The link between bismuth tellurides and gold: deposits ... - Cmi Capital

The link between bismuth tellurides
and gold: deposits in the Banatitic
Magmatic and Metallogenetic Belt
Cristiana L. Ciobanu
Natural History Museum, University of Oslo, Norway
Nigel J. Cook
Natural History Museum, University of Oslo, Norway
Kamen Bogdanov
Sofia University 'St. Kliment Ohridski', 15 Tsar Osvoboditel Bd.,
1504 Sofia, Bulgaria

Balkans
The Banatitic Magmatic and Metallogenetic Belt (BMMB) is the only one among six
belts with a calc-alkaline signature in SE Europe that has a Cu-dominant character.
W. Carpathians
Bohemian
Massif
E. Alps
Mesek
Budapest
Belgrade
Skopje
Bukk
(Szarvasko)
Axiopolis
Paikon
Pindos
Severin
Sofia
Sithonia
Athens
Argolis
East European
Platform
E. Carpathians
S. Carp.
Black Sea
Bucharest
Moesian Platform
External Dinarides
Internal Dinarides
Vardar zone
3
Complex island-arc &
ophiolite units (see text)
Mid-Hungarian
Line
Undifferentiated ophiolites
2
Pannonian Basin
Pieniny Klippen Belt
& Penninic Units
Trotus Line
SAM
Magura
Dobrogea
Cerbia
Periadriatic Line
Foreland basins
1
External Dacides (flysch)
Kotel
Marginal Dacides
(Danubian)
Adriatic Sea
Srednogorie
1. Late Cretaceous
‘banatitic’ belt (BMMB)
2. Apuseni Mts. (Neogene)
Internal Dacides (Getic)
Rhodopes
Serbo Macedonian
6
50 o
48 o
4
46 o
44 o
Dinarides
42 o
5
Strandza
Transdanubian Ridge
Tisza Block
Aegean Sea
3. Inner Carpathian Arc
(Neogene)
4. Peri-Adriatic Recsk Arc
(Paleogene)
Major tectonic line
Cyclades
Ionian
Sea
5. Lece-Chalkidiki Arc
(Tertiary)
100 km
Othrys-
Evia
20 o 22 o
24 o
26 o 28 o 36 o
6. Drina-Rhodope Arc
(Tertiary)
Inner Alpine-Carpathian
(incl. Bihor, Codru)
40 o
38 o
Carpathian-
Dinaride-
Hellenide
realm
(Sndulescu,
1988;
ophiolites
from Channell
& Kozur, 1997;
metallogenetic
belts from
Mitchell,
1996).
Hellenides
Magmatic &
metallogenetic belts

R. T i s z a
R o m a n i a
R. M u r e
Ocna de Fier
Dognecea
Oravia-Ciclova
Sasca Montan
Belgrade Moldova Nou
Borod-Corniel
Budureasa area
Juleti-Valea Fagului
Mgureaua Va
Poiana Rusc
Banat
Krepoljin
Tincova area
Ridanj
Kuajna
Reškovica
Valja Saka
Valja Strž
S e r b i a
Teregova-
Lpunicel
Bozovici
opot area
Bioara-
Valea Lita
Valea Seac
Brusturi
Cerovo
Veliki Krivelj
Bor
R. J i u
Timok
B u l g a r i a
S r e d n o g o r i e
R. Isker
R. O l t
R. A r g e
R. D a n u b e
Black
Kremikovtsi Elatsite
Sea
Sofia
Vardar Zone
Chelopech
Pozharevo
Yambol Bakadjik Burgas
Medet
Krumovo
Vurly Bryag
Assarel
Dikanyite
Zidarovo
Petelevo
Rossen
Dinarides
Krassen
Vitosha
Radka
Gramatikovo
Skopje
Elshitsa
Tsar Assen
Velikovets
Vlaykov Vruh
Popada
Malko Turnovo
200 km
Panagyurishte
Mladenovo
Burdtzeto
20 24 o 26 Strandza
o 22 o
o 28 o
Neogene calc-alkaline
volcanics
Upper Cretaceous volcanoplutonic
& volcano-sedimentary
complexes
Upper Cretaceous intrusives
Tertiary-Quaternary sediments
East European and Moesian
Platforms
Inner Alpine-Carpathian belt
Apuseni Mts.
Majdanpek
oka Marin
Ruschia
Fig. 3
E u r o p e a n P l a t f o r m
W. Alps
Skarn
Porphyry
Massive sulfide
Vein
Po Basin
Tyrrhenean Sea
400 km
Shear zone hosted
Volcano-sedimentary
Carbonate-hosted
replacement
Eastern Alps
Apennines
Penninic
Adriatic Sea
Bucharest
R. Marika
Western
Carpathians
Pieniny
P a n n o n i a n
Dinarides Hellenides
Irregular body
Porphyry - stock
Vein
Lens
Mure
Fe
Cu
Zn-Pb-(Cu)
Au
M gura
Severin
Vardar
Mo
Mn (Pozharevo)
E. Carpathians
Ceahl u
Moesia
Trojan
Balkans
Rhodope
Suture zone/covered
BMMB
Transylv.
S. Carp.
Area in main figure
44 o
42 o
BMMB deposits are a
variation on the theme
of the magmatic
hydrothermal
continuum, centered
upon calc-alkaline
intrusions (Ciobanu et
al., 2002). The belt is
characterized by exotic
(Bi-Te-Se-Au-Ag-PGE-
Cd-In-Sn-V) trace
signatures – that of Bi is
most prominent (e.g.,
Cook et al. 2002).

