GEOMETALLURGY OF THE SEDIMENT-HOSTED KUPFERSCHIEFER CU-AG-AU DEPOSITS AND THE GEOLOGICAL RELATION TO THE MID-EUROPEAN CRYSTALLINE ZONE

Sediments covered by Lower Permian Kupferschiefer extend over an area of more than 600,000 km² from the UK to East Poland. However, the sediment-hosted bulk base and precious metal enrichments and mineable deposits are only known from the Central European Copper Belt, extending from the Rhön-Richelsdorf region in the west of Germany to the Konrad and Lubin-Rudna region in central Poland, charcterized by a systematic sequence of lateral and vertical distribution of metals.

The bituminous calcareous Kupferschiefer shale that is at the base of a massive marine evaporitic sequence of the Zechstein period. The Zechstein sea changed the paleography by transgressing a desert-like red epicontinental basin. The Kupferschiefer strata is a contributing and essential component for the formation of the enriched Cu-Ag-Au deposits. The geometallurgical composition of the enrichment zones has metallic and non-metallic components. A complex assemblage of aromatic organic components of up to 16 % vol. content is indicative of the enrichment zones. For the metallic components, the systematic sequence of the zones are: hematitic “Rote Fäule” with mostly sharp borders to the high-grade Cu-Ag-Au mineralization facies, followed outwardly by the Pb-, Zn-, and Pyrite dominated belts. The high-grade Cu-Ag-Au deposits are of economic importance.

Although the mineralization is hosted by a variety of sediments it is essential to observe that the oxidized hematitic “Rote Fäule” zone, as well as the economically important Cu-Ag-Au zone and the following Pb- and Zn- belts are crosscutting the sedimentary strata over large distances. The mineralized bodies are subhorizonal, tabular and belt-like. Geochemically and mineralogically, the research suggests a multiphase mineralization resulting in multi-stage base and precious metal enrichment.

New research by the authors indicate that Au mineralization in the Kupferschiefer deposits as well as in adjacent vein type occurrences outline the economically interesting European base and precious metal district. The arched Central European Copper Belt mirrors the Mid-European Crystalline Zone MECZ. The line of deposits at the southern rim of the MECZ marks the boundary area of the Saxo-Thuringicum with the Rhenoherzynicum and represents a major subduction zone of the European Variscan.