ALBERT

Description: Organic matter (OM) is known to be an important reductant in sediment-hosted base metal deposits like the European Kupferschiefer. However, the precise nature of interactions between OM and hydrothermal fluids are still debated as well as how the interconnected reactions develop over geological timescales. This dataset provides for the first time bulk, compositional and stable isotope data of hydrocarbons, biomarkers and organonitrogen, -sulfur and-oxygen (NSO) compounds for the mineralized Kupferschiefer Spremberg-Graustein field in Eastern Germany based on samples from two drill cores. The study aims to help to better understand the role that organic matter plays during the mineralisation and formation of the sedimentary ore deposit within the Kupferschiefer with a focus on stable hydrogen isotope compositions and NSO compositional data to especially address the origin and to assess the oxidative nature of the brines that caused the mineralization in the Spremberg-Graustein field. The data publication includes bulk, compositional and stable isotope data on inorganic metals and organic matter. The data about metal contents were generated using ICP-MS while those on the organic matter were generated using Rock-Eval pyrolysis, a microscope, a Soxhlet apparatus, medium pressure liquid chromatography (MPLC), gas chromatography with flame ionization (GC-FID) and mass spectrometric detection (GC-MS), gas chromatography isotope ratio mass spectrometry (GC-IRMS) and ultrahigh resolution mass spectrometry (Fourier Transform ion cyclotron resonance mass spectrometry, FT-ICR-MS) with Electrospray ionization (ESI) and Atmospheric pressure photoionization (APPI). The full description of samples, methods and data is given in the following sections.

Description: Organic matter (OM) is known to be an important reductant in many sediment-hosted base metal deposits. However, the precise nature of interactions between OM and hydrothermal fluids are still debated, as well as how the interconnected reactions develop over geological timescales. We investigated the Kupferschiefer mineralization in two drill cores from the Spremberg-Graustein field in Eastern Germany focusing on the inventory of organonitrogen, -sulfur and -oxygen (NSO) compounds, which are most affected by organic-inorganic interactions with mineral surfaces, metals and aqueous fluids. Rather homogeneous deposition of type II marine organic matter, prevailing photic zone euxinia and an early oil window thermal maturity were documented using conventional hydrocarbon analysis. Furthermore, a slight level of hydrothermal alteration was detected in the lower part of drill core 121h/72, in proximity to the epigenetic hematitic alteration zone known as ‘Rote Fäule’: A minor loss of extractable organic matter and especially long-chain n-alkanes was accompanied by significant enrichment in oxygenated compounds and increased molecular oxygen content detected by FT–ICR–MS. A strong enrichment of deuterium was observed in the n-alkanes (up to -36‰) and isoprenoids (up to -20‰) indicate that hydrogen exchange with an evaporitic fluid occured in the Spremberg Kupferschiefer over geological timescales at maximum temperatures not exceeding 110 °C. We therefore conclude that FT–ICR–MS combined with the stable hydrogen isotope composition can provide valuable information about interaction time scales and the origin of mineralizing hydrothermal fluids.