The formation of unconformity-type uranium ore deposits 1. Coupled groundwater flow and heat transport modeling

Abstract

Unconformity-type ore deposits of Middle Proterozoic age account for more than 25% of the world's proven uranium reserves. Most of these uranium deposits are found within the Athabasca Basin, Saskatchewan, Canada and the McArthur Basin, Northern Territory, Australia. The ores are typically associated with unconformable contacts between Archean to Early Proterozoic metamorphic basement and overlying Middle Proterozoic sandstones that comprise thick sequences in continental rifts and intracratonic sags. Earlier geochemical and fluid inclusion studies have shown that these high-grade uraninite deposits formed by the migration of basinal brines at temperatures of 110°C to 240°C. This paper examines the role of thermally-driven free convection as a mechanism for the driving regional groundwater flow systems and uranium ore formation within Proterozoic sedimentary basins. The possible role of topography-driven flow is also examined as another hydrogeologic mechanism for large-scale migration of ore-forming brines within the sedimentary basin and fractured basement. -from Authors