Assessment of orogenic gold mineralisation inGreenland

No. 26 - February 2015

GO-26_GO-26 19/02/15 15.14 Side 1

An orogenic gold deposit has beenmined at Nalunaq (South Greenland)from 2004 to 2013 when the operationwas closed. A total of 10.65 tons(375,670 oz) of gold was produced dur-ing that period. In order to assess thepotential for undiscovered orogenicgold deposits in Greenland, a work-shop in Copenhagen (November 2014)investigated geological, geochemicaland geophysical data. The main conclu-sion was that areas of South Greenlandin relative proximity to the closedNalunaq gold mine and the Archaeanterranes of southern West and South-West Greenland have the highestpotential for finding new orogenic golddeposits. The highlights from thisworkshop are presented here.

Introduction

Gold (Au) was probably the first metalknown by mankind and has been exten-sively used and mined in the last 5,000years. Gold is still the most importantcommodity in the mineral explorationindustry, and approximately one third ofthe worldwide exploration investment isused to find gold deposits. Approximatelyhalf of the gold is used in jewellery andapproximately one third is used as safeinvestment as many of the National Banksmust hold a gold reserve. Only approxi-mately 12% of the produced gold goesinto industrial applications such as elec-tronics, medicine and space craft.

The biggest current gold producers areChina, Australia, USA, Russia and SouthAfrica. Although gold is enriched in theEarth’s crust by different mechanismsforming different deposit types, orogenicgold deposits constitute 40% of theworld’s gold resources.

In November 2014, a workshop on the‘assessment of the orogenic gold potentialin Greenland’ was arranged by theGeological Survey of Denmark andGreenland (GEUS) and the Ministry ofMineral Resources (MMR) - formerly

Ministry of Industry and Mineral Resourcesto stimulate new gold exploration cam-paigns in Greenland. The purpose for theworkshop was to assess the potential ofundiscovered orogenic gold deposits inthe upper 1 km of the Earth’s crust and torank the most prospective areas. Themethods for the assessment and rankingof the individual tracts were designed tocomply with the ‘Global Mineral ResourceAssessment Project’ procedures defined bythe US Geological Survey (USGS).

This edition of Geology and Ore highlightsthe main results from the workshop,including descriptions of the most impor-tant orogenic gold provinces in Greenland.A recent geological review of orogenicgold provinces in southern West andSouth-West Greenland is given in Kolb etal. (2013), and a review on gold occur-rences in South Greenland can be found in

Stendal & Frei (2000). Other Geology andOre volumes covering the description oforogenic gold mineralisation are nos. 1, 9 and 11. A comprehensive GEUS reportdocumenting all results from the workshopwill be available during 2015.

Methodology

The evaluation of the potential for undis-covered orogenic gold deposits was carriedout according to the standardised processutilised in the Global Mineral ResourceAssessment Project. In this process, anexpert assessment panel uses all availableknowledge and data for a specific region(tract) to assess the possibility of findingundiscovered deposits within this tract to adepth of 1 km (Fig. 1). The assessmentpanel consisted of sixteen geologists fromthe USGS, the Geological Survey of Finland(GTK), GEUS, MMR and private exploration

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5 Assessment of orogenic goldmineralisation in Greenland

512

4 613

7

3+10 11281

1524

2725

28

32

33b

33a

22

30 + 31

19

16c

1817

9

23

14

20

16a

16b

37

26Nuuk

Tasiilaq

Nanortalik

IlloqqortoormiutUummanaq

Figure 1. The tracts assessed for orogenic golddeposits during the November 2014 workshop.

GO-26_GO-26 19/02/15 15.14 Side 2

and consulting companies; each with spe-cific knowledge on relevant aspects of theGreenland geology or expertise in orogenicgold deposits. After geological presenta-tion and discussion, the members of theassessment panel made their individualestimates (bids) of the number of undis-covered deposits they believed could befound under the best circumstances in atract. A final discussion in the panel result-ed in a consensus bid that was used asinput to statistical simulation. Based on thegrade-tonnage model for Proterozoic andArchaean orogenic gold deposits fromFinland, Sweden and Australia recentlycompiled by GTK for their own assess-ment, this simulation provides a predictionon how much undiscovered gold ore canbe expected in a specific tract.

Orogenic gold mineralisation

Orogenic gold deposits, also referred to aslode-gold, quartz vein-hosted gold andgold-only deposits, are hydrothermaldeposits formed during focussed fluidflow in an orogen during metamorphismand deformation (Fig. 2; Goldfarb et al.2005; Groves et al. 1998). Regionalreviews of orogenic gold deposits haveshown that the majority formed at 1–3kbar and 250–400°C in greenschist to

lower amphibolite facies, but lower andespecially higher temperature counterpartshave also been recognised. These golddeposits are collectively characterised bytheir common structural control, and simi-lar hydrothermal alteration (Si, K, Rb, Ba,Li, Cs, Tl, S, H2O, CO2 enrichment) andmetal (Au-Ag ± As, Sb, Te, W, Mo, Bi)association (Table 1). The gold is hosted inquartz-vein systems, hydrothermal alter-ation zones and altered mylonites inshear- and fault-zone systems.

