Geology, petrology and age of the gabbroanorthosites of the Oster lake area (Vodlozerskiy domain, Karelian province)
The gabbroanorthosite intrusion, emplaced into the volcanics of the Osterskaya structure of the Segozersko-Vodlozerskiy greenstoun belt and referred to the third stage of mafic-ultramafic magmatism, was studied. The age of the intrusion, determined using a SIMS SHRIMP II, is 2860 ± 9 Ma. Based on the obtained results, the major and trace elements composition of the intrusion was modeled. The obtained model implies that komatiite melt was formed due to a melting of the mantle lherzolite 120 km below surface, and then, it was fractured on the depth of 30 km and significantly (20 %) contaminated by tonalites of the basement. The obtained results indicate that between 2.86-2.84 Ma there was a temperature gradient under the Vodlozerskiy domain, probably generated by the mantle plume.