Geochemical characteristics across the oxic/anoxic interface (Rote Fنule front) within the Kupferschiefer of the Lubin-Sieroszowice mining district (SW Poland)

Samples of profiles from Lower Zechstein in the Lubin-Sieroszowice mining district (SW Poland) were collected within and at different distance to the oxidized facies (Rote Fäule), developed within the Zechstein strata around the Zary Pericline. The samples include Kupferschiefer, underlying Weissliegendes sandstone and overlying Zechstein Limestone from Rote Fäule zones, adjacent Cu-mineralized strata, and drill cores from the Pb/Zn-mineralized zone more distant to the Rote Fäule front. The Kupferschiefer samples show differences in ore paragenesis and composition of organic matter, which are accompanied by variations in base metal and trace element contents, and isotope ratios of organic carbon and carbonates. sults from Rock-Eval analyses provide evidence for an oxidative alteration of organic matter in Kupferschiefer samples within and adjacent to the Rote Fäule zones related to base metal mineralization. The extent of this alteration is reflected by differences in the temperature of maximum pyrolysis yield (Tmax), hydrogen and oxygen indices (HI, OI). In contrast to Kupferschiefer from Pb/Zn-mineralized areas, organic matter is characterized by lower hydrogen equivalents, and by higher Tmax values. anges in the isotopic composition of organic carbon and carbonates reflect the alteration of organic matter. Kerogen within, or close to, Rote Fäule zones is enriched in 13C caused by the preferential release of isotopically light organic compounds through progressive degradation of organic matter. The opposite tendency towards lower δ13C values of calcite provides evidence for organic matter remineralization. Isotopic exchange reactions of carbonate with the isotopically distinct oxidizing brines at temperatures between 100 and 120 °C caused decreasing δ18O values of calcite. gional zonation in the Kupferschiefer with respect to sulfide paragenesis and base metal composition in the mines is explained by metal precipitation from oxidizing brines through decreasing Eh conditions during the infiltration of the brines into the reduced Kupferschiefer. Relationships between selected trace elements, organic carbon and sulfur contents, and HI values are consistent with that model of ore formation.