Composition and age of Sariolian volcanites of the Vermas formation in Northern Karelia

During this work, the composition of Sariolian volcanites of the Vermas formationin the Karelian region was studied and the U-Pb age of these rocks was first obtained (SHRIMP-II). In composition these volcanites are andesites and andesite-basalts, as well as, to a lesser extent, trachyandesites and trachyandesitobasalts of the calc-alkaline series. Due to porphyroblast crystallization, widely manifested in this region volcanites are enriched in TiO₂, Al₂O₃, Fe₂O_3total, K₂O, Rb, Cs, Zr, Hf, Y, Nb, Cr, V, Th and REE (primarily La and Ce). Rocks of the Vermas formation formed in the Paleoproterozoic (2412 ± 17 Ma) and were transformed as a result of the Svecofennian metamorphism in the interval of 1970 ± 15 Ma. The source of the melt and inherited zircons with the age of 2630–2760 Ma can be crustal material with the ancient Sm-Nd model age (3–3.1 Ga).