Геодинамический комплекс апогипербазитов зоны Передового хребта Большого Кавказа

Abstract

Apohyperbasite complexes are important indicators of geodynamic settings, their features indicate both the composition of the mantle substrate and the parameters of crustal metamorphism. In the structure of the folded-boulder structure of the Greater Caucasus, apohyperbasites are mainly associated with the Hercynian structural-tectonic zone of the Peredovoy Range, where the bulk of serpentinites is conventionally attributed to the late Proterozoic and combined into the Bedene complex. Electron probe and X-ray phase analyzes of serpentinites and accessory chromespinelides make it possible to determine whether the protolith belongs to the depleted substrate of the geodynamic complex of supra- and oversubduction zones (SSZ) and indicate its connection with dunite-harzburgite massifs. The composition of mantle chromespinelides varies from picotite with values of Cr# 0.36-0.43, Mg# 0.66-0.72 (in the Nizhneteberdinsky massif) to subferrichromite - chromites (in the Dakhovsky massif), which corresponds to the ophiolitic trend. During exhumation, the zoned grains of the mantle composition were partially preserved, since after recrystallization they are intensively processed by hydrothermal solutions with the formation of microporous and atoll structures. Serpentinites of chrysotile-antigorite and antigorite composition are typical for the southern part of the Peredovoy Range; less high-temperature lizardite-chrysotile associations are common to the north. Petrographic features of the studied serpentinite massifs of the zone of the Peredovoy Range of the Greater Caucasus make them similar to the massifs of the Central Belt and the East Ural megazone of the Southern Urals.