organic Matter + 0.049 Clay + 0.014 Silt
R = 0.715
-17.237 + 2.239 pH+ 0.258 Conductivity+ 0.060 Equivalent CaC0 3 + 0.010 N +
+ 0.017 P20s + 0.003 K20 .
R = 0.726
The correlation coefficients are significant at 0.01 level

Geochemistry of Available Micronutfie-iits in Soils ... 487
contributions, a value for Cu is
obtained that closely resembles the
observed mean values.
Extractable Fe is significantly related
to carbonate content. According
to the regression coefficients, the unitary
contributions of calcite and
dolomite are 19.1 and 9.9 ppm Fe respectively.
Summing up both contributions,
the observed mean value
for Fe is not reached by far, this could
imply that a part of the extractable
Fe might be associated with Fe oxyhydroxides.
On the other hand, this
element is not accounted for by either
organic matter or phyllosilicates,
since the correlation coefficients are
negative.
There are two sources of extractable
boron, namely, organic matter
and clay. The unitary contributions
are ·130 and 4.9 ppm respectively.
Therefore, organic compounds ri2h in
B must be a fairly abundant component
in the soils of this region. It must
be taken into account that micas constitute
a potential source of ;B. This ,
element is hydrolyzed and concentrated
in neoformed clay minerals,
and in addition forr'ns complexes
with organic matter. By summing up
the weighted contributions of both B
sources, a value is obtained which is
higher than the observed mean value.
It could happen that the multiple regression
coefficients were distorted
by a concealed effect of soluble B.
It may be concluded that the
amounts of extractable Cu and B depend
mainly on the organic matter
content, and that of Fe, on carbonate
content. Cu is also partly related to
carbonates and clay, while B is related,
to a certain extent, to the clay
content.
In Table 3 values of extractable Cu
and B are compared with those
given in the literature. The values
found fall within normal ranges, so
that probably the soils are not deficient
in these elements.
Finally, since Fe is closely related
to carbonate content, it is of interest
to assess whether the concentrations
in· extractable Fe are in solubility
equilibrium with the corresponding
carbonate compound (siderite). The
reaction may be \Yritten as:
FeC03 + 2H+ ~ Fe 2 + + COz + HzO
log K = 7.92 (LINDSAY, 1979)
Assuming that the soil moisture
content is about 10 percent, a con-
TABLE 3
ppm values of extractable Cu and B compared with those given in the literature
This Paper 2
Cu 0.66 2.9 0.06-0.3
(0.002-19.2)
B 2.55 1.9 0.1 -2
(0.01-130)
1: from FAIRBRIDGE & FINKL (1979); 2: from AUBERT & PINTA (1971); Numbers in
parentheses give the ranges of variation

1
488 A. Ruiz, S. Jaime, A. Aguilar, E. Barahona, F. Huertas, J. Linares
centration of 10·3·23 M for extractable
Fe is obtained. Since the dominant
texture is loamy sand, the soils
should be well aerated and their C02
content should be very close to that of
the free atmosphere (10·3·5 atm). Consequently,
substituting this value in:.
log K = log Fe + log C02 + 2 pH
we QP.t

Miner. Petrogr. Acta
Vol. 29-A. pp. 489-498 (I 985)
Geochemistry of Soils from Peridotite
in Los Reales, Malaga, Spain
A. YUSTA 1 , E.BARAHONA 2 ,F.HUERTAS 2 , E.REYES 2 ,J. YANEZ 2 ,J.LINARES 2
1 Departamento de Qufmico-Ffsica, Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071
Malaga, Espaiia
2 Estaci6n Experimental del Zaidfn, C.S.I.C., Profesor Albareda I, 18008 Granada, Espaiia
ABSTRACT- Los Reales mountain belongs to the Ronda ultramaphic complex
and is located near the southern coast of Spain. The peridotites are partially
serpentinized in some places.
A soil profile representative of the zone studied was sampled. The soils are
Chromic Cambisols or Typic Xerochrepts. For the geochemical and mineralogical
study samples of fresh rocks, altered fragments (gravels included
within the soil) and soil horizons were taken.
The fresh rocks are composed of olivine, enstatite, diopside and serpentine.
Since the primary minerals have nearly constant chemical compositions, the
calculation of a mineralogical norm was feasible, and the structural formula
of serpentine was deduced. These results checked against diffractometric
data allowed reflecting power factors to be obtained for these minerals, in
order to facilitate their semiquantitative determination by XRD analysis.
In altered rocks, in addition to primary minerals, a trioctahedral smectite
\saponite) was found.
The soils are rich i~organic matter. The exchange complex is dominated by
magnesium and the degree of saturation is always high. Free iron oxyhydroxides
are abundant and they concentrate in the B horizons. In the upper
horizons small quantities of quartz and chlorite of eolian origin are found.
It can be concluded from mass balance calculations that a 54% loss occurred
for the transformation of fresh to altered rock while the loss for the transformation
from fresh rock to soil was 63%. Important amounts of serpentine,
olivine, Cr, Zn .and Co are lost.
Introduction
The peridotite exposure occurring
at Los Reales is located in the Ronda\
ultrabasic complex and belongs to
the inner zones of the Betic Ranges.
This complex extends over about 300
km 2 , near the southern Spanish
coast. In places, the peridotite body is
partially serpentinized by a subsequent
process of metasomatism
(TORRES, 1979). This zone has been
studied by several authors, among
them DICKEY (1970) and. OBATA
(1979), who determined the chemical
composition of olivines, ortho- and
clinopyroxenes and of some other
accessory minerals (spinel, garnet,
amphibole, etc.); in all cases, minimal
compositional changes were found.
The purpose ofthis study is to gain

490 A. Yusta, E. Barahona, F. Huertas, E. Reyes, J. Yanez, J. Linares
some knowledge of the matter balance
associated with the processes of
surficial alteration of peridotites.
The ease with which the primary
minerals of these rocks an~ destroyed
permits the important losses of matter
in these processes to be studied. In
addition, it is possible to determine
the mobilization of trace elements
associated with these minerals.
Furthermore, given the small variation
in the chemical composition of
olivines, pyroxenes, etc., a calculation
of the mineralogical norms can
be made. These results, checked
against diffractometric data allow re'!.
fleeting power factors to be obtained
__________ for _these minerals, in order to facilitate
their semiquantitative determination
by XRD analysis.
Materials and experimental methods
The sampling site is located near
the top of Los Reales mountain where
the colluvial cover is minimal and
the soils show well developed weath-.
ering horizons.
Soil profile description
Classification: Chromic Cambisol,
Typic Xerochrept. Location: Los
Reales, Malaga. Topographic sheet
1071, UTM coord.: 029398. Physiographic
position: Sideslope near the
mountain top. Elevation: 1300 m.
Slope: Steep (28%). Vegetation: Coniferous
forest (Pinus pinaster sol.).
I
Parent material: Peridotite residuum.
All 0-1:3 cm:· Dark-reddish brown
(5YR 3/3) silty loam (moist), strong
fine granular structure, slightly plastic,
very friable, common coarse fragments
(stones and gravels), many fine
pores, many fine roots, clear smooth
boundary.
B21 13-25 cm: Dark reddish brown
(2.SYR 3/4) loam, moderate medium
subangular blocky structure, moderately
plastic, friable, few gravels,
frequent fine pores and fine roots,
smooth gradual boundary.
B22 25-40 cm:· Dark red (5YR 3/6)
silty loam, moderate medium subangular
blocky structure, no clay
skins are visible, moderately plastic,
friable, few gravels, frequent fine
pores and very fine roots, smooth gradual
boundary.
B31 40-60 cm: Strong brown
(7.5YR 3.5/6) loam, weak medium
subangular blocky structure, no clay
skins, moderately plastic, friable,
some ston"es, few pores, few roots,
gradual wavy boundary.
B32 60-70 cm: Yellowish brown
(lOYR 4.5/6) loam, very weak
medium subangular blocky structure,
moderately plastic, friable,
abundant rock fragments (40% vol),
gradual wavy boundary. ,
Cl 70-100 cm: Light olive brown
(2.5Y 5/4) sandy loam with common
yellowish red streaks, massive,
slightly plastic, horizon truncated
laterally by hard rock.
C2 100-130+ cm: Light olive brown
(2.5Y 5/4) loamy sand (saprolite) with

common yellowish red streaks, massive,
non plastic, friable, truncated
laterally by hard rock.
Master horizons. were sampled for·
laboratory determinations, and, in
addition, a more detailed sampling
was made in a nearby site, with identica.l
profile characteristics. Here, the
horizons were subdivided into a total
of 14 soil samples.
Nine samples of fresh rock, not
showing signs of external alteration,
were takeri. Also, gravel~ occurring in
each horizon were sampled as well as
a rock showing distinct evidence of
alteration, so that the different
weathering stages would be represented.
The mineralogical analysis was
carried qut by XRD. For fresh
rock mineralogical semiquantitative
analysis, the starting point ~as the
"
mineralogical norm, calculated from
"
chemical analysis of rocks, taking
into account the composition of
different minerals (Table 1). The
percentages so obtained were checked
against the areas of diagnostic
Geochemistry of Soils from-Peridotite ... 491
peaks for minerals. Finally, the following
reflecting power factors were
obtained: diopside = 1.7; enstatite,
olivine and serpentine = 1, for the J
2.99, 2.87, 2.64 and 7.3 A reflections,
respectively. These values are in
accordance with the respective
«mass attenuation 'coefficients»,
(MAC).
For the mineralogical analysis of
altered rocks, the linear regressions
between mineral percentages and the
_corresponding diagnostic peak areas,
for fresh rock samples, were calculated.
For the amphibole, in accordance
with its MAC, a reflecting power
factor of one was assumed. From diffractometric
data, the percentages of
primary minerals were calculated by
using the above mentioned regression
equations. The rest (up to 100)
was exf1ressed as free iron oxyhydroxides
(previously determined by
chemical analysis) and as smectite
neoformed by alteration.
' For carrying out the mineralogical
analysis of soils, the regression between
smectite content and the 17 A
peak area (i.e. solvated) was calculated.
By using this equation and the
above mentioned ones, the percentages
for mineral components were
calculated. The remainder up to 100
was expressed as free iron oxyhydrox- .
ides (chemically determined) and as '
chlorite and quartz, using in this case
the reflecting power factors obtained
by BARAHONA (1974).
The chemical analysis of major elements
was carried out with the
method given by HUERTAS & LI­
NARES (1974). Trace elements were
determined by atomic absorption
and arc spectrography following the
method of LACHICA & YANEZ
(1974). ·Free iron was determined
according to HOLMGREN's (1967)
method. Exchange cations and CEC
were determined by the NH4Ac
method. Statistical analysis of the
data was done by computer, using
programs implemented by E. BARA­
HONA (pers. comm.). Surface area
measurements were carried out following
the method of KEELING
(1961).

-.
492 A. Yusta, E. Barahona, F. Huertas, E. Reyes, J. Yanez, J. Linares
Experimental results and discussion sample, which is. chemically and
mineralQgi~aJJy~~~O~ll~!~_t_e_JlLWitl;l~ the_
Fresh rock following mineralogical composi-
The chemical composition of oli- tion: 96% serpentine, 3% diopside
vine (Fo90Fa10) and that of enstatite and 1% free iron. The chemical con-
(En91Fe9) was established using the tribution of diopside and free iron
methods outlined by AGTERBERG was subtracted from the chemical
(1964) and HIMMELBERG & JACK" analysis of sample R-0, to obtain the
SON (1967) respectively. The results composition of the serpentine (Table
obtained are within the range pre- 1).
viously found by DICKEY (1970) and Chemical analyses of pure minerals
OBATA (1979). The chemical corn- and fresh rocks are listed in Table 1.
position of serpentine was deduced The mineralogical composition of
from the mineralogical norm of R-0..,, samples is given in Table 2. Reported
TABLE 1
Chemical analyses
-·-------·-····-----
Sample Si0 2 Alz03 Fe203 Ti0 2 M gO CaO Na 2 0 KzO Hzo+ Total
R-0 40.52 0.91 7.45 0.0 37.41 1.43 0.16 0.01 12.43 100.32
R-1 40.95 2.41 7.21 0.0 39.01 2.37 0.31 0.19 7.15 99.60
R-2 42.45 3.17 8.44 0.21 36.20 3.89 0.84 0.02 5.15 100.37
R-3 41.14 1.48 8.87 0.0 38.59 2.64 0.57 0.20 7.20 100.69
R-4 40.34 2.17 6.28 0.0 41.25 2.54 0.60 0.10 7.55 100.83
R-5 41.44 2.38 . 6.35 0.0 40.64 2.07 0.44 0.14 7.18 100.64
R-6 41.16 2.08 7.01 0.0 39.26 2.46 0.73 0.05 7.71 100.46
R-7 39.93. 1.75 8.72 0.0 39.20 1.67 0.48 0.08 8.06 99.89
AR-1 42.73 1.13 8.57 0.0 37.33 2.83 0.56 0.12 6.52 99.79
AR-2 46.67 3.53 9.12 0.44 28.34 4.03 0.71 0.11 7.22 100.17
AR-3 48.90 3.44 8.67 0.41 24.80 6.79 0.91 0.10 6.03 100.05
AR-4 40.94 7.80 8.01 0.39 25.20 8.97 0.71 0.18 7.39 -99.59
AR-5 45.60 3.08 7.83 0.24 29.09 6.64 0.81 0.08 7.06 100.43
AR-6 47.34 3.07 6.42 0.37 28.31 8.40 0.46 0.19 5.47 100.03
AR-7 41.24 3.22 6.62 0.20 28.71 12.53 0.86 0.10 5.80 99.28
AR-8 41.50 4.50 9.01 0.69 33.95 2.60 0.46 0.16 7.14 100.01
All 42.21 6.87 13.10 0.27 25.72 3.75 0.42 0.27 7.20 99.81
B21 40.60 7.77 14.24 1.02 24.37 3.40 0.83 0.29 7.44 99.96
B22 43.87 7.18 14.28 0.39 22.62 4.14 0.83 0.21 7.08 100.50
B31 43.82 6.56 13.15 0.38 22.22 4.64 0.73 0.18 7.05 100.23
B32 43.34 7.00 13.06 0.32 22.57 5.33 0.75 0.18 7.36 99.91
Cl 44.47 7.45 5.99 0.34 25.21 9.17 0.83 0.07 6.09 99.62
C2 42.87 7.04 6.82 0.21 29.73 6.16 0.87 0.06 6.03 99.79
Olivine 42 7 51 100
Enstatite 53 6 7 33 1 100
Diopside 53 6 3 16 21 1 100
Am phi bole 44 14 4 2 18 12 4 2 100
Serpentine 41 2 6 37 14 100
Samples R-0 to R-7: fresh peridotite rocks; samples AR-1 to AR-8: altered rocks; samples All
to C2: soil horizons; chemical compositions of primary minerals after OBATA (1979), for
serpentine see text

Geochemistry of Soils from.Peridotite ... 493
TABLE 2
Mineralogical compositions
Sample Sapo. Serp. Diop. Enst. Oliv. Amphib. Free Fe Chlor. Quar.
R-0 96 3 1
R-1 44 8 15 31 t 2
R-2 40 9 18 31 t 2
R-3 52 5 16 24 t 3
R-4 52 5 12 29 t 2
R-5 43 8 14 33 2
R-6 42 8 16 32 2
R-7 42 6 "19 31 t 2
AR-1 21 20 5 30 19 2 3
AR-2 12 15 12 22 32 4 3
AR-3 43 t 15 18 10 11 3
AR-4 32 5 11 37 12 t 3
AR-5 25 9 19 22 17 5 3
AR-6 14 3 20 37 15 8 3
AR-7 13 7 37 27 11 2 3
AR-8 14 18 17 16 28 4 3
All 22 6 4 20 17 5 9 9 8
B21 18 3 4 19 7 10 11 12 16
B22 22 5 9 26 11 6 12 5 4
B31 23 8 6 26 10 8 10 5 4
B32 31 9 7 31 8 4 10
Cl 46 3 6 22 5 10 8
C2 32 4 17 38 6 2 1
Sapo.: saponite; Serp.: serpentine; Diop.: diopside; Enst.: enstatite; Oliv.: olivine; Amphib.:
amphibole; Chlor.: chlorite; Quar.: quartz; t: traces
"'- TABLE 3 .-
Trace element contents (ppm), fre~ iron oxyhydroxides (%) and surface area (m 2 /g) values
Sample Cr Zn Co Ni Mn B V Fe S.A.
R-0 540 383 129 2169 378 25 20 0.63 82
R-1 1453 220 209 2300 755 8 36 1.71 89
R-2 1438 375 lSQ 2368 750 2 115 2.29 115
R-3 1770 363 219 4890 730 1 40 3.08 132
R-4 1213 154 233 2181 678 2 32 1.50 49
R-5 1118 141 201 2081 728 2 63 1.58 48
R-6 1248 247 225 2059 688 6 19 1.17 46
R-7 1178 147 184 2119 810 2 28 2.96 so
AR-1 1780 320 162 2523 863 1 42 1.58 so
AR-2 1825 453 139 2334 930 5 75 2.83 110
AR-3 2035 303 222 1701 678 2 10 3.00 200
'AR-4 2938 233 141 2010 928 15 79 n.d. 248
-AR-5 2358 249 298 3052 1055 4 15 n.d. 135
AR-6 2008' 372 255 1715 985 2 174 n.d. 87
AR-7 2023 285 234 2117 869 2 200 n.d. 105
AR-8 2728 132 284 2952 985 2 132 n.d. 239
All 3717 120 354 2655" 1710 19 91 9.17 202
B21 4460 135 331 2953 1330 2 200 10.25 103
B22 2928 88 293 2855 1208 3 100 11.05 225
B31 3080 258 355 3021 1185 3 125 7.70 238
B32 2658 117 284 2233 lOOS 17 72 3.91 271
Cl 2398 173 258 1734 738 2 166 0.96 268
C2 1833 121 220 1247 833 6 150 1.22 239
Fe: free iron oxyhydroxides;_ S.A.: surface area

494 A. Yusta, E. Barahona, F. Huertas, E. Reyes, J. Yafiez, J. Linares
in Table 3 are the trace element and
free iron oxyhydroxide contents as
'well as the surface area val~es of the
samples.
Taking into account the variable
associations evidenced by an R-mode
Factor analysis with Varimax rotation,
a set of multiple linear correlations
and regressions was calculated.
Some of the results will be discussed
below.
The regression coefficients corresponding
to the regression between
serpentine and the rest of minerals
indicate that this mineral is derived
mainly from the transformation of
diopside and, to a lesser extent, that'
of enstatite and olivine (%serpentine
·······- ··----;;-·91.48. --l :2.5% -dfopsfde :::-6.96% ·enstatite
- 0.78% olivine, R = 0.999).
Free iron contains a sizeable
amount of several trace elements,
probably in an occluded form (i.e.: %
free iron = 0.35 + 0.003 Zn (ppm) +
0.001 Co (ppm), R = 0.985).
In some of the regression equations
between J[i!.C~:u~le_Il1enJ§ and i:r.tinerals,
the independent term is very
high, probably due to the presence of
minor quantities of Cr- and Ni-bearing
spinels, not accounted for in the
mineralogical analysis by XRD (i.e.
Cr (ppm) = 518.18 + 357.32% free
iron + 3.32% serpentine, R = 0.923).
From the multiple regressions between
the trace elements and mineral
assemblage in fresh rocks it was
feasible to calculate the unitary contributions
of each mineral to the
trace element contents. The data
listed in Table 4, where the mean
values for all samples studied are
given (fresh and altered rocks and
so-ils) were calculated from these contributions.
There is good agreement
between the values obtained by statistical
analysis and those determined
partially by DICKEY (1970)
and OBATA (1979) using the electron
microprobe. These results are also in
TABLE 4
Mean trace element contents in minerals
Element Serp. Diop. Enst. Oliv. Am phi b. Spin. Sapo. Chlor. Fe Perid.
Cr (1) n.d. 3563 1567 n.d: 3962 71156 n.d. n.d. n.d. 1231
Cr (2) 2658 . 2395 12000 3671 n.d. 1182 13500 3.5% 1348
Mn (1) n.d. 723 1152 n.d. 529 2224 n.d. n.d. n.d. 928
Mn (2) 5058 814 960 6303 618 n.d. 5095 7620 748
Ni (1) n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 2069
Ni (2) 4344 734 3977 10610 n.d. 11342 1.5% 2184
Zn (2) 1000 60 855 n.d. 140 85 5% 235
Co (2) 297 435 64 518 n.d. 813 900 203
V (2) 600 315 1575 n.d. 190 3430 47
(1) mean data from DICKEY (1970) and OBATA (1979); (2) this paper: statistical approach;
n.d.: not determined; -: absence of statistical signification

Geochemistry of Soils from Peridotite ... 495
. TABLE 5
Structural formulae for saponites
Si IV Al 1 v Fe 1 v
Gravel 6.76 1.20 0.04
Lower horinzons 6.57 1.30 0.13
Upper horizons 5.92 1.87 0.21
AlVI MgVI Fe VI x+ Ozo(OH)4
5.24 0.57 1.05 )}
0.11 5.12 0.60 1.06 >>
0.15 5.24 0.60 1.35 )}
agreement with data reported by
WEDEPOHL (1968-1978) for minerals
and rocks of the same type.
Altered rocks
In the altered rock fragments
(gravel included in soil horizons) in
addition to the minerals occurring in
fresh rocks, a trioctahedral smectite
and an amphibole were found, the
latter being almost undetectable in
X-ray diffractograms of fresh rocks.
The results of the mineralogical
analysis are shown in Table 2. The
components existing in each mineral "
species were derived from the chemical
analyses (Table 1) and using
this information it was possible to determine
the chemical composition of
the smectite, which corresponds to
that of a saponite (Table 5).
Soils
By their characteristics, the soils
can be classified as Chromic Cambisols
(FAO, 1977) or ~ypic Xerochrepts
(SOIL SURVEY STAFF, 1975).
The organic matter is well humified
(Table 6) and the pH is nearly
neutraL The exchange complex is
dominated by magnesium and the
degree of saturation is a~ways high.
The Fe oxyhydroxides are abundant
and they concentrate mainly in B
horizons. In the upper horizons, in
addition to minerals occurring in
fresh and altered rocks, small quantities
of quartz and chlorite (Table 2)
are found. Based on their grain size
(silt); both the chlorite and quartz
probably originated from Saharian
dust of eolian origin. The chemical
compositions of saponite and chlorite
TABLE 6
Analytical data for soils
All B21 B22 B31 B32 Cl C2
Sand% 26.96 30.13 29.96 35.97 37.15 53.68 67.65
Silt% 52.61 44.35 52.48 45.16 42.31 32.41 27.26
Clay% 20.19 25.12 17.33 18.65 20.24 13.85 4.93
pH 6.50 6.75 6.85 6.95 6.95 6.95 7.05
Organic Matter% 12.61 2.57 \ 1.26 0.90 0.57 0.20 0.30
N 336.7 123.2 86.8 123.2 43.4 22.4 86.8
C!N 21.77 12.13 8.44 4.25 7.64 5.19 2.01
C.E.C. 35.40 20.20 24.20 27.70 34.70 24.20 30.90
Ca 5.99 1.25 0.75 0.50 1.25 1.00 1.00
Mg 20.81 12.01 13.66 18.34 26.82 23.28 24.68
Na 0.54 0.53 0.52 0.52 0.53 0.52 0.51
K 0.21 0.06 0.04 0.05 0.06 0.03 0.03
Saturation % 78 69 62 70 83 100 85

496 A. Yusta, E. Barahona, F. Huertas, E. Reyes, J. Yafiez, J. Linares
we!'e obtained by subtracting from
the chemical analysis (Table 1) the
components ascribable to minerals of
known composition, taking into
account the percentages of each present.
Regression equations relating
oxide percentages to saponite content
were derived from the remaining
components, recalculated to give a
total of 100. Extrapolation to a value
of zero for saponite gave the composition
of chlorite and the composition
of saponite was obtained from the remainder.
On the other hand, extrapolation
to a value of 100 for saponite
did not give sensible results. Two
types of saponite were distinguished,
corresponding to (i) the upper and (ii)
---~ --· -----the1owernorizons_---- -- - ·-
Minerals found in the sand, silt and
clay fractions of the soil were the following:
sand - diopside, olivine, enstatite,
amphibole and quartz; .
silt - amphibole, quartz and all the
other minerals found in the clay fraction;
clay - serpentine, chlorite, saponite
and quartz.
It can be deduced from the regression
equations that the organic matter
contains about 8600 ppm Cr, 564
ppm Co, 3175 ppm Ni, 5900 ppm Mn
and 106 ppm E, while the free iron
oxyhydroxides. contain 14700 ppm
Cr, 16000 ppm Ni, 180 ppm Zn, 900
ppm Co and 3190 ppm Mn (i.e.: Cr
(ppm) = 1512.36 + 86.02% organic
matter + 146.96% free iron, R =
0.789; Ni (ppm) = 898.20 + 31.73%
organic matter + 161.72% free iron,
R = 0.88:J:)~~-____ ---~-
Balances of matter
Using the mean values of the chemical
analysis data, the iso-oxygen
calculation of EARTH (1948) was performed
for fresh and altered rocks
(Table 7). In this way a global matter
loss of 54% was obtained, with important
losses of Si and Mg and, to a
lesser extent, Fe. A matter balance
made upon mineralogical data, and
based on the assumption that diopside
remains constant, resulted in an
overall loss of 56%. The most important
losses correspond to serpentine
and olivine (Table 9). As regards trac:e
elements, important amounts of Ni,
Co, Mn and Zn are lost (Table 8).
Earth's balance was also applied to
the stage of transformation of fresh
rock to soil (Table 7). In this case a
mean loss of 63% was obtained. The
mineral losses correspond to serpentine,
diopside and olivine, and to Si,
Zn, Ni, Co and Mn (Tables 8 and 9).
Consequently, it can be stated that
the most important step in the surficial
alteration of peridotites takes
place in the transformation of fresh
rock to altered gravels, since in the
subsequent transformation of the latter
to soil only an additional )oss of
8% occurs.·
The data obtained allow us to deduce
that 430 kg serpentine, 260 kg
olivine, 60 kg enstatite and 40 kg
diopside are lost per ton of peridotite
transformed into soil. A loss of 2206
g Ni, 867 g Cr, 218 g Zn, 158 g Co and
28 g V also occurs. At the same time

-------- ---·---~-~-------------
------------·
----------------
--
TABLE 7
Ions in 160-oxygen rock cell (Barth balance)
Si AI Fe n Ca Mg Na K
/
Fresh rock 38.05 2.40 5.12 /0.09 1.57 50.53 0.12 0.09
Altered rock* 18.21 2.40 2.64 0.08 2.08 18.69 0.24 0.08
Weight of fresh rock/ 1065 65 286 4 63 1228 3 4
Weight of altered rock 527 65 147 4 83 454 6 3
Weight loss (fresh-altered rocks) 538 0 139 0 -20 774 -3 1
Soil* 14.68 2.40 3.47 0.07 1.22 12.82 0.20 0.12
Weight of soil 411 65 194 3 49 311 5 5
Weight loss (fresh rock-soil) 654 0 92 1 14 917 -2 -1
a) Weight loss for fresh to altered rock tranformation = 54%
b) Weight loss for fresh rock to soil transformation = 63%
* Balance for Al constant
H 0
40.47 160
9.67 71.11 .
41 2560
10 1138
31 1422
9.61 57.31
10 917
31 1643
Total
138.44
54.09
5319
2437
2882
101.90
1970
334Q

-,
498 A. Yusta, E. Barahona; F. Huertas, E. Reyes, 1. Yanez, 1. Linares
TABLE 8
Trace elements. Balance of matter
Cr Zn Co Ni Mn B V
Fresh rock 1348 235 203 2571\ 748 3 47
AI tered rock* 968 128 95 1006 399 2 40
Weight loss (fresh-altered rocks) 380 107 108 1565 249 1 7
Soil* 481 17 45 365 182 19
Weight loss (fresh rock-soil) 867 218 158 2260 566 3 28
* Balance for Al constant
TABLE 9
Mineralogical balance
Serp. Diop. Enst. Oliv. Amphib. Fe Sapo.
Fresh rocks 45 7 16 30 t 2 0
Altered rocks 5 7 11 8 2 1 10
Soils 2 3 10 4 3 4 11
Mineral balance * (rock-soil) -43 -4 -6 -26 +3 +2 +11
* losses (-); gains ( +)
110 kg of saponite are formed, and a
relative enrichment of 30 kg amphibole
and 20 kg free iron oxyhydroxides
takes place.
REFERENCES
AGTERBERG F.P., 1964. Statistical analysis ofX-ray data for olivine. Mineral. Mag. 33, 742-748.
BARAHONA E., 1974. Arcillas de ladrilleria de la provincia de Granada: Evaluaci6n de algunos ensayos
de materias primas. Ph. D. Thesis, University of Granada.
BARTH T.W., 1948. Oxygen in rocks: a basis for petrographic calculations. J. Geol. 56, 60-61.
DICKEY U.S., 1970. Partial fusion products in alpine type peridotites: Serrania de Ronda and other
examples. Min. Soc. Amer. Special Paper 3, 33-49,
F.A.O., 1977. Guias para la descripci6n de perfiles de suelos. F.A.O., Roma. .
HIMMELBERG G .R., JACKSON E.D ., 1967. X-ray determinative curve for some orthopyroxenes. U .S. Geol.
Surv. 575, 101-102. ·
HoLMGREN G.G.S., 1967. A rapid citrate-dithionite extractable iron procedure. Soil Sci. Soc.Amer.
Proc. 31, 210-_211.
HuERTAS F., LINARES J., 1974. Analisis quimico de rocas y minerales. Report-Tnterno. Estaci6n Experimental
del Zaidin, C.S.I.C., Granada. · -
KEELING P.S., 1961. The examination of clays by !LIMA. Trans. Br. Ceram. Soc. 60, 217-244.
LACHICA M., YANEZ J ., 197 4. Analisis de elementos traza en minerales y rocas. Report interno, Estaci6n
Experimental del Zaidin, C.S.I.C., Granada.
0BATA M., 1979. The Ronda peridotite: garnet, spine/ and plagioclase lherzolite facies and the P-T'
trajectories of a high-temperature mantle intrusion. J. Petrology 21, 933-948.
SOIL SURVEY STAFF,'1975. Soil Taxonomy. U.S. Dept. Agric.
TORRES R.L., 1979. La evoluci6n tecti:mometam6rfica del macizo de Los Reales. Ph. D. Thesis,
. . University of Gra?ad!J:c.. Spair:. . .. _ _ _ .·=- ,. .
: WEDEPOHL K.H., 1968-78. Handbook ofGeochemistry. Springer-Verlag, Berlin.

Miner. Petrogr. Acta
Vol. 29-A, pp. 499-509 (1985)
The Effect of Gypsum on the Poral System
Geometry in Two Clay Soils
A.B. DELMAS 1 , C. BINP, J. BERRIER 1
1
Laboratoire des Sols, Station Centrale d'Agronomie, C.N.R.A., Etoile de Choisy, Route de Saint-Cyr, 78000
Versailles (Yve!ines), France ..
2
Istituto di Geopedologia e Geologia ,Applicata, Fa.colta di Scienze Agrarie e Forestali, Universita di Firenze,
Piazzale delle Cascine 15, 50144 Firenze, Italia
ABSTRACT - This work is devoted to the study of the reorganization of the
para! system in clay materials subjected to a wide range of calcium concen-.
tration.
By SEM observations it is shown that as calcium level increases, both a
modification of the domains in the samples, and a re-organization of the
para! system appears, concerning shape, size, arrangement of pores and clay
particles.
A tentative explanation of the observed phenomena, linked to the diffusion
process, is given. Possible consequences both in the weathering/pedological
field and in the engineering/agronomical one are suggested.
Introduction
The present necessity for increasing
agricultural production has
addressed recent agronomic technology
towards the utilization of
lands with high limitations (e.g. clay
soils).
There is already a literature on the
technology concerning the improve- .
ment of alkaline soils (CHISCI et al.,
1978; BUSSIERES et al., 1982).
On the contrary, adequate experimentation
concerning the reclamation
of acid soils (which are widely
diffused. especially in the tropical- .
equatorial zones) has not yet been
carried out (JANOT, 1983).
The improvements accomplished
are usually attributed to exchange
phenomena between Ca 2 + and the
ions Na+, and Mg 2 +, and to the soil
solution concentration.
In the case of soils whose exchange
complex is often saturated in calcium,
the sole cation exchange processes.
seem to be inadequate to explain
the accomplished improvez:nents
(GUYOT et al., 1984).
This paper deals with a laboratory
e~perimental study carried out on
two acid clay soils. The purposes
are to control the poral system
Research carried out with the financial support of M.P.I. 40%: «Capacita d'{rso dei suoli argillosi».

~
500 A.B. Delmas, C. Bini, J. Berrier
re-organization after treatment with
gypsum crystals, as well as to evaluate
the effect of gypsum on the structural
behaviour and its pedological
and agronomical implications.
Materials and methods
Samples of the B horizon of two
desaturated clay soils - a brown
leached soil and a red fersiallitic one
- developed on calcareous rocks in
the Jura Region (France) were hom9-
genized and intensively mixed with a
limited amount of distilled water, in
order to standardize the materials.·
The physical, mineralogical and
. --- -·------chern.icalcharactedstics ofth.e samples
are shown in Table 1.
Subsequently, several fractions
(lOO gr) of the standardized materials
were subjected to mechanical pressure.
The pressure was increased until
the humidity and pF of the samples
approached those of the soil in the
field (2 bars).
Standard cylindrical sticks 0 40
mm and 50 mm high, such as to reproduce
the soil aggregates in saturation
conditions, were thus obtained.
The sticks wer~ coveted with a parafilm
membrane and held in a closed
chamber, at constant remperature
(10 °C), in order to impede the desiccation.
Subsequently, gypsum monocrystals
were laid on one end of the soil
polyhedra, at different periods of
time (from 7 to 90 days), and constant
temperature (10 °C). In this way, a
range of calcium concentration diffusing
in the clayey materials was
obtained from the slowly dissolving
mineral.
At the planned deadline of the
treatment, the residual gypsum was
retrieved and the dissolution features
have been observed by SEM.
Each clay stick was cut into small
disks 5 mm thick, and subjected to
physical and chemical analyses
(humidity, pF, extractable calcium)
·as well as microscopic analyses by
SEM.
The SEM analyses were made with
a Jeol SM 35 microscope, while preserving
the humid conditions of the
samples, according to the cryoscan
technique (samples frozen at -40 oc
·with liquid nitrogen cooled by Freon
22: TESSIER & BERRIER, 1979).
Results and discussion
SEM-CRYOSCAN obse1Vations
a) Samples not treated with gypsum.
During the hydratation process,
the samples, subjected to the same
constant pressure (2 bars) showed
to react differently.
In the red soil water is rapidly
drained off, as the poral system
geometry seems to be quite rigid and
isotropic (Fig. la), since it is conditioned
by the interlayered iron. The
clay particles, pores and fissures are
equidimensional, and their size is
quite small. Coarser magnifications
show clay particles disposed in such
a way as to create a cellular structure
of smectitic type (Fig. lb) (TESSIER,

-~
A
B
TABLE 1
Physical plus mineralogical (A) and chemical analyses (B) of the B horizons at two sites in the Jura*
Site and soil type Texture% Colour Mineralogy
-- --
Mont Rond Clay fine silt coarse silt fine sand coarse sa~d Kaolinite Smectite Vermiculite S-V
brown leached soil 82.1 12.1 2.5 2.9 0.4 10YR 5/6 5 so 10 25
Maisod 62.4 26.7 7.7 2.8 0.4 SYR 6/8 10 20 15 50
red fersiallitic soil_-
CEC
pH water O.M.% meq/100gr Exch. Ca lions meq/100gr Satur. Fe tot Extr. Fe% AI tot-
Ca Mg Na K % % Di Ox Py %
Mont Rond 5.48 2.2 34.4 32.7 1.1 0.1 0.5 55 6.68 3.2 0.5 0.4 10.22
Maisod 6.72 0.8 23.2 22.1 0.8 0.1 0.5 65 6.44 0.4 0.5 0.2 8.28
* For the complete soil description and other analytical data, see BRESSON, 1974 and 1981
Quartz Goethite
5 5
5 tr
Extr. AI%
Di Ox Py
0.5 0.5 0.2
0.6 0.6 0.3
:;1
(I>
h1
~
~
-Q.,
~
~
~
~
0
;:::
1r
d'
~
~
v.'
" r
VI
8

-2!-LID
d-1 !liD
e-2 !liD f-10!-lrrr

The Effect of Gypsum on the Poral System ... 503
1984). In these hydric conditions,
pores of such size (2-3 Jlm) are reg-·
ularly distributed, and they become
empty, while the aggregates are detached.
In the brown soil the water is
drained off slowly, since it is impounded
because of the small pore
size. The geometry of the system
shows a marked orientation, owing to
the mechanical constraint exercized
(Fig. le). The clay particles are disposed
mainly F-F, they are packed
and the packets are separated by
pores and fissures very different in
size. (Fig. ld). Sometimes, along the
edges of the fissures, «open>> particles
disposed E-F are present: it means
that during the dehydratation process
the system is re-organizing its
geometry.
b) Samples treated with gypsum.
The behaviour of the fersiallitic soil
did not show substantial differences
throughout the treatment (7 to 90
days): the rigid structure typical of
the organization of clay particles
plays a decisive role in cancelling any
possible gypsum effect.
The system geometry as observed
after 15 days of treatment (Fig. le)
displays packets of particles tightly
connected, disposed F-F, and separated
by pores and fissures constantly

--
504 A.B. Delmas, C. Bini, J. Berrier
pendicularly to the fissures themselves,
according a E-F organization,
This kind of organization is particularly
developed on the edge of the
large fissures which surround either
ancient, non-dispersed nodules or
was in contact with the gypsum crystal
shows an organization formed by
large particles separated by elon"
gated, boat-shaped fissures (0 2-3
!-!ID). Along the edges of the fissures,
small-size particles are disposed pera-5!lm
b-5!lm
c-5!lm
d-2!lm
Fig. 2- Brown leached soil. After 15 days treatment: a) At the contact surface, clay particles seem to
open themselves towards a E-F organization. The fissures show a typical boat-shape. b) Far from
the treated surface, particles are packed F-F and separated by empty cavities. After 45 days
treatment: c) At the contact surface, the starting orientation is overcome. The fissures' edges are
enriched with perpendicular particles (size about 1 x 0.2!lm). d) At a distance of 3 cm from the
surface, small empty cavities separate particles disposed F-F, without any re-filling. Note, in the
center, a curious E-F aggregation ().

quartz grains of silt size (Fig. 2a).
As we move away from the treated
surface towards the bottom of the
stick, the system geometry remains
as described previously in the nontreated
samples. Elongated,
fissures separate packets of large
particles which are disposed F-F and
oriented (Fig. 2b).
The above described theme of a reorganization
of clay particles along
the edges of the fissures recurs
throughout the experimental data,
from 30 to 90 days, and it is attributed
to what we call

506 A.B. Delmas, C. Bini, I. Berrier
a-1 ~m b-1 ~m
c-2 ~m d-20 ~m
Fig. 3 - Brown leached soil. After .60 days treatment: a) Beneath 1 cm under the treated surface,
packets of particles are opened and disposed E-F. b) Beneath 3 cm from the SJJ.rface, an F-F
organization is still present. The poral system geometry is mantained. After 90 days treatment:
c) At a distance of 4.5 cm from the surface, clay particles seem to be still F-F packed and separated
by empty cavities. d) A number of small, empty fissures divides a non-dispersed microaggregate.
The clay material's structure before treatment with gypsum is thus recorded.
observe the crystal surface; second,
analyses were made of exchangeable
calcium in the sticks, after having divided
each stick into ten disks 0 40x5
mm.
(i) The SEM observations gave a
number of dissolution features which
differed according to the period of
contact between gypsum and clay.
Such features have not yet been classified,
and they will not be discussed
further in this paper.

The Effect of Gypsum on the Porarsystem ... 507
(ii) Exchangeable Ca2+ distribution
in the clay sticks confirms the SEM
observations. There was indeed Ca 2 +
mobilization in the gypsum-clay system
proportional to the ·. contact
period. Moreover, the mobilization is
in relation to the intensity of the
as examined by
SEM. Calcium distribution curves, in
fact, show (Fig. 4) that throughout
the testing period there is a Ca 2 +
accumulation at the surface, an inflection
zone between 1 and· 3 cm,
and a minimum Ca 2 + content at the
other extremity of the stick. The maximum
Ca 2 + accumulation, of course,.
takes place after a 90 day gypsum dissolution.
We can try to explain kinetically
this trend by the migration of protons
from the surface of the micro-system
to the bottom; this migration, is
caused by a calcium excess, due to
gypsum dissolution (DELMAS, 1979).
Since the system is closed, the trans-
ferred protons move the Ca 2 + from
the bottom to the centre of the stick
by a retro-diffusion process, that
brings the system back to the starting
conditions. The suggested mechanism
must be necessarily accompanied
by a pH variation in acid direction,
from the top to the bottom of the
micro-system, a variation that we
really ascertained.
The pH values, during the experimental
tests, varied from 5.95 at
the top of the stick, to 5.25 at the bottom.
The zone of the stick corresponding
to that of the inflection of
the calcium distribution curves (between
1 and 3 cm) showed pH values
close to that of the starting material,
that is 5.5.
Conclusions
Since the above experimental
study modelizes a natural system
0 cm
10
25 30 35
meq/1 OOgr
Fig. 4- Brown leached soil. Exchangeable calcium distribution curves (meq/100 gr) in clay sticks
as a function of time of gypsum application. Sticks are cutted into disks 50 mm thick (no. 1 to 1 0).
A: Ca 2 + after 15 days. treatment with gypsum; B: Ca 2 + after 30 days treatment with gypsum;
C: Ca 2 + after 45 days treatment with gypsum; D: Ca 2 + after 60 days treatment with gypsum;
E: Ca 2 + after 75 days treatment with gypsum; F: Ca 2 + after 90 days treatment with gypsum.

508 A.B. Delmas, C. Bini, J. Berrier
[rock-clay-pore] as well as what happens
at the interface clay-Ca bearing
mineral, the following pedological
and agronomical conclusions may be
drawn:
1. The «gypsum effect» on a poorly
structured, non-salted clayey material
(brown soil), whose exchange
complex is close to Ca 2 + saturation,
results in a modification of the starting
structural conditions. Clay particles,
which were organized mainly F­
F, tend to detach themselves and to
be oriented B-F in the coarsest pores.
These, indeed, will not be «shut»;
they will remain «open». On the
other hand, the presence Of iron in
the clay structure (red soil) strongly
limits the effect of gypsum, and does
not support appreciable modifications
of the poral system geometry.
2. The role played by the gypsum is
not yet well known. As far as we can
see, it is responsible for a microfissuration
with re-distribution of
,poral spaces in the material, by creating
a system of micropores whose
size is still favorable to the passage of
soil solutions, thus increasing thepermeability.
3. In our opinion, the cation Ca 2 +
cannot be the only factor promoting
structural improvement, as has been
shown in experimental studies carried
out with CaClz · 2H 2 0 solutions
(GUYOT et al., 1984). On this basis,
we suggest that it is the anion S04 2 '
that exercises a specific action on the
clayey material, probably because
of its tetrahedral structure.
4. Gypsum application on clayey
materials in a determined hydric
state (40% H 20) gives positive results
in a relatively short time, but it takes
at least three months. to have a
structural improvement 5 cm under
the surface.
5. An improvement of soils affected
by strong limitations (e.g. acid clay
soils) is thus possible with gypsum
application over periods of average
length - without risks of soils salinization-
as an alternative to other
soil conditioners.
REFERENCES
BRESSON L.M., 1974. La rubefaction recente des sols en climat tempere humide. These Ill cycle, Paris
VI, pp. 185.
BRESSON L.M., 1981. Tournee 15-61 Oct. 1981. Feuille «S. Claude•• de la Carte Pedologique de
France, echelle 1/100.000. III partie. INAPG, Laboratoire de Pedologie, Grignon, Paris. ·
BussrERES P ., GrRou A., CALLOT G., AND RE L., 1982. Dissolution de particules d' amendement calcaire.
Science du Sol 4, 263-273.
CALVET R., 1967. La diffusion dans les systemes argi/e-eau. II Ann. Agron. 18(4), 429-444.
CHISCI G., LORENZI G., PICCOLO L., 1978. Effects of a ferric conditioner on clay soils. Pp. 309-319, in:
Modifications of Soil Structure (W.W. Emerson, R.D. Bond and A.R. Dexter, editors), J. Wiley
& Sons, New York.
DELMAS A.B., 1979. Etude experiment ale du phenomene de dissolution des sels et des silicates. Approche
cinetique. These Doct. Etat. Paris VI/INRA.
GUYOT J., DELMAS A.B., JACQUIN M.; 1984. Amelioration de la structure. de sols non sales, par le gypse.
Trans. Eur. Col!. «Fonctionnement hydrique et comportement des sols», Dijon (in press).

The Effect of Gypsum on the Porat System ... 509
JANOT M.F., 1983. Influence du phosphogypse sur le comportement physique des sols argileu.x. Mem.
D.E.A. Univ. Rennes!INRA (diff. limitee), p. 83.
TESSIER D., BERRIER J., 1979. Utilisation" de la microscopie electronique a balayage dans /'etude des
sols. Observations des sols humides soumis a different pF. Science du Sol 1, 67-82.
TESSIER D., 1984. Etude experimentale de /'organisation des materiau.x argileu.x. These, INRA, Paris.

Abstracts. 511
Clay Mineralogy of the Piedmont Soils, Italy: A Survey
E. ARDUINO, E. BARBERIS, G. PICCONE, M. FRANCHINP, F. AJMONE
MARSAN, V. BOERO
Istituto di Chimica Agraria, Facolta di Agraria, Universita di Torino, Via P. Giuria 15, 10126 Torino, Italia
1 Dipartimento di Scienze della Terra, ur:iversita di Torino, ViaS. Massimo 22, 10123 Torino, Italia
Soil genesis in Piedmont (NW Italy) has been affected by very different
geological, geomorphological and climatic situations. Since some important
features of the soil depend on its < 2 J.Lm fraction, an extensive research on
the clay minerals was carried out with scientific and utility purposes. It is
well known that the quality of the clay minerals is related to the parent rock
and to the climate occurring during pedogenesis; therefore in this study,
which is still in progress, several situations significantly located throughout
the area were considered: plain, high plain, middle slope and top.
The piedmontese plains and high plain consist mainly of fluvial and fluvioglacial
mixed-grained sediments which can be allocated to the interglacial
phases. Most of them are terraced and the evolution of'the clay fraction of
their soils depends chiefly on the climatic conditions and the time. In fact, in
the ·early Middle Pleistocene soils vermiculite and kaolinite are dominant7
owing to an intense pedogenetic evolution, while in the more recent soilssometimes
superimposed on the former- chlorite and illite are abundant.
This situation is well supported by the data concerning the soils developed
along the river Po near Turin 6 : in the more ancient ones (left banck) we find
mainly vermiculite· whereas chlorite is more frequent in the more recent
soils of the right bank."
The correlation between age and quality of the clay minerals was also
observed in the high plain: a recently studied chronosequence near Biella 1 • 2
shows dominant vermiculite + interlayered illite + kaolinite in the ancient
soils while chlorite and illite are abundant in the more recent ones.
Landscape
Location
Lithology
of the
parent
rock (I)
Age (2)
N.
of
samples
First, second and third
predominant clay
minerals (x)
Lenta (VC) L UPH 3 CI-I-V
FSCG EMP 6 Poorly crystallized min. -V
Mottalciata (VC) FSSG EMP 8 V-V/I-K
Vercelli FG UH 19 I-Cl-V
FSSG UP 6 I-Cl-V
Biella (VC) FSSG MP 5 I-1/V-K
FSSG MP 11 V-V/1-K(G)
Plain Balangero (TO) FSCG EMP 3 K-V/interl.-Clllnterl.
and Torrazza (TO) FS. LMP 2 V-I/CI-I
high Poirino (TO) FS' EMP I V-1/V
plain FSS UPH I V-1-1/V
Carmagnola (TO) FSS UPH I V-I-UC!
Rivoli (TO) L UPH 20 I-V-UV
Brandizzo (TO) FSSG MH 9 CI-I-M
Gassino (TO) FGSG UPH 8 V-Cl-I
Testona (TO) L UPH 3 CI-I-VC!
L UPH 2 CI-I-V
Ternavasso (TO) FSSG EMP 7 V-VII-CI

512 Abstracts
Middle Val Sessera (VC) hEM 4 V-VII-I
slope mEM Pre-alpine 6 1-1/V-V/Interl.
(700- p orogenic __ ~2~CLJJ-illire··a:n:d '15iotite 4 vermiGulik as a consequence of a moderate
pedogenesis seem therefore to be likely.
Monte l'Eco lies at the boundary between the alpine crystalline rock and the
apennine shales and argillites so its mineralogy is more complex. In the top
soils 5 the femic minerals of the Cretaceous diabases have given rise, through a
moderate pedogenesis, to abundant chlorite and sometimes also to chloritevermiculite;
the middle slope soils 3 show a similar clay fraction although
in those developed along the argillaceous border, more heterogeneous clay
minerals resulted form more intense weathering and pedogenesis of the finegrained
sediments, viz. montmorillonite, M/Cl, I/Cl and kaolinite.
The following conclusions can be drawn about the clay minerals of the
Piedmontese soils: i) the clay minerals of the plain and high plain depend
mainly on the climate and the time, ii) in the middle slope and top soils they
are largely affected by the parent rock, and iii) since the pedogenesis is
generally moderate, the more frequent clay minerals are chlorite and interlayered
illite except for the buried or exhumed paleosoils.
Arduino E., Ajmone Marsan F., Barberis E., Zanini E., Franchini M., 1986. Clay minerals and Fecixides
distribution as indicators for soil chronosequences: a significant pedologic situation in the
Piedmontese area (Italy). Geoderrna, (in press).
Arduino E., Franchini M., Barberis E, Piccone G., 1977. Studio di un profile di suolo della zona
Baraggiva Piemontese (Comune di Lenta, provincia di Vercelli). Geol. Appl. Idrogeol. 22, 235-50.
Arduino E., Piccone G., 1968. I terreni dei pascoli montani del Piemonte. 11. I pascoli di'mezza
costae i prati pascoli della F.D. di Monte l'Eco (Alessandria). Ann. Fac. Sci. Agr. Univ. Torino 4,
359-374.
1
2
3
4
Arduino E., Piccone G., Manassero P., 1971. I terreni dei pascoli montani del Piemonte. I pascoli
di vetta della F.D. «Val Sessera» (Vercelli). Ann. Fac. Sci. Agr. Univ. Torino 6, 87-102.
5
Cecconi S., Arduino E., 1966. I terreni dei pascoli montani del Piemonte.l. I pascoli di vetta della
F.D. di Monte l'Eco (Alessandria). Ann. Fac. Sci. Agr. Univ. Torino 3, 349-370.
6
Facchinelli A., 1983. Private comunication.
7
Manassero P., Arduino E., Piccone G., 1973. I terreni della Baraggia Vercellese. I. Zona di
Mottalciata. Ann. Fac. Sci. Agr. Univ. Torino 8, 173-194.
8
Piccone G., Manassero P., Arduino E., 1972. I terreni dei pascoli montani del Piemonte. I pascoli
di mezza costa della F.D. «Val Sessera>> (Vercelli). Ann. Fac. Sci. Agr. Univ. Torino 7, 53-68.

