U-PB isotope age and tectonic position of the paleoproterosoic andesite porphyrites, Kursk block, Eastern Sarmatia

Abstract

One of the manifestations of volcanics within the Kursk block of Eastern Sarmatia is the ande-site porphyrites of the Glazunovka suite, opened by one well 2926 on the northern flank of the Oryol-Tim sinform. Andesitic porphyrites are content (SiO2 = 57–61% and increased magnesium (Mg # = 0,45– 0,62)). They belong to metaaluminous potassium-sodium (Na2O / K2O = 1,1–3,2) rocks. According to the K2O – SiO2 ratio, porphyrites are high-potassium alkali-calcareous series differences. The eruption age of Glazunovka suite andesite porphyrites from the Kursk block of East Sarmatia is determinated at 2067 ± 5 Ma. Our geochronological data and discriminant diagram interpretation suggest that eruption of the andesite porphyrites occured in post-collisional setting.