ABSTRACT

Late Mesozoic volcanic rocks are widespread in the Great Xing’an Range (GXR), Northeast (NE) China. However, details of the tectono-magmatic evolution during the Late Mesozoic are poorly understood. In this paper, new zircon U–Pb, Lu–Hf, and whole-rock geochemical data from Late Mesozoic volcanics in the southern GXR, are used to further constrain the tectono-magmatic evolution of the region. Late Mesozoic magmatism in the GXR, eastern Mongolia and southern Transbaikalia occurred during the Early Cretaceous (120–140 Ma) and Late Jurassic (150–163 Ma) periods. Late Jurassic trachyandesites-trachytes show a low rare earth element and moderate light rare earth element (LREE) enrichment with no Eu anomalies. Early Cretaceous trachytes are characterized by an LREE enrichment and negative Eu anomalies. Contemporaneous rhyolites exhibit a significant LREE enrichment, A–type granitoid affinity, and pronounced negative Eu anomalies. Different negative Nb, Ta, and Ti anomalies, and positive zircon ε_Hf(t) values, indicate that the ~160 Ma trachyandesites-trachytes are derived from partial melting of the lithospheric mantle that was metasomatized by subduction-related fluids. The ~125 Ma trachytes and rhyolites were possibly generated by partial melting of the accreted Meso-Neoproterozoic lower crust. New and previously published geochemical, isotopic and geochronological data from the southern GXR, eastern Mongolia and East-Transbaikalia, suggest that Late Jurassic–Early Cretaceous volcanism in the southern GXR occurred during the post-collisional extension after the closure of the Mongol–Okhotsk Ocean.