Age and Tectonic Setting of the Kopri-Type Granitoids at the Junction Zone of the Dzhugdzhur–Stanovoi and Western Stanovoi Superterranes of the Central Asian Fold Belt

Abstract

Abstract Geochemical, geochronological (U–Pb on zircons, ID TIMS), and isotope–geochemical (Sm–Nd) studies of Kopri-type granitoids of the Tukuringra Complex have been carried out. The granitoids are located exclusively in the zone of the Dzheltulak suture, which separates the Dzhugdzhur–Stanovoi and Western Stanovoi superterranes of the Central Asian fold belt. It has been established that they can be classified as postcollisional adakite-like granitoids of elevated alkalinity and adakite-type basicity, formed in the age range between 127 ± 1 and 126 ± 1 Ma, which are part of the Late Mesozoic postcollisional Stanovoi volcano-plutonic belt that extends more than 1000 km in the sublatitudinal direction from the Sea of Okhotsk into the continent subparallel to the Mongolia–Okhotsk suture zone and stitches the Dzhugdzhur–Stanovoi and the Western Stanovoi superterranes. The structural position of the Kopri-type granitoid massifs registers the upper age limit of the Dzheltulak suture. Formation of the parent melts of these granitoids is associated with an essentially lithospheric source formed as a result of mixing of the Early Precambrian and a younger, apparently Phanerozoic component. In contrast to other granitoids of the Stanovoi belt that are close in composition and age, the granitoids under consideration are characterized by a certain increase in the role of the asthenospheric component in their source, which is probably due to their localization in the zone of elevated lithospheric permeability and at the junction of faults of different orientations, generally sublatitudinal, guided by the Mongolia–Okhotsk lineament, and northwestward, associated with the development of the Dzheltulak suture.