Abstracts
513
Micromorphological Features of Clay Translocations in
Mediterranean Red Soils (Rhodoxeralfs-Haploxeralfs)
C. BANOS, M. AYERBE
Centro de Edafologia y Biologia Aplicada del Cuarto, C.S.I.C., Apdo. 1052, 41080 Sevilla, Espaiia
In Soil Micromorphology, a thin-section is representative of a horizon. The
basic descriptive unit is the s-matrix; it consists of the plasma, skeletcm grains
and voids (porosity) ... (Kubiena, 1938; Brewer, 1964).
The arrangement of these basic components and the proportions of plasma,
silt and sand lead to formation of distinct «related distribution patterns».
The plasma- colloidal fraction of the soil- is the most active component of
the soil material and is capable of reorganization, translocation and neoformation.
In Soil Taxonomy (Soil Survey Staff, 1975), soils are classified based on the
activity of the plasma or on the characteristic given to the soil by a specific
behaviour of the plasma (v.gr. in the argillaceous horizon, plasma has accumulated
by translocation).
Although a colloidal size is specified, individual plasma can not be seen with
the petrographic microscope and'even with the scanning electron microscope
a magnification of more than 10,000 is generally necessary. However,
plasma domains are readily discernible (Eswaran & Baflos, 1976).
Skeleton grains comprise a range of minerals which are primary or secondary,
which vary in solubility, which are or may be present in all stages of
transformation and which are present in all size fractions greater thari
colloidal size.
In this paper, micfomorphologica:l features of clay translocation in B, horizons
of mediterranean.,«red soils>> are studied. They are located in the Guadalquivir
River basin (Seville, Spain).
The principal process occurring in this group of soils is probably the illuviation
of fine clay in the argil!aceous horizons B, indicated by the existence of.
ferriargilans (cutans with clay and iron oxides) in conducting channels.
Examination of thin-sections by petrographic microscopy showed the existence
of

514 Abstracts
Clay Minerals in Brown Soils of Cantabria, Spain
M.T. GARCIA-GONZALEZ, M.P. RECIO
Institute de Edafo1ogia y Biologia Vegetal, C.S.I.C., Serrano 115 · dpdo., 28006 Madrid, Espafia
The clay mineralogy of two soil profiles from Puerto de !os Tornos and Puerto
de la Gtanja, respectively, has been investigated. These profiles were shown,
among others, during the XIIth Meeting of the Spanish Soil Science Society
as representative soils of Cantabria.
Both profiles are developed on Cretaceous sandstone under mesic and udic
climatic conditions; their clay fraction is around 30%. They have been classified
as Inceptisol Humaquept. The profile of Puerto de !os Tornos (I) contains,
according to Soil Taxonomy (1975), the following horizons: Au1-Au2-
B/A-Bg1-Bg2-BCg1-BCg2-Cg and R. Their pH's are between 4.9 and 5.2 and
their base saturation is low, specially in the lower horizons. The profile of
Puerto de la Granja (II) can be described as Au1-Au2-Bg-BCg-Cg1-Cg2-Cg3-C
and R, the plj values being between 4.7 and 5.4. Their base saturation is
rather low, although increasing in the horizons Cg3 and C.
The clay fraction of profile I contains dioctahedral mica as the main component.
Its X-ray diffraction pattern shows an asymmetric maximum at about
10 A, with a bulge on the low angle side. After treatment with glycerol, the
symmetry of the 10 A peak increases considerably and no additional peak is
observed at lower Bragg angles. The heated specimens at 110°C (48 hours)
and 300°C (24 hours) show a gradual decrease of the lower angle tail. After
heating at 500°C (24 hours), the peak becomes more symmetrical and ~ifts
to lower theta values (10.3 A). Heller-Kallai & Kalman (1972), when studying
some illitic-Paleozoic sediments from Israel, reported somewhat similar
diffraction effects, which were interpreted in terms of the existence of about
20% of a randomly interstratified illite-smectite. The lack of an additional·
peak (after glycolation) can, however, also be due to a contents of ordered
expandable layers less than about 20% (Rower & Mowatt, 1966). From the
facts reported above and until a more complete analysis is made, we may
only suggest that this mineral is mainly illite, with a small amount of some
expandable species, perhaps randomly interstratified. This illitic material is
found in every horizon of profile I, although in the lowest one (C) it seems to
be much more organized, as it occurs in the clay fraction of the parent
material. Goethite and lepidocrocite are also found in this profile as minor
components. The clay fraction of the parent material contains high
proportions of goethite.
Illite is also found in profile II as the main component, although less
degraded than in I. Its alteration increases in the upper horizons. Kaolinite
minerals are also found in this profile, their proportion decreasing in the
deepest horizons. Illite and kaolinite minerals are also detected in the parent
material.
The clay mineralogy of these profiles is the common one for strongly weathered
acid soils, which show hydromorphic properties, being developed in
areas with high rainfall and updulating topography.
Heller-Kallai L., Kalman Z.H., 1972. Some naturally occurring illite-smectite interstratifications.
Clays Clay Miner. 20, 165-168.
Rower J., Mowatt T.C., 1966. The mineralogy of illites and mixed-layer illite/montmorillonites.
Am. Miner. 51, 825-854.
Soil Taxonomy, 1975. A basic system of soil classification .for making and interpreting soil surveys.
Soil Survey Staff, Washington.

Abstracts
515
Zeta Potential as a Tool for Investigating the
Dispersion-Flocculation Processes of Clay Soils
G. GIOVANNINI, M. GIACHETTI, S. LUCCHESI
lstituto per la Chimica del Terreno, C.N.R., Via Corridoni 78, 56100 Pisa, Italia
Many clay soils of the Mediterranean area present very poo:r physical characteristics.
Clay material in the presence of water, (rain or irrigation) may
become higly dispersed whereas soil used for agricultural purposes must be
kept in a flocculated state in order that it be porous. Clay dispersion .may
lead to particle rearragement by way of detachment and migration and may
partly fill or plug the pores and channels in the soil and thus reduce soil
permeability with the relevant effects, for instance, on correct irrigation
practice and on.soil erodibility.
The flocculation of clay suspensions is determined by the characteristics of
the double layer which surrounds the particles and extends into the bulk as
described in the well known Gouy-Chapman colloidal model. In this model
certain potentials may be identified: the potential existing between the shear
plane and the bulk phase, called Zeta potential, is of special importance
since it can be measured.
The Zeta potential may be used as an useful indicator of the electrical state of
.the double layer and may supply information on the dispersion-flocculation
processes of the clays. Many papers dealing with the Zeta potential of pure
colloids and clay minerals are reported, whereas there are few in the field of
clay soils; but the findings on the flocculability of the clay minerals cannot
be translated literally to the clay soil because in soil the clay fraction is
interconnected with other mineral fractions, with the organic matter and
with electrolytes. ',
We are therefore forced to measure the Zeta potential on the whole clay soil
or on its fractions: sand, silt, cl~y and on very concentrated suspensions, the
more similar to that present in field conditions.
For this goal we have chosen the apparatus based on the electrophoretic
mass-transport analyzer reported by Oliver & Sennet (1965), and described
as suitable for Jtleasurements on concentrated suspensions. The paper
reports our early results on the reliability of the instrument for clay soil
material as well as on the choice of the best measurement conditions.
Adamson A.W., 1967. Physical Chemistry of Surfaces. Interscience Publishers, New York.
Oliver J.P., Sennet P., 1965. Electrokinetics effect in kaolin-water systems: the measurement of
electrophoretic mobility. 5th Conf. Clay Minerals, Pittsburgh.
Sennet P., Oliver J.P., 1965. Colloidal dispersion, Electrokinetic effeCts and the concept of Zeta
Potential. Ind. Eng. Chem. 57, 32-50.
Van Olphen H., 1977. An Introduction to Clay Colloid Chemistry. J. Wiley & Sons, New York.

516 Abstracts
Clay Mineralogy of Organic Soils from the
«Cordillera Central», -Spain----- --- ------~
M.J. SANCHEZ-MARTIN, M.A. VICENTE, M. SANCHEZ-CAMAZANO
Centro de Edafologia y Biologia Aplicada, C.S.I.C., Cordel de Merinas 40-52, Apdo. 257, 37008 Salamanca, Espafla
This stucfy forms part of a detailed project on the mineralogy and genesis of
clays from soils from the «Cordillera Central» (Luffiego et al., 1976; Sanchez­
Camazano & Vicente, 1979; Vicente & Sanchez-Camazano, 1981; Vicente et
al., 1984). Five profiles, characterized by water logged conditions during a
large part of the year, of the situated at altitudes ranging
from 1500-1780 m, were studied.
The classification and other details of these profiles, located in the Province
of Avila, have already been reported by Luffiego et al. (1976).
----·~ ------------------.
Profile Location Geology Soil type
I Hoyos del Collado Granite Histosol
II Hoyos del Collado Granite Gleyic Cambisol
III La Herguijuela Schists - Histosol
IV Santiago del Collado Granite Histosol
V Navacepeda de Tonnes Granite Humic Cambisol
The techniques adopted were X-ray diffraction and thermic analysis. In
addition, cation exchange capacity also was determined. The clay fractions
of different horizons were extracted, subdivided into two series and treated
in the following manner. The first series of samples was saturated with .
magnesium and the X-ray diffractograms of these Sample were obtained.
Following this, all the samples were either treated with glycerol or subjected
to a temperature of 500°C and their X-ray diffractograms obtained. The
second series of samples was first treated with sodium citrate to liberate free
oxides and subsequently saturated with either magnesium or potassium.
X-ray diffractograms of these samples were obtained in addition to those of
K-saturated samples to temperatures of 110°C and 300°C.
The clay fraction of profiles II and V is composed of kaolinite, illite, gibbsite
and a vermiculite-chlorite intergrade, part of which is interstratified with
illite. Profile II also contains chlorite. The potassium test indicated that a
part of the intergrade behaved like vermiculite. The transformation of illite
and chlorite to intergrades is more pronounced in deeper horizons characterized
by high humidity. In the active organic matter rich profile II the most
predominant process is the destruction of 2/1 layer silicates and increase.of
kaolinite and gibbsite contents, while fn profile V the process of evolution of
illite ~intergrade predominates.
Profiles I, III and IV are very rich in organic matter("' 33%). Profiles I and IV
with polycyclic evolution have a similar mineralogical composition in their
clay fraction, which contains illite, kaolinite, chlorite, gibbsite and interc
grade. The kaolinite rich G horizon is the most characteristic feature· of
these profiles.
Profile III is almost similar to I and IV. The kaolinite and chlorite contents
are lower and constant throughout the profile. The deeper horizons exhibit a
strong illite ~ intergrade transformation.
The nature of organic matter and degree of humidity are the major factors
determining the evolution of these soils. The higher constant humidity of the
deeper horizons favours a high degree of evolution or destruction of 2/1 layer
silicates and an increase in the quantity of kaolinite and gibbsite.

Abstracts 517
Luffiego M., Garcia Rodriguez A., Gallardo J .F., 1976. Contribuci6n a] estudio de Ios suelos histicos
y gleis de la vertiente norte de la Sierra de Gredos.An. Cent. Edafol. Biol. Apl. Salamanca 3, 155-
177.
Sanchez-Carnazano M., Vicente M.A., 1979. Mineralogia de arcillas de sue Ios forestales del Centro­
Oeste de Espafta. I. Sierra de Gata. An. Cent. Edafol. Biol. Apl. Salamanca 5, 231-242.
Vicente M.A., Sanchez-Carnazano M., 1981. Mineralogenesis de arcillas de suelos forestales del
Centro-Oeste de Espafia. II. Sierra de Francia. An. Edaf Agrobiol. 40, 367-380.
Vicente M.A., Sanchez-Carnazano M., Sanchez-Martin M.J ., 1984. Mineralogia de arcillas de suelos
glei y de cesped alpino de la Cordillera Central (in press).

Section V
Ceramic Clays

Miner. Petrogr. Acta
Vol. 29-A, pp. 521-533 (1985)
Drying Properties of Ceramic Clays
from Granada Province, Spain
E. BARAHONA 1 , F. HUERTASI, A. POZZUOLP, J. LINARES 1
1 Estaci6n Experimental del Zaidin, C.Sl.C., Profesor Albareda 1, 18008 Granada, Espaiia
2 Dipartimento di Geofisica e Vulcanologia de\l'Universitit di Napoli, LargoS. Marcellino 10,80138 Napoli, Italia
ABSTRACT - A critical study is made of the different for!Tls of e;>epressing
drying shrinkage, and it is concluded that the best index is the volume
shrinkage expressed as percentage of fin

522 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
since it often leads to piece failures
due to excessive or unequal shrinkage
of molded pieces. The first stage ~of
water loss is equal in weight to the
volume contraction. This «shrinkage
water» is that held by clay particles
due to colloidal mechanisms.

Drying Properties of Ceramic Clays ... 523
TABLE 1
Drying properties of the samples
Sample H Ac Ap DA p cvs CLS Ks
Ac-ll 30.9 14.8 16.1 1.87 30.1 27.7 8.5 .92
Ab-ll 33.6 13.8 19.8 1.69 33.4 23.3 7.2 .70
Ah-11 27.5 12.1 15.4 1.89 29.1 22.9 7.1 .79
Ah-21 27.2 ll.S 15.7 1.88 29.5 21.6 6.7 .73
Ah-31 34.4 13.2 21.2 1.70 36.0 22.4 7.0 .63
Ah-32 30.4 12.1 18.3 1.79 32.8 21.7 6.8 .66
Ah-33 35.6 11.6 14.0 1.69 27.4 22.7 7.1 .83
Ah-41 31.5 13.1 18.4 1.81 33.3 23.7 7.3 .71
Ah-42 40.1 18.4 21.7 1.71 37.1 31.5 9.6 .85
Ah-51 27.9 12.8 15.1 1.88 28.4 24.1 7.5 .85
Ah-52 31.9 13.8 18.1 1.75 31.7 24.2 7.5 .76
J-11 33.7 17.6 16.1 1.84 29.6 32.4 9.8 1.09
J-12 30.2 15.0 15.2 1.90 29.8 28.5 8.7 .99
J-21 31.6 12.3 19.3 1.79 34.7 22.0 6.8 .64
J-31 33.0 17.3 15.7 1.88 29.5 32.5 9.8 1.10
J-41 33.7 17.3 16.4 1.88 30.8 32.5 9.8 1.05
J-51 29.8 15.2 14.6 1.90 27.7 28.9 8.8 1.04
J-52 33.6 18.6 15.0 1.92 28.8 35.7 10.7 1.24
J-53 34.0 17.6 16.4 1.86 30.5 32.7 9.9 1.07
J-54 33.9 17.0 16.9 1.89 32.0 32.1 9.4 1.01
J-55 32.5 6.7 25.8 1.60 41.3 10.7 3.4 .26
Mn-ll 31.0 16.3 14.7 1.88 27.6 30.6 9.3 1.11 .
Mn-21 33.7 15.5 18.2 1.80 32.8 27.9 8.6 .85
Pi-ll 39.0 18.0 21.0 1.70 35.7 30.6 9.3 .86
Pi-12 38.5 18.7 19.8 1.73 34.2 32.3 9.8 .94
Pi-13 34.3 16.4 17.9 1.81 32.4 29.7 9.1 .92
Ch-11 31.0 16.8 14.2 1.90 27.0 31.9 9.7 1.18
Ch-12 31.2 17.2 1'4.0 1.84 25.8 31.6 9.6 1.23
Ga-ll 26.6 12.1 14.5 1.93 28.0 23.4 7.3 .83
Ga-21 29.8 14.3 15.5 1.88 29.1 26.9 8.3 .92
Ma-ll 34.0 17.8 16.2 1.84 29.8 32.8 9~9 1.10
Ma-12 30.9 17.3 13.6 1.96 26.6 33.9 10.2 1.27
Ma-13 26.2 13.8 12.4 1.99 24.7 27.5 8.4 1.11
Ma-14 23.2 11.0 12.2 2.00 24.2 22.0 6.8 .90
Pc-ll 37.4 23.2 14.2 1.91 27.1 44.3 13.0 1.63
Vi-ll 26.9 13.8 13.1 1.92 25.2 26.5 8.2 1.05
B-ll 49.9 35.1 14.8 1.88 27.8 66.0 18.4 2.37
B-12 47.6 32.3 15.3 1.90 29.1 61.4 17.3 2.ll
B-13 37.7 22.2 15.5 1.90 29.4 42.2 12.4 1.43
B-14 38.4 24.6 13.8 1.85 25.5 45.5 13.3 1.78
B-21 30.5 14.8 15.7 1.89 29.7 28.0 8.8 .94
D-ll 36.0 15.0 21.0 1.70 35.7 25.5 7.7 .71
G-ll 32.7 16.7 16.0 1.86 29.8 31.6 9.6 1.04
Mo-ll 22.1 11.5 10.6 2.12 22.4 24.4 7.5 1.08
Mo-21 19.0 7.0 12.0 2.10 25.0 14.7 4.7 .58
Mo-22 '29.1 9.0 20.1 1.74 35.0 15.7 5.0 .44
Mo-31 34.2 11.7 22.5 1.68 37.8 19.7 6.2 .52
Mo-41 29.8 11.1 18.7 1.74 32.6 19.3 6.1 .59
Ac: Acequias; Ab: Albuftuelas; Ah: Alhendir:t; J: Jun; Mn: Monachil; Pi: Pinos Genil;
Ch: Chauchina: Ga: Gabia; Ma: Caracena; Pc:' Pantano de Cubillas; Vi: Viznar; B: Baza;
D: Diezma; G: Guadix; Mo: Motril
tionship may be considered as linear
and this method was also selected,
for it is often used by manufacturers.
Experimental methods
Samples were crushed and sieved

524 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
to 2 mm and water was added until a
consistency corresponding to Rieke' s
sticky point was reached. After
kneading, test pieces approximately
cylindrical in shape with a volume of
about 20 cm 3 were molded by hand
and allowed to dry at room temperature
and, then, in an oven at 105 °C.
Moist and dry weights (Ph and Ps)
were recorded. Moist and dry
volumes (Vh and Vs) were measured
by mercury displacement. From
these values, the following characteristic
values were calculated:
Volume shrinkage, CVS = (Vh-Vs)
lOONs;
Linear shrinkage, CLS was de­
- ·---

Drying Properties of Ceramic Czqys ... 525
60
60
50 50
40 .. 40 ..
'» ·>.
u
u

526 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
15 ..
~-----·-·--·-~---- -------w
Fig. 5 - Drying shrinkage (CLS) lines. Samples
from Jun.
din (Ah-42), Jun (J-55), Pinos (Pi-11),
Diezma (D-11) and Motril (Mo-22 and
20 ...
Cl
-"'

Drying Properties of Ceraniic-Cl~ys ... 527
the drying curve shows that this is
not the case. As a matter offact, since
volume shrinkage is CVS = VNs and
shrinkage water is Ac = V/Ps, where
V is the volume change, the slope is
given by CVS/Ac or PsNs, namely,
the bulk density of dry bodies. Thus,
differences in bulk density among
samples give rise to the fact that the
same water removed on a volume
basis is. manifested by different figures
when expressed on a weight
basis, which is undoubtedly unrelated
to the ease of drying.
On the other hand, where Vh is the
specimen moist volume, Vs the dry
volume, Vo the volume of the solid
phase, Va the volume of tempering
water and Vp the volume of pores, we
have that:
Vh = Va·Vo and
Vs = Vp•Vo, so that
Vh-Vs = Va-Vp
Therefore, CVS = (Vh-Vs)Ns could
be also expressed as CVS = (Va-Vp)/
Vs or CVS = VaNs-VpNs.
Taking into account that the bulk
density is D = PsNs and that porosity
is P = VpNs the expression for
volume shrinkage can be written as:
. CVS = H · D-P
where D is the bulk density, H the
tempering water and P the porosity.
This is the equation of a straight line
whose slope is the bulk density and
the origin intercept, the porosity of
dried specimens. Assuming a value of
2.65 for the true particle density, this
equation reduces to:
CVS = D(H + 37.7)-100
80 Vl
>
u
60
a;
Cl
-"'
s:::
s....
.

528 E. Barahona, F. Huertas, A. Pozzuo/i, J. Linares
Thus we can describe shrinkage as
a function of moisture content, by
only knowing the dry bulk density.
This. is illustrated in Fig. 7 where
shrinkage values estimated using the
above equation are plotted against
the experimental values. Note the
very low error of the estimated
shrinkage values.
The shrinkage curves obtained by
using the values of pore water and
linear shrinkage, do not clearly de-
. \
scribe some phenomena, such as the
secondary shrinkage that occurs durl.ng
pore water removal. Actually, a
~harp critical point where shrinkage
, ceases .. does not exist. However, the
curves so obtained are satisfactory,
__________ as.can-be seen- -i-n-Fig~- 8- where the
shrinkage curves were constructed by
multiple recording of volumes and
weights during the drying process.
The values of calculated pore water
and those obtained by extrapolation
of these curves ary coincident (see top
10 Mo 11 Ga11 Ah32 Ah31 J55
of Fig. 8). On the other hand, the existence
of a, secondary sJ:l:r::~J:lJ

Drying Properties of Ceramic Ctays ...
529
20
(/)
--'
(.)
•
~
QJ
Ol
15 -"'
c
·s::
.s=
(/)
,_
10
QJ
"' c
--'
... . . ... ...
• ..
/ ••
.. . .
•
••••
••• •
• •
5
y = 2.398 + 0.220x
r = 0.844
"
Cl ay %
20 40 50
Fig. 9 - Linear shrinkage (CLS) versus clay content.
80
summarized in Table 3. Most of the
shrinkage variance (50%) is
accounted for by the illite content.
Both illite and smectite show a positive
unitary contribution, while paragonite,
chlorite and kaolinite tend to
diminish shrinkage_.and show negative
signs for the regression coefficients.
The prediction of linear
. shrinkage through smectite and illite
content is better than that obtained
by simple linear regression against
TABLE 3
Correlations and multiple linear regression equations. Relationships between linear
shrinkage and clay minerals contents
CLS = 3.506+0.195 Smectite +0.230 Illite
R=0.905 Degree of freedom: 45 Standard error: 1.18
CLS,;, 10.740- 1.056 Paragonite- 0.386 Chlorite- 0.061 Kaolinite
R = 0.432 Degree of freedom: 44 Standard error: 2.52
Clay minerals are expressed as percentages of the whole sample

530 E. Barahona, F. Huertas, A. Pozzuoli, J. Li1-;ares
clay content (multiple regression
coefficient R = 0.905).
It is worth stressing that the best
single predictor for drying shrinkage
is the hygroscopicity of raw materials,
as determined according to the
method outlined by KEELING (1966)
(Fig. 10). The correlation coefficient
(0.94) is significantly higher than any
considered above. This determination
is very simple, but takes into
account both the amount and quality
of the clay fraction, for it is a rough
measure of the specific surface, and
its use is strongly recommended for
routine work.
20
On the other hand,_porosity and the
relatecl ~~9,riabl_e,s.,.~J2C!t::_e~ ~ater ancl
bulk density, are dependent on grain
size distribution, since the packing of
solid particles is increased as heterometry
increases. The most used measures
of -grain size heterometry are:
the semiinterquartile range (0 3 -QI)/2
(Krumbein's Qd __,
u
...
15
QJ
C">
"""

Drying Properties of Ceramic Clays ... 531
TABLE 4
Correlations and simple linear regression equations. Pore water, porosity and bulk density
versus heterometry indexes
y X r Regression equation
Pore water-Qdcp
Pore water-He
Pore water-P10-P9o
Porosity-Qdcp
Porosity-He
Porosity-P10-P9o
Bulk density-Qdcp
Bulk density-He
Bulk densi-ty-P10-P9o
r= -0.727
r= -0.621
r= -0.664
r= -0.706
r= -0.655
r= -0.633
r= +0.813
r= +0.741
r= +0.750
y=25.11-4.18x
y= 23.32-3.88x
y=24.72-1.08x
y=40.94-5.20x
y= 38.79-4.86x
y= 40.31-1.32x
y= 1.52+0.16x
y= 1.59+0.15x
y= 1.53+0.04x
MANN (1956) was used without conclusive
results. Thus, the drying behaviour
of materials in commercial
practice at some type localities was
used to judge the drying sensitivity,
taking into account both drying conditions
and size of the manufactured
pieces.
At Motril, drying is performed by
direct exposition to sun, without
further precautions. Pieces are
molded by hand, because of lack of
plasticity, and these materials can be
considered as non sensitive. Nosova's
index ranges from 0.43 to 0.75 with a
mean value of 0.55.
This is also the case for Alhendin,
but here hollow bricks are manufac-
tured by vacuum extrusion. Drying
sensitivity is considered to be low. Ks
ranges from 0.58 to 0.87, with a mean
with heterometry, while the opposite
is true for the bulk density. The best
predictor is, in all cases, Krumbein's
Qd

532 E. Barahona, F. Huertas, A. Pozzuoli, J. Lin_ares
Nosova's index
Excessive
-• ~---~ ~~DY'yirig.:..- ~- -~~~
Sensitivity
L_ ____ o_._7 ______ ~o._s _____________ 1~.4--------,:>
Clay ~b
116 17. 21 24 25 26 43 >
L...--..,.,-t -l--I--;l.---.1 ___ _
Hygroscopicity % ,1.3 1.5 2 2.4 2.5 2.7 4.8 "'
L..,-t ----,fr-. --~tr-:tr-----v'
Plasticity
Barnas's index
Plasticity
Rieke's index
~---o._4 _____________ o_.4_5-r------------------->·
t
__;___>
L__l7 ___ 9 _
Pl asti city
- ··-too -low for·
small pieces
Plasticity
too low fo-r
big pieces
~ ·- -
Fig. 11 -Guide-numbers for evaluating raw materials. Clay and hygroscopicity values were derived
from regressions against plasticity and sensitivity indexes.
sidered to be moderate. Ks ranges
from 0.75 to 1.25, with a mean value
of 1.06.
The materials from Baza are a
clear example of high drying sensitivity.
The driers used are closed chambers,
without an internal heat source,
so as to slow down the drying speed,
and large sized pieces . are not currently
manufactured because of their
rate of drying failure. Here Ks ranges
from 1.28 to 2.37, with a mean value
of 1.88. Such is.the case, also, for a
sample of Pantano de CU:billas. This
material was used by several manufacturers
of J un and Maracena and
abandoned because of multiple
drying failures (Ks = 1.83).
Ifwe take the mean values between
type localities as guide-numbers, the
classes obtained are very similar to
those given by BUDNIKOV (1964).
Figure 11 summarizes the guidenumbers
obtained for drying sensi- •
tivity, plasticity indexes and the corresponding
clay and hygroscopicity
values. Clays low in drying sensitivity
are also low in plasticity, which
becomes a limiting factor. Such critical
values are to be taken only as a
rule of thumb and should be revised
if better installations for molding and
drying are introduced in working
practice.

Drying Properties of Ceramic Clays ... 533
REFERENCES
BARAHONA E., HUERTAS F., POZZUOLI A., LINARES J., 1982. Mineralogia e genesi dei sedimenti della
provincia di Granada (Spagna). Miner. Petrogr. Acta 26, 61-99.
BARAHONA E., HUERTAS F., Pozzuou A., LINARES J ., 1983. Sulla plasticita dei sedimenti della provincia
di Granada (Spagna). Miner. Petrogr. Acta 27, 161-182.
BuDNIKOV P.P., 1964. The Technology of Ceramics and Refractories. Edward Arnold, London.
FoRD R.W., 1964. Drying. Mac Laren & Sons, London.
KEELING P.S., 1966. !LIMA. A practical metho4 of assessing pottery clays. 'Irans. Br. Ceram.Soc. 65,
463-477.
KRiscHER 0., KROLL K., 1956. Trocknungstechnik, Band 2: Trockner und Trocknungsverfahren.
Springer-Verlag, Berlin.
LIPPMANN F., 1956. Uber einen einfachen Test zur Erkennung der Trockenempfindlichkeit van Tonen.
Ber. dt. keram. Ges. 33, 150-153.
NORTON F.H., 1949. Refractories. Mac Graw-Hill, New York.
STONE R.L., 1957. Determinative Tests of Aid in the Design of Driers and Kilns.Bull. Am. Ceram. Soc.
36, 1-5.

Miner. Petrogr. Acta
Vol. 29-A, pp. 535-545 (1985)
Clays and Complementary Raw Materials
for Stoneware Tiles
B. FABBRI, C. FIORI
Istituto di Ricerche Tecnologiche per la Ceramica, C.N.R., Via Granarolo 6, 48018 Faenza, Italia
ABSTRACT- The chemical-mineralogical characteristics of the main types of
clay used in the production of Italian stoneware tile are described. On the
basis of average chemical and mineralogical compositions of bodies used on
an industrial scale, criteria are given to develop optimal mixes with the described
clays and complementary quartz-feldspar raw materials in order to
obtain stoneware tiles of good qualitY: The objective is that of contributing
to a better knowledge of the compositional characteristics of the clay used
for ceramic products as well as that of developing simple and reliable
methods for the preliminary verification of the suitability of a clay material
for use by the ceramic industry, even though the data about the clay material
has been obtained for a different purpose.
Introduction
Clays are the basic raw mq.terials
for many traditional ceramic products.Asanexampleoftheirapplication
in _the manufacture of ceramics, we
chose the use of clay materials in the
production of stoneware tiles by the
modern rapid single-firing technique.
Theseproductsrepresentagood
quality goal of the Italian Ceramic
Industry, because of their high mechanical
strength and frost resist-\
ance, and their aesthetic characteristics,
which allow their use for pavements
and walls both indoors and
outdoors.
In keeping to the specific subject
of this Conference, the present paper
deals with clays and complementary
raw materials used "in the manufacture
of vitrified stoneware tile bodies,
and the materials used for glazed will
not be taken in to consideration. Stoneware
tiles are essentially of two
types: «red gres» and «white gres».
The white gres actually is_ gray in
most cases, while the red gres can be
brown, dark-brown, dark-purple and
so on. Nowaday, coloured stoneware
tiles are obtained by using ceramic
pigments in the white gres body compositions.
Going back to the two fundamental
bodies for stoneware tiles, it should
be pointed out that their colouring
depends mainly on the clay utilized:
- for the «red gres >>, illi tic-chlori tic

B. Fabbri, C. Fiori
clays with an iron content of 6-8%
Fe 2 0 3 are used;
- for the «white gres>> illitic-kaolinitic
clays with an Fe 2 0 3 content
less than 1.5% are used.
The complementary raw materials
used as stoneware body components,
together with the. above said clays,
can be divided into two main categories:
feldspars and sands.
With regard to feldspars, it should
be pointed out that rather than using
pure feldspars, the ceramic industry
frequently uses feldspar-rich rocks,·
because of their lower cost and their
quartz content; otherwise quartz
must be added separately to the bodies.
-- - -----~.. pso mchidea a-mon~( ille-feldspars
are feldspathoid-rich rocks used as
«fluxes>> and well-known as nepheline-syenites.
Among the sands, quartz-feldspar
types are more frequently' used than
high purity quartz sands.
The illitic-chloritic clays for the
typical Italian stoneware tiles come
from the «argille varicolori>> or
behaviour; they develop a
remarkable amount of vitreous phase
during firing, without the necessity
of adding fluxes to the starting bodies.
The clay fraction of these materials
is characterized by the illi techlorite
association, while kaolinite
and montmorillonite often are present,
but, generally, in smaller and
fairly variable amounts. This kind of
clay also contains relatively high
amounts .QLQ)(i.,
with variable characteristics,
available for importation to
Italy from the above said countries. In
fact, even if the main mineralogical
components are always the same
(illite, kaolinite, quartz), they range
from materials with a high quartz
content and relatively poor- illitekaolinite
fraction, which in the ceramic
industry are usually referred to
as kaolinitic sands, to real kaolins
whose main constituent is kaolinite.
AI1f.ong the accessory minerals, potash
feldspar is very frequentlY: present.
Chemical characteristics represented
by means of ternary diagrams
There is a remarkable mass of data
regarding the chemical composition

Clays and Complementary Raw)J:c!terials ... 537
Fe 2 o 3 + Ti o 2 +
MgO + CaO +
Na 2
0 t KzO
Fe 2 o 3 + Ti o 2 +
MgO + CaO
SiOz Alz0 3
Na 2 0+K 2 0 ~lgO+CaO
Fig. 1 - The three ternary diagrams used to represent the variability limits of the chemical
composition of clays and complementary raw materials for the production of stoneware tiles.
rameters relative to the four groups
of raw materials. This objective was
attained using ternary diagrams, already
applied in previous studies,
and shown schematically in Fig. 1. At
the vertices we have respectively: on
the first diagram: silica, alumina and
the sum of the other oxides; on the
second (which excludes silica): alumina,
alkali oxides and the sum of the
of the four fundamental groups of
raw materials. They are available in
the literature or in catalogues published
by the suppliers of raw materials.
Irt general, the mineralogical
compositions of the materials are
known only qualitatively. Our study,
essentially statistical in nature, had
the aim of defining the limit~ of variability
of the principal chemica:I paa)
il ritic- chloritic clays
b) illitic- kaolinitic materials
b 1 )
b")
b 11 • 1 )
german
engl ish
french
Fig. 2- Compositional fields of clays for red and «white>> stoneware tiles in the ternary diagram
Si0 2 /Alz03/(Ti0z + Fez03 + MgO + CaO + Nazb +KzO).

538 B. Fabbri, C. Fiori
remammg oxides; on the third
(which excludes both alumina and
silica): alkali oxides, alkaline-earth
oxides and iron oxide plus titanium
oxide. A further objective of our work
was that of describing the contribution
of the individual raw materials
to the chemical and mineralogical
composition of typical bodies for
stoneware tile.
The first diagram, silica/alumina/
other oxides (Fig. 2), takes into account,
practically, the whole chemical
analysis (with the exception of the
ignition loss) and so it is the most
significant and the most suitable diagram
for the determination of typical
··-~~---- __ co~e~~tion fields ~or th~ va!i~l:l~
types of raw materials and ceramic
mixes or for their classification on
the basis of their chemical composition.
On this diagram the composition
fields of the illitic-chloritic clays
(hatched area) and the illitic-kaolinitic
materials, separated on the basis
of the country of origin (white areas),
have been delineated. This was done
by taking into consideration 38 chemical
analyses of illitic-chloritic clays
available in the literaturec(EMILIANI
& VICENZINI 1974; PALMONARI et
al., 1974; BIFFI, 1976; LOSCHI.
GHITTONI & MINOPULOS, 1976;
LOSCHI GHITTONI, 1977; VICEN­
ZINI & FIORI, 1977; BIFFI et al.,
1979; FABBRI & FIORI, 1981), 57
analyses of German, 40 of English,
and 30 of French kaolinitic raw materials,
partly declared by the suppliers,
and partly from results obtained
at our Institute. Each material
has been r~presented on the diagram
by one point and the boundary of the
fields has bee_n_

Clays and Complementary Raw Matenals ...
539
60%
a) illitic-chioritic clays
b) illitic- kaolinitic materials
b' ) german
b") engl ish
b"') french
~~----~------~------~------~~----~~--~~60%
Na 20+K20
Fig. 3 - Compositional fields of clays for red and stoneware tiles in the ternary diagram
Alz03/(NazO + K 2 0)/(Ti0 2 + Fe 203 + MgO + CaO).
MgO+CaO
a) illitic- chloritic clays
b) illitic- kaolinitic materials
b' )
b")
b 111 )
german
english
french
K 2
o
Fig. 4- Compositional fields of clays for red and «white>> stoneware tiles in the ternary diagram
(NazO + K 2 0)/(Ti0z + Fez03)/(MgO + CaO).
Fez03

540 B. Fabbri, C. Fiori
ides, and the field of illitic-kaolinitic
materials. However there is a discrete
amount of differentiation within the
illitic-kaolinitic field itself. In fact,
the field of French materials is located
close to the alumina-remaining
oxides side, showing an extreme
scarceness of alkali oxides.
Analogous consideration can be
made in regard to the third diagram
Na 2 0 + K 2 0/Fe 2 0 3 + TiOz/MgO +
CaO (Fig. 4) where the field of the
French materials is clearly separate
from the fields of the English and
German materials, which are practically
superimposed one on the other.
The sal:ne ternary diagrams seen
for the clay materials have been util-
~-~~~--·~---·---~1ze-d~t

Clays and Complementary Raw-Materials ... 541
and shifted in comparison with;them
towards the silica vertex. It can be
said that there is no solution of conti-·
nuity between the areas of the diagram
occupied by the feldspars and
feldspathic rocks and by the quartzfeldspar
sands. The quartz sands,
composed almost exclusively of
quartz, and the nepheline-syenites,
silica unsatured rocks, occupy positions
distinctly separate from those
of the other complementary raw materials.
The other two ternary diagrams
relative to the complementary
raw materials were drawn, but are
not reported here since they have
little significance.
Theoretical formulation of bodies for
stoneware tile
Vitrifiable bodies for tile produc­
"-
tion are mixes of the raw ~aterials
we have discussed here. Reported together
on the ternary diagram silicaJalumina/sum
of the other oxides
are (i) the composition fields of the
four fundamental raw materials, and
(ii) the typical fields of the body compositions
used industrially for the
production of

542 B. Fabbri, C. Fiori
nary diagram just illustrated was
used for this purpose. The first example
(Fig. 7) is for the formulation of a
mix for red gres, composed by only
two materials: illitic-chloritic clay
(85%) and quartz-feldspar sand
(15%). The relative amounts of the
two materials were chosen so that
the representative point of the mix
falls inside the field of the industrial
compositions of red gres. Of course
the representative point of the mix
lays on the line that joins the points
of the two raw materials at distances
from them inversally proportional to
the amounts of these raw materials
in the mix. Because of the relatively
small amount of sand, the minera-
. - - --···-·-·-------logical-composition of the mix does
not differ very much from that of the
clay. Thi,:;.is~~i~-~g£t:~Q!>) to them serves mainly to
modify the)particle size distribution
of the clay.
,The following body composition
for potassic white gres was formulated:
55% illitic-kaolinitic clay, 15%
potassic feldspar and 30% quartzfeldspar
sand (Fig. 8). In this case, the
·representative point of the mix falls
within the triangle having as vertices
the representative points of the three
raw materials used, the relative a­
mounts of which were calculated in
such a way that the point of the mix
50%
Fe2D3+ Ti D2+MgO+
+Ca0+Na 2 0+K20
A
body
quartz 20 55 25
K- feldspar 18
Body for red gres:
85% A
15% s
Na- feldspar 12 15 13
kaolinite
ill ite +muse. 34 30
chlorite 12 10
dolomite
hematite
accessories
Fig. 7- Formulation of a mix for red gres with only two raw materials: an illitic-chloritic clay and a
quartz-feldspar sand.

Clays and Complementary Raw Materials ...
543
50%
Fe 2 o 3 + Ti 0 2 +Mg0+
+Ca0+Na 2 0+K 2 0
FP
body
quartz
25
55
31
K- feldspar
72
18
18
Na- feldspar
19
15
kaol inite
20
11
illite+musc.
accessories
50
30
100%~--------~--------~--~----~--------~--------~50%
A1 2 o 3
Fig. 8 - Formulation of a body for potassic white gres with only three raw materials: an illitickaolinitic
clay, a potassic feldspar and a quartz-feldspar sand.
s'o "
Fe 2
o 3
+ Ti0 2
+Mg0+ '
+CaO+Na 2 0+K 2 0
FS
body
quartz 23
K- feldspar
Na- feldspar
kaolinite 40
illite+musc. 30
accessories
55 25
18
92 15 27
22
18
11
Sodic white 11 gres:
Si0 2
Fig. 9 - Formulatfon of a body for sodic white gres with only three raw materials: an illitickaolinitic
clay, a sodic feldspar and a quartz-feldspar .sand.

