GOLD ENVIRONMENTS AND FAVOURABILITY

GOLD ENVIRONMENTS AND FAVOURABILITY52°W Sillissianguit51°W50°WIsua GreenstonebeltInlandIceIsukasiaNagssugtoqidianorogenSimplified schematic geologicalmap of the Nuukregion with general indicationof different geologicalenvironments.Outlines of the rock unitsare from digital versionsof 1:100 000 and 1:2500 000 scale geologicalmaps published by theSurvey.Q: Qingaaq;A: Aappalaartoq;S: Seqi Olivine mine.The statistically definedgroups of gold showingsin the region are alsoindicated (a gold showingis defined as a localitywhere in situ rock samplesyielded 1 g/t Au).65°NDavisStrait64°30'NFiskefjordNordlandetNuukSGodthåbsfjordSermitsiaqQussukBjørneøenAmeralikQ AQooqqutStorøIvisaartoqGodthåbsfjord25 kmNorthAtlanticcratonNuukregionKetilidianorogenGneiss -infracrustalMajor faults andshear zonesSupracrustalenvironments:UnknownIsland ArcOcean FloorMagmaticGroups of goldshowings:Isua gold groupBjørneøen gold groupStorø gold groupUngroup showingsuted to seafloor hydrothermal alteration.The Ivisaartoq belt hosts volcanic massivesulphide deposits (semi-massive to massivepyrite-pyrrhotite) and disseminated tungstenin altered komatiites (channel sampleswith 0.44% WO 3 over 2.5 m). Showingswith up to 3.5 g/t Au are recorded withinthe Ivisaartoq belt.Ocean-floor environmentThe 3.8 Ga Isua greenstone belt representsan ocean-floor environment. The dominatingrock types in this belt are pillow-structuredtholeiitic and high Mg-basaltic rockswith intercalated, extensive bands of chertand banded iron formation, turbidites aswell as garnet-mica schist representingmetamorphosed sediments. Gold occurrenceshave been found in several settingswithin the Isua greenstone belt.• In silicate facies iron formation(up to 1.2 g/t Au)• In fuchsite-stained quartz-rich rocks(up to 3.1 g/t Au over 3 m)• In shear-zone hosted, carbonatealteredultrabasic rocks (grab sampleswith up to 100 g/t Au).A hydrothermal episode affected a c.3.8 Ga intrusive tonalite sheet in the westernpart of the Isua greenstone belt. Thebelt contains up to 14% combined Pb andZn with up to 6.8 g/t Au and 180 g/t Ag.Well-preserved, volcanic successionsinterpreted as environments dominated byocean-floor settings are described fromseveral other areas in the Nuuk region. Bimodal,volcanic succession in greenschistfacies is described from the ‘Nunatak 1390’in the Tasiuarsuaq terrane. Voluminouslylayered amphibolites and well-preservedpillow lava at Bjørneøen, associated withhomogenous, metagabbroic amphiboliteare also interpreted as a primary oceanfloor environment. A small VMS showingis located in the south-western part of thebelt at Bjørneøen. This showing containsup to 3.55% Zn, 1.33% Pb, 33 g/t Agand 0.153 g/t Au.Magmatic environmentThe Nordlandet and Fiskefjord areas aredominated by mafic to ultramafic sequencesincluding dunite, peridotite, pyroxenite,norite and amphibolites hosted by tonaliticand trondhjemitic gneisses. In manycases relict magmatic layering is preserved.This area comprises probably both primarymagmatic environments and relicts ofgreenstone belts. The mafic to ultramaficcomplexes south of Fiskefjord show enhancedvalues of Au and PGE. The SeqiOlivine Mine operated by Minelco AB islocated just north of central Fiskefjord.The deposit contains at least 100 milliontonnes of high-quality olivine and is hostedwithin a large dunite body.The supracrustal belt at central Storø isof a complex character and much debated.It seems that this belt may contain characteristicsof both continental and oceanicvolcanic and sedimentary rocks. The areais furthermore affected by intense foldingand major shearing, making straight interpretationseven more difficult. The area mayrepresent an accretion environment alongboundaries of different terranes (amalgamatedaround 2.7 Ga). Central Storø hoststhe Qingaaq Gold prospect which is investigatedand drilled by NunaMinerals A/S.Several gold bearing structures, 4–36 mwide, have been found at Qingaaq withgrades from 0.5 to 6 g/t Au and locally2–4 m wide zones with grades up to 20g/t Au.3