First Data on the Age and P–T Formation Conditions of Zones of Low-Angle Dip Schistosity of the Belomorian Mobile Belt

Abstract

The low-angle dip schistosity zones of the Belomorian mobile belt of northern Karelia are zones of plastic flow of thrust origin. They were formed from 1.85 to 1.90 Ga: 1879 ± 21 Ma according to 40Ar/39Ar for amphibole from amphibolites and 1857 ± 13 Ma according to the Sm–Nd isochron in amphibolites. The P–T parameters of rock metamorphism in low-angle dip schistosity zones correspond to the boundary of amphibolite and granulite facies of metamorphism: T = 640–765°C, rarely rising to 826°C; P = 8.0–11.7 kbar. The hypothesis of the two-stage Paleoproterozoic metamorphism of rocks of the Belomorian mobile belt was introduced.