Changes in the sulphus isotope ratio in the calcium sulphates of the earth crust

The article deals with changes in the ratio of sulphur isotopes 32S and 34S, occurring in sedimentary calcium sulphates, formed in the course of geological history from the earliest Pre-Cambrian to the Quaternary. The author amplifies on the problem raised by W.T. Holser and I.R. Kaplan (1966) and finds that changes in the 34S/32S ratio in evaporites reflect, on the one hand, a selective precipitation of sulphur - from the point of view of isotope content - and on the other hand, endogenic processes in the course of which isotope content increases to 34S. The author discusses the sulphur isotope ratio in different environments. He finds that there is a continuous exchange of sulphur between the earth crust, water and atmosphere. In the course of this exchange sulphur passes from one kind of environment to another and thus goes through different stages of oxidization and reduction. In this process of transition a selection of isotopes takes place: in the course of reduction sulphur becomes poorer in the heavy isotope and, vice versa, it is enriched with this isotope during oxidization. The author presents also the results of studies on evaporites (gypsum and anhydrite) from Poland. He finds that the values of 34S in these deposits are characterized by considerable differentiation. He emphasizes the fact that almost all of these values are contained within intervals established for the particular geological periods by W.T. Holser and I.R. Kaplan (1966). (author)