Title

G.A. KUCHEROVSKIY, N.A. ARESTOVA (IPGG RAS)

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.
Keywords: Baltic shield, Vodlozero domain, gabbroanorthosites, isotopic age of rocks, petrogenetic modeling.