The genetic concept is the crustal continu-um model that describes orogenic golddeposits, which formed at different P–Tconditions equivalent to lower greenschistto lower granulite facies levels over aninterval of 20–25 km in the middle toupper crust (Fig. 2; Goldfarb et al. 2005;Groves et al. 1998). It proposes the syn-metamorphic upward migration of aurifer-ous fluids from deep-seated sources alongstructural conduits such as shear and faultzones. Differences in P–T conditions oforogenic gold formation have been usedto subdivide the deposits into epizonal(150–300°C, 0.5–1.5 kbar), mesozonal(300–475°C, 1.5–3 kbar), and hypozonal(475–700°C, 3–6 kbar). Phanerozoic oro-genic gold deposits formed in accretionaryorogens such as the North American

Cordillera in fore-arc to back-arc settings.Although other genetic models are alsodiscussed in academia, this does not affectthe key parameters of the gold mineralsystem (Table 1). The critical and impor-tant factors of the orogenic gold mineralsystem are an active pathway forhydrothermal fluids, the fluid throttle andthe site of gold deposition. In geologicalterms these are: (1) long-lived, polyphaseshear and fault zones at continental mar-gins that transect the lithosphere; (2) com-plex, smaller-scale deformation zones thatare spatially associated with permeabilitybarriers and rocks of contrasting compe-tency; and (3) heterogeneous host rockswith a large chemical gradient or chemi-cally reactive rocks that would be in dise-quilibrium with the ore fluid.

The largest orogenic gold deposits are theGolden Mile deposit in Western Australiawith 1,800 tons Au and the Hollinger-McIntyre deposit in Ontario, Canada with987 tons Au (Table 1). The tonnage oforogenic gold deposits varies largelybetween a few thousand tonnes to morethan several hundred million tonnes of ore(Fig. 3). Historically, the average grade oforogenic gold deposits has been c. 5–15g/t (equiv. to ppm) Au until the start ofthe new century. Since then cut-off

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A S S E S S M E N T O F O R O G E N I C G O L D M I N E R A L I S A T I O N I N G R E E N L A N D

Sub-greenschist

L. Greenschist

U. Greenschist

Amphibolite

Granulite

Du

ctile

-bri

ttle

tra

nsi

tio

n

Porphyry- lamprophyre dyke swarms

PegmatiteMetamorphic

Pb, Sr, Au?

Magmatic Pb, Sr, Au?

Mantle/lower crust Pb, Sr, Au?

Westonia,

Renco,

Griffins Find,

Big Bell

Lupin, Hutti,

Marvel Loch

Wiluna

Hollinger-McIntyre,

Golden Mile, Hutti

Meteoric

Metamorphic

Mantle

Magmatic

Lamprophyric

Orogenic gold-quartz veinsHypotheses for fluid sources

10 km

10 k

m

Groves et al. 1998 Pettke et al. 2000

+ ++

++ +

++++

dykes

Figure 2. Left: Schematic sketch of the crustal continuum model for orogenic gold deposits, illustrating a crustal-scale shear zone focussing auriferousfluids from different sources. Major examples of the typical orogenic gold deposits are given. Right: Sketch of possible fluid migration paths in an oro-genic setting. Gold mineralisation occurs in shear zones and folded metamorphosed wall rocks, often in higher order structures close to the main terraneboundary.

GO-26_GO-26 19/02/15 15.14 Side 3

grades decreased due to increasing goldprices and currently even deposits withless than 1 g/t Au on average are minedin places. Orogenic gold deposits are gold-only deposits producing generally noother commodity. The lower-grade exam-ples are mined in open pit operations,whereas the often high-grade nature ofthis type of deposit makes them a primarytarget for underground operations, andalso a target for artisanal mining in manydeveloping countries. The Nalunaq depositin South Greenland has been mined from2004–2013 and 10.65 tons Au from c.714,000 tons of ore at a grade of 15 g/tAu have been produced, which is averagein tonnage but slightly higher in goldgrade when compared with orogenic golddeposits worldwide (Fig. 3).

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1

10

Au

(g

/t)

Tonnage (Mt)

0.01 0.1 1 10 100

GlobalFennoscandia

Nalunaq

Figure 3. Diagram plotting oregrade (Au in g/t) against theproven amount of ore (tonnage inmillion tons (Mt)) of the Nalunaqgold deposit and selected orogenicgold deposits from Scandinavia(Fennoscandia) and elsewhere(global). These data were used inthe model for the statistical calcu-lations. Courtesy of GTK. TheNalunaq gold deposit has compa-rable tonnage to the deposits inthe model, suggesting that themodel is able to correctly charac-terise Greenlandic deposits.

