| Summary: | The Palaeoproterozoic lower crust, forming several belts and domains, is a major component of the crystalline basement within the large region to the southeast of the Baltic Sea in Belarus, Lithuania and Poland. Four stages of high grade metamorphism have been determined in the Western Lithuanian Granulite domain (WLG) and Belarus-Podlasie Granulite belt (BPG), the western East European Craton (EEC). We have carried out P-T studies, secondary ion mass-spectrometry (SIMS) zircon- and electron probe (EPMA) - monazite dating of peak metamorphism. The first stage occurred at 1.81-1.79 Ga under 800-900 °C and 8-10 kbar and was related to both accretionary and postcollisional tectonics in the South Baltic region, whereas the stages at 1.73-1.68 Ga (700-800 °C, 6-7 kbar), 1.62-1.58 Ga (700 °C, 4-5 kbar), and 1.52-1.50 Ga (900 °C, c. 10 kbar) can be attributed to extensional intracratonic regimes. The 1.81-1.79 Ga stage was connected both to the major Sarmatia-Fennoscandia collision and the eastward accretion, which led to the formation of Baltica (East-European Craton) during the assembly of the Columbia (Nuna) supercontinent. The later high grade events associated with intracratonic extensions and magmatism may be distal manifestations of accretionary processes along the long-lived common Laurentia-Baltica margin. The 1.52-1.50 Ga metamorphism was associated with extensive anorthosite-mangerite-charnockite-granite magmatism in already consolidated crust.
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