544 B. Fabbri, C. Fiori
also falls inside the composition field
of the potassic white gres. Reported
in the table alongside of ~he diagram,
are the mineralogical compositions
of the three raw materials and of the
mix. It can be seen easily from these
data that the clay makes the greatest
contribution to the clay minerals
content of the mix, while, for the
most part, the feldspar rock and to a
lesser extent the quartz-feldspar sand
contribute to the feldspar content of
the mix. The clay and the sand contribute
in fairly equal measures to .
the quartz content of the mix.
Finally, an example is given of a
mix formulation for a sodic white
gres body (Fig. 9) composed as fol-
-- -·-~------------· -·- --10Ws:S5o/~-iTTitic-k3.-0lill{tiC claY, iS%
sodic feldspar and 20% of the same
quartz-feldspar sand used for the
·mixes described in the previous two
examples: The consi)derationsfor the
previous potassic mix. also are valid
in this case.
Conclusions
The representation of the composition
fields of ceramrc raw materials
in ternary diagrams based on chemical
parameters can be valid when all
the prin"cipal. g~tc,:l~s~ ~[t'U~lcf!n ir].to
consideration. The ternary diagram
which includes silica, alumina and
the sum of the other oxides of the socalled
,
is without doubt the most significant
and the most useful, since the ignition
loss and possible trace elements
remain excluded (generally trace elements
are not determined in the
analyses of ceramic laboratories).
The other two diagrams proposed
are less valid, particularly the
one based only on minor constituents
of the chemical composition. Also for
each individual diagram the significance
of the fields delineated is dif-
. Ierent for the various raw materials.
The ternary diagram Na 2 0 +
K 2 0/Fe-z0 3 + Ti0 2 /Mg0 + CaO, for
example, includes elements which
may be relatively abundant in illiticchloritic
clays and in feldspathic
ro~ks, while they are quite secondary
in illitic-kaolinitic clays and in sands.
In conclusion, such ternary diagrams
can be quite useful for the formulation
of ceramic body compositions
as illustrated by the examples presented.
REFERENCES
BIFFI G., 1976. Studio mineralogico e tecnolo}tico di affioramenti di argille rosse da gres situati in zona
S. Clemente (aN del T. Sillaro). La Ceramica 19 (6), 19-26.
BrFFI G., EMo G., FABBRI B., FroRr C., 1979. Le argille dei

Clays and Complementary Raw Materials ... 545
LoscHI GHITTONI A.G ., 1977. Caratteristiche petrografiche di argille varicolari parmensi. La Ceramica
20 (4), 6-12.
LoscHr GHITTONI A.G., MINOPULOS P., 1976. Caratteristiche mineralogiche e petrografiche di alcune
argille rosse dell'alto Appennino Emiliano in funzione di un loro possibile impiego ceramico.
Ceramurgia 6 (3), 129-135. . . .
PALMONARI C., BERTOLANI M., ALIETTI A., 0RTELLI G., 1974. Emilia-Romagna. Pp. 55-86, in: Giacimenti
di Argille Ceramiche in Ita!ia (F. Veniale and C. Palmonari, editors), Gruppo It

Miner. Petrogr. Acta
Vol. 29-A, pp. 547-562 (1985)
Manufacture of Heavy-Clay Products with the Addition
of Residual Sludges from other Ceramic Industries
C. PALMONARI, A. TENAGLIA
Centro Ceramico, Via Martelli 26,40138 Bologna, Italia
ABSTRACT- Clays of diverse origin are used for the manufacture of heavy clay
products. The chemical and mineralogical characteristics of these clays may
vary within a relatively wide range: for this reason, it was felt worth wile to
investigate the· possibility of using these clays as receivers for ceramic
sludges from the waste water treatment systems of other ceramic industries,
in particular from the ceramic floor and wall tile industry. A typical clay
used for the manufacture of heavy clay products was chosen for the experimental
studies. Various quantities of sludge with different chemical
compositions were added to the clay: the sludges used were classified according
to their lead content which was chosen as the determining parameter.
For mixtures of clays with fixed sludge additions, the variations in structural
characteristics and dimensions were evaluated as a function of firing temperature.
Introduction
Chemical and mineralogical characteristics
of clays employed in Italy
for heavy-clay products may vary
within a relatively wide range
(Tables 1 and 2). Based on data from
scientific literature on this topic
(TENAGLIA, 1982) and contacts with
the national and international heavyclay
industry it can be seen that there
is no other ceramic product for which
such a variation of raw materials is
employed. It is worth wile to note that
the raw materials used in a factory
may vary slightly, depending on un-
TABLE 1
Chemical analysis (%) of clays for heavy-clay production
) 2 3 4 5
L.I. 15.54 15.70 18.56 16.52 15.42
SI02 49.50 46.01 39.24 46.12 47.31
Al20 3 13.46 13.62 15.01 14.81 14.23
TI02 0.27 0.23 ' 0.45 0.09 0.07
Fe 2 0 3 3.98 4.48 3.74 6.21 6.51 '
CaO 11.90 13.52 1.6.74 11.51 10.21
M gO 1.94 1.75 2.51 0.86 1.68
KzO 2.11 2.28 2.25 1.92 2.07
NazO 1.84 2.02 1.19 1.97 2.04
CaC0 3 20.51 22.37 28.30 20.22 18.78

548 C. Palmonari, A. Tenaglia
CLAY
MINERALS
TABLE 2
Raw materials for heavy-clay products
l
kaolinite
smectite
. chlorite
vermiculite
illite-smectite mixed-layers
quartz
NKa
feldspars
{
Ca
calcite
ACCESSORY
carbon.ates dolomite
MINERALS {
siderite
l
goethite
iron compounds
lepidocroci hematite
te
pyrite, marcasite
gypsum
_____ avoidable ___ disuniformities in the_
quarry. Such variations do not exert
any influence on the consistency of
the product properties. For this
reason, it was felt worthwile to investigate.
the possibility of using
these clays as receivers for ceni.mic
sludges from the waste water treatment
systems of the ceramic floor·
and wall tile industry.
Ceramic sludges
The sludges obtained from the
waste water treatment plants of the
ceramic £loor and wall tile industry
are characterized (PALMONARI et
al., 1983) by the presence of residues
of clay and mixtures of various silicates,
hydroxides and carbonates originating
from the purification of water
containing residues of glazes. On
the basis of recent studies, it was
found that the composition of these
ceramic sludges (Table 3) varied as a
function of the particular type of product
being manUfactured (complete
double firing cycle with red or white
ware, single firing of red or white
ware, only the glost firing cycle), but
always ranged within relatively wide
limits. Present in the sludges are substances
also found in clays (silica,
alumina and oxides of iron, titanium,
calcium, magnesium, potassium and
sodium), metal oxides and carbonates
used for the production Of glazes
(lead, zinc, nickel, copper) and borate
compounds. Therefore, ceramic
sludges may be defined only as
«silica-al umina-based ·inorganic
materials (in nearly all the samples
examined the sum of silica and alumina
exceeds 50%) containing variable
amounts of heavy metals, alkali
and alkaline-earth elements».
X-ray diffraction analysis (Table 4)
allowed rough estimates of the
various crystalline species to be
obtained. On the basis of the results,

Manufacture of Heavy-Clay Products -with the Addition ... 549
TABLE 3
Average chemical analyses and ranges of variability of sludges collected, relating to the
production type ·
Production type
A B c D E F
Loss on % 5.94 10.97 1.78 8.83 10.30 11.43
ignition 2.47-12.96 3.42-33.70 1.40-2.05 3.66-15.97 8.81-10.73 1.60-37.09
Si02 % 49.05 39.81 52.94 41.48 41.02 34.15
30.30-59.54 10.74-59.37 48.67c57.12 36.87-49.14 40.99-48.27 15.31-48.37
Al203 % 9.25 12.12 9.92 11.76 13.12
7.24-10.56 6.01-20.77 8.37-10.52 8.63-19.25 9.37-15.69
TiO % 0.22 0.65 0.08 1.58 2.84
0.12-0.35 0.14-1.09 0.03-0.27 0.09-3.87· 1.69-3.89
CaO % 3.34 6.27 1.53 6.96 4.49
2.14-5.82 1.78-15.47 0.88-2.15 0.21-21.21 2.29-7.96
MgO % 0.32 0.37 0.34 1.10 0.57
0.13-0.7~ 0.17-0.82 0.19-0.59 0.27-1.69 0.38-1.77
B203 % 8.02 6.40 8.63 5.37 3.91
6.36-11.25 4.86-10.53 5.82-10.37 2.79-9.36 2.13-5.96
Zr02 % 3.83 2.72 2.91 6.36 2.05
1.07-5.31 2.42-3.40 1.85-3.83 2.13-10.66 0.61-3.15
Fe203 % 1.41 3.94 IS' 1.01 5.66 3.74
0.70-2.99 0.74-12.73 0.81-1.27 3.19-11.24 2.28-5.12
PbO % 9.02 11.42 11.04 5.85 0.49 -
2.84-15.94 1.20-24.02 4.98-16.39 0.64-15.41 0.15-1.18
ZnO % 5.40 1.98 1.95 4.02 4:44
1.82-15.82 0.99-2.84 0.55-3.27 1.56-7.26 0.37-8.25
CdO % 0.00 0.03 0.02 0.01 0.00
0.00-0.14 0.00-0.06 0.00-0.05
NiO % 0.09 0:07 0.00 0.02 .· 0.03
0.00-0.19 0.00-0.18 0.00-0.06 0.01-0.11
CuO % 0.04 0.04 0.00 0.38 1.83
0.00-0.16 0.00-0.11 0.01-0.96 0.00-3.96
MnO % 0.03 0.19 0.04 0.32 1.76
0.00-0.08 0.06-0.63 0.01-0.08 0.08-0.94 0.35-3.71
CoO % 0.17 0.03 0.01 0.01 0.00
0.01-0.53 0.00-0.09 0.00-0.09 0.00-0.06
Cr203 % 0.06 0.24 0.09 0.07 0.11
0.00-0.14 0.13-0.42 0.05-0.21 0.00-0.18 0.06~0.41
Li20 % 0.14 0.07 0.02 0.11 0.16
0.02-0.43 0.00-0.21 0.01-0.08 0.04-0.18 0.09-0.29
K20 % 2.42 0.88 0.95 1.67 0.92
0.82-3.96 0.20-1.41 0.51-1.32 0.75-2.96 0.59-1.61
Na20 % 2.16 1.74 3.09 1.48 2.46
1.53-3.31 0.41-2.93 1.34-3.95 0.88-2.09 2.13-3.07
er- % 0.62 0.09 0.23 0.42 n.d.
0.10-1.60 0.01-0.16 0.01-0.39 0.03-0.91
10.77
5.91-30.59
0.57
0.37-0.72
7.58
0.59-17.98
0.35
0.21-0.86
6.42
2.19-11.19
1.99
1.16-3.31
3.78
1.55-8.31
'16.83
1.63-28.39
1.75
0.46-4.55
0.01
0.00-0.04
0.07
0.00-0.22
0.07
0.00-0.17
0.31
0.00-1.83
0.03
. 0.00-0.17
0.17
0.01-0.53
0.12
0.05-0.22
0.71
0.29-L73
1.32
0.51-2.39
0.30
0.07-0.62
A) 5 factories producing majolica (complete double firing cycle)
B) 7 factories producing cottoforte (complete double firing cycle)
C) 5 factories producing whiteware bodies "(complete double firing, cycle)
J:?) 5 factories producing red-ware bodies (si~gle firing cycle)
E) 5 factories producing light colored ware (single firing cycle)
F) 7 factories for glazing the tiles (factories where only the glazing and glost firing operations
are carried-out)
,_
the sludges have been divided into
the following groups:
a) sludges from purification systems
in factories producing majolica,

550 C. Palmonari, A. Tenaglia
TABLE 4
X-ray diffraction analyses of sludges, relating to the production type as in Table 3
Production type
Crystalline species A B c D E F
Zircon m m m m se m
a-Quartz se se tr m ab m
Calcite tr se a tr m tr
Na-feldspar a a a ,, tr m a
ZnO tr a a a se a
Hematite a a a tr tr tr
TiOz a a a tr se a
Kaolinite se tr m tr m se
Other clay minerals a a a tr tr a
Amorphous phase ab ab ab ab se ab
ab: abundant, ~: medium, se: scarce, tr: traces, a: absent
cottoforte, whiteware bodies, singlefired
red-bodied ware and from factories
carrying out only the glazing
________________ a~d glost ~ring operations; ~
b) sludges from purification systems
in factories manufacturing
single-fired, light-colour products.
In the first case the waste waters
contain glazes with high frit contents
and thus have high concentrations of
dissolved metals, especially lead and
zinc; purification of these waste waters
is obtained mainly by a process
of flocculation, with the formation of
insoluble amorphous substances
which tend to trap the crystalline
substances present inside the floes,
even though in small quantities
(quartz, feldspars). An exception to
this occ;urs with the zirconia-bearing
sands which, because of their high
density (4.56 g/cm 3 ), separate from
the turbide waters by simple sedimentation
without being incorporated
in the precipitated floes. Indication
of this phenomenon is found
in the characteristic bell shape which
amorphous material gives to the
background of the X-ray diffraction
patterns.
The higher firing temperature used
for the single-fired light-colour
bodies permits the use of glazes with
relatively modest amounts of frit and
sometimes no frit at all is used in the
glazes employed in this process;
however the percentage of additives
in th~ mill is high. The waste waters
from this process contain a large
amount of material in suspension
and lower quantities of dissolved
metals. The sludges resulting· from
the purification of these waste waters
contain high quantities of crystalline
materials and a relatively limited
amount of colloidal substances (hydroxides
and/or carbonates of heavy
metals). The amorphous phase is
scarce while, in addition to· the zirconia
sands previously mentioned,
quartz, feldspars and CaC0 3 are also
present, kaolinite, too, is very evident
and originates both from the glaze
and from the raw materials used in
preparation of the tiles.
Waste waters from glazing depart-

Manufacture of Heavy-Clay Products with ihe Addition ... 551
ments contain argillaceous materials
in suspension only in single-firing cycles;
in all the other cases the body is
previously fired, so fragments that
may breakoff are composed of amor­
I?hous alumino-silicates, and there if
no evidence of minerals typical of
clays.
Such heterogeneity in chemical
compositions renders problematic
the reuse of sludges inside the same
ceramic industry; an exception to
this is their introduction into raw
materials for tile bodies. This solution,
however, is not always suitable
(for example in factories where only
the glazing and glost-firing operations
are carried out).
Dispo~al and re-use for heav:y clay
products ,
As documented in the literature,
raw materials for heavy-clay products
have been shown in various
ca_ses to be good receivers of residue
sludges of diverse origin.
The aspects which led to the consideration
of dispersing predetermined
quantities of sludge iiJ. the raw
materials for the ma:~;mfacture of
J::teavy clay products as a possible
means of disposal and reuse of ceram- ·
ic 1 sludges deriving from floor and
wall tile production are the follow- \
ing:
a) the characteristic extreme
variability in composition of these
ceramic sludges, not only from one
factory to another, but also within
the same factory from ·on~ day to
another, according to the changes in
production;
b) the toxicity of these ceramic
sludges;
c) the water content of these
sludges at which they can be transported
without excessive cost;
d) the massive presence of low
melting point substances in these
sludges.
In fact, raw materials for the
manufacture of heavy~clay products
are

552 C. Palmonari, A. Tenaglia
the Edilfornaciai factory in the Province
of Bologna (Italy), manufacturing
heavy clay products. It is a sandy,
calcareous clay from the Olocene (recent
Quaternary) characterized by a
relatively large amount of smectite
and illite in the day fraction. On the
basis of particle size analysis the
Edilfornaciai clay may be classified,
according to SHEPARD (1954), as a
sandy silty clay. From these results
this clay can be described as being a
typical raw material for the manufacture
of heavy clay products (Table 5
and Figs 1, 2 and 3).
Laboratory tests
~--~-~--- ~--~--~~- Tn c5rd~erto evaluate the~effeds of
sludge additions on the technical
characteristics of fired products,
clay-sludge mixtures were prepared
using the dry~i~~i~g p~o~~s~:~
A sludge with a medium-high lead
content (ranging from 15% to 17%)
was used. This parameter was felt to
be discriminative, based on data
from chemical analyses, relative to
the various production types, and on
the relevant fluxing action of this element.
The batches (with 0%, 5%,
10%, 15% sludge content) were drymilled,
granulated, dried, pressed
into 40 mm diameter, 4 to 6 mm thick
disks and fired at temperatures ranging
from 950° to 1100 °C. Determinations
of linear shrinkage and water
absorption were made on the resulting
fired disks.
The results (Fig. 4) illustrate the
TABLE 5
Edilfornaciai clay
Chemical composition (%):
Loss on ignition
11.67
SiOz
56.90
Alz03
13.64
Carbonates: 18.92
Ti0 2
0.19
CaO
9.36
M gO
0.45
K 2 0. Na 2 0
2.01 1.42
Gravel
Coarse sand
Fine sand
Silt
Clay
Particle size (J.Lm)
>2000
2000-256
256-63
63-3.9
3

Manufacture of Heavy-Clay Products with the Addition ... 553
42 39 36 33 30 27 24 21 18 15 12
Fig. 1 - X-ray diffraction patterns of the Edilfornaciai Clay:·a: in acetone; b: ·in H 2 0.
2e
fluxing action of the sludges, in particular
for additions greater than
10%. However, phenomena of softening
or excessive deformation did not
occur to such an extent so as to " ex-
elude the use of sludges presumably
even in fractions greater than those
studied.
Additional day-sludge mixtures
were prepared, containing 0, 10, 20
30 27 24 21 18
15 12
Fig. 2 - X-ray diffraction patterns _of the oriented clay fractions of the Edilfornaciai clay. a: natural;
b: glycolated; c: heated at 550 oc for 2 hours. '
29

554 C. Palmonari, A. Tenaglia
Fraction < 2!'-m 70
Temperature ( °C)
885
- · ~- -~-~~--- --- --~----~~---~-- -~--0~ ~--lOO-~.-·. 200 --~- 300 --400 - 500 - .600. ~ - 700 800 900
Fig. 3 -Differential thermal analyses of the Edilfomaciai clay.
and 30% sludge from which'test bars
were obtained by extrusion with a
laboratory extruder. The test bars
were fired in an industrial kiln at 980
cc using a 28 h firing cycle. Bending
strength and water absorption of the
fired pieces were measured (Fig. 5).
Neither of those two parameters
seem to undergo important variations
with sludge contents up to 20%;
with 30% sludge, however, the bending
strength was distinctly greater,
by about 30%, than that of the test
pieces without sludge additions. The
fluxing action of the sludges also is
clearly evident in the colour and external
appearance of the samples,
which tend to look «Overfired>> with
increasing frequency as the sludge
content increases.
Microstructural characterization
of fired samples was performed with
optical microscopy and scanning
electron microscopy. The results (Fig.
6) show the presence of fuse-d phases
increasing with increasing sludge
content. The higher glass content
promotes: i) the formation of large
but not communicating pores (mostly
closed porosity), and ii) a higher degree
of cementation which imparts
increased mechanical resistance to
the fired products.
The highest sludge contents promoted
the presence of recrystallization
in cavities caused by localiz,ed fusion.
This phenomenon results from the
shaping technique adopted for preparing
the laboratory samples (extr:usion),
typical for heavy clay products

Manufacture of Heavy-Clay [>roducts with the Addition ...
555
20
16
12
8
4
::.:. -== =-=--: ---- !---
-·-- ---- -··-··-··- ·--·---.... r- a b
-··-
-.......
~ .......... '.../.
W.A. .........
......... '
.........
r· '
~. c '
"\
·~ \~/d
~
0::::
0
:;::;
c.
s..
0
V1
.0
c:r:
s..

556 C Palmonari, A. Tenaglia
a
b
c
Fig. 6 - Scanning electron micrographs of the fired samples. a: without sludge additions;
b: with 10% sludge additions; c: with 30% sludge additions.

Manufacture of Heavy-Clay Products with -the Addition ... 557
but which does not achieve optimum
mixing of the raw material.
Industrial scale tests
Verification of the laboratory results
was organized in four series of
industrial tests carried out at the
Edilfornaciai factory in Fiesso, Castenaso,
Province of Bologna (equipped
with camera dryers and a mobile
flame Hoffman-type kiln). In the first
three tests, verifications were made
on a small scale (1000 bricks) of the
results obtained with mixtures previously
studied in the laboratory. A
comparison of the fired products
without sludge additions fired at the
same time as those with sludge additions
showed that increasing sludge
additions (8%, 15%, 20%, 25%) only
caused a decrease in water absorption
of the fired samples (from _16% to
13%). No particular production problems
were encountered in any phase
of the technological cycle.
Successively a larger scale series
was carried out: three days of production
for a total of 100000 perforated
bricks with a 25% sludge addition;
four different firing curves characterized
by maximum temperatures
of 800°, 850°, 900° and 1000 oc were
employed. The time-temperature relationship
characteristic of mobile
500
400
300
e
I
N
u
......
I
en
I
-" I
~
_,..
I
..

flame kilns was followed using thermocouples
dropped down from the
ceiling of the kiln and positioned inside
the piles of bricks to be fired. The
most interesting result is the increase
in compressive strength (Fig. 7),
which went from 283 kg/cm 2 for normal
production to 396 kg/cm 2 for
bricks containing the sludge additions
and fired at the same temperature;
even materials fired at lower
temperatures show an increase in
compressive strength, with respect to
normal production, which went from
361 kg/cm 2 at 900 °C, to 340 kg/cm 2 at
850 oc and 306 kg/cm 2 at 800 °C. The
compressive strength after 20 freezethaw
tests conformed to the require-
~------~~-
558 C. Palmonari, A. Tenaglia
ments of Italian Standards. The extentofwater
absorptionoJ}'iig .. 81}Y::_ts
always slightly lower for the bricks
containing the sludge additions than
for normal production; however, the
values were always well within the
requirements of the UNI 5632 Standard
(the water absorbed by dry
heavy clay products falls between 8%
and 28%).
A study was made on the environmental
impact of the addition of
ceramic sludges to the clay used in
the manufacture of heavy clay products.
Comparison of the data
obtained during normal production
with those obtained when sludge
additions were made showed that no
Water
Absorption (%)
15
10
Fig. 8 - Variations in water absorption of test bricks with sludge additions as a .function of firing
temperature. For comparison, .also shown is the value relative to bricks of normal production
'
without sludge additions (fired .at 980-1000 °C).

Manufacture of Heavy-Clay Products wfth the Addition ... 559
Pb
1. 6 (mg/Nm 3 )
0.8
400
200
16
8
0~~~~~~~~~~~~~
160~~~~~r.rl~~~~b7~77~~~"+r'-"~V7TTrn~777i
80
0
800
400
0
' '
'
Time. (h)
6 2 18
Fig. 9 - Concentrations of pollutants in the stack emission during firing of the bricks containing
sludge additions. Pb: Lead compounds; SO,: Sulphur oxides; F: Fluorine compounds; Pv: Particu-
. late matter.
(!)
0"">
,__ ro
(!)
>
c:(

560 C. Palmonari, A. Tenaglia
particular problems arose at any
level (pollutant emissions, workroom
environment, release of heavy metals
from fired samples).
A study was made on the environmental
impact of the addition of
ceramic sludges to the clay used in
the manufacture of heavy clay products·.
During the entire firing cycle
for the industrial scale tests, samples
were taken of the stack emissions and
analyzed for total suspended particles,
lead compounds, fluorine compounds
and sulfur oxides. Analogous
analyses were made during normal
production before the sludge additions
were made to the raw materials.
The values of the concentration
_______ _ ----of -pGllutants-measured- duFing the
tests (Fig. 9) with sludge additions
were not appreciably different from
those associated whh'normal production.
This means that for the dosage
studied, - i:l:ie a'ddi-1Io~-~-;;:f~ c~~amic
sludge to the raw materials did not
create situations with regard to the
pollutant em1sswns appreciably
different from those associated with
normal production. With regard to
lead, whieh is absent under normal
production conditions, it was found
that more than 70% of the determinations
-gave values corresponding to
concentrations less than 0.6 mg/Nm 3
and that 65% of the determinations
gave values less than 0.4 mg/Nm 3 • For
comparison, the standard set for the
ceramic floor and wall tile industry is
a maximum of 0.5 mg/Nm 3 .
Samples of air within the workroom
environment were taken during
the industrial tests in order to evalu-
- 3
r·1inera1 dusts
(mg;m3)
Lead
(JLg/m3)
6
2
·-·-·-·-·- .
Pb,Test
·-·-·-·--. j_
............ ·-·--·
~1d,Test .......
J_. .... ....-:
-=~
-' ---,
·- • Md,Production
Stacking of dr~ bricks
1
Extruder 2 3
Right side
Left .si de
Fig. 10 - Average concentrations of lead and of the suspended mineral dusts in the workroom
environment during normal production and during the industrial scale tests with sludge additions
to the raw materials. -
l
4
2

Manufacture of Heavy-Clay Products with the Addition ... 561
ate the possible risk involved in the
use of material containing lead compounds.
The results, reported in Fig.
10, show that the concent~ations of
suspended particles and lead are well
below the limits established by the
ACGIH (American Conference of Governmental
Industrial Hygienists).
The extent to which the ceramic
sludges had been rendered innocuous
by the mixiJ:.Lg with clay and subsequent
firing was evaluated by stucljes
of heavy metal release by the fired
brick. Heavy metal release, in particular
Pb, Zn and Fe, was determined
using the leaching method
proposed by the U.S. EPA (Environmental
Protection Agency). The
values of the concentrations of the
heavy metals leached are shown in
Fig. ll. The· results show that firing
the sludges mixed with clays renders
Leaching (mg/1)
50
10
8
6
4
2
Fig. 11 -Results of leaching test carried out on the test bricks with sludge additions fired at various
temperatures. For comparison, the limits of acceptability are also show\1.

562 C. Palmonari, A. Tenaglia
them sufficiently innocuous. Already
at the lowest firing temperature studied
(800 °C) the release of the heavy
·metals · analyzed for was well below.
the limits of acceptability. As the firing
temperature was increased above
800 °C, heavy metal release from the
fired products decreased because of
the formation of a greater amount of
glassy phase in the products to hold
the heavy metals present with the
formation of stable, inert silicates
and alumino-silicates.
Conclusions
The clay for heavy-clay products
can be considered a good receiver for
the residual sludges from treatments
of waste wa ters~~fromthe ce~amic
floor and wall tile industry. Disposal
and reuse can be easily achieved because
of the relatively wide range of
variability in chemical characteristics
of the raw materials as well as
the typical features of the technological
cycle used for heavy clay production.
This solution allows improvements
in the qualitative properties
of the fired products to be
obtained along with energy savings
as well as rendering these sludges innocuous,
sludges which once were
considered not only unusable, but
also toxic and harmful.
REFERENCES
PALMONARI C., BERTOLANI M., ALIETTI A., 0RTELLI G., 1974. Emilia-Romagna. Pp. 55-86, in:
Giacimenti di Argille Ceramiche in Italia (F. Veniale and C. Palmonari, editors), Gruppo Italiano
A.I.P.E.A., Cooperativa Libraria Editrice, Bologna.
PALMONARI C., TENAGLIA A., TIMELLINI G., 1983. Jnquinamento idrico da industrie ceramic he- Smaltimento
e riutilizzo dei fanghi residui. Ed. Int. Centro Ceramico Bologna.
SHEPARD F.P., 1954. Nomenclature based on sand-silt-clay ratios. 1. Sediment. Petrol. 24, 151-158.
TENAGLIA A., 1982. Piu argille per laterizi. L'Ind. Italiana dei Laterizi 1, 11-16.

Miner. Petrogr. Acta
Vol. 29-A, pp. 563-575 (1985)
High Temperature Reactions and Use of Bronze Age
Pottery from La Mancha, Central Spain
J. CAPEL 1 , F. HUERTAS 2 , J. LINARES 2
1 Departamento de Prehistoria y Arqueologia, Facultad de Filosofia y Lettras, Poligono Universitario de Cartuja,
18012 Granada, Espafta
2 Estaci6n Experimental del Zaidin C.S.I.C., Profesor Albareda 1, 18008 Granada, Espafta
ABSTRACT- In La Mancha (Ciudad Real) there are numerous hills of low
altitude called «Motillas>> which very often correspond to prehistoric settlements
which date from the late Copper to Bronze Ages. Sixty eight ceramic
fragments of different typologies belonging to eleven archaeological sites were
studied by X-ray diffraction. Taking into account the regional geology, seve-.
ral clayey sediments close to the archaeological sites were selected under the
assumption that they would be similar to the raw materials of the ceramics.
Test pieces were moulded and fired at several temperatures (standard test
pieces) and were studied following the same scheme as that for the
archaeological ceramics. In order to simulate the effects of a long-lasting
burial the test pieces were submitted to autoclave treatment.
In general, the mineralogical composition of the archaeological ceramic
pieces coincides with that of the standard test pieces fired at 700-800 °C.
Therefore it can b.e concluded that most of the ceramic pieces of Bronze Age
in this zone are mamifactured with materials neighbouring the settlement.
Furthermore, free energies as a function of temperature were calculated for
nine reactions accounting for destruction and neoformation of the different
phases of the mineralogical ceramic system.
Comparison of the theoretical data with the actual mineralogical composition
of the ceramic pieces shows that mineral destruction is not fully
achieved at theoretical temperatures; the minerals persist at higher temperatures
due probably to kinetic effects. Furthermore, the neoformed phases
always appear at temperatures higher than the theoretical ones, due to the
necessary recrystalliza tion process.
Through the alteration obtained by the autoclave treatment, the mineralogical
transformations due to the effect of burial, as well as those originating
from usage (cooking, etc.) could be reproduced. In both cases there was a
neoformation of smectite from amorphous vitreous material. Smectite is not
found in the raw materials nor in some types of ceramic pieces (for instance,
dishes). However, smectite is always present in cooking pottery,. specially
stewpots. Theoretical calculations show that in this zone burial contributes
minimally to smectite neoformation.
Introduction
1 this work we present some of the
more significant results obtained
from the study of archaeological
ceramics through application of
physical analytical techniques, such
as X-ray diffraction, atomic absorption
spectroscopy and treatment in
an autoclave.

562 C. Palmonari, A. Tenaglia
them sufficiently innocuous. Already
at the lowest firing temperature studied
(800 oq the release of the heavy
metals analyzed for was well below
the limits of acceptability. As the firing
temperature was increased above
800 °C, heavy metal release from the
fired products decreased because of
the formation of a greater amount of
glassy phase in the products to hold
the heavy metals present with the
formation of stable, inert silicates
and alumino-silicates.
Conclusions
The clay for heavy-clay products
can be considered a good receiver for
the residual sludges from treatments
of waste~waters~-fiom the ce~amic
floor and wall tile industry. Disposal
and reuse can be easily achieved because
of the relatively wide range of
variability in chemical characteristics
of the raw materials as well as
the typical features of the technological
cycle used for heavy clay production.
This solution allows improvements
in the qualitative properties
of the fired products to be
obtained along with energy savings
as well as rendering these sludges innocuous,
sludges which once were
considered not only unusable, but
also toxic and harmful.
REFERENCES
PALMONARI C., BERTOLANI M., ALIETTI A., 0RTELLI G., 1974. Emilia-Romagna. Pp. 55-86, in:
Giacimenti di Argille Ceramiche in Italia (F. Veniale and C. Palmonari, editors), Gruppo Italiano
A.I.P.E.A., Cooperativa Libraria Editrice, Bologna.
PALMONARI C., TENAGLIA A., TIMELLINI G., 1983. Jnquinamento idrico da industrie ceramic he- Smaltimento
e riutilizzo dei fanghi residui. Ed. Int. Centro Ceramico Bologna.
SHEPARD F.P., 1954. Nomenclature based on sand-silt-clay ratios. 1. Sediment. Petrol. 24, 151-158.
TENAGLIA A., 1982. Piu argille per laterizi. L'Ind. Italiana dei Laterizi 1, 11-16.

Miner. Petrogr. Acta
Vol. 29-A, pp. 563-575 (1985)
High Temperature Reactions and Use of Bronze Age
Pottery from La Mancha, Central Spain
J. CAPEL 1 , F. HUERTAS', J. LINARES'
1
Departamento de Prehistoria y Arqueologia, Facultad de Filosofia y Lettras, Poligono Universitario" de Cartuja,
!8012Granada,Espafia
2 Estaci6n Experimental del Zaidin C.S.I.C., Profesor Albareda I, 18008 Granada, Espafia
ABSTRACT- In La Mancha (Ciudad Real) there are numerous hills of low
altitude called «Motillas» which very often correspond to prehistoric settlements
which date from the late Copper to Bronze Ages. Sixty eight ceramic
fragments of different typologies belonging to eleven archaeological sites were
studied by X-ray diffraction. Taking into account the regional geology, seve-.
ral clayey sediments close to the archaeological sites were selected under the
assumption that they would be similar to the raw materials of the ceramics.
Test pieces were moulded and fired at several temperatures (standard test
pieces) and were studied following the same scheme as that for the
archaeological ceramics. In order to simulate the effects of a long-lasting
burial the test pieces were submitted to autoclave treatment.
In general, the mineralogical composition of the archaeological ceramic
pieces coincides with that of the standard test pieces fired at 700-800 °C.
Therefore it can b.e concluded that most of the ceramic pieces of Bronze Age
in this zone are manufactured with materials neighbouring the settlement.
Furthermore, free energies as a function of temperature were calculated for
nine reactions accounting for destruction and neoformation of the different
phases of the mineralogical ceramic system.
Comparison of the theoretical data with the actual mineralogical composition
of the ceramic pieces shows that mineral destruction is not fully
achieved at theoretical temperatures; the minerals persist at higher temperatures
due probably to kinetic effects. Furthermore, the neoformed phases
always appear at temperatures higher than the theoretical ones, due to the
necessary recrystallization process.
Through the alteration obtained by the autoclave treatment, the mineralogical
transformations due to the effect of burial, as well as those originating
from usage (cooking, etc.) could be reproduced. In both cases there was a
neoformation of smectite from amorphous vitreous material. Smectite is not
found in the raw materials nor in some types of ceramic pieces (for instance,
dishes). However, smectite is always present in cooking pottery,. specially
stewpots. Theoretical calculations show that in this zone burial contributes
minimally to smectite neoformation.
Introduction
1 this work we present some of the
more significant results obtained
from the study of archaeological
ceramics through application of
physica1 analytical techniques, such
as X-ray diffraction, atomie absorption
spectroscopy and treatment in
an autoclave.

564 J. Cape/, F. Huertas, J. Linares
Most of the sherds analyzed here
come from the archaeological excavation
of the

High TemperatureReactions and Use-of Bronze ... 565
during heating and the consequent
formation of high temperature
phases. It is therefore worthwhile to
establish a theoretical scenario
which allows the prediction of composition
variations. We have based
such a scenario on the evaluation of
free energy release in the relevant
reactions, which should take place in
the clay matrix during the firing process.
As starting components we have
chosen phyllosilicates (illite), quartz,
calcite and dolomite. Other usual
components of a clay such as plagioclase
and K-feldspar have been rejected
due to its scarce presence in
our ceramic samples, which reduces
its possibile influence on the .reactions.
The inclusions of these components
would unnecessarily complicate
the computation. The most relevant
high temperature phases, such
as wollastonite, anorthite, K­
feldspar, diopside and enstatite are
explained with the reactions considered.
They are the following:
-
A) gehlenite formation
illite calcite gehlenite
K Alz (Si3Al)010(0Hh + 6 Ca C03 ~ 3 Ca2SiAlz07 +
+ 6 C02 + 2 H20 + K20 + 3 Si02
B) anorthite formation
illi te
"
calcite
K Alz (Si3Al)010(0Hh + 3 Ca C03 ~
+ 3 C02 + 2 H20 + K20
C) wollastonite formation
D) diopside formation
anorthite
3 Ca Alz Si20s +
quartz calcite wollastonite
2 Si 0 2 + ea co3 ~ ea Si 03 + C02
quartz
dolomite
diopside
2 Si02 + Ca Mg (C03h ~ Ca Mg Si206 + 2 C02
E) gehlenite and K-feldspar formation ·
illi te
calcite
K Alz(Si3Al)010(0H2) + 2 Ca C03 +
gehlenite
quartz
Si02
+ Ca2AlzSi07 + 2 C02 + H20
K-feldspar
~ K AlSi 3 0 8 +

566 J. Capel, F. Huertas, J.- Linares
F) anorthite and K-feldspar formation
illi te calcite quartz K-feldspar
K Al 2 (Si3Al)0 10 (0H)z + CaC03 + 2 Si0 2 ~ K A1Si30s +
anorthite
+ Ca AlzSi 20 8 + COz + HzO
G) gehlenite, enstatite and K-feldspar formation
illite dolomite quartz
3 Si0 2
K Alz(Si 3 Al)0 10 (0H)z + 2 Ca Mg (C0 3 )z. +
gehlenite enstatite K-feldspar
Ca 2 Al 2 Si 0 7 + 2 MgSi03 + K A1Si 3 0 8 + 4 C0 2 + HzO
H) gehlenite destruction
gehlenite
Ca 2 Al 2 Si 0 7 +
quartz wollastonite anorthite
2 Si0 2 ~ CaSi03 + Ca AlzSizOs
I) gehlenite destruction
gehlenite
Ca 2 AlzSi 0 7 + KzO +
quartz K-feldspar
5 Si0 2 ~ 2 KA1Si30 8 + . 2 CaO
The sign of the free energy variation
produced in each reaction AG =
~AG final products - ~AG initial
componer1ts obviously indicates the
sense in which the reaction will preferentially
take place under the given
pressure and temperature conditions.
The AG values are therefore an indication
of stability and of creation
or destruction of a certain mineral at
a given temperature. For each mineral
specimen we have used the AG
values given by ROBIE & WALD­
BAUM (1968). In Fig. 1 we have plotted
the variations of AG with temperature
for the different reactions listed
previously. As can be seen, reactions
A and B producing gehlenite and
anorthite from illite + calcite behave
in a similar way with temperature
variations. The sign of AG in both
reactions changes from positive to
negative around 670 °C. However,
these reactions not only require a
sufficiently high temperature, but
also a suitable velocity. Due to this,
the production ofgehlenite and anorthite
through reactions A and B is not
significant below 800 oc (BARAHO­
NA, 1974). Reactions E and F must be
also considered in the production of
these phases. Up to 870 °C, E is more
probable than A, i.e. AGE

High Temperature Reactions and Use-o(B~onze ... 567
0
0
E
......
';;;
-40
u
::.::
200 400 600 800 1000 1200
"' ""1
-80
-120
80
40
0
-40
-80
0
E
......
';;;
u
::.::
"'
"
-120
~160
-200...J_---,--,...--..-----.-----.----..,,.-----.
200 400 600 800 1000 1200
Fig. 1 -Variation of D.G with temperature for\the different mineralogical reactions.
reaction F is preferred to B up to 1000
oc for the same reason. With respect
to reactions E and F we point out that- ·
the quantities of K-feldspar produced
by them in laboratory experiments
(BARAHONA et al., 1985) are not significant
due probably to its formation
as a vitreous phase, which
actually contributes to the stiffness of
the fired vessels. .

568 J. Cape/, F. Huertas, J. Linares
The LlG variations for reactions C
and D indicate a higher probability
for the formation of diopside than
wollastonite, but the latter actually
presents larger abundances due
mainly to the higher content in calcite
than in dolomite in the original
sediments.
Finally, we alsonote that reactions
H and I describing destruction of
gehleni te-'-caiL~ ,take .... place- .. at . all
temperatures (llG

and the theoretical considerations
just outlined are complemented with
the data obtained from the analysis
of a test ceramics sample elaborated
and fired in the laboratory. These
data are represented in Fig. 2, which
shows the absence of the clay minerals
at temperatures above 800 oc and
not 900 °C, as would be expected.
This is due to the exceedingly small
particle size of the available illite
(Table 1).
Otherwise, the curves can be used
to interpolate the results of our
mineralogical analysis and to get relatively
accurate estimates of the fir- ...
ing temperatures. However, this determination
can be affected by errors
coming from the unknown composition
of the original clay and the influences
that it has on the foriD;ation of
new phases during the firing process.
'
With the procedure outlined, we estimate
baking temperatures ranging
between 690 oc and 735 oc for 60% of
the samples and above 735 oc for the
remaining sherds.
In order to ve:dfy the validity of the
estimated firing temperatures, we
have refired the sherds of the samples
to a temperature of 1000 °C. In Fig. 3
we show the results of a comparison
between the mineralogical composition
of the refined pieces and that of
the original ones. As can be seen in
this figure, phyllosilicates and calcite.
High Temperature Reactions and Use of Bronze ... 569
are completely destroyed, whereas
the amounts of K-feldspar, plagioclase,
gehlenite and diopsidewollastonite
present a relative increase.
We also searched for a possible correlation
between thickness of the
sherds and formation of high temperature
phases. This correlation can be
reasonably well reproduced by a
linear least squares fit, given by the
equation:
T = 760.34- 4.29 C, r = 0.40, N = 25.
T is the firing temperature and C the
thickness in millirneters. As it was expected,
formation of high temperature
phases is favoured in thinner
sherds, where homogeneization is
easier and faster.
Influence of use and burial
We now turn to the discussion of
possible modifications in mineralogical
composition, which may have
been casued by the use given to the
vessels and by the later burial period,
through an hydrolysis effect. This
effect was simulated on our test
pieces by submitting them to treatment
in an autoclave at a temperature
of 130 oc and a pressure of 2
atmospheres. X-ray diffraction analyses
of the samples were carried out
during this treatment at regular, pre-
TABLE 1
Illite parameters. Mean values
~r~:(t\li.~~~~ .. :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::· 17~:~i!9~:~i ~~j
/

570 J. Capel, F. Huertas, J. Linares
30
Archaeological Arch~ological Ceramics
Ceramics
10
20
60
20
o-l-.....---.--r---,----l=~==;:=:::::~f-:.....---r--.....---.---:==:----!:=1---.
60
K-F
-----~ ~~-28
rtl
~ 40
4-
0
• Pla
~ a+-~~~~~~~~~~~~~~~~--.
60
20
D+W
80
Geh
40
01+---.-~--,-~~~~--~~~~~~~~~~~
80
Hem
40
t~i nera l %
-Fig. 3- Differences between the mineral contents of the refired archaeological ceramics (lQOO •c)
and those ofi:he original ones. Mineral abbreviations as in Table 2.

High Temperature Reactions arrd·Use-of Bronze ... 571
.\ .. ~ ..
20
viously fixed time intervals. The re- ..--0--..:::::::
suits of this experiment are reported .;, "'
10
in Table 2 and plotted in Fig. 4.
It is interesting to note that the
most significant v.ariations of come
position with time of treatment in the ·
autoclave are shown by" those test
fragments fired at 800 °C. We find
in these fragments significant
20
neoformation and destruction of .::1
c
minerals, as is the case of phyllosili- .!::
10 ~
cates and quartz, respectively. The· ..
test pieces fired at 700 oc do not show
any. relevant changes, except the
clear increase in the calcite content.
Otherwise, this increase becomes less
.. o~o
.·--·--·~
c------------
200 400
200 400
~c--c-
10

--------~---
-28-·
572 J. Cape/, F. Huertas, J. Linares
TABLE 2
Mineralogical alteration of the test fragments with time of treatment in autoclave
"-'""-" o• -- --~~-
T t Phy Qz Cal K-F Pia D+W Geh Hem
oc hours % % % % % % % %
700 0 78 13 8 1
700. 260 72 12 14 0.5
700 310 86 12 10 0.5
700 362 72 13 14
800 0 21 34 5 18 16 5
800 26 40 36 5 6 5 3 3
800 62 41 36 5 6 5 3 3
800 150 43 32 7 4 5 4 5
800 254 49 28 6 4 6 3 3
800 370 37 27 12 5 7 5 5 2
800 512 40 25 9 5 7 7 5 2
800 562 43 21 13 4 8 5 5 1
800 614 36 28 14 5 5 6 4 2
800 622 28 28 14 8 7 6 5 4
900 0 14 28 6 26 17 5 .. 4
900 260 26 22 10 12 18 8 4
900 310 16 24 5 12 16 15 8 4
900 362 21 24 13 15 15 9 3
950 0 11 8 26 19 6 2
950 260 0.5 28 2 13 31 17 5 4
950 310 0.5 24 3 20 25 19 6 3
950 362 0.5 23 4 25 24 15 7 2
Phy: phyllosilicates; Qz: quartz; Cal: calcite; K-F: K-feldspar; Pia: plagioclase; D+W: diopside+wollastonite;
Geh: gehlenite; Hem: hematite
evident the higher th~ firing temperature.
Plagioclase and K-feldspar behave
exactly as would be expected
from their known formation prop-
' erties. The former presents a clear decrease
in the pieces fired at 800 oc
during the first hours in autoclave
and remains constant thereafter. In
our opinion, this is due to the small.
particle size of the plagioclase
neoformed during the firing process
which makes it easily hydrolyzable.
On the other hand, the increase of K­
feldspar in the 900 oc sherds can be
explained by neoformation of this
mineral, which is favoured in a confined
environment by the vitreous
matter produced in the destruction of
the phyllosilicates.
Among the neoformed high
temperature phases, the stability of
gehlenite stands out, whereas wol-
·lastonite presents a more complicated
behaviour due to the variable
particle size, which actually depends
on the firing temperature ..
In Fig. 5 we show the results of
the X-ray diffraction analysis for the
original test fragments as compared
with those obtained after different
times of treatment in the autoclave.
As can be seen, hydrolysis indeed
changes the mineralogical composition
but somewhat preserves. the

High Temperature Reactions an:dVse of Bronze ... 573
60 ~
40
20
u
E~·
0.. •
~ '950 'C
..
"C 0
o; 0
....
'
"'
20
700 'C
~
% Phy
40 60 80 100
Fig. 5 - Variation of the content in K-feldspar
+ Plagioclase through hydrolysis in autoclave
(see Table 2).
80
"' s..
"' 0.
"0 "'
60 ~
~
..., "' OJ
40 :3
"' 0
..
20 ';:,
s:
-20
clustering around the original values,
avoiding to some extent the mixture
between data of hydrolyzed sherds
fired at different temperatures.
Figure 6 shows the behaviour of the
difference % phyllosilicates ·c- % total
feldspar against firing temperqture
for samples treated in the autoclave.
As can be seen, the use and ageing
cause an increase of this quantity in
the ceramics fired at temperatures
below 900 °C. This increase means
neoformation of phyllosilicates and/
or. destruction of feldspar and is
actually what one would expect as
the result of an intensive hydrolysis
due to use. However, for sherds fired
at temperatures hotter than 900 oc
we find just the opposite effect.
On the other hand, the time of burial
could also influence these trans-\
formations. An indication of that
might be the presence in the
archaeological ceramics of phyllosilicates,
such as montmorillonite,
which are not present in the original
sediments.
-40
T °C
600 700 800 900 1000
Fig. 6 - Influence of the ·use on the mineralogical
composition.
We start from the fact that the
ceramic fragments contain a certain
amount of vitreous matter, which is
essentially an intermediate product
of the reactions forming high temperature
phases from phyllosilicates,
calcite, quartz, etc. This glass should
have a similar composition to that of
the feldspars and therefore in our
estimations we can use the known
data for hydrolysis of feldspars at
room temperature. Following
HELGESON et al. (1969) 0.3 g of
, albite can produce, through hydrolysis
with lliter of water, 0.2 g of montmorillonite
at 25 oc temperature.
We consider now a typical fragment
of cubical shape and lOO g
weight. Assuming a density of 2 g/

Miner. Petrogr. Acta
Vol. 29-A, pp. 577-590 (1985)
Firing Properties of Ceramic Clays
_from Granada Province, Spain
E. BARAHONA 1 , F. HUERTAS 1 , A. POZZUOLF, J. LINARES 1
1 Estaci6n Experimental det Zaidin, C.S.I.C., Profesor ALbareda I, 18008 Granada, Espana
2 Dipartamento di Geofisica e Vulcanologia, Universita di Napoli, Largo S. Marcellino 10, 80138 Napoli, Italia
ABSTRACT - The firing properties of ceramic clays from Granada Province
(Spain) are studied. The properties determined were weight loss, firing
shrinkage, water absorption, crushing strength and mineralogy of specimens
fired at temperatures of 700, 800, 900, 950, 1000, 1050 °C.
The weight loss on firing is closely related to carbonate content. The changes
of firing shrinkage with temperature depend on content and grain size distribution
of carbonates and on clay content.
Calcareous samples exhibit an appreciable firing shrinkage at low temperatures,
but have, in general a greater dimensional stability than non calcareous
ones.
Generally, non calcareous samples show a water absorption capacity 10%
lower than the calcareous ones. Water absorption after 24 hours immersion
in cold water exhibits a similar pattern to water absorption after 5 hours
boiling.
Indexes of resistence to freezing damage found for the samples studied were
not high but this was not judged a limiting factor due to the mild regional
climatic conditions.
Crushing strength in12reases with firing temperature. There is a strong correlation
between crushing strength and clay content, since this is probably
the component that supplies a vitreous cement at low temperatures. The
hygroscopicity of unfired samples is a better predictor of crushing strength
than the clay content.
Finally, the mineralogy of fired test pieces was studied by XRD. The evolution
with firing temperatures of the neoformed phases (gehlenite, wollastonite,
diopside, plagioclase, hematite and anhydrite) was analyzed with the
purpose of aiding in the study of archaeological ceramic fragments.
Introduction
This paper deals with the firing
properties of ceramic clays of Granada
Province (Spain).
The raw materials are used mainly
for the manufacture of structural clay
products. Forty eight samples corre-
sponding to 15 localities were taken.
The geological setting, mineralogy,
molding and drying properties have
been described elsewhere (BARAHO­
NA et al., 1982; 1983; 1985).
Experimental methods
The samples were crushed to 2 mm
This research work was carried-out with the financial support of M.P.I.

578 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
and water was added to prepare a
plastic mass with a water content
corresponding to Rieke's sticky point.
Test pieces, approximately cylindrical
in shape, with a volume of about
20 cm 3 were molded by hand and
dried at room temperature and then
at 16.5 "c:A.Tso~cuoForTquefies; 2cm
on a side were prepared. Test pieces
and briquettes were heated in an
TABLE 1
Weight loss(%) on firing at several temperatures
Firing temperature oc
Sample 700 800 900 950 1000 1050
Ac-11 7.6 13.9 14.2 14.1 14.1 14.2
Ab-ll 10.0 18.4 19.6 19.6 19.5 19.6
Ah-ll 7.9 10.4 10.6 10.6 10.4 10.4
Ah-21 7.5 12.8 12.9 12.9 12.9 13.1
Ah-31 9.4 ll.3 11.5 ll.S 11.5 ll.4
Ah-32 9.1 11.2 11.2 11.3 11.5 11.9
Ah-33 9.4 14.7 15.0 15.0 15.1 15.1
Ah-41 8.0 11.3 ll.4 11.4 11.4 11.3
Ah-51 8.9 11.6 11.8 11.8 11.9 11.9
Ah-52 9.2 13.5 13.8 13.7 13.7 13.8
J-ll 10.6 14.8 15.0 15.0 15.2 15.1
J-12 9.1 14.4 14.6 14.5 14.6 14.7
---------------J:ZT---- -----8os--- 12.0 -u.o 12.1 13.2 14.6
J-31 9.0 15.6 15.8 15.8 16.0 16.6
J-41 9.8 14.5 14.5 14.8 15.6 17.7
J-51 8.6 14.4 14.6 14.8 14.5 14.7
J-52 10.0 17.2 18.0 18.1 18.4 18.8
J-53 8.1 14.3 15.6 15.8 15.6 16.0
J-54 7.6 14.6 18.1 18.2 18.2 18.5
J-55 4.0 7.7 8.1 8.2 8.1 8.0
Mn-ll 7.5 12.6 12.8 12.8 12.9 12.9
Mn-21 6.9 12.3 13.0 13.1 13.2 13.3
Pi-ll 7.0 11.9 11.8 12.1 12.6 12.8
Pi-12 7.6 13.2 13.4 13.5 13.6 14.0
Pi-13 7.4 12.1 12.2 12.3 12.5 13:0
Ch-ll 11.7 19.4 19.7 19.7 20.0 20.0
Ch-12 12.1 19.3 19.6 19.5 19.6 19.4
Ga-ll 10.1 12.2 12.1 12.4 12.3 12.7
Ga-21 7.5 14.2 15.2 15.3 15.2 15.2
Ma-ll 10.2 17.0 17.1 17.3 17.2 17.2
Ma-12 9.5 16.5 17.0 17.0 16.9 17.2
Ma-13 6.8 13.8 16.0 16.0 15.9 15.7
Ma-14 6.1 12.7 16.4 16.3 16.3 16.2
Pc-11 12.2 22.2 22.7 22.8 22.7 22.9
V i-ll 6.2 11.4 13.4 13.5 13.4 13.2
B-ll 7.2 7.0 7.6 7.7 7.6 7.6
B-12 19.0 17.8 18.0 17.9 18.0 18.3
B-13 16.1 19.9 20.0 20.0 19.9 19.9
B-14 14.1 18.9 19.1 19.1 19.1 19.2
B-21 11.7 19.2 19.4 19.5 19.3 19.4
D-ll 9.2 13.5 13.7 13.9 13.8 14.1
G-ll 4.4 4.5 4.6 4.7 4.7 4.7
Mo-ll 2.9 3.1 3.2 3.2 3.4 3.3
Mo-21 2.8 3.0 3.1 3.2 3.1 3.1
Mo-22 7.1 8.4 8.5 8.5 8.4 8.1
Mo-31 7.3 9.6 9.6 9.6 9.6 9.6
Mo-41 5.7 8.5 8.8 8.8 8.7 8.7

Firing Properties of Cera'mic Clays ... 579
electric furnace at 700, 800, 900, 950, ing the first two hours and 200 oc per
1000 and 1050 oc under oxidizing hour during the following hours until
conditions. The temperature was reaching the maturing temperature,
raised at a rate of 100 oc per hour dur- at which the temperature was held
TABLE 2
Linear dimensional change(%) on firing at several temperatures
Firing temperature oc
Sample 700 800 900 950 1000 1050
Ac-11 +1.0 -0.0 -.6 -.1 -.3 +0.0
Ab-11 +1.0 +.1 -.7 -.4 -.5 -.7
Ah-ll +.8 +.1 +.1 +.2 +.1 +.1
Ah-21 +.6 +.4 +0.0 +.1 +.1 +.1
Ah-31 +1.0 +.6 +.2 +.2 -0.0 -.1
Ah-32 +1.0 +.1 -.1 -.3 -.3 -.4
Ah-33 +.8 +.3 -.3 -.3 -.5 -.5
Ah-41 +.8 +.5 +.1 -.1 -.1 -.3
Ah-42 +.9 +0.0 -.5 -.4 -.5 -.6
Ah-51 +.8 +.6 -.1 -.1 -.1 -.2
Ah-52 +.5 -1.0 -1.1 -1.5 -1.5 -1.6
J-11 +.8 . -.2 -.5 -.6 -.8 -.9
J-12 +.9 -.6 -.6 -.7 -.9 -.6
J-21 +.7 -.2 '-.7 -.7 -.9 -.9
. J-31 +.4 -1.0 -1.1 -1.4 -1.7 -1.7
J-41 +.7 -.1 -.1 -0.0 -.2 -.5
J-51 +.6 -.5 -1.1 -1.2 -1.2 -1.0
J-52 +.5 -.'9 -1.4 -1.5 -1.6 -1.8
J-53 +.4 .+.3 "- -1.3 -1.3 -1.3 -1.2
J-54 +.8 +1.3 +1.2 +1.4 +1.3 +1.2
J-55 +.7 +0.0 -.4 -.3 -.7 -.6
Mn-11 +.7 +.3 +.4 -.2 -.3 -.4
Mn-21 +.5 -.4 -.5 -.7 -.6 -.3
Pi-ll +.6 -.1 -.8 -.9 -.9 -.8
Pi-12 +.7 -.1 -.4 -.3 -.3 -.8
. Pi-13 +.8 -.7 -.7 -.6 -.6 -.6
Ch-ll +.7 -.9 -.7 -.6 -.5 -.4
Ch-12 +1.0 -.2 -.3 -.7 -.8 -.5
Ga-ll +.8 +.1 -.7 -.2 -1.6 -.5
Ga-21 +.6 +.2 -.4 -.4 -.4 -.7
Ma-ll +.6 -.7 -.9 -1.2 -1.2 -1.1
Ma-12 +.6 -.8 -1.1 -1.0 -1.4 -1.3
Ma-13 +.7 +.4 -.6 -.6 -.4 -.6
Ma-14 +.8 +A -.5 -.1 -.2 -.3
Pc-ll +.4 -2.9 -4.6 -4.6 -4.8 -4.0
Vi-11 +.6 +.6 -.2 -0.0 -.1 -.4
B-11 -.2 -1.0 -5.4 -3.3 -2.3 -.1
B-12 +.1 -1.4 -1.1 -2.1 -2.4 -2.3
B-13 +.7 -1.1 -.5 -.4 -.4 -.6
B-14 +.5 -1.5 -1.3 -1.4 -2.4 -2.0
B-21 +.5 -.4 ,-.4 -.3 -.2 -.6
D-ll +.7 +.1 .:....8 -.8 -1.0 -1.2
G-ll +.6 +.6 -.3 -.3 -2.3 -4.1
Mo-11 +.9 +.9 +.9 +.5 -.3 -1.2
Mo-21 +.9 +.9 +.9 +.6 -.1 -.8
Mo-22 +1.1 +1.0 +1.0 +.9 +.8 -0.0
Mo-31 +1.1 +.8 +.3 +.2 +0.0 -.3
+: expansion; -: contraction

580 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
constant for two hours.
The following determinations were
performed on the test pieces:
a) weight loss, referred to weight of
the piece dried at 1050 °C;
b) firing shrinkage, computed as the
volume change from oven dry (150
°C) to fired state and expressed as
percentage of fired volume. Volume
shrinkage was converted to linear
shrinkage using the tables given by
NORTON (1949). Volume measurements
were carried out by mercury
displacement;
c) water absorption capacity of test
pieces. Two measurements were
made: 1) after 24 hours soaking in
cold water and 2) after 2 hours soak-
.. - ---- -----ilig :tn-ooJ.Ting water; Ieavl:O.g the
pieces immersed in water during the
cooling. In both cases the weight increase
was recorded and expressed as
a percentage of the weight of fired
pieces previously dried at 105 °C;
d) crushing strength. Two cube faces
were smoothed~_on~a. car:borundum
plate and their surface calculated
from their sides, measured with a
caliper. Crushing strength tests were
carried out with a 10 ton hydraulic
press. The load was increased at a
rate of about 90 to 100 kg per cm 2
min and six replications were made
of each test.
Experimental results and discussion
The weight and dimensional
change on firing at several temperatures
are given in Tables 1 and 2. For
most samples, the weight loss increases
steadily from 700 oc up to
somewhere between 800 and 900 °C,
remaining constant beyond this
point. Samples containing gypsum
(J-21, J-41) show a secondary loss of
weight at about 1000 °C, due, prob-
30
""
y=5.15+0.43x
u
r=0.924
0
...,
0
0
2Sy·x ,.-
+'.
20 "'
Ul
Ul
0
10
...,
.