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A few thousand tonnes to > 100 Mt

5 to 15 g/t, lower in recent open pit or large-scale operations

Nalunaq: 714,000 t at 15 g/t Au

Golden Mile: 119 Mt at 10.7 g/t AuHollinger-McIntyre: 101 Mt at 9.9 g/t AuBarberton: 27 Mt at 10.7 g/tHomestake: 148 Mt at 10.7 g/tFäboliden: 90 Mt at 1 g/t

Economic and geological characteristics of orogenic gold deposits

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Economic characteristics

Typical size

Typical grade

Greenland

International

Geological characteristics

Tectonic context

Age

Structure

Metamorphism

Lithology

Alteration

Geochemistry

Metal association

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Assessment criteria

Orogenic setting

Terrane age was used where data was available

Major shear zone (if data available)

Greenschist facies and amphibolite facies, also retrograde from granulite facies

Chemically reactive rocks and heterogeneous sequences as additional positive argument

Alteration halo as additional positive argument (if data available)

Not used

Anomalies in stream sediment and whole- rock data (where available)

Accretionary orogen, Archaean granite-greenstone belts

Neoarchaean (2.74–2.54 Ga), Palaeoproterozoic (2.1–2.0 and 1.91–1.77 Ga), Neoproterozoic (700–600 Ma), Silurian to Carboniferous (430–300 Ma), and Cretaceous to early Palaeogene (120–50 Ma)

Terrane boundary, major crustal-scale shear zone

Mainly greenschist facies and lower amphibolite facies

Metamorphic, often chemically reactive and heterogeneous metamorphic rocks

Mainly localised tens of metres-scale halo around auriferous zones, including carbonates, sulphides, micas and amphiboles

Si, K, Rb, Ba, Li, Cs, Tl, S, H2O, CO2 enrichment

Au-Ag ± As, Sb, Te, W, Mo, Bi

Table 1. Main characteristics and assessment criteria for orogenic gold deposits.

GO-26_GO-26 19/02/15 15.14 Side 4

Undiscovered orogenic gold deposits

A total of 28 tracts have been assessed forundiscovered orogenic gold deposits. Theyhave been defined on the 1:500 000 scalegeological map of Greenland, based ongeological knowledge, geochemicalanomalies and known gold occurrences(Figs 1 and 4). Only tracts that fulfil atleast one of the critical assessment criteriafor orogenic gold have been chosen (Table1) and extracted as geo-referenced poly-gons. The consensus bids on the numberof undiscovered orogenic gold depositsare summarised in Table 2. The 28 tractscover an area of 254,324 km2 in total.

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Stream sedimentAu ppb

50 - 120

> 120

20 - 50

HMCAu ppb

200 - 1000

> 1000

50 - 200

Rock samplesAu ppb

600 - 1000

> 1000

200 - 600

250 km

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Consensus bid on the number of undiscovered orogenic gold deposits

at different confidence levels

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1200400001000112020000004000

2510620002002234141000017201

4722

103021402

1038825222223

11623

3511620102016255141111128312

3.65.70.80.43.52.30.70.10.10.50.20.10.30.20.10.70.11.60.20.31.40.90.10.31.60.10.10.1

Summarystatistics

N05 N01N10N50N90Depositdensity

Number ofunknowndeposits

Tract Area(km2)

Tract name

Mean estimate of undiscoveredorogenic gold(metric tons)

71143

164152614

205

161248543236

201135

101365

235373836

501036206

10765469

331557

44872214

11032

315

741

215964091922367241313121429

150551228

702866

1,5431,9612,078

787205

12,2774,3674,402

6357,967

19,29714,98565,9217,7158,7282,3445,7333,238

543751

5,1915,2065,211

29,44025,33816,892

12

3+104567

8+9+15+26+2711121314

16a16b16c

17+1819202223242528

30+3132

33a33b37

N90, N50, N10, N05, N01 = Confidence levels; a measure of how reliable a statistical result is, expressed as a percentage that indicates the probability of the result being correct. A confidence level of 10% (N10) means that there is a probability of 10% that the result is reliable. Deposit density = The total number of deposits per 1000 km2.

•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

Table 2. Summary of consensus bids from theNovember 2014 assessment workshop.

Figure 4. Geochemical gold anomalies in various sample sets from localities in Greenland. The most prospective areas for orogenic gold deposits are rep-resented in southwestern and southern Greenland. Anomalies in northwestern and eastern Greenland are related to other types of gold deposits. Left:Stream sediment samples with Au > 20 ppb. Centre: Heavy mineral concentrates (HMC) with Au > 50 ppb collected by GEUS, Nordisk Mineselskab A/Sand NunaMinerals A/S. Right: Rock samples collected by GEUS and Nordisk Mineselskab A/S with Au > 200 ppb.

GO-26_GO-26 19/02/15 15.14 Side 5

Tartoq gold province

The Tartoq gold province (Tract 2) inSouth-West Greenland was ranked as thearea with the highest prospectivity fororogenic gold deposits in Greenland interms of tract size (Table 2). This wasbased on the number of known orogenicgold occurrences and prospects, and thefavourable geology including a majorgreenschist facies shear-zone system in anArchaean orogenic setting (Kolb 2011,Kolb et al. 2013). Reasonably sizedArchaean greenstone belts host two oro-genic gold prospects with widespreadchlorite-ankerite-pyrite alteration (Fig. 5), a typical feature observed in giant oro-genic gold provinces elsewhere (e.g.Golden Mile and Hollinger-McIntyre).Mineral exploration in the late 1980s andearly 1990s focussed on the Nuuluk andIterlak occurrences, however using a vol-canic-hosted massive sulphide mineralisa-tion model. The drilling campaign was notable to identify larger sulphide orebodiesand was therefore stopped. Hence, thefull potential for orogenic-style gold min-eralsation remains untested.

