J. L. Bischoff Wayne C. Shanks III 1977 <p>Thermodynamic calculation of distribution of dissolved aqueous species in the Red Sea geothermal brine provides a model of ore transport and deposition in good agreement with observed accumulations of base metal sulfides, anhydrite, and barite.</p><p>The Red Sea brine is recirculated seawater that acquires high salinity by low-temperature interaction with Miocene evaporites and is subsequently heated to temperatures in excess of 200°C by interaction with recent rift zone intrusive rocks. At temperatures up to 250°C, NaSO⁻₄<span>&nbsp;</span>and MgSO⁰₄<span>&nbsp;</span>are the dominant sulfur-bearing species. H₂S forms by inorganic sulfate reduction at the higher temperatures but is maintained at a uniform concentration of about 2 ppm by the strength of the sulfate complexes.</p><p>Chloride complexes solubilize metals at the higher temperatures, and thus sulfide and metals are carried together into the Atlantis II Deep. Below 150°C, the brine becomes supersaturated with respect to chalcopyrite, sphalerite, galena, and iron monosulfide due to chloride-complex dissociation. Sulfide precipitation rates, based on the rate of brine influx, are in good agreement with measured sedimentation rates. Anhydrite precipitates as crystalline fissure infillings from high-temperature inflowing brine. Barite forms from partial oxidation of sulfides at the interface between the lower hot brine and the transitional brine layer.</p> application/pdf 10.1016/0016-7037(77)90255-1 en Elsevier Ore transport and deposition in the Red Sea geothermal system: a geochemical model article