Discovery of an abnormally high-[delta]^sup 34^S barite deposit and a new understanding of global sulfur isotope variation during geological history

The evolution of the global sulfur isotope curve was plotted based on the δ^sup 34^S values of evaporates resultant from oceanic evaporation. In the long period of geological history the δ^sup 34^S values showed obvious peaks for three times during the process of ancient oceans' sulfur isotope evolution, namely the Early Cambrian (+30[per thousand]), the Late Devonian (+25[per thousand]) and the Permian-Triassic transition interval (+17[per thousand]), but the causes of the abnormal rise of sulfur isotopic values during the geological period are still in question. In this paper, 18 samples collected from a large Devonian barite deposit from Zhenning County were analyzed to determine their δ^sup 34^S values, revealing that the 18 samples have very high δ^sup 34^S values (δ^sup 34^S=41.88[per thousand]-+68.39[per thousand]), with an average close to 56.30[per thousand], which are higher than the isotopic values of contemporary sulfates (+17[per thousand]-+25[per thousand]). A comparative analysis was conducted of the emerging of high δ^sup 34^S barite deposits (from Cambrian and Devonian) and the δ^sup 34^S variation curves of the ancient oceans. The results indicate that the time when the obvious peaks of δ^sup 34^S values appeared and the time of massive sedimentation of high δ^sup 34^S barite deposits are very close to each other, which, in our opinion, is not a coincidence. There may exist some correlations between the sulfur isotope evolution of ancient oceans during the diverse periods of geological history and the massive sedimentation of high δ^sup 34^S barite deposits. Therefore, it is inferred that perhaps it was the massive sedimentation of high δ^sup 34^S barites that caused the sharp rise of δ^sup 34^S values in a short period of time.[PUBLICATION ABSTRACT]