What is kupferschiefer in geology ?

Kupferschiefer : definition

The deposits of the "kupferschiefer" type (copper schist) belong to the vast category of stratoid deposits in detrital sedimentary rocks. These deposits are closely related to their sedimentary host rock and generally present an appearance consistent with the latter. The "kupferschiefer" type deposits are composed of sulphides and oxides disseminated along an oxidation-reduction front within transgressive marine sequences with evaporites, deposited under anoxic conditions, overcoming continental red layers. The thickness of these formations varies from 30 cm to 2 m. Mineralizing fluids are probably brines derived from evaporites that leach these red layers to extract copper and other metals.

Very important deposits of this type are known in Germany and Poland (Permian deposits of the Zechstein Sea, Lubin mine), and in Central Africa (Congo, Zambia) where they constitute the deposits of the copper belt.

Copper is the most important metal there, but silver, cobalt, sometimes lead and zinc are recovered as by-products. The sulphides that make up the mineralization appear in a series of mineral zones : hematite - cuprite and tenorite - native copper - chalcocite - bornite - chalcopyrite - galena - sphalerite or pyrite.