Origin and significance of early-diagenetic calcite concretions and barite from Silurian black shales in the East European Craton, Poland

The Silurian Pelplin Formation is a part of thick, mud-prone distal fill the Caledonian foredeep, which stretches along western margin East European Craton. consists organic carbon-rich mudstones that have recently been target intensive investigations, as they represent potential source shale gas. host numerous calcite concretions containing authigenic pyrite and barite. Mineralogical and petrographic examination (XRD, optical microscopy, cathodoluminoscopy, SEM-EDS) and stable isotope analyses (δ13Corg, δ13C δ18O carbonates, δ34S barite) were carried out in order to understand diagenetic conditions led to precipitation this carbonate-sulfide-sulfate paragenesis and to see if can enhance understanding sedimentary settings Baltic Lublin basins during Silurian. Barite formed during early diagenesis before concretionary growth due a deceleration sedimentation increased primary productivity. main stages took place yet uncompacted sediments shortly after their deposition sulfate reduction zone. This precompactional cementation preferential preservation original structures, faunal assemblages and early- barite, which mostly lost surrounding burial. These components allowed for reconstruction important paleoenvironmental basins, such depth, proximity detrital orogenic source marine Investigation the concretions also enabled estimation magnitude mechanical compaction calculation of rates. Moreover, it showed biogenic methane was produced at an early-diagenetic stage, whereas thermogenic hydrocarbons migrated through deep