Sources of Mesoproterozoic igneous rocks and formation time of the continental crust of the Kokchetav Massif (Northern Kazakhstan)

Abstract

Within the Kokchetav massif (Northern Kazakhstan), Mesoproterozoic granites and acid volcanics are widespread: these are the youngest Precambrian igneous rocks forming basement of the region. The Nd isotopic characteristics (ε_Nd(t)–4.4 ÷–9.6, t_Nd(DM) 2.1–2.6 Ga) obtained for these rocks indicate that the source of their melts was the Early Precambrian continental crust. Thus, the continental crust of the Kokchetav Massif had basically been formed by the beginning of the Mesoproterozoic and during the Late Precambrian: later it became a source for the granitoid melts.