• Nuuluk: Gold is hosted in quartz-ankerite veins in four 0.5 m wide, paral-lel tabular zones. These zones form a350 to 400 m wide and 4 to 5 km longNNE-trending, moderately WNW-dip-ping hydrothermally altered zone. Thequartz-ankerite veins contain as much as 50 ppm Au in grab and drill-coresamples. The host rocks are mainlymagnetite- and graphite schist with atypical mesozonal alteration zone ofankerite, chlorite, quartz, pyrite,arsenopyrite, pyrrhotite, chalcopyrite,tennantite and gold. Locally, ultramaficrocks contain talc, serpentine, fuchsite,dolomite as hydrothermal alterationassemblage.

• Iterlak: Banded quartz-pyrite rockshost the gold mineralisation up to >5ppm at Iterlak, which was initiallyinterpreted as syngenetic exhalativesulphide mineralisation. The sulphidesand gold, however, replaced mag-

netite-grunerite-quartz banded ironformation in two NNE-trending,approx. 100 m wide and 200 to 400m long zones. Hydrothermal alterationin the wall rocks is muscovite, quartz,ankerite, pyrite and chlorite. Talc-car-bonate schist has a talc-ankerite-chlo-rite-pyrite alteration assemblage.

• Amitsuarsua: Amitsuarsua is a rela-tively large (c. 12 km long and up to 4 km wide) greenstone belt, which isonly poorly investigated. Gold minerali-

sation of as much as 1 ppm is hostedin zones of carbonate alteration, silifi-cation and sulphidation.

• Other areas: In the Tartoq goldprovince, there are also smaller areasof greenstone that show hydrothermalalteration for several hundred metresalong strike, surrounding foliation-par-allel laminated quartz veins. They areonly poorly investigated, but have thepotential to host gold mineralisation.

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48°W

61°45'N

61°30'N

61°25'N61°25´N

61°30´N

48°30´W49°W

48°W

Iterlak

BikubenNuuluk

Amitsuarsua

Naalagaaffik

Sermilig

aarsuk

Nuna Qaqortoq

Serm

iligaa

rsuk B

ræ

Midternæs

Akuliaruseq

5 km

61°35´N

61°45´N

Greenland

Thrust faults Fault

Proterozoic

Granite, undifferentiatedSupracrustal rocks

Gold occurrence

Archaean

Felsic schistTartoq Group supracrustal rocks

Chloritised breccia zoneSerpentinite

Orthogneiss, undifferentiatedPegmatite, undifferentiated

Quaternary coverIce

Figure 5. Right: Iron-stained min-eralisation at Nuuluk. The rusty redcolouration stems from weatheringof pyrite in the auriferoushydrothermal alteration zones. The strong lamination of the hostrock is a result of deformation in ashear zone associated with goldmineralisation.

Figure 5. Top: Geological map ofthe Tartoq gold province showingthe Nuuluk and Iterlak prospectsand other gold occurrences in thegreenstone belts. Left: Finely lami-nated banded iron formation atIterlak with grey iron-oxide andwhite quartz-rich layers. This is thehost rock of orogenic gold miner-alisation at Iterlak.

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Paamiut gold province

The Paamiut gold province (Tract 1) inSouth-West Greenland was ranked as thearea with the second highest prospectivityfor orogenic gold deposits in terms oftract size (Table 2). The Paamiut goldprovince is characterised by amphibolitefacies greenstones, major retrograde shearzones in the lower amphibolite facies andabundant late-tectonic granites in anArchaean orogenic setting (Kolb 2011,Kolb et al. 2013). The area has attractedonly limited exploration, although streamsediment samples record a pronouncedgold anomaly. Four gold prospects havebeen identified during field work andexploration (Fig. 6).

• Akuliaq: Limited exploration has beencarried out on the Akuliaq peninsula,identifying up to 12 ppm Au inhydrothermal alteration zones and upto 4 ppm in quartz veins. Auriferousquartz veins form lenses in foliation-parallel, NE-trending, 2–4 km longshear zones. They are generally 2–20cm wide, although a few reach 20 min width. Amphibolite is the primaryhost rock and developed a quartz,hornblende or orthoamphibole, biotite,tourmaline, pyrrhotite, arsenopyriteand, locally, garnet, and muscovitealteration assemblage that is character-istic for the transition between meso-zonal and hypozonal conditions.

