Geological Survey of Denmark and Greenland Bulletin 18, 2009, 78-91
Total Page：16
File Type：pdf, Size：1020Kb
Mineral deposits Mineral raw materials in Greenland occur in a series of rocks. The Nalunaq Gold Mine in Kirkespirdalen (a val- different geological environments that include sedi- ley north-east of Nanortalik) operated from 2004 to mentary deposits, metamorphic crystalline rocks, and 2008, but the mine is presently (2009) placed on ‘care volcanic and plutonic rocks. An overview of selected and maintenance’. Another find substantiating the inter- mineral occurrences with their place names are shown pretation of the Ketilidian orogen as a gold province was in Fig. 54. made in southernmost South-East Greenland, where Mining activities have been carried out in Greenland gold mineralisation was found in a quartz-bearing shear since the middle of the 19th century, with the cryolite zone cutting a sequence of mafic to andesitic extrusives mine at Ivittuut as the only long-term mine; it was in and intrusives and associated sedimentary rocks. The operation for a period of 130 years. The cryolite deposit promising gold mineralisations in South Greenland are was associated with a granite intrusion in the Meso - situated at the southern border of the Julianehåb batholith proterozoic Gardar Province of South Greenland (p. 38), (p. 29), which is also the root zone of a former volcanic and represents an example of a very rare type of miner- arc (Chadwick & Garde 1996; Garde et al. 1998, 2002; alisation, of which there are only very few similar deposits McCaffrey et al. 2004). in the world (Pauly & Bailey 1999). Other mining activ- Exploration for base metals in recent years has focused ities in Greenland have exploited more common types on showings in the Lower Palaeozoic Franklinian Basin of mineralisation. The two most important ones were both and Ellesmerian fold belt of North Greenland. A mas- lead-zinc deposits – one at Mestersvig in East Greenland sive sulphide deposit with lead and zinc was discovered was associated with quartz veins of probable Palaeo - in 1993 at Citronen Fjord in Peary Land (Fig. 54; van gene age, and the other at Maarmorilik in central West der Stijl & Mosher 1998). It occurs as stratiform sheets Greenland was a stratabound mineralisation in the in a folded sequence of dark argillaceous rocks of the Palaeoproterozoic Mârmorilik Formation (p. 27). Most Upper Ordovician to Lower Silurian Amundsen Land recently a gold occurrence in Kirkespirdalen in the Group. The Citronen Fjord deposit is located at the east- Palaeoproterozoic Ketilidian orogen, South Greenland, ern end of the Franklinian Basin, which extends across has been mined (Nalunaq Gold Mine, see below). North Greenland into Arctic Canada and is known to Mining activities have so far been very limited in be a significant prospective zone which includes the Green land considering the expected potential of such a Polaris zinc-lead mine in Canada. large area. However, systematic exploration did not com- Diamond exploration has focused on the Archaean and mence until the late 1950s when new legislation governing Palaeoproterozoic crystalline shield areas of West Green - the mineral sector was introduced to encourage the min- land. The kimberlite province in this region in cludes the ing industry to undertake exploration. This was inten- Archaean craton and areas of Archaean rocks farther north sified with the introduction of Home Rule status for reworked during the Palaeoproterozoic. The province con- Greenland in 1979. tains various Meso–Neoproterozoic ultramafic lam - In recent years exploration activities have concen- prophyres (UML) as well as Mesozoic UML-intrusions. trated on prospecting for gold, base metals, platinum elements, molybdenum, iron ore and diamonds. Gold exploration has focused on the Archaean and Palaeo - proterozoic Precambrian shield of West Greenland and the Palaeogene Skaergaard layered gabbro intrusion (p. 62) in southern East Greenland (Andersen et al. 1998; Secher et al. 2007). A major new gold province in the Facing page Palaeoproterozoic Ketilidian orogen forming the south- Fig. 54. Map of known mineral occurrences in Greenland. The presentation combines the geological map with the knowledge of ern tip of Greenland (Steenfelt 2000; Stendal & Frei mineral prospects and deposits gathered over more than 150 years. 2000; Stendal & Secher 2002) was first recognised by The main geological divisions on the geological map cover periods panning of stream sediments, and in 1992 visible gold from Archaean to Palaeogene and are summarised in the legend. was found in quartz veins transecting mafic supracrustal From GEUS Department of Economic Geology. 