THE NATURE OF MAGMATISM OF THE SIBERIAN PLATFORM ACCORDING TO DATA ON HOT HETEROGENEOUS ACCRETION OF THE EARTH

Abstract

The article presents planetary and geological evidence of the hot heterogeneous accretion of the Earth and the existence of a global magma ocean at an early stage of its evolution. It had a composition ranging from acidic in the upper parts to ultrabasic in the lower parts. With this in mind, the genesis of the main igneous rocks of the Siberian platform was considered. The Early Precambrian crystalline complexes arose from the crystallization of the upper parts of the layered magma ocean. Their heterogeneity was due to the multiple subsidence of the crystallized upper parts of the ocean and the emergence of the lower liquid ones. Autonomous anorthosites were formed by intrusion of not yet solidified plagioclase cumulates of its middle and main layers. Alkaline-ultrabasic carbonatite-bearing plutons were formed from the residual melts of the fractionated picrite layer of the magmatic ocean. Very high contents of rare elements in them were due to the long-term processes of their accumulation in the residual melts. The kimberlites arose from the residual melts of the bottom peridotite layer. The diamond in them crystallized due to the accumulation of carbon in the residual melts. Trap magmas were formed as a result of decompression melting processes in the emerging main plumes. Mesozoic alkaline intrusions of the Aldan Shield were formed by frictional remelting of alkaline differentiates of the magmatic ocean in zones of deep tectonic dislocations.