Carbonate phases rich in magnesium in the Triassic limestones of the eastern part of the Germanic Basin

Abstract

This article presents the results of the studies of Triassic carbonate rock samples taken from the area of the Polish part of the Germanic Basin. The task of the study was the identification of carbonate phases with magnesium: a low-Mg calcite, a high-Mg calcite, a dolomite and a huntite in samples collected from the formations which build the profile of the Lower Muschelkalk in the Polish part of the Germanic Basin. The formations are named Gogolin Beds, Górażdże Beds, Dziewkowice Beds and Karchowice Beds. The mineral phases were described on the basis of the results of the following researches: microscopic analysis, X-ray diffraction, FTIR spectrometry and microprobe measurements. Low-Mg calcite which dominates in the limestones can be demonstrated as follows: (Ca1.00–0.98,Mg0–0.02). In some samples, there is also a higher quantity of dolomite and lower amount of high-Mg calcite. The chemical formula of high-Mg calcite of Gogolin limestones can be demonstrated as Ca0.9Mg0.1CO3, whereas in high-Mg calcite of Górażdże limestones the relation assumes the form of (Ca0.92–0.90,Mg0.08–0.10)CO3. The chemical formula of high-magnesium calcite of Dziewkowice limestones is (Ca0.77–0.60,Mg0.23–0.40)CO3 and that of Karchowice limestones is (Ca0.73–0.68,Mg0.27–0.32)CO3. Moreover, dolomite and huntite were identified in some samples. The content of Ca and Mg in dolomite is [Ca0.53–0.51,Mg0.47–0.49CO3] and in huntite [Ca0.48–0.40,Mg0.52–0.60CO3]. The results of researches extend the data connected with mineral phases which build Triassic carbonate rocks of the Germanic Basin. These sediments also occur in other countries of Europe, so that the data can be compared with information connected with the mineral composition of Triassic carbonate rocks situated in other places in the world.