Petrogenesis and tectonic significance of the Triassic granites in Arhada area of Dong Ujimqin Qi,Inner Mongolia

Through zircon LA-MC-ICP-MS U-Pb geochronology,Lu-Hf isotopes,and whole-rock geochemical analysis of the Binbalechagan granitic complex in Arhada area of southern Daxinganling Mountains,this study determines the emplacement age,magma source characteristics,and geodynamic setting of the granite to provide important constraints on the tectonic evolution of the eastern Xing'an-Mongolia orogenic belt. Zircon LA-MC-ICP-MS U-Pb dating results indicate that the Binbalechagan complex was formed by multiple magmatic intrusions during the Late Triassic（233-220 Ma）,and is mainly composed of syenogranite and monzogranite. The in situ zircon Hf isotopic analyses of biotite syenogranite yield ε_Hf（t）values ranging from 7.8 to 14.5,with two-stage Hf model ages varying from 339 to 763 Ma.Geochemically,this complex is classified as weakly peraluminous,high-K calc-alkaline A-type granite. The primary magma originated from partial melting of juvenile continental crust,with possible addition of mantle-derived magma during emplacement. Combined with regional geological data,the Late Triassic Binbalechagan complex in Dong Ujimqin Qi area was formed in a post-orogenic extensional setting,and its geodynamic background may be related to the collision and amalgamation between the Xing'an block and Songliao block.