Abstract
In 1982 scheelite was identified in stream sediments in the: Nuuk/Godthåb area, about 600 km south of Atâ. Subsequentlya regional stream-sediment programme was carried out in the Nuuk area from 1982 to 1987 as a result of which scheelite was found to be quite abundant in the 3800 m.y. old Isukasia supracrustalrocks as well as in the 3300 to 3000 m.y. old Malene supracrustal sequence (Appel, 1988). It was also recognised that there is a close correlation between the number of scheelite grains and the gold content of the heavy mineral concentrates in the Nuuk area (Appel, 1988). In the Ata area (fig. 1) extensive outcrops of supracrustal rocks are found. In these supracrustals, which have been metamorphosed to greenschist and amphibolite facies, abundant sulphide-rich horizons are found, as well as sulphide-bearing breccia zones with appreciable gold contents (Knudsen et al., 1988). During the 1987 field season geological reconnaissance mapping was carried out in two of the supracrustal areas and the gneiss-granite complex enclosing the supracrustal rocks ·was investigated (Knudsen et al., 1988). A limited programme of stream-sediment sampling was carried out in the Atâ area, where stream sediment samples were collected in all the main streams draining the supracrustal rocks.
Highlights
The stream sediments collected in the Atå area consisted of coarse grave! and sand collected in sieves which contain about 3 kg of sample material
Most of the scheelite apparently occurs in the supracrustal rocks which have undergone amphibolite facies metamorphism
From this work and from the abundance of scheelite previously discovered in the supracrustal rocks further south (Appel, 1988) it is concluded that scheelite is probably more cbmmon in Precambrian supracrustal sequences than hitherto realised
Summary
The stream sediments collected in the Atå area consisted of coarse grave! and sand collected in sieves which contain about 3 kg of sample material. The stream sediments collected in the Atå area consisted of coarse grave! Sand collected in sieves which contain about 3 kg of sample material. The material was passed through a sieve with 1 mm holes. The fines were measured by volume and concentrated by panning. The heavy mineral concentrates were dried and the number of scheelite grains counted under ultra-violet light (except samples 353024 and 353025).
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