Middle to Late Permian adakitic granites in the Xiari complex, North China: Insights into the final closure of the eastern Paleo-Asian ocean

Permian granitoids are widely distributed throughout the northern margin of the North China Craton (NCC). However, their origin (petrogenesis) and the tectonic settings in which they formed remain highly debated. The present study focuses on a granitic complex, the Xiari complex located in the western segment of Bainaimiao arc terrane that is composed of granodiorite porphyry, monzogranite, and granite porphyry. Zircon UPb dating yields an emplacement age range of ca. 263–254 Ma. Geochemically, all the granites show characteristics of adakitic rocks, with high K2O contents and enriched Nd isotopic compositions ranging from −14.3 to −6.0. These compositions are distinct from those of typical slab-derived adakitic lavas. Furthermore, the granites exhibit significantly higher SiO2 and lower Fe2O3 contents, yet show similar MgO, Cr, Co, Ni, and Mg# values compared to the coeval mafic enclaves indicate that these granites are unlikely to have formed by fractional crystallization of basaltic lavas. Instead, we infer that the Xiari complex most likely originated from partial melting of a thickened lower crust within the garnet stability field. Combining this data with information from previously reported A-type granites and volcanic rocks in adjacent regions, the age and petrogenesis of the Xiari complex suggest that the Bainaimiao arc terrane documents a collision-related crustal thickened event. This event was most likely linked to the far-field response of the amalgamation between the Mongolia block and the North China Craton. [Display omitted] •Middle to Late Permian high-K adakitic granites were identified in the Xiari area.•High-K adakitic granites were derived from overthickened lower continental crust.•The closure of the eastern PAO occurred before ca. 263 Ma in the western Bainaimiao arc.