Isotopic composition of various forms of sulfur in barite crusts from the Red Sea rift

Barite crusts were formed by an intermittent hydrothermal vent with output temperature from 85 to 465°C. Principal sources of supply of sulfate sulfur are sea water, evaporites, and tholeiitic basalts of the Red Sea rift. Sulfides and sulfates were formed in conditions of isotope disequilibrium with respect to sulfur because rate of precipitation of sulfur compounds from hydrothermal solution was high compared with rate of isotope exchange.

Composition of barite crusts and basalts from the Red Sea rift zone

Barite ores with admixture of sphalerite that occur in the Atlantis-II Deep are indicated by their geological position, structure, and mineral and chemical characteristics and by isotope composition of sulfur and oxygen in them to be of hydrothermal origin. They were produced close to an orifice of an intermittent hydrothermal vent by chemogenic precipitation of barite onto cooled basalt.