Abstract

Late Cenozoic intraplate volcanism in the Changbai volcanic field straddles the border between China and North Korea, forming basic (alkali basalts and tholeiites) and intermediate–acidic (trachytes and peralkaline rhyolites) volcanic rocks with ages ranging from 19.9 Ma to the present. Major and trace elements and Sr–Nd–Pb isotopic compositions indicate that the basic magmas were formed by partial melting of the depleted mid-ocean ridge basalt-source mantle and contaminated by aqueous fluids with EM1-like isotopic signatures from the lower continental crust, whereas the intermediate–acidic magmas resulted from assimilation–fractional crystallization processes on the basic magmas. On the basis of petrological and geochemical studies, we propose that a magma underplating model could be used to explain the genesis of the Late Cenozoic intraplate volcanism. In this model, the mantle-derived basaltic magma was underplated at the base of the continental crust and contaminated by EM1-like aqueous fluids liberated from the lower crustal granulites. Geodynamic processes responsible for the magma underplating and subsequent eruption might be lithospheric extension and small-scale thermal upwelling, induced by episodic changes in convergence rates between the Eurasian and Pacific plates, indicating a genetic link between the intraplate volcanism and deep subduction of the Pacific slab.

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