Contrasts of Fluid Chemistry, Isotope Compositions and Temperature in Modern Seafloor Hydrothermal Systems

A comparative study of fluid inclusions, He and hydrocarbons in fluid inclusions trapped in sulfides and S isotopes in sulfides from modern sulfide edifices on the Mid-Atlantic ridge (Rainbow, Logachev, Broken Spur, TAG), East Pacific Rise (EPR 9 N, 21 N) and in the Manus and Lau back-arc basins (Pacific) was carried out. Variations in fluid salinity were found. Methane through butane occur in fluids. R/Ra ratio indicates a contribution of helium from upper mantle and recycled seawater to fluids. The S isotope ratio suggest a mixing of sulfur derived from different sources.