Генезис магм с позиции горячей гетерогенной аккреции Земли

Abstract

The obtained numerous proofs of hot heterogeneous accretion of the Earth lead to a fundamentally new solution of the magma genesis problem. According to these data, in the course of the silicate mantle accretion, the global magmatic ocean emerged under the impact heat emission. Its bottom part crystallized and fractionated as a result of the pressure increase of the upper parts being formed. Cumulates formed the ultrabasic mantle; residual melts, the magmatic ocean. The increase in ocean temperature and depth caused the evolution of bottom residual melts from acidic to ultrabasic, the appearance of corresponding layers in the ocean, and the reverse geothermal gradient in the mantle. The top-down cooling and crystallization of the ocean, 3.8 billion years ago, Early Precambrian crystal complexes, acidic crust, and the lithosphere of ancient platforms were formed. The separation of residual melts from various layers determined the evolution of magmatism from acidic to alkaline-ultramafic and kimberlite. Heating of the mantle by a high-temperature core resulted in the appearance of a direct geothermal gradient at the end of the Proterozoic, convection in the mantle, and modern geodynamic environments. In the latter, magmas are formed by the frictional and decompression remelting of the magmatic ocean differentiates.