Origin of cone-in-cone calcite veins during calcitization of dolomites and their subsequent diagenesis: A case study from the Gogolin Formation (Middle Triassic), SW Poland

摘要: Abstract Although bedding-parallel cone-in-cone structure calcite veins are present in the Middle Triassic Gogolin Formation Opole Silesia, their occurrence is limited to Emilowka Cellular Limestone Member. Marly limestones (dedolomites) consisting of pseudospar host rocks. The veins, which up 3 mm high and 30 cm long, built densely packed cone columns, with individual cones 0.7 mm 0.6 mm wide at bases, vertex angle values ranging from 30° 50°. microfractured, adjacent vertically shifted oblique planes. exceptionally small consist fibres 0.15 mm high. low-magnesium non-ferroan calcite, characterized by low δ18O − 6.8‰ − 7.4‰, δ13C − 2.9‰ − 4.5‰ vs. PDB. These isotopic similar those obtained rocks (δ18O − 3.2‰ − 3.6‰ PDB) they strongly depleted comparison other carbonate particles Formation. only formed one lithostratigraphic member, suggesting that origin related processes acted locally. There two unique Member alone underwent: early diagenetic evaporitic dolomitization lime mud sabkha environment, subsequent calcitization dolomite. Dolomitization led sediment cohesion loss, porosity increase initial horizontal laminae separation as a result transformation calcium dolomite within anisotropic deposits. Similar geochemical parameters vein rock evidence vein-filling precipitation was contemporary dedolomitization. Geochemical data combined sedimentological research burial history show meteoric-derived waters saturated respect source calcite. Dedolomitization may have taken place Norian/Early Jurassic Late when study area became eroded land, local paleoaquifer conducting waters. Solid inclusions detached calcitized nodules, force crystallization main factor responsible for widening. Vertical shifts cones, remnants primary fibrous crystals, well justify application Tarr's theory interpreting secondary veins. timing particular conditions required develop uncertain.