Archaean to Palaeoproterozoic high-grade evolution of the Belomorian eclogite province in the Gridino area, Fennoscandian Shield: Geochronological evidence

Abstract

The Belomorian eclogite province was repeatedly affected by multiple deformation episodes and metamorphism under moderate to high pressure. Within the Gridino area, high pressure processes developed in a continental crust of tonalite–trondhjemite–granodiorite (TTG) affinity that contains mafic pods and dykes, in which products of these processes are most clearly evident. New petrological, geochemical and geochronological data on mafic and felsic rocks, including PT-estimates, mineral chemistry, bulk rock chemistries, REE composition of the rocks and zircons and U–Pb and Lu–Hf geochronology presented in the paper make it possible to reproduce the magmatic and high-grade metamorphic evolution in the study area. In the framework of the extremely long-lasting geologic history recorded in the Belomorian province (3–1.7Ga), new geochronological data enabled us to define the succession of events that includes mafic dyke emplacement between 2.87 and 2.82Ga and eclogite facies metamorphism of the mafic dykes between ~2.82 and ~2.72Ga (most probably in the time span of 2.79–2.73Ga). The clockwise PT path of the Gridino association crosses the granulite- and amphibolite-facies PT fields during the time period of 2.72Ga to 2.64Ga. A special aspect of this work concerns the superposed subisobaric heating (thermal impact) with an increase in the temperature to granulite facies conditions at 2.4Ga. Later amphibolite facies metamorphism occurred at 2.0–1.9Ga. Our detailed geochronological and petrological studies reveal a complicated Mesoarchaean–Palaeoproterozoic history that involved deep subduction of the continental crust and a succession of plume-related events.