78 Navarana Fjord Citronen Fjord ▲ CanadaC a n a d a Zn, Barite Zn, Pb a n d I s l e r e s m Washington Land ▲ e l ▲ l Zn, Pb, Ag ▲ E ▲ ▲ ▲ ▲ ■ ■ ■ ▲ ■ ■ ▲ ■ ▲ ■ ▲ ▲ ▲ ▲ ▲ ▲ Inglefield Land Fe, Au,Cu ■ ■ ■ ■ Moriusaq ■ Ti ■ ■ ■ ▲ ▲ ▲ ▲ Melville Bugt ▲ Fe ■ ■ ■ INLAND ICE ■ ■ Brogetdal ■ Cu ■ Clavering Ø ■ ■ Pb, Zn, Fe ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Ymer Ø Sb, W, Au ■ ■ ■ ■ ■ Mestersvig (‘Blyklippen’) ■ ■ Langø ■ Pb, Zn ■ ■ Graphite Malmbjerg ■ ■ Mo, W ■ ■ Karrat ▲ ▲ ■ Bredehorn ▲ ▲ Au, Cu, Zn ▲ Barite ▲ Devon Dal Hammer Dal Maarmorilik (‘Black Angel’) Cu ■ ■ Fe, Pt Zn, Pb, Ag ■ ■ ■ ■ Karstryggen ■ ▲ Qullissat ▲ Celestite ■ Saqqaq ▲ ▲ ■ ▲ ▲ Coal ■ Au Milne Land Nuussuaq Zr, REE, Ti Coal Itilliarsuk, Itilli Fe, Au, Cu, Co, Ni Ilukunnguaq Ni, Pt Eqi Arveprinsen Ejland Au Cu, Zn Flammefjeld Attu Naternaq Mo, Au, Ag Skærgaard Au Cu, Zn Au, Pd, Ti, V Eqalussuit Kap Edvard Holm Graphite ▲ ▲ ▲ ▲ ▲ Au, Pt ▲ ▲ ▲ ▲ Sarfartoq Sillisissanguit Nb, Ta Ni, Pt Tasiilaq Ni, Cu, Pt Qaqqaarsuk Kangerlussuaq Diamond Iceland REE, Nb, P ▲ Palaeogene basalts ▲ ▲ Isukasia ▲ Majuagaa Fe Cretaceous–Palaeogene sediments, Nuussuaq Basin in Diamond West Greenland and Kangerlussuaq Basin in East Greenland Seqi Isua Carboniferous–Palaeogene sediments, Olivine Au Wandel Sea Basin in eastern North Greenland Amikoq Ivisaartoq Carboniferous–Cretaceous sediments, North-East Greenland Pt, Pd, Os W Carboniferous–Cretaceous sediments, Qussuk Sinarsuk Jameson Land Basin in East Greenland Au Storø V, Ti Devonian Basin of North-East Greenland Au Fiskenæsset Shelf Cr, Pt, Ruby Lower Palaeozoic sediments, North Greenland, Franklinian Basin Trough Taar toq Au Motzfeldt Sø Palaeo- to Neoproterozoic sediments and volcanic rocks Ta, Nb Ivittuut Caledonian orogenic belt Cryolite Kangerluluk Au Palaeoproterozoic orogenic belts Grønnedal-Ika Fe Stendalen Cu, Ni, Ti Archaean craton Kobberminebugt (‘Josva’) Illorsuit Intrusive complexes: Palaeogene in East Greenland, Cu Ilímaussaq Mesoproterozoic in South Greenland (Gardar Province) Zr, Be, REE, Nb, U, Th U ▲ ▲ Fault, thrust Niaqornaarsuk ▲ ▲ 250 km Amitsoq Au Mine site Graphite Nalunaq Au Abandoned mine 79 A large number of these intrusions contain diamonds, and intensive exploration activity has been in progress Archaean–Palaeoproterozoic since the 1990s (Secher & Jensen 2004; Jensen et al. high-grade regions 2004; Nielsen et al. 2009). At present more than 1000 At Isukasia (Isua supracrustal sequence [69]; Fig. 54) occurrences of diamondiferous kimberlite dykes have north-east of Nuuk, a major Archaean banded iron for- been found, and the largest diamond so far discovered mation is composed of interlayered magnetite and chert is of 2.5 carat. The Archaean block also contains three (Fig. 5). The deposit, which is partly covered by the In - large intrusive carbonatite complexes with a resource land Ice, has been drill tested and a minimum tonnage potential for various speciality commodities such as nio- of 1900 million tonnes grading 32.9% Fe is estimated bium and tantalum. (Niel sen 1976; Appel 1991). The Nuuk region in southern West Greenland has revealed a good potential for gold mineralisations (Stensgaard & Stendal 2007). The gold occurs in the Mineral occurrences in specific supracrustal parts of the Archaean craton, which largely geological settings consists of amalgamated islands arcs, which gradually Significant occurrences of a broad range of metallic and merged into micro-continental blocks (Windley & Garde industrial minerals are present in all the principal geo- 2009). The supracrustal belts reflect both island-arc and logical provinces in Greenland, ranging in age from ocean-floor environments, and also contain ultramafic Archaean to Quaternary (Fig. 54; Schønwandt & Dawes to mafic magmatic intrusions. Gold showings occur in 1993; Stensgaard & Thorning 2009). In broad terms a NNE-trending belt along the fjord Nuup Kangerlua these can be related to five main settings: (Godthåbsfjord) from Nuuk to Isukasia, and a multi- disciplinary approach has now resulted in division of the Archaean–Palaeoproterozoic high-grade regions occurrences into three main groups (Stensgaard & Stendal Mesoproterozoic intracratonic intrusions 2007). The occurrences contain up to 3–7 g/t Au with Palaeozoic orogenic belts local grades of up to 20 g/t Au. Intensive exploration Upper Palaeozoic – Mesozoic basins with drilling both north and south of the fjord has been Late Phanerozoic intrusions. undertaken since 2003. A series of gold occurrences has also been found in the The following description covers the principal active crystalline basement rocks of the Nagssugtoqidian oro- and former mines and some significant prospects (Fig. gen north-east of Disko Bugt, central West Greenland. 54); at present (2009) there are two active mines, although Here Archaean orthogneisses with their Archaean and one is ‘on hold’. On the printed map sheet the locations Palaeoproterozoic cover rocks have been variably affected of only