Abstract The Gulf Coast is a young basin with many geologic features that commonly are regarded as critical to the development of sediment-hosted mineral deposits. Metalliferous formation waters are locally present in the Gulf Coast Basin and have been proposed as modern analogs for the ore-forming fluids for ore deposits in older sedimentary terranes. Synsedimentary growth faults are important features that control local depositional facies and subsequent fluid movement in the Gulf Coast. Zn-Pb-Ag sulfide concentrations in salt dome cap rocks and shelf carbonates have been identified in the Gulf Coast. These sulfides have the most direct genetic affinity with Mississippi Valley type ore deposits that typically occur in older sedimentary terranes, although the cap rock occurrences have some similarities to SEDEX-style mineralization. Recently discovered barite mounds on the floor of the Gulf of Mexico provide a modern analog for the seafloor discharge of metal-bearing formation waters in a sedimentary basin. Salt dome cap rock mineralization is thought to be the result of the episodic injection of a deep-sourced, relatively hot, metal-bearing brine into the shallow cap rock environment where it mixed with a cool, dilute solution that was rich in H 2 S produced by bacterial sulfate reduction accompanying hydrocarbon oxidation. Reaction path geochemical modeling with SOLVEQ/CHILLER supports this model for the massive sulfide mineralization within the bioepigenetic calcite cap rocks and also shows that simple cooling (by 25 to 50°C) of a brine saturated with metal sulfides under reservoir conditions would lead to the precipitation of the sulfides. Adding H 2 S to a fluid close to saturation with respect to Fe, Zn, and Pb sulfides also would cause sulfide deposition without calcite deposition, as both the addition of H 2 S and sulfide deposition have the effect of lowering the pH, thus inhibiting calcite precipitation. This mechanism may explain the formation of the anhydrite-hosted stratiform sulfide laminae that formed at the salt/cap rock contact during the accretion of the anhydrite cap rock. Modeling further suggests that some H 2 S-rich brines (with low Zn and Pb contents) could contain appreciable dissolved Ag which would produce Ag-rich concentrations upon cooling or dilution. These geological and geochemical features support a genetic relationship among petroleum destruction, sulfate reduction by bacterial or thermochemical mechanisms, and Fe-Zn-Pb-Ag sulfide and Ba-Sr sulfate precipitation in environments ranging from ocean floor precipitates that are analogous to sedimentary exhalative ore deposits to deep intrastratal positions in carbonate formations that are similar to Mississippi Valley type deposits.

Abstract Salt domes, their cap rocks, and the adjacent sedimentary strata represent a major economic resource in the Gulf Coast and elsewhere. The resources and utilization of the salt dome setting are remarkably diverse. Major economic products of the salt dome environment are salt, cap rock-hosted native sulfur deposits, and oil and gas that occur on the dome flanks and in the cap rock. Some cap rocks are sources of limestone, gypsum, and anhydrite, and some host commercial concentrations of Zn and Pb. Uranium is concentrated in strata above or adjacent to some diapirs. Caverns, excavated within the salt, serve as product storage as diverse as crude oil, including the Strategic Petroleum Reserve, liquified petroleum gas, and hazardous waste. In addition, the Gulf Coast is a geologically young basin with many components that commonly are regarded as critical for the development of sediment-hosted mineral deposits. Metalliferous formation waters are locally present in the Gulf Coast Basin and have been proposed as modern analogs for the ore-forming fluids for ore deposits in older sedimentary terranes. Synsedimentary growth faults are important features that control local depositional facies and subsequent fluid movement in the Gulf Coast. Zn-Pb-Ag sulfide concentrations in two principal host settings (salt dome cap rocks and shelf carbonates) have been identified in the Gulf Coast. These sulfides have the most direct genetic affinity with Mississippi Valley type ore deposits that typically occur in older sedimentary terranes, although the cap rock occurrences have similarities to SEDEX-style mineralization. Recently discovered barite mounds on