Patterns of Phase Formation in Kimberlite under Reducing Conditions at 4 GPa and 1500°C

Experimental data on the interaction of an iron melt with natural kimberlite at a temperature of 1500 ± 25°C and a pressure of 4.0 ± 0.2 GPa corresponding to the conditions of the Earth’s upper mantle are reported. It was shown that the interaction of the carbonate component of kimberlite with iron resulted in the formation of magnesioferrite, a solid solution of carbon in iron, and carbide phases. The silicate–oxide part of the system included a mineral assemblage of olivine + pyroxene + garnet + monticellite + perovskite + (probably) ilmenite. The results obtained provide evidence for the instability of the carbonate component of kimberlite under the reducing conditions in the presence of metallic iron.