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Category: Hypothesis

Description: Various geodynamic mechanisms can lead to the penetration of siliceous carbonates into the mantle wedge. Their thermal decomposition in the “mantle olivine autoclave” can be a mechanism for the formation of diamond erupted in subduction zone of Kamchatka. Using the theory of poro-elasticity, we showed that rapid heating of a mixture of sideritic dolomite and silica at 150-200oC can lead to an increase in pressure by 2-3 GPa. With the initial parameters P = 2 GPa and T = 830oC, the carbonic fluid produced during the reaction would get into the PT stability field of the diamond. The growth of diamond in the PT field of metastable graphite can be enhanced by microparticles of native Ni and Mn formed by the thermal decomposition of gaseous carbonyls. The corresponding abundant micro-inclusions of Ni and Mn are found in Kamchatka diamonds.