New Constraints For Convergent Margin Plate Tectonic Reconstructions From Imaged And Predicted Mantle Structure

Date

2020-12

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Abstract

Details of global plate models decrease back in geological time, such that approximately one-third of the Earth surface lacks sufficient plate tectonic constraints by the early Cenozoic ~50 Ma, increasing to >60% uncertainty by the Late Jurassic. The most significant global plate model uncertainties can be traced to convergent margins, where tectonic plates are lost due to subduction. Our aim is to develop new, non-traditional constraints for convergent margin plate reconstructions from imaged and predicted mantle structure using seismic tomography and forward geodynamic models, respectively. We apply recently-developed P-wave tomographic filtering to create ‘synthetic tomography’ of the geodynamic models. East Asia is one the most uncertain areas in global plate tectonics. We therefore focus on the East Asia Eurasian margin at both finer local scales within recent Earth history (i.e. the Cenozoic), and also at larger regional scales in earlier history (i.e. early Mesozoic). In southeast Asia, we address the highly debated proto-South China Sea (PSCS) tectonic history by assimilating published plate models into TERRA mantle convection models and comparing to seismic tomography and surface topographic warping from mantle viscous stresses (i.e. dynamic topography). The results suggest that double-sided (PSCS) subduction with earlier Borneo rotation and a smaller (<1000 km) Philippine Sea plate is more viable. At East Asia, a 4000 km-long, NE-SW trending ‘slab gap’ is mapped from seismic tomography that fits with the geodynamically-predicted signature of the subducted Izanagi