Geology and evaluation of the uranium mineral occurrence at Igdlorssuit, South Greenland

Geological and radiometric mapping, and petrological and mineralogical investigations were made of a uranium mineral occurrence at Igdlorssuit, South Greenland during 1984 and 1985. The results have been evaluated in terms of the uranium potential and genesis the showing. The work was part of the South Greenland Exploration Programme (Sydex) carried out by the Geological Survey of Greenland (GGU) in cooperation with Risoe National Laboratory (Risoe). It was financed by the Danish Ministry of Energy. Igdlorssuit is located at the northerly limit of the fjord system about 60 km north of Kap Farvel (60 deg. 23 min.; 46 deg. 06 min.). The main uranium mineral showing is on a small alp on the eastern side, 500 m vertically above the fjord. Detailed plane table mapping (1:1000), and radiometric measurements with a lead collimated scintillometer calibrated for uranium delineated this occurrence: Regional mapping (1:10 000), however, showed that it was only one of many similar uranium occurrences in the area albeit the largest and richest. Over 35 uranium mineral occurences have been found scattered over the hillside. Textural and paragenetic relationships, and isotopic data show that the uranium was present in the supracrustal units before the folding, metamorphism and intrusion of the granite. The largest, highest grade uranium mineralised zone is about 50m long and up to 5m wide with an average grade of 0.31% with highs up to 7%. The results of the mapping and sampling has established that this type of mineral occurence can reach economic grades, and its surface expression suggests a size which could approach economic proportions. 3 maps, 30 refs. (EG)