The PGE potential in Greenland

The PGE potentialin GreenlandNo. 8 - February 2007

THE PGE POTENTIAL IN GREENLANDChromitite banded anorthosites from the Fiskenæsset anorthosites complex, southern West Greenland. Photo: GEUS.phosed under amphibolite – and locallygranulite facies conditions.ExplorationPGE exploration has been limited. In the1970s Platinomino A/S searched for Merenskytype platinum deposits. The impetuswas the discovery of an approx. 1 metrewide bronzitite layer with discrete chromitebanding. The bronzitite contains minornickel sulphides. Assays gave very promisingresults of up to 0.6 ppm Pt and 3 ppmPd which, however, could not be confirmed.In 1980 study of one stratigraphicalsection in the anorthosite complex showedthat PGEs are concentrated mainly in ultramaficlithologies and chromitites. The lattercontain up to 310 ppb Pt, 175 ppb Pdand 220 ppb Rh. Similar concentrationsalso occur in anorthosites and leucogabbrosrich in disseminated sulphides.In 1991 GEUS resampled the bronzititeand a few other parts of the anorthositecomplex. The bronzitite gave 74 ppb Pt and115 ppb Pd. In other parts of the anorthositecomplex, several-hundred-metre-thickBronzitite layer in anorthosites from the Fiskenæsset anorthosites complex, southern WestGreenland. Photo: GEUS.3

THE PGE POTENTIAL IN GREENLANDGEOLOGY AND ORE 8 / 2007Drilling in dunite by NunaMinerals A/S in the Fiskevandet region, southern West Greenland. Photo: NunaMinerals A/S.ment textures. The average sulphide contentin the mineralised rocks is around 2vol.% and locally up to 25 vol.%.The Ni-Cu sulphide occurrences show arather uniform Pd /Pt, but the absoluteconcentration is dependent on the sulphidecontent. High concentration - up to2.7 ppm - is believed to be the result ofremobilisation.Exploration and ore compositionNunaMinerals A/S acquired the Fiskefjordlicenses in 2005 and initiated PGE explorationsoon after. Stream sediment samplesdemonstrate a wide range of PGE concentrationsfrom weakly anomalous to a maximumcontent of >600 ppb, combined Ptand Pd. NunaMinerals named the twoprospect subareas Amikoq and Fiskevandet.Exploration drilling is ongoing in the Amikoqarea.Analysis of whole-rock samples has returnedvalues up to 4.5 ppm PGE (com-Fiskefjord–Amikoq:Ultramafic intrusions: irregular bodies ofdunite and peridotite.Several layered mafic to ultramafic intrusionsare embedded in a supracrustal beltwithin the Archean gneiss terrain. Igneouslayering is common, despite strong deformation.Sampling site in scree with Pt-enriched weathered amphibolite bordering dunite, Fiskevandet region,southern West Greenland. Photo: NunaMinerals A/S.6

