Preliminary data on U and Th values in the basement rocks of the W. Saskatchewan shield

Analysis of 1165 samples of basement rock for U and Th (NAA) and major elements (ICP) has been completed. The mean U and Th values of 1.12 and 9.22 ppm respectively are lower than published averages for the Western Canadian Shield in general and the Churchill Province in particular. Three U/Th lithological associations can be identified. Distinction between the groups can be explained in terms of pre-Hudsonian lithological controls with some Hudsonian remobilization. Some transfer of U from high grade metasediments into co-eval anatectites is observed. More complete anatexis at depth may be responsible for the U/Th enriched plutons such as the Junction Granite in the Virgin River Shear Zone