Firing Properties of Ceramic Clc£ys ... 581
ably, to the thermal decomposition of
CaS0 4 with the evolution of S02 •
The weight loss on firing is closely
.related to carbonate content. The regression
line (Fig. 1) shows a

582 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
particle size (61% clay). Curves of the
types 1, 2 and 3 correspond to calcareous
materials, and the shapes of
these curves are not easily related to
sample characteristics. The common
feature of these curves is that shrinkage
at low temperatures (between
700 and 900 °C) is related to carbonate
content, and, hence, must be due
to the volume changes that accompany
the decomposition of CaC03.
Thus, the transformation of CaC03
(molar volume 36.9) to CaO (molar
volume 16.78) implies a 54% reduction
in volume. Also, transformation
of calcite into wollastonite following
the equation:
CaC03 + SiOz ;;:::::: CaSi0 3 + C0 2
is accompanied by a 33% reduction
in volume. It must be noted that in
addition to the amount, the grain size
distribution of carbonates plays an
important role in determining the firing
shrinkage: the finer the size, the
more probable that carbonate decomposition
or transformation will
induce an overall shrinkage. This
might be the case for sample Pc-11,
extremely rich in fine grained carbonates,
which shows an exceedingly
high amount of sl)rinkage even at
low temperatures. Below certain
thresholc! values for grain size and
carbonate content, the decomposition
of carbonate, for steric reasons,
will induce an increase in porosity
rather than a reduction in volume, or
both processes at the same time.
Actually, in most calcareous samples
there are both an increase in water
absorption between 700 and 800 oc
and a volume reduction accompanying
the weight loss due to carbonate
decomposition.,~~-~-~,·-·--~--·
Figure 3 shows the relationship of
firing shrinkage between 700 and 900
oc with lime and clay content. The
correlation coefficient is higher for
clay content and a somewhat better
prediction is achieved when both
variables are summed together.
Generally, calcareous clays show a
lower firing shrinkage than non calcareous
clays, not greater than 2 per
cent, so that, for these materials,
dimensional changes will be not a
problem within the firing range.
Values for water absorption after
24 hours soaking in cold water are
given in Table 3 and those for 5 hours
soaking in boiling water, in Table 4.
The former are intended to be an expression
of the readily accessible
pore space, while the latter are a
measure of total open porosity. Non
readily accessible porosity (nearly
closed pores) is given by the difference
between these two values, and
provides free space for relieving
stresses produced on freezing, by
plastic extrusion of ice crystals into
the void pores. Hence durability, or
resistance to freezing, will increase
with the proportion of nearly closed
pores, and may be evaluated by the
expression
D = (B + CIB) 100
where D is durability, B is the water
absorption after 5 hours boiling and
C is the water absorption after 24
,hours of immersion in cold water.
Although not entirely reliable (:aUT­
TERWORTH, 1964), the· following

Firing Properties of CeraYIJ.ic_Clays ... 583
TABLE 3
Water absorption(%) of samples fired at several temperatures after 24 hours immersion in
cold water
Firing temperature oc
Sample 700 800 900 950 1000 1050
Ac-11 20.7 24.5 22.4 19.3 21.2 20.6
Ab-11 27.0 33.0 30.2 30.9 24.0 30.0
Ah-11 19.9 21.0 19.6 18.5 18.5 18.8 .
Ah-21 19.0 22.2 20.2 20.2 20.1 19.7
Ah-31 26.4 27.1 23.5 27.3 25.2 24.3.
Ah-32 23.3 23.9 23.0 21.1 22.6 20.3
Ah-33 19.0 22.8 20.3 19.5 20.3 19.0
Ah-41 21.6 24.1 22.7 21.8 21.2 18.5
Ah-42 . 22.0 20.8 21.9 16.8 19.5 19.6
Ah-51 24.8 28.6 26.0 26.3 26.0 25.6
Ah-52 21.7 23.8 19.7 20.2 19.1 18.0
J-11 19.3 20.2 18.5 17.6 18.5 19.8
J-12 22.4 22.6 20.7 18.6 17.7 18.2
J-21 20.5 24.8 18.9 18.4 21.6 20.8
J-31 19.6 20.3 18.3 17.3 18.6 16.4
J-41 18.8 22.2 20.0 18.8 19.0 17.7
J-51 19.7 22.9 19.6 21.7 20.4 19.6
J-52 20.0 24.2 19.6 18.8 19.6 19.5
J-53 19.4 23.8 21.1 21.9 19.3 21.4
J-54 27.3 28.7 28.6 29.3 29.0 28.8
J-55 20.4 20.4 18.9 17.7 19.4 18.8
Mn-11 21.7 23.7 23.2 18.2 19.3 20.9
Mn-21 23.3 28.6 26.6 27.5 23.7 25.7
Pi-ll 23.3 27.0,- 25.6 25.8 26.1 25.2
Pi-12 22.6 21.8 23.7 23.5 22.4 22.0
Pi-13 21.4 24.7 "- 22.8 21.7 22.1 21.2
Ch-ll 23.6 26.0 26.9 22.9 25.3 24.0
Ch-12 22.0 20.9 19.2 19.0 18.4 18.2
Ga-ll 18.0 20.5 19.6 18.3 19.1 17.4
Ga-21 21.3 25.8 20.1 22.9 22.2 21.2
Ma-ll 24.1 26.2 24.1 24.2 22.0 23.5
Ma-12 18.0 20.1 17.9 18.8 19.9 19.6
Ma-13 14.9 19.1 17.7 17.9 16.0 15.1
Ma-14 14.2 18.8 19.6 19.4 18.1 16.2
Pc-11 23.2 25.3 19.1 18.4 20.8 21.9
Vi-11 18.0 19.3 17.9 19.1 18.5 18.7
B-11 19.0 15.3 1.3 1.1 1.0 .9
B-12 23.7 21.4 18.6 18.9 18.8 19.4
B-13 26.7 27.9 27.2 24.0 26.2 26.1
B-14 22.2 24.6 22.0 21.6 20.0 22.4
B-21 22.8 26.0 25.7 25.4 25.2 23.9
D-ll 24.6 27.1 25.4 21.8 24.9 24.3
G-11 J5.7 17.0 14.7 14.3 10.4 6.0
Mo-ll 10.6 10.5 10.3 9.6 8.4 6.6
Mo-21 10.8 10.8 10.3 9.7 8.7 7.3
Mo-22 24.6 24.6 23.7 23.2 22.2 21.2
Mo-31 25.2 27.1 2_5.6 25.6 22.5 23.0
values are often used as a guide for
durability:
D < 75, high resistence to freezing;
D > 95, low resistence to freezing.
In the samples studied, curves for
water absorption (Fig. 2) show a
rather irregular pattern, due probably
to the lack of replication. Only

584 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
TABLE 4
Water absorption (%) of samples fired at several temperatures after 5 hours immersion in
boiling water
~-:--~---
Firing temperature oc
--~~-==-===-=~~~--~ .. ~. ~-~-·.
Sample 700 800
Ac-ll 21.2 24.5
Ab-ll 28.8 33.5
Ah-ll 20.8 22.5
Ah-21 19.2 22.1
Ah-31 27.9 29.4
Ah-32 23.8 24.4
Ah-33 19.5 23.2
Ah-41
Ah-42
23.6
23.1
27.0
22.0
Ah-51 27.0 30.8
Ah-52 22.1 24.1
J-ll 20.3 19.1
J-12 22.4 23.4
J-21 .

Firing Properties of Ceramic Clays ...
585
4
y = -0.043 + 0.059 X
r = 0.616
u
0
0
0
0'1
-o
c

586 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
samples there is an almost parallel
increase in both types of .water
absorption from 700°C up to 800-900
oc and, above this temperature, the
water absorption remains constant
or changes irregularly, but there also
is a clear divergence between both
absorption curves, which is evidence
of non readily accessible porosity.
This phenomenon does not exist in
lime free samples.
In any case, with the exception of a
few non calcareous samples the durability
index is almost always greater
than 95 or, even, 100, thus these
materials could be considered as non
durable. However, no cases of frost
____________ c:lamage ha ve_beenreportedin the re- .
gion, and the suitability of the above
mentioned critical values should be
questioned under the climatic conditions
of southern Spain.
The values for crushing strength of
some selected samples, fired at several
temperature-nrre givenYi1Taole · 5.
It must be pointed out that these
values are dependent on briquette
size and, therefore, are only valid for
comparative purposes within the
sample set. Almost all samples show
a steady increase in strength with firing
temperature, except for some
cases in which crushing strength stabilizes
above 900 °C. Crushing
strength depends closely upon clay
content (Fig. 4) probably because
clay sized material supplies the vitreous
cement and new high temperature
phases that hold solid particles
together. This dependence is lower at
1000 oc probably because of the additional
contribution of other grain size
separates to the formation of binding
agents.
Neither quartz content nor water
absorption (or porosity) are good pre-
TABLE 5
Crushing strength (kg/cm 2 ) of some selected samples fired at different temperatures. Mean
values of 5 replications
Sample 7oooc 800°C 900°C 1000°C
Ah-32 256 403 472 524
Ah-41 206 299 404 472
Ah-51 428 552 637 1142
J-12 377 536 732 769
J-21 262 372 343 337
J-51 365 497 641 654
J-53 532 548 937 956.
J-54 329 535 716 687
J-55 17 25 98 175
Mn-21 323 440 519 568
Pi-13 307 425 511 479
Ga-ll 322 443 541 486
Ma-12 464 599 625 752
Vi-11 385 480 549 608
Ba-ll 735 928 1232
D-11 263 447 603 893
G-11 313 334 472 816
Mo-21 181 254 344 447
Mo-41 110 205 240 418

-
Firing Properties of Ceramic Clays.:.
587
1000
1 ODD
500
500
.

- ----~- ---~----
588 E. Barahona, F. Hu(!rtas, A. Pozzuoli, J. Linares
100 Calcite 100
80 80
'""" .=-/\ ..
/ .
•
oo

Firing Properties of Ceramic Clays ... 589
and quantified by XRD. Quartz, mica
·and calcite were. detected as residual
phases. The neoformed phases detected.
were plagioclase, anhydrite,
hematite, gehlenite, wollastonite and
diopside. In addition, leucite, corundum,
andalusite and mullite were
found as minor, questionable, phases.
The evolution . of residual and
neoformed phases with firing temperature
is illustrated in Figs 5 and
6. Only general tendencies should be
taken into consideration and no
weight should be given to several
strange occurrences, such as the
irregular evolution pattern for quartz
in some samples, due probably to
faulty quantification. Based on these
results, the following qualitative
statements may be made:
- Samples rich in calcite, on firing,
yield gehlenite, wollastonite and
diopside.
- Samples rich in dolomite yield
the same minerals as obtained from
60
Diopside
+
Wollastonite
30
Diopside
o<
._,.
"'
N
10
o<
00
a:
N
40
800 1000
20
o<
>,M
.. 00
" .el
. ,5
20
·:;; ,; 10
Wall astonite
.----·-·--·
/,~.:::::::,. .. :>< •
,?:--· / --· 6.
800 1000
40
Plagioclase
30
Hematite
o< 20
0
"'
M
10
800 1000 Firing temperature (oc) 800 1000
Fig. 6- Evolution of high temperature phases with firing temperature for some selected samples.

590 E. Barahona, F. Huertas, A. Pozzuoli, J. Linares
the calCite rich samples plus diopside.
- The presence of albite in the
fired specimens should be related to
the presence of paragonite in the raw
materials.
'
-The absence of the above mentioned
phases and the presence of
sizeable amounts of hematite indicate
a carbonate free raw material.
The relative abundance of each
high temperature phase may be indicative
of the firing temperature:
-The presence of large amounts of
calcite indicates that the firing
temperature was probably under 800
oc.
--------------'fhepr:esence-Qf-abundantgehlenite
points to a firing temperature
probably over 800 °C.
- If mica is absent, the firing
temperature was probably above
1000 °C.
- The same is to be suspected if
diopside, wollastonite or plagioclase
are abundant.
The following multiple regression
equation:
Temp. oc = 675.71 - 0.92 phyllosilicates
+ 5.36 quartz +, 10.41 plagioc~ase
+ 1.21 (gehlenite + diopside +
wollastnnite)
allows the firing temperatures to be
obtained from the amounts of the
high temperature phases present as
determined by XRD, with a 95% confidence
limit of 67 oc for calcareous
samples. For XRD quantification the
foll?wing reflecting power factors
were used: phyllosilicates 0.1 for 4.45
A spacing, quartz 1.5 for 3.34 A spacing,
plagioclase, gehlertite, diopside
and wollastonite 1.0 for 3.18, 2.85,
2.99 and 9.97 A spacings, respectively.
In the case of lime free samples no
reliable equation for the prediction of
firing temperature was found.
The results may be useful for making
inferences about the raw material
composition and firing temperature
of ceramic fragments in archaeological
studies.
REFERENCES
BARAHONA E., HUERTAS F., Pozzuou A., LINARES J., 1982. Minera/ogia e genesi dei sedimenti del/a
provincia di Granada (Spagna). Miner. Petrogr. Acta 26, 61-99.
'
BARAHONA E., HUERTAS F., Pozzuou A., LINARES J ., 1983. Sul/a p/asticita dei sedimenti del/a provincia
di Granada (Spagna). Miner. Petrogr. Acta 27, 161-182.
BARAHONA E., HUERTAS F., POZZUOLI A., LINARES J., 1985. DryingProperties u( Ceramic Clays from
Granada Province, Spain. These Proceedings.
· BuTTERWORTH B., 1964: The recording, comparison and use of outdoor exposure test. Trans. Br.
Ceram. Soc. 63, 615-629.
KrEFER C., 1957. Proprietes dilatometriques des mineraux phylliteux entre 0 et 1.400 °C. Bull. Soc. fr.
Ceram.35, 95-114.
NoRRISH K., RAoosLovrcH E.W., 1957. Effect ofbiotite on the firing characteristics of certain weathered
schists. Clay Miner. Bull. 3 (18), 189-192.
NoRTON F.H., 1949. Refractories. McGraw-Hill, New York.

Miner. Petrogr. Acta
Vol. 29-A, pp. 59!-598 (1985)
Degradation of Ceramic Sculptures on the
Cathedral of Seville
C. MAQUEDA 1 , J.L. PEREZ RODRIGUEV, A. JUSTO ERBEZ 2
1 Centro de Edafologia y Biologia Aplicada del Cuarto, C.S.I.C., Apartado 1052, 41080 Sevilla, Espaiia
2 Departamento de Quimica Inorganica y Fisico-Quimica, Facultad de Farmacia, Universidad de Sevilla, Apartado
874, 41012 Sevilla, Espaiia
'
ABSTRACT - The alteration of the statues adorning the Baptism and Birth
Porticos of the Cathedral of Seville (Spain) made by Lorenzo Merc?dante was
studied.
The statues are covered by dust which contains organic matter, nitrogen
(organic and ammoniacal) and phosphorus coming from animal excrements
and other environmental contamination. The lead content, caused by petrol
combustion is very high (0.38%).
The study of the ceramics shows sulphur contents changing from 0.81% in
the altered ceramic to 0.26% in the unaltered parts.
Some zones of the surface have a reddish colour and a similar composition to
the ceramic, but with a higher iron content. Accumulation of iron oxides on
the surface comes from release of this element from the ceramic and ulterior
precipitation.
The environment.provides SOz, SH 2 , C0 2 , Pb, nitrogen compounds, humidity,
mechanical erosion, etc., and also salts (external and from the ceramic),
that cause considerable alteration of these ceramic sculptures.
Introduction
The degree and causes of alteration
of materials employed in building
and ornamentatjon of monuments is
very important from the viewpoint of
its conservation (MARIJNISSEN,
1967; ROSSI-MANARESI, 1976). The
alteration produced in urban buildings
because of their exposure to the
atmosphere is essentially mechanical
and chemical. WINKLER (1966;
1973) and INIGUEZ-HERRERO
(1967) have pointed out the different
.J
causes of decay of stones used for
building.
In the Seville Cathedral there are
two Porticos decorated by Mercadante
between 1453 and 1467. Each
one of these porticos displays on its
jambs six statues made of terra cotta.
In a previous paper, PEREZ-RO­
DRIGUEZ et al. (1985) have studied
the materials and techniques used
to make the statues. In the manufacture
of this ceramic two different firing
temperatures were used (below
950 cc and over 950 cC) and the possi-

592 C. Maqueda, J.L., Perez Rodriguez, A. Justo Erbez
Fig. 1 - Baptism Portico of the Cathedral of Seville.

Degradation of Ceramic Sculptures ... 593
Fig. 2 - Birth Portico of the Cathedral of Seville.

594 C. Maqueda, J.L., Perez Rodriguez, A. Justo Erbez
ble material employed was a blue
marl consisting of illite, smectite,
kaolinite, quartz, feldspars, calcite
and iron oxide.
The deteriorating quality of the
urban atmosphere of Seville (FER­
RAND et al., 1969; 1975; REPETTO
& MENENDEZ, 1971), has greatly
accelerated the decay of these ceramic
statues. In regard to the great
value of this artistic monument, the ·
present work was undertaken to
study the causes and degree of alteration
supported by this ceramic.
Materials and methods
The Baptism and Birth Porticos
are shown in Fig. 1 and Fig. 2, respectively.
Samples of the dust that cover the
statues, dust from accumulation
zones, original unaltered ceramic,
ceramic with different degrees of alteration,
and rock surrounding the
statues, were taken.
Chemical analysis. The determination
of Si, AI, Fe, Ti, Ca, Mg~ Mn and
Ph was made following the method
proposed for the dissolution of silicates
by BENNET et al. (1962), with
the concentration of the elements
being determined by atomic absorption
spectrometry.
X-ray diffraction. XRD diagrams
were obtained with a Siemens Unit,
using Ni-filtered CuKa radiation and
a scanning speed of 1 o 28 per minute
(BRINDLEY & BROWN, 1980).
Thermal analysis. Differential thermal
and thermogravimetric analyses
were carried out using a Rigaku Unit,
operating at a heating rate of 15°C per
minute{MACKENZIE,l9'JO).~·····
Infrared analysis. IR spectra were
recorded from 400 to 4000 cm -l, using
a Perkin Elmer model377 double
beam spectrophotometer after sample
preparation utilizing the KBr
disk-technique (FARMER, 1974).
Sulphur analysis. The sulphur content
was determined in a Leco set
model 522 by formation of so2 in an
induction furnace and subsequent
titration with potassium iodate.
Carbon analysis. The concentration
of carbon was obtained by oxidation
-of organic matter with potassium
dichromate.
Nitrogen analysis. Total nitrogen
was determined following the Kjeldahl
method. The nitrogen from nitrates
and nitrites was determined by
fixation with salicylic acid and reduction
with sodium thiosulphate,
and ulterior titration in a Kjeldahl
apparatus (NEHRING, 1960).
Phosphorus analysis. The analyses
for phosphorus were performed
according to the method of MURPHY
& RILEY (1962).
Results and discussion
In order to obtain a better understanding
of the nature of the alteration
of these sculptures, the compositions
of the different layers observed
from the external to internal part of
the ceramic were studied.
The most external part of the statues
is covered by dust that contains
gypsum, calcite and quartz, as is
shown by the X-ray diagram (Fig.
3a).

Degradation of Ceramic Sculptures ... 595
Fig. 3- X-ray diffraction patterns of the dust covering the statues (a) and that found in accumulation
zones (b). Gy: gypsum; Q: quartz; Cal: calcite; M: mica; F: feldspar.
The dust accumulated in '-some
zones of the statues (Fig. 3b) has a
·higher proportion of quartz, mica
and feldspar and a lower proportion
of gypsum in relation to ~he dust
from the most external part. The difference
between the two samples
may be due to the coarser grains
coming from external contributions,
and the altered ceramic that remains
in the accumulation zones.
The chemical analysis of the dust
(Table 1) shows a high content in
organic matter, nitrogen (organic
and ammoniacal) and phosphorus,
coming from animal excrements and
other environmental contamination.
The high lead content (0.38%) can
only be produced by petrol combustion.
The high suplhur content
agrees with X-ray diffraction diagrams
that show gypsum in its composition,
probably arising from external
contributions and alteration of
the ceramic by the S0 2 in the atmosphere.
TABLE 1
Chemical analysis of dust that cover the statues(%)
Nitrogen
Nitrates
Organic matter
Carbon
Sulphur
Phosphorus
Lead
0.59
0.00
7.50
4.40
0.85
0.49
0.38

596 C. Maqueda, J:L., Perez Rodriguez, A. Justo Erbez
All this suggests the existence of
acid pH and salts that alter the
ceramic material.
In some altered parts, the dust
mixed with the remainder of the
ceramic forms a hard crust, whose
composition is intermediate between
the dust and the ceramic.
The X-ray diffraction study shows
that the proportion of gypsum, calcium
carbonate and other components
found in the dust decreases
from the external to internal part of
the ceramic.
The proportion of sulphur in the
ceramic changes from 0.81% in the
external part (altered ceramic) to
0.26% in the internal part (un-
- ------------~-- alrered). The presence- of ·a ·substantial
proportion of sulphur in the internal
part is very significant from
the point of view of the alteration.
100 200 300 400 500 600 700 800 900 1000
Fig. 4 _ Gravimetric and thermal analysis
curves of a sample of altered ceramic.
The gravimetric and differential
thermal analysis curves of altered
ceramic (Fig:4)igre~- withtbe X-ray
diffraction diagrams. The thermal
curve shows an endothermic effect at ·
158 oc and also a weight loss caused
by dehydration of gypsum. At 335 oc
there is a broad exothermic effect and
a weight loss indicative principally of
organic components and gels of iron,
originating from environmental contamination
and alteration of the
ceramic, respectively. Endothermic
effects at 573 oc and 780 oc are due to
the a-~
quartz transformation and
the decomposition of calcium carbonate,
respectively. The endothermic
effect at 890 oc is due to the dehydroxylation
of smectite, illite and
kaolinite only partially decomposed
in the original ceramic, while the exothermic
effect at 920 oc is due to
the recrystallization to wollastonite,
kilchoanite and anorthite. The reason.
for the two last effects is that the
altered ceramic was fired at a
temperature below 950 oc (PEREZ­
RODRIGUEZ et al., 1985).
Some zones of the surface of the
statues have a reddish colour. The
chemical analysis data for Fe, Ca and
Mn from the reddish patina and the
most internal part of the same ceramic
are shown in Table 2. The iron
and manganese contents are higher
on the surface, probably due to a release
of these elements from the ceramic
and ulterior precipitation,
producing the reddish colour.
The rocks that surround the ceramic
statues may also influence the al-
teration process. The petrographic

Degradation of Ceramic Sculptures ... 597
TABLE 2
Chemical analysis of Fe 2 0 3 , CaO and Mn from the external and internal part
reddish part
external
internal
part
Fe203 6.33% 4.95%
CaO 19.86% 14.12%
Mn 573 ppm 450 ppm
a~d X-ray diffraction studies show
that this rock is a calcareous sandstone
consisting of calcite, quartz and
feldspar. This material is easily
altered, loosing the cementating
components and yielding gypsum.
These components are deposited on
the statues and have influenced their
alteration, because of an extra contribution
of salts.
The experimental results suggest
the following causes of altera.tion:
1. The environment provides 'S02,
SH2, C02, Pb, nitrogen compounds,
animal excrements, salts (external
and from the ceramic), humidity,
mechanical erosion, etc., that cause a
high alteration of these ceramic
· sculptures.
2. The S02 .in the atmosphere originates
from contamination (petrol
combustion from cars and from industry).
It has been shown ex-
. perimentally (FUZZ! & VITTORI,
1976) that a high transformation of
so2 to so3 can happen in urban.
atmospheres when NH 3 is present. In
the ceramics of the Seville Cathedral
there is a high proportion of ammoniacal
nitrogen and also Pb, which
can catalyze the formation of sulphuric
acid. This acid may produce
gypsum by reaction with the calcium
carbonate or other calcium bearing
minerals of the ceramic.
3. The recarbonation of smali ~alcium
oxide nodules formed during
the manufacture of the ceramic, as
has been shown in a previous paper
(PEREZ-RODRIGUEZ et al., 1985),
may produce strain, but does not
cause any visible cracks in the ceramic.
These nodules and the calcium
carbonate from external contamination
react with the environmental
C02 yielding calcium bicarbonate
that produces movement of salts
through the ceramic, thus contributing
to its alteration.
4. The proportion of sulphate and
carbonate found is very high in relation
to the content of CaO initially
present in the ceramic, and thus,
there must be contributions from the
Seville atmosphere and from the alteration
of the rock that surrounds
the sculptures.
5. Salts, and especially the influence
of atmospheric agents in some
zones of the ceramic, produce the liberation
and migration of iron and
manganese from the interior to the
surface with subsequent precipitation
on it, produ~ing a red patina.

598
C. Maqueda, J.L., Perez Rodfiguez, A. Justo Erbez
REFERENCES
BENNET H., EARDLEY R.P., HAWLEY W.G., THWAITES !., I 962. Routine control analysis of high-silica
and aluminosilicate materials. Trans. Br. Ceram. Soc. 61, 636-666.
BRINDLEY G.W., BROWN G. (editors), 1980. Crystal Structures of Clay Minerals and their X-ray Identification.
Mineralogical Society, London.
FARMER V.C. (editor), 1974. The Infrared Spectra of Minerals. Mineralogical Society, London.
FERRAND C., REPETTO M., BtASCO P., MENENDEZ M., ALVAREZ-DARDET A., I969. La contaminaci6n
atmosferica en Sevilla. Rev. Sanidad e Higiene Publica XLIII, 72I-748.
FERRAND C., BtASCO P., KUHN A., REPETTO M., LAZARO J., GARC!A-SERNA D., 1975. La COntaminaci6n
atmosferica en Sevilla. Rev. Sanidad e Higiene Publica XLIX, 14I-I58.
Fuzzr S ., VITTORI 0 ., I 976. Climatic chamber for laboratory experiments on the system S02-wet marble.
Airborne particles. Pp. 65I-66I, in: Proc. Int. Symposium «The Conservation of Stone>> I 975,
Bologna- Italy, Centra per la Conservazione delle Sculture all'Aperto, Bologna, Italy.
I!ir!GUEZ-HERRERO Paris. J., I967. Alteration des calcaires et des gres utilises dans la construction. Eyrolles,
MAcKENZIE R.C. (edjtor), 1970. Differential Thermal Analysis. Academic Press, London.
MARIJNISSEN R.H., 1967. Degradation, conservation et restauration de l'oeuvre d'art. Arcade,
Bruxelles.
MURPHY J., RILEY J .P., 1962. A modified single solution method for the determination of phosphate in
natural water. Anal. Chiin. Acta 27, 3I-36.
NEHRING K., 1960. Agrikulturchemische Untersuchungs-methoden fur Dii.ge- und Futtermittel, Boden
und Milch: Bestimmung des Gesamt-stikstoffs, methode van 0. Foerster. Verlag Paul Parey,
Hamburg.
PEREZ-RODRIGUEZ J.L., MAQUEDA C., JusTo A., 1985.Scientific study of the sculptures from the Baptism
and Birth Porticos of Seville Cathedral. Studies in Censervation 30, 3I-38 .
. ____ REPETTO-M.,-MENENDEz· M.,· 197L La poluci6n atmosferica en Sevilla, 1970-71. Rev. Sanidad e
Higiene PUblica XLV, 921-954.
Rossr-MANARESI R. (editor), 1976. The Conservation of Stone. Centra per la Conservazione delle
Sculture all'Aperto, Bologna, Italy.
WINKLER E.M., I 966. Important agents of weathering for building and monumental stone. Eng. Geol. 1
(5), 38I-400.
WINKLER E.M., I973. Salt action in urban buildings. Pp. 139,I49, in: Proc. Sem. «Application of
Science in Examination of Works of Art>> 1970, Boston (W.J. Young, editor), Museum of Fine
Arts, Boston.

Abstracts . 599
Kaolin and Sericite Clays from SW Spain: Particle Size
Distribution, Mineralogical and Ceramic Study
F. GONZALEZ-GARCIA, G. GARCIA-RAMOS, J.M. MESA, M.T. RUIZ-ABRIO,
P.J. SANCHEZ-SOTO
Departamento de Quimica Inorganica, Facultad de Quimica and Departamento de Investigaciones Fisicas y
Quimicas, Centra Coordinado del C.S.I.C., Universidad de Sevilla, C/Tramontana, 41012 Sevilla, Espafla
Nine samples of natural clays with high aluminium contents, from different
southwestern Spanish deposits, mainly used in the ceramic industry were
studied.
The deposits from Sta. Eufemia (Cordoba) and Garlitos (Badajoz) are formed
by ampelitic Ordovician-Silurian materials, while the ones from Zalamea
and Monterrubio de la Serena (Badajoz), which have similar characteristics,
are Lower-Pevonian in age. However, all the deposits show a very low-grade
metamorphism, and there are some break networks formed by the Hercynian
Orogeny which enabled the fluids to flow.
The Carboniferous deposits of the Province of Sevi!la belong to coal exploita-.
tions. The Villanueva del Rio y Minas deposit is of pre-Orogenic Westphalian
origin; the one from Guadalcanal is also of post-Orogenic Westephanian
origin.
The Conquista (Cordoba) bed belongs to an old alluvial deposit which developed
over the granitic batholith of Los Pedroches. The Cazalla de la Sierra
(Sevilla) bed is placed on the southern edge of a syenitic intrusion, weathered
in a supergenic-like way. The Zalamea la Real (Huelva) deposit is formed
by acid volcanic materials belonging to the SW Iberian pyritic belt.
With reference to the ceramic industry applications of high temperatures
(stoneware, feldspathic tableware, porcelain and refractories), the particle
size distribution, mineralogy and sintering temperatures are studied.
According to the particle size analysis, three groups of materials are differentiated:
with 80%, 25% or 10% particle size smaller than 63 J.Lm. The samples,
according to the mineralogical data, excepting the feldspathic one ·of magmatic
origin, are defined as kaolinitiC and illitic-kaolinitic (sericites) types.
There is also, among the latter ones, a sample with 25% pyrophyllite and 5%
carbo~ates. The < 63 J.Lm fraction is richer in .kaolin minerals and generally
has a greater content in AlzOJ.
Sintering temperature diagrams to 1450°C show that a great part of these
materials could be used as silica aluminous refractories, after the concentration
process. The feldspathic sample is appropriate for feldspar earthenware,
or as a raw material in vitrous ceramic ware.
Natural clays studied
Origin
Sample

,---r-~--=-----~~-~-==-e

Abstracts 601
and Middle Age times, have been investigated by X-ray diffractometry,
scanning electron microscopy (SEM) and· thin sections under the polarizing
microscope.
Clays constituting the ceramic-pottery matrix were of different
(particle size and distribution) and composition; although, in certain
samples the original mineralogy has been deeply modified by firing techniques
and temperatures, rendering inconsistent any indications regarding
origin.
Some primitive firing equipment did not exceed 500°C, quartz and cristobalite
indicate a firing range of 600-700°C, the presence of gehlenite may
indicate temperatures between 700-850°C (but it may be decomposed over
900-950°C), diopside was formed at 850°C. The presence of fine calcite and
reducing-oxidizing atmospheres (magnetite: hematite ratio) may shift the
temperature of formation of the new phases.
The ratio between clayey matrix and chamotte grains is widely variable;
different materials (limestone, diorite, granite, gneiss, mica-schist) were
used as chamotte, reflecting the materials available locally. Manufacts with
sandy-quartz chamotte are considered imported from African Mediterranean
countries. Porous, void filled, isoriented, welded, vitrified, etc. textures
and fabrics of the ground-mass, reaction rims around quartz, feldspar, mica,
calcite grains, as observed by SEM, are discussed as being representive of
manufacturing techniques and firing reactions.
Raw Materials and Technological Data of Ancient
Ceramic Piece's of the Archaeological
Bed of Cerro Macareno, Seville
M.C. GONZALEZ VILCHES, G. GARCIA-RAMOS, F. GONZALEZ-GARCIA
Departament.o de Quimica Inorganica y Fisico-Quimica, Facultad de Farmacia, Universidad de Sevilla, Apdo. 874,
41012 ,Sevilla, Espafla
A group of ceramic materials from the archaeological bed of Cerro Macareno
(Seville, N-NE, 7 Km from the city on the Guadalquivir riverside),' was
studied.
Forty four samples, from 28 amphora fragments used by ancients in the
Mediterranean countries, were investigated with the aim of determining the
provenance of the raw materials and the technology used in the fabrication
of the amphoras.
The study carried out consisted mainly of chemical analysis, X-ray diffraction
and heating of the fragments to 1100°C, with observation of the colour
changes that take place in the freshly cut surface. In some cases an X-ray
diffraction study on the transformations induced during the heating was also
undertaken. The results provide useful information not only on the type of
materials employed but also on the temperatures and conditions of the
original firing process.
Thus, it can be concluded that all the samples contain important amounts of
calcite and quartz, and that a number of them also contain dolomite, plagioclase,
potassium feldspars and small amounts of illite and kaolinite.
Certain reactions occur upon heating the samples from 700 to ll00°C in a

602 Abstracts
muffle furnace: disapP,earance of calcite and dolomite and also of illite and
kaolinite, a decrease in the percentage of quartz, disappearance of the potassium
feldspars between 700 and 900~C,_fpJ:1I!~t_iQJl_q_f__}VSJJlastoni!e,e!c ..... _
These data and the colour changes observed upon heating indicate that 8 of
the samples investigated were fired at temperatures lower than 700°C, 13
between 700 and 750°C and 7 samples at 800°C or slightly higher.
In addition, it is possible to conclude that with the exception of four
pieces imported from Palestine-Phoenicia, the remaining were made with
raw materials from the Cerro Macareno area.
Red Bed Clays: Fundamental Raw Materials for Fast
Single Firing of Ceramic Floor and Wall Tile
--- ------ -A~ TENKGLIA- 1 ; V: VENTURF -
1
Centra Ceramico, Via Martelli 26, 40138 Bologna, ltalia
2 Geoceramic Researches, Via Bacchello 9, 40050 Monte San Pietro, Bologna, Italia
The recent technological innovations in manufacturing processes in the field
of ceramics have provided the incentive for studies and applied research in
the field of raw materials. In this respect, particular needs and requirements
have developed as a result of the especially large role which fast single firing
has begun to play (for both red and white ware bodies) at ·the expense of
double firing (also for both red and white ware bodies) and of slow single
firing. This trasformation is based on a radical modification of ceramic
manufacturing cycles. In addition to changes in firing methods, the shaping
operation (pressing) and especially grinding methods also have undergone
profound modifications.
In the case of single fired white ware bodies, wet grinding of the raw materials
followed by spray drying is indispensable. This leads to the problem of
cost of the operation from the energy point of view. Also, the raw materials
used, in particular the clays, must be imported. This too leads to higher
overall cost of the final product.
With respect to single fired red ware, initially, the clays being used are those
which already.have been employed for some time for production of red gres
(stoneware), typical traditional Italian ceramic products. These clays are
national raw materials which can be grouped together under the common
denomination of «red bed» clays. They include clays of various geological
formation, in general during the Oligocene and in some cases, also during the
Eocene.
With the advent of fast firing cycles, materials preparation by wet grinding
became more common, resulting in increased energy comsumption. Presently,
however,. there seems to be a move towards the return to dry grinding.
This tendency has stimulated studies of both clay and non-clay raw materials
directed towards obtaining a better understanding of the characteristics
of particular importance from the applications point of view.
The present study reviews a wide range of red clays presently used for _fast
single firing. Chemical-mineralogical data and physico-ceramic data are

Abstracts 603
given for each clay studied. An examination of the data allows relationships
to be established between the type of raw material and its behaviour during
the industrial manufacturing cycles. The presentation of the data in appropriate
diagrams allows the suitability of the clays for use with the new
technologies to be determined, a priori, on the basis of certain chemicalmineralogical
data.
Analogous data are given for the non-clay raw materials (sand, basalts,
volcanic rocks) used in the mixtures as structural components. Their
function is to consent the use of local rather than imported clays and to allow
dry grinding or turbogranulation techniques to be employed, thus avoiding
the heavy energy consumption associated with wet grinding.
A Study of Eneolithic Ceramics from
La Pefia del Aguila, Avila, Spain
S. LdPEZ-PLAZA 1 , J. VICENTE-HERNANDEZ 2 , P. HERNANDEZ-HERNAN­
DEZ2, M.A. VICENTP
1
Departamento de Prehistoria, Facultad de Geografia e Historia, Universidad de Salamanca, 37019 Salamanca,
Espaiia ,-
2 Departamento de Quimica Analitica, Facultad de Ciencias, Universidad Aut6noma, Canto Blanco, 28049
Madrid, Espaiia
'·
3
Centro de Edafologia y Biologia Aplicada, C.S.I.C., Cordel de Merinas 40-52, Apd!'J. 257, 37008 Salamanca,
Espaiia
The settlement La Pefia del Aguila is situated on the plateau of a small hill
on the southern slope of the Avila mountain range, at about 18 km S.W.
of Avila in the township of Mufiogalindo. Its exact location is indicated by
the coordinates 1°12'21" longitude west and 4°36'21" latitude north at an
altitude of 1160 m above sea level, as per sheet 530 Vadil!o de la Sierra of the
map (1:50.000) of the Geographical and Statistical Institute.
The excavation made in this sett!ementrevealed the existence of three levels,
characterized initially by differences in soil colour. From the top to the
bottom the levels could be described as follows:
Level I. It is constituted by brown sandy soil and demonstrates a maximum
power of 48 cm;
Level II. It is formed by a blackish soil and lies immediately below level I
with a maximum power of 60 cm;
Level III. It is characterized by a fine ash-grey soil with a maximum power of
70 cm. The importance of this level lies in the presence of a large number of
circular or oval shapes excavated in the rock at the bottom.
Materials of archaeological interest found, show great homogeneity throughout
the period of existence of this settlement. Besides, they also indicate a
slow evolution and could be dated to the Regional.Eneolithic beginning
about 2500 B.C. Levels II and III, which could be Classified under the prebeaker
period, show neolithic traditions of «Cave Culture>>. These levels
could be linked to the Eneolithic settlements of the Portuguese Extremadura,
based on certain other proved characteristics identified by the ceramic
industry. The presence of a small frag~ent of a bell beaker in level I indicates
the contact of this settlement with the Ciempozuelos beaker.

604 Abstracts
Adopting the techniques of Arc-emission Spectroscopy, XRD and DTA, 8
ceramic samples, three from level Ill (samples 1, 4 and 6), four from level II
(samples 2, 3, 5, 7) and one pertaining-to a-type-of-painted-ceramic:-, collected
from the top layer, but known to occur in all the levels,- were studied.
Certain samples demostrate a black interior and an aspect totally different
from the exterior. Both parts were studied separetely and a sample, when
subjected to a temperature of 500°C under oxidizing conditions, acquired a
uniform brick-red.color.
All the ceramic samples had similar chemical compositions. Si, Fe, Mg, Na,
Ca and Al occur in higher proportions while K, Ti and Mn in lower proportions.
Cr and Cu occur only in trace quantities. The surface layer is quantitatively
similar, although with a lower proportion of Si. In all DTA curves, the
thermal inversion of quartz could be seen at 573°C and also certain small
effects owing to the presenceof different oxides.· Samples 1, 3, 6 and 8, all
black in colour, produce a large exothermic effect, indicating the presence of
considerable organic matter in them. X-ray diffractograms show diffraction
effects at: 9.90-9.40 and 3.36-3.18 A due to micas and/or collapsed smectites;
4.23-4.04, 3.83-3.62 and 3.26-3.15 A due to feldspars; 3.24 due to quartz, and
other effects due to Al and Fe oxides. Sample number 1 is the only one
demonstrating effects due to kaolinite.
It could therefore be concluded that ceramic samples obtained from different
levels were made using similar materials and the polished surfaces
made using the finest fraction of the same materiaL All of them were heated
to temperatures less than 500°C and the black samples made under reducing
conditions.
Mineralogy of Ceramic Clays from
the Sagra Area, Central Spain
B.GALVANMARTINEZ,C.RODRIGUEZPASCUAL,J.M.GONZALEZPENA',
J. GALV AN GARCIA
Institute de Edafelegia y Bielegia Vegetal, C.S.I.C., Serrane !IS - dpde., 28006 Madrid, Espafla
1
Institute de Ceramica y Vidrie, Arganda del Rey - Madrid, Espafla
The tectonic trough of the Tagus river was filled during the Tertiary with
materials from the Central and the Iberian Ranges, and the Toledo Mountains.
·
Those materials are made up of a detrital facies which change~ gradually to
evaporitic facies towards the center of the Tagus basin.
The area of interest corresponds to Miocene materials, such as clays, marls,
gypsiferous marls, gyp~um, limestones, sands, etc.
This paper concerns the Miocene clays which have a wide distribution in the
Tagus basin.
The area of study is limited to the following localities: Illescas, Yuncos,
Pantoja and Alameda of the Sagra. The clays present a high degree of purity,
and are progressively enriched in a detrital fn,.ction which becomes coarser
to the west.
Those clays are used in the ceramic industry, mainly for the manufacture of
bricks, roofingtiles and small vaults. .
Sixteen samples were investigated by the following physical-chemical

Abstracts 605.
techniques: X-ray diffraction, transmission electron microscopy, infrared
absorption spectroscopy and thermal methods. A semi-quantitative analysis
was carried out on the < 2 mm fraction. The estimated amounts of minerals
were the following: layer and fibrous silicate species (85-55%), quartz (27-
10%) and feldspars (22-2%). Calcite and dolomite occur occasionally, but
always in small amounts. The mineralogy of the clay fraction ( < 2 11m size) of
the Miocene sediments, from the de Sagra area, is usually dominated by
degraded mica (illite), and smectite with lesser amounts of chlorite and :
kaolinite. Almost all samples contain sepiolite. Appreciable amounts of palygorskite,
vesy_well_ crystallized with long fibres, were also found in two .
samples. Primary minerals, such as, quartz, feldspar, calcite and dolomite ·
were still present in the clay fraction, but always in small quantities. The
presence of kaolinite in this area is of great mineralogical interest. A granulometric
analysis was performed and the position of samples on Casagrande's
diagram was obtained in order to know the exploitation possibilities by the
ceramic industries.
Alonso J.J., Garcia V.S., Riba 0., 1961. Sedimentos finos del centro de la cuenca terciaria del Tajo.
Aetas 2" Reun. Gr. esp. Sediment. C.S.I.C., 21-55, Madrid.
Huertas F., Linares J., Martin Vivaldi J.L., 1971. Minerales fibrosos de la arcH!a en cuencas ·
sedimentarias espaiiolas. I. Cuenca del Tajo. Eo/. Inst. Geo/. Min. t-82, Fasc. 6, 534-542, Madrid.
I.G .M.E. 197 4. Map a de Roe-as .Industriales. Escala 1 :200.000 Hoja y Memoria, n. 45-5/6, Madrid.
I.G.M.E. 1974. Mapa de Rocas Industriales. Escala 1:200.000 Hoja y Memoria, n. 53-5/7, Toledo.

Section VI
Geotechnical Properties and Applications

Miner. Petrogr. Acta
Vol. 29-A, pp. 609-619 (1985)
Mineralogical Composition and Geotechnical Properties
of the Pelitic Antognola: Formation from
the Baiso Area, Northern Apennines
A. CANCELLJI, A. FAILLA 2 , N. MORANDF
1
Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano,
Italia
2 Istituto di Mineralogia e Petrografia, Universita di Bologna, Piazza di Porta S. Donato 1, 40127 Bologna, Itali~
ABSTRACT- A pelitic portion of the Antognola Formation from the Baiso area
(northern Apennines, Italy) is considered. Mineralogical analyses (non-clay
to clay ratio and clay mineral content) and geotechnical tests (shear strength
parameters and swelling characteristics) are reported and correlated with
each other. These analyses put in evidence a wide spectrum of geotechnical
properties, in accordance with the mineralogical composition.
Introduction
This study takes into consideration
the correlation between geotechnical
behaviour and mineralogical composition
of the pelitic Antognola
Formation (northern A,pennines, Italy).
The opportunity for this research
work was gi:ven by the engineering
geological study (being carried out
by two of the Authors, A.C. and A.F.)
of an extended landslide, which involved
and goes on involving the
Antognola Formation in the Baiso
area (Province of Reggio Emilia;
locality about 1 km south of Costetto;
Carta Tecnica Regionale no.
218124-BAISO). The main mass.
movement can be classified as an
«earth block slide», the foot pf which
gives origin to two earthflows (Fig.l).
The Antognola Formation
The Antognola Formation belongs
to the Oligomiocenic «Complessi
Emiliani», outcropping as floating
. plates on the allochthonous substra­
\ turn (ROVER!, 1966), and characterized
by semiautochthony, because
they took part only in the last phases
of the Ligurian nappe translation
This research work has been carried out within the program and with the financial support of
C.N.R. and M.P.I.

610 A. Ca!'!celli, A. Failla, N. Morandi
0 100 200 300 m
2
~ V777l
~~
5 6
~
3 4
7 8
• *
Fig. 1 ~ Schematic map of the area studied and position of samples. 1: Antognola Formation;
2: «Complessi liguri>>; 3: Earthflow; 4: Fault; 5: Main scarp; 6: Movement direction; 7: Sample;
8: Position« 1».
(DALLAN NARDI & NARDI, 1975):
This Formation is mainly composed
of a pelitic portion (marls, clay
marls, sometimes clays), interbedded
with rare and thin sand layers.
This pelite shows homogeneous and
typical features, such as dark greengreyish
colour, frequent manganese
coats and a characteristic conchoidal
fracturing.
A mineralogical and petrographic
study of the pelitic portion of the
Antognola Formation was published
recently for the Vetto-Carpineti Syncline
(BOLZAN et al., 1983). This research
shows a homogeneous clay
mineral composition of the fine fraction:
smectite/illite ratio close to
unity, serpentine always present
and often prevailing on chlorit~, and
kaolinite always scarce or absent:

Mineralogical Composition and Geotechnical Properties ... 611
Samples and methods
For engineering geological investigations,
the sampling (Fig. 1) of the
Antognola Formation was made in the
crown area (samples no. 2, 3, 4, 5, 6,
7, 8) and near the toe (sample no. 9) of
the landslide, and in a quarry next to
the eastern flank of the landslide
(sample no. 10 and several samples
from position 1).
All the samples showed the typical
macroscopic characteristics . of the
pelitic Antognola Formation (as mentioned
before), except for sample 10
an~ samples collected from position
1, which are less compact, less
cemented and more clayey than the
others.
The semiquantitative analyses of
clay minerals were made according
to the methods proposed by JOHNS
et al. (1954), BISCAYE (1965) and
MEZZETTI et al. (1980). The quartz
and feldspar contents were determined
by XRD analysis, as suggested
by BOCCHI et al. (1982).
Results·
The result.s of mineralogical analyses
carried out on all samples are
shown in Table 1.
The samples collected in the landslide
area (no. 2 to 9) have a CaC0 3
content variable from ll%o to 19%
(except for one sample with 25%);
therefore they are classified as marly
clays. Their most abundant clay components
are illite and smectite, with a
ratio generally close to unity; chlorite
and kaolinite are present as minor
components, with the former prevailing
over the latter; serpentine content
is around 10%.
This composition is very similar to
that found in a great number of.
«Antognola Marls» samples from
other areas of the northern Apennines
(MEZZETTI et al., 1980; BOLZAN et
al., 1983), where serpentin_e is considered
the characterizing mineral of
the Antognola Formation.
The samples collected from position
1 in the quarry adjacent to the
TABLE 1
Clay minerals content (to 100%) of fine fractions of pelites from the Baiso area
sample illite smectite serpentine chlorite kaolinite CaC0 3 *
2 34 42 11 7 6 16
3 '35 46 8 7 4 16
4 33 40 12 8 7 15
6 so 35 6 6 tr 17
7. 46 43 \5 4 tr 11
8 41 43 7 6 tr 18
9 51 31 7 8 tr 25
10 38 25 16 21 tr
1** 47 18 15 21
* The CaC0 3 content is referred to whole samples
·** Mean composition of samples from position 1
tr, traces.

