Stront w utworach węglanowych cechsztynu Polski

Abstract

STRONTIUM IN ZECHSTEIN CARBONATE DEPOSITS OF POLANDSummaryThe purpose of the present work was to determine strontium contents and to explain the concentration conditions of this chemical element in the Zechstein carbonate deposits of Poland. Data concerning strontium distribution in these deposits were based on the results obtained from analyses of about 450 samples taken from 20 bore holes situated within the marginal zones of the Zechstein basin (Fig. 1). Samples analysed for this study were taken mainly in the northern and north-western areas of Poland. The carbonate deposits of Zechstein age are, for the most part, represented by dolomite and dolomite-limestone formations. To explain the activity of the strontium migration during the diagenetic processes of carbonate deposits, particular attention was paid to the profiles which were represented by both dolomite and limestone deposits. The results of analyses, mean contents and dispersion of concentration are shown in Fig. 3. The mean contents of strontium amount, taken generally for the Zechstein carbonate deposits of Poland to 0.132%. The examinations have also demonstrated that the maximum concentration of strontium can be observed to occur in the Zechstein marly-carbonate series, and in the carbonate rocks impregnated with anhydrite or gypsum. These data suggest that the distribution of strontium in these deposits depends upon the contents of calcium sulphate, and that the concentration is of secondary nature. In cross sections, where both limestone and dolomite deposits appear, an inverse correlation has been observed to occur between the contents of strontium and magnesium, i.e. a decrease in concentration of strontium with the increase in magnesium content. This proves a diminution of strontium, probably due to an easy removal of this chemical element from the carbonate rocks during the process of dolomitization. Dolomite deposits, found in the north-western areas of Poland, are distinguished y a relatively high strontium concentration that amounts here to 0.130%. Most probably, it is of epigenetic character, and may be related to the presence of celestine. It has also been observed that the concentration of strontium in the Zechstein carbonate deposits depends more considerably upon the conditions of the environment, than upon the nature of deposits. The results obtained have proved that strontium, a geochemical index, is highly valuable in the reconstruction of the diagenesis of carbonate deposits.