Location of Uranium-Rich Brines Determines the Distribution and Grade of Unconformity-Related Uranium Deposits

Recent fluid inclusion analysis indicates that uranium-bearing brines were present in both the sandstone and the basement at the time of ore genesis in the Athabasca Basin, Canada. However, the question of how the location of uranium-rich brines controls the formation of unconformity-related uranium deposits remains unresolved. In this study, four reactive flow modeling scenarios are designed to address this outstanding issue. Our numerical results confirm that the basement-hosting uranium-rich brines are capable of forming high-grade concentrated uranium deposits in the footwall region of the fault zone below the unconformity interface. In contrast, the sandstone-hosting uranium-rich brines lead to the formation of low-grade sheet-like uranium mineral precipitates above the sandstone layer rather than in the basement. Therefore, this study reveals that unconformity-related uranium deposits tend to be formed when the basement unit serves as the main uranium source. Taking the sandstone layer as the main uranium source, no unconformity-related uranium deposits can be formed since the resultant uranium precipitation has no spatial relation with the unconformity interface.

Automated summary

This study utilizes reactive flow modeling to investigate the formation of unconformity-related uranium deposits and reveals the importance of the location of uranium-rich brines. The results indicate that uranium deposits are more likely to form when the basement serves as the main uranium source.