Calculation of the Equilibrium C-O-H Fluid for Ilmenite Xenocrysts and Estimation of the Diamond Potential

The composition of the C-O-H fluid is estimated on the basis of the composition of ilmenite xenocrysts. The P-T parameters and oxygen fugacity were assessed for peridotitic ilmenites from the diamond and diamond-free kimberlites of Africa and Yakutia. The composition of the equilibrium C-O-H fluid for these conditions was calculated. The diamond and diamond-free pipes of Angola and Yakutia are characterized by the H2O-rich and CO2-rich fluids, respectively. The results indicate that estimation of the composition of the C-O-H fluid in equilibrium with picroilmenite fits the necessary petrological criteria and may be applied for assessment of the diamond potential of mantle objects.