The role of thermochemical sulfate reduction in the origin of Mississippi Valley‐type deposits. II. Carbonate–sulfide relationships

Abstract The two‐dimensional (2D) reactive transport model of Corbella et al. [ Min. Deposita 39 (2004) 344] of the classic ‘mixing hypothesis’, in which a solution containing reduced sulfur and a solution containing aqueous Zn are mixed, has been extended to the case where one brine contains sulfate rather than reduced sulfur, and H 2 S is produced during the mixing process by thermochemical sulfate reduction (TSR), using a possible rate law and experimentally derived rate constants. It is shown that TSR can provide sufficient reduced sulfur to form an ore body in geologically reasonable times, using rate constants in the upper part of the experimental range, in agreement with the results of a constant stirring tank reactor model ( Thom & Anderson in press ). The results of the 2D model are also compared with the results of titration (zero dimensional) and one‐dimensional models, showing that these models fail to adequately show the amount of carbonate precipitation. Although the 2D model qualitatively shows the distribution and amounts of carbonate precipitation and dissolution, these results are quantitatively inaccurate due to several factors that are intrinsically hard to define.