The Kupferschiefer; an overview with an appraisal of the different types of mineralization

Abstract

The Kupferschiefer, a thin (<4 m) bed of marine bituminous marl of Upper Permian (Zechstein) age, occurs over a large area of north-central Europe and has, in certain areas, been exploited for silver and some base metals, notably copper, since medieval times. It has been regarded as the type example of a shale-hosted, strata-bound sulfide deposit and theories regarding the origins of Kupferschiefer mineralization have exerted considerable influence on theories of ore genesis. The Kupferschiefer sediments were deposited following a rapid marine transgression over an area that had been subject to a very long period of arid to semi-arid conditions. In many areas the Kupferschiefer overlies red-bed sediments (Rotliegende), but in others it overlies Carboniferous sandstones and marls or the bleached and reworked equivalents of earlier rocks (Grauliegende and Weissliegende). Within the Kupferschiefer, lithologieal variations can be related to detailed paleogeography. Overall a euxinie, sapropelie facies predominates, but changes occur in the region of paleohighs where more carbonate and elastic-rich facies are developed. Strong evidence exists for the development of chemical stratification in the Zeehstein sea (from which the Kupfersehiefer was deposited) with oxidizing conditions in the upper part and reducing conditions in the lower part. Everywhere the Kupferschiefer grades upward into overlying dolomitie limestones. Although large areas of the Kupfersehiefer contain only average concentrations of base and precious metals compared to other shales and marls, in certain areas the concentrations reach ore grade. Historically, the Mansfeld district (SE Harz Mountains) was important for copper and silver mining, but at present-day mining is undertaken only in the Spremberg-Weisswasser area (East Germany) and in Lower Silesia (Poland). The ores in such regions contain sulfides of Cu, Pb, and Zn and may be enriched in a variety of other elements, notably V, Mo, U, Ag, As, Sb, Bi, and Se; Cd, T1, Au, Re, and the platinum-group metals are also reported; lateral and vertical zoning of Cu, Pb, and Zn may be observed; and in some areas, a reddening of the rocks adjacent to ores (Rote Fiiule facies) is a useful exploration guide. The Kupfersehiefer in Poland, in two contrasting regions in Germany (the Lower Rhine basin and the Hessian depression) and in England (where it is termed the Marl Slate) are compared and provide evidence for four types of mineralization. The first (and oldest) is a weakly mineralized type exemplified by the English Marl Slate. Average base metal content of this type is • 100 ppm. Detailed mineralogieal, geochemical, and isotopic studies indicate that the mineralization is synsedimentary; these studies have enabled a model to be developed in which precipitation of the various mineral phases can be related to stratification of the early Zeehstein sea and oscillations in water and oxie-anoxie boundary levels. The second is an average mineralization involving base metal content at the 2,000-ppm level. In th...

A multistage origin for Kupferschiefer mineralization

“…Several paragenetic stages are commonly described for the whole region, each related to distinct and separate phases of mineralization (e.g., Michalik and Sawlowicz, 2001); this paragenesis also includes several stages of hematite formation in the Rote Fäule (Jung and Knitzschke, 1976;. Many of the models for Kupferschiefer mineralization stress a progressive development of the mineralizing system, from synsedimentary processes to early and then late diagenesis, to later replacement (e.g., Vaughan et al, 1989;Sun and Puttmann, 1997). Additionally, dilatant, crosscutting sulphide bearing veins exist (e.g., Salski 1977;Jowett, 1987) but although definitely later, their significance in terms of the overall mineralization process is unclear.…”

“…Additionally, dilatant, crosscutting sulphide bearing veins exist (e.g., Salski 1977;Jowett, 1987) but although definitely later, their significance in terms of the overall mineralization process is unclear. Thus, proposed models for the mineralization have included descriptive terms such as 'polycyclic' (Nawrocki, 2000), 'episodic', a 'continuum' (Vaughan et al, 1989), 'multistage and long term' (Michalik and Sawlowicz, 2001), and 'extended over tens of millions of years' (Bechtel et al, 2000).…”

“…of Jowett, 1986, or the 20 m.y. of Vaughan et al, 1989). Any theory on ore genesis for the Kupferschiefer must take this extended age range into account, but also must accommodate the entire range of potential processes from diagenesis to epigenesis.…”

“…The geological and mineralogical characteristics of the Kupferschiefer have been extensively studied and thorough descriptions of the geology are to be found in Vaughan et al (1989), Oszczepalski (1989Oszczepalski ( ,1999, , Borg et al (2012), and Zientek et al (2015).…”

The Value of Adaptive Mineral Processing based on spatially varying Ore Fabric Parameters

“…The Permian Kupferschiefer is a thin unit of marine bituminous marl that conformably overlies sandstones of the Pre-Zechstein and grades upward into dolomitic limestones (Speczik et al, 1995;Vaughan et al, 1989). It occurs from England through the Netherlands, Germany into Poland, the Baltic states, and Belarus and covers an area of approximately 600 000 km² (Kopp et al, 2008).…”