Cenozoic Mantle-plate System Evolution Of East Asia Margin And Its Surface Expression

Tectonics are naturally connected to mantle convection processes.However,the evolution of deep mantle system can be enigmatic because of the complex tectonic configuration,poorly constrained subduction history as well as a lack of surface geological data.Such difficulty is present at northwest Pacific-east Asia margin.The presence of the world's only TTT triple junction and the poorly constrained Philippine Sea plate resulted in the uncertainty in regional tectonic history and corresponding geodynamic process.The Neogene geodynamic evolution of this region was explored with 4D forward geodynamic global models assimilated by reconstructed tectonic history in one million year increment.We first finished regional tectonic reconstruction in Gplates.The reconstructed history reached the consistence with a variety of surface observations including present plate motions,paleomagnetic data as well as geological observations from east Asia margin and Philippine Sea plate.The geodynamic modeling was completed with CitcomS.The simulation results reached first-order agreement with the slab architecture in seismic tomographic images,whose overlap score range from 70% to 90% in a quantitative analysis.It is illustrated the initiation of slab stagnation in the mantle transition zone beneath east Asia occurred since around 40 Ma.It is also emphasized the global subduction history since Mesozoic time played a significant role in shaping the slab morphology.Westward ambient mantle flow beneath northwest Pacific in the global plate tectonic context might have contributed to the formation of horizontal slab.Meanwhile,the presence of Izanagi slab in the lower mantle might have furnished the partial penetration at the slab leading edge.Tectonic coupled simulations constrained by alternative scenarios preferred the retreat of IzuBonin trench and clockwise rotation of Philippine Sea plate in Neogene.It is suggested the diachronous convergence between Philippine Sea plate and east Asia margin was accompanied by the development of a series of tears in the Pacific slab,which were responsible for the segmentation of horizontal slab in the mantle transition zone.The detachment of Pacific slab beneath Ryukyu trench occurred in late Miocene.Finally,we examine the contribution of mantle convection on surface topography based on the predicted buoyancy distribution with the geodynamic model.RMS analysis suggested the predicted dynamic topography achieved well consistence with the residual topography database in the target region spatially.Moreover,the temporal evolution of predicted dynamic topography achieved first order agreement with anomalous subsidence in the rifting basins in east Asia.Generally,the temporal and spatial evolution of dynamic topography suggests the successive subduction of Izanagi platePacific plate-Philippine Sea plate resulted cyclical uplift and subsidence of the east Asia margin.