THE PGE POTENTIAL IN GREENLANDHornblendite intrusion from the Amitsoq locality, South Greenland. Photo: GEUS.bined) and samples show high Pt/Pd ratios.Most samples have high contents of Crand Ni (up to 3.7 % and 2.8 %, respectively)and moderately high Cu. The majorityof samples are depleted in S and sulphidesare rarely observed in hand specimens.Whole-rock samples are Pt-dominatedwith Pt/Pd ratios around 2.7. Cu/Pd displaysa wide range, indicating that the physicalconditions were favourable for substantialPGE enrichment in the melt during mantlemelting. The parental magma(s) were relativelyPGE-rich and S-undersaturated andcould potentially have generated significantPGE mineralisation. A high Pt/Pd ratio isobserved at three localities.Tasiilaq:Ammassalik Igneous complex.The syntectonic norite complex is locatedwithin the northern half of the AmmassalikMobile Belt, assumed to be the easterncontinuation of the Paleoproterozoic Nagssugtoqidianorogen in West Greenlandand the Torngat orogen in Canada. Thebelt consists of alternating re-workedArchaean rocks, with tectonically interleavedsheets of quartzo-feldspathic orthogneissesand early Proterozoic supracrustalrocks including komatiitic ultramafics.The Ammassalik Igneous complex in theTasiilaq area is enveloped by supracrustalgneisses and has been the object of explorationsince 1995. Exploration in the AmmassalikIsland and Kitak concessions hasbeen conducted since 1998 by NunaMineralsA/S and later by Inco Ltd and DiamondFields International. A joint venture operationbetween Diamond Fields Internationaland GEOARC/PF&U was initiated in 2003.ExplorationEarly exploration led to the discovery ofNi-Cu sulphides hosted in a komatiitic setting.A lens of massive sulphide (440 m 2 )was found in partly serpentinised ultramaficrocks hosted in gossanous supracrustals onthe south coast of the Ammassalik Island.Systematic surface sampling of the lenseshowed an average of 0.98 % nickel,0.33 % copper, 553 ppm cobalt and 510ppb combined Au-PGE.The Ammassalik occurrence displaysProterozoic komatiite-related Ni-Cu deposits.The komatiitic host rock has a high magnesiumcontent ranging from 25 to 30 wt.%.Diamond drilling at three localities in 2005outlined a new sulphide occurrence withup to 1.5% nickel.Amitsoq:Amitsoq-Nanortalik peridotite intrusions.Four PGE-bearing ultramafic hornblendeperidotite intrusions have been recordedon Nanortalik peninsula and the island ofAmitsoq in South Greenland. The intrusionswere investigated in 1987 by PlatinovaResources Ltd. and Boulder Gold N.L.Exploration ceased after a few years dueto modest PGE contents. The ultramaficplugs in the Nanortalik region may be relatedto an appinite suite observed throughoutthe Ketilidian orogen across the southerntip of Greenland.7

THE PGE POTENTIAL IN GREENLANDGEOLOGY AND ORE 8 / 2007Rusty layer of iron basalt at the Asuk beach on the northern coast of Disko, central West Greenland.Photo: A.K.Pedersen.Two small plugs of layered ultramaficsoccur on the south shore of Søndre Sermilik.• A hornblende peridotite body is exposedfive km south of the Ippatit valley.It hosts the “Waldorf” PGE showing.The peridotite body is exposed > 200metres along the shore and 350 metresinland. Small exposures of peridotiteindicate that the body is >2.5 km across.The peridotite contains about 1 vol.%disseminated sulphides. Grab samplesshowed up to 280 ppb platinum and330 ppb palladium, and drill-core samplesyielded up to 100 ppb Pt and only40 ppb Pd.• A hornblendite-peridotite intrusionoccurs on central Amitsoq. It has beenobserved over a length of 1.5 km, andfrom the shore and inland to 335 ma.s.l. It is an E-W striking dyke-like bodythat pinches and swells in three dimensions.Widths vary between 90 and250 metres. The sulphide content isabout 0.2 vol. % , but reaches 15% in10-20 cm wide zones. Pyrrhotite, pentlandite,chalcopyrite, and cubanite dominatethe sulphides, accompanied by 5-10 vol. % magnetite. Traces of gold,platinum, and palladium were reportedfrom the showing in 1970.Palaeogene settings(West and East coast)Disko Island:Flood basalt related Palaeogene Ni-sulphideoccurrences with PGE (Noril´sk type).For more than a century the PalaeogeneWest Greenland Basalt province has seenexploration for Ni-sulphides and PGE. Theknown occurrences in the Disko Bugt regionare mainly hosted in contaminated lavas,and in dykes at the base of the volcanicsuccession. The province is believed to havea significant potential for PGE-Ni-mineralisation.Palaeogene picrite and basalt lavas overliethick Upper Cretaceous and Palaeogenesediments. Most of the voluminous onshorevolcanics were deposited in a shortperiod of time 61–59 Ma ago. The Palaeogenedyke intrusions, such as the HammerDal complex on northwest Disko, containnickel-bearing pyrrhotite and native ironformed by processes akin to Noril´sk typeNi-Cu-PGE deposits. The analogy to Noril´skhas attracted exploration, e.g. by Falconbridgeand Vismand. The Hammer Dalcomplex on Disko belongs to a swarm ofmineralised dykes fed by contaminatedmagma and the complex has a number ofattractive characteristics. It is the richestmetallic iron deposit in the region and itrelates spatially to the most intense hydrothermalalteration field on Disko. A fieldthat may imply the existence of a large intrusionat depth. Ground geophysics haverevealed a large conductor at 400–500 mbelow the present surface. The conductercould represent a volcanic body with sulphidesand metallic iron.Basalt chunk with accumulation of metallic iron, Disko Island, central West Greenland.Photo: A.K.Pedersen.Exploration and evaluationof potential resourcesThe prospective area on north-west Disko(Hammer Dal) is defined by a swarm ofNW-SE to N-S striking dykes and subvolcanicintrusions of basaltic melt. The dykeswere probably feeders to large volumes ofcontaminated lavas. The intrusions hostdeposits of metallic iron and sulphides, allof which at the moment are too small tobe economically viable. "Branched iron8