• Mellembygden: Laminated quartzvein sets with 10–20 m spacing and 30 to 50 cm thickness can be followedover 3–5 km along strike. The shearzones are developed at the contactbetween amphibolite and orthogneiss.One grab sample returned as much as2.6 ppm Au. No systematic explorationhas been carried out to map the extentof the mineralisation. Hydrothermalalteration assemblages contain epidote,tourmaline, carbonate, titanite, pyriteand chalcopyrite in addition to horn-blende, biotite, muscovite, quartz, andthe sulphides in orthogneiss.

• Nigerlikasik: At Nigerlikasik, quartzveins range in thickness from a fewmillimetres to as much as 3 m for 30 malong strike. Although analyses of grabsamples only returned gold values inthe higher ppb-range, quartz veins andhydrothermal alteration assemblagesare similar to the auriferous structureson Akuliaq. No exploration programmehas been designed to identify a possi-ble gold mineralisation.

• Akulleq: At Akulleq, hydrothermalquartz veins are common, but they are

cut by later structures and have beenmetamorphosed. The mineral assem-blage in quartz vein halos is quartz,plagioclase, clinopyroxene, garnet,chalcopyrite, arsenopyrite andpyrrhotite, indicating the higher meta-morphic conditions reaching granulitefacies in the wall rocks. Quartz in theveins is recrystallised and gold mayhave been remobilised. This area is sci-entifically interesting, but may not bethe best exploration target, due tometamorphic and tectonic overprint.

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Figure 6. Top: Geological map of the Paamiut gold province showing the basic geology and goldoccurrences. Bottom: Geologist working on a section across an auriferous structure in Mellembygden.

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South Greenland gold province

The Nalunaq gold deposit that was minedfrom 2004–2013 is located in this goldprovince north of the Nanortalik settle-ment. Tract 5 covers an area around theclosed mine, which is known for severalgold occurrences and has attracted mineralexploration in the last years (Figs 1 and 7).Gold and arsenic (As) anomalies in streamsediment samples are widespread (Fig. 4).Tract 6 encompasses the eastern extensionof tract 5 and is also known for Au and Asanomalies, and several gold occurrencesand prospects (Figs. 1, 4 and 7; Stendal &Frei 2000). Both tracts are located in thePalaeoproterozoic Ketilidian orogen at thecontact of an arc batholith-like granite-gneiss terrane (Julianehåb batholith) to thenorth, and a possible fore-arc terrane ofaccreted meta-sedimentary and meta-vol-canic rocks to the south. Although nomajor structure was mapped along thiscontact and geophysical methods do notshow a significant anomaly, the gold occur-rences cluster around this contact. In thesame geological setting, the Phanerozoicorogenic gold deposits of the circum-Pacificrim are located (Goldfarb et al. 1998).Based on the favourable geological settingand timing, the gold anomalies and knownoccurrences, both tracts were rated veryprospective for orogenic gold mineralisation.

• Nalunaq gold deposit: Gold minerali-sation is hosted in laminated quartzveins in a reactivated reverse shearzone. Several different descriptions ofthe hydrothermal alteration assemblageexist in the literature about a calc-sili-cate (clinopyroxene-garnet-plagioclase)alteration in the host rock amphibolite(Bell & Kolb 2013; Kaltoft et al. 2000;Stendal & Frei 2000). Recent investiga-tions proved that this calc-silicate orskarn alteration formed pre-mineralisa-tion and was overprinted by the aurifer-ous quartz veins (Fig. 7). The hydrother-mal alteration assemblage consists ofbiotite, quartz, rutile, arsenopyrite, tour-maline, gold, löllingite, Bi-sulphosalts,scheelite and maldonite. The currentidea is that the orogenic gold minerali-

sation overprinted earlier skarn alter-ation in the middle amphibolite faciesand formed at c. 1790 Ma duringPalaeoproterozoic orogeny.

• Vagar gold prospect (Niaqornaarsuk):The Vagar prospect on theNiaqornaarsuk peninsula consists of

approx. 20 gold occurrences, each withgold-contents in the ppm range. Theoccurrences cluster around a NE-trendingdextral shear zone (Stendal & Frei 2000).The best target to date (AmphiboliteRidge, Fig. 8) is characterised by 1-4 mwide auriferous quartz vein sets with aminimum strike and down-dip continuity

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Inland Ice, local ice caps and glaciers

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Metapelites and granites (Pelite Zone)

Metapsammites to -pelites and metavolcanic rocks (Psammite Zone)

Julianehåb Batholith and related intrusions

Rapakivi granite suite and related intrusions

Gold occurrence

100 km

Figure 7. Top: Geological map of the SouthGreenland gold province showing the Nalunaqgold deposit and the other prospects. Centre:Underground photograph from the Nalunaq goldmine showing the auriferous quartz vein crosscut-ting the greenish calc-silicate or skarn alteration.The quartz vein is approx. 40 cm wide. Bottom:Large (1–2 mm) visible gold grains in quartz ofthe auriferous quartz vein. Gold is closely associ-ated with the dark minerals due to reactionbetween the hydrothermal fluid and the minerals(clinopyroxene).

