New perspective on trace element (Re, Ge, Ag) hosts in the Cu-Ag Kupferschiefer deposit, Poland: Insight from a LA-ICP-MS trace element study

Abstract

The Kupferschiefer deposit in SW Poland provides an opportunity to study an ore system where besides factors such as temperature, salinity and pH, redox conditions play a major role in controlling trace element incorporation in sulphides. Chalcocite, djurleite, bornite, chalcopyrite, sphalerite, covellite and pyrite from the Cu-Ag deposit in the Lubin-Sieroszowice district were analysed with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to study the distribution of trace elements and to identify the main carriers of by-products such as silver and rhenium. Trace element anomalies are not only associated with certain minerals but also linked to specific mineralization styles. Chalcopyrite in epigenetic veins has significantly higher content of Ge, As and Sb while sulphides adjacent to hematitic “red spots” are enriched in redox sensitive elements: djurleite is enriched in V, Se, Re, Au, Hg and Tl, chalcopyrite in V, Se, Hg and Tl, and pyrite in Tl in comparison with bulk Cu-Ag mineralization. Elevated and substantially more variable data for V, Mn, Ni, Co, Ga, Mo, Sn in shale hosted sulphides can be attributed to submicron inclusions of Kupferschiefer silicate matrix which might skew low concentration values even if careful petrographic observations and precise spot selection are applied. Silver concentrations form a linear pattern from chalcocite/djurleite > bornite > chalcopyrite > sphalerite. Silver distribution in the deposit on a broad scale could be linked to the general Fe3+-Cu-Pb-Zn-Fe2+ zonation as well as mineral sequence (hematite-chalcocite-bornite-chalcopyrite-galena-sphalerite-pyrite) observed in the majority of sediment hosted stratiform copper deposits. Epigenetic sulphide-calcite veins associated with local faults and tectonic zones contain chalcopyrite exceptionally rich in germanium (up to 4806 μg/g of Ge) suggesting that the potential of Kupferschiefer Cu-Ag ores in terms of Ge grades and resources could be underestimated. The majority of analysed sulphides do not contain rhenium above detection limits (0.1 μg/g Re) with measurable quantities found almost exclusively in djurleite (up to 3.9 μg/g Re). This indicates that copper sulphides, in particular djurleite, could be a preferred host and an important carrier of rhenium in the deposit.