DURATION OF MIGMATITE FORMATION IN THE GRANULITE-FACIES METAMORPHISM ZONE OF SVECOFENNIDES OF THE LADOGA REGION, SOUTHEASTERN BALTIC SHIELD

Abstract

High-temperature metamorphism zone is characterized by partial melting of rocks and the generation of diverse migmatite leucosomes in the course of rock deformations leading to the structural and morphological diversity of rocks. Therefore, polymigmatites represent a unique rock assemblage, in which separate members of the evolution series related to the successive generation (crystallization) of leucosomes retain, to variable extent, characteristics of the evolving environment of mineral formation. Isotope dating of differentaged (with respect to geological relationships) leucosomes makes it possible to estimate the timing of ultrametamorphic events and respective deformations.