Metallic inclusions in natural diamonds and their evolution in the postcrystallization period

Based on experimental results on the growth of diamonds and the phase diagram of the iron-carbon system at high pressures and temperatures, an analysis of the conditions of phase formation in metal inclusions in natural diamonds from kimberlites was carried out. Metallic inclusions are present in both lithospheric and sublithospheric diamonds associated with both peridotite and eclogite assemblages of mantle minerals. It is argued that the equilibrium phases at the post-crystallization stage of the genesis of natural diamonds are iron carbides and oxides; the presence of native metals in inclusions indicates that equilibrium has not been achieved. The presence of native iron in inclusions also indicates a high rate of decrease in pressure and temperature at the post-crystallization stage of the genesis of natural diamonds. The change in P-T parameters during diamonds transportation to the Earth's surface probably occurred as an explosion process characterized by a rapid pressure decrease and high temperature maintaining for some time.