Petrogenesis and tectonic implications of Early Cretaceous volcanic rocks from the Shanghulin Basin within the north‐western Great Xing'an Range, NE China: Constraints from geochronology and geochemistry.

This study presents new zircon U–Pb ages, Sr–Nd–Hf isotopic data, and whole‐rock geochemical data obtained from the Early Cretaceous volcanic rocks from the north‐western Great Xing'an Range, Northeast China, to constrain the late Mesozoic magmatism and geodynamic setting of this region, which is located in the eastern segment of the Central Asian Orogenic Belt (CAOB). Zircon U–Pb age determinations show that the studied samples formed at 124–114 Ma with an Early Cretaceous magmatic event produced voluminous felsic and minor mafic volcanic rocks. The mafic rocks are dominantly basalt and basaltic andesite, with relatively low SiO2 contents (49.88–56.64 wt.%). These rocks are enriched in Th, U, large‐ion lithophile elements (LILE; e.g., Rb, Ba, and K) and light rare‐earth elements (REEs), and depleted in high‐field‐strength elements (HFSE; e.g., Nb, Ta, and Ti) and heavy REEs (Yb and Lu). The rocks have εNd(t) values of 0.44–0.75 and initial 87Sr/86Sr ratio of 0.70499–0.70548. These results indicate that the mafic rocks were derived from the partial melting of enriched lithospheric mantle that had been previously metasomatized by subduction‐related fluids and experienced variable amounts of fractional crystallization and moderate crustal contamination. In contrast to the mafic rocks, the felsic rocks are dominantly peraluminous trachytes, rhyolites, and dacites with high SiO2 contents and low MgO contents. These felsic rocks display enriched and variable concentrations of LILEs and REEs, show negative Eu anomalies, and have εHf(t) values of +2.6 to +8.3 with TDM2 ages of 1,014–655 Ma, indicating they were derived from partial melting of juvenile crustal materials. These Early Cretaceous igneous rock assemblages record a post‐collisional lithospheric extensional setting resulting from the closure of the Mongol–Okhotsk Ocean, consistent with the results of previous studies on the contemporaneous tectono‐magmatic activities in NE China. [ABSTRACT FROM AUTHOR]