Early evolution of Earth and beginning of its geological history: how and when granitoid magmas appeared

Abstract

Earth has a number of differences from the planets of the Solar System, as well as other stellar-planetary systems, which were acquired during its formation and geological history. The early chaotian aeon was marked by Earth’s accretion, the differentiation of its primary material into a mantle and a core, as well as the by formation of its satellite (Moon). Earth’s geological history began 4500 million years ago in the Hadean aeon. At that time, the endogenous processes on Earth were largely controlled by meteorite and asteroid bombardments, which caused large-scale melting and differentiation of its upper layers. In magmatic chambers, differentiation proceeded until the appearance of granitoid melts. The Hadean continental crust was almost completely destroyed by meteorite bombardments, with the last heavy bombardment occurring at the end of the Hadean aeon (4000–3900 Ma). Conclusions about the geological situation of this aeon can be drawn only from the preserved Hadean zircons. In particular, their geochemical features indicate that Earth had an atmosphere. The Hadean aeon was replaced by the Archaean one, starting from which the processes of self-organisation were predominant on Earth. At that time, a crust composed of komatiite-basalt and tonalite-trondhjemite-granodiorite (TTG) rock series was forming. Its formation was driven by sagduction processes – vertical growth of the crust over rising mantle plumes. Thus, the lower basaltic crust subsided into the mantle, eclogitised and melted, which led to the appearance of sodium TTG rocks series. At the end of the Archaean aeon (3.1–3.0 Ga), lid tectonics, which determined the structure and development of the Archaean crust, was replaced by small-plate tectonics that later evolved into modern plate tectonics combined with mantle plume tectonics.