Pochodzenie siarczanów w niektórych polskich wodach podziemnych w świetle oznaczeń δ34S

Abstract

THE ORIGIN OF SULPHATES OF SOME POLISH GROUND WATERS IN THE LIGHT OF δ34S DETERMINATIONS Summary The present paper deals with the results of measurements of sulphur isotopic composition of sulphates from Polish mineral waters. The determinations have been performed in foreign laboratories thanks to the kindness of dr H. Nielsen (Zentrallaboratorium für Geochemie der Isotope - Göttingen) and dr V. Šmejkal (Ustředni Ustav Geologicky - Praha). The results of measurements in samples 1-10 taken from the Mesozoic of the Kujawy-Pomorze swell confirm the author's hypothesis concerning the partially relict character of brines found in these sediments. The δ34S of sulphates in waters from the Keuper show their genetic connection with the evaporating sedimentary basin of this period. The results obtained from waters found in Liassic and Dogger deposits may evidence syndiagenetic processes of sulphate reduction, which took place in these deposits. Waters from the Upper Cretaceous of the North-East margin of the Miechów trough (samples 11-17) contain sulphates derived mainly from the Tortonian gypsum-bearing series. These sulphates are enriched in 34S as a result of reduction processes due to sulphate-reducing bacteria. Higher values of δ34S in water from Upper Jurassic containing not much sulphate seem to testify the ascension of Jurassic or older relict brines in which a part of sulphate has been reduced during early phases of diagenesis.