No abstract

We present zircon U-Pb and Hf isotopic and whole-rock geochemical data for late Paleozoic igneous rocks in the central Great Xing'an Range, northeast China, to constrain the late Paleozoic amalgamation history of the united Xing'an-Erguna and Songnen-Zhangguangcai Range massifs. Based on zircon U-Pb dating, we ascertain three main stages of magmatic events: Late Devonian (381-364 Ma), early Carboniferous (360-341 Ma), and late early Carboniferous-early Permian (328-271 Ma). Late Devonian rhyolites originated from partial melting of Meso-proterozoic accreted lower crust. The crust-derived rhyolites and coeval mantle-derived basalts constitute a bimodal volcanic association in the west. Early Carboniferous igneous rocks include syenogranites, monzogranites, gabbro diorites, and gabbros. The granitoids are derived from partial melting of Meso-proterozoic accreted lower crust. The gabbros and gabbro diorites show the spatial variation in zircon ε Hf (t) values (À0.53 to +0.84 in the east and +12.3 to +13.5 in the west), which imply that they were mainly derived from metasomatized mantle wedge and asthenosphere mantle, respectively. These characteristics indicate that northwest-towards high-angle subduction of the Paleo-Asian Ocean plate beneath the united Xing'an-Erguna Massif induced arc magmatism in the east and back-arc magmatism (similar to back-arc rift) in the west during the Late Devonian to early Carboniferous. Late early Carboniferousearly Permian sub-alkaline and alkaline igneous rocks are characterized by multiple sources, such as the depleted mantle, juvenile lower crust, and thickening lower crust. Their temporal variations in geochemical characteristics imply that the central Great Xing'an Range was situated under a transitional setting from syn-collisional to post-collisional during the late early Carboniferous to early Permian. Using the combined insight from lithofacies palaeogeography and regional magmatisms, we suggest amalgamation of the united Xing'an-Erguna and Songnen-Zhangguangcai Range massifs occurred during the late early Carboniferous to late Carboniferous.

No abstract