Tectonics and volcanism in East Asia: Insights from geophysical observations

We review geophysical and geochemical properties in the vicinity of the stagnant Pacific slab beneath northeast China, Korea and Japan to understand the origin and current state of intraplate volcanism in East Asia. East Asia has been susceptible to intensive volcanism since the Cretaceous. In particular, during the Cenozoic, Jeju Island, Korea is the most significant volcanic construct in East Asia. The generation of adakites and A-type granitoids littered throughout East Asia during the Cretaceous has been previously explained by the subduction of the Izanagi-Pacific ridge system. However, a recently revised plate reconstruction model does not comprise such a tectonic episode and consequently fails to explain adakites in arc magmatism during the Cretaceous. Thus, we propose an alternative hypothesis: temporal plume-slab interaction on the source of East Asian magmatism in order to trigger the adakites in arc magmatism without ridge subduction. In addition, we provide an overview on the tectonics and volcanism of Jeju Island during the Cenozoic in the context of the lithospheric structure from seismological constraints and recent geochemical results. The main scientific aims are to understand the consequences of mantle mixing in response to long-term subduction and subsequent changes on the stress state to determine the distribution of chemical heterogeneities, and thus define the origin and development of intraplate volcanism in East Asia. Although geophysical and geochemical data for Jeju Island are not sufficient at present, we strongly state that Jeju Island and the surrounding regions hold a key to unraveling the source of intraplate magmatism since the Cretaceous.