Despite evidence that Au-rich ores are
present in virtually all deposits of the belt,
only Chelopech (3.38 g/t Au; 1.24 % Cu), has
been/is exploited primarily for Au.
Considering that 10 of 60 deposits and
prospects in the belt are currently under
mining, the kind of arguments presented
may be applicable to mineral assessment
and prospecting activities in the belt.

Northern
Yambol
Apuseni
Banat Timok
-Burgas
Mts.
Strandza
~30 MT ~525 MT ~3000 MT ~1200 MT ~70 MT
W
1500 km
Vladeasa
Baisoara
Baisoara
~80 Ma
Baita Bihor
Poiana
Rusca
Late Cretaceous surface
Subvolcanic
shallow
skarn &
2-3km porphyry
10 km
Tincova
p
Ruschita
76.5 Ma
Ocna de Fier
Dognecea
~82 Ma
Plutonic
deep seated
skarn
Oravita-
Ciclova
Present-day
level of erosion
Moldova
Noua
Panagy
urishte
Volcanic&subvolcanic
epithermal/porphyry
Majdanpek
~90 Ma
~80 Ma
Bor
Elatsite
Chelopech
Medet Asarel
Radka
Elshitsa
Malko
-Tarnovo
Vein
Epithermal
&porphyry
Skarn
Late Cretaceous Banatitic Magmatic & Metallogenetic Belt
E

Romania Serbia Bulgaria
Apuseni .Mts.
Poiana Rusca
Banat
Timok
Strandza
Yambol
Burgas
Gold speciation in
deposits from the
BMMB
Panagyurishte
Baisoara
Valea Seaca
Baita Bihor
Valea Lita
Valisor-Tincova
Ocna de Fier-Dognecea
Oravita-Ciclova
Sasca Montana
Moldova Noua
Majdanpek
Bor
Elatsite
Chelopech
Assarel
Medet
Radka
Krassen
Elshitsa
Malko-Turnovo district
Bakadjik
Vurly Briag-Zidarovo
Gold ores include
Au(Ag) tellurides in
Panagyurishte
district (Bulgaria).
Maldonite is present
in 2 skarns from the
Romanian districts
Native Au-Electrum x x x x x x x x x x x x x x x x x x x x x
Maldonite x x
Kostovite x
Calaverite x x
Sylvanite x x x x
Krennerite x x
Montbrayite x
Nagyagite x
Buckhornite x x
Petzite x x x x
Fischesserite x
Bakadjik
Baita Bihor
Asarel
Elatsite
Moldova Noua
Grade (g/t)
Contained gold (tonnes)
Chelopech
Majdanpek
V. Krivelj
Bor
The world-class
porphyry
deposits in Bor
district (Serbia)
have the largest
Au tonnages in
the belt.

What types of Au-enrichment mechanisms can we consider
for BMMB deposits
1) The role played by Au-carriers such as Cu-Fe sulphides (Simon et al.
2000; Kesler et al. 2002). Bornite in skarn (Baita Bihor, Ocna de Fier),
porphyry core (Elatsite) and epithermal ores (Chelopech) accounts for
most of the Au endowment in these deposits (Ciobanu et al. 2003).
Chelopech, Bulgaria
Coarsening of exsolved Au
Exsolutions
of Au in
bornite
5 µm 5 µm
pyrite
bornite
Au
2) The role played by Bi-melts as scavengers for Au, as proven by
experiment (Douglas et al. 2000) can be extended to Bi-Te melts (e.g.
Ciobanu et al. 2005). We discuss the Bi-telluride signature in 9 deposits
along the BMMB, and the implications their presence has for
understanding Au formation/enrichment.

Where do we find Au associated with Bi-tellurides in
BMMB deposits
Examples:
• Skarns:
Baisoara, Baita Bihor, Ocna de Fier (Romania),
Majdanpek (Serbia)
• Porphyry:
Moldova Noua (Romania), Elatsite, Assarel
(Bulgaria)
• Epithermal:
Radka, Elshitsa (Bulgaria)

Speciation of tellurides and selenides associated with Au in the 9
deposits under discussion
Mineral Abr. Formula
Apuseni Mts. Banat Timok Panagyurishte
Baita
Bihor
Baisoara
Native Bi Bi Bi x x
Maldonite Mld Au2Bi x x
Hedleyite Hed Bi7Te3 x x x
Joseite B JoB Bi4Te2S x x x
Joseite A JoA Bi4TeS2 x
Ikunolite Ik Bi4(S,Se)3 x
Ingodite Ing Bi(Te,S,Se) x x
Tsumoite Ts BiTe x x x x x
Tetradymite Td Bi2Te2S x x x x x x x x x
Kawazulite Kw Bi2Te2Se x x
Tellurobismutite Tbs Bi2Te3 x x x x x*
Native Te Te Te x x x
Petzite Pz AuAg3Te2 x x x
Calaverite Cal Au2Te x*
Sylvanite Syl AuAgTe2 x x*
Krennerite Kr Au1.8Ag1.2Te2 x* *
Buckhornite Buk (Pb2BiS3)(AuTe2) x x*
Fischesserite Fss AuAg3Se2 x
Native Au Au Au x x x x x x x x
Native Ag Ag Ag x x
Hessite Hs Ag2Te x x x x x x x x
Stutzite Stz Ag5Te3 x x
Cervelleite Cerv Ag4TeS x x x
Volynskite Vol AgBiTe2 x x
Bohdanowiczite Boh AgBiSe2 x x x
Clausthalite Cls Pb(Se,S) x x x
Altaite Alt PbTe x*
Ocna de
Fier
Moldova
Noua
Majdanpek
Elatsite
Assarel
Radka
Elshitsa

