New find of high-pressure rocks in the Belomorian mobile belt

Abstract

1267 The Belomorian mobile belt (BMB) of Karelia is one of the quite complex geological structures, for which repeated highpressure metamorphism is typi� cal. Successful reconstruction of the Archean geody� namic history of the BMB is predominantly based on the detailed microanalysis of mineral parageneses and correct estimations of the Р-Т parameters of meta� morphism. Two stages of granulite metamorphism were estab� lished in the Archean history of the BMB. The first one is Early Archean granulite metamorphism with an age of 2820 ± 15 Ma (1, 2). The second one is Neoarchean granulite metamorphism controlled by enderbite and charnockite intrusions (2.71-2.73 Ga) (2, 3). However, these metamorphic events occurred at low or moderate pressure (4-5 or 6-7 kbar) and were found in the western domain of the BMB (2, 4). Only Neoarchean metamorphism with an age of 2691 ± 5 Ma (2, 5) occurring in both western and eastern domains of the BMB was characterized by a high pres� sure regime (9-10 kbar with a maximum up to 12- 13 kbar) (4). At the same time, this metamorphism occurred under the conditions of highpressure amphibolite facies (650-700°C) (4). Highpressure metamorphism of the eclogite facies with an age of 2.72 Ga (14-17 kbar) (2, 6) and highpressure granu� lite and amphibolite facies on the retrograde stage were registered in the Gridino zone of the tectonic melange (far eastern part of the BMB). In this relation finds of highpressure Grt-Cpx-