-------------------
612 A. Cancelli, A. Failla, N. Morandi
... ___ ~--·----~------------
landslide mass and sample no. 10
show some differences from the
others: illite is the most abundant
mineral; smectite, serpentine and
chlorite are present with equivalent
amounts, while kaolinite is absent.
The low content of smectite,
together with the absence of CaC03,
justifies the exc.avation of this material
for ceramic uses.
However, even if such a composition
does not correspond exactly to
that typical of ~

Mineralogical Composition and Geoteclinical Properties ... 613
tics of the fraction passing an ASTM
no. 40 sieve, all points fall into the
field of (see Casagrande's
plasticity chart in Fig. 3-
right).
However, the degree of diagenesis,
acting as a cementing agent, recommends
the use of non-standard proce-
. dures for sample preparation, in order
to favour a better disaggregation of
the solid particles forming the clastic
fraction; several procedures were
suggested for the Italian clay f?rmations
(see e.g. RIPPA & PICARELLI,
1977; JAPPELLI et al., 1977).
For this study the following procedures
were adopted. The sample was
dried at 40 oc and subsequently
crushed by means of l)l rubber pestle;
then it was soaked in water and
dried again at 40 °C. A sequence of 10
alternate, drying and wettin'g c:ycles
was. applied. Then new granulometrical
and plasticity analyses
were carried out, and the values, represented
by full dots in Figs 2 and 3,
were obtained. The difference is out-
60
lp(% )
40
20
~ Active
"~ormal ~
~
I~
""'
. '\
~ .... '\.
Inactive ~ ,'\ ~
60 (%) CF 40
20
I
I
i~L
I
I
lJ
standing, both in terms of granulometrical
classification and in terms
of plasticity.
The activity index la, defined as the
ratio of plasticity index lp to the per
cent of particles finer than 0.002 mm
CF (SKEMPTON, 1953), is about 0.8,
depending on the prevalence of inactive
minerals (illite, serpentine, chlorite)
in the clay fraction (GRIM,
1962); the method of sample preparation.
does not alter the value of la
(Fig. 3-left).
The high degree of compactness is
marked by the low values of the
porosity n and the void ratio e (the
mean values are, respectively, fi =
16% and e = 0.19). Accordingly,
though the degree of saturation Sr is
always higher than 0.9 and often
close to unity, the natural water
content W 0 is only 7.0% and the unit
weighty reaches 24.5 kN/m 3 •
Such a compactness is the result of
high compressive stresses. In fact,
from a conventional oedometer test
on the undisturbed speci~en ''-~»-.(~ee
V
0
• /
CL 0/
/
/
ML
OL
CH
V
/
MH
OH
/
..
/r
20 40 60 80 WL (%) 100
60
p(%)
40
20
· o standard method
• after drying and wetting ·cycles
Fig. 3 - Left: plasticity index Ip vs. clay fractio~ Cp; representation of the activity indexi:a
(SKEMPTON, 1953). Right: Casagrande's plasticity chart. All points represent specimens from
position « 1 ».

~--·- -
614 A. Cancelli, A. Failla, N. Morandi
Fig. 4), a maximum apparent preconsolidation
pressure p~ as high as 20
MPa can be evaluated, both by the
classical Casagrande's graphical construction
on the compression-log p
curve and by plotting the secondary
compression ratio Ca versus the vertical
pressure p (Fig. 4-b).
The «Marne di Antognola» Formation
is Oligo-Miocenic and the samples
examined belong to the Lower
Miocene; therefore, the maximum
thickness of covering formations can.
t _
.. _ _
15
.. r- ..
(%) ................
.. ..,
10
......_
~- -~ --· --
~:--:r-- ~----
"
..
0
5
"' ,..--o--·o
..
""'
r
0.
--- -.
f-b ~-::........ '?-
11 B ..
" I I I
~::£-.-i
"
0
"' ,_
"'
P.
E
0
u
5
..
be estimated as about 1000 m. Consequent!y_,~!!J:e~.
af~!:~!E:~!J:tio:~H~~~gigh
values of p~ seem to be due not only to
lithostatic pressure, but also to tectonic
stresses and/or to diagenetic
bonds.
To determine the swelling properties
of the rocks examined, three
specimens of pelite from the same
outcrop no. 1 were put into onedimensional
consolidometers; then:
- specimen A was subjected to a
routine compression test, no initial
--
- li"'

Mineralogical Composition and Geoteclinical Properties ... 615
TABLE 2
Geotechnical data
Sample/specimen no.
Swelling potential S (under Po = 7kPa)
Swelling pressure p~
Swelling index C.;
within the range 100 + 10 kPA
within the range 1000 + 100 kPa
Virgin compression index Cc
nor final expansion being. allowed
(Fig. 4-a);
- for specimens B and C, free initial
expansion under a vertical load p= 1
p.s.i. = 7 kPa was permitted, in order
to measure the swelling potential S
in the undisturbed state (CHEN,
1975); subsequently, compression
under vertical loads up to 15-20 MPa
(so measuring the swelling pressure
p~) and final swelling under p=7 kPa
were performed (Fig. 4-a).
All results of the geotechnicaL_analyses
are summarized in Table 2. The
swelling properties (namely s' p~, c.)
of specimen C are quite higher than
those of specimen B.
The different geotechnical behaviour
of specimens B and C, despite
the same location and the same
macroscopical appearance, could
only be due to differences of minelA
lB lC
(%) 4.2 14.0
(MPa) 1.8 2.2 6.0
(%) 2.4 6.0
(%) 2.4 3.8 5.5
(%) 9.2 9.6 9.0
ralogical composition. For this reason,
intensive mineralogical investigations
were carried out on samples
from position 1, and the range reported
in Table 3 was established.
It is important to remark that clay
fraction contents and smectite percents
are rather widely scattered and
vary in direct correlation. As a consequence,
the smectite content of the
whole sample can vary from 2.5% to
9% (ratio about 1 to 3); the extremes
of the range of values for the smectite.
content arerepresented by diffractograms
of glycolated material in Fig.
5. The same ratio (about 1 to 3) was
found for the geotechnical parameters
determined on specimens 1B
and 1C (cfr. values of S, p~ and c. in
Table 2). This fact suggests a correlation
between the smectite content
and the swelling characteristics of
TABLE 3
Mineralogical composition of outcrop 1
Mineral composition range (%)
Quartz
Feldspars
Carbonates
Clay fraction (to 100%)
.
Clay minerals range of fine fraction(%)
Illite
Smectite
Serpentine
Chlorite
47
30
23
49
11
17
25
36
20
44
44
21
14
19

616 4.. Cancelli, A. Failla, N." Morandi
Cl
Fig. 5 - Schematic representation of diffractograms
of samples from position « 1 ,, , · corresponding
to the extreme values of the amount
of smectite.
clay rocks. Moreover, a smectite content
as low as 9% can be ~esponsible
for high swelling properties. 1·
·Because of its primary importance
on the long-term stability of slopes,
r the shear strength in drained conditions
was extensively investigated,
both on undisturbed and on re-.
moulded pelite specimens, by direct
shear and ring shear tests. All specimens
tested were cut from the sample
drawn from position 1.
For direct shear tests, both square
(breadth B = 100 mm) and circular
(diameter D = 60 mm) boxes were
adopted; for undisturbed specimens,
after having allowed complete swelling
or consolidation under the
selected normal pressure p, peak and
residual (after multiple-reversal
shear) values were determined. The
residual strength was also measured
Sm
so
by . shearing remoulded soil speci­
~ :mens along~~~~oilli:

Mineralogical Composition andGeotechnical Properties ...
/
1.0+-------/·
/.
• •
•
/"
• •
•
Peak resistance
0.5
Undisturbed
0.5
• Direct shear; square section; peak
0
•
circular
11
'' residual
peak
residual

618 A. Cancelli, A. Failla, N. M;randi
was found between ring shear tests
and direct shear tests along a soil/
rock contact, and the correlation
with lp proposed by KANJI (1974) resulted
fairly well satisfied.
Conclusions
On the basis of mineralogical data,
the pelitic facies of the Antognola Formation,
extracted from the Baiso area
for ceramic industries and examined
in several samples, differs from the
typical average composition of this
t
•
Formation: the absence of carbonates,
the low content of smectite and
the high percentage of skeletal particles
(quar:tz"-amf,_feldspar:s) "are .. to.be.
mentioned.
Within the pelites of position 1, a
wide range of geotechnical properties
were found (obtained also by non traditional
techniques), namely the
swelling and the shear strength parameters,
in accordance with a scattering
in the ratio of non-clay to clay
minerals and in the mir;teralogical
composition of the clay fraction.
Such variability of data, on a small
scale (about 1 m), is unusual in a fine
grained sediment (silty clay) and suggests
an uncommon depositional
mechanism.
REFERENCES
BrsCAYE P.E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and
adjacent seas and oceans. Geol. Soc. Am. Bull. 76, 803-832. ·
BJERRUM L., SIMONS N.E., 1960. Comparison of Shear Strength Characteristics of Normally Consolidated
Clays. Pp. 711-726, in: Proc. ASCE Conf. on Shear Strength of Cohesive Soils, Denver.
BOCCHI G., LuCCHINI F., MINGUZZI V., MoRANDI N., NANNETTI M.C., 1982. Significato .del chimismo
delle porzioni pelitiche delle «Marne di Antognola» della zona di Zocca (Modena). Rend. Soc. It.
Min. Petr., 38 (2), 839-847.
BOLZAN R., CECCARELLI 1., FAILLA A., MEZZETTI R., MORANDI N., ROMANO A., 1983. Caratteri composizionali
delle peliti oligo-mioceniche della sinclinale di Vetto-Carpineti (prov. di Reggio Emilia e
Parma). Miner. Petrogr. Acta 27, 51-71.
CANCELLI A., 1979. Sulla misura della resistenza residua dei terreni mediante prove di taglio lungo un
contatto suolo!roccia. Geol. Appl. Idrogeol. XIV (Ill), 351-365.
CHEN F.H., 1975. Foundation on Expansive Soils. Elsevier, Amsterdam, 280 pp.
DALLAN NARDI L., NARDI R., 1975. Structural Pattern of the Northern Apennines. In:

Mineralogical Composition and Geotechnical Properties ... 619
LUPIN! J.F., SKINNER A.E., VAUGHAN P.R., 1981. The Drained Residual Strength of Cohesive Soils.
Geotechnique 31 (2), 181-213. .
MEZZETTI R., MORANDI N., PINI G.A., 1980. Studio mineralogico delle porzioni pelitiche nelle «Marne di
Antognola» della zona di Zocca (Modena). Miner. Petrogr. Acta 24, 57-75.
RIPPA F., PICARELLI L., 1977. Some Considerations on Index Properties of Southern Italy Shales. Pp.
401-406, in: Proc. Int. Symp. on the Geotechnics of Structurally Complex Formations, I, Capri
(Italy). .
RovER! E., 1966. Geologia della sinclinale Vetto-Carpineti (RE). Mem. Soc .. Geol. It. 5, 241-267.
SKEMPTON A.W., 1953. The coiloidal ,;G_ctivfry~; o(clay. Pp. 57-61, in: Proc .. 3rd Int. Conf. Soi1
Mechanics Foundation Engineering, I, Zurich.

Miner. Petrogr. Acta
Vol. 29-A, pp. 621·628 (1985)
Geomorphological and Geotechnical Aspects
of the Fissured Clays of Lucera,
Apulia Region, Southern Italy
C. CHERUBINP, A. GUERRICCHI0 2 · , . .
1 Istituto di Geologia Applicata e Geotecnica, Facolta di lngegneria, Universita d1 Bari, Via Re David 200, 70125
Bari, Italia
2
Dipartimento di Difesa del Suolo, Universita degli Studi dell'1- Calabria, 87036 Arcavacata di Rende, Italia
ABsTRACT- The subapenninic blue-grey clays outcropping in the vicinity of
Lucera (Apulia Region, southern Italy) consist of clays, marls and sandy
clays etc. dated generically, in the literature, as Upper Pliocene-Calabrian.
On the basis of the existence of a disconformi ty, of a clear change of the facies
and of a clean break in the system of fissures affecting the basal clay formation
of Upper-Pliocenic age, the Authors recognize a new cycle of sedimentation
for the higher clays.
Moreover, after a geotechnical characterization of the different types of
clays, some stability analyses were made by the simplified Bishop's method.
Such analyses have pointed out that, since the slopes are affected by mining
activity they present minimal safety factors, except in the very unusual case
where the ground-water is at ground level. Those slopes cut at the base by
quarries have ea precarious equilibrium that, in some cases, has already produced
deformativ~ phenomena and/or slumps.
Introduction
Stability conditions of some slopes
and quarry fronts of marly blue-clays
near Lucera (Apulia Region, southern
Italy) are examined (Fig. 1).
The importance of such a study has
been recognized because of the exist-'
ence, in the village, of important human
structures both archaeologicalhistorical
(e.g. Norman Castle) and
social (e.g. state hospital, houses,
etc.), threatened by the aforesaid
quarry fronts developed at the foot of
the slopes, at the top of which the
above-mentioned structures exist.
The lack of an intensive study of engineering
geological characteristics
is felt more strongly because of the
numerous quarries existing in the
area. They are generally at the foot of
the slopes with ·consequences that,
even at a purely qualitative level, are
easy to imagine. Added to all this is
the dilapidated state in which some
of them are to day without any prospect
of reclamation in either the
short or the long ter.m.

622 C. Cherubini, A. Guerricchio ·
....
D I I Gill] ITIJ]]
~
G)>\ t t t
0 0.5 1.0 1.5 km
2 .3 4 5 6 7 8 9 10
Fig. 1- Geological map of Lucera village and it.s environs. 1: Fills; i: Re~ent and modern ~lluvial
deposits; 3: Pebbles and conglomerates with sandy levels (Pleistocene); 4: Sandy-clayey soils (Calabrian);
5: Clays and clayey-marls (Upper Pliocene); 6: Attitude of strata; 7: Slumps bodies and
' crowns; 8: Creep; 9: Geological section line; 10: Active quarry.
*
Geological outlines
The soils outcropping in the village
of Lucera, from the bottom to the top
are represented by (i) subapenninic
blue-grey clays (DELL'ANNA et al.,
1974) on which sediments rich in sandy
levels and centimetrical strata of
diagenized sandstones (all of marine
origin) lean unconformly, and (ii) by
other deposits of continental origin
(Figs 1 and 5).
The subapenninic blue-grey clays,
as it is known, derive from the ·

Geomorphological and Geotechnical Aspects of the Fissured ... 623
Pleistocenic-Suprapliocenic cycle of
the Post-Orogen Complex of the «Fossa
Bradanica» (OGNIBEN, 1969; DEL­
L'ANNA et al., 1974; BALENZANO
et al., 1977; JACOBACCI et al., 1976).
They are made up of clays, marly
clays and clayey marls of blue-grey
colour, with thin millimetrical silty,
sandy and sometimes blackish organic
(algal remains, etc.) levels.
The clays contain quartz, biotite,
and clasts of methamorphic rocks.
The microfauna associations given by
Bulimina marginata, Bolivina silvestrina,
Bolivina usensis, Globobulimina
pseudospinescens, Bolivina alata,
Uvigerina nodosa, Ammonia inflata,
indicate an Upper Pliocenic age and
an infralittoral environment.
The micropalaeontological data a­
bo~t the transgressive sandy-clayey
succession are not yet sufficient to
clarify the exact age.
The blue-grey clays of the Upper
Pliocene (Fig. 2) are affected by a
close net of fissures and joints represented
in the diagram of Fig. 3.
Such fissures have generally a
planar trend, sometimes with local
ondulations, so that it was always
possible to represent their significant
average trend and therefore to recognize
the following groups of discontinuities:
group A N 70° E, S 20° E: 80°
group B EW, S: 80°
group C N 50° E, N 40° W: 40°
group D NS: 90°
Fig. 2 - Particular of a quarry's front where disconformity between the basal. clays of Upper
Pliocene age and sandy-clayey soils is visible with the systems of fissures clearly stopping along the
transgressive contact. ·

624 C. Cherubini, A. Guerricchio
w
Fig. 3 - Structural analysis of the -fissures sur~,
veyed in the Upper-Pliocenic clay Formatiop
(Lambert equal area projection).
group EN 60° E: 90°
---~---- -group FN-40°W~N60°-W: 90° ~---'~-­
group G N 20° W: 90°
The fissures, in particular those
with an east-west trend, visible in
Fig. 1 cease along the line of contact
with the higher clayey-sandy formation;
this latter, for the sudden
change of the facies, the- irregular surface
of the contact with the underlying
marly clays as well as for the
aforesaid reasons seems to belong to
another epoch, probably Pleistocenic.
Stick shaped concretions with a
limonitic-goethitic covering, fill, as
far as a certain height of the quarry
fronts, some fissure intersections,
such as for example those with the
directions EW and NS. The inner
part of such concretions is formed by
poorly crystallized sulphurs (pyrite
and/or marcasite), crystals of gypsum,
monodimensional grains of
quartz and feldspars.
The oxidation zones that surround
N
s
E
all the fissures and joints, in many
cases for some centimetres, prove the
ex!stence- of a' certain ch-cui~tion of
water and/or oxidizing air and they
seem to continue in the depth below.
The spacing between the fissure
edges- ranges from a few millimeters
to one centimetre, also in the fresh
cuts of the quarry fronts. Obviously
these fissure networks have a considerable
importance for the stability
conditions of the quarry fronts as
well as for the natural slopes, considering
also the stiffness of such
clays (Fig. 4) and the probable circulation
of water inside the discontinuities.
As regards the mineralogical characteristics
deduced from the work of
BALENZANO et al. (1977), the clays
sampled in the quarry fronts present
clayey contributions from the Apenninic
chain and calcareous contributions
form the Murgian region.
In particular the carbonates form a
remarkable fraction of the total, so
that the soils of Lucera must be classified
as clayey marls. Among the carbonates,
stoichiometric calcite prevails
considerably over dolomite
while aragonite is subordinate.
Among the clayey minerals, 2M
polytype dioctahedral illite (40-60%)
prevails over the other three siallitic
minerals, represented by calcic
montmorillonite (5-15%), by ferriferous
chlorite (10-15%) and lastly by
kaolinite fireclay (20-35%).
The chemical composition (% wt)
of the samples after removal of carbonates
is mainly constituted by. Si02

Geomorphological and Geotechnical Aspects of the Fissured ... 625
Fig. 4 - Stiff clayey-marls blocks fallen from the quarry's front with sticks of sulphurs along the
main fissure surfaces.
(63.92-62.10), Ah0 3 (19.95-18.27),
Fe20 3 (4.88-5.02) and H20 (5.88-6.71).
Geotechnical data
·Blue clays
From the geotechnical point of
view the Pliocene clays, to be considered
overconsolidated and very
often stiff, show the following characteristics.
Total unit weight is variable from
2.05 to 2.12, while dry unit weight
ranges from 1.70 to 1.75 t/m 3 •
Natural water contents vary from
20.0 to.23.5% and the clay fraction(

626 C. Cherubini, A. Guerricchio
values of the -effective friction angle
and cohesion intercept:
q, = 25° and c' = 4 t/m 2
Sandy clayey soils
In places where the sandy fraction
did not prevail it was possible to
carry out some total unit weight
(1.93-1.98) and consistency limit (WL
variable among 31.5-37.8, Wp from
19.5 to 20.1) measurements. The clay
fraction of such soils is about 20%.
In these more clearly «sandy»
materials, the clayey fraction descends
to values of 16-.17% with the
> 20 Jlm fraction variable from 46 to
70%, and the silt fraction from 13 to
-- --------38%.It-wasnotpossible to carry out
any mechanical tests on soils such as
these.
Comments about the stability of the
slopes and of the quarry front
Four typical sections of the slopes
, of Lucera are reported in Fig. 5. In
,:J
order, they represent: I) the still
working_

Geomorphological and Geotechnical Aspects of the Fissured ... 627
with the following input data:
y = 2.0 t/m 3

628 C. Cherubini, A. Guerricchio
BALENZANO F., DELL'ANNA L~, DI PIERRO M., 1977. Ricerche rnineralogiche, chirniche e granulornetriche
su argille subappennine della Daunia (Puglia). Atti 2° Congr. Naz. sulle Argille 1976, Bari, Geol.
Appl. Idrogeol. 12, parte II, 33-55. ------ ~~-~-----~---~~-
JACOBACCI A., MALA TESTA A., MARTELLI G., STAMP ANON! G., 1967. Note illustrative della Carta Geologica
d'Italia alla scala 1:100.000. F.163 «Lucera». Roma, pp. 36.
OGNIBEN L., 1969. Schema introduttivo alla geologia del confine calabro-lucano. Mem. Soc. Geol. It. 8,
453-763.

Miner. Petrogr. Acta
Vol. 29-A, pp. 629-645 (1985)
Geological and Mineralogical Aspects of and Geotechnical
Approach to the Landslides in the «Crete Nere» Formation
in the Noce River Valley, Lucania, Southern Italy
L. DELL'ANNA 1 , M. DI PIERR0 1 , A. GUERRICCHI0 2 , G. MELIDOR0 3
1 Dipartimento Geomineralogico dell'Universita di Bari, Campus, Via G. Salvemini, 70124 Bari,Italia
2
Dipartimento di Difesa del Suolo, Universita della Calabria, 87036 Arcavacata di Rende, Italia
3 Istituto di Geologia Applicata e Geotecnica, Facolta di lngegneria, Universita di Bari, Via Re David 200, 70125
Bari, Italia
ABSTRACT- The , ouctropping in
the Noce River Valley (Lucania, southern Italy), consists of clay shales with
intercalations of limestones, mar!y limestones, etc.
The very difficult to assess geotechnical characteristics were determined both
for the weathered and softened clay shales and for fresh ones. The prevailing
clay minerals are represented by the association of mixed-layers illitesmectite
and dickite + kaolinite, sometimes with illite and chlorite. The
presence of dickite, found for the first time in the «Crete Nere>> Formation,
offers the possibility to develop some speculations about its origin and the
geotechnical behaviour of the clay shales.
The approach to the correlations between mineralogical composition and
geotechnical characteristics seems to be complicated by the scaly microstructure
and some,diagenetic links.
A detailed geological and geomorphological map of the landslide phenomena
is also reported.
Introduction
A rather important reference in the
study of mass movements in the Noce
River Valley is provided by the relics
of the deposits of a large, now extinguished,
Pleistocene lake (DE LOREN-.
ZO, 1898) (Fig. 1). The lake was ere-.
ated by damming of tectonic origin
(GUERRICCHIO & MELIDORO,
1981; 1983; MELIDORO, 1982). After
the failure and erosion of the natural
dam, which took place about 700,000
years B.P. during the last tectonic
phase, the stream system in the subtended
basin began to subside and
this fast movement gave rise to many
This work was carried out under the «Finalized Project on Soil Conservation- Subproject Landslide
Phenomena>>, Italian National Research Council (C.N.R.): Contract n. 80.1254.87 and was also
supported by the Ministry of Public Education with grant No. 82/7264 (40%) and No. 82/07129.
Some of the mineralogical-geochemical data were presented by L. Dell'Anna and G. Melidoro at
the Meeting «Finalized Project Soil Conservation- Landslide Phenomena» which was held in Bari
on May 22-23, 1978. - ·

630 L. Dell'Anna, M~ Di Pietro, A. Guerricchio, G. Melidoro
... ----'~-----Fig. 1--Schematic-geological·map of the Noce·RivedYasin;·l :· Meso-cenozoic car bona tic formations
/ of the Campano-Lucanian Platform; 2: Mesozoic siliceous schists; 3: «Crete Nere» Formation and
Galestrine Flysch; 4: Slipped Large rock bodies (limestrone rocks, siliceous schists); 5: Pleistocenic
lacustrine deposits of the Noce River basin; 6: Alluvial deposits; 7: Overthrust contacts; 8: Zone of
. ·tectonic damming of the Pleistocene lake of the Noce River basin; 9: Contour l~ne of the 500 metres.
impressive, and still ongoing, gravitational
movements. These movements
are especially active in flyschoid
formations essentially represented
by the «Crete Nere» («Black
Clays») Formatiop and by the Galestrine
Flysch.
Geological features
The «Crete Nere» Formation as defined
by SELLI (1962) was studied
stratigraphically by VEZZANI
(1968), but even before that COTEC­
CHIA (1958) described its main geological
characteristics although he did
include it under the term «Scaly
ophiolitiferous clays».
The «Crete Nere» Formation, also
termed «Black Flysch» (SCANDONE,
1971), outcrops in southern Italy in
patches distributed along a belt running
from the Ionian coast beginning
not far from the village of Trebisacce
and stretching out in the NNW direction
to the Thyrrenian coast almost
as far as the Gulf of Policastro. It is
allochthonous and is included in the
«North-Calabrian and I::.agonegro
Sheets» («Coltri nord-calabresi e
lagonegresi») by SELLI (1962) and
in the «Liguride Complex» by
OGNIBEN (1968). Within such a tectonic
unit, the Formation is located
between the overlaying Saraceno
Formation and the underlaying Frido
Formation; locally, it may lie directly

Geological and Mineralogical Aspects of~nd Geotechnical ... 631
on the «Panormide Complex» or on
the more elevated rocks of the «Basal
Complex» and it may be overlain by
the transgressive Albidona Flysch or
else by the Pleistocenic conglomerates
of the «Bacino di S. Arcangelo».
More recently, SPADEA (1976) excluded
the hypothesis that the Frido­
Crete Nere-Saraceno sequence can
belong to one and the same tectonic
unit and, based on petrographic considerations,
accepted that the Frido
Formation belongs instead to a tectonic
unit other than the one which includes
the Crete Nere-Saraceno sequence.
In the Noce River Valley, the
«Crete Nere» Formation does notalways
overlie the «Panormide Complex»;
indeed, in the area between
Rivello and Nemoli, at Lauria etc.
(GRANDJAQUET, 1963; GUERRIC­
CHIO & MELIDORO, 1981; 1983) it
is the «Panormide Complex>> which
was found to overlie the «Crete Nere»
'Formation. This formation consists of
clay shales and marls of ·blackish,
leaden gcey, blackish grey and occasionally
greenish colours, separated
into small scales and thin plates,
occasionally laminated, with thin
blackish levels of carbon substances
with either thinly or thickly packed
levels of limestones, marly limestones,
silica limestones and marls,
blackish or grey-blackish calcarenites
and sparse· levels of calcareous'
fine breccias and calcareous-quartzymicaceous
sandstones interstratified.
As pointed out later, one characteristic
feature is the presence of dickite
which is the first finding in the
formation. Occasionally, small mass- .
es of serpentine are found embedded
in tectonic contacts. The age, relative
to that part of the formation which
outcrops in the Noce River Valley,
should be the same as suggested by
VEZZANI (1968) for other areas,
namely the Aptian-Albian age.
Being allochthonous, the «Crete
Nere» Formation has been subjected
to intensive tectonic stresses and its
general appearance is creased and
twisted, locally chaotic. At the surface,
it is mostly chaotic, weathered,
displaced and mixed up by landslip
movements; only some minor ditches
reveal stackings of undisturbed
layers. Because of their marked susceptibility
to sliding, the «Crete
Nere» offer a landscape with gentle
forms and mild slopes in which the
few relatively more resistant spots
and slipped calcareous masses
emerge.
Mineralogical characteristics
The mineralogical analysis was
carried out on the >63 J..lm fractio~
(>90% of the total) of 21 samples of
clay shales(Fig. 2, Table 1)- 5 from
Lagonegro, 3 from Nemoli, 12 from
Lauria and 1 from Trecchina - by
X-ray diffraction, using a Philips
power diffractometer with Ni-filtered
CuKa radiation. Quantitative determination
of the most widely represented
minerals was done using the
methods of SCHULTZ (1964), RAISH
(1964) and GRIFFIN (1971) with·
MoSz and MgC0 3 as the internal stan-

632 L. Dell'Anna, M. Di Pierro, A. Guerricchio, G. Melidoro
4~
Fig. 2 - Location map of the boreholes and trench cutting from which samples have been drawn: a)
borehole; b) trench cutting; c) broken railway bridge of Lagonegro Village.
dards. For nonclay minerals, the X­
ray studies were integrated with
polarizing microscope and stereomicroscope
observations on coarser
grains.
The samples investigated were
found to consist of clay minerals,
quartz, feldspars and carbonates. The
clay minerals are mixed-layer illitesmectite
(I/S), illite, chlorite, smectite,
kaolinite and dickite; the feldspars
are orthoclase and Naplagioclase;
with weathered clay
patches on the coarser grains; the
carbonates consist of secondary
stoichiometric calcite, magnesiferous
calcite ·of the limestone fragments,
and dolomitic limestone probably derived
from the fragmentation of dolomites
and of calcareous dolomites.
The mixed layers liS were identified
and determined after the
methods of REYNOLDS (1980): they
are of the ordered type with about
30% expandable layers.
Following the definition of BRAD-

Lagonegro
sample 1 2 3 4
borehole SI SI Sw' Sw
deptli (m) · 36 4E2 35.5 45
(*)drawn from trench cutting cl4
TABLE 1
Noce River Valley

-
634 L. Dell'Anna,, M. Di Pierro, A. Guerricchio, G. Melidoro
LEY & GRIM (1961), the illite is a 2M
polytype with a chemism- as determined
by the methods of BROWN &
BRINDLEY (1980) - which reveals
Al as the principal cation in the
octahedral sheet and a low HzO con-
J
tent; it has varying degrees of crystallinity
(WEBER et al., 1976) (E = 95 to
420 A) and paragonitization (x = 4 to
17%) which was assessed on the basis
of the ratio suggested by CIPRIANI et
al. (1968). The (001) reflections give C 0
sin~ values around 19.96 A. Chlorite
is represented by the II b polytype
(BAILEY, 1980); its crystallochemical
formula, as determined after
BROWN & BRINDLEY (1980) is
(Mgz.oAlL4Fez.6)(Siz.?Alu)(OH)sOw and
. --------can-he aitriouted to the ripidolite
family (HEY, 1954). The behaviour of
the characteristic reflections as a result
of heating (JOHNS et al., 1954)
and the position of the (060) reflection
seem to indicate good crystal
structure and bo values equal to 9.306
A. Little crystallochemical information
can be obtained for the smectite
because its characteristic reflections
SiOz
TiOz
Al203
Fe203
M gO
CaO
K 2 0
Na 2 0
HzO
46.65
39.49
13.86
TABLE 2
Chemical composition of the dickite
literature data
2 3 4
45.07 44.87 45.59
0.01 0.64 0.04
40.20 38.04 39.60
0.09 1.67 0.31
0.03 0.28 0.22
0.21 0.17 0.24
0.15 0.12 0.04
0.02 0.11
13.84 14.41 13.88
overlap those of other minerals that
are pr:es~nLiiLg:r.e.atc:;cal;n.mdauce ..
The smectite has a low degree of crystallinity.
The kaolinite, too, because
of the poor resolution of the characteristic
doublets (HINCKLEY, 1963),
is poorly crystallized. Conversely, the
dickite is well crystallized and is distinguishable
from the other clay
minerals by its colour and occurrence.
In fact, it is found between the
scales of the soil as thin beds, spots
and streaks of a white colour. It does
not occur in association with kaolinite
and its chemical composition
(Table 2), as determined in 8 samples
obtained from representative clay
shales, is very close to the
stoichiometric composition with
Fez03, MgO, CaO, KzO and NazO in
traces, as in the natural compounds
to which it can be compared with respect
to X-ray and optical properties
(Tables 3 and 4) and density (Dmeas.
and Dcalc. = 2.61 g/cm 3 ).
Concerning the relationship between
the identified components in
terms of abundance (Table 5), the
«Crete Nere» (8 samples)
45.97
0.07
39.54
0.23
0.15
0.11
0.05
0.02
13.96
:2:
0.2
0.4
0.2
C%
0.5
0.9
1.3
100.00
99.62 100.20 100.03
100.10
1: stoichiometric dickite; 2: FERLA & ALAIMO (1975); 3: DEER et al. (1962); 4: average
sample (AMICARELLI et al., 1977)

Geological and Mineralogical Aspects of and Geotechnical... 635
TABLE 3
Lattice constants of the dickite
5.149
8.949
14.419
98°48'
litera tu re data
2
5.150 ± 0.001
8.940 ± 0.001
14.424 ± 0.002
96°44' ± 1'
3
5.154 - 5.160
8.930 - 8.942
14.418 - 14.430
96°49' - 96°51'

a­
"' a-
TABLE 5
Mineralogical composition of the

Geological and Mineralogical Aspects o(and Geotechnical... 637
rock portion- appears to be splitting
into scales, thin plates or hard
little prisms in depth; at the surface,
wherever it has been affected by
weathering processes and dislocation
and mixed up by landslide phenomena,
the clay shale portion has
undergone a softening process which
has partially destroyed its scaly nature
and structural layout with an
ensuing remarkable decay of its
mechanical strength characteristics.
The geotechnical behaviour of the
unweathered and softened scaly clay
shale is obviously different. This is
shown in Table 6 which gives the
mean values of laboratory tests made
on 12 undisturbed samples obtained
from boreholes at Lauria.
The textural microscopic features
are similar to the macrosc_opic features.
In fact, the microphotographs
presented in Figs 3a and 3b obtained
by the scanning electron microscope
(SEM) show a high level of isoorientation
of the thin plates with a
flat-undulating microtexture; The
surfaces of microscales are very
smooth and on them the domains and
particles appear to be «imbricated»
and welded almost in continuity, by
stress activities and diagenetic
bonds. This gives rise to a strongly
anisotropic mechanical behaviour
both parallel and normal to the fissility
surfaces. When the scales are intact,
unweathered, their microstructure
is rather compact with very minute
pores.
Particle-size distribution, as determined
with the ASTM technique,
shows that the «sand» and «gravel»
contents prevail over the clay contents.
This is quite often due to the
argillitic nature of the soils, so that
these conventional techniques are inadequate
to obtain complete disaggregation
of the hardest little scales.
On the basis of the colloidal activity,
taken as the ratio between the plasticity
index and the clay content (d:::;
0.002 mm), they can be classified as
TABLE 6
Mean values of some geotechnical characteristics of the

638 L. Dell'Anna, M. Di Pierro, A. Guerricchio, G. Melidoro

Geological and Mineralogical Aspects of and Geotechnical... 639
Fig. 3 - Microtexture of «Crete Nere>> (Black Clays) of La~ria Inferiore V_ill~~e by the SE!'1·
a: cross-section to the fissility surface; planar ondulated m1crotexture; b: flSSI!rty surface w1th
planar microtexture constituted by isoriented and «welded>> domains and plates; c: dickite associations
along a fissility surface.

640 L. Dell'Anna, M. Di Pierro, A. Guerricchio, G. Melidoro
same soil, but weathered and with a
low scale content, is higher than the
average (0.95), with an experimental
peak of 0.98. For the weathered and
softened surface soil, lower unit
weight values and higher water
limits and contents were obtained.
Concerning the characteristics of
residual shear strength determined
by means of reversal, the effective
mean friction angle is 16°. Such low
strength ought to be close to that
which occurs along the scaly surfaces.
Lastly, preliminary tests indicate
that the mechanical strength is considerably
lowered by large amounts
of dickite; very likely, this is due to
the «lubricating effect» of this powdery
mineral along the scaly surfaces.
Landslide phenomena
The rupture of the tectonic damming
in the Noce River Valley, which
had created the big Pleistocene lake,
\
marks the beginning of a long landsliding
phase due to the rapid sinking
of the stream system. Gravitational
movements of large masses, which
are displaced by a sliding mechanism
·are often interpreted as active tectonic
phenomena just because they
occur at sites which correspond to
structural organizations produced by
faults, tectonic superpositions, etc.,
according to the recent findings by
GUERRICCHIO & MELIDORO
(1981) in the South Apennine Range.
Th~y are more apparent by characteristic
«fresh>> bands, of a lighter colour,
which become unevenly broader
as time goes by along the contacts between
masses of limestones and
dolomitic limestones and flyschioid
formations or colluvia .. Quite often
these bands are «freshened up>> as a
result of an earthquake as, for example,
at Senerchia, in the Sele River
Valley and in the Valley of the Sauro
Torrent near Stigliano (Lucania), following
the catastrophic earthquake
which occurred in Campania and
Lucania on November 23, 1980. In
the Noce Valley, these «fresh>> areas
have been observed as a band marking
the site of landslide detachment
in the limestone masses at Lauria.
Concerning the susceptibility to
landsliding of the Noce River basin, a
rather ·interesting comment was
made by BRUNO (1891) at the end of
the last century: «In this basin, except
for some peculiar exceptions, everything
may be said to be in motion:
so great is the number of landslips
and sliding soils>>. Obviously this
statement should be understood with
reference to the flyschioid formations.
Among the major landslide movements
in the basin studied, special
mention should be made with reference
to the built up areas at Lauria,
Lagonegro, Trecchina, and Nem9li or
to road and railway infrastructures.
The stream system is subject to continuous
deformation and, as a consequence,
the channelled waters produce
toe erosions which in turn
cause remobilization of large landslide
bodies. These landslides are responsible
for major problems with

~ - - -- -
Geological and Mineralogical Aspects of and Geotechnical... 641·
respect to soilconservation and economic
and social development all
over the valley.
Because of its specific geological
and geomorphological conditions,
Lauria is, at present, one of the villages
most seriously affected by the
landslide phenomena which mostly
prevail in the «Crete Nere» or are induced
by them in the calcareous
rocks (GUERRICCHIO & MELIDORO,
1983).
At Lagonegro, the calcareous cliff
on which the older part of the town
tests is involved in the mass movement:
the mass was crossed by a railway
tunnel and a high a~ch bridge
was built at the exit from the tunnel
in the 1930's (Fig. 4). Above this
structure, soon after it was completed,
there bega.n to develop, deformations
and failures which are
still going on due to the very slow
«Sinking» motion into the flysch and
to the tilting movement of the rock
mass.
At Trecchina, impressive landslide
)movements are observed inside the
«Crete Nere» from where they begin
and deve}op upwards to dismantle
the overlying Pleistocene lacustrine
deposits.
Lake Sirino is believed by some to
be of glacial origin, whereas others
think it was simply created by landslide
damming across the lake's
effluent. Recently, it has been demonstrated
(GUERRICCHIO & MELI­
DORO, 1981) that the whole body of
water is a classical landslide-created
lake which was formed as a result of
the slopewise sliding, along the bedding
planes, of a huge bulk of «silica
schists» and galestrine flysch that
had fallen off the mountain and
whose large failure surface is still
visible.
The map in Table 1 reports a geolo-
.Fig. 4 - Failure of the railway bridge near Lagonegro Village (see Fig. 1) produced by the slow
movement of the masses of carbonatic rocks on the flyschioid formations, partially constituted by
the «Black Flysch». ·

642 L. Dell'Anna, M. Di Pierro, A. Guerricchio, G. Melidoro
gical and geomorphological survey of
the mass movements in the soil at
and around Nemoli, reproduced on a
1:2000 scale. In addition to normal
landslide phenomena such as slumps
and earthflows, large mass movements
are also present which are due
to «deep gravitational failure>>,.
«lateral spread>> and, occasionally,
«sackung>>. Ancient dormant mass
movements have been distinguished
from ongoing ones by using different
colours in the map. Within each
landslide phenomenon, various
morphological features such as edges
and primary and secondary failure
scarps-have-·been mapped· wherever
they are still visible, and so have the
boundaries of the landslide body, depressions
and basins, counterslope
surfaces, the main direction of the
mass movement, etc.
Interesting phenomena of lateral
spread are observed in the Arenazza
carbonate relief, only part of which
falls within the northwest section of
the surveyed area (Fig. 5).
It often happens that the earthflows
dichotomize the stream beds,
as in Vallone Ferriera, an event that
2 ~===~ --
a
4~
0
200 400
Fig. 5 - Schematic geological map of the lateral spreads in the Arenazza carbonate relief and of the
flows in the «Black Shales Formation~. 1: Calcarenites, calcilutites, dolo mites of the M.te Fora porta
se.rie and dolomites with Megalodon of the Carbonatic serie of Lucanian-Silentini massif; 2: «Crete
Nere>> Formation; 3: Nomenclature of a landslide; a) crown a;nd main scarp; b) slumps; c) secondary
scarp; d) sense ofthe movement; e) flows; f) limit ofthe landslide body; 4: overthrust; 5: springs.

Geological and Mineralogical Aspects of and Geotechnical ... 643
is clearly apparent in the body of the
ancient mass movements.
Due to the high rate of viscosity of
the clay material, the flows have a remarkable
dragging capacity so that
large calcareous-dolomitic blocks
(often as large as hundreds of metres)
from the overlying mass are dislocated
and crushed, or else left behind
along .the sides of the «channels» in
the form of .
The slumps and earthflows described
thus far are only Qccasional
and local manifestations in the large
rock mass underlain . by the deep
gravitational failure. Elsewhere, the

644 L. Dell'Anna, M. Di Pierro, A. Guerricchio, G. Melidoro
which disguised such correlations.
Difficulties could also arise from
possible local differences deriving
from the fact that the clay shales
were involved in different geologic
events during anP/or after their deposition
so that the genetic interpretation
of the main identified association
becomes extremely difficult
to understand. In fact, the heterogeneity
of the identified minerals
seems to point to a heritage in the
genesis of the sediment: still, the presence
and occurrence of dicki te seem
to suggest a rather strong postdepositional
diagenesis resulting
from burial and/or tectonization
---- which might be responsible for the
building of ordered mixed-layer IfS
through the mechanism smecti te --7
mixed-layer IfS --7 illite. In this context,
however, one could not understand
the absence of dickite and/or
nacrite in samples containing the~
simple association illite + chlorite.
Furthermore, the fact that certain
illites are poorly crystallized and paragonitized
seems to indicate further
transformations during an early diagenesis
and that these were also re-
SJ?Onsible for feldspar weathering;
the formatioRof-dickite~too, according
to the most recent genetic interpretation
(FERLA, 1982) could be
ascribed to this diagenesis. There are
·no elements contrary to the genetic
hypothesis according to which dickite
was formed through hydrothermal
effects which were penecontemporaneous
or posterior to
sedimentation; the hydrothermal
effects would be more or less directly
responsible for the presence of thenardite,
Na 2 S0 4 , which was found to
be associated with dickite in some
«Crete Nere» samples during further
analyses. Lastly, the geological and
geomorphological detailed study of
the mass movements in Nemoli and
its surroundings not only provides a
precise idea about the typology, entity
and frequency of these gravitational
movements, but it also clearly
shows that the _mass movements
which are normally observed are,
in many instances, nothing but
occasional and local manifestations
of far more deep-seated movements
affecting very much larger rock
masses.
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BRADLEY W.F., GRIM R.E., 1961. Mica Clay Minerals. Pp. 208-241, in:

. ..----
Geological and Mineralogical Aspects of and Geotechnical ... 645
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RAISH H.D., 1964. Quantitative mineralogical analysis of carbonate rocks. Texas J. Sci. 16, 172-180.
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VEZZANI L., 1968. Studio stratigrafico della Formazione delle Crete Nere (Aptiano-Albiano) al confine
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Miner. Petrogr. Acta
Vol. 29-A, pp. 647-660 (1985)
Upper Miocene Clays from Vallone Salina, SW Cosenza,
Calabria: Textural and Compositional Characteristics
with Geotechnical and Paleoenvironmental Aspects
F. BALENZAN0 1 , L. DELL'ANNA 1 , M. DI PIERR0 1 , V. RIZZ0 2
1 Dipartimento Geomineralogico dell'Universita di Bari, Campus, Via G. Salvemini, 70124 Bari, Italia
2
Istituto di Ricerca per la Protezione Idrogeologica, C.N.R., Via Marconi 28, 87030 Castiglione Cosentino Stazione,
Italia
ABSTRACT- In accordance with geological data (ORTOLANI et al., 1979), the
pelitic sediments of Vallone Salina (southwest of Cosenza) were deposited in
a neritic environment after a long transport in suspension during the period
ranging from the Upper Tortonian to the Messinian.
The largest part of the sediments derives essentially from the metamorphites
and magmatites of the Calabrian Alpine overthrust rocks; the clay minerals
(illite, smectite, mixed-layer illite-smectite, chlorite, kaolinite and mixedlayer
hydrobiotite-vermiculite) are the products of various areas of diagenesis
in a continental environment during weathering of the parent rocks
and in a marine environemnt during transport and sedimentation.
During deposition of the medium to high part of the sediments, almost at the
time of the passage from the Upper Tortonian to the Messinian, a deepening
of the sedimentation basin took place. With the deepening, there. occurred an
enrichment in clay, smectite and calcite from direct chemical precipitation,
as well as from a change in the source areas. At first, material was brought in
from the upper overthrust rocks (Polia-Copanello Units), and later from those
in an intermediate position (Castagna Units and Bagni-Fondachelli Units) of
the Calabrian Alpine chain.
The deepening began in correspondence with a volcanic event that caused
the direct deposition of volcanic ash. Probably the volcanic event and
deepening of the basiri are geologically related.
In the upper part of the sediments, in correspondence with the beginning of
the deposition of diatoms, a partial closing of the basin took place.
The pelitic sediments of Vallone Salina have very poor geotechnical properties.
The Atterberg limits are correlated with the clay content and are
strongly affected by the amounts of carbonates and clay minerals present,
particularly smectite.
introduction
The clays investigated outcrop at
Serra d'Aiello, Cleto and Savuto (Fig.
1), southwest of Cosenza, Calabria
(southern Italy). They belong to Upper
Miocene sequences of the Calabrian
coastal chain and were deposited
before the tectogenic phase of
,the Lower Messinian (ORTOLANI et
al., 1979). These sequences have similar
environmental facies with local
variations (DI NOCERA et al., 1974;
This research work was carried-out with the financial support of C.N.R. ·

648 F. Balenzano, L. Dell'An.na, M. Di P!erro, V. Rizzo
------r ·----------~-~-----·--- -·· ___ )" __ -·
-z_
EZJ2
EJE]4
0 2 4 6km
Fig. 1 -Geological scheme of the area considered and location of the section studied. 1: Quaternary;
2: Messinian-Lower Pliocene sedimentation cycle; 3: Tortonian-Messinian sedimentation cycle; 4:
SJlbstratum (ORTOLANI et al., 1979).
ROMEO & TORTORICI, 1980). From
the base upward, the sequences consist
of continental conglomerates, littoral-calcareous
sandstones, pelagic
clays with abundant microfauna,
euxinic diatoms and evaporites. The
clayey unit is a maximum o~ 80 m
thick. In the area of Serra d'Aiello,
Cleto and Savuto the clays are interbedded
with minor sandstone layers
and sometimes with conglomerates
of pelagic rock elements (Fig. 2) ..
The clays are rich in planctonic
foraminifera, lamellibranchia with
thin shells and Dentalia (DI NOCERA
et al., 1974); the microfauna suggest

s::
·~ "'
s::
Vl
Vl
Cl)
:;:
s::
·~
s:: "'
0
4-'
"' 0
I-
Cl)
"'
D..
D..
:::>
100
~
-rd.,-,-- 80
...!;!_
.............. ...._
....... ...L. ..L 60
..,... .,...d...._
..L. ...L.
25 r-·-.-_~• __,..._, 40
..L...L."T'"-rj
24 a 20
2~ .,.. ..,... ...... .J.
22 1
21 ,- ,- ..L ......
20
19 a
Upper Miocene Clays from Vallone Salina ... 649
E

650 F. Balenzano, L. Dell'Anna, M. Di Pierro, V. Rizzo
large amounts of Mn (BONI &
ROLANDI, 1975). The two samples
from the lowest part of the s~ries
were taken at a site west of Savuto,
where the passage to underlying 'calcareous
sandstones can be seen.
The objectives of the work presented
here were to determine the
granulometric, mineralogical and
chemical features of the clayey unit
. in relation to the general characteristics·
of sedimentation, origin of the
minerals and the main related
geotechnical properties.
Particle size analysis was carried
out by wet sieving for the greater
than 32 ).LID fractions and by sedimentation
for the other size fractions
(MILNER, 1962).
The mineralogical studies were
carried out using a Philips powder X­
ray diffractometer with Ni-filtered
CuKa radiation. Mixed-layer illitesmectite
(liS) clay minerah were
identified in accordance with ihe
methods of REYNOLDS (1980) and
SRODON (1981); the structural and
chemical characteristics of illite,
according to CIPRIANI et al. (1968),
WEBER et al. (1976), BRADLEY &
GRIM (1961), BROWN & BRINDLEY
(1980), and DI PIERRO (1981); those
of the smectites according to
GREENE-KELLY (1953), MAC
EWAN (1961), BISCAYE (1965), BRI­
GATTI (1983), and DESPRAIRES
(1983); those of chlorite, according to ·
. J
HEY (1954), JOHNS et al. (1954),
CARROL (1970), BAILEY (1980), and
BROWN & BRINDLEY (1980);- and .
;the degree of crystallinity ofkaolinite
according to HINCKLEY (1963).
The quantitative evaluation of the
main minerals was carried out on the
sand (63-125 ).LID); silt (4-63 ).LID) and
clay (less than 4 ).LID) fractions in
order to reduce errors due to the
«matrix .effect»; the methods of
RAISH (1964), SCHULTZ (1964) and
GRIFFIN (1971) were followed using
MoSz and MgC03 as internal standards.
The mineralogical analyses of
the non-clay minerals were completed
with microscopic observations
using a polarized light microscope.
Methods of analysis
------------~~------------ __________ __i:he~fal an~Jyses of the samples
after removal of carbonates were
done by X-ray fluorescence spectroscopy
using a Cr tube. Atomic absorption
spectroscopy was used to determine
the Ca and Mg in the carbonates,
and the Brush-Penfield method
(TREADWELL, 1954) was used to determine
HzO+. The Atterberg consistency
limits were measured following
ASTM standards D 423-66
and D 424-59 (65).
Results
Samples 1-16, taken from the lower
part of the clayey sequence, were
found to have different particle size
and compositional characteristics
than those of samples 18-25, taken
from the medium-high part of the
same sequence. Sample 17, which divides
these two groups of-samples, is
rich in ash tuff material.