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of 600 m and 300 m, respectively. Grab,channel and diamond core samplesreturn very high gold grades (nunaminer-als.com). Auriferous quartz veins andalteration zones are hosted in amphibo-lite and granodiorite to granite gneiss.The hydrothermal alteration assemblageis K-feldspar, quartz, muscovite, chlorite,titanite, calcite, pyrite, chalcopyrite, Bi-tel-lurides, Bi-sulphosalts, gold and bismuth.

• Hugin gold prospect (Kangerluluk,Sorte Nunatak): A larger, c. 20 m wideshear-zone system is mineralised withgold and copper in quartz veins, and theoccurrences at Kangerluluk and SorteNunatak are probably connected via thisshear zone (nunaminerals.com; Stendal& Frei 2000). The auriferous quartz veinshave a quartz, biotite, chlorite, chalcopy-rite, pyrrhotite, gold, bornite, chalcocitealteration halo. Grab samples contain asmuch as 120 ppm Au and 4 wt% Cu.Channel samples returned 3.1 metres at9.3 ppm Au. The high copper gradesoriginate from copper sulphides that

occur as lenses in the shear zone. This isexplained by an orogenic gold overprintof a previous volcanic-hosted massivesulphide mineralisation in the metamor-phosed basaltic host rock.

Ataa gold province

The Ataa gold province (Tract 20) is situat-ed north and east of Ataa in the north-eastern Disko Bay area (Fig. 1). TwoArchaean greenstone belts, the amphibo-lite facies Saqqaq–Itilliarsuk and the green-schist facies Ataa–Eqi belts, are separatedby the Torsukattak shear zone and hostthree orogenic gold occurrences (Fig. 9;Garde et al. 1999; Stendal et al. 1999).

Based on criteria such as Archaean age,metamorphic grade, gold occurrences andgeochemical anomalies, this area wasranked as one of the most prospective fororogenic gold deposits in Greenland.However, the area was overprinted byPalaeoproterozoic orogeny that possiblydeformed and remobilised the Archaeanmineralisation.

• Saqqaq: Gold mineralisation is hosted inthe strongly silicified Saqqaq shear zone,separating serpentinite and laminatedamphibolite from overlying garnet-micaschist. The mineralisation is tabular, 2–5m wide and c. 1200 m long. Gold gradesare 1.8–4.2 ppm Au and on average 1ppm over 2.5 m. Higher-grade zonesoccur in the shear zone along strike withas much as 11.4 ppm Au over 2.2 m.

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Figure 9. Geological map of the Ataa gold province.

Figure 8. Panorama view of the Amphibolite Ridge, part of the Vagar gold prospect. (looking duesouth). Quartz-veins are outcropping on the left (east) side of the ridge in the saddle (centre ofimage). Potassic-feldspar altered granitoids are seen in the foreground (Copyright SRK 2012).

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Hydrothermal alteration is quartz, gar-net, fuchsite, biotite, chlorite, actinolite,titanite, tourmaline, pyrrhotite,arsenopyrite, gold, niccolite, wolframiteand scheelite.

• Itilliarsuk: Near-vertical shear zoneshost discontinuous auriferous quartzveins in various host rocks ranging frombanded iron formation and amphiboliteto biotite schist. Six auriferous zoneswith maximum strike length of 500 mcontain as much as 15.1 ppm Au over2.8 m in channel samples.

• Eqi: Gold mineralisation occurs at thecontact between metamorphosed basalt,komatiite and felsic volcanic rocks. Thecontact is characterised by a 100–200 mwide hydrothermal alteration zone con-sisting of ankerite, chlorite, fuchsite,tourmaline and pyrite as a typical meso-zonal alteration assemblage. Centimetre-wide quartz veins are ubiquitous, locallyforming brecciae. The proximal sulphideassemblage is pyrrhotite, pyrite, chal-copyrite, sphalerite, bismuth, bismuthi-nite, arsenopyrite and gold. As much as12 ppm Au over 3.2 m in a channelsample is recorded.

Godthåbsfjord gold province

The Godthåbsfjord gold province (Tract 32)in southern West Greenland was estimat-ed to host most possible orogenic golddeposits in Greenland, but at a lower den-sity (Table 2, Fig. 1). The positive evalua-tion was based on the number of knownorogenic gold occurrences and prospectsand the favourable geology including amajor shear zone in an Archaean orogenicsetting. The panel compared the geologyand orogenic setting to the similarSouthern Cross domain in WesternAustralia that hosts 45 mines (closed andin operation).

The Godthåbsfjord gold province is anarea, where several Archaean terranesassembled during Neoarchaean orogenies(Fig. 10). A major shear-zone system, the

Ivinnguit–Ataneq fault, formed by retro-grade amphibolite facies shearing, cuttingorthogneiss and greenstone belts. Fourorogenic gold occurrences, Qilanngaarsuit,Bjørneøen, Storø and Qussuk, have beenexplored to varying extent and investigatedscientifically. Reviews of research andexploration activity are given in Kolb et al.

(2009, 2010, 2013). Numerous gold occur-rences and anomalies are known from thearea defined by Tract 32.

