Metal accumulation during and after deposition of the Kupferschiefer from the Sangerhausen Basin, Germany

摘要: Abstract A densely sampled profile (58 cm in thickness) composed of 13 samples the Kupferschiefer and overlying Zechstein carbonates from Sangerhausen Basin, Germany has been analysed by various geochemical microscopic methods order to clarify mechanism base metal accumulation. In this location, is only slightly influenced hematite-bearing, oxidized fluids called Rote Faule . The determination facies-dependent parameters along indicates that Basin was largely deposited a marine environment; at beginning sedimentation did euxinic conditions prevail. bottom part significantly enriched trace elements such as Cu, Ph, Zn, As, Co, Ag U. Cu concentration amounts 19.88 wt.%. Post-depositional oxidation organic matter observed transition zone between conglomerate indicating influence ascending, oxidizing brines. Microscopic analyses show Fe sulfides form framboidal textures; minerals are present total preferentially fractures patchy structures chalcocite, chalcopyrite bornite. highly mineralized section, associated with pyrobitumen, sparry calcite arsenopyrite. Results maturation studies suggest maximum temperature affecting approximately 130°C. 3-step-process accumulation proposed. During deposition sediment, pyrite precursors were precipitated bacterial SO 4 2− reduction (BSR). diagenesis replaced mixed Cu/Fe chalcocite (PR). section very high contents (> 8%) reduced sulfur Fe-sulfides not sufficient for precipitation other metals ascending solutions. profile, thermochemical (TSR) occurred after replacement indicated presence pyrobitumen calcite.