TABLE 1
Granulometric characteristics
%Wt
% Cumulative

652 ·F. Balenzano, L. Dell'Anna, M. Di Pierro, V. Rizzo
a) Particle size analysis. All samples The smectite is Al-rich (bo varying
consist of very fine grained material. from 9.05 A to 9.15 A; Mg+Fe­
The grains have a maximum size of octahedral= 0.10-0.20), with Mg-~;:;d~--
125 Jlm and are predominantly in the Kas the interlayer cations, and J.:las a
less than 2 Jlm and 8-16 Jlm fractions high degree of crystallinity (v/p=1).
(Table 1). As compared with samples The mixed-layer liS minerals are
1-16, samples 18-25 are richer in clay mostly disordered and have 20% to
(t = 4.31; P ~ 99.9%)(1) and poorer in 50% smectite layers. The chlorite is
silt (t = 3,24; P ~ 99.9%) (Table 1). the lib polytype and has a rather
Samples 18-25 fall in the clay and good degree of crystallinity; its chemsilty-clay
fields of SHEPARD's dia- istry varies from ripidolite to the
gram (1954), while samples 1-16 fall pseudothuringite-daphnite composiin
the silty-clay and clayey-silt fields .tions (bo varying from 9.30 A to 9.35
(Fig. 2).
A). The kaolinite has a low degree of
After carbonate removal, the decar- crystallinity. The carbonates are calbonated
samples show an enrich-. cite and dolomite, with traces of Mgment
of the fine fractions at the ex- calcite and aragonite. The feldspars
, pense of the 8-16 Jlm fraction as well are Na-plagioclases and K-feldspars.
--~1------- -as a consiaera01e atteniia1ion_m_fue--""Mrcroscoj5ic observations of the
difference between the two groups of coarser fractions showed that the
samples. The cumulative curves (Fig. quartz and feldspars are often cata-
2) show an upward concavity, more clastic. The feldspars present are
marked in samples 1-16. Sample 17 mainly albite and microcline with
has characteristics intermediate be- patches of weathered clay and sometween
those of the two groups. times with quartz and apatite inclub)
Mineralogical analysis. All sam- sions. The micas are greenish-brown
ples consist of clay minerals,' carbon- biotite and .muscovite which often
ates, quartz, feldspars and micas. The show inclusions of ilmenife and
clay minerals present are illite, smec- graphite. Microscopic analysis also
tite, mixed-layer illite-smectite (liS), showed the presence of chlorite, mica"
chlorite and kaolinite. The powder schists and chlorite-rich schists,
diffraction data indicate that the Na-ampbiboles (glaucophane and
illite is the 2M polytype (eo sin ~ riebeckite), actinolite and hornvarying
from 19.978 A to 20.124 A) blende amphiboles, almandine garwith
Al as the main oct~hedral cation net, tourmaline, · sillimani te,' chlo­
(bo varying from 9.008 A to 9.013 A), ritoid, phlogopite, apatite, strengite,
and K as the interlayer cation (the de- vivianite, rutile, ilmenite, birnessite,
gree of paragonitization varies from Fe-hydroxide from weathering,
2% to 15%); the degree of crystallin- glauconite, gypsum, sponge spicules
1
and pyritized echinoderm · remains.
ity is moderate (from 90 A to 21 o A).
(I) t = Student' !-test; P = statistical significance.

TABLE 2
Mineralogical characteristics
total
clay fraction
I s liS Ch K Q F Ca Do C.m. C.a. Q+F I s liS Ch K
Sample 1 21 13 7 4 3 12 2 35 3 48 38 14 44 27 15 8 6
2 27 11 4 3 1 13 3 35 3 46 38 16 59 24 9 6 2
3 23 10 2 6 2 14 3 35 5 43 40 17 53 23 5 14 5
4 25 10 5 5 2 10 2 37 4 47 41 12 53 21 11 11 4
5 27 8 5 5 2 12 2 35 4 47 39 14 57 17 11 11 4
6 31 10 5 3 2 10 2 34 3 51 37 12 61 19 10 6 4
7 23 9 7 4 2 13 2 36 4 45 40 15 51 20 15 9 5
8 23 12 5 5 tr 11 2- 38 4 45 42 13 51 26 11 11 1 ~
'

654 F. Balenzano, L. Dell'Anna, M. Di Pierro, V. Rizzo
The clay minerals (:X = 47%) are rarely sodic (glaucophane and
slightly more abundant than the car- riebeckite), while those in the .. seconcL
bonates (:X = 40%) and prevail over group are almost exclusively sodic.
quartz (:X = 11 %) and feldspars (:X = The carbonates in the first group are
2%) (Table 2). Among the clay mine- essentially organogenic, but inorganrals,
illite (:X= 24%) is more abundant ic carbonates are also present, while
than smectite (:X = 11 %) and prevails those in the second group are almost
over mixed-layer I/S (:X = 6%), chlo- exclusively organogenic. Mica schists
rite (x = 4%) and kaolinite (x = 2%). and chlorite-rich schist fragments are
Among the carbonates, calcite (x = found almost exclusively in samples
36%) prevails over dolomite (x = 4%). 18-25, which sometimes also contain
The mineralogical characteristics hydrobiotite and ·mixed-layer
(Table 2) of samples 1-16 are different hydrobiotite-vermiculite, while
from those of samples 18-15. The phlogopite is found almost exclusiveillite
in samples 18-25 is more Al-rich ly in samples 1-16.
(bo = 9.008 A) than that in samples In accordance with the gran-
1-16 (bo = 9.013 A). The chlorite in the ulometric data and the particle size
first group of samples (18-25) is distribution of clay minerals (DEL-
·-···--·-·--------pseudothuringite~daphllite--in--co~- ·- L'ANNA &-:R.Izzo, 1979), samples
position and has the average struc-. 18-25 (Fig. 3) are richer in smectite (t
tural formula, (Mgz.3oFez.osAl~.~s) = 4.43; P ~ 99.9%) and poorer in
(AlJ.szSizAs)Ow(OH)s, while the chlo- illite (t = 3.19; P ~ 99.5%); howevrite
in the second group (samples 1- er, they also are richer in carbonates
16) is ripidolite (HEY, 1954) and has (t = 4.15; P ~ 99.9%) both as calcite
the average formula (MgL9zFez.7oAlu 8 ) (t = 3.18; P ~ 99.5%) and as dolo-
(AluzSiz.6s)Ow(OH)s. The amphiboles mite (t = 2.60; P ~ 99%).
of the first group are mostly actino- The mineralogical composition of
lite and hornblende and are only sample 17 is distinctly different from
25 50 50
l/S+Ch+KL------...,....------~
50 50
Fig. 3- Mineralogical differences between samples 1-16 (A) and samples 18-25 (B). Mineral abbreviations
as in Table 2.

Si0 2
Ti0 2
Al 2 0 3
Fe 2 0 3
M nO
Cab
M gO
Na 2 0
K 2 0
PzOs
Hzo+
CaQ
M gO
C0 2
tr: traces
TABLE 3
Chemical analyses
--
Sample
2 3 4 5 6 7 8 9 10 11 12 13 14 IS 16 17 18 19 20 21 22 23 24 25
38.1 38.0 37.3 36.5 37.2 39.0 36.2 JS.l 37.2 37.4 38.6 36.7 36.7 39.6 40.2 38.4 47.2 35.6 34.5 35.4 38.0 34.5 36.4 37 .I 36.5
0.6 0.6 0.5 0.5 0.6 0.6 0.5 . 0.6 0.6 0.6 0.6 ·. 0.6 . 0.6 0.6 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
11.6 11.4 11.0 10.3 11.1 11.6 11.4 11.0 11.5 11.6 11.7 11.6 11.9 11.9 11.9 11.0 12.6 9.8 11.1 10.7 11.2 10.4 10.4 10.7 10.4
3.5 3.6 3.0 3.2 3.8 3.7 3.3 3.3 3.5 3.6 -1.6 3.4 3.5 3.6 3.7 3.5 4.3 2.9 3.3 3.3 3.5 3.3 3.5 3.7 3.4
OJ. 0.1 0.2 0.1 0.1 0.1 0.1 tr tr tr tr 0.1 0.1 0.1 0.1 0.1 0.1 0.1 tr 0.1 tr tr tr . 0.1 0.1
0.6 .. 0.8. 0.6 0.5 0.4 0.4 " 0.4 0.4 0.3 0.4 0.4 0.3 0.3 0.3 0.3 0.3 0.7 0.3 0.2 0.2 0.3 0.3 0.3 0.4 0.3
·1.4 1.4 .. 1.3 1.3 1.4 1:4: 1.4 1.3 1.5 1.5 1.5 1.4 1.4 1.4 1.5 1.4 1.8 1.2 1.3 1.3 1.4 1.3 1.4 1.5 1.4
0.7 0.7 0.8 0.8 0.7 0.7 0.8 0:6 0.1 0.7 0.8 0.6 0.7 0.8 0.7 0.7 0.9 0.7 0.6 0.6 0.7 0.6 0.6 0.6 0.6
1.8 1.8 1.7 1.8 1.9 •. 1.9 . 1.8 1.8 1.9 1.9 1.9 1.9 .• 1,9 2.0 2.0 L9 2.0 1.6 1.8 1.8 1.8 1.8 1.9 1.9 1.8
0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
3.5 3.7 2.9 3.4 3.7 3.6 3.1 3.7 3.5 3.8 3.5 3.6 3.7 3.7 3.9 3.2 3.4 2.5 3.5 3.3 3.4 3.2 3.2 3.5 3.1
20.5 20.3 21.3 . 22.1 2LI •' 19.8 .. 2L8 22.3 20.8 20.6 19~9 21.0 21.2- 18.9 18.4 20.7 138 23.9 22.6 23.0 2\.i 23.9 22.0 21.1 . 21.6
0.8 0.7 1.1 0.8 0.8 0;1 0.9 0.9 0.8 0.8 0.7 1.0 0.8 0.8 0.8 0.8 0.9 1.1 1.1 0.8 0.8 0.8 1.0 p 1.5
17.0 16.7 17.9 18.2 ·17.4 16.3 18.1 18.5 i7.2 17.0 16.4 17.6 17.5 15.7 15.3 17.1 11.8 20.0 18.9 18.9 17.4 19.6 18.4 17.9 18.6
100.3 99.9 99.7 99.6 100.3 99.9 99~9 99.6 99.6 100.0 99.7 99.9 100.4 99.5 99.5 99.8 100.1 100.3 99.5 10(}.0 100.2 100.3 99.7 100.3 99.9
~
'

I"''
F. Balenzano, L. Dell'Anna! M. Di Pierro, V. Rizzo
· the others. Along with a limited = 0.432, P ;;,: 98%; Ip, r = 0.402,
quantity of the minerals found in the P ;=: 97%); therefore the g:r:mw oL
group of samples 1-16, sample 17 has samples 1-16 is geotechnically diffean
abundance of smectite and volcan- . rent from the group of samples 18-25
ic ash composed of vitreous frag- (WL, t = 2.380, P ;;,: 99%; Wp, t =
ments and pumice with inclusions of 1.776, P ;;,: 93%; Ip, t = 1.574, P ;;,:
quartz, orthoclase and biotite; the 92%). According to Casagrande's
vitreous fragmens have an index of plasticity chart the samples in the
refraction of 1.50-1.51. Samples 16, first group have a medium to high
18 and 19 also contain small amounts plasticity, while those in the second
of volcanic ash. The morphological group fall into the high plasticity
characteristics of the grains of sam- field (Table 4; Fig. 4). In addition,
pies 16 and 17 show a direct sedi- samples 1-16 show both normal and
mentation of the volcanic ash with- inactive coll~idal activities (Table 4;
out transport by water.
Fig. 5), while those in the second
The clays from the highest parts of group (samples 18-25) are all inactive
the sequence, above sample 25, were probably because of the different infound
to have considerably less de- fluence of various carbonates. Sam-
----r---.-----·-tritar fragments- ··aiid___ caroonates;---pie--f7has-hlgher consistency limits,
while the presence of pyrite was probably because of the presence of
appreciable and there were conside- large amounts of smectite and relrable
amounts of birnessite and di- atively small amounts of carbonates;
atoms.
it also has a high plasticity and highc)
Chemical analysis. The results of er colloidal activity (Table 4; Figs. 4
the chemical analyses are reported in and 5).
Table 3. In accordance with the
mineralogical composition, the noncarbonate
chemical components are Discussion
mostly SiOz, Ab03, Fez03 and HzO+.
After the carbonates have been removed,
chemically there are no significant
differences between the two
groups of samples (samples 1-16 and
18-25). In addition to its very low carbonate
content (26%), sample 17 has
a singular chemical composition
(Table 3) because of the abundance of
volcanic ash.
d) Geotechnical properties. The
Atterberg consistency limits are
linearly correlated with the clay content
(WL, r =_0.564, P ;;,: 99%; Wp, r
The Vallone Salina Upper Miocene
pelitic sediments show granulometric
characteristics of a neritic
sedimentation; the grain size distribution
is characterized by a, moderate
sorting which improves with
the disappearance of organogenic
carbonates and indicates deposition
after prolonged suspension in water.
The increase in the amounts of fine
fraction and smectite and the appearance
of fine carbonates from chemical
precipitation in the medium-high .

Upper Miocene Clays from Vallone Salina ... 657
TABLE 4
Atterberg consistency limits
WL Wp lp lp/

'':
F. Balenzano, L. Dell'A nna, M. Di Pierro V R'
------T-----=~=~,:·· 1 zzzo
Low ~1edium High
F 30
LiOOid 1 ;;n ,
40
80
Jg. 4 - Plast' !City · Chart A' s:o 60
. . samples 1-16· ' B. . samples 18-2570
20 -~~--~-~~~~,~
70
..
X
60
'"
~
~
·u
t
50 0:: "'
Active
Normal
sample 17
...
! Inactive
40
F' Jg. 5 - Colloidal 10 . ActivJ't 20 Ch 30 40 50 60 Cl ay fraction (

mon in metamorphites and magma-
--~~~- tites of the Alpine overthrust rocks.
The presence of different types of
amphiboles, almandinE: garnet, tourmaline,
chlorithoid, sillimariite,
phlogopite, and Fe and Ti minerals
confirms the origin from metamorphic
rocks of the sedimeJ;J.tS and
appears to be related with the overthrust
unit sequence (AMODIO­
MORELLI et al., 1976). In addition,
some typical mineralogical characteristics
of the clays are similar to
those of the Alpine overthrust rocks
(the glaucophane content of the Na-
. amphiboles, the essentially triclinic
character of the K-feldspars, the
essentially albite composition of the
.. plagioclase, the inclusion of both
quartz and apatite in the feldspars
and of ilmenite and graphite _in the
micas, the remarkable catacla~tic
texture in the sialic and femic minerals
and the colour of the biotites and
chlorites). However, the almost exclusivepresence
in the group of samples
1-16 of Na-amphiboles and
· phogopite associated with sillimanite
and rutile leads to the hypothesis of
contributions from the upper units of
the Alpine chain (Polia-Copanello U­
nits, according to AMODIO-MORELLI
et al., 1976) while the presence of various
amphiboles and micaschists and
chlorite-rich schist fragments in the
group of samples 18-25 suggests a
derivation from the middle units of
the same chain (Castagna Units and
Bagni~Fondachelli Units, according
to AMODIO-MORELLI et al., 1976).
This hypothesis also is supported by
Upper Miocene Clays from Vallone Salina ... 659
the ferri-muscovite composition of
the illites (bo = 9.013 A) in samples
1-16, the essentially muscovite composition
in samples 18-25 (bo = 9.008
A), (DIETRICH et al., 1976) and by the
marked ferromagnesian composition
of the chlorites in the first group as
compared to those of the second
group of samples.
In regard to the origin of the clay
minerals, the illite may be derived
froro the weathering of the feldspars
and muscovite already in the parent
rocks; the kaolinite and chlorite
probably were derived from the
weathering of the feldspars and chlorite
in the parent rocks. The stnectite,
because of its higher crystallinity,
could have been formed by aggradation
both in continental and marine
environments during transport and
sedimentation, while the mixed-layer
minerals probably were derived from
early diagenesis according to the
following transformation sequence: ,
illite ~mixed-layer I/S and biotite ~
hydrobiotite ~ mixed-layer hydrobiotite-vermiculite.
The sedimentation environment
changes entirely in the most upper
part of the peli tic sequence of Vallone
Salina. The carbonates and the
amount of detrital sedimentation decrease
considerably; sulfides, and Fe
\ and Mn hydroxides increase, and
f::Onsiderable amounts of diatoms are
found. This may have been caused by
the absence of sea-bottom currents
and poor oxygenation of the water
due to partial closing of the basin.
(

660 F. Balenzano, L. Dell'Anna, M. Di Pierro, V. Rizzo
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granulometrica e alcune caratteristiche geotecniche. Geol. Appl. Idrogeol. 14, 57-86.
DESPRAIRIES A., 1983. Relation entre le parametre b des smectites et leur contenu en fer et magnesium.
~,- ~---~-----------Applicalion-aTltuae -des- sMiliuints~ 'CfliYMineraTS 18, lo5-T7S: - ·
DIETRICH D., LORENZONI S., SCANDONE P ., ZANETTIN LORENZONI E., 197 6. Contribution to the knowledge
of the tectonic units of Calabria. Relationship between composition of K-white micas and metamorphic
evolution. Boll. Soc. Geol.It. 95, 193-217.
Dr NocERA S., 0RTOLANI F., Russo M., ToRRE M., 1974. Successioni sedimentarie messiniane e limite
Miocene-Pliocene nella Calabria Settentrionale. Boll. Soc. Geol. It. 93, 575-607.
Dr PIER:OO M., 1981. Caratteri composizionali delle argille pleistoceniche della zona di Miglionico (MT).
Rend. Soc. It. Min. Petr. 37, 229-240.
GREENE-KELLY R., 1953. Identification of montmorillonoids. J. Soil. Sci. 4, 233-237.
GRIFFIN G.M., 1971. Interpretation of X-ray Diffraction Data. Pp. 541-569, in: Procedures in
· Sedimentary Petrology (R.E. Carver, editor), J. Wiley & Sons, New York.
HEY H.H., 1954. A new review of the chlorites. Mineral. Mag. 30, 277-292.
HINCKLEY D.N., 1963. Variability in «cristallinity» values among the kaolin deposits of the Coastal
Plain of Georgia and South Carolina. Clays Clay Miner. 11, 229-235.
JoHNS W.D., GRIM R.E., BRADLEY W.F., 1954. Quantitative estimations of clay minerals by diffraction
methods. J. Sediment. Petrol. 24, 242-251.
MAcEwAN D.M.C., 1961. Montmorillonite Minerals. Pp. 143-207, in: The X-ray Identification and
Crystal Structures of Clay Minerals (G. Brown, editor), Mineralogical Society, London.
MILNER H.B., 1962. Sedimentary Petrography. J. Allen & Unwin, London ..
0RTOLANI F., ToRRE M., Dr NocERA S., 1979. I depositi altomiocenici del bacino di Amantea (Catena
costiera calabra). Bell. Soc. Geol. It. 98, 559-587.
RAISH H.D., 1964. Quantitative mineralogical analysis of carbonate rocks. Texas J. Sci. 16, 172-180.
REYNOLDS R.C., 1980. I nterstratified Clay Minerals. Pp. 249-303, in: Crystal Structures of Clay Minerals
and their X-ray Identification (G.W. Brindley and G. Brown, editors), Mineralogical ~ociety,
London.
RoMEO M., ToRTORICI L., 1980. Stratigrafia dei depositi miocenici della catena costiera meridionale e
della media valle del F. Crati (Calabria). Boll. Soc. Geol. It. 99, 303-318.
ScHULTZ L.G., 1964. Quantitative interpretation of mineralogical composition from X-ray and chemical
data for the Pierre Shale. Prof. Pap. U.S. geol. Surv. 391-C.
SHEPARD F.P., 1954. Nomenclature based on sand-silt-clay ratios. J. Sediment. Petrol. 24, 151-158.
SRODON J ., 1981. X-ray identification of randomly interstratified illite-smectite in mixtures with discrete
illite. Clay Minerals 16, 297-304.
TREADWELL F.P., 1954. Trattato di Chimica Analitica. F. Vallardi, Milano, 2, 543-544.
WEBER F., DUNOYER DE SEGONZAC G., ECONOMOU C., 1976. Une nouvelle expression de la cristallinite de
l'illite et des micas. Notion d'epaisseur apparente des crista/lites. C.R. somm. Soc. Geol. Fr. 5,
225-227:

_...I
Ii
Miner. Petrogr. Acta
yol. 29-A, pp. 661-670 (1985)
Techniques of Analysis for Lithostratigraphic
Correlations in the Subsoil of Milan
V. FRANCANP, L. SCESP, F. VENIALP, A. CANCELLP, F. PREVITALI\
A. FARINP, I. ASSP
1 Istituto di Vie e Trasporti, Sezione geologica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano,
Italia
2
Dipartimento di Scienze della Terra, Sezione miner~logico-petrografica, Universita di Pavia, Via A. Bassi 4,
27100 Pavia, ltalia
3 Dipartimento di lngegneria Strutturale, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano,
ltalia
4 Istituto di Idraulica Agraria, Gestione Risorse Idriche, Conservazione del Suolo, Facolta di Agraria, Universita
di Milano, Via Celoria 2, 20133 Milano, Italia ·
5 Istituto di Chimica Agraria, Faco!ta di Agraria, Universita di Milano, Via Celoria 2, 20133 Milano, Italia
ABSTRACT - A multidisciplinary methodology allowing for correlations in
alluvial deposits is pointed out. A lot of samples, extracted from wells drilled
in Milan (Lombardy Region, northern Italy), were tested, under the
following aspects: geological, mineralogical, chemical, pedological, and
geotechnical. Some weathered levels, marked by an initial stage of reddening,
were recognized in particular at 20 to 25 m and 60 to 65 m. The
genesis of these lev:els can. be ascribed to climatic conditions which were
different from the present ones.
"
Introduction
Even though its geological, hydrogeological
and geotechnical features
have for some time been known
in suffiCient detail, noneth~less the
subsoil of Milan (Lombardy Region,
northern Italy) still presents some
unanswered questions, as regards
genetic and stratigraphic correlations
between lithologically related
levels (FRANCANI & PREVITALI,
1983). This investigation, referring to
samples taken from well drilling car~
ried out for the Milan Wate~ Board,
aims in fact to determine the suitable
characteristics for a reconstruction of
the processes determining the accumulation
and evolution of continental
sediments in the area studied.
Samples were analysed by methods
selected also with reference to a
general knowledge of the geological·
setup of the alluvial materials in the
Po valley and of the palaeoclimatic
events that affected it over the ages
(ALLASON et al., 1984).
The study, still under way; has thus
made it possible, in a first approx-
This research work was spo~sored -by M.P .I.. (Ministry of Public Education of Italy).

'" 1
662 · V. Francani, L. Scesi, F. Veniale, A. Cancelli, F. Previtali, A. Farini, I. Assi
imation, to recognize eolic, fluvial,
fluvio-glaCial and swampy sedimentological
phases, and soil forming,
processes.
Selection of samples
Milan is an extended city (about
100 km 2 ); its subsurface is geologically
formed by sediments coming
from several rivers (Olona, Seveso,
Lambro, etc.). The analysed samples
can be referred to such sediments
(POZZI & FRANCANI, 1981).
There are about 50 pumping plants
with an average of 10 wells each;
--------'-----among--them, .t-wo or three ha-ve been
chosen to outline a selection (Fig. 1).
The three enclosed sections show a
, succession that is schematically represented
in the follow-ing -~~!!:~t!:__
graphic column (see Fig. 2): 0 to 25 m,
, gravel and sand in varying proportions;
25 to 65 m, gravel and ·sandinterbedded
with clay; 65 to 100 m, the
same, but inch.iding more clay levels
and some conglomerates; below 100
m, gray clay with peat and sand
lenses.
Methodology of the study
The tests, analyses, observations
and forthcoming discussions, which
have to be considered provisional
since .the-investigation is still under
way, concerned the following features.
i
NORD
r ,
Fig. 1 - Location of pumping plants and trace of sections.

Techniques of Analysis for Lithostratigraphic Correlations ... 663
gravel and sand
sand with gravel and clay
peculiar levels turned out to be very
interesting; in fact, they show a
marked weathering (proved by
mineralogical analyses) and an evident
redness stage.
Such levels are found all over the
area, only locally interrupted by erosion,
and successive resedimentation,
along the bed of the most important
rivers.
Mineralogical Analyses (F. Veniale)
clay with sand lenses
Fig. 2 _ Representative stratigraphic column.
Geology (L. Scesi)
The enclosed sections (Figs 3, 4, 5)
essentially confirm the lithological
sequence. .
Nevertheless, the presence of some
The mineralogical composition of
the finest soils was determined by
semi-quantitative, X-ray diffraction
methods. Various levels at different
depths can be distinguished, as shown
in Fig. 6.
A good agreement between different
boreholes is found at 20 to 25 m and
' at 60 to 65 m of depth, on the basis of
a more significant abundance of
quartz, feldspar, smectite, vermiculite,
illite and kaolinite.
A relative abundance of the same
minerals was detected at 45 to 50 m,
75 to 80 m and 95 to 100 m beneath
ground level.
2 4
m 3 5
150
Assiano Baggio Tonezza Vercell i I tal ia Anfossi Ovidio Linate·
9 17 18
' 13 6
I 3 5 6 7 18 4 . 16 10
2 19 10 12
bl nk PI · t ·c and Holocenic deposits (fluvioglacial
Fig. 3- Hy~rogeologi~al seAction)·no .. thl. Inbliqaue 'lin~~s ~~~franchian deposits; black dotted lines
Mindel Rtss and Wurm uct. , wt o , .
'
Indicate the I and IT weathered level.
Km

664 V Francanz, · L . Scesi, F. Venza . z e, A · Cance 11. z,. p • Prevztalz, . . A · Farini, !. Assi s
Salemi Assietta
. ""''" ,,_ '""'""".' Luga,no Cenisio Pat-eo Italia
.
m
150
4 710
11 5 13
12 7 12
2 1
16 7 8
12 18 7
3 2 113 15
14 1.7
100
50
0
1
Km
F1g. . 4- H Y drogeological sectiOn . no. 2 (for symbols, see Fig. 3).
'
Novara Chiusabella Oimabue
4 7 10 20 2 20
tso , I J:J
100
50
1
d eological section no. 3 (for sym­
Fig. 5 - Hy rog bols, see Fig. 3).
, . . o 25 m and 60 to
The levels at 2~ th ent in smectite
h ennc m
and
65 m
vermicuhte,
s o': an.
w
hereas
. )
chlorite is
h . h degradatiOn ·
scarce ( Ig d the other levels
are On more the ot·h~r ne i:a~hlorite (lower de­
f d rada tion) · d
gree o eg be correlate
These results c~n . ditions;
"th: a) different chm~tlc con
WI
b) presence of pa 1 eos
oils
.
Chemical · Analyses (A. Farini . and I..
As si)
investigation aims to
The present h ical characteroutline
both the c em
,,
IStiCS . . of the analyse d · sam Pies and
of alteratwn ..
s were car-
their cie.gree --~ ··. · ·1
The following ana ~~grain diamried
out on samples WI (see Table 1):
1 than 2 mm .
eters .. ess . b potentiometnc
H ( determmed Y . d by
p thod); C.E.C. (determmeK Na
me - 8 2); Ca, Mg, '
BaCh at pH.- 1~ CH3COONH4 and
(extracted With . absorption
. d by atomic
determme (AAS) by means of an
spectroscopy . strument).
UNICAM SP 1900 m f Fe indexes of
T he different forms o , deterdegree
of alteratiOn, . · were
mined as follows: I Fe obtained by
F = tota
- er . hydrofluonc . a cid attack on d
sulphunc- 5 m mesh an
les sieved at 0. m
samp 50 oc overnight;
calcined at 4 . oluble Fe de-
- Feo = dithiomte s ethod of
d b the D.B.C. m
MEHRA
termine
& JACKS
Y ON (l 9
60): free Fe
oxides;
F
ble Fe deter-
- oxalate so 1 u ,
:- eo - SCHWERTMANN s
mmed by tive» Fe oxides.
method (196 4 ): «ac determined
F e I . n all extracts . was .
by AAS.

Techniques of Analysis for Lithostratigraphic Correlations ...
- . '
665
..., "'
Vl
,.,
0
::c "'
..., "'
:::
..., "'
'[
0
.

f''"!
666 V. Francani, L. Scesi, F. Veniale, A. Cancelli, F. Previtali, A. Farini, I. Assi
Geopedology (F. Previtali)
The results of the first set of analyses
(in particular, the chemical, granulometric
and mineralogical tests),
together with the first series of macromorphological
observations carried
out on the samples, permit some
deductions which are of interest from
the geological and pedostratigraphic
points of view (Table 1).
First of all, a noteworthy homogeneity
in acidity values and cation
exchange capacities was found at
all depths and- in all wells .. -Ihe~~pK-~
values were constant around neutral
or very slightly acid readings (minimum
pH = 6.50).
C.E.C. values, though varying over
quite a wide range (from 10.5 to 20.5
meq/100 g of soil), show clay minerals
of low activity to be relatively
abundant. The exchange complex
was found to be dominated by the
Ca 2 + ion, with an unexp-ected quantitative
equilibrium between Na+
TABLE 1
Chemical analyses and textures
Bore-hole/Depth pH C.E.C. Ca Mg
--------------'- ---Em~--------(H 2 0~- -(meq/1 00g)-(in 1 N NR4"acetate)
K Na Texture
(meq/100g) (U.S.D.A.)
NOVARA 4
23.5- 24.5 7.10 12.9 10.0 2.3 0.3 0.4 Loamy
33.0- 42.0 7.00 12.9 10.0 2.4 0.2 0.4 Loamy
62.5- 63.5 6.70 20.5 16.5 2.5 0.2 0.4 Clayey loam
76.5- 82.0 6.80 12.5 9.0 2.3 0.3 0.3 Silty loam
NOVARA 7
20.0~ 26.0 6.90 10.9 8.5 1.5 0.2 0.3 Sandy loam
62.0- 65.0 6.50 16.7 11.0 "'1.9 0.2 0.4 Silty clay loam
77.0- 80.0 7.20 11.7 9.5 2.3 0.3 0.5 Silty loam
NOVARA 10
22.0- 24.0 7.10 11.0 10.0 2.0 0.3 0.2 Silty loam
29.0- 39.5 6.90 18.0 11.5 2.0 0.4 0.4 Silty clay loam
61.0- 67.0 6.70 14.9 9.5 1.8 0.2 0.3 Siltyloam
74".0- 75.5 6.90 13.5 10.0 2.3 0.2 0.3 Silty loam
97.5-100.0 6.90 14.5 12.0 2.0 0.5 0.4 Silty loam
CHIUSABELLA 20
16.5- 18.5 7.10 17.4 14.0 2.7 0.2 0.4 Silty loam
22.0- 25.5 6.80 15.5 11.0 2.9 0.2 0.4 Silty loam
31.5-' 35.5 6.90 14.7 11.0 3.1 0.3 0.4 Silty loam
59.0- 61.5 6.90 13.8 9.5 2.1 0.3 0.4 Loamy '
96.0- 97.0 7.20 10.5 9.5 2.0 0.4 .A).4 Silty loam
CIMABUE 20
33.5- 43.5 7.30 11.9 10.0 2,4 0.2 0.4 Sandy clay loam
46.0- 53.0 7.10 10.9 9.5 1.7 0.1 0.3 Silty
60.0- 61.0 7.10 15.1 12.5 2.0 0.3 0.4 Silty loam
MARTINI 3
45.0- 46.0 6.90 12.3 10.0 '2.0 0.3 0.3 Clayey loam
46.0- 50.5 6.90 11.1 10.0 2.0 0.3 0.4 Clayey loam
64.0- 67.0 6.80 16.8 11.5 2.2 0.2 0.5 Silty loam

Techniques of Analysis for Lithostratigraphic Correlations ... 667
and K+ ions. This leads to the supposition
that the ground waters may
have exercised a considerable influ­
. ence over the primary chemical characteristics
of such continental Quaternary
deposits.
The research carried out on the various
forms of Fe (free oxides, amorphous
and crystalline, complex form,
and quantitative ratios between
these) show no immediate correlation
between degree of alteration and
sample depth, but further processing
ofthe data acquired may allow more
far-reaching evaluations, in particular
as regards relationships between
clay minerals and iron oxides (Table
2).
With regard to the results of miner:al~gical
analyses, an important find­
. ing wa,s that two levels (at 20 to 25 m
i and 60 to 65 m) are particularly rich in
smectite-vermiculite, whilst chlorite
is rare. This confirms the colorimetric
observations made on the
samples, showing a redness rating
Bore-hole/Depth (m)
TABLE 2
Chemical analyses of iron forms
Fer Fen Feo
(%of soil)
Fen/Fer
FeJFen
NOVARA 4
23.5- 24.5 2.0 0.66 0.05 0.33 0.08
33.0- 42.0 7.2 2.37 0.07 0.33 0.03
62.5- 63.5 6.6 2.12 0.36 0.32 0.17
76.5- 82.0 4.8 1.10 0.15 0.23 0.14
"
NQVARA 7
20.0- 26.0 5.6 1.22 0.11 0.22 0.09
62.0- 65.0 2.4 1.12 0.08 0.47 0.07
77.0- 80.0 4.6 1.02 0.13 0.22 0.13
NOVARA 10
22.0- 24.0 2.2 0.86 0.02 0.39 0.02
29.0- 39.5 3.4 1.91 0.15 0.56 0.08
6LO- ,67.0 2.2 0.80 0.13 0.36 0.16
74.0- 75.5 3.0 0.87 0.10 0.29 0.11
97.5-100.0 3.2 0.70 0.15 0.22 0.21
CHIUSA.BELLA 20
16.5- 18.5 3.0 1.30 0.23 0.43 0.18
22.0- 25.5 4.8 3:70 0.28 0.77 0.08
.31.5- 35.5 . 3.6• 2.20 0.10 0.61 0.05
59.0- 61.5 3.0 1.40 0.23 0.47 0.16
96.0- 97.0 4.2 0.30 0.03 0.07 0.10
CIMABUE 20
33.5- 43.5 2.2 0.90'. 0.07 0.41 0.08
46.0- 53.0 3.4 0.60 0.07 0.18 0.12.
60.0- 61.0 4.8 1.01 0.12 0.21 0.12
MARTINI 3
45.0- 46.0 3.4 0.50 0.08 0.15 0.16
46.0- 50.5 2.6 0.15 0.06 0.06 0.40
64.0- 67.0 "4.2 0.14 0.02 . 0.03 0.14

jff" I
668 V. Francani, L. Scesi, F. Veniale, A. Cancelli, F. Previtali, A. Farini, I. Assi
which is in fact higher at such depths ..
Also of significance is the strong correlation
between illite content and
the silty-type grain size of certain
specimens, considered as a first
approximation to be loess, perhaps
even laid down. in a lacustrine environment.
Further investigations will aim to
evidentiate and clarify the relationships
existing between reddened
levels and soils covering the terraced
fleistocene surfaces of the plainland
of I,.orp.bardy.
Geotechnical properties (A. Cancelli)
For geotechnical laboratory tests,
a set of 24 remoulded, representative
samples was selected, and split up
into four groups, according.to~thefol--~
lowing criteria:
- soils showing to have been subject
to a past weathering process (red,
br9wn or yellow coloured) were distinguished
from the unweathered,
gray ones;
- «recent» soils (less than 50 m
deep) were distingl!ished from
«ancient>> soils (depth= 50 to 100 m).
From identification tests, the following
conclusions can be drawn:
a) all tested samples can be classified
as, more or less, silty and clay
loams (see triangular classification
chart-"-'- Fig. 7);
b) in regard to weathe~ed levels
(paleosoils?), the deep samples show
Weathered .. 100 0
e z 50 m
.,
{:
iY
I
clay
, .
sandy and
claY loam
.o
•
clay
0
loam
..
•
loam
• ...
silty
loam
"'
-+-% SAND
Fig. 7- Grain size composition, according to the triangular classification chart issued by the U.S.
· Soil Survey Staff (1951).

Techniques of Analysis forLithostratigraphic Correlations ... . 669
finer grain composition, and higher
plasticity, than the shallow ones (see
plasticity chart- Fig. 8-right);
c) also concerning weathered
... levels, the activity of deep samples is
generally higher than in shallow
samples (see SKEMPTON's activity
chart (1953) -Fig. 8-left);
d) possibly, such a different behaviour
can be ascribed to the presence
of a more active clay fraction,
as a consequence of a higher degree of
weathering (cfr. pedological and
mineralogical analyses).
C~mclusions
The aim of the study was to point
out a multidisciplinary methodology
allowing detailed correlations in
alluvial deposits. The analyses of
samples concerned the following
aspects: geological, mineralogical,
chemical, pedological and geotechnical.
The research was mostly devoted
to the identification of weathered
levels interbedded into the alluvial
sequence.
An initial stage of reddening permits
a good correlation among samples
found respectively at 20 to 25 m
and 60 to 65 m of depth. Therefore,
such samples can be assigned to dis-'
tinct.Jevels, only locally interrupted.
This hypothesis needs for further de- .l
tailed studies on larger number of
samples, in order !O be confirmed.
Weathered
• z < 50 m
" z > 50 m
Active
"
Ip (%)
4 0
3 0
Unweathered
o z < 50 m
"' z > 50 m
CH
2 0
CL
0
Inactive
60 50 40 30 20 30 40 50 60 . 7.0 80
Fig. 8 - Right: Casagrande's plasticity chart;. left: Skempton's activity chart (WL = liquid limit;
lp = plasticity index; Cp = fraction finer than 0.002 mm).
•
ML
OL

670 V. Francani, L. Scesi, F. Veniale, A. Cancelli, F. Previtali, A. Farini, I. Assi
REFERENCES
ALLASON B., CANCELLI A., FRANCANI V., PREVITALI F., REPOSSI G., 1984. Nota preliminare sui significato
geologico dei livelli coesivi nel sottosuolo di Milano. Costruzioni XXXIII, 338, Milano.
FRANCANI V., PREVITALI F., 1983. Caratteristiche tecniche e pedologiche dei suoli dei terrazzi ferrettizzati
della Lombardia: il terrazzo di Morazzone (V A). Costruzioni XXXII, 330, Milano.
MEHRA"O.P., JACKSON M.L., 1960. Iron oxide removal from soils and clays by a dithionite-citrate system
buffered with bicarbonate. Clays Clay Miner. 7, 317-327.
Pozzi R., FRANCANI V., 1981. Condizioni di alimentazione delle riserve idriche del territorio milanese. La
Rivista della Strada L, 303, ed. La Fiaccola, Milano.
ScHWERTMANN U., 1964. The differentation of iron oxide in soils by a photochemical extraction with .
acid ammonium oxalate. z. Pfalenzenernlihr., Dung, Bodenkd. 105,' 194-202.
SKEMPTON A.W., 1953. The colloidal «activity» of clay. Pp. 57-61, in: Proc. 3rd Int. Conf. Soil Mech.
Found. Eng., I, Zurich.

!I'
Miner. Petrogr. Acta
Vol. 29-A, pp. 671·680 (1985)
Paleoi1.tological, Mineralogical and Geotechnical
Characterization of Nardo Clays
L. ALBANESE 1 , C. CHERUBINF, M. DI PIERR0 3 , C.I. GIASF, F.M.
GUADAGN0 4 , A. PEDE 2 , F.P. RAMUNNF
1 Via Urbano VI 24, 70124 Bari, Italia
2 Istituto di Geologia Applicata e Geotecnica, Facolta di Ingegneria, Universita di Bari, Via Re David 200, 70125
Bari, ltalia
3 Dipartimento Geomineralogico del!'Universita di Bari, Campus, Via G. Salvemini, 70124 Bari, Italia .
• Dipartimento di Geofisica e Vulcanologia, Universita di Napoli, Largo S. Marcellino 10, 80138 Napoli, Italia
ABSTRACT - As a part of the general background of engineering problems
·related to the utilization of clay formations, this study deals with the characterization
of the clay mass in the Nardo basin (Province of Lecce, southern
Italy) by means of paleontological, geological, mineralogical and geotechnical
analyses. Nardo clays, essentially of the Calabrian age, consist of clay silts
with sands and fall within the range of inorganic, medium-to-high plasticity,
on the Casagrande chart. The compressibility curves e-logp seem to indicate
a preconsolidation pressure of about 5 kg/cm 2 .
Mineralogically, they consist of clay minerals, carbonates, quartz and feldspars;
among the clay minerals, illite prevails over smectite while kaolinite
and chlorite are less abundant; among the carbonates, calcite prevails over
dolomite while quartz is more abundant than feldspars.
·,
Introduction
Geological setting
L.an attempt to provide a technical
. -and scientific contribution, this work
reports the results of a detailed
geotechnical analysis on Nardo clays.!
(Province of Lecce, southern Italy)
(Fig. 1) which was developed starting
from mineralogical and biostratigraphic
investigations and provides ·
data concerning the physical and
mechanical properties of the clay
mass. These data should be used as a
basis for a correct approach to .any
kind of engineering work in the territory.
The clay deposits at Nardo can be
ascribed to the marine sedimentary
cycles which developed in the «Fossa
Bradanica» and in the Apulian foreland
between the Upper Pliocene and
Pleistocene. In addition to outcrops
along the western border of Apulia,
other' much more extended and thicker
outcrops are to be found in the
area corresponding to the «Fossa
Bradanica».
In the Salentine Peninsula, the
clays may be lying directly over the
Mesozoic limestone (Ugento), or they
may be separated from the Mesozoic

'"'"'
672 L. Albanese, C. Cherubini, M. Di Pierro,, C.!. Giasi, F.M. Guadagno. A. Pede, F.P. Ramunni
Foggia
•
Potenza
•
carenites. Despite their shallow
thickness, which is alsoa):'~A!!lLQf~
calcarenite cementation, ground water
in the aquifers may rise as high as
the foundation of buildings at Nardo
due to the fluctuation of the
piezometric level (RICCHETTI &
SCANDONE, 1979).
Fig. 1 - Geographic location of the area studied.
limestones by underlying calcarenites
(Cutrofiano) and make up a
rather thick homogeneous sequence
___________ between the _c~lcarenite~ (Nardo) or
else be arranged in levels, 0.50 to 2 m
thick, between the calcarenites (Maglie
and S. Andrea) (ZEZZA, 1976).
Their presence can be explained by
a more or less powerful subsidence of
depressions of tectonic ongm,
stretching NW to SE, as a result of
events occurring in the areas of the
Apennine Chain and the «Fossa Brad,anica».
At Nardo, the clay complex is a
thick alternation of clay-silty levels of
a grey-blue colour and of silt-sandy
levels varying .in colour from grey to
yellow. The top portion contains yellowish
sand levels with transitional
sedimentary structures.
The levels are approximately subhorizontal.
Their age is Pleistocenic
due to the presence of Hyalinea balthica
at the base. Given the stratigraphy
described above, Nardo clays
provide an impervious bottom for
shallow aquifers in the overlying calfauna
Paleo-environmental considerations
based on the foraininifera micro-
Samples, the same taken for
geotechnical tests, were submitted to
150 mesh screening and the retained
__ p()rt~()n w_as~nalyzed from a micropaleontological
point of view. The
washing residues, ranging between
4% and 8%, were found to consist
essentially of organic matter. In addition
to the foraminifera, small specimens
and fragments of gastropods,
ostracods and echinoids were also
found.
The existing microfauna, generally
well preserved, was analyzed quanti-
- tatively, and the most frequent species
and those of special paleoecologi­
.cal and stratigraphic significance
were recognized.
The samples analyzed revealed
microfauna having quite similar
characteristics. Benthonic foraminifera
appear to be predominant as
they represent approximately. 80% of
the total in all of the samples. The
following species are the most frequent:
Cassidulina laevigata carinata
Silvestri; Cibicides pseudoungerianus
(Cushman); Uvigerina mediterranea

Paleontological, Mineralogical and Geotechnical... 673
Hofker; Uvzgerina peregrlna Cushman;
Melonis barleanum (d'Orbigny);
· Bulimina spp.; Bolivina spp.; Valvulineriay
bradiana (Fornasini); Globocassidulina
oblonga (Reuss); Pullenia
bulloides (d'Orbigny); Pullenia quinqueloba
Reuss.
This prevailing association appears
to be contaminated by coastal species
such as: Textularia calva Lalicker;
Textularia aciculata d'Orbigny;
Elphidiw:n crispum (Linnaeus); Elphidium
macellum (F. & M.); Hyalinea
balthica (Schroeter); Buccilla frigida
(Cushman).
Among the placton species, the following
are by far the most frequently
found: Globigerina qui?'zqueloba Natland;
Globigerina bulloides d'Orbigny;
Globigerina pachyderma (Ehremberg),
while rare specimens of Globo~otalia
· truncatulinoides excelsa (SPROVIE}.U
et al., 1980) were found, though not in
all samples.
The resulting association, the
heavy presence of Uvigerina spp., Bilimiba
spp., Bolivina spp. and Cibicides
pseudoungerianus and the occurrence
ofPullenia spp., Hyalinea balthica and
the Melonis barleanum are indicative
of a sedimentation environment
around 200 meters deep (nerhic environment).
Due to the presence of Hyalinea
balthica in the sampled base, the
whole formation can· be ascribed to
the Pleistocene (GIGNOUX, 1913;
MARTINIS, 1967).
Moreover, due to the presence of
Globorotalia trucatulinoides excelsa
and of the various species of Globigerina,
the formation can ·be
thought to belong to the cold Pleistocene,
starting from the Sicilian
(LAZZARI, 1956).
Grain-size characteristics
The grain-size composition was determined
by wet sieving for the
coarser particles (> 32 Jlm) and by
sedimentation methods for the finer
fractions (

674 L. Albanese, C. Cherubini, M. Di Pierro, C.!. Giasi, F.M. Guadagno. A. Pede, F.P. Ramunni
Clay %
80 20
% Sand 20 40 60 80
Fig. 2- Grain-size distribution of the samples in SHEPARD's diagram (1954).
clay fraction (

The AI and Fe hydroxides consist of
ochre coloured aggregates, almost
amorphous to X-rays, represented by
small reddish, more or less rounded,
masses.
Following the definition of BRAD­
LEY & GRIM (1961), the illiteis a 2M
polytype with a chemism which reveals
low H 2 0 and almost solely AI in
the octahedral sheet (BROWN &
BRINDLEY, 1980; DI PIERRO,.
1981); the AI smectite is dioctahedral
with Ca and Mg as interlayer cations
(BROWN & BRINDLEY, 1980), and
with a high degree of crystallinity (v/
p quite close to 1) (BISCAYE, 1965).
The Fe-chlorite and kaolinite have a
low degree of crystallinity (JOHNS et
al., 1954; HINCKLEY, 1963).
Concerning the relative abundance
(Table 2), the clay minerals (:X ::;:: 53%)
prevail over carbonates (:X = 30%)
and over quartz plus feldspars (:X =
17%).
Among the clay minerals, illite and
smectite occur in greater quantities
with illite (:X = 25%) slightly exceeding
smectite (:X = 19%). There are
Paleontological, Mineralogical and Geotechnical ... 675
much smaller amounts of chlorite
and there is little, if any, kaolinite.
Among the carbonates, calcite prevails
largely over dolomite and Mgcalcite.
Finally, the amount of quartz
is twice that of the feldspars. The
clayey materials examined can be
classified as marls (MALESANI &
MANETTI, 1970) (Fig. 3).
Geotechnical properties
Stratigraphically, the levels sampled
in this study are located below
the contatct between the clays and
the overlying cover, locally consisting
of calcarenites, silt and sand of a
yellowish colour and elsewhere by
«terra rossa>> down to a depth of 7 m.
The samples were first analyzed to
determine their physical characteristics,
according to the A.S.T .M. recommendations
(1979). The water content
(W) ranges between 20.2% and 34.2%
(mean value equal to 27.7%); the dry
unit weight (yd) is between 1.42 g/cm 3
, and 1.71 g/cm 3 with a mean value of
TABLE 2
Mineralogical composition (%)
Sample
m2.2 m 4.4 m4.9 m 5.2 m5.6 m6.2 m 7.0 ·x s
Smectite 25 15 28 19 15 13 18 19.0 5.0
Illite 22 24 22 27 26 26 27 25.0 2.0
Kaolinite 2 3 2 5 3 3 3 3.0 1.0
Chlorite 6 5 6 10 5 5 7 6.0 2.0
Quartz 13 16 12 10 13 14 14 13.0 2.0
Feldspars 3 5 3 4 4 5 4 4.0 11.0
Calcite 25 26 21 19 27 26 22 24.0 3.0
Dolomite 4 6 6 6 7 8 5 6.0 1.0
x: mean value; s: standard deviation

676 L. Albanese, C. Cherubini, M. Di Pierro; C.I. Giasi, F.M. GuadaglJ!l.: A.. Pede, F.P. ,Ril_nu-_mni
carbonates
Fig. 3 - Distribution of the samples in MALESANI & MANETTI'~ diagram (1970). 1: calcarenites;
2: carbonatic sandstones; 3: sandstones; 4: carbonatic siltstones; 5: siltstones;. 6: marls; 7: shales.
Q + F: quartz + feldspars.
4
8
..
.

