title: The S3- ion is stable in geological fluids at elevated temperatures and pressures.
abstract: The chemical speciation of sulfur in geological fluids is a controlling factor in a number of processes on Earth. The two major chemical forms of sulfur in crustal fluids over a wide range of temperature and pressure are believed to be sulfate and sulfide; however, we use in situ Raman spectroscopy to show that the dominant stable form of sulfur in aqueous solution above 250°C and 0.5 gigapascal is the trisulfur ion S(3)(-). The large stability range of S(3)(-) enables efficient transport and concentration of sulfur and gold by geological fluids in deep metamorphic and subduction-zone settings. Furthermore, the formation of S(3)(-) requires a revision of sulfur isotope-fractionation models between sulfides and sulfates in natural fluids.
authors.affiliation: Géosciences Environnement Toulouse (GET, ex-LMTG), UMR 5563 of CNRS, Université Paul Sabatier, 14, avenue Edouard Belin, F-31400 Toulouse, France. gleb.pokrovski@get.obs-mip.fr
authors.forename: Gleb S
authors.initials: GS
authors.lastname: Pokrovski
authors.forename: Leonid S
authors.initials: LS
authors.lastname: Dubrovinsky