The Kupferschiefer is a copper-, polymetallic-, hydrocarbon-bearing black shale of the lowermost Zechstein Group of Permo-Triassic age (252 Ma) in Germany and Poland. It is usually 1 m thick and underlies 600,000 km2, extending from Great Britain to Belarus for a distance of over 1500 km. At a district scale, copper has been mined for over 800 years since its discovery circa 1200 A.D. Mineralogical, chemical, and geological analyses of the combined Zechstein-Kupferschiefer show strong chemical and paragenetic relationships between the Zechstein salines, Kupferschiefer, and Weissliegend sandstones that lead to a broader, more unified, genetically linked model related to deep-sourced, hot, hydrothermal, mud-brine volcanism. The overall Zechstein-Kupferschiefer chemical stratigraphy suggests density-/composition-driven fractionation of deep-sourced, metal-rich, alkali-rich, silica-aluminum-rich, halogen-rich, high-density brines. The ultimate brine source is interpreted to be serpentinized peridotite in the lower crust near the Moho transition to the mantle. Dehydration of the serpentinite source to talc (steatization) by mantle heat during failed, intra-continental rifting of the Pangaea supercontinent at the end of Permian time released vast amounts of element-laden, high-density brines into deep-basement fractures, depositing them into and above the Rotliegend Sandstone in the shallow Kupferschiefer Sea, which is analogous to the modern northern Caspian Sea.
Mud volcanism can provide a mechanism for hot hydrothermal muds and brines to ascend from dehydrated, serpentinized peridotite at the mantle-crust contact (Moho). Such mud volcanism may have occurred on a regional scale across northern Europe when high to low density brines erupted as metalliferous, hot, hydrothermal, hydrocarbon-rich mud slurries. These mud-brines were delivered to the Permo-Triassic unconformity in a shallow Zechstein sea during the Pangea breakup through a series of deep-seated conduits that connected the serpentosphere to the Zechstein unconformity. A three-stage, hot, hydrothermal, mud volcanic model can explain the Kupferschiefer-Zechstein-Rote Fäule sequence of polymetallic, hydrocarbon, and saline mineralization as a consequence of a three-stage, dehydration sequence of deep serpentospheric uppermost mantle. Dehydration products of mantle-heated serpentinite were produced in three sequential stages: (1) lizardite to antigorite, (2) antigorite to chlorite-harzburgite, and (3) chlorite-harzburgite to garnet peridotite. The dehydration of serpentine correlates to three stages of Zechstein-Kupferschiefer mineralization: (1) Weissliegend-Kupferschiefer Cu-Ag-carbonaceous shale and silica sand deposits, to (2) Zechstein saline deposits, to (3) Rote Fäule hematite-Au-REE-U cross-cutting metallization.
