Lower carboniferous fractured carbonates of the Campine Basin (NE-Belgium) as potential geothermal reservoir: Age and origin of open carbonate veins

Within the Lower Carboniferous limestones in boreholes of Poederlee, Heibaart and Turnhout (Campine Basin, NE-Belgium), open veins partially cemented by calcite dolomite are considered important with regard to geothermal reservoir potential these limestones. Based on a detailed petrographic analysis, stable carbon oxygen as well clumped ?47 isotope analysis U/Pb age dating, formation conditions have been reconstructed were placed geodynamic evolution sedimentary basin. All host rocks recrystallized, carbonate vein cements often possess similar depleted ?18OPDB signature their recrystallized rock. The latter thus indicates cement precipitation was likely rock-buffered. ?13C rock displays marine signature, while two isotopic clusters can be differentiated. first cluster groups cleavage twins, characterized slightly moderately ?13C, reflecting mixture derived from organic matter. This group typically occurs microbially dominated Poederlee buildups characterised on-lapping organic-rich Namurian black shales. One formed at 216 ± 6 °C, indicating that it crystallised during Sudetic – Asturian deformation stage late age, others between 110 130 they could burial or after uplift. second may, but do not, contain twins. They show host-rock buffered signatures. These Cretaceous (late Aptian/early Albian) and/or Paleocene temperatures dominantly 50 80 °C based isotopes.