• Qilanngaarsuit: Gold is hosted in lami-nated quartz veins and hydrothermalalteration zones in as much as 8 mwide zones in a regional-scale synclinal

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Figure 10. Top: Geological map of the Godthåbsfjord gold province showing the various prospectsand gold occurrences. Facing page: Visible gold and pyrrhotite in a quartz vein; drill core from theStorø prospect.

GO-26_GO-26 19/02/15 15.15 Side 10

fold structure. The mineralisation canbe followed for several hundred metresalong strike with elevated gold contentsof up to 0.8 ppm Au in grab samples.The hydrothermal alteration assemblageis hypozonal and consists of garnet,quartz, plagioclase, biotite, sillimanite,pyrrhotite, chalcopyrite and gold.

• Bjørneøen: Gold mineralisation occursin magnetite-quartz veins in c. 160 mlong and 1.8 m wide zones close to afold hinge, probably forming a saddlereef geometry. As much as 4 ppm Auis found in grab samples. Hydrothermalalteration halos are hypozonal andcharacterised by garnet, quartz, biotite,actinolite, chlorite and pyrite. A meta-morphosed volcanic-hosted massivesulphide occurrence is found in thenear proximity.

• Storø: The Storø gold deposit has beendrilled extensively in two prospects,Qingaaq Mountain and Aappalaartoq.At Qingaaq Mountain, gold is hosted inlaminated quartz veins in a saddle reefgeometry in the Main Zone and the BDZone. Hydrothermal alteration zoneswith lenses of quartz veins and laminat-ed quartz veins are 10 to 50 m wide.The hypozonal assemblage consists ofgarnet, quartz, plagioclase, biotite, silli-manite, pyrrhotite, chalcopyrite,

orthoamphibole, gold, löllingite, spha-lerite, molybdenite, tellurides, ilmenite,local K-feldspar and diopside. The BDZone is 9 m wide with up to 20 g/t Auover 2.5 m, and the Main Zone con-tains up to 50 g/t Au over 2 m withwider sections of 60 m at 2.9 g/t Au insurface channel samples. Approx. 65%of the gold is recoverable by gravitymeans and more than 90% with addi-tional cyanide treatment.

• Qussuk: The Qussuk gold prospectforms a 20 km-long and 1 to 3 kmwide zone with ≤ 0.6 m wide quartzveins surrounded by 1 to 2 m widebiotite-dominated alteration zones. Thehypozonal alteration assemblage con-sists of quartz, hornblende, garnet,tourmaline, epidote, muscovite,pyrrhotite, gold and chalcopyrite. Goldgrades in diamond core, channel andgrab samples range between 1 and 22g/t in veins and alteration zones.Channel samples yield up to 21.7 g/tAu over 1.5 m and drill core intersec-tions 12.6 g/t Au over 1.1 m.

Other interesting target areas

The Archaean Bjørnesund and Sermilikorogenic gold occurrences are located inTracts 24 and 25, respectively (Figs 1 and10). Although they record gold in quartz

veins in the ppm-range, the overall geolo-gy of these tracts in the Tasiusarsuaq goldprovince has been rated less prospectivethan the Archaean tracts described above.

Greenland has orogens that formed dur-ing the most prospective eras for orogenicgold globally (Table 1), includingNeoarchaean orogens, Palaeoproterozoicorogens and the Caledonian orogen ineastern Greenland. The level of geologicalknowledge and data varies greatly forthese generally prospective areas.Individual orogenic gold occurrences aredescribed from Tracts 19 and 22, but ourunderstanding of these Archaean terranesis poor. No orogenic gold occurrences areknown from the PalaeoproterozoicNagssugtoqidian, Rinkian and InglefieldLand orogens (Tracts 14, 19, 22, 23, 30,31, 33, 34, 37; Fig. 1), which may berelated to their generally high-metamor-phic grade. However, in particular theRinkian and Inglefield Land areas arepoorly investigated. The Caledonian oro-gen has not been examined for orogenicgold occurrences, although it has all theingredients that would make it a prospec-tive area, including greenschist faciesmetamorphism, large shear-zone systems,syntectonic granite intrusions and feworogenic gold occurrences in a Cale donianthrust system (Harpøth et al. 1986).

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Concluding remarks

Greenland is regarded as very prospective fororogenic gold deposits in its Neoarchaean,Palaeoproterozoic and Palaeozoic orogens.The potential ranges from prospects wheredrill targets can be defined with relatively littleeffort to greenfield targets in poorly knownareas. The assessment resulted in the defini-tion of very prospective tracts in SouthGreenland in proximity to the closed Nalunaqgold mine and at several other localities inwestern Greenland. All areas of high prospec-tivity are close to settlements with access togood infrastructure and ice-free waters.

Key references

Bell, R.-M. & Kolb, J. 2013: Various alteration

stages in the Nalunaq gold deposit, South

Greenland. Mineral deposit research for a high-

tech world. 12th Biennial SGA Meeting, Uppsala,

12–15 August, 2013, 1093–1096.

Garde, A.A., Thomassen, B., Tukiainen, T. &

Steenfelt, A. 1999: A gold-bearing volcanogenic-

exhalative horizon in the Archaean(?) Saqqaq

supracrustal rocks, Nuussuaq, West Greenland.