46º N
NORTHERN
APUSENI
MTS.
Hungary
Arad
Timi oara
T i m i
B î r z a v a
Serbia
C a r a
N e r a
Baita Bihor
C r i s u l A l b
M u r e s
B e g a
Ocna de Fier
BANAT
D a n u b e
Upper Cretaceous
Intrusive (granite,
granodiorite, diorite)
Caransebes
Orsova
Volcanic/volcano-sedim.
(rhyolite, dacite, andesite)
Poiana
Rusca
23º E
S o m e
R î u M a r e
A r i e
METALIFERI
MTS.
Deva
Cluj
Baisoara
R O M A N I A
SOUTHERN CARPATHIANS
Bucharest
Neogene
M u r e s
Subvolcanic
(andesite, dacite)
Volcanic
(andesite, dacite)
Skarns not associated with
porphyry: Baisoara, Baita Bihor (N.
Apuseni Mts.); Ocna de Fier-
Dognecea (Banat)
All are oxidised skarns (Grt>Px;
Meinert 1992)
All include early forsterite; humite
at Baita Bihor and Baisoara only.
Associations of exotic trace
elements, including a common-toall
Au-Bi-Te signature, are
abundant especially throughout
parts of the orebodies with intense
retrograde overprinting.

Apuseni Mts.
HB SZ.
Moesia
Trojan
Apuseni Mts.: Two skarn deposits are situated at the E, Baisoara, and W,
Baita Bihor, sides of this tectonic unit, along the Highis-Biharia Shear
Zone (HBSZ).
The role that inherited tectonics may have played in focusing fluids can
explain why these are the only two skarn deposits in the Apuseni Mts.,
even though there are several other prospects and many banatite
intrusions which could have ’produced’ mineralisation.
E u r o p e a n P l a t f o r m
Iara River
Crisul Negru R.
Highis Mts.
DroceaMts.
Biharia Mts.
Aries R.
Somes R.
20 km
Cluj
Biharia
Gilau Mts.
Baisoara-
Valea Lita
Biharia
Baita Bihor
Muntele
Mare
Poiana
Biharia
Arieseni
Paiuseni
Trascau
Mts.
Crisul Alb River
N
Lipova
Paiuseni
Brad
Post tectonic deposits
Late Cretaceous ‘Gosau’-type
strata(post-Austrian cover)
Late Jurassic & Early Cretaceous
mostly flysch strata
Permian to Barremian-Aptian
mostly platform strata
Jurassic ophiolites &
island arc volcanics
HIGHIS-BIHARIA SHEAR ZONE (HBSZ)
HBSZ (Pana & Erdmer
1994) is a Variscan (300-
320Ma) greenschist belt
with Alpine overprint
(100-114Ma) (Dallmeyer
et al. 2002) marking the
boundary between N and
S Apuseni Mts.
Ca rpathians
Western
Pieni ny
Eastern Alps
E. Ca rpathians
Magura
W. Alps
P a n n o n i a n
Penninic
Severin
Ceahlau
Transylv.
Po Basin
S. Ca rp.
B MMB
B MMB
Adriatic Sea
Apennines
Balkans
Vardar
Tyrrhenean Sea
400 km
Neogene volcanics HBSZ
Suture zone/covered
Alpine orogen
Area in main figure
Rhodope
Dinarides Hellenides
Highis/Biharia igneous core,
a) phyllonites
a
Baia de Aries carbonatelenses
gneissic assemblage,
a) retrogressed
Codru granite-intruded
amphibolite assemblage
a
Muntele Mare granite
Somes gneiss-granite
assemblage, a) retrogressed
a
Thrust
Skarn
Mures River

Valea Lita Shaft
Zn(Pb) skarn
BAISOARA
Baisoara Shaft
Fe skarn
Mieilor V.
Iara Valley
Masca Shaft
Fe skarn
Almasel V.
N
a
a
a
Qauternary, a) alluvial
Middle Miocene
Paleogene (banded clay,
conglomerate, sandstone)
Late Cretaceous intrusion
(granodiorite, granite, rhyolite)
Campanian Maestrichtian
(conglomerate, sandstone,
marly- limestone)
Gilau crystalline
Micaschist, a) limestone
Gneissic granite, a)albiteporphyroblast
amphybolite
schist
Fault
Magnetite: Fe
ore ca. 10 Mt
Marble
Baisoara-Valea
Lita Fe(Zn-Pb)
skarn
Zn-Pb ore in
Cacova mine.
10 cm
10 cm
Cacova Ierii Shaft
Fe skarn
CACOVA IERII
1 km
Gold was never a target in the skarn ore
although we found that this is present in
the deepest level of Masca orebody.
Exploitation stopped because this part of
the orebody is dominantly formed by Fe
sulphides rather than magnetite.

