Geochemistry and petrogenesis of Permian granitoids in the northwestern margin of the North China Craton: insights from the Dongshengmiao pluton, Inner Mongolia

The zircons in quartz diorite have ε Hf ( t ) values of −15.6 to −11.1 with two-stage Hf model ages (T DM2 ) of 1997–2281 Ma, suggesting that the magma was derived from partial melting of old continental materials. In contrast, porphyritic granite shows variable Hf isotopic composition with ε Hf ( t ) values of −13.7 to −2.6 and T DM2 of 1471–2167 Ma, indicating a heterogeneous magma source. Besides the Dongshengmiao pluton, all the Permian granitoids in the northwestern margin of the NCC exhibit similar geochemical characteristics, including enrichment in LILEs, depletion in Nb and Ta, and enriched Hf isotopic signatures.

The comprehensive geochemical data indicate that these Permian granitoids are derived from magma mixing between dominant partial melting of ancient felsic crustal materials and minor juvenile basaltic magma. Tectonically, the Dongshengmiao and other granitoids in the northwestern margin of the NCC may have been formed in a post-collisional extensional setting.