EXPERIMENTAL STUDY OF DIAMOND FORMATION IN THE MOLTEN CARBONATE-SILICATE ROCKS OF THE KOKCHETAV METAMORPHIC COMPLEX AT 5.5-7.5 GPA

Abstract

The genesis of diamonds from metamorphic complexes (Kokchetav in Kazakhstan and Dabie Shan in China) has been experimentally modeled. For the first time, diamonds were synthesized at pressures of 5.5-7.5 GPa in the molten carbonate-silicate (dolomite-garnet-clinopyroxene) rock of the Kumdy Kol deposit, Kokchetav. The melts were oversaturated with respect to dissolved carbon. The experimental data on the growth of diamond crystals both spontaneously nucleated and on seeds were used to construct the P-T diagram of diamond crystallization. In addition to diamond, the carbonate-silicate melts produced the high-pressure garnet-clinopyroxene association. The formation of diamonds under mantle conditions and their transport into the Earth's crust are discussed.