ABSTRACT

The variation of the carbon isotope ratio of calcite samples collected from the micro crystalline main body of a hydrothermal ore vein has been found to follow a trend opposite to that shown by the oxygen isotope ratio of the same samples. This anomalous behaviour is explained by the presumable mechanism of the formation of the vein. The “oxygen-carbon isotopic behaviour” has been found normal in the case of big single crystals of calcite from the same vein.