SSW
4 km NNE
N194 N280 N220 N140
N155 N218
Cacova
Masca Baisoara Valea Lita
Distal
Zn(Pb)
skarn
-100
-200
-300
-280
-400
Au and Bitellurides
Sulphidation
a
Continental shale
(Ypresian-Lutetian)
Banatite (granodiorite)
Schists, a) limestone
-500
a
Zn-Pb ore
Fe ore, a) exploited
Skarn (garnet, pyroxene, epidote)
Hornfels (tremolite, actinolite)
Mg-skarn (forsterite, humite,
ludwigite) occurs at deeper
levels whereas the calcic
skarn (andradite, diopside)
form the upper parts. No Mgskarn
is formed in Valea Lita.

Magnetite
Marcasite/Pyrite
Calcite
Cal
Pyrrhotite
Diopside
Retrograde stage is marked by replacement of magnetite by pyrrhotite - most
intense in the lower parts of the orebodies. This is followed by a second stage
of sulphidation when pyrite/marcasite replaces pyrrhotite.
At Valea Lita such sulphidation is also accompanied by formation of sphalerite
(up to 20 wt. % FeS). Some pockets of sphalerite (

Magnetite
Bi-tellurides
Magnetite
Bismuth
50 µm
Baisoara
Forsterite
Au
Hedleyite
The presence of Au and maldonite in such
blebs was noted only in Baisoara
Brecciation during the sulphidation stages is marked by trails with blebs/patches
of native Bi, Bi-tellurides (+Bi-sulphosalts) in both Baisoara and Valea Lita.
Bi-tellurides& Bi-ss
Sphalerite
And 25
Gr 75
Bismuthinite
Bi
And 95
Chalcopyrite
Valea Lita
Valea Lita

Tetradymite is formed during retrograde reactions that increase sulphidation state
leading to replacement of pyrrhotite by pyrite
Bi
Bism
Au&
Bis
m&
Ttd
Joseite B
Skeletal Au formed during sulphidation
of an assemblage with joseite B and
maldonite:
maldonite + joseite B + Sulphur
Au + tetradymite + bismuthinite
(2Au 2
Bi+Bi 4
Te 2
S+3S 2
=
4Au+Bi 2
Te 2
S+2Bi 2
S 3
)

Se+S
BiS
Ik
Baisoara
Valea Lita
JoA
Ing
JoB
Ttd
Bi+Pb
Hed
Pls
Ts
Tbs
Te
Two distinct Bi-telluride
associations can be defined
based on Bi/(Te+S+Se) (R):
1) maldonite+Au+Bi+Bi-tellurides
with R>1 (hedleyite, joseite A
and B, ikunolite)
2) Au+Bi-tellurides with R

Baita Bihor Cu (Mo, Zn-Pb) skarn; 2Mt
Triassic J1-2
Pre-skarn dikes
(lamprophyre, andesite)
Bihor Autochton
Barremian
Codru
Liassic/Dogger
Norian
Carnian dolomites
Anisian /Ladinian
Arieseni series
Permian shale,
sandstone
Fault
Thrust
Blidar Contact
Molibden
Level VI
1 km
Codreanu V.
Codreanu V.
G. Codreanu
G. Speranta
Molibden
G. Cosuri
Cosuri
Bernard
868.2
Crisul Negru V.
G. II Molibden
Ponor V.
Corlatu V.
Izv Cris
983.4
G. Ladislau
G. Borului
Antoniu
Corlatu
Cu(Mo,Zn-Pb)
N
G. Toni-Bolfu
Baia Rosie-Marta-Bolfu-Toni
Plesuta V.
Mo Zn-Pb(Cu,Mo)
Frasinel
1124.4
Hoanca Motului V.
Proximal Distal
Antoniu Fault
sphalerite&galena
bornite
marble
bornite & sphalerite
garnet
Gold is a target for the present exploitation. Deeper parts of Antoniu have grades of
1-2g/t Au in bornite ore, also rich in Ag, and Bi. The intersection of theAntoniu and
Blidar faults is considered the main control for this trend (mine geologist O. Kiss).

Baita Bihor Cu (Mo, Zn-Pb) skarn; 2Mt
WSW
800
4 km
Antoniu
Ocna Rosie
Marta
Bolfu-Toni
ENE
600
400
200
Blidar Contact
Level XVII (+269m)
Level XVIII (+227 m)
Antoniu N
Speranta +576m
Blidar Contact
BBH (1291)old sample
ca 80 Ma,
Mol in granite -500m
0
-200
-400
Ladinian limestone
Werfenian
Permian shale,
sandstone
a
Norian limestone
Carnian dolomite
Anisian limestone
a) quartzite
Orebody
Granite (banatite)
Dyke (lamprophyre,
granite, andesite)
Hornfels
Intrusive dyke
Marble

GOLD and Bi-tellurides in ANTONIU PIPE (main ore is Cu)
Tetradymite is present in
samples with rare Bi-sulphosalts
from the upper part of Antoniu.
Textures indicate that this is
formed during retrograde
overprint of such assemblages.
Aikinite displacement
Tetradymite
Makovickyite
Cuprobismutite
Tetradymite
Aikinite
Paderaite
Makovickyite
Cuprobismutite
Tetradymite

ANTONIU PIPE
N
Exploited
Mo
Breccia
Zn-Pb
Level XV
356 m
Ab. 333 m
Level XVIII
227.5 m
Bi-tellurides
and Au
Antoniu pipe
Native Cu
Ab. 3
278 m
Au @ 4g/t
Ab. 1&1bis Dolomite
235 m
Ab. 2A &B
325 m
Mineralised
skarn
Zn-P b in
breccia
Tr. 11
Limestone
Tr. 13
6
Ni-Co signature
7
Mineralised dyke
13
Skarn
Hornfels
Antoniu N pipe
Ab. 3-4
278 -278 m
Minute grains of Au are
included in Bi-telluride
patches associated with
fluid inclusion trails in
this sample.
Cp ore (Po-Mt buffered) in forsterite-diopside (Di 93-64
Hd 7-36
)
skarn from the deeper part of Antoniu (currently under
exploitation).