Geology of Greenland Bulletin 181, 119–128.

Goldfarb, R.J., Baker, T., Dubé, B., Groves, D.I.,

Hart, C.J.R. & Gosselin, P. 2005: Distribution,

character, and genesis of gold deposits in meta-

morphic terranes. Economic Geology 100th

Anniversary Volume, 407–450.

Goldfarb, R.J., Phillips, G.N. & Nokleberg, W.J.

1998: Tectonic setting of synorogenic gold deposits

of the Pacific Rim. Ore Geology Reviews 13, 185–218.

Groves, D.I., Goldfarb, R.J., Gebre-Mariam, M.,

Hagemann, S.G. & Robert, F. 1998: Orogenic

gold deposits: A proposed classification in the con-

text of their crustal distribution and relationship

to other gold deposit types. Ore Geology Reviews

13, 7–27.

Harpøth, O., Pedersen, J.L., Schønwandt, H.K.

& Thomassen, B. 1986: The mineral occurrences

of central East Greenland. Meddelelser om

Grønland, Geoscience 17, 139 pp.

Kaltoft, K., Schlatter, D.M. & Kludt, L. 2000:

Geology and genesis of Nalunaq Palaeoproterozoic

shear zone-hosted gold deposit, South Greenland.

In: Stendal, H. (compiler): Exploration in Greenland:

discoveries of the 1990s, Transactions of the

Institution of Mining and Metallurgy, Section B,

Applied Earth Sciences 109, B23–B33.

Kolb, J. (ed.) 2011: Controls of hydrothermal

quartz vein mineralisation and wall rock alter-

ation in the Paamiut and Tartoq areas, South-West

Greenland. Danmarks og Grønlands Geologiske

Undersøgelse Rapport 2011/114, 176 pp.

Kolb, J., Stensgaard, B.M., Schlatter, D.M. &

Dziggel, A. 2009: Controls of hydrothermal

quartz vein mineralisation and wall rock alteration

between Ameralik and Sermilik, southern West

Greenland. Danmarks og Grønlands Geologiske

Undersøgelse Rapport 2009/25, 76 pp.

Kolb, J., Dziggel, A., Koppelberg, M., Stoltz,

N.B., Kisters, A.F.M. & Bergen, A. 2010:

Controls of hydrothermal quartz vein minerali-

sation and wall rock alteration between Sermilik

and Grædefjord, southern West Greenland.

Danmarks og Grønlands Geologiske Undersøgelse

Rapport 2010/47, 73 pp.

Kolb, J., Dziggel, A. & Schlatter, D.M. 2013:

Gold occurrences of the Archean North Atlantic cra-

ton, southwestern Greenland: a comprehensive

genetic model. Ore Geology Reviews 54, 29–58.

Pettke, T., Diamond, L.W. & Kramers, J.D. 2000:

Mesothermal gold lodes in the north-western

Alps: a review of genetic constraints from radi-

ogenic isotopes. European Journal of Mineralogy

12, 213–230.

Stendal, H. & Frei, R. 2000: Gold occurrences

and Pb isotopes in the Ketilidian mobile belt,

South Greenland. In: Stendal, H. (compiler):

Exploration in Greenland: discoveries of the

1990s, Transactions of the Institution of Mining

and Metallurgy, Section B: Applied Earth Sciences

109, B6–B13.

Stendal, H., Knudsen, C., Marker, M. &

Thomassen, B. 1999: Gold mineralisation at

Eqi, north-east Disko Bugt, West Greenland.

Geology of Greenland Bulletin 181, 129–140.

Front cover photographGeologist mapping a stope wall in theNalunaq gold mine underground operation. The auriferous quartz vein iscomposed of several parallel laminae,dipping moderately to the southwest.The rusty red colour is iron-staining andstems from sulphide weathering. The dark host rock (amphibolite) alsoshows internal banding parallel to theauriferous vein, representing composi-tional variation.

Ministry of Mineral Resources (MMR)Government of Greenland

Postbox 1601Imaneq 1A, 201

3900 NuukGreenland

Tel: (+299) 34 50 00Fax: (+299) 32 43 02E-mail: isiin@nanoq.gl

Internet: www.govmin.glwww.naalakkersuisut.gl

www.greenmin.gl

Geological Survey of Denmark and Greenland (GEUS)

Øster Voldgade 10DK-1350 Copenhagen K

Denmark

Tel: (+45) 38 14 20 00Fax: (+45) 38 14 20 50E-mail: geus@geus.dkInternet: www.geus.dk

AuthorJochen Kolb, GEUS

EditorLars Lund Sørensen, GEUS

Graphic ProductionAnnabeth Andersen, GEUS

PrintedFebruary 2015 © GEUS

PrinterRosendahls • Schultz Grafisk a/s

ISSN1602-818x

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Panoramic view of Aappalaartoq on Storø seen from Qingaaq Mountain to the northeast. A numberof gold prospects are located in a 12 km2 area between the two mountain ranges. Copyright MMR.

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