ISOTOPE EFFECTS ATTENDING DECARBONATION AT HIGH PT PARAMETERS: EXPERIMENTAL DATA

Isotope effects accompanying decarbonation process during the redox interaction of carbonate with metallic Fe and Ni at high PT parameters (1200 °C, 6.3 GPa) were assessed. Under these conditions, carbonate decomposition proceeds with the formation of reduced carbon (ΣC: graphite, carbides, carbon dissolved in metal) and metal oxides (wustite, Mg-wustite). The isotope effect calculated using the models of batch and Rayleigh decarbonation for carbon isotopes in the ΣC-carbonate system ranged from 1.2 to 0.5‰, for oxygen isotopes in the Mg-wustite-carbonate system from 1.1 to 0.46‰. The obtained estimates show that during redox-induced decarbonation, isotopic shifts of oxygen and carbon in the residual carbonate are directed towards its enrichment in heavy isotopes 18O and 13C. This direction of the isotopic shift is opposite in sign to the isotopic effects that arise during decarbonation with the separation of CO2 at low pressures.