Isotopic Signatures of Deposition and Transformation of Lower Cambrian Saliferous Rocks in the Irkutsk Amphitheater: Communication 1. Sulfur Isotopic Composition

摘要

New isotope data on Lower Cambrian rocks of the Irkutsk amphitheater are reported in three communications. The first communication is devoted to the sulfur isotopic composition, which is most sensitive to postsedimentary geochemical transformations of sulfate rocks in saliferous formations. It is shown that δ~(34)S values in Bel'sk and Zhigalovo boreholes are within 22-35 per thousand. The lowest values are close to the sulfur isotopic composition of a halogenic basin, while the highest values are related to epigenetic sulfate reduction. This process was responsible for the elimination of 100 m of anhydrites from the Lower Cambrian section.