AGE AND TECTONIC SETTING OF THE KOPRI-TYPE GRANITOIDS OF THE JUNCTION ZONE OF THE DZHUGDZHUR-STANOVOY AND WEST-STANOVOY SUPERTERRANES OF THE CENTRAL ASIAN FOLD BELT

Geochemical, geochronological (U-Pb on ID TIMS zircons), and isotope-geochemical (Sm-Nd) studies of the Kopri-type granitoids of the Tukuringra Complex have been done. The granitoids localized exclusively in the zone of the Dzheltulak suture, which separates the Dzhugdzhur-Stanovoy and West Stanovoy superterranes of the Central Asian fold belt. It has been established that they can be classified as postcollision granitoids of elevated alkalinity and basicity of the adakite type, formed in the age range of 127 ± 1–126 ± 1 Ma, which are part of the Late Mesozoic postcollision Stanovoy volcano-plutonic belt extending in the sublatitudinal direction from the Sea of Okhotsk inland continent subparallel to the Mongolo-Okhotsk suture zone for more than 1000 km and stitching the Dzhugdzhur-Stanovoy and West- Stanovoy superterranes. The structural position of massifs of the Kopri-type granitoids fixes the upper age boundary of the formation of the Dzheltulak suture. The formation of the initial magmas of these granitoids is connected with an essentially lithospheric source formed as a result of mixing of the Early Precambrian and younger, apparently, Phanerozoic component. The similarity in the Nd isotopic composition of the granitoids of the Kopri-type with similar in composition and age granitoids of the West Stanovoy superterrane most likely indicates the similarity of their sources, as well as the fact that the Dzheltulak suture zone “plunges” in the northeast direction under the structures of the Dzhugdzhur–Stanovoy superterrane. This is in full accordance with modern ideas about the features of the deep structure of the junction of the Eurasian and Amur lithospheric plates.