The possible role of sulfate-reduction kinetics in the formation of hydrothermal uranium deposits

As a sulfate-bearing, hydrothermal solution cools to less than about 200°C, kinetic factors prevent sulfate from entering into oxidation-reduction reactions. Consequently, the reducing effect of H₂S (and other reduced species) is not balanced with the oxidizing effect of SO_4⁼ to the same extent as at higher temperatures. The result is a lower effective Eh of the system. This decrease in the effective Eh due to a slowing of the rate of sulfate reduction with cooling may be the precipitation mechanism for many types of ore deposits.