HUMIC-SOURCED ORGANIC-MATTER FROM THE UPPER SILESIAN ZN-PB DEPOSITS (POLAND)

Black, amorphous organic matter from the Upper Silesian Zn-Pb sulphide deposits (northwest of Krakow), hosted in the dolomitized Middle Tria ssic limestones, is a humic substance of unknown origin. In the Pomorz any Mine this organic matter occurs in the interfragmental voids of mi neralized, hydrothermal karst collapse breccias and as discontinuous l ayers and concordant laminae in the mineralized internal sediments tha t fill the pockets in the dissolutional surface beneath collapse brecc ias. Samples of organic matter were studied with reflected light (RLM) and scanning electron (SEM) microscopes, and were also subjected to c hemical analyses, Rock-Eval pyrolysis and gas chromatography. The resu lts obtained indicate that the organic matter has a humic, allochthono us nature and was subjected to migration under oxidizing conditions. P etrologically, the organic matter consists of eugelinite, with a refle ctance (R(r)) of < 0.3%. It is proposed that the organic matter is dop plerite (calcium humate). It precipitated from humic acids, migrating downwards in aqueous solutions and loaded with Ca cations released fro m the surrounding carbonates by ascending, hydrothermal solutions. The probable source of humic acids was highly oxidized, plant-derived org anic matter. The coalified remnants of flora are abundant in various U pper Triassic stratigraphic members overlying the ore deposits. Geolog ical observations indicate that the organic matter and the sulphide or es were both deposited within the karst collapse structures at the sam e time and are genetically related. It is suggested that the organic m atter and humic acids played a critical role in the precipitation of s ulphide ore minerals as reductants of partly oxidized, sulphur- and me tal-bearing, hydrothermal, ascending solutions.