Dedolomityzacja węglanów cechsztyńskich w rejonie Lubina

Abstract

DEDOLOMITIZATION OF THE ZECHSTEIN CARBONATES IN THE REGION OF LUBIN

Summary

Products of dedolomitization, i.e. those of the transformation process of dolomites back into limestones under surface conditions, under the influence of aqueous solutions of calcium sulphate, have been ascertained to occur in the Zechstein carbonates within the Lubin region (SW Poland). The main part of these formations occurs in the upper portion of the Zechstein limestone horizon (Cal), which ranges here from 60 to 80 metres in thickness. Dolomitic limestones, mainly strongly porpus, grey-beige in colour, are the product of this dedolomitization process (Table I, Figs. 3, 4). The fundamental mass of the rocks is built of calcite crystals, pseudomorphically substituting from inside the rhombohedral dolomite crystals (Table II, Figs. 5, 6). Dolomite occurs as politic relicts that stick in the calcite, as well as in the form relict rims round the calcite crystals. The strontium content in these rocks, lower than that in the limestones from the bottom part of the Zechstein limestone (Cal), as well as than its content in the dolomites from the top part of this horizon, is characteristic here (Fig. 2). Products of dedolomitization have also been found to occur in other Zechstein carbonate horizons (Table III, Figs. 7, 8), and even in small carbonate intercalations that occur within the Zechstein sulphate horizons (Table III, Fig. 9). The extent of the dedolomitization processes in the considered has not far been examined in detail. It is known, however, that these processes have developed along the sub-Tertiary outcrops of the Zechstein formations, in the period of the pre-Tertiary erosion.