ANTONIU PIPE
Chalcopyrite
Small pyroxene grains are also formed
along the same fluid inclusion trails.
Forsterite &
Diopside
Cp
Di 97 Hed 3
Di 62 Hed 36 Joh 3
Fo & Di
Retrograde front
with
precipitation of
Bi-tellurides
(tetradymite,
tellurobismutite)
and Au.

Bi-tellurides in distal Zn-Pb
skarn from Marta
This pipe is formed at the
contact with one of the
lamprophyre dikes that was
transformed into diopside
skarn. Tellurides are associated
with retrograde brecciation that
also brings in apatite. In
contrast to Antoniu, the
tellurides are represented by
hedleyite and joseite B (R>1).
apatite
apatite
diopside
10 µm
hedleyite
joseite B
S+Se
50 µm
joseite B
Ik
JoA
Ing
Bi/(Te+S+Se)1
Hed
Bi2Te
Pls
Tsm
Rkl
Tbs
Te
1) BB1: Bi-tellurides with R1, in Marta

Banat District
LMDSZ
Skarn and porphyry depsoits
are placed along the contact
between Jurassic-Early
Cretaceous sediments
(carbonaceous units) and
crystalline schists along the W
border. With the exception of
Ocna de Fier-Dognecea, all
other deposits are Cu skarns
with associated porphyry
systems.
This alignment follows the
Alpine Lescovita-Maciova-
Dabica Shear Zone (LMDSZ)
(Pana and Erdmer, 1994). Au
prospects hosted within
schists along the LMDSZ are
targeted at Oravita.

Valeapai-Nadrag-
Cincis-Shear Zone
(Pana& Erdmer, 1994)
LMDSZ
Ocna de Fier-Dognecea, located in
the uppermost nappe from Banat
(Supragetic Domain), is the only
skarn that lacks connection with a
porphyry system.
2 cm

Ocna de Fier-Dognecea
Fe (Cu, Zn-Pb) skarn;
15Mt, 2Mt Cu ore
10 km strike, narrow
contact aureola
Deep-seated skarn
(Nicolescu & Cornell, 1998)
Closed in 1993
Au exploited from Cracul
cu Aur (Romans), Iuliana,
Valea Lacului Mic (18th
Century)
Typical
rhythmically
banded
magnetite
ore
1 cm

OCNA DE FIER – DOGNECEA Fe(Cu,Zn-Pb) skarn
Proximal: Fe-Cu/Fe; Distal: Zn-Pb
The Cu-Fe
15 Mt ores; 40-45 % Fe; 1 % Cu, locally 1-2 g/t Au
core: deepest
part of Simon
Iuda orebody
(Cook &
Ciobanu 2001)
core
Mt
Forsterite
2 cm
Bn
Ciobanu & Cook Fig. 2
Mt
400 µm
South
Valea Enoanea
5.5 k m < < < < < < < D i s t a n c e f r o m S i m o n I u d a t o D o g n e c e a < < < < < <
Dognecea: distal reducing
Au &
scheelite
Au&Bi-tell
Proximal oxidising
(R > > > > > > > D i s t a n c e f r o m S i m o n I u d a t o P a u l u s > > > > > > 4.5 km
Au
Au&Bi-tell
(R>1)
Paulus: distal oxidising
North
Au &
scheelite
Valea Ferendia
Limit of distal skarn
Pb-Zn chimneys in
limestone
Pb-Zn pyroxen e skarn
Dognecea
Low grade Fe ore in g arnet skarn
Limit of pro ximal ore
Zn-Pb zone
Fe zone in calcic skarn
Cu-Fe zone in Mg-skarn
Supergene-enriched Cu ore
Source
Fe
Cu
Pb
Zn
Elias
Liesegang banding
Massive ore (60% Fe-ore)
30-60% Fe-ore
< 30 Fe-ore in calcic skarn
Reichenstein
Limit of distal skarn
Granodiorite
Limestone
Schist
Altered fractured ore
Breccia zone in schist

Fo
Cp
Ap
Simon Iuda: Retrograde devolatilisation
following forsterite formation is recorded
only in the Cu-Fe core - represented by
formation of minerals such as valeriite,
phlogopite, ludwigite and apatite. It marks
the boundary to the Fe zone (Di70-90-
And70-90) (Ciobanu & Cook, 2004).
Sp
Cp
Apatite cluster
20 µm
Srp
As-bearing apatite:
turneaureite,
Ca 5
[(As,P)O 4
] 3
Cl
Apatite clusters contain
blebs of Bi-Ag
tellurosulphides, selenides
& Au (small arrows)

