Tomographic evidence on multistage plate subduction in Northeast Asia: Implications for lithospheric deformation and intraplate volcanism

Since the Early Mesozoic, extensive Cretaceous intraplate volcanism, cratonic lithospheric thinning, and widespread crustal deformation have been documented in Northeast (NE) Asia. Global plate reconstruction models and paleo-magnetic data suggest a highly complex subduction system under NE Asia since the early Mesozoic, with proposed Mesozoic models including continuous subduction of the Izanagi plate and possible subduction of intra-oceanic arcs and early Cenozoic subduction of an active spreading ridge. Although subduction is a critical factor impacting continental deformation, the interactions between deep dynamic processes and surface tectonic responses remain debated. Based on a systematic investigation of seismic tomography, plate reconstruction, and igneous rock data, we present a new model of continental co-deformation with a multistage subduction history involving the Proto-ocean, Izanagi, and Pacific plates in Northeast Asia. The high-resolution mantle seismic structures were ascertained using a novel global tomographic inversion based on adaptive inversion mesh refinement and regional velocity perturbation constraints from 298,725 hand-picked and > 16 million arrival times of multiple P-wave phases (e.g., P, pP (pwP), PP, PcP, Pdiff, PKP, PKiKP) which were recorded by the 4,107 temporary and permanent stations in Northeast Asia. The unprecedented data reveal new integrative views on the geometry and behavior of mantle high-velocity anomalies associated with a sequence of oceanic lithosphere subduction events. The extensive compilation of dated volcanic samples provides strong constraints on past subduction events. Positions of remanent slabs derived from a multistage subduction history were reconstructed using the ages of initial subduction and slab sinking rates, where the geographical distribution of remnant slabs observed in our tomographic model helps to define the plate reconstruction history since the Early Mesozoic. The inferred multi-plate subduction configuration with slab advance, rollback, stagnation, break-off, and foundering, together with implied slab dehydration, should have resulted in various degrees of fluid-rock interactions among the slabs, the asthenosphere, and the continental lithosphere. We argued that fluid intrusions and mantle flow have played crucial roles in episodic intraplate volcanism and craton lithosphere thinning in different subduction stages. The Early Cretaceous intraplate volcanism, the ancient cratonic lithospheric thinning, and the crustal deformation have been caused mainly by a successive effect of the Proto oceanic plate and Izanagi slab subduction, but less by the Pacific plate subduction. These findings provide a systematical framework for understanding the co-evolution of the continental lithosphere with deep mantle dynamics in NE Asia and also serve as an excellent illustration of how the Earth's interior works.