Scientific publications

Unveiling the distinctive features of the metamorphic evolution of Precambrian granulite complexes is essential for the geodynamic reconstruction of early stages in Earth’s crust formation. Located in the northern Central Karelian terrane of the Karelian Craton is the Archean Voknavolok granulite complex (VGC), where relics of Neoarchean enderbites, charnockites and bipyroxene crystalline schist are preserved among gneisses, granites and amphibolites. Geological, petrological and geochronological studies show that this complex is split up into two variably aged (2.76–2.74 and 2.72–2.70 Ga) subcomplexes: southern and northern. The zircon age of the southern subcomplex is 2760–2740 Ma and that of the northern subcomplex is 2716–2704 Ma. The northern subcomplex comprises large granulite massifs, while the southern subcomplex is dominated by small bodies with relics of granulitic mineral associations persisting in highly diaphthorated biotite gneisses. The РТ-conditions for the formation of granulitic parageneses in the southern and northern subcomplexes are similar: Р = 3–7 kbar, Т = 750–810 °С (low- to moderate-pressure granulite facies). As the PT-conditions are relaxed, the retrograde metamorphism of the rocks is accompanied by the formation of actinolite, epidote, carbonate, chlorite, and titanite. The ages of the granulites are correlated with the occurrence of subduction volcanics in the associated greenstone belts: the southern subcomplex of the VGC is correlated with the Gimoly Group volcanics of the Kostomuksha Greenstone Belt and the northern subcomplex with the dacite andesite-dacite of the Khedozero-Bolshozero Belt. Available data suggest that the granulites were formed in the suprasubduction zones of variably Neoarchean island-arc systems.