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The Central Asian Orogenic Belt (CAOB), which formed by closure of the Paleo-Asian Ocean, is one of the largest Phanerozoic accretionary orogens on Earth. However, the timing of final closure of the Paleo-Asian Ocean remains debated. Here we present new zircon U-Pb dating, oxygen fugacity estimates, and whole-rock geochemical and Sr-Nd isotopic data from intermediate and felsic intrusive rocks in the Chunhua area of NE China to constrain their petrogenesis and assess the tectonic implications for the evolution of the eastern CAOB. Zircon U-Pb dating indicates that the intrusive rocks formed in the late Permian (257-261 Ma). Based on their chemical compositions, two groups of rocks can be identified. Group Ι consists mainly of dioritic rocks (e.g., gabbroic diorites, diorites and tonalites) with relatively low SiO 2 but high MgO contents and Mg# values. Petrological and geochemical characteristicsshow that Group Ι rocks were formed by mixing of mantle-and crust-derived magmas.Mafic microgranular enclaves within Group Ι rocks have high MgO contents (up to 9 wt%) and depleted isotopic compositions (ε Nd (t) = +4.3 to +7.2), and probably represent mafic end-member magmas derived from a metasomatized lithospheric mantle, which subsequently were injected into the felsic crustal magmas. In contrast, Group ΙI rocks are mostly granodiorites characterized by high SiO 2 and low Mg# values, with high Sr/Y and La/Yb ratios. These rocks were probably generated by partial melting of mafic lower crust with little or no addition of mantle materials.Trace element modeling suggests that intracrustal differentiation was dominated by hornblende fractionation and caused the high Sr/Y and La/Yb signatures of Group ΙI

Convergent plate boundaries are the primary location for the formation of continental crust by the intrusion of arc batholiths that contain essentially mantle-derived magmas. This paper presents two types of arc granitoids (enclave-free monzogranites and enclave-bearing granodiorites) in northeastern (NE) China to understand crustal evolution and growth in the eastern Asian continental margin. The monzogranites (189 Ma) show characteristics typical of upper continental crust, with high SiO2 contents and enrichment of K, Rb, and Pb. These monzogranites have low ISr (87Sr/86Sr) ratios (0.70378–0.70413) and positive εNd (t) (+2.2 to +2.3) and εHf (t) (+7.3 to +10.2) values. These features, combined with high zircon saturation temperatures (TZr > 800 °C), suggest that the monzogranites were generated by the heat-fluxed melting of juvenile lower crust. In contrast, the granodiorites (171 Ma) contain abundant coeval mafic enclaves and show relatively low silica contents, low TZr (748–799 °C), and particularly wide variation in εHf (t) (−3.5 to +5.6), implying a hybrid origin involving both mantle- and crust-derived components. Isotopic modeling indicates that mantle material accounts for around 60%–70% of the hybrid magmas by volume. The granodiorites have adakite-like signatures (e.g., Sr/Y > 21 and [La/Yb]N > 15), which may have been primarily caused by a process of magma mixing and hornblende-dominated fractional fractionation, rather than through melting of a subducting slab or thickened lower crust. The two distinct granitoids (monzogranites and granodiorites) represent continental crustal reworking and growth, respectively, related to the subduction of the Paleo-Pacific Plate beneath the eastern Asian continental margin during the Jurassic.