Reactive Flow Modeling Investigation into the Effects of Paleo-regoliths on the Formation of Uranium deposits

Reactive fluid flow modeling is conducted using TOUGHREACT to examine the effect of paleo-regoliths on uranium ore genesis. A 2-D conceptual model is developed based on the common characteristics of some unconformity-related uranium deposits in the Athabasca basin, Canada, where regional paleo-regoliths are commonly present beneath the unconformities and are offset by reactivated fault zones. Numerical results indicate that the paleo-regoliths are important in governing fluid circulation, which in turn controls the temperature distribution, the transport of aqueous components, the water-rock reactions, and the uranium deposition. The permeable regoliths tend to facilitate the oxidizing basinal fluid to be concentrated in the footwall of the fault zones where it reacts with the reducing basal brine to precipitate uraninite. The greater the thickness of the regoliths is, the stronger such a concentrating effect. Numerical results also exhibit that a 'down-slope' flow develops over the fault offset of the unconformities, which shifts the uranium deposits to be formed away from the fault zones.