Bogd
Se
Me/(Te+Se+S) = 1
Nev
Te-nev
Kw
Bogd
Hs
Wit
Ag+Bi
Tsm
Ing
Vol
Tbs
Ttd
Te+S
Te-nev
Te-nev
Tbs
Vol
Cu-Fe core-
Simon Iuda: Bitellurides
with
Bi/(Te+S+Se)

Ing
Ttd
A second association of Bi tellurides (R>1; OdF2), native Bi, Au and
maldonite is present in blebs along trails that crosscut magnetite in distal
Zn-Pb skarn at Paulus (4.5 km N of Simon Iuda), hosted within calcic
skarn (HedJoh>60).
Distal skarn: Paulus
S
Mld
Au
Bism
Jo
Bi
Hed
Pls
Tsm
Rkl
Tbm
Te
Orebodies in Paulus have Fe ore with
hematite at the lower part and Zn-Pb ore
at the upper part. Retrograde stage is
characterised by fO2 decrease that
induces formation of magnetite after
hematite. Hematite is again formed
along cleavages in magnetite outwards
from late fractures.

MOLDOVA NOUA
orefield
N
FLORIMUNDA
Cu skarn
(underground)
Baronului V.
MOLDOVA NOUA
Lake
Radimna V.
Western tectonic line
SUVOROV
porphyry Cu&skarn
(open pit)
Valea Mare
Moldovita
NW Mol stock
Og. Rau
Moldovita-Colonovat synclinorium
a
Quaternary
Late Cretaceous
granodiorite (banatite);
a) contact aureola
Albian-Cenomanian
Late Aptian
(Minis strata)
Low Aptian-Hauterivian
(Plopa limestone)
Valanginian-Berriasian
(Crivina marls)
Late Tithonic
(Marita limestone)
Low Tithonic
(Bradet limestone)
Low Kimmeridgian-
Late Oxfordian
(V. Aninei limestone)
Triassic
Crystalline schists
Fault
Moldova Noua orefield (500Mt) includes
a large porphyry Cu stock (Suvorov-
Valea Mare), and two small Cu skarns in
the N and S. However, the high grade
ore is associated with patches of calcic
skarn within the porphyry stock.
Ore
Skarn
Granodiorite
Limestone
SUVOROV
Mining plan
level -209 m (+20m)
VALEA MARE
porphyry Cu&skarn
(underground)
VARAD
Cu skarn
(underground)
Vard Crest
VALEA MARE
3 km

Brecciated andradite
skarn replaced by
calcite+epidote
Brecciated pyrite in
andradite skarn.
Typical brecciation in the ores from the -209m level where
tellurides and Bi-sulphosalts are present.
Single tetradymite
blebs in pyrite
More
complex
blebs (Ag
tellurides
and Ag-Bi
sulphosalts)
are formed
in dilational
sites along
fractures.
Cervelleite
Matildite
Hessite
5 µm

Valea Mare-Suvorov porphyry: Bleb morphology of tetradymite in pyrite
indicates that crystallisation followed deposition of a molten precipitate. Some
of them have ’feeding’ necks resembling fluid inclusions.
10 µm
Au in pyrite
Fluid inclusion trails

Timok Massif, Serbia
Majdanpek
Bor
Veliki Krivelj
Valja Strz
Intrusion
Massive ore
Limestone
Skarn
Andesite
Porphyry stock,
a) disseminated
Deposits from Bor District,
Timok Massif (Serbia) include
world-class porphyry Cu, with
epithermal massive sulphides
at the top. Even though
limestones are present, skarn
formation is only minor. The
largest deposits (Bor,
Majdanpek) are centred on
intrusions situated at deeper
levels and intersected only in
drillcores.

MAJDANPEK orefield map
Zn-Pb skarn
Tenka 1 & 2 & 3
530m
W
590
560
530
Tenka North Revir
Drillcore
E
a
Zn-Pb skarn ore
Massive Cu-pyrite ore
a) disseminated
(in andesite)
Dolovi 1
440m
500
Andesite
Limestone
0,1% Cu
0,2% Cu
470
Gneiss
440
Dolovi 2
410
Southern pit
main Cu ore
(massive &
porphyry Cu)
380
350
Pyrite ore
Zn-Pb ore
0,3 % Cu
N
500 m
Quaternary
Late Cretaceous
Andesite lava
Late Cretaceceous
Senonian flysh
Jurassic-Cretaceous
limestone
Crystalline schists
(group II)
Paleozoic granite
Crystalline schists
(group I)
Fault
10 cm 10 cm

Majdanpek: Zn-Pb skarn
Trails of Bi-tellurides (tetradymite,
tellurobismutite) and sulphosalts
(bismuthinite derivatives) in skarn
ore from Tenka 1 & Severni River
An average grade of 1.3 g/t Au (Jankovic et al. 2002) is given for these bodies

Majdanpek: Zn-Pb skarn
Deposition of Bi-tellurides &
sulphosalts accompanies
brecciation of pyrite and
formation of Zn-Pb ore. Skarn
minerals are present within
sphalerite.
Di46Hed38Joh16.
Sphalerite
Di94
Pyroxene with Fe-Mn–rich rims
within sphalerite
Small grains of pyrite formed during this stage are slightly deformed and
tetradymite and/or bismuthinite fills intergranular spaces (arrows).

