Nd isotopic composition of the Paleozoic granitic rocks and structure of the deep crustal levels of the Chingiz Range, East Kazakhstan

Abstract

This work presents the Nd isotopic composition of Middle Cambrian to Late Paleozoic granitic rocks of the central part of the Chingiz Range in eastern Kazakhstan. All the rocks are characterized by a high positive ɛNd(t) value (no less than +4), which is similar to that of the country island arc volcanic rocks. These peculiarities allow us to suggest that the juvenile crust of this region was formed at the island arc stage. The continental crust was further thickened due to the transformation of the island arc rocks with an insignificant contribution of the crustal component. On the basis of these data, it is assumed that the deep crustal levels of the Chingiz Range are composed of tectonically juxtaposed, geochemically and isotopically similar, metamorphosed complexes of the Early Paleozoic island arcs.