THE PGE POTENTIAL IN GREENLAND500 m high mountain slope of iron-rich basalt layers in the southern partof Disko Island, central West Greenland. Photo: A.K.Pedersen.bodies" dominate the ore cumulates depositedalong the steep (70º) contacts bya mechanism that is not completely understood.The presence of iron cumulates suggestsconsiderable magma transport capabilityin the magma. The amount of depositediron typically reflects local conditions ofdeposition rather than the general potentialof the intrusive system. Apart fromnative (metallic) iron (and alloys), pyrrhotiteand pentlandite are common. Sulphideenrichedbasalt (together with accumulated,metallic iron) shows > 1% Ni and elevatedPGE contents, up to 0.5 ppm. Afinal evaluation of the PGE potential inthis setting is not possible at present.Exploration was carried out in the areain the 1980s by Greenex/Cominco Ltd. APlatinova A/S-Falconbridge Greenland A/Sjoint venture conducted an extensive pro-9

GEMSTONES OF GREENLANDcontacts between mafic intrusive units andbasement or other intrusive units.Back scatter images of selected Skaergaard minerals. c–d: skaergaardite (PdCu) in a sulphide droplet;e–f: free intergrowths of various noble metals minerals.The Skaergaard intrusionThe intrusion was emplaced during thebuild up of the regional flood basalts andthe initial stages of continental rifting andseafloor spreading in the North Atlantic.The intrusion is currently modelled as a boxlikemagma chamber c. 11 by 7.5 km insurface area with an original stratigraphyof c. 3.8 km.The magma solidified in concentriczones toward the centre of the intrusion.Phase layering, i.e., liquidus parageneses,and cryptic variation in liquidus mineralsallow a subdivision of the intrusion. Thecryptic variation in minerals is significant.Olivine evolves from c. Fo70 to Fo1, andplagioclase from c. An70 to An10.Thedeepest gabbros in the Layered Series (LS)are not exposed and are referred to as theHidden Zone (HZ). The exposed rocks ofLS are divided in Lower Zone (LZ), MiddleZone (MZ), and Upper Zone (UZ).The mineralisation is hosted in theTriple Group in the upper part of the MZafter the crystallisation of c. 70 % of theparental ferrobasalt magma. The TripleGroup is the name of a c. 100 m thickstratigraphy characterised by three, distinct,leucogabbro layers. The mineralisation iscomposed of five main levels and in totalten well-defined levels of enrichment inPGE (Pd-levels). The stratigraphic separationbetween main Pd-levels is c. 10 metres.All Pd-levels are perfectly parallel to thewell-developed saucer-shaped magmaticlayering in the host gabbros.The number of developed Pd-levels decreasessystematically toward the marginsof the intrusion, where only one Pd-level(Pd5) is developed. Au is always concentratedin or just above the top of the locallydeveloped Pd-levels irrespective of thenumber of developed Pd-levels. The stratigraphicseparation between the base ofPd5 level and the top of the Au-rich zonesincreases from c. 5 metres at the marginto c. 60 metres in the centre of the mineralistion.The mineralisation has a low suphidecontent (

