Sulphur isotopes in anhydrites from Badenian (Middle Miocene) salts of Hrynivka area (Ukrainian Carpathian Foredeep)

Abstract

Ten new determinations of the stable sulphur isotope content of anhydrite from Badenian rock salt in the Hrynivka 525 borehole (Ukrainian Carpathian Foredeep) show that δ³⁴S values in anhydrite range from +20.2 to +22.7‰ and the average value of δ³⁴S is +21.4 ± 0.3‰. Those values are similar to those of the Neogene marine sulphates. Comparison to other geochemical data (chemical composition of the brine contained in fluid inclusions and the bromine content in halite) suggests that the Badenian Carpathian Foredeep evaporite basin was supplied predominately by seawater solutes where, at different stages of salt accumulation, the influence of continental waters with lighter isotopic compositions of dissolved sulphate was important. The isotopic composition of sulphur (δ ³⁴S) of Badenian seawater, calculated on the basis of sixty analyses of anhydrite related to halite of the Carpathian Region, is approximately +20.3‰, this value being similar to the sulphur isotopic composition of present-day seawater. The δ ³⁴S value for Badenian seawater may have been slightly higher if we consider potential changes of the brine composition of salt-bearing basins caused by inflow of continental waters enriched in light ³²S isotopes.