Origin of Kupferschiefer mineralization as suggested by coal petrology and organic geochemical studies

Abstract

The Kupferschiefer base metal occurrences of Central Europe have been investigated by a variety of organic geochemical and coal petrology methods to clarify their genesis. Low rank vitrinite anomalies were encountered in the paleogeothermal field of the Kupferschiefer horizon in close proximity to Variscan paleohighs and tectonically severely disturbed basement. Spatially, they are related to the position of well-known base metal occurrences the Kupferschiefer type. In the areas of ore grade mineralization an inorganic oxidation effect of soluble organic material has been recognized. Base metal content and degree of oxidation expressed by a ratio of phenanthrene to the sum of metylphenanthrene (Ph/ΣMePh) increases and then decreases towards the epigenetic Rote Fäule facies. This suggests that ascending, low-temperature and oxidized ore-bearing solutions were responsible for the enrichment of the Kupferschiefer bed. The Kupferschiefer, acting as a geochemical hydrogen-sulphide screen, was a site of the redox type reactions that resulted in base metal reduction (precipitation) and hydrocarbon oxidation within this Upper Permian (Zechstein) bed.