SALT DOME CAP ROCK IN THE CENTRAL AFRICAN COPPERBELT, ZAMBIA AND THE DEMOCRATIC REPUBLIC OF CONGO (DRC)

Halokinesis has been invoked in the Katangan basin to account for the development of megabreccias in the Central African Copperbelt. However, halite and associated cap rocks, common in modern salt structures, have not been recognized to date. Cap rock formation is a multi-step process principally involving halite dissolution and anhydrite concentration followed by microbially mediated conversion of anhydrite into calcite in the presence of hydrocarbons. Native sulfur is a common byproduct of this process and locally occurs with minor pyrite, sphalerite, and galena. Observations from two locations in the DRC and one location in Zambia document carbonate (calcite and dolomite), native sulfur, pyrite, and sphalerite that occur in relatively thin layers adjacent to polylithic breccias. These polylithic breccias are interpreted to be the remnants of halokinetic evaporites and their spatial association with the carbonates, native sulfur, and sulfides supports the interpretation that these sequences represent the first documented occurrence of salt-related cap rock in the Central African Copperbelt. Results of ongoing isotopic analysis will be presented to compare C, O, and S isotopic signatures from these cap rock horizons to modern biogenic minerals in salt dome cap rocks, which show marked negative isotopic shifts.