GEOLOGY AND ORE 8 / 2007Bureau of Minerals and Petroleum(BMP)Government of GreenlandP.O. Box 930DK-3900 NuukGreenlandTel: (+299) 34 68 00Fax.: (+299) 32 43 02E-mail: bmp@gh.glInternet: www.bmp.glGEOLOGY AND ORE 7 / 2007Layered sequences in the Upper Zone of the Skaergaard Intrusion, southern East Greenland.Photo: GEUS.Key referencesGeological Survey of Denmarkand Greenland (GEUS)Øster Voldgade 10DK-1350 Copenhagen KDenmarkAppel, P. W. U. 1993: Gold and platinum-groupelement anomalies in the Fiskenæsset stratiformanorthosite complex, West Greenland. GeologicalSurvey of Greenland. Open File Series. 93/6, 24 pp.Harpøth, O., Pedersen, J. L., Schønwandt, H.K.& Thomassen, B. 1986: The mineral occurrencesof central East Greenland. Meddelelser om Grønland,Geoscience 17, 1–139.Lightfoot, P. C. and C. J. Hawkesworth 1997:Flood basalts and magmatic Ni, Cu, and PGE sulphidemineralization: Comparative geochemistryof the Noril'sk (Siberian Traps) and West Greenlandsequences. In: Large igneous provinces: continental,oceanic, and planetary flood volcanism.J. J. Mahoney and M. F. Coffin (eds). AmericanGeophysical Union, Geophysical MonographSeries, 100, 357–380.Myers, J. S., 1985: Stratigraphy and structure ofthe Fiskenæsset Complex, southern West Greenland.Grønlands Geologiske Undersøgelse Bulletin150, 72pp.Nielsen T.F.D. 2004: The shape and volume ofthe Skaergaard intrusion: implications for massbalances and bulk composition. Journal ofPetrology 45, 507–530.Nielsen, T.F.D. & Bernstein, S. 2004: Maturationof areas in the Tertiary of East Greenland for PGE-Ni-Cu exploration. Danmarks og GrønlandsGeologiske Undersøgelse Rapport 2004/6, 59pp. (CD-ROM included).Nielsen, T.F.D., Andersen, J.C.Ø. & Brooks, C.K.2005: The Platinova Reef of the Skaergaardintrusion. Mineralogical Association of CanadaShort Course 35, 431–455.Page, N. J., Myers, J. S., Haffty, J., Simon, F. O.& Aruscavage, H. R. 1980: Platinum, paladiumand rhodium in the Fiskenæsset Complex, SouthwesternGreenland. Economic Geology. 75,907–915.Schönwandt, H. K. 1971: Mineralised ultramaficrocks in South Greenland. Rapport GrønlandsGeologiske Undersøgelse, 35: 30–31.Schönwandt, H. K. 1972: Geological and geophysicalwork on ultramafic rocks in the Nanortalikarea, South Greenland. Rapport GrønlandsGeologiske Undersøgelse, 45, 35–36.Secher, K.1982: Noritic rocks and associated nickelcopper-sulphideoccurrences in Sukkertoppendistrict, central West Greenland, GGU Rapport115, 30–34.Secher, K. 2001: The Pd + Pt dispersion in noriticand undifferentiated mafic rocks of the Archaeancraton east of Maniitsoq, southern West Greenland,Danmarks og Grønlands Geologiske UndersøgelseRapport 2001/123, 22 pp.Steenfelt, A. 2001: Geochemical atlas ofGreenland – West and South Greenland, Danmarksog Grønlands Geologiske UndersøgelseRapport 2001/46, 40 pp. (CD-ROM included).Stendal, H. (ed.) 2000: Exploration in Greenland:discoveries of the 1990s. Transactions of theInstitution of Mining and Metallurgy, section B,Applied Earth Science 109, B1–B66.Ulff-Møller, F.1991: Magmatic platinum-nickeloccurrences in the Tertiary West Greenland BasaltProvince: prospecting by Greenex A/S in 1985-1988." Open File Series Grønlands GeologiskeUndersøgelse, 91/1. 37pp.Tel: (+45) 38 14 20 00Fax.: (+45) 38 14 20 50E-mail: geus@geus.dkInternet: www.geus.dkFront cover photographLayered dunite from the region ofFiskevandet, southern West Greenland.Photo: NunaMinerals A/S.AuthorK. Secher, P. Appel and T.F.D. NielsenEditorKarsten Secher, GEUSGraphic ProductionCarsten E. Thuesen, GEUSPhotographsGEUS unless otherwise statedPrintedFebruary 2007 © GEUSPrintersSchultz Grafisk12ISSN1602-818x