Elatsite
N
Chelopech
Assarel
Panagyurishte
Krassen
Vlaikov Vruh
Medet
Elshitsa
Petelovo
Radka
YUG
MAC
Tsar
Assen
Romania
Sofia
BULGARIA
SZ
Panagyurishte
Greece
Aegean
Sea
0 3 km
Black
Sea
Burgas
Turkey
Tertiary alluvial sediments
Upper Cretaceous
intrusions
Andesite and dacite
lavas and tuffs
Maastrichtian flysch
Triassic limestones
Pre-Mesozoic
basement
Deep faults of
Panagyurishte
Corridor
Epithermal
Cu-Au deposits
Porphyry-copper
deposits
Gold is/was exploited as
by-product in most of the
deposits in Panagyurishte
district (Bulgaria; e.g.
Bogdanov et al., 2003). The
most diverse range of Au
tellurides is known from
both epithermal and
porphyry deposits in the
district (e.g. Bogdanov et
al., 2004). Even though
native Te and 7 different
Au-tellurides are present in
the HS epithermal deposit
at Chelopech (e.g. Terziev,
1968; Petrunov, 1995;
Bonev et al., 2004), there
are no Bi-tellurides as
such.
They are however
abundant in chalcopyritepyrite
ores from both
deposit types. Importantly,
they are associated with
Au-tellurides and Au.

Elatsite porphyry Cu(Au)
Pd2Te
Bn
Cov&Cc
Bn-Mt-Cp ores in the preserved K-
alteration core in the Cu(Au)
porphyry at Elatsite are precious
metal-rich
(Tarkian et al. 2003; flotation
concentrates: Au 13.6 g/t; Ag 33
g/t; Pd 0.72 g/t; Pt 0.15 g/t; at Cu
25.6%).
Au
Remobilisation of
exsolved Au during
subsequent boiling
Bn
Mt

In the core: Tesylvanite
Te
Sylv
hessite
tetradymite
Bi-tellurides & sulphosalts
in chalcopyrite-pyrite ores
surrounding the core (red
dotted line)
aikinite

Cp
Td
Hs
Ai
The Assarel porphyry features abundant Bitellurides,
selenides and rare Bi-sulphosalts in
chalcopyrite-pyrite ores.
Fischesseite: AuAg3Se2
Hessite

Bi-tellurides
are found along
brecciation
trails.
Td
Hs
Bohdanowiczite
Td
Td
Hs
Ag-Cbs
Mutual boundaries inside
the blebs suggest melt
precipitation

Epithermal deposits in
southern Panagyurishte:
Radka and Elshitsa
NW
923
Radka
fault
149
907
SE
300
0
Granodiorite porphyry
Subvolcanic dacite
-300
-600
Dacite ash tuff
Dacite agglomerate
tuff
Andesite agglomerate
and ash tuff
Andesite lava
and breccia
Cu-Au sulphide orebody
Pyrite-dominated
orebody
Fault
149 Drill hole
SW NE
7
9 Elshitsa fault
12
13
0 200 400m
370
Subvolcanic
dacite
Granodiorite
140
-90
Effusive dacite
Cu-Au sulphide
orebody
Pyrite-dominated
orebody
Anhydrite
Fault
0 200 m
9
Drill hole

Both epithermal deposits, Radka (HS) and Elshitsa (LS) features similar
tetradymite-aikinite associations in brecciated pyrite-chalcopyrite ores.
Position of the Bi-telluride blebs along fractures
clustered by fluid inclusion trails, as well as their
shape, is highly indicative for contemporaneous
precipitation.
1 cm

HS epithermal: Radka
Chalcopyrite-pyrite ore contains Au-tellurides together with Bi-tellurides
in complex blebs (sulphosalts and sphalerite)

Elatsite
Assarel
Radka
Radka
Elshitsa
The association tetradymite-aikinite (CuPbBiS 3 ) is common to
porphyry and epithermal ores in Panagyurishte.
It is formed during events marked by strong brecciation and
suggests precipitation of such blebs in a molten state, together with
abundant fluid inclusions. When present, Au-tellurides are included
in the blebs, whereas Au may also be as single grains

Bi
Ikunolite
4/3
Joseite A
1/1
Joseite B
Hedleyite
2/3
Ingodite
Pilsenite
S+Se
Tetradymite
Tsumoite
Ruckligeite
Tellurobismutite
Porphyry Cu Elatsite (Cp ore)
Porphyry Cu Assarel (Cp ore)
S+Se
Te
Bi
Bi/(Te+S+Se)>1
Cu skarn Oravita
Cu skarn-porrphyry Moldova Noua
Zn (Pb) skarn Majdanpek
S+Se
Bi/(Te+S+Se)

How can Bi-tellurides scavenge Au from hydrothermal fluids
Metals precipitated above their melting points (as melts) from fluids can
extract Au from those fluids as proven experimentally for native Bi (Douglas
et al. 2000). Using hydrothermal fluids undersaturated in Au for the
experiments, this mechanism was shown to be a more efficient alternative in
extracting Au from a fluid than precipitation upon saturation, i.e. a proper
‘scavenger’ for Au. The templates of many Au skarns (Meinert 2000) and
orogenic Au (e.g. Maiskoe, Ukraine; Cook et al. 2002) replicate experiments of
Douglas et al. (2000) below the Po/Py buffer.
BS1
Bismuthinite
(Bi 2
S 3
)
Maldonite
(Au 2
Bi)
Au
Fractionation of melts from a fluid
(precipitation of metals above the
solvus curve) is controlled by two
factors: (1) temperature above m.p.
(T melt ) along the liquid/solid curve, and
(2) insolubility of metal-complexes in
the fluid at the respective temperature.
The latter is, in turn, controlled by
chemistry of the fluid, e.g.
sulphidation/oxidation (fS 2 /fO 2 ) and
redox (Ph/Eh) characteristics of the
fluid.

