DIAGENEZA PIASKOWCÓW KARBONU GÓRNEGO WYSTĘPUJĄCYCH NA POGRANICZU ROWU LUBELSKIEGO I BLOKU WARSZAWSKIEGO

Abstract

DIAGENESIS OF THE UPPER CARBONIFEROUS SANDSTONES OCCURING AT THE BORDER OF THE LUBLIN TROUGH AND THE WARSAW BLOCKAbstract. The main components of cements of the Upper Carboniferous sandstones from the northwestern part of the Lublin Trough and the Warsaw Block are represented by detrital clay minerals and authigenic minerals such as quartz, kaolinite and carbonates. Authigenic illite, authigenic chlorite, iron hydroxides and hematite also locally occur in considerable amounts. Sulphates and pyrite represent a small percentage of the cement. Compaction and cementation were the major diagenetic processes that affected the sandstones studied. These processes reduced the primary porosity of sandstones by about 41 and 36% on the average, respectively. Another important diagenetic process which influenced the sandstone porosity was dissolution. It has resulted in the formation of secondary porosity (up to 7% at a maximum). Diagenetic history of the Upper Carboniferous sandstones includes two stages: eo- and mesodiagenesis, the suggested boundary of which corresponds to temperatures of about 50 degrees of Celsius. The pore water isotopic composition of oxygen gradually changed through time towards higher 18O values, and at the final stage of diagenesis it returned to a flower value. The Carboniferous deposits underwent diagenesis at a maximum temperature of approximately 120 degrees of Celsius.