Investigation on Sulfur Isotopic Composition and Its Geological Genesis of Marine Triassic Anhydrite in Sichuan Basin

By the comparative analysis on sulfur isotopes(i.e,δ34S)with the characteristics of the marine Triassic evaporite in Sichuan Basin,for the Triassic δ34S with the features of abnormal high values and presents gradually lighter from day to night in the region,combined the background of its deposition geological physical-chemical conditions,particularly the study on isotope fractionation,geological and geochemical characteristics under complex conditions,δ34S abnormal high values of the anhydrite and the geological causes of its gradual poverty with evaporation are discussed,which aimed at providing an important basis for the reconstruction of ancient environment,the division and comparison of stratum.It is shown that δ34S abnormal high values of the anhydrite mainly due to the isotope fractionating effects in a closed environment and when sulfate was reduced by bacteria.