Bi
Hedleyite
The only eutectic on the Bi side
in the Bi-Te system (BS1).
0
Temperature ( C)
Wt. % Te
588
600
Bi-rich side eutectic: 540 562 59.8
Bi & hedleyite,
500 266 0 C
420
413
400
375
90
312
300
Te-rich side eutectic:
271.442 266
Te & tellurobismuthite,
2.4
413 0
C
200
100
0
10
20
Bi7Te3 (Hed)
Bi2Te
30
Bi4Te3 (Pilsenite)
40
BiTe (Tsumoite)
Bi6Te7
Bi4Te5
50
Bi2Te3 (Tellurobismuthite)
60
70
80
90
100
449.57
Conditions for ’melt precipitation
windows’ for Bi-tellurides depend on
which of the Bi-rich (R>1) or Te-rich (R1 is constrained at temperatures
>266 o C and reducing conditions (stability
of Bi; Skirrow & Walshe 2002)
R413 o C and oxidizing conditions
(stability of Te; e.g. McPhail 1995).
0
0
Bi
10
20
30
40
The only
eutectic on
the Te side
in the Bi-Te
system
(Majdanpek).
50
At. % Te
60
70
Te
80
90
10 µm
100
Te
After Okamoto and Tanner (1990)
Tbs

Liquid Bi can incorporate as
much as 17 at. % Au beyond
the solubility capacity of any
fluid at any temperature. The
potential of melts to dissolve
Au is even higher for Bi-Te
melts (10-37 at. % Au) - see
eutectics in the Au-Bi-Te
system
System Eutectic Melt (at. %) T (ºC) References
Bi-Au maldonite+Bi Bi 82.8 Au 17.2
241 Okamoto & Massalski (1983)
Bi-Te-Au Bi 5 Te 3 +maldonite+Bi Bi 84.5 Au 14 Te 1.5
235 Gather & Blachnik (1974)
tellurobismuthite
+calaverite + Te
tellurobismuthite
+calaverite + Au
Bi 7.5 Au 10.5 Te 82
383 Gather & Blachnik (1974)
Bi 10 Au 37 Te 53
402 Gather & Blachnik (1974)
Bi-Te hedleyite + Bi Bi 97.6 Te 2.4
266 Okamoto & Tanner (1990)
tellurobismuthite +Te Bi 10 Te 90
413 Okamoto & Tanner (1990)
In BS1, droplet chemistry represents a
compositional range close to the eutectic on the
Bi-rich side of the Bi-Te system.
After Okamoto & Masaalski (1983)

Hm
Mt
Hm
Mt
Cc + Qz
Wo
And + Qz
And + Qz
Di90Hed10
Hem
+ Cc
+ Qz
And
Di90Hed10
Qz
Hd + Wo
-15
Mt
And90-70
And90-70
Fa
Td/Tbs+Bism
Tbs/Td+Te
Cal/Syl+Te
Gr
Di10Hed50Joh40
-20
OdF1
Mt+Bn
Po+Bn
-25
Hed +
Qz Qz + + Mt Mt
BB2
OdF2
Mt
Mt+Bn
Log f(O 2)
Log f(O 2)
Di10Hed50Joh40
Po
Cos
Gb
Fe-Act
Fe-Act
And
And
Mt
+ Cc
+ Qz
Py
-30
Po Po
Hed + Mt + Cc
300
BB1
Po+Bn
BS2
400
BS1
Cos
Gb
Hed +
Qz Qz + + Mt Mt
Fe-Act
And
Hed + Mt + Cc
And
Mt
+ Cc
+ Qz
Py
Po Po
500
o
T ( C)
600
700
o
T ( C)
600
700
Bi+Hed
Bi+Bism
Hem
+ Cc
+ Qz
And
Cc + Qz
Wo
Qz
Hd + Wo
-15
Mt
Fa
Td/Tbs+Bism
Tbs/Td+Te
Cal/Syl+Te
Gr
-20
-25
Mt
ELA
ORV
MN
Po
ASR
Fe-Act
RDK
MJ
ELH
-30
300
400
500
Bi+Hed
Bi+Bism
Rectangle: epithermal (HS&LS); Star: porphyry
Circle: skarn associated with porphyry
Eutectics shown in the blebs that form the
telluride association with R1: native Bi + hedleyite at
266 o C; Okamoto & Tanner 1990; native Bi +
bismuthinite at 270 o C; Lin et al. 1990) indicated by
the blue dashed line. Maldonite + Bi at 241 o C
(Okamoto & Masaalski 1983) is not shown.
Position of each telluride
association for the 9 deposits in
fO 2 -T diagrams. The 3skarns
without porphyry systems
shows a higher spread in
comparison with the other
deposits. Common to all is the
association R

t
Based upon stability of native Bi (Skirrow &
Walshe 2002) and that of native Te (e.g.
McPhail 1995), as well as the
thermodynamic data of Afifi et al. (1988),
the ratio R can be used to discriminate
associations formed in reduced
environment (Po, Mt stability; R>1) from
those formed in oxidised (Py, Hm stability;
R

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