Abstract
Abstract
Formation homogenity and geodynamic conditions for the formation of apohyperbasites is an actual problem in geological study of the Paleozoic complexes of the Greater Caucasus. Study results of chromespinelids from serpentinite fragments of Paleozoic tectonic melange in the Western part of the Greater Caucasus (outcrops in Dakhovskiy uplift and Kisha river) tested with electron microprobe methods and processing of the results of elemental analysis using non-parametric statistics lead to the conclusion that apohyperbasites belong to ophiolites of subduction environments. Their composition is close to chromespinelids’ of ophiolite complexes of supra-subduction zones (SSZ) composition. Chromespinelides from the flank of Dakhovskoye uplift are represented by subferrochromite cores with rims of magnetite; transformation of subferrochromites during obduction process (Cr# ∼0.80-0.81, Mg# ∼0.35-0.40 in the least modified cores) in to chromites occurred under the conditions of the greenshist facies and was accompanied with redistribution and removal of aluminum and magnesium, and enrichment with iron and chromium. Chromespinelides from the serpentinites of contact Agarinskiy and Kizilkol’skiy thrust sheets presented with cores of aluminumchromite with relics of chrompicotites (Cr# ∼0.50-0.70, Mg# ∼0.39-0.64), surrounded by rims of ferrochromite – chromomagnetite. This transformation occurred on the boundary of the greenschist and low-temperature zone of the amphibolite facies and was accompanied by the substitution with iron for both two-and trivalent cations.