Problem występowania i genezy pirytu w obrębie skał cechsztyńskich monokliny przedsudeckiej

Abstract

THE PROBLEM OF OCCURRENCE AND GENESIS OF PYRITE IN THE ZECHSTEIN ROCKS OF THE FORE-SUDETIC MONOCLINESummaryIn the Lower Zechstein formations of the Fore-Sudetic monocline (Lower Silesia), pyrite is an abundant sulphide. It may be found to occur as spherical concretions built up of idiomorphic crystals called mineralized bacteria. The spherical concretions are approximately 10 or 30 μ in diameter, the size of the individual crystals being from 0.5 to 8 μ (Table I, Fig. 2). At places, these spherules appear in lenticular concretions (Fig.3). The deposits under consideration reveal also single pyrite crystals scattered in rock chaotically, rarely accumulated in the form of irregular concentrations (Table II, Fig. 4). Other form of iron sulphide occurrence in the deposits of Lower Zechstein age is represented by irregular pyrite grains, up to several millimeters in size (Table II, Fig. 5). There is a distinct regularity in the distribution of pyrite within the Lower Zechstein rocks of the Fore-Sudetic monocline (Fig. 1). An increased amount of pyrite is found to appear at certain distance from the occurrence area of the horizon of copper-bearing shale deposited under conditions of an oxidized facies called rote Fäule. In vertical profile this minerals occurs mainly above, frequently also below the main copper mineralization zone. For the most part it appears together with chalcopyrite, galenite and sphalerite, rarely also with bornite and chalcosine (Table III). The spherical form of pyrite has long ago been interpreted as petrified colonies of bacteria (H. Schneiderhöhn, 1923). This opinion was rejected by numerous scientists (C. Schouten, 1946, T. Deans, l948), who determined such a kind of pyrite as the effect of simple precipitation of iron sulphide in a solution or the result of substitution of other bodies, not always of organic provenance. At present, in the light of the studies made by L. G. Love (1957, 1962), L. G. M. Baas Becking and D. Moore (1961), M. Langer (l963) and U. Regnell (l96l), the spherical form of pyrite should be thought to be a result of anaerobe activity. Due to the metabolic processes, the H2S product facilitated the formation of iron sulphide, recrystallized in the early-diagenetic time in the form of pyrite. This opinion is proved by the observations of pyrite within the Lower Zechstein deposits of the Fore-Sudetic monocline (Lower Silesia).