Природа раннедокембрийских кристаллических комплексов

Abstract

The obtained evidence of hot heterogeneous accretion of the Earth leads to a fundamentally new solution of the problem of the genesis of Early Precambrian crystal complexes. According to this approach, a powerful impact heat release during accretion resulted in the formation of a layered global magmatic ocean. Its upper acidic layer arose from low-pressure residual melts of the bottom parts of the still shallow early ocean, fractionated under the influence of an increase in the load pressure of the forming upper layers. The solidification of the uppermost parts of the acidic layer led to the formation of the most ancient tonalite-trondyemite complexes. Gneiss-crystalshale complexes were formed from its deeper parts by lowering the crystallized near-surface areas together with sediments accumulated on them and lifting the underlying magmas of often more mafic composition in their place. Leaching of the near-surface parts of the solidified rocks under the influence of acidic emanations of the magmatic ocean caused the predominance of quartzites and high-alumina gneisses among the oldest pararocks. Due to the solidification of the magmatic ocean from top to bottom, the isotopic age of gneiss decreases on average with depth. The surfacing of residual melts of its various layers led to the evolution of magmatism of ancient platforms from acidic to alkaline-ultrabasic and kimberlite. The separation of ore-bearing emanations of the magmatic ocean caused the formation of numerous often unique deposits.