Kupferschiefer - Type Mineralization and Geodynamic Evolution of the Polish Zechstein Basin

During the past few decades diverse geological data (mineralogic, petrographic, geochemical, paleomagnetic) have suggested that ascending, oxidizing Rotliegend-brines may have been involved in post-depositional accumulation of copper and silver in the Kupferschiefer of Central Europe. We and others have hypothesized that sulfide precipitation took place by participation of the organic matter of the Kupferschiefer through thermochemical sulfate reduction. The results of recently published stable isotope analyses of clay Minerals (illite) and carbonate from the Kupferschiefer shale argue for increasing extent of isotopic exchange reaction with the ore-bearing solutions with decreasing distance to the copper mineralized zones. All these data in summary indicate that alteration of organic matter, metal sulfide precipitation and isotopic reequilibration are the results of fluid-rock interaction, due to enhanced fluid activity in areas which are related to morphological and tectonic structures in the underground. We will test these hypotheses through the combined use of petrographic, geochemical and stable (0, H, C) isotope analyses of ore minerals, clays, carbonates and the organic matter in Kupferschiefer samples throughout the Polish Zechstein basin. Also our approach will make use of organic geochemical methods in order to evaluate the origin of organic matter, the sedimentary environment" the rank of the Kupferschiefer as well as post-depositional alteration. XRD and geochemical methods for characterizing the clay mineralogy, illite polytypism and illite crystallinity will be applied to the collected samples. In combination with informations about basin dynamics in the Polish Zechstein basin. these results will provide evidence about possible zones of enhanced heat flow and fluid activity in relation to the known morphological and tectonic structures in the basement. In addition" structure- controlled (vein-type) mineralization inside the Kupferschiefer-ore deposits will be investigated by use of fluid inclusion and stable isotope analyses. We plan to characterize fluid inclusions inside the gangue minerals by heating-freezing stage, chemical (ion chromatography, AAS) and stable isotope analyses. It can be expected that the results will provide informations about the composition, origin and evolution of the fluids responsible for the so-called "Rücken"-type (epigenetic) Mineralization. We anticipate that the results of this study will address fundamental questions regarding the timing and mechanism of ore formation inside the Kupferschiefer with respect to the geodynamic evolution and fluid activity inside the Polish Zechstein basin.