Mineralizacja polimetaliczna spągowych osadów cechsztynu w rejonie Węglińca - Żar

Abstract

W rejonie Węglińca - Żar stwierdzono występowanie spągowych osadów cechsztynu w facji redukcyjnej i utlenionej. Wyróżniono typy genetyczne skał oraz określono związek mineralizacji z paleogeografią weny i z określonymi mikrofacjami i środowiskami fizykochemicznymi. Stwierdzono występowanie margli cynkonośnych oraz podano wstępną interpretację środowiska powstania tego typu osadów.POLYMETALLIC MINERALIZATION OF BASAL ZECHSTEIN ROCKS IN THE WĘGLINIEC - ŻARY AREAIn basal Werra sections of the western part of the North-Sudetic Depression and southern part of the Żary Pericline (Fig. 1), the lithostratigraphic subdivision of which was given elsewhere (S. Oszczepalski, 1978), the following microfacies were differentiated: sandstones, marls, clay pelmicrites, clay micrites and micrites laminated with terrigenic material, micrites and sparites (Fig. 3).During the first phase of the Zechstein sedimentation, the microfacies development of sediments and the differentiation in geochemical facies and polymetallic mineralization has been determined by paleorelief of sedimentary reservoir floor. The Iłowa morphological treshold (J. Krason, 1964) was the main paleogeographic element in this area. A Zechstein Limestone barrier, corresponding to the oxidated zone (Fig. 1, see A Rydzewski, 1978), originated at that treshold From the beginning of the Werra, this barrier zone has· been separating nearshore zone of the North-Sudetic Depression and fore-barrier zone of the Żary Pericline.Microfacies features of carbonate Werra deposits from the Węgliniec area (Figs. I, 3), the wealth of algal structures (Table I, Figs. 6, 7, Table III, fig. 16), the presence of the Nodosaria-Agathammina assemblage as well as sulfides and dolomite show that these deposits have been originating in shallow-water lagoons, under the conditions eX low hydrodynamic regime and steadily increasing salinity of marine water (see T.M. Peryt, 1978a).The studied mineralization is related to bituminous rocks and it is characterized by predominance of sphalerite and pyrite on galena and copper sulfides, the wealth of marcasite, the bulk a sulfides dispersed throughout the rock, and marked traces of diagenetic and hydrogenetic processes. Vertical zonality in distribution of ore minerals is marked by the presence of chalcopyrite-pyrite-marcasite paragenesis in sandstones, the sphalerite-chalcopyrite-galena in marls, and the pyrite in overlaying rocks (Fig. 4). The drillings made in southern part of the Żary Pericline showed that mineralization of the pyrite-marcasite type is mainly related to tectonic and diagenetic structures.Zinc-bearing marls represent reducing facies, typical of Werra lagoonal zones fairly distant from the area of oxidated facies. High content of bituminous matter, structural-textural features of dispersed ore minerals and environmental features show that these sulfides originated in sedimentary environment characterized by high salinity of marine water, high pH and low Eh (Fig. 5), that is under conditions unfavourable for precipitation of copper sulfides (C. Harańczyk, 1972; J. Rentzsch, 1974; W. Jung, G. Knitzschke, 1976).