Tungsten mineralization in the Nuuk region, West Greenland

The first traces of scheelite in West Greenland were found in Godthåbsfjord in 1982. Subsequent field work revealed scheelite in the mid-Archaean Malene supracrustal rocks occurring as enclaves in gneisses over an area of at least 35 000 km² . Of lesser importance from an economic point of view is the scheelite in the early Archaean Isua-Akilia supracrustal enclaves.

The Malene supracrustal rocks comprise thick sequences of basic and ultra-basic pillow lavas interspaced with peridotites as well as miner amounts of cordierite-silimanite-bearing quartz-mica schists. The scheelite in the Malene supracrustal rocks is stratabound and occurs in banded amphibolites and calc-silicate horizons. The scheelite-bearing horizons are associated with tourmalinites, pyrite-rich zones and locally with gahnite-bearing sulphide-rich anthophyllite-gedrite rocks. The scheelite-bearing zones can be traced for kilometres along strike.

The scheelite occurs as small grains and veinlets arranged parallel to the banding of the rock, as disseminated grains, as cm-sized porphyroblasts and as joint coatings. Most of the scheelite has a low molybdenum content.

In the Ivisartoq area of the inner Godthåbsfjord, a c. 3.5 km long scheelite-bearing calc-silicate horizon has been channel sampled. This revealed up to 0.35 % tungsten over a width of 2.5 m, but the grades vary considerably along strike. Towards the end of the field season a scheelite-bearing calc-silicate zone was found at several sites in an about 10 km long peridotite horizon, which separates two basic volcanic cycles. Channel sampling revealed up to 0.38 % tungsten over a width of 1.5 m.