Paleontological, Mineralogical and Geotechnical ... 677
1.53 g/cm 3 ; the specific gravity of soil
particles is between 2.65 and 2.76
and the mean value is 2.72 ..
The liquid limit (WL) is between
41.6% and 55.7% with a mean value
of 49.6%; the plastic limit (Wp)
ranges between 19.6% and 31.5%
(mean value 25.9%) (Fig. 4).
Furthermore, activity values, according
to SKEMPTON (1953), range
between 0.61 and 0.85. All these data
on physical properties are rather uni-
form and correlate well with the data
obtained from the literature (COTEC­
CHIA, 1971; ZEZZA, 1976).
Compressibility and swelling properties
Clay samples were subjected to
oedometric stresses. This kind of test
can be used to simulate the loading
and unloading cycles which the clay
sediments may have undergone
1.00
e
0.90
0.80
o. 70
0.60
0.50
0.40
0.1
1- -
1- --
-
-
-t-..
-~-t-..
t-t-
----- 1-·
-
1--t- ,...3
0.5
1'---."'
7,
~ I"-.
1'-. 1\
1'-2
6, .........
5
"""
"'
r-,.1\
I'
l::s: I\
r"... -
~ ,\
........ )'... I:'
.....
\\
1\
' "
1\
Fig. 5 - Compressibility curves.
\\
f\. '\
1\ '\ ~
\\ ~
\
10
'
\ .\
\ \ \
\ \J\
1\ 1\'l\
\ '!~
1\
1\
\
p (kg/cmq) 50

· 678, L. Albanese, C. Cherubini, M. Di Pierro, C.l: Giasi, F.M. Guadagno. A. Pede, F.P. Ramunni
throughout their history, starting im- sx 10 3
-
mediately after their initial deposi~
tion (CHERUBINI et al., 1980).
The stress-strain behaviour of clays
against time also were investigated.
The investigation covered the primary
effects during the compression
unloading phases and secondary
effects (viscous strain) during the
compression phase with the related
aging phenomena and the secondary
effects during the unloading phase.
Figure 5 shows the compressibility
curves e - logp for pressure ranges
between 0.1 and 50 kg/cm 2 • The compressibility
curves were studied by
means of Casagrande's method in an·
____________ attempt __ to establish the heaviest
pressure to which the clay mass had
been subjected in the past (preconsolidation
pressure); this value was
found to be between 3.8 kg/cm 2 and
7.0 kg/cm 2 • This possibly means that
the maximum consolidation pressure
was partly due to the cover material
probably removed and, for the most
cas
·OI+-----~~----~--~--~p~(k~g/~cm~q)
0.1 0.4 0.8 12 50
Fig. 7- Cas versus logp for samples 3,5 and 7.
part, to the surface drying of the clay
mass.
Decompression curves are not
shown for lack of space. The field
of the hydrodynamic consolidation
0.016
0.012
•
• •
12x10" 4
10
~
$
~
>
u
0.008
••
..
!
, I
~~~
/. -~
'0.004
•
• •
•• ..
o+-~--~~----~----~_LP~(k~g/~cm~q)
0.1 0.2 0.4.c. o.s__ ,.. 12o .. · -so:
. Fig. 6.- Cv versus logp for samples 3,5 and 7.
Fig. 8 - Cae versus Cc for all samples and three
pressure levels.

Paleont.ological, Mineralogical and Geotechnical ... ' 679
0.12l
ea ss
10
0 "f
0.081
0.061
.
0.04
0.02
.:
p (kg/cmq)
12 50
Fig. 9 - Caes versus logp for samples 2,3,5,6
and 7.
p (kg/cmq)
0+--------.--------~--~~~
0.1 0~ H
Fig. 10- CaesiCs versus logp for samples 2,3,5,6
and 7.
coefficients (Cv) was determined
according to Casagrande's method.
Changes in Cv with logp may provide
further support for the identification
of maximum consolidation pressure.
The specimens examined show " a
gradual increase of Cv up to 3 kg/cm 2
and subsequently a decrease. Precon~
solidation pressure very likely occurs
between these two values. Figure 6
reports Cv variations with logp in
three tests.
The viscous behaviour of the Nardo
clays brought about secondary phenomena
due to increased loading (Cae,
_ Cae coefficients) a.'nd also secondary
phenomena due to decreased loading
(Caes, Caes coefficients). Readings to
obtain the secondary compression
coefficients were taken, at each load- '
ing step, for a period of 7 days and for
longer periods when the swelling
coefficient was surveyed. Figure 7 reproduces
the broken lines Cae - logp
for three samples. The trend rises
considerably at about 50 kg/cm 2 • The
chart in Fig. 8 shows the relationship
between Cae and Cc. The corresponding
experimental points are contained
inside a rather clearly defined
band with CaeiCc ratios that are sufficiently
steady and in the order of 0.05
± 0.02, in agreement with the data
reported in the literature.
For the unloading phase, the curves
Caes - logp are reported in Fig. 9;
these broken lines indicate that, as
the loading pressure drops, the
values of Caes increase. Similarly,
there is an increase in time Tp which
marks the end of the primary swelling.
In fact, with unloading, T/s vary
from 40 to 120 minutes for a pressure
of 6 kg/cm 2 , from 119 to 446 minutes
for 0.8 kg/cm 2 and from 655 to 2100
minutes for 0.1 kg/cm 2 • Figure 10
sums up the viscous behaviour of the
samples during unloading; the ratio
CaesfCs with logp shows a marked
increase with decreasing effective
pressure.

l
680 L. Albanese, C. Cherubini, M. Di Pierro, C.!. Giasi, F.M. Guadagno. A. Pede, F.P. Ramunni
REFERENCES
A.S.T.M., 1979. Annual Book of A.S.T.M. standards. Part. 19, 560 pp.
BISCAYE P.E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and
adjacent seas and oceans. Geo!. Soc. Am. Bull. 76, 803-832.
BRADLEY W.F., GRIM R.E., 1961. Mica Clay Minerals. Pp. 208-241, in: The X-ray Identification and
Crystal Structures of Clay Minerals (G. Brown, editor), Mineralogical Society, London.
BROWN G., BRINDLEY G.W., 1980. X-ray Diffraction Procedures for Clay Mineral Identification. Pp.
305-359, in: Crystal Structures of Clay Minerals and their X-ray Identification (G.W. Brindley
and G. Brown, editors) Mineralogical Society, London.
CHERUBINI C., RAMUNNI F.P., WALSH N., 1980. Ef{etti nel tempo della variazione delle sollecitazioni
applicate all'edometro su campioni indisturbati di argille subappennine. Geo!. Appl. Idrogeol. 15,
376-392.
CoTECCHIA V., 1971. Su taluni problemi geotecnici in relazione alia natura dei terreni della regione
pugliese. Riv. Ita!. di Geotecnica I, 2, 1-32, Napoli. .
DI PIERRO M., 1981. Caratteri composizionali delle argille pleistoceniche della zona di M{glionico (MT).
Rend. Soc. It. Min. Petr. 37, 229-240.
GIGNOUX M., 1913. Les formations pliocenes etquaternaires de l'Italie du Sud et de la Sicile. Ann. Univ.
Lyon, n.s., Se., Med., fasc. 36, 283-286.
GRIFFIN G.M., 1971. Interpretation of X-ray Diffraction Data. Pp. 541-569, in: Procedures in
Sedimentary Petrology (R.E. Carver, editor), J. Wiley & Sons, New York. ·
HINCKLEY D.N., 1963. Variability in «crystallinity» values among the kaolin deposits of the Coastal
Plain of Georgia and South Carolina. Clays Clay Miner. 11, 229-235.
JoHNS W.D., GRIM R.E., BRADLEY W.F., 1954. Quantitative estimation of clay minerals by diffraction
methods. J. Sediment. Petrol. 24, 242-251.
--~---- ~--~- LAZZARI. A.,-1956. Ccmtribut{iilla conoscenza del Pleistocene della provincia di Lecce -1} La microfauna
delle·argille sabbiose diNardo. Mem. Ist. Sup. Se. Lett. S. Chiara 8, 345-362, 1 tav., Napoli.
MALESANI P .G., MANETTI P ., 1970. Proposta di classificazione dei sedimenti clastici. Mem. Soc. Geol.
It. 9' 55-63.
MARTINIS B., 1967. Sull'eta delle.argille di Gallipoli (Lecce). Rend. Accad. Naz. Lincei 42, serie VIII.
MILNER H.B., 1962. Sedimentary Petrography. J. Alien & Unwin, London.
RAISH H.D., 1964. Quantitative mineralogical analyses of carbonate rocks. Texas J. Science 16, 172-
180. '
RrccHETTI G., ScANDONE B., 1979. Inquadramento geologico regionale della Fossa Bradanica. Geo!.
·•I
I
Appl. Idrogeol. 14, parte Ill, 276-281.
RrviERE A., 1977. Methodes granolometriques; Techniques et interpretation. Masson et ci•, Paris.
SHEPARD F.P., 1954. Nomenclature based on sand~silt-clay ratios. J. Sediment. Petrol. 24, 151-158.
SCHULTZ L.G ., 1964. Quantitative interpretation of mineralogical composition from X-ray and chemical
data for the Pierre Shale. Prof. Pap. U.S. geol. Surv. 391-C.
SKEMPTON A.W., 1953. The colloidal «activity• of clay. Pp. 57-61, in: Proc. 3rd Int. Conf. Soil Mech.
Found. Eng., I, Zurich:
SPROVIERI R., RuGGERI G., UNTI M., 1980. Globorotalia Truncatulinoides excelsa n. subsp. foraminifero
planctonico guida peril Pleistocene inferiore. Boil. Soc. Geol. It. 99, 3-11.
ZEZZA F., 1976. V alutazione geologico-tecnica degli Ammassi rocciosi carsificati con particolare riferimento
alle aree carsiche pugliesi. Mem. Soc. Geol. It. 14, 9-34.

Miner. Petrogr. Acta
Vol. 29-A, pp. 681-692 (1985)
Effects of Particle Geometry on Treatment
and Processing of Clays
R.A. KUHNEL
Department of Mining Engineering, Delft University of Technology, 120 Mijnbouwstraat, the Netherlands
ABSTRACT - A variety of shapes have been recognized on clay minerals as
crystals, crystal fragments and as aggregates. Any non-spherical particle
behaves differently in comparison with the behaviour of a sphere. Shape
factors are numerical expressions for particle geometry. These are often derived
from their relationship to sphere. Effects of shape factors are important
for flow behaviour, moreover, they also imply numerous technological processes.
Non-spherical particles tend to a natural segregation and/or preferred
orientation. Because of physical anisotropy of all crystals, any aggregate
with a degree of preferred orientation shows some degree of imisotropy in a
variety of physical and chemical properties. ·
This paper gives a survey of different particle geometries, shape factors and
examples of technological implications connected with preferred orientation
and anisotropy of aggregates. Also a survey of techniques for the examination
of particle geometry and for. the quantification of preferred orientation of
aggregates is discussed.
Particle (pore) analysis
Since the introduction of electron
microscopy in clay research, various
shapes have been recognized for clay
minerals. To the pioneers in this field
belong H. BEUTELSPACHER &
H.W. van der MAREL (1968). The
shape of clay minerals has become
diagnostic for the identification of
clay minerals, for instance fibrous
sepiolite and palygorskite, bladed
rectorite · and tubular halloysite,
while others (micaceous clay minerals,
kandites, chlorites, etc.). are
generally tabular. An isometric (spherical)
shape is not frequent for clay
minerals, although it does occur for
some common aggregates and nonphyllosilicates.
Examples of some
characteristic shapes of clay minerals
are shown in Figs 1 and 2. Aggregates
of isometric particles are easier for
all kinds of technologies because .of
the isotropic character of the products.
Nevertheless, the non-spherical
particle geometry and preferred
orientation in some instances can
improve properties of the aggregates
e.g. in refractories, laminated or fibrous
composites.
Particle (pore) analysis has recently
developed into a means of comprehen-

"!
682 R.A. Kiihnel
Fig. 1- Examples of different shapes of clay minerals. Photomicrographs TFDL Wageningen. a)
SEM photomicrograph. Spherical bodies of opal, Greece. b) TEM photomicrograph. Globular
halloysite, Italy. c) TEM photomicrograph. Tubular halloysite, Spain. d) TEM photomicrograph.
Fibrous nickeliferous sepiolite, Indonesia.
0.2JJm
Fig. 2- Examples of different shapes of clay minerals. Photomicrographs TFDL Wageningen. a)
TEM photomicrograph. Flat pseudohexagonal crystals of kaolinite, Brazil. b) SEM photomicrograph.
Bladed serpentinite and fibrous goethite, Philippines.

Effects of Particle Geometry on Treatment ... 683
sive particle characterization. In 1984
appeared the first volume of a new
international periodical entitled
«Particle Characterization» dedicated
to that important technological
problem. Particle (pore) analysis examines
particles from the four following
viewpoints:
1) Particle (pore) size distribution:
Population of particles is specified in
terms of central tendencies (mode,
mean and median), dispersion (standard
deviation, sorting), asymmetry
(skewness) and kurtosis (peakedness);
2) Particle (pore) geometry: By
means of.different shape factors morphological
features of crystals, fragments
and crystalline aggregates are
numerically expressed;
3) Surface quantity and quality:
Specific surface area gives the 'extent
of particle surfaces per weight, wiiile
surface quality quantifies different
kinds of surfaces such as crystal
planes, cleavages, fractures etc. including
the surface morphology;
4) Inner fabrics: From this point of
view are specified aggregates which
are either of a single-phase or multiphase
composition. Moreover, the
geometry of mutual spatial arrangement
and/or intergrowth is of importance.
In points 1) and 2) also pores and
voids are mentioned. The microfabric
image will not be complete without
specification of pore size distribution
and pore geometry. Both parameters
control the behaviour of hetero-
. geneous systems such as rocks, sus­
,pensions, and aerosols, ··as regards
permeability, conductivity and other
important properties.
Shapes and shape factors of clay
minerals
Any three-dimensional body can
be characterized by a number of
dimensions. Spheres and cubes for
instance can be characterized by
one dimension only. Therefore, spheres
and cubes and related shapes are
called «isometric». A prism, a rod, a
hair all show an isometric character
as regards cross section but not as regards
length. We can call such particles
«two-dimensional>>. A similar
situation exists for tablets and discs.
Blades and bricks must be specified
by three dimensions. Ideal geometric
forms are easier to quantify. But
irregular angular or rounded particles,
often with a pitted and ragged
surface, present a more complex
problem. However, if a particle can
be enclosed between three pairs of
parallel planes (a parallelopiped with
minimum volume), the dimensions of
such bodies characterize the enclosed
particle properly.
Besides combinations of dimension-ratios,
also other measures
are applied for shape factors.
For example, perimeter and surface,
and area and volume of particular
sections or particles have important
roles. Surveys of shape factors
and their sensitivities are published
in sedimentological and/or stereological
references (e.g. BARRETT,
1980; MORTON & McCARTHY,
1975).

684 R.A. Kuhnel
Simple shape classification can be
derived from ratios of L, I and S­
dimensions (measures) as shown in
Table 1.
Among the most popular factors in
petrology and sedimentology are the
following:
Elongatior;t factor: t = I/L, also
used as life
Flatness factor: fr = 2S/(L+ I), also
used as 1/ff
Sphericity: 'P = VpNL or Sp/SL
where V stands for the volume of the
particle (p) and the volume of the circumscribed
sphere (L), and S for particular
surfaces respectively. In the
____ ________ case qf a sphere, all dimen_sions are .
equal and all shape factors are equal
to one. Any deviation of the particle
geometry from that of a sphere lowers
·the value ofthe shape factors. Despite
that we speak about high shape
factors.
Concept of anisotropy of aggregates
The concept of anisotr-opy is based-. -.
upon the following statements:
- All crystals of any size are anisotropic
in their properties (chem~cal
and physical properties are vectors).
Only completely . randomly
oriented particles form an isotropic
aggregate.
- Due to any degree of preferred
orientation, an aggregate becomes
anisotropic.
Any non-spherical particle tends to
reach equilibrium with the environment.
Starting from nucleation and
crystallization through displacements
up to mechanical rearrangement
and recrystallization under
high pressures and temperatures, the
position of particles expresses the
equilibrium between particle and all
co-existing driving forces. When conditions
are changed, the position of
particles follows the path to a new
TABLE 1
A simple classification of particle shapes (modified accordin_g_ to ZINGG, 1935)
SHAPE
CONDITIONS
ISOMETRIC
(MONO- DIMENSIONAL)
L;r;s .!>~:~>3:
L 3 I 3
ELONGATED
(TWO- DIMENSIONAL)
_ I 2 5 2
L>I=S --
L 3 1 3
EXAMPLES OF:
GEOMETRIC FORMS
f-(,..._-_-_-_-_-_-..::;0/II s
FLAT / ?I
(TWO-DIMENSIONAL) ~I
L;l>S~>~ :~I>S-

Effects of Particle Geometry on Treatment ... 685
steady equilibrium. Therefore, parti­

-··:r.·;-,c::
-- --------------~- -·- --------~. ------~ -=---=------------------------ ------------- _J;.· -------- ---
---=~
-------------­
·-·-·-------··
! .
a-.
00
a-.
TABLE 2 .
Methods for examination of particle geometry and preferr~d orientation of particles in aggregates
Method
Driving forces (measures)
Advantages/disadvap.tages
Optical
microscopy
(image analysis)
direct measurement of
particles
suitable for particles and grains larger than 5 micrometers;
suitable for particles, grains and voids;
quantitative data on oriented preparations only;
necessity of stereological recalculations on images
Electron microscopy
image analysis
SEM + TEM
X-ray diffraction
direct measurement of
particles and voids
line intensities on oriented
preparations
polar diagrams
suitable for submicroscopic particles and inner voids;
qualitative and semiquantitative data on SEM;
quantitative data on TEM;
necessity of stereological recalculations on images
suitable for rocks and other aggregates;
oriented preparation required;
necessity of internal standards (e.g. MoS 2 )
~
~
?

Effects of Particle Geometry on Treatment ... 687
amined, and spatial variability of
properties is measured as a function
of preferred orientation. Summarized
in Table 2 are techniques available
for determination of shape and of
preferred orientation of particles in
suspensions and aggregates with
their capacities.
Microfabrics of clayey sediments
During sedimentation from suspension,
a large fraction of flaky clay
particles establish their equilibrated
position subparallel with the bottom.
Due to the mutual meshanical and
electrostatic interaction a complete
parallel P?Sitioning is never reached.
Clay particles are surrounded by
hydration (solvation) layers which
compensate the charges and surface
energy. During the whole postsedimentary
development (both diagenetic
and metamorphic), the microfabric
undergoes drastic changes.
Due to compaction, particles come in
mutual contact, so that porosity, pore
size distribution and pore geometry
change completely. The rearrangement
of particles with higher shape
factors requires higher activation
energy and the degree of displacement
does not always lead to an improvement
of preferred orientation.
Without any doubt, microfabrics
control mechanical properties of,
sedimentary rocks. Therefore, sedimentologists,
engineering geologists
and civil engineers. follow this complex
problem thoroughly by means of
the most advanced techniques.
Mathematical models of compaction
have been designed and particular
stages of microfabric development
have been recorded on scanning electron
microscope photomicrographs.
An excellent survey of these was
given by F. VENIALE during this
Congress.
Microfabrics also reflect a kind of
sedimentation. It would be possible
to recognize submarine mudflows,
turbidity currents of different density
and spee_d as well as landslides and
any partial displacements of soils on
unstable slopes. However, the primary
prerequirements are undisturbed
oriented samples and oriented
sections. In addition to that it is of
importance to know the distribution
of shape factors on particular granulometrical
and mineralogical fractions.
Technological implications
The shape of the particles and preferred
orientation strongly affect
different processes during the treatment.
Both, advantages and disadvantages
of these phenomena are
known, however, prevailing disadvantages
often imply technologies.
Adhesion of flaky particles to the
parts of excavation and transporting
machines is a well-known implication
in winning, transporting and
storage of ceramic raw materials,
especially in the partly wetted state.
Sticking of clays results from preferred
orientation of non-spherical
particles with a large surface area,

688 R.A. Kuhnel
and of course of their charges. Par.ti~
des reach the most stable position
parallel to the surface of tools or containers.
It is impossible to change the
nature of such materials. Therefore,
the solution of that problem lies
rather in modification of adjacent
surfaces.
Similar problems are more pronounced
in classification (screening)
processes where the more common
presence of moisture often causes
closing of meshes.
The comminution (grinding and
milling) by means of different instrumentation
should result in the generation
of larger surfaces. However,
preferred orientation of flakes to the
··------surface·of-baHs·, pebble·s; rods-or ham-·
mers causes the most elastic crystal
planes to be exposed to the impacts
and more elastic deformation than
breakage takes place. Subsequently,
energy for comminution is used with
little effect.
During sedimentation, all nonspherical
particles do not obey
Stokes' law and their settling velocities
are directly controlled by shape
factors. During elutriation, in air
or in liquids, particles with the same
weight behave differently according ·
to their shape factors. The shape of
particles strongly effects the flow behaviour
of powders, pastes, slurries
and suspensions. Due to the different
settling velocities and charge distribution,
particles segregate continuously
during the movement and
establish aggregates with a rather
high degree of preferred orientation
and grading. All kinds of forming processes
such as molding, slip casting,
pressing and extrusion are~

(
p
Effects of Particle Geometry on Treatment ... 689
Fig. 3- Negative photomicrograph, axial section through a sewage pipe. Photomicrographs TFDL
Wageningen. Parabolic fissures in the central part result from differences in flow speed during the
extrusion. Paste flows faster in central part while close to the mouth piece retardation occurs due
to higher adhesion of flaky particles in preferred orientation.
Fig. 4- SEM photomicrograph (TFDL Wageningen). Fabrics of green body (sewage pipe). Flaky
particles show high degree of preferred orientation (lineation).

690 R.A. Kuhnel
Fig. 5 -
SEM photomicrograph (TFDL Wageningen). Fabrics of fired body (sewage pipe). Subparallel
distribution of fissures (lamination) caused by anisotropic shrinkage.
products in so far as they lower the
permeability of ceramic bodies;
further water penetration might result
in sheeting decay.
Another troubling effect of shape
can be recognized on filtering. Particles
in suspension are uniformly
oriented towards the pressure gradient
and cake on a filter becomes
dense with the lowest permability
against the driving force.
Numerous other examples can be
given in order to demonstrate the
consequences of particle geometry.
Technology attempts to modify the
anisotropic clayey material by
numerous treatments. For instance,
destruction of preferred orientation
by spray drying is one of the successful
techniques. Droplets of clay suspension
are dried and the inner structure
of resulting granules is highly
random. The tendency to preferred
orientation is depressed and shrinkage
on drying and firing can be more
easily controlled. Admixing of
isometric and irregular pa~ticles (e.g.
saw dust) with suspensions to be filtered
provides higher permeability of
thicker cakes on filters. The life of the
filter is extended and also the capacity
is increased.
The shap~ of the particle and preferred
orientation can also have

Effects of Particle Geometry on Treatment ... 691
Fig. 6 -
SEM photomicrograph (TFDL _Wageningen). Detail of lamination (parallel fissures) in
fired sewage pipe.
-·-"
favourable effects. For instance, the
quality of paper depends on microstructure
and preferred orientation of
kaolinite crystallites within. the paper
coating. Shiny submetallic lustre
of plastic coatings depends on the degree
of preferred orientation of flakes
of micas or other fillers. In the case of
aggregates consisting of highly anisotropic
crystallites it is possible to
exploit the optimum (maximum)
properties by control of orientations. ·
In such cases technology seeks to prepare
powders of required size and
shape and aggregates with required
orientation. Applications of such
materials could be found among refractories
and insulating materials,
reinforced composites, electroceramics,
magneto-ceramics, abrasives
etc. Mechanical properties of
ceramic bodies are improved by
mutually penetrated and intercalated
non-spherical particles. These
are trends in the development of new
composites, laminates and fibre reinforced
materials.
Conclusions
Shapes of particles control their
behaviour during any treatment.
Non-spherical particles tend to riatu-

,, I
I
li
692 R.A. Kii.hnel
.I
ral segregation and preferred orientation
and cause anisotropy of aggregates
and/or products. Shape and
orientation have both, negative and
positive effects on products. It is desirable
to recognize different shapes
in granulometric and also in mineralogical
fractions of the raw materials.
Furthermore, it is desirable to quantify
shapes and their distribution by
means of sensitive shape factors and
to quantify the degree of preferred
orientation. When the behaviour of
particular clayey particles is understood,
it is easy to optimize the technology,
by depressing the negative
effect and favouring the positive
ones. For examination it is possible to
modify techniques already applied in
sedimentology and stereology. These
offer a variety of approaches for individual
particles, as well as for bulk
materials. A development of new
techniques is expected. Controlled
oriented aggregation is a prerequirement
for all powder technologies.
REFERENCES
BARRETT P.J., 1980. The shape of rock particles, a critical review. Sedimentology 24, 291-303.
BEKKER P.C.F., KDHNEL R.A., 1983. Investigation of lamination phenomena on vitrified sewage pipes.
Science of Ceramics 12, 107-115.
BEUTELSPACHER H., VAN DER MAREL H.W., 1968. Atlas of Electron Microscopy of Clay Minerals and
their Admixtures. Elsevier, Amsterdam.
McCRONE, W.C., BROWN J.A., STEWART I.M., 1980. The Particle Atlas. Vol. VI, Ann. Arbor. Science
Pub!., Michigan, USA.
GARD J .A.( editor), 1971. The Electron-Optical Investigation of Clays. Mineralogical Society, London.
MORTON R.R.A., McCARTHY C., 1975. The Omnicon TM pattern analysis system. Microscope 23, 239-
260.
Suoo T., SHIMODA S., YOTSUMO Y., AITA S., 1981. Electron Micrographs of Clay Minerals. Develop- .
ments in Sedimentology 31, Elsevier, Amsterdam.
VENIALE F., 1985. The Role of Microfabric in Clay Soil Stability. These Proceedings.
ZINGG TH. W., 1935. Beitrag zur Schotteranalyse. Schweiz. Min. u. Petr. Mitt. Bd. 15, 35-140.
':'l ,,,
11
11
I' .I

(
,.
Miner. Petrogr. Acta
Vol. 29-A, pp. 693-702 (1985)
On Some Characteristics of Compacted Cohesive Soils
· G. DENTE, L. ESPOSITO
Dipartimento di Difesa del Suolo, Universita degli Studi della Calabria, 87036 Arcavacata di Rende, Italia
ABSTRACT- The permeability and swelling pressure values of two compacted
cohesive soils from Avellino and Catanzaro Provinces (southern Italy)
were determined in order to examine their engineering behaviour related to
core earth dam construction.
These properties are strongly influenced by the molding water content. In
particular, the swelling pressure is the result of the action of both mechanical
and osmotic components. The osmotic component depends mainly on
clay mineralogical composition and the adsorbed cations.
The variations of soil microfabric with molding water content were observed
using scanning electron microscopy and are in agreement with the behaviour
of both permeability and swelling pressure.
Introduction
When soil is used as a construction
material it is treated by means
of special techniques which improve
both its shear strength and compressibility.
Compaction is one of the tech-
. -nique most commonly used.
Some authors have suggested that,
due to a constant compactive effort,
the structure of soil can be changed
oy varying the water content (LAM­
BE, 1958; SEED & CHAN, 1959).
When materials are drier than the ·
optimum, the structure is random or
· flocculated, whereas when they are
wetter than the optimum the structure
is oriented or dispersed. Recent
studies have established tha:t the clay
particles are assembled into structural
units called domains, clusters and
peds. These structural units are arranged
in frameworks described as
random (opened structure), flocculated
(closed structure) or dispersed
(oriented structure). Whenever the
framework of a soil is random the volumetric
behaviour is isotropic, whilst
when it has a totally 'oriented structure
the bulk behaviour is anisotropic.
In describing the structural units
BARDEN & SIDES (1970) have followed
the . indications of LAMBE
(1958): when the water content is low
,the structural units are hard and not
distorted by the compactive effort,
with the result that the density is low
and many macropores are to be
found between the structural units
(opened structure). An increase in the

694 G. Dente, L.Bsposito
water cop.tent causes the structural
units to become progressively softer
so that they are distorted by compaction,
the macropores disappear and
the density increases (closer and partly-oriented
structure). When the water
conte~t is high the density decreases
since the water cannot replace the
air entrapped in the isolated pores
(oriented structure) with the result
that some solid partiCles disappear.
This paper reports the results of
laboratory tests which measured the
permeability and swelling pressure
of some samples of compacted cohesive
soils.
-- --
Material and methods
The soils, designated A and B, belong
to the top of a fluvial deposit
close to the Conza dam (Avellino Province)
and the middle part of the
(ypical S. Anna stratigraphic sequence
(Catanzaro Province). Sampling was
done in order to obtain material to
be utilized for construction of the dam
cores. '-~.
The experimental methods include
. the following steps:
(i) Compaction, utilizing the A.A.S.H.
0. standard technique (AMERICAN
SOCIETY FOR TESTING MATE­
RIALS, 1956).
(ii) Measurement 0f swelling pressure
(sp), utilizing a Geonor rigonfimeter.
(iii) Measurement of permeability
coefficient (K), utiliziiJ,g __ Il: _ _Q~QnQI"~
permeater(I).
(iv) Control of soil B . microfabric
after compaction by means of scanning
electron microscopy (SEM).
In the case of swelling pressure,
two different techniques were used:
- the so-called «Standard test>>, regarding
immersion in water to
obtain sample 'saturation;
.-the so-called «as compacted test>>,
relative to saturation after a first stage
in which the water content of the sample
is kept constant with the same
value obtained after its compaction.
For soil B, the permeability tests
consider flow in a vertical direction,
k~, i.e. parallel to the direction of the
compactive effort, and in a horizontal
direction, kh, i.e. normal to the
direction of compactive effort.
Results and discussion
The plastic properties, minerq.logical
composition and cationic concentration
of the less than 2 )liD fraction
for the soils studied are reported in
Table 1 .
The values of the dry density Yd vs ..
molding water content for soils A and
B are reported in Fig. 1.
The variation occurring in the
structural arrangement of· soil B
when the water content increases is
(1) The equation K = Yw ;• e 3 where ll = viscosity of permeant; c. = shape factor; Yw
ll R l+e . .
= unit weight of water; e = void ratio; s = degree of saturation; R = ratio between wet
surface and volume of the solid particles, derived by Darcy's Law, is not utilized because of
the considerable discrepancies with the experimental results. ·

On Some Characteristics of Compacted ... 695
TABLE 1
Plastic properties, mineralogical composition and cationic concentration of the < 2 Jtm
fraction of the soils studied
WL Wp lp la Smectite
Illite
Kaolinite Na+ Ca 2 + Mgz+
+ Chlorite
(meq/100 g)
Soil A 59.3 21.4 37.9 1.5 79
Soil B* 45.5 22.0 23.5 0.9 10
12 9 6.52 2.32 0.53
60 30 4.32 1.30 2.13
* Chlorite is absent in Soil B
shown in Figs 2, 3 and 4, in agreement
with the hypotheses of BARD EN
& SIDES (1970).
The sp values obtained by means
of the ;,standard test» are reported in
Figs 5 and 6, where the maximum
value is reached for a water content
less than the optimum relative to closed
and partly-oriented structures.
BOLT (1956) has explained the·swelling
of clay soil only in terms of''the
osmotic pressure. But since BOLT's
theory is only valid for totally oriented
structures it is unable to explain
these experimental results. It is there-
fore clear that the swelling pressure
is partly due to the soil-water
potential (mechanical component)
and partly to osmotic pressure. This
hypothesis (A YLMORE & QUIRK,
1960) enable the experimental results
to be satisfactorily interpreted.
For «as compacted» samples (Figs
7 and 8) the behaviours of materials
A and B differ. In the case of soil A,
the swelling pressure in the first
stage is only exerted by those samples
whose degree of saturation approaches
unity. Under this condition the
soil-water potential approaches zero,
2.0
1.9
1.8
...
I
1.7
w optimum
Fig. 1 --Compaction curves: (a) soil A, (b) soil B.,

696 G. Dente, L. Esposito
Fig. 2- Soil B microphotograph (w = 13%).
Fig. 3 - Soil B microphotograph (w = 14.7%).

On Some Characteristics of Compacted ...
697
Fig. 4- Soil B microphotograph (w = 18.5%).
sp
(kg/cm2)
0
I
0
/
0
·~
0~ 0
~0
---
w%
w optimum
Fig. 5 - Swelling pressure versus water content for soil A.
(

698 G. Dente, L. Esposito
sp
( kg/cm2)
0
0
/
w%
0+-----r----,-----,-----,----,-----,---T'
8 10 11 12 13 14 15
w optimum
Fig. 6- Variation of the swelling pressure with water content for soil B.
thus the measure of swelling pressure
·--·-·r--is entirely due to osmotic pressure
(DENTE & ESPOSITO, 1984). In the
case of soil B, swelling pressures are
only exerted by those samples whose
water content approaches 80% of the
optimum, i.e. when the water content
is low. Under this condition • the
osmotic pressure approaches zero
and the swelling pressure measured
sp
(kg/cm2)
0
• as compacted
o with water
4
/
I
i
/
/
0
I
I 9
.... ·-I.
w optimum
Fig. 7 - Swelling pressure of samples «as compacted>> for soil A.

0
8
w optimum
/
On Some Characteristics of Compacted ... 699
"' as COilJpa"cted
Fig. 8 - Swelling pressure of samples «as compacted>> for soil B.
is entirely due to the soil-water potential.
In the second stage both soil
. samples achieved the same pressure
values as those called «standard>>.
The different behaviour is primarily
\
kv
(cm/sec)
~\
~
r-·
_1
'
due to the different clay minerals
present, although in both soils the
cations adsorbed are essentially the
same (BOWLES, 1979).
Figures 8 and 9 show that the per-
'
~
'
gr- ·-
I
~-...... . t--
~'.~t=:::e=
0 w%
7 9 11l 13 15
w optimum
Fig. 9 - Variation of permeability co€Jficient kv with water content for soil A.

700 G. Dente, L. Esposito
-6
1 ·1 0
J
k
(cm/sec)
- --
~"'-:"'
~-~
-~}

On Some Characteristics of Compacted ... 701
part of the macropores disappears
(Fig. 4). Obviously, the variation in
pore size and the disappearance of
macropores determine the decrease
of K values (OLSEN, 1962; YONG &
WARKENTIN, 1975).
For soil B, the permeability coefficients
determined in vertical (kv) and
horizontal (kh) directions, assume
the same values for low water content
confirming the isotropic behaviour
of the microfabric. At high water
contents, the kv and kh values are
different because of the anisotropy
assumed by the structure. In particular,
the degree of anisotropy, defined
by kvfkh, is low (Fig. 10). In all probability,
the small increase inK values
from w values greater than the optimum
ones can be due to an increase
. in the size of the micropores. ,.
Conclusions
Based on the results obtained, it
can be concluded that the permeability
of compacted cohesive soils depends
mainly on the structure assumed
by the materials after compaction
and, consequently, is to be considered
essentially a function of the
water content. This dependence, hypothesized
for various materials by some
researchers since 1960, has been illustrated
by scanning electron microscopy.
The experimental results obtained
indicate that the swelling pressure
depends on both mechanical and
osmotic components, as stated by
AYLMORE & QUIRK (1960). This
fact is particularly evident on the basis
of the tests relative to «as compacted»
soils. In particular, tl)e osmotic
component, influenced by mineralogical
and chemical-physical properties,
is negligible for soil B because of
its low smectite content.
Acknowledgments
The writers wish to express their
thanks to Prof. C. Buondonno for mineralogical
and chemical-physical
determinations, Prof. P. 0:::-sini for
permission to use the electron microscope
and Prof. A. Pozzuoli for critical
reading of the manuscript.
REFERENCES
AMERICAN SOCIETY FOR TESTING MATERIALS, 1956. Soil Testing.
AYLMORE L.A.G., QuiRK J.P., 1960. The structuraistatus of clay system. Clays Clay Miner. 9, 104-130.
BARDEN L., SIDES G.R., 1970. Engineering behaviour and structure of compacted clay. ASCE 96, n.
SM4, 1171-1200.
BoLT G .H., 1956. Physical-chemical analysis of the compressibility of pure clay. Geotechnique 6, 86-
98.
BowLES J.E., 1979. Physical and Geotechnical Properties of Soils. McGraw-Hill, New York.
DENTE G., EsPOSITO L., 1984. Permeabilita e pressioni di rigonfiamento dei terreni coesivi costipati.
Rivista Italiana di Geotecnica 18, 159-171.
LAMBE T.W., 1958. The engineering behaviour of compacted clay. ASCE 84, n. SM2, 681-717.

"~'I!
''li ::I,
''
MITCHELL J.K., HooPER D.R., CAMPANELLA G.R., 1965. Pennecibility of compacted clay. ASCE 91, n.
SM4, 41-65.
OLSEN H.W., 1962. Hydraulic flow through saturated clays. Clays Clay Miner.n, 13Fr6r:-·~--· ---­
SEED H.B., CHAN C.K., 1959. Structures and strength characteristics of compacted clays. ASCE 85, n.
SMS, 87-109.
YoNG R.N., WARKENTIN B.P., 1975. Soil Properties and Behaviour. Elsevier, Amsterdam.
'
702 G. Dente, L. Esposito

I
..-J7
Abstracts
703
Physical and Mechanical Properties
of Silica-Kaolin Mixtures
R. GENEVOIS, P.R. TECCA
Istituto.di Geologia e Paleontologia, Universita di Roma, Piazzale A. Moro 5, 00185 Roma, Italia
This paper presents the results of a research on the influence of non-clay
particles on the behaviour of cohesive soils. For this purpose, the physical
and mechanical properties of kaolin mixtures with increasing percentages of
amorphous silica were analysed. A purified kaolin provided by the german
Industry BSH was utilised: five mixtures were prepared with increasing
percentages of fumed silica up to 40% of total dry weight; laboratory tests
were performed both on the mixtures and pure kaolin. Plasticity characteristics
were determined preliminarily from the values of the Atterberg limits
(liquid limit, WL%; plastic limit, Wp%). The fundamental mechanical behaviour
of the mixtures was examined on samples initially prepared as a slurry,
with a water content 'slfglitly over tw!ce the related liquid limit, ai::i(f thenconsolidated
one-dimensionally in a mould under an axial stress of 10 t/m 2
for a period of 60 days. The specimens, both for CIU triaxial and oedometer
tests, were trimmed from the sample obtained, 150 mm long and 100 mm in
diameter. Oedometer and CD direct shear tests also were performed
directly on the initial slurries. The changes of fundamental properties
with the silica content are plotted in Figs 1, 2, 3 and 4, from which it is
possible to draw the following conclusions: a) the linear relationships
between Atterberg limits and silica content imply a contemporaneous in-
' crease of the net interparticle attractive forces. The SEM investigations
showed that the smallest silica particles were adsorbed on the largest kaolin
particles, thus modifying their properties: the presence of silica grains lead
consequently to a coating of large particles and to an interparticle bonding,
b) che increase in cohesion and friction angle may be due to the same effect
0.4
0.2
0
C'
c
.,...,.
---·-c
,..--·
~~-·-·-· --•~r
c: consolidated - r: remolded
~-.......
c~ . •.............__
·---
0.04
~"-·
..... ... c
0.02
·---·--•-•-r
Silica (%)
Silica (%)
0 5 10
20
Fig. 1
30 ..
40
5 10 20
Fig. 2
30
40

704 Abstracts
1.8
1.2
0.6
c
(Kg/cm2)
.. /•,c'
. ./
/ .... c
1./
.,./
y·
c :total stress parameter
c': effective stress parameter
~.,-rp-~~~~~~~- -·-
30 ./.(effective)
20
10
v·/
~·/
_rp
• • (total)
---
0 5 10
Silica (%) Silica (%)
20 30 40 0 5 10 20 30 40
Fig. 3 Fig. 4
of interparticle bonding. The stress~strain plots show that, at higher silica
-- con-ten-ts, -mixtures- behave -as stairr=softening material, c) more complex is
the interpretation of the oedometertests: experimental data (compression
and swelling indexes, constrained moduli and permeability coefficients) are
quite different if samples have been formerly consolidated or not. The influence
of silica particles adsorption and creep phenomena as rate processes
has been pointed out in the formation of double layers, responsible for long
range repulsive forces between particles.
I
Mitchell K.J., 1976. Fundamentals of Soil Behavior. J. Wiley & Sons, New York. .
Moore C.A., Mitchell K.J., 1974. Electromagnetic forces and soil strength. Geotechnique 24 (4), 627-'
640. .
Sokolovich V.E., 1980. Electrostatic forces in soils. J. Soil Mech. Found. Eng., ASCE, 17 (2).

v.
Abstracts
705
Geological-Technical Characterization of the Clay Bash~
in Rutigliano, Province of Bari, Southern Italy
C. CHERUBINP, G. NUOV0 2 , F.P. RAMUNNP, N. WALSH 3
1 Istituto di Geologia Applicata e Geotecnica, Facolta di Ingegneria, Universita di Bari, Via Re David 200, 70125
Bari, Italia
2
Dipartimento Geomineralogico dell'Universita di Bari, Campus, Via G. Salvemini, 70124 Bari, Italia
3 Dipartimento di Geologia e Geofisica dell'Universita di Bari, Via G. Fortunato, 70125 Bari, Italia
Pleistocene transgressive clastic sediments outcrop in the built up area of
Rutigliano over a calcareous basement of the Cretaceous age.
The basal portion of the Pleistocene sediments consists of whitish calcarenites
gradually changing into pale yellow sands in the upper layers.
Detrital sediments change stratigraphically into clays. The latter consists of
silt clays of a blue-greenish colour with thin horizons of greyish silt. The
clays are heavily fissured and broken into polyhedrons of varying size. Along
the crack surfaces, black striations can be observed consisting of manganese
oxides.
On top of the clays there are transgressive depositions of sands and sandy
silts, bright yellowish to light brown in colour, medium to fine textured.
In terms of grain-size distribution, practically all the curves describing the
specimens considered in our study show a leptokurtic and unimodal distribution.
Generally, the sands are rather fine-textured and subrounded. Mineralogically,
these sands do not appear to belong to a variety of species; on the
contrary, they seem tp be of rather poor quality. Quartz-feldspar is the
prevailing fraction in all the samples and colourless to white and lactescent.
Heavy minerals are either absent as is the case in most samples or are only
present in traces (magnetite). Conversely, many specimens include iron
oxides or hydroxides of detrital origin.
Of the phyllosilicates, biotite is present, though in much smaller amounts
than the other minerals and belongs to the coarser grain-size classes.
The carbonates a~e represented by microfossils and clasts with either group
prevailing locally.
In terms of quantity, contents are between 2% and 30%.
For mineralogy of the clay levels, the reader is referred to the work of
Dell'Anna et al. (1974). Natural bulk density of the clays is about 2.00-2.10
t/m 3 • Average water content is 17%.
According to the established liquid limits, these clays belong to the class of
. The compression indexes show
values ranging from 0.010 to 0.0036 as pressure is increased from very low
values to 50 kg/cm 2 •
' ...
Dell'Anna, Di Pierro M., Nuovo G., Ciaranfi N., Ricchetti G., 1974. Puglie. Pp. 195-234, in: Giacimenti
di Argille Ceramiche in Italia (C. Palmonari and F. Veniale, editors), Gruppo Italiano AIPEA,
Cooperativa Libraria Editrice, Bologna.
I
I
·''

1
706 Abstracts
Dispersive Soils in Earth Dam Geology
A. PICCIO
Dipartimento di Scienze della Terra, Sezione geologico-paleontologica, Universita di Pavia, Strada Nuova 65,
27100 Pavia, Italia
Dispersive soils are referred to, in engineering geology, as fine grained soils
that rapidly erode by a process of dispersion (or deflocculation) so that the
individual clay particles go into suspension in slow-moving, practically still
water, whereas the erosion process for ordinary clays is quite different,
requiring considerable velocity in the eroding water (Sherard et al., 1976). In
the 1960's, dispersive soils, already recognized by soil scientists in the 1930's,
were found to be troublesome materials for earth dam embankments. Further
studies on case histories and on dispersive clays have tried to recognise
these soils by simple tests and to prevent their dangerous effects on the
stability of earth embankments but at present there is not an unique opinion
on the matter (see e.g. ASTM, S.T.P. 623, 1977).
Five tests are proposed by the U .S. Soil Conservation Service (Sherard et al.,
1976), none of them corresponding to the usual geotechnical tests, while
other Authors (Resendlz, 1977) claim that it is possible to estimate the risk of
dispersivity also by usual identification tests such as activity.
On the possibility to build safe earth dams with dispersive soils, some
._ -- ....... Auth0J::s-say-that-,-sinc:e the-mec:hanism of.dispeJ:sion is not yet well known,
these soils should be avoided as embankment materials. On the contrary,
according to other Authors, specially designed filters and careful attention to
prevent hydraulic fracture would permit the utilization of such soils.
Widespread diffusion of these soils has been recognized throughout the
world, but no study for Italian soils is known to the writer. As a first look on
the problem, 14 soils were tested with the «soluble salts in pore water»
chemical test, (Fig. l) and the test (Fig. 2).
The samples are very different in geological origin (sample 1 lacustrine; 6
and 12 aeolian-lacustrine; 2 and 8 alluvial; 3-14-11 eluvial; 5 and 10 marine;
7-13-14 colluvial; 9 volcanic), geotechnical properties and location (sample 5
from Piedmont; 3-4-10-11 from northern Apennines; 1-2-6-8-12 from central
Italy; 7 and 9 from southern Italy; 13 and 14 from Sicily).
The results of the tests show that there are Italian soils which could be
dispersive: due to the widespread diffusion, especially in the Apennines· and
100
:>

X
Cl)·
Abstracts 707
75
not susceptible
to piping
-o 50 9
,
+-'
·~
u
:;::;
tll
"' 25 0::
erodible
0
0 25 0 75
Content of clay (

708 Abstracts
the phyllosilicate component is principally characterised by an association
of illite (ill.), montmorillonite (mont.), and chlorite (chl.) with lesser quantities
ofkaolinite (K), quartz (Q) and calcite (C) (Table l).This can explain-the
different mechanism of erosion in «biancane>> compared to «calanchi» and
their individual morphologies.
Table I
Semiquantitative XRD analysis of clay fraction. Mean values
biancane
calanchi
ill.
33
25
mont.
18
18
chl.
13
11
K
9
7
Q
16
12
c
11
27
Even textural characteristics are different between «biancane» clay and
«calanchi» clay. In fact the percentages of the various sizes vary from the
first to the second, as can be seen from Table 2. Therefore, it emerges from
Shepard's diagram that «biancane» clay fits into the range of clayey-silts
and «calanchi» clay into the that of clayey-silty-sands. _
In determining the Atterberg limits and the plasticity range, the results
obtained (wich can be seen on the Casagrande plasticity diagram) give
evidence that

Abstracts
Long-Term Isolation of Radioactive Wastes in Deep
Clay Formations: Fractures and Faults as Possible
Pathways for Groundwater Percolation
709
M. D'ALESSANDR0 1 , F. GERA 2
1 Divisione Radiochimica, Ed. 46, C.C.R. Euratom, 21027 Ispra, Italia
2 Istituto Sperimentale Modelli e Strutture S.p.A., Via dei Crociferi 44, 00197 Roma, Italia
Some radioactive wastes contain very long-lived radionuclides and need to
be isolated from the biosphere for many thousands of years. Long-term
isolation can be provided by a combination of natural and man made barriers.
Geological formations of different types have been proposed as suitable
natural barriers for radioactive waste isolation.
Argillaceous formations can have very favourable characteristics, such as:
- low permeability;
- high plasticity;
- high sorption capacity.
Mathematical models of radioactive waste disposal in deep clays indicate
that waste will be successfully isolated provided that the favourable properties
are not modified by geologic processes or human activity.
In some cases argillaceous materials appear to be or to have been characterized
by a certain fracture permeability. In many clay quarries, fissures
surrounded by oxidation zones one or two cm thick have been observed. In
some cases the oxidation zones are more than 100 m below the original
ground surface. The oxidation zones are brownish in colour and appear to be
due to oxides ~nd hydroxides of Fe 3 +; they prove that oxidizing water has
percolated along the fissures.
An understanding of the mechanism and rate of formation of oxidation zones
in clays would allow us to interpret field observations and to decide if the
oxidation zones must be considered proof of long-term water circulation at
depths or if they can be near surface features formed after excavation and
stress relief of the clays.
On Residual Failure Mechanisms
V. COTECCHIA, A. FEDERICO
Istituto di Geologia Applicata e Geotecnica, Facolta di Ingegneria, Universita di Bari, Via Re David 200, 70125
Bari, Italia.
It is well known that the values of the angle of residual friction 0'R present a
sharp variation for Ip values of around 25-30%. Lupini et al. (1981) have
explained this phenomenon in the light of the various residual failure mechanisms
that can occur. The same Authors have also hypothesized, on the basis
of observational considerations, that if a soil exhibiting residual behaviour of
the turbulent type is sheared against a smooth, hard surface- which locally
'!
/ '

l
710 Abstracts
reduces the interference of the grains of sand and silt - a partial sliding at
the contact may take place, with local isorientation of the platy clay particles
and lower residual strenght.
The aim of the present research was the experimental verification of this
latter aspect which, while appearing to be of marginal importance, is nevertheless
of conceptual interest and of possible applicational relevance.
The materials used were mixtures of quartzose-feldspathic sand and kaolinite
in various ratios of dry volume. The results obtained are reported in Fig. 1.
An examination of the results and of textural observations, although limited
to just one type of sand-clay mixture, confirmed the hypothesis put forward
by Lupini et al. (1981). If such confirmation can be extrapolated, as would
seem likely, to other clayey materials, two considerations should be made:
1) the residual technique using a smoothed plate, introduced by Kanji
(1974), offers as is known, the advantage of requiring only a small displacement
for the residual strength. Theresults obtained by the Autor (1974, Le.)
show decreases in residual strength of soil-rock contact of up to 50% (depending
on the roughness of the contact) in relation to the analogous resistance of
the soil alone (direct shear). Moreover, for clays of medium-high plasticity
the smooth plate (Kanji & Wolle, 1977) compares well in its results with
the ring shear apparatus; however, as lp diminishes, the differences- for
materials of the same plasticity- become considerable, which is the consequence
of the different type of residual failure mechanism. It would therefore
appear to be incorrect, for natural situations of real slipping of soil-to-soil (of
low plasticity) to resort to the residual technique using the smooth plate;
2) on the contrary, the 0'R values of low plasticity soils determined on
smooth or variously rough plates may be of significance in situations which
____ .. _________________________________ realLy__present_slipping problems_along soil-rock contacts.
a' = 136 k Pa
35 • 1
n
... 2
T 3
28
24 full orientation
~-----+--?
20
0.3
8
0.1
4
I
Ip=29 Ip=26 Ip=21
0
0
40 Sand
80 100
100 80
40
0 (%)
Kaolinite

(
T!;,
I
I'
Abstracts 711
Kanji M.A., 1974. Unco~ventionallaboratory tests for the determination of the shear strenght of
soil-rock contacts. Proc. 3rd Congr. Int. Soc. Rock Mech., Denver (Cola.), 2, 241-247.
Kanji M.A., Wolle C.M., 1977. Residual strenght-New Testingand microstructure. Proc. 9th Int.
Conf SMFE, Tokyo, I, 153-154.
Lupini J.F., Skinner A.E., Vaughan P.R., 1981. The drained residual strenght of cohesive soils.
Geotechnique, 31, n. 2, 181-213.
.,
I

AUTHOR INDEX
ABDEL GADIR S. 350
AGUILAR A. 483
AJMONE MARSAN F. 473,511
ALBANESE L. 671
ALBERTI A. 425,426
ANTONIOLI F. 339
APARICIO A. 352
ARAGON F. 340
ARDUINO E. 473, 511
ASSI I. 661
AYERBE M. 513
BALENZANO F. 647
BANDS C. 513
BARAHONA E. 483, 489, 521, 577
BARBERIS E. 473,511
BARRIOS J. 427
BERRIER J. 499
BERTOLANI M. 348
BINI C. 499
BRELL J .M. 267
BRIGATTI M.F. 425, 426
BOERO V. 473, 511
BURRIESCI N. 428
CABALLERO E. 187
CANCELLI A. 609, 661
CAPEL J. 563
CARAMES M. 267
CASAL B. 183
CAUCIA F. 347, 600
CHERUBINI C. 621, 67'1, 705
COCITO S. 600
COMAS MINONDO M.C. 245
CORMA A. 181, 182
COTECCHIA V. 709
D'ALESSANDRO M. 709
DAMBLON F. 350
DE SOUSA FIGUEIREDO GOMES_ C. 381
DELL'ANNA L. 85, 629, 647
DELMAS A.B. 499
DENTE G. 693
DI PIERRO M. 205,217,629,647,671
DIOS CANCELA G. 145
DOVAL M. 267, 340, 352
ESPOSITO L. 693
FABBRI B. 535
FAILLA A. 609
FARINI A. 661
FEDERICO A. 709
FELICE G. 437
FENOLL HACH-ALI P. 231, 245,.341, 343
FERNANDEZ MARTINEZ J. 341
FERNANDEZ NIETO C. 259
FIORI C. 535
'- FORNES V. 181
FRANCANI V. 661
FRANCHINI M. 511
FRANCI M. 171
FUSI P. 137, 171
GALAN E. 259, 352
GALLIGNANI P. 277
GAL V AN GARCIA J. 604
GAL VAN MARTINEZ B. 604
GARCIA-GONZALEZ M.T. 514
GARCIA-RAMOS G. 599, 601
GARCIA-SANCHEZ A. 345
GENEVOIS R. 703
GERA F. 709
GE$SA C. 428
GIACHETTI M. 515
GIASl C.I. 671
GIOVANNINI G. 515
GONZALEZ DIEZ I. 259
GONZALEZ-GARCIA F. 599, 601
GONZALEZ GARCIA S. 145
GONZALEZ LOPEZ M. 259
GONZALEZ PENA J .M. 604

714 Author index
GONZALEZ VILCHES M.C. 601
GRILLINI G.C. 437, 461
GUADAGNO F.M. 671
GUERRICCHIO A. 621, 629
GUILLEN ALFARO J.A. 145
HELLER-KALLAI L. 3
HERMOSIN M.C. 155
HERNANDEZ-HERNANDEZ P. 603
HIDALGO A. 431
HUERTAS F. 187, 303, 483, 489, 521, 563,
577
MESA J.M. 599
MIFSUD A. 181, 182
MILLAN A. 455
MONTCHARMONT M. 350
MORANDI N. 437,461, 609
"MORELLI G.L. 431
MORES! M. 205, 217
MORILLO E. 155
NANNETTI M.C. 461
NAY ARRETE J. 349
NUOVO G. 351, 705
IGLESIAS J .E. 363
JAIME S. 483
JUSTO ERBEZ A. 591
KONTA J. 121
KUHNEL R.A. 681
LA IGLESIA A. 429
LANDUZZI V. 277
LEGUEY S. 287, 344
LENZI G. 339
LINARES J. 17, 187, 303,483, 489, 521, 563,
577
LOPEZ-AGUAYO F. 303
LOPEZ GALINDO A. 245
LOPEZ GARRIDO A.C. 341
LOPEZ-PLAZA S. 603
LOSCHI GHITTONI A.G. 348
LUCCHESI S. 515
OLIVERA P. 179
OLIVERI F. 277
ORTEGA HUERTAS M. 231, 245, 341, 343
PALMIERI F. 391
PALMONARI C. 547
PALOMO DELGADO I. 231, 341
PEDE A. 671
PEREZ J. 182
PEREZ PARIENTE J. 181
PEREZ RODRIGUEZ,J.L. 155, 591
PESCATORE T. 350
PETRERA M. 428
PICCIO A. 706
PICCONE G. 511
POPPI L. 426
POZO M. 287, 344
POZZUOLI A. V, XV, XIX, 521, 577
PREVITALI F. 661
QUIRK J.P. 137
MAQUEDA C. 591
MARTELLONI C. 137
MARTIN PATINO M.T. 345, 455
MARTIN-POZAS J.M. 349
MARTIN-VIVALDI J.M. 349
MASCOLO G. 163
MASSA S. 600
MEDINA J .A. 287
MELIDORO G. 629
MELIS P. 428
MENDELOVICI E. 357
RAMUNNI F.P. 671, 705
RAUSELL-COLOM J.A. 399, 409
RECIO M.P. 514
REYES E. 187, 489
RISTORI G.G. 137, 171
RIZZO V. 647
RODAS M. 340
RODRIGUEZ A. 179
RODRIGUEZ FERNANDEZ J. 341, 343
RODRIGUEZ GALLEGO M. 55
RODRICUEZ GORDILLO J. 343

J
Autor int/.ex
715
RODRIGUEZ PASCUAL C. 604
ROUX M.V. 455
RUIZ A. 483
RUIZ-ABRIO M.T. 599
R UIZ AMIL A .. 340
RUIZ-HITZKY E. 183
TENAGLIA A. 547, 602
THOREZ J. 313, 350
TOMADIN L. 277
TORRENT J. 427
TURRION C. 455
SAAVEDRA J. 345,455
SAGARZAZU A. 357
SANCHEZ-CAMAZANO M. 180, 516
SANCHEZ-MARTIN M.J. 180, 516
SANCHEZ-SOTO P.J. 599
SANTOS M. 431
SANZ E. 182
SCESI L. 661
SDAO G. 707
SEBASTIAN PARDO E. 303
SENATOR£ M.R. 350
SERNA C.J. 363
SERRATOSA J.M. 71, 399, 409
SETT! M. 600
SIMONE A. 707
SOGGETTI F. 347
SOLINAS V. 428
SPARVOLI E. 137
STREEL M. 350
VENIAL£ F. 101, 347, 600, 661
VENTURI V. 602
VIANELLI G. 437
VICENTE M.A. 197,516,603
VICENTE-HERNANDEZ J. 197, 603
VILLALBA R. 357
VIOLANTE A. 371, 391
VIOLANTE P. 391
VITTORINI S. 707
VURRO F. 205
WALSH N. 705
YANEZ J. 489
YUSTA A. 489
TCHOUBAR C. 35
TECCA P.R. 703
ZANINI E. 473
ZEZZA U. 347

Abruzzo Region. 278
Abruzzo-Campania.
carbonate platform. 95
Activation energy. 184
Activity index.
(see geotechnical properties ... )
Actual clay structures.
methods of determination. 37, 39
localization of octahedral vacancies. 47
kinds of stacking faults. rotational faults,
translational faults, faults by
fluctuation of the layers around an
average position. 42, 43,44
Adriatic sea. 278,285
Adsorption.
of chloropropham by montmorillonite,
kaolinite, illite and soils. 147, 150,
standard free energy, standard
enthalphy standard entrophy. 153
of chlorthiamid by homoionic
montmorillonite. 173, 175
of dichlobenil by homoionic
montmorillonite. 176
of para-nitrophenol on homoioni~
montmorillonite and beidellite. 139
Akaganeite.
by reaction of goethite and lepidocrocite
with glycerol. 360
Alkylamines.
inter layer complex of lanthanidt7
vermiculite. 179
Alkylammonium ions.
decomposition in butanol medium. 160,
162
Allophane. 103,208
Alluvial fans. 271,344
Almeria. 17, 187, 259
Alpujarride Complex. 342, 483
Alteration.
of volcanic rocks. 18, 187,205,311,347,
348,490
Alteration clay integron. 318
Aluminium extractable form.
indicator of different ages of fluvial
terraces soils. 480
Aluminum hydroxides and oxyhydroxides.
influence of organic ligands on
crystallization of. 372
Alunite.18, 187
SUBJECT INDEX
AII).blygonite.
associated with lithium-muscovites in
granitic pegmatites from centralwestern
Spain:. 345
Amide.
from hydrolysis of chlordimeform in
aqueous medium. 162
Amine.
interlamellar sorption of mixed-layer
minerals. 341
Amphiboles. 102,207,652 ,
Analcime. 211,425
Analysis of variance. 425,426
Anchimetamorphic conditions, process. 265
Andosoil. 208
Anhydrite. 269
Anion exchange selectivity. 166
Anorthite.
high-temperature phase. 565, 566
Anoxis conditions. ·
in the sedimentary environment of
pelagic Cretaceous black-greenish
mudstones. 256
Antacid. 164
Antognola Formation. 609
Apulia Region. 351,621,671
Apennines.
central. 115, 116,280
northern. 105,113,114,609
southern.99,206,217
Argille varicolori.
as red bed clays in the production of
ceramic floor and wall tile. 602
from Avellino Province, characteristics
and diagenetic processes. 221,224,226,
228
from northern Apennines, in the
production of stoneware tiles. 536
influence of different clay mineralogy on
the soil fabric. 106
relationship with lateritic soils. 228
source areas of the Ofanto river sediments
and smectites. 99,283
Argillogenesis. 313
Aromatic amines.
interlayer complexes of lanthanide
vermiculite. 179
Arsenopyrite.
in granitic pegmatites from central-

718 Subject index
western Spain. 345
As compacted test.
(see geotechnical properties ... )
Atomic Absorption Spectroscopy. 209,357,
491,665,676 '
Atterberg limits.
(see geoiechnical properties ... )
Avellino Province. 217, 694
Avila Province. 455, 603
Azuer river. 564
b axis measurement.
in illites, micas and smectites. 261,304
B horizon of clay soils.
standard soils sticks, gypsum application
for different periods of time, calcium
diffusion. study with scanning electron
microscopy .exchangeable calcium
distribution in sticks, poral system
~----geometi"y,-Fe0l.=ganiza-tien of-elay --~-- -
particles. 502,503 1
504,505,506
B horizons of medi terranean red soils.
micromorphological features of clay
translocations. 513
Badajoz. 599,600
Bagni-Fondachelli Units. 659
Balance of matter.
matter and mineral losses during the
formation of altered products and soil
from peridotites. 496,497,498
matter losses during the formation of
bentonite deposits in southeastern
Spain. 28,29
Bayerite.
from interaction between lithium
hydroxide dialuminate and
homocationic solutions. 166
infrared spectra. 396
relation with organic ligands. 372
synthesis. 392
Bari Province. 705
Barite. 249,291
Barth geochemical balance.
(see balance of matter)
Beidellite.
adsorption of para-nitrophenol. 139
crystal chemistry. 426 ·
ferric, from Mondaino, Italy, 138
homoionic, specific surface area. 141
stage number for the calculation of the
hydrolysis index. 333 ~-~--------~-~-~- -~
weathering index. 329
Beidellite-montmorillonite series. 223
Bentonites.
anion and cation exchange capacity. 190,
192
colour of. 19
deposits. chemistry, genesis. 189, 196, 311
disordered tridymite. 23
geothermometer (Na-K-Ca). 195
hydrothermal alteration. 187
hydrothermal solutions. chemistry. 192,
origin. 23, 189, thermal characteristics.
24, transport. Z4, types. 193
phyllosilicates. 2:1 phase diagram. 31
process of formation. devftrification of
glass. 28, enthalphy of hydrolysis
reaction. 26, free energy of hydrolysis
reaction. 27, hydratation of glass. 28,
matter-andvolumeJosses. 29, phase
rule. 25, 27, reaction rates. 29,
temperature. 24
rock wall alteration.187, 188
soluble salts. 193
temperatureofformation.195, 196
Bentonite (Wyoming). 138, 172
H-bentonite.
Mossbauer study. 428
Benzoic acid.
from aci~ic hydrolysis of thiobenzamide.
176
Benzoni trile.
from thiobenzamide in alkaline medium.
176
Betic Cordillera. 232,245,265, 304,489
Biancane.
in Pliocene and Pleistocene of Calabrian
clay areas. 707
~ikitaite.
associated with lithium-muscovites in
granitic pegmatites from centralwestern
Spain. 345
Biotite.
(see dehydroxylation process and high
resolution transmission electron
microscopy)
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329

Subject index 719
Biscaye index.
(see montmorillonite)
Bishop's method.
(see geotechnical properties ... )
Black Flysch or Crete Nere Formation. 629
Blue-grey clays. 622,643
Block Formation. 343
Bodies for stoneware tiles.
theoretical formulation. 541
Boehmite (disordered).
relation with organic ligands. 372
weathering index. 329
Bologna Province. 552
Boron.
determination with optical spectrometry.
464
extractable, in soils used to grow
subtropical crops. 487
from rocks and soils, balance of matter.
498
Bradano Foretrough (Bradanic Trough,
° FossaBradanica). 206,352,623,671
Brahmaputra river, 126
Bronze age pottery.
from ia Mancha. 563
domestic use, firing temperatures.'S64,
565,566
effect of burial. 569
free energy of ceramic reactions. 566, 56 7
Brown soils.
from Cantabria. 514
gypsum effect on. 504
Bulk density.
of dry test pieces. 524
relationship with heterometry indexes.
531
Butanol solution
(see alkylammonium ions). 159
Butylamine.
(see amine)
Cabo de Gata volcanic region. 18, 187
Calabria Region. 351,647,707
Calabrian coastal chain. 647
Calanchi.
in Pliocene and Pleistocene of Calabrian
clay areas. 707
Calcite.
compensation depth. 254
high-temperature phase. 565, 566
in ceramic bodies, autoclave treatment.
571,572
weathering index. 329
Calcretization.
influence on genesis of fibrous minerals.
288
Campania-Lucania.
carbonate platform. 95
Camp ani a Region. 85, 640
Caotico Indifferenziato. 439,463
Carbon.
in the dust that cover the statues
adorning the Porticos of the Seville
Cathedral. 595
Carbon-14 dating.
of the Motilla del Azuer archaeological
excavations. 564
Caroni river, 126
Casagrande plasticity chart.
(see geotechnical properties ... )
Cassiterite.
in granitic pegmatites from centralwestern
Spain. 345
Castagna Units. 659
Catalytic activity.
ofsepioliteandpalygorskite.181, 182
Catanzaro Province. 694
Cation exchange capacity.
associated with fine material quantities
and extractable forms of AI and Fe as
indicator of different ages of fluvial
terrace soils. 480
Ceramic bodies.
autoclave treatment. 569
Ceramic clays.
from central Spain. 604
from ·southwestern Spain. 599
from Italian Oligocene Formations. 602
Ceramic pieces.
archeological bed of Cerro Macareno,
Seville. 601,602
eneolithic settlements of la Peiia del
Aguila, Avila. 603, 604
late Roman and Middle Age times. 600,
601
Ceramic sculptures.
alteration of. 595
contamination. 597
Ceramic sludges.

720 Subject index
disposal and reuse for heavy clay
products, industrial scale tests. 551,
557
Chabazite. 425
Chalcopyri te.
in granitic pegmatites from centralwestern
Spain. 345
Chelating organic ligands. 376
Chemical test.
(see geotechnical properties ... )
Chlordimeform.
aqueous and butanol solutions of. 157,
159
Chlorite.
classification. 634, 652
crystalchemistry, 634
polytypism. 634, 652
relationship with linear shrinkage. 529
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329
· -----··a;!0~op~~pha~~-- -- · --- · --
(see adsorption)
Chlorthiamid.
decomposition to dichlobenil. 176
Chloritization.
secondary. 328
Chromium.
influence on crystallization of iron oxides.
427
from rocks and soils, balance of matter.
498
Ciudad Real Province. 564
Clay and non-clay minerals.
assemblages in various sediments, rocks,
soils and rivers suspensions. 20, 88,
105,124,199,207,208,211,224,225,
235-239,249,249-251,261,266,274,
279,280,282,290,293,305,335,339,
340,342-345,348-350,353,441,444,
455,465,485,493,501,511-514;516,
536,548,599,600,605,611,624,632,
653,665,675,695,705,708
Clay mineral species.
stage numbers. 333
Clay-vermiculite. 440, 464
Cluster analysis. 468
Cobalt.
from rocks and soil, balance of matter.
498
Complesso Sicilide. 218
Copper. -·---~extractable,
in soils used to grow
subtropical cropsC 487
Cordillera Central. 516
Cordoba. 599,600
Costa Rica.
caracteristics of clays from the Central
Valley. 348
Cretaceous Iberian paleomargin. 245
Crete Nere Formation or Black Flysch. 629
Cristobalite.
high-temperature phase. 601
high-temperature phase from ka~linites
with intercalated mineralizers. 385,
386;387,388
weathering index. 329
Cryptands.
intercalation between the layers of
smectites and vermiculites. 183
Cuenca Province. 429
Defects.
(see layer silicates).
Dehydroxylation process.
in biotites, phlogopites and homoionic
vermiculites, infrared study. 402,403,
404,405
influence of interlayer saturating cations
and octahedral composition on. 406,
407
selectivity of the thermal process
according to octahedral composition.
408
Desiccation phases.
ih the Neogene basin of Madrid. 296, 297,
298
Determination of crystallographic axes in
microcrystals. 365, 366, 367
Diagenesis.
dickite, from kaolinite. 228
fibrous minerals, from carbonated waters
reacting with silcretes. 299
late, in Paleozoic shales and lutites, 353
Diamines.
interlayer complexes with lanthanide
vermiculite. 179
Dichlobenil.
from decompositiOJ?- of chlorthiamid. 176
~
I

0
-----------------------------------------------------~
0
of
0"
Subject index 721
Dichlorvos
interaction with vermiculite. 180
Dickite.
chemical composition, 634
diagenetic, in argille varicolori. 111 , 223,
228
hydrothermal, in Crete Nere Formation.
644
in microtextures of a scaly clay and Crete
Nere Formation. 110, 639
lattice constants. 635
Differential Scanning Calorimetry.
quantitative determination of gibbsite
and halloysite. 459
Differential Thermal Analysis.
of altered ceramic sculptures. 596
of aluminium precipitation products in
presence of organic ligands. 374
ofEdilfornaciai clay. 554
Dimethylsulfoxide.
in oriented specimens for X-ray
diffraction. 234, 250, 260
interaction with lanthanide vermiculites.
179
intercalating agent in the kaolinite
structure. 383
'-
Diopside.
equation for firing temperature
prediction. 590
high-temperature phase. 565,601
in ceramic bodies, autoclave treatment.
571,572
reflecting power factor. 590
Discriminant analysis.
correlations between genesis and
chemical composition in zeolites. 425
differences of crystal chemistry in Al-rich
smectite types. 426
Dispersive soils.
in earth dam geology. 706
Distribution coefficients.
Cs and Sr sorption properties by clayey
formations. 339
Dolomitic sandstones. 170
Drying properties.
of ceramic clays. 524
DudarFormation. 343
Duero basin. 344
Electron micrograph.
of AI precipitation products. 373
of brown leached soil and red fersialli tic
soil from Jura Region. 502,504,506
different shapes of clay minerals. 682
of gibbsite. 459
of nordstrandite. 394
ofpalygorskite. 200,295,308
of sepiolite. 292, 295
of smectite. 292, 308
Emilia-Romagna Region. 437,461
Eneolithic ceramic. 218
English clays.
illitic-kaolinitic materials for stoneware
tiles. 539
Epimetamorphism-anchimetamorphism
conditions.
in Paleozoic shales and lutites. 353
Epsomite. 269
Erionite. 425
Eucryptite.
associated with lithium-muscovites in
granitic pegmatites from centralwestern
Spain. 345
Evaporitic Miocene sediments.
ofTajo basin. 275
Fabric.
influence on slope stability-failure. 105
scanning electron microscopy on:
laminations of sewage pipes. 689, 690,
691, microstructure offired samples.
556, structural arrangement of soil
with different water content. 696, 697,
texture, morphology and location of
minerals in sedimentary and volcanic
rocks. 106, 107,108,109,110,111, 112,
113,114,115,116,200,292,295,308,
638,639,682
Factor analysis.
R-mode.189,477,494,479
Fardes Formation. 251, 303
Feldspars.
equations for firing temperature
prediction. 590
evolution with firing temperature. 589
in ceramic bodies, autoclave treatment.
571,572
Ferrallitic weathering characteristics. 212,
215
I
i
:I
·'
!

722 Subject index
i
il
' I' .. _'.
,, i
.
!!
Firing properties of ceramic clays.
crushing strenght. 586
durability index. 582
equation for firing temperature
prediction. 590
high-temperature phases. 588,589, 590
shrinkage, relationship with clay
mineralogy, calcite effect on. 585
water absorption. 584
weight loss. 578
Fluvial pelit-ic supplies.
clay mineral facies. 282, 283
horizontal zoning. 282
inherited imprinting. 282, 286
Fluvio-lacustrine environment.
influence of silicification and
calcretization of the genesis of fibrous
clay minerals. 288
Flysch.
Albidona. 631
Castelvetere. 92
-------------------·Gate·strrne.-6-30 ____ --------------
Gorgoglione. 92, 95,207
Nocara. 218
Numidico. 207
Rosso. 207
Fossa Bradanica.
(see Bradano F oretrough)
French clays.
illitic-kaolinitic materials for stoneware
tiles.539
Freundlich's model. 89
adsorption isotherms of chloropropham
by clay minerals, peat and soils. 147,
150
adsorption isotherms of pesticides by
homoionic vermiculite. 180
Frido Formation. 631
Frohlic relation. 367
Ganges river. 126
Garnet.. 199, 207, 652
Gehlenite.
gestruction. 566
equation for firing temperature
prediction. 590
high-temperature phase. 565, 566,601
in ceramic bodies, autoclave treatment.
571,572
reflecting power factor. 590
Genesis.
relationships ~ith chemistry in :z.te2li!e,

Subject index 723
unconfined compressive test. 625,637
Geothermometer.
(see bentonites ... )
German clays.
illitic-kaolinitic materials for stoneware
tiles. 539
Gessoso-Solfifera Formation. 439
Gibbsite.
formed in presence of organic ligands. 372
in weathering sequences. 347
infrared differences with bayerite and
nordstrandite. 396
quantitative determination by
Differential Scanning Calorimetry. 459
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329
Glauberite. 269
Glycerol.
(see goethite, lepidocrocite and magnetite)
Gneiss.
chamotte in antique ceramics. 601
Goethite.
effect of chromium on crystallization of.
427 ,,
transformation in the thermal reaction
between lepidocrocite and glycerol.
360
weathering index. 329
Gord6n-Matallana coal basin. 352
Granada Province. 145, 303, 521, 577
Granite.
chamotte in antique ceramics. 601
Greene-Kelly treatment (Li-test).
(see montmorillonite)
Grinding.
effects on crystallinity, standard free
energy of kaolinite. 429
Guadalquivir river basin. 513.
Gypsum.
effect of applications on clay materials.
improvement of soils affected by strong
limitations. 507,508
in evaporite Miocene sediments of the
Tajo basin. 269
in the dust that cover the statues
adorning the Porticos of the Seville
Cathedral. 595
weathering index. 329
H-type isotherms. 183
Halite. 269
Halloysite.
quantitative determination by
Differential Scanning Calorimetry. 459
Hancock-Sharp method.
kinetic study of the interaction of
macrocyclic compounds with layer
silicates. 184
Hematite.
shape effects and estimation of the
particle shape responsible for'. 364,365
surface area. 359
thermal reaction with glycerol. 359
weathering index. 329
Hemipelagites.
in northern and southern Middle
Subbetic realms, differences with
turbiditic pelites. 254
mineralogical composition. 251
Hepty lamine.
(see amine)
Herbicide.
retention of chloropropham by clay
minerals, peat and soils. 145
Heulandite. 272, 425
High resolution transmission electron
microscopy.
of a brucite-like sheet. 67
of a damage by electron beam irradiation
in 1M biotite. 68
of a dislocation in goethite. 60
of a low angle boundary betwe.en
wonesite and chlorite. 65
of a low angle grain boundaries in
chlorite. 64
of a muscovite-biotite transformation. 66
of a talc-chlorite-lizardite intergrowth. 65
of an amphibole-talc intergrowth. 66
of clinochlore. 62
ofmargarite. 62
of microprecipitates in pla~es ofbiotite.
67
Hinckley index.
(see kaolinite)
Huelva. 599
Hydrazine hydrate.
intercalating agent, intercalating degree.
383
Hydrogen bonding.
I I
'
! I
·'

724 Subject index
in Al(OH) 3 polymorphs. 393
Hydrohematite. 363 '
Hydrolysis.
in the process of bentonite formation. 26,
27,28,195
of archaeological ceramic pieces
submitted to autoclave treatment. 569
of chlordimeform in aqueous medium.
162
ofnaturallepidocrocite alkoxide. 361
of thiobenzamide in acid and alkaline
media.176
Hydrolysis index.
definition. 330
calculation and relationship with
paleoclimatic reconstruction. 332
Hydrolytic reactions.
of aluminium, influence of organic
ligands. 379
Hygroscopicity.
relationship with crushing strenght. 587
··· --· ----·-·--·-· - - -su:ilaoility-ofra w materialsfor the
manufacture of structural ceramics.
532
Hydrotalcite.
anion selectivity sequence. 167
Hydrothermal solution.
composition from analysis of ions
extracted from bentonites. 189
Illite.
chemical composition. 265, 675
crystal size. 261
crystallinity. 223,261,285, 634,652
dioctahedraL 223,265,270,624,634,652,
675
evolution in soils. 452, 517, 659
Kubler crystallinity index. 261, 353
paragonitization degree. 223, 634,652
polytypism. 223,624, 634,652, 675
relationship with linear shrinkage. 529
stage number for the calculation of the
hydrolysis index. 333
transformation pathways. 328
trioctahedral. 265,270
Weaver crystallinity index. 353
Illitic-chloritic and Illitic-kaolinitic clays.
for stoneware tiles. 535, 536
Imogolite.
in soils from Vulture. 208
on the surface of weath~r~c;l felgsRars.)47~---·
Indus river. 126
Infrared spectroscopy.
analysis of particle shape. 363,364
of Al precipitation products formed in
presence oftannic acid. 375
of chlorthiamid-Al-montmorillonite
complex. 173
of chlorthiamid-Ca-montmorillonite
complex. 175
ofglycerolato derivatives from
lepidocrocite and hematite. 361
of micas heated at various temperatures. ·
405
of OH-bending region of aluminum
hydroxide polymorphs. 396
of OH-stretching region of aluminum
hydroxide polymorphs. 395
ofhematite. 368
of vermiculite-decylammonium complex
- treated with water and organic
substance. 158,161
ofvermiculites saturated with
monovalent and divalent cations, after
being heated at various temperatures.
402,403,404
optical constants ofhematite. 368
theory of absorption and scattering by
small particles. 364
Interlayer.
of homoionic smectites, penetration of
paranitrophenol and chlorthiamid.
143,172
of vermiculite-decylammonium complex.
157, 159
basal spacings of anion-exchanged forms
oflithiumhydroxidedialuminate.167.
complexes oflanthanide vermiculites
with organic substances. 179
homoionic vermiculites treated with,
pesticides. 180
of vermiculites and smectites with
macrocyclic compounds. 183
saturating cations, influence on
dehydroxylation of micas and
vermiculites. 407,408
cations in homoionic vermiculites,
structural implications. 414
Interstratified minerals.
(see mixed-layer minerals)

-------------------------------------------------- ~.
Subject index 725
Iron.
displacement from octahedral layer ofHbentonite.
428
extractable, in soils used to grow
subtropical crops, equilibrium with
siderite. 488 ·
extractable form, indicator of different
ages of fluvial terraces soils. 480
from rocks and spils, balance of matter.
496
micronutrient in soils. 483
Iron oxides.
crystallization at low temperature. 427
ferrihydrite. 211
goethite. 211
in soils from Vulture. 208.
thermal reactions with glycerol. 359,360
Irpinian Units.
Castelvetere flysch, Gorgogliore flysch,
Serra Palazzo Formation. 92
Isosteric (adsorption) heats.
chloepropham adsorption by clay
minerals and soils. 151
pesticides adsorptio~ by homoionic
vermiculites. 181
Isotope studies.
""'
of hydrogen and oxygen in bentonites. 20,
188
Jackson sequence.
clay mineral reactions in soils. 319
Jarosite. 18
J].lra Region. 500
Jurassic sediments.
origin and paleogeography. 241, 242, 243
K coefficient of permeability. 700
K-feldspar. '
high-temperature phase. 565, 566
in ceramic bodies, autoclave treatmnet.
571,572
K-Ar dating.
of Vulture volcanic products. 207
Ks values.
for different drying sensitivities. 531
Kaolinite.
adsorption of chloropropham. 147
effect of mineralizers on the temperature,
rate and products of thermal reactions.
385,386,387,388
effect on decarboxylation and cracking of
stearic acid. 10
Hinckley crystallinity index. 220, 385,
386,387,388,429,634,650,675
in argille varicolori, diagenetic
trasformation to dickite. 228
relationship with linear shrinkage. 529
stage number for the calculation of the
hydrolysis index. 333
Kerogen.
in carbonate rocks and shales, natural
thermalevents.5,6
mineral reactions. 8, 9
parent material. clay catalysis. open,
closed and semiclosed systems.
transporting medium. 3, 4, 5
pyrolysis in closed and open systems. 7, 8
Kilchoanite. 596
Kubler index.
(see illite)
Kyanite. 199
L, Rand Rk molecular ratios.
relationships between geochemical
characteristics of underground waters
and neogenesis of the weathering
minerals. 209,214
La Peza Formation. 343
Lacustrine precipitation.
genetic environment in the Neogene basin
of Madrid. 300
Laga Formation. 280,281,282
Lagonegro basin. 95
Lambert equal area projection.
structural analysis of the fisseres in bluegrey
clays. 624
Lamination.
in ceramic bodies. 688, 689, 690,691
Langmuir type isotherms. 139
Landslide phenomena.
importance of microfabric in researches
of. 103
in Crete Nere Formation. 640
in the Baiso and Lucera areas. 610,626
Lanthanide vermiculite. 179
Laponite.
effect on decarbo.xylation and cracking of
stearic acid. 10
I
·'I I

726 Subject index
Layer silicates.
line defects. plane defects. regular mixedlayhs,
formation by point defect
induction, random mixed-layers. 59,
60,61,62,63,64
point defects. thermodynamic approach,
thermoluminescence, cation ordering
in micas. 56, 57, 58,59
volume defects. grain boudaries,
intergrowths, lamellar precipitates,
exsolutions.64,65,66,67,68,69
Raman spectra. 431
Lead.
in the dust that cover the statues
adorning the Porticos of the Seville
Cathedral. 595
Lecce Province. 671
Le6n Province. 352
Lepidocrocite.
transformation to iron alkoxide by
reaction with glycerol. 360
--------------,:----weat-hering-index:-32 9 -----· -
Li-test. 426,761
(see montmorillonite)
Liguride complex .. 630
Lithium hydroxide dialuminate. 164
Lithium-muscovites.
in granitic pegmatite from centralwestern
Soain, mechanism of
formation. 345, 346
Lombardy Region. 661
Lucania Apennines. 206
Lucania Region. 640
Lizardite.
effect on decarboxylation and cracking of
stearic acid. 10
LST relation in anysotropic microcrystals,
Luxonformula. 367
Macigno Formation. 439
Mackenzie river. 126
Magnetite.
unchanged by reaction with glycerol. 360
weathering index. 329
Malaga Province. 483,489
Malaguide Complex. 483
Manganese.
degradation of ceramic sculptures. 597
from rocks and soils, balance of matter.
498
Margarite.
27
Al and 29 Si isotropic chemic~L~hift§.,_l_t)
29 Si MAS-NMR spectrum. 74
Marnoso-Arenacea Formation. 439
MAS-NMR spectra of phyllosilicates. 72
Meixnerite. 165
Micas.
dehydroxylation process. 400
Micronutrients.
boron, copper and iron in soils. 484
Mineralizers.
(see kaolinite)
Mixed-layer minerals.
Allegra formula. 431
Fourier transform analysis. 169, 340
in sediments. 211,223,234,251,270, 2RO,
339,340,344,350,353,440,464,512,
514,632,650
Molisano basin. 95
Montmorillonite.
adsorption of chloropropham. 147
adsorption of chlorthiamid and
dichlobenil. 173, 175, 176
adsorption of macrocyclic compounds.
184
adsorption of para-nitrophenol. 139
crystallinity, Biscaye index. 223,261,265,
284
displacement of Fe from octahedral layer,
Mi:issbauer study. 428
effect on decarboxylation and cracking of
stearic acid. 10
formed by hydrolysis during burial of
high-temperature ceramic sherds. 574
Greene-Kelly treatment (Li-test). 220,
261,426,761
homoionic, specific surface area. 141
reduction of structural iron on heating
with stearic acid, Mi:issbaner study. 13
relationship with linear shrinkage. 529
stability field. 310
'
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329
Montmorillonite-nontronite series. 304
Mordenite.
in modern geothermal areas. 31
in Miocene sediments of the Tajo basin ..
272
indicator of the lower temperature limit

Subject index 727
of an altering hydrothermal solution.
20
Mullite.
high-temperature phases from kaolinites
with intercalated mineralizers. 385,
386,387,388
Multiple linear regression analysis. 486,496,
529,590
Multivariate analysis of variance.
correlation between genesis and chemical
composition in zeolites. 425
differences of crystal chemistry in Al-rich
smectite types. 426
Muscovite.
27
AI MAS-NMR spectrum. 73
29
Si MAS-NMR spectrum. 74
27
AI and 29 Si isotropic chemical shifts. 76
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329
Nardo basin. 671
Natrojarosite. 218,252
Neogene basin of Madrid. 287
Neogene ~edimentation. "
in the Granada basin. 343
Nevado-Filabride Complex. 265, 342,344
Nickel.
from rocks and soils, balance of matter.
498
Niger river. 126
Nile river. 126
N:itrogen.
in the dust that cover the statues
adorning the Porticos of the Seville
Cathedral. 595
p-Nitrophenol
(see adsorption)
Noce river valley. 629
Nontronite.
effect on decarboxylation and cracking of
stearic acid. 10
'
reduction of structural iron on heating
with stearic acid, Mossbaner study. 13
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329
Nordstrandite.
electron micrograph, infrared spectra and
X-ray diffraction. 393,394,395,396
structural relationship with bayerite and
gibbsite. 396,397
synthesis. 392
Nosova drying sensitivity index.
for evaluating the suitability of raw
materials for the manufacture of
structural ceramics. 532
Octahedral composition.
influence on dehydroxylation of micas
and homoionic vermiculi tes. 406, 407
Octylamine.
(see amine)
Oedometer test.
(see geotechnical properties ... )
Ofanto river valley.
grain-size and compositional
characteristics of clastic materials. 88
granulometric, chemical and
mineralogical pelitic sequence of
sedimentation. 96
relationships with Pliocene sediments of
southern Apennines. 99
source areas distribution and deposition
of the minerals. 99
Orange river. 126
Organic matter.
(see kerogen and pyrolysis)
in the dust that cover the statues
adorning the Porticos of the Seville
Cathedral. 595
influence on the nature and chemical
conditions of the environment during
sedimentation. 251
relationships with micronutrients in soils
from Veg~ de Velez. 486,487
relationship with paleoclimatic
transition in the Tajo basin. 273
with an elevated degree of evolution in
soils deriving from subaerial exposure
of green clays in the Neogene basin of
Madrid. 297
Orinoco river. 126
Oxidation-reduction reactions.
(see pyrolysis)
Padma river. 126
·'

728 Subject index
Palygorskite.
effect on decarboxylation and cracking of
stearic acid. 10
genesis in Villamayor sands tones,
stability conditions. 201,202
in central facies at the Duero basin. 344
in evaporitic Miocene sediments of the
Tajo basin. 271
in Miocene-Pliocene materials at Vera
basin. 261
in pelagic Cretaceous mudstones,
precipitation. 256
in the bentonite of the Fardes Formation,
stability field. 304,310
in the Tertia.ry sediments of the Alameda.
349
polygenesis in a fluvio-lacustrine
environment in the Neogene basin of
Madrid. 296
textural modification by acid treatment,
catalyst. 183
--~- ----~ -----·Panormi·d-e

Subject index 729
systems. oxidation-reduction reactions.
9, 10, 11, 12,13
Pyrophyllite.
27
AI MAS-NMR spectrum. 73
27
AI and 29 Si isotropic chemical shifts. 76
29 Si MAS-NMR spectrum. 73
effect on decarboxylation and cracking of
stearic acid. 10
in uppermost Miocene of the Granada
basin. 342
retention of organic matter by thermal
reaction in a Semi closed environment.
11
stage number for the calculation of the
hydrolysis index. 333
Quantitative analysis of clay and non-clay
minerals. (see X-ray diffraction)
Quantitative determination of gibbsite and
halloysite by Differential Scanning
Calorimetry. 459
Quartz.
equatiOf! for firing temperature
prediction. 590
in ceramic bodies, autoclave treatme~t.
571,572
reflecting power factor. 590
relationship with crushing strenght. 587
weathering index. 329
Quentar Formation. 343
Radioactive wastes.
l.ong-term isolation in deep clay
formation. 709
Red bed clays. 602
Red gres. 535
Residual failure mechanisms.
(see geotechnical properties ... )
Ronda Complex. 489
Rutigliano basin. 705
Salamanca Province. 455
Sangro river. 283
Saponite.
effect on decarboxylation and cracking of
stearic acid. 10
in altered rocks from Los Reales, Malaga.
495
Saraceno Formation. 630
Scanning electron microscopy
(see fabric)
Sepiolite.
acid catalyst. 182
effect on decarboxylation and cracking of
stearic acid. 10
in central facies at the Duero basin. 344
in evaporitic Miocene sediments of the
Tajo basin. 271,272
in Miocene-Pliocene materials at the Vera
basin. 261
polygenesis in a fluvio-lacustrine
environment in the Neogene basin of
Madrid.296
surface acidity. 181
textural modification by acid treatment.
182
Seville Province. 599
Shape and shape factors.
of clay minerals. elongation, flatness,
sphericity. 684
Shear test.
(see geotechnical properties ... )
Shrinkage.
drying, in raw materials for the
manufacture of structural ceramics.
relationships with density and
tempering water, and clay minerals
contents.513,527,529
equation for calculation of. 527
Siderite. 251
Silicification.
influence on genesis offibrous minerals.
288
Skempton colloidal chart.
(see geotechnical properties .. .)
Smectite.
dioctahedral and trioctahedral in
evaporitic Miocene sediments from the
Tajo basin. 273,275
ofbeidellite-montmorillonite series. 223
of montmorillonite-nontronite series. 304
synthesis. 21
trioctahedral, in altered rocks from Los
Reales, Malaga. 495
with variable chemical composition and
tetrahedral charge in bentonites from
Cabo de Gata. 20
Soils.
I
,01

730 Subject index
compacted cohesive. engineering
behaviour related to core earth dam
construction. 693
from Cantabria. developed in areas with
high rainfall and undulating
topography. 514
from Cordillera Central. influence of
organic matter and humidity on the
evolution of. 516
from Emilia-Romagna Region.
mineralogical and geochemical
characteristics, genetic implications.
451,470,471
from Guadalquivir river basim. study of
micromorphological features of clay
translocations. 513
from Jura Region. (see gypsum)
from peridotite in Los Reales, Malaga.
mineralogy and geochemistry,
relationships with mineralogy and
geochemistry of parent and altered
·-- -----roCks. matter balance-s. reflecting
power factors for am phi bole, diopside,
enstatite, olivine and serpentine. 490,
491,492,493,494,495,496,497,498
from Piedmont. clay minerals
distribution in different environments
ofthe Region. 511
from Po valley. (see cation exchange
capacity)
from Vega de Velez, Malaga. mineralogy
and geochemistry. micro nutrients.
correlation of extractable boron,
copper and iron with organic matter,
carbonates and clay content. 485,486,
487
from Vulture v.olcanic complex.
mineralogical characteristics. 208
Specific surface area.
(see beidellite and montmorillonite)
Sphalerite.
in granitic pegmatites from centralwestern
Spain. 345
Spine!.
high-temperature phase from kaolinite
with intercalated mineralizers.385,
386,387,388
St. Lawrence river. 126
Stability fields diagram.
relationships among albite, gibbsite,
kaolinite and Na-montmorillonite at
25°C and 1 Atm., as a function oL[Na:

Subject index 731
stage number for the calculation of the
hydrolysis index. 333
Tetrahedral.
cation ordering, in layer silicates. 77
Thenardite. 269
Thermodynamic.
grinding effects on crystallinity of
kaolinite. 429,430
of the adsorption of chloropropham by ·
clay minerals and soils. 148, 152
of adsorption of macrocyclic compounds
by montmorillonite. 184
of interaction of organophosphorus
pesticides with vermiculite. 181
textural modification of sepi2lite and
palygorskite by acid treatment. 183
Thermogra vimetric analysis.
of altered ceramic sculptures. 596
Topaz.
in granitic pegmatites from centralwestern
Spain. 345
Tourmaline.
associated with lithium-muscovites in
granitic pegmatites from centralwestern
Spain. 345
in Villamayor sandstone. 199 '-
Trace elements.
distribution and behaviour in the Gulf of
Taranto. 351,352
genesis of the Fardes Formation
bentonites. 309
in lithium-muscovites. 345
in soils from Emilia-Romagna region,
. relationships with mineralogy. 469,
470
in soils from Los Reales, Malaga, balance
of matter. 493,498
Triaxial test.
(see geotechnical properties ...)
Tridymite.
disordered. 23
low temperature phase in bentonite. 20
weathering index. 329
Tronto river. 282
Tufiti di Tusa. 218
Turbitic pelites.
in northern and southern Middle
Subbetic realms, differences with
hemipelagites. 254
mineralogical composition. 251
Unconfined compressive tests.
(see geotechnical properties .. .)
UVlight.
detection of chlorthiamid and
dichlobenil. 172
Van der W aals forces.
retention of chloropropham in
intercrystalline pores of
montmorillonite and kaolinite,
interactions between cations and
chloropropham in peat. 150
Vanadium.
from rocks and soils, balance of matter.
498
Van't Hoff equation.
for adsorption isosteric heats calculation.
181
Vera basin.
lithology. 260, location. 260, mineralogy.
261, Miocene-Pliocene boundary. 259,
266, sedimentary environment. 265,
266, stratigraphical and
paleontological investigations. 259
Vermiculite.
27
Al and 29 Si isotropic chemical shifts. 76
2 9Si MAS-NMR spectrum. 74
decylammonium complex 155
electron density profiles for dehydrated
V-Na, V-K and V-Cs. 412
electron density profiles for monolayer
hydrates V-Va and V-Li. 413
homoionic, infrared spectra in the v 0 H
region.413,414,415,416
perturbation of OH groups by interlayer
cations. effect oflarge and small
cations on layer stacking modes. 418,
421
stage number for the calculation of the
hydrolysis index. 333
weathering index. 329
Volume shrinkage. 524
'Vomano river. 281 o 282
Vulture volcanites.
weathering products of. 210,211
Waikato river. 126
Water molecules.

732 Subject index
I
localization in Na-beidellite.
homogeneous one-water-layer state,
homogeneous two-water-layer state.
50, 51,52
Weathering index.
of clay-size minerals in soils and
sedimentary deposits. 329
Weathering sequences:
of acidic volcanic rocks, granites and
gneisses. 347
Weaverindex.353
Western Mediterranean basin. 260
Wol!astonite.
equation for firing temperature
prediction. 590
high-temperature phase. 565,566
in ceramic bodies, autoclave treatment.
571,572
reflecting power factor. 590
X-ray diffraction.
modelling methods of X-ray diffraction
spectra. principle of the method,
mathematical approach. 35;-3o~37-;-3s:~-~-~-·
39
quantitative analysis of clay and non-clay
minerals. 224,234,248,260,261,269,
270,271,279,280,289,304,342,343,
440,463,485,491,514,516,552,568,
571,572,588,589,590,605,611,624,
631,636,650,653,663,674,695,708
X-ray fluorescenc;. 209,220,650
Zeolites.18, 31,272,291,339:425
Zeta potential.
indicator of the electric state of the
__ double layer. 515
Zinc.
from rocks and soils, balance of matter.
498
:,I I
11
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Finito di stampare
ne/ mese di dicembre 1986
dalla Tipegrafia Compositori - Bologna
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