Geochemical and Mineralogical Characteristics of Triassic Dolomites from Upper Silesia, Poland

A detailed description of carbonate minerals of Triassic dolomites with different magnesium contents is presented in this article. Tests were carried out to determine geochemical and mineralogical characteristics. The following carbonate phases were identified: low-Mg calcite, high-Mg calcite, proto-dolomite, ordered dolomite, and huntite. The methods used were microscopic description, X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron probe microanalysis (EMPA). Samples were collected from the Tarnowice Formation, which is the lower part of the profile of Upper Muschelkalk. On the basis of the obtained results, the chemical formulae of carbonate phases were calculated. The results indicate that Mg in low-Mg calcite ranges from 0.6 to 1.2% and in high-Mg calcite from 7.47 to 10.41%. In protodolomite, it ranges from 10.96 to 11.78%. In ordered dolomite, the Mg content is 13.18% on a stoichiometric basis. Due to the reduced Mg content in the identified huntite (in the range of 13.62% to 17.76), this carbonate phase is considered de-huntite.