The secondary oxidation of organic material and its influence on Kupferschiefer mineralization of southwest Poland

Abstract

Organic geochemical analyses were applied to a series of sixteen extracts obtained from Kupferschiefer samples collected in the Konrad and Rudna mines, southwest Poland. Results show that the content of saturated hydrocarbons in the extracts is reduced relative to the content of aromatic and heteroaromatic compounds. The extent of this effect depends on the intensity of secondary oxidation processes which affected the Kupferschiefer zone. Compounds like phenanthrene, dibenzofuran, dibenzothiophene and biphenyl are enriched by secondary oxidation processes in this sulphide-rich sedimentary rock. The ratio of phenanthrene to the sum of methylphenanthrenes provides a measure of the degree of oxidation in the investigated samples. The most oxidized zone is at the base of the Kupferschiefer. The degree of oxidation decreases upwards. It is envisaged that ascending solutions with an oxidizing, high metal content migrated into the Kupferschiefer which was initially deposited under reducing conditions. Thereby, redox reactions between H-rich organic matter and oxidizing metal solutions occurred and resulted in the secondary enrichment of metals in the Kupferschiefer zone.