Main Stages And Geodynamic Regimes Of The Earth's Crust Formation In East Antarctica In The Proterozoic And Early Paleozoic

摘要

Geological, geochemical, and isotopic data (U-Pb for zircon and Sm-Nd for whole-rock samples) are summarized for Proterozoic and Early Paleozoic geological complexes known from various regions of East Antarctica. The main events of tectonothermal and magmatic activity are outlined and correlated in space and time. The Paleoproterozoic is characterized as a period of rifting in Archean blocks, their partial mobilization, and formation of a new crustal material over a vast area occupied by present-day East Antarctica. In most areas, this material was repeatedly reworked at the subsequent stages of evolution (1800-1700, 1100-1000, 550-500 Ma). Complexes of Mesoproterozoic juvenile rocks (1500, 1400-1200,1150-1100 Ma) arising in convergent supra-subduction geodynamic settings are established in some areas (basalt-andesite and tonalite-granodiorite associations with characteristic geochemical signatures). The evolution of the Proterozoic regions in East Antarctica may be interpreted as a Wilson cycle with the destruction of the Archean megacontinent 2250 Ma ago and the ultimate closure of the secondary oceanic basins by 1000 Ma ago. The Mesoproterozoic regions make up a marginal volcanic-plutonic belt that combines three provinces of different ages corresponding to consecutive accretion of terranes 1500-1150, 1400-950, and 1150-1050 Ma ago. The Neoproterozoic and Early Paleozoic tec-tonomagmatic activity developed nonuniformly. In some regions, it is expressed in ductile deformation, gran-ulite-facies metamorphism, and postcollision magmatism; in other regions, a weak thermal effect and anorogenic magmatism are noted. The evolution of metamorphic complexes in the regime of isothermal decompression and the intraplate character of granitoids testify to the collision nature of the Early Paleozoic tectono-magmatic activity.