Abstract: Uranium Deposits of Northern Saskatchewan

L. S. Beck

Northern Saskatchewan forms part of the Churchill structural province of the Canadian shield and is underlain by Archean and Aphebian rocks that were metamorphosed and granitized during the Hudsonian orogeny (ca. 1,750 m.y. ago). In places the orogene is overlain by unmetamorphosed Helikian rocks including the Martin and Athabasca Formations.

There are two main types of economic uranium deposits:

1. The "Beaverlodge type" consists of epigenetic fracture fillings of pitchblende in quartz and carbonate gangues spatially related to major faults and mylonite zones in the basement. Pitchblende was introduced initially about 1,780 m.y. ago, at temperatures as high as 440°C. The most widely accepted genetic theory considers the source of uranium to be syngenetic materials in the basement that were mobilized by metamorphic-hydrothermal fluids during the Hudsonian. Recently, a supergene origin has been proposed which relates uranium mineralization to the weathering of the basement after the Hudsonian event.

2. The "unconformity type" consisting of epigenetic pitchblende deposits in quartz-carbonate gangues is associated closely with a regolith underlying the Athabasca Sandstone. Initial mineralization may have occurred about 1,000 m.y. ago and some of the uranium was emplaced below 100°C. In view of this, a supergene origin for the deposits is currently fashionable. In contrast, however, there is a view that the deposits are hypogene veins which have been reworked partly or completely by groundwaters.

Other types of uranium deposits in northern Saskatchewan, which are presently uneconomic, are (a) uraninite-bearing pegmatites, (b) uraninite in calc-silicates, and (c) complex U-Co-Cu-Ag-Au mineralization in quartzite.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC