Magmatism and geodynamic scenarios at the Archean-Paleoproterozoic boundary. A view from Karelia

This study synthesizes the findings on the geodynamic regimes of emplacement and development of igneous rocks and associated terrigenous complexes forming the supracrustal part of the Vodlozero Terrane (southeastern part of the Karelian Craton) during the Mesoarchean – Paleoproterozoic interval. Early geodynamic processes (during the Meso-Neoarchean) are reconstructed based on the study of key strato-tectonic associations of the Vedlozero-Segozero Greenstone Belt. The transformation of geodynamic regimes during cratonization in the Paleoproterozoic is substantiated by the example of the Onega Basin’s formations, which overlie the greenstone complex. It is established that crustal formation in the Vodlozero Terrane during the Meso-Neoarchean was controlled by subduction-collisional processes, comparable in duration to a full Wilson cycle. After the stage of continental crust stabilization, around 2.5 billion years ago, magmatic reactivation of the territory occurred. The Karelian Craton experienced an uplift and intense erosion, which led to the formation of subaerial weathering crusts. The change in geodynamic regimes was triggered by the onset of a plume event, heralding the formation of a large igneous province. The development of the territory occurred under conditions of continental rifting (in the interval 2.5–2.45 billion years) with the formation of a siliceous high-Mg andesibasalt association. This association is characterized by a dual geochemical nature – plume and subduction-related – which is explained by the involvement of Archean slab fragments in melting and contamination by melts of sanukitoid granitoids.