CARBON ISOTOPIC COMPOSITION OF WHEWELLITE (CAC2O4.H2O) FROM DIFFERENTGEOLOGICAL ENVIRONMENTS AND ITS SIGNIFICANCE

Carbon isotopic composition of whewellite (CaC2O4.H2O) varies signific antly among individual types of occurrences from the Bohemian Massif, Czech Republic. The deltaC-13-values of whewellite found inside pelosi derite concretions in the coal-bearing Carboniferous Kladno Basin are unusually high from +3.2 to +14.7 parts per thousand, indicating influ ence of bacterial activity on the oxalate carbon isotopic composition. In the Tertiary Northern Bohemian Basin, where the depth of burial an d coalification grades are much lower, the deltaC-13-values of two whe wellite samples are -6.9 and -14.2 parts per thousand. Whewellites fro m low-temperature hydrothermal veins of the Pribram uranium deposits, where bacterial processes are highly unlikely, have deltaC-13-values o f -31.7 to -28.4 parts per thousand, identical to carbon isotopic comp osition of underlying black shales.