Strefa przejściowa w utworach węglanowych triasu obszaru Olkusza

Abstract

TRANSITIONAL ZONE IN THE CARBONATE TRIASSIC OF THE OLKUSZ AREASummaryThe zone of interfingering of dolomites and limestones in the carbonate deposits of the Silesian-Cracow Triassic, delineating the Silesian-Cracow ore basin, was named transitional zone in 1955. Along with progress in geological prospecting the, course of that zone was delineated more precisely. Figures 1 and 2 show reconstructions of the course of that zone from different times. The analysis carried out by the present authors was aimed at recognition of the nature of that transitional zone; it covered core material from about 300 boreholes. The results obtained were presented in the form of lithological-metallogenic maps made for the following horizons: a – Gogolin beds and their dolomite equivalents; b - the equivalents of the Gorażdże beds; c – the equivalents of the Terebratula beds; and d – the equivalents of the Karchowice beds. Figures 3a–3d show the position of the dolomite-limestone boundary in approximately in the middle of these horizons, and Figure 4 – changes 1n the position of the boundary. The analysis has shown that the dolomite-limestone boundary generally runs oblique to lithostratigraphical horizons. The change in lithology may be traced at small distances of the order of some hundred meters. The horizontal extent of dolomites is the smallest in the lower Gogolin beds and the greatest in the uppermost Karchowice beds. The ores occur in a few horizons, mostly in dolomites, being confined to a belt 2.5–3 km wide, adjoining or situated within the transitional zone. The results obtained call for a modification of the current views on the structure and boundaries of the ore basin, as well as on possibilities and directions in prospecting for Zn and Pb ores both within and outside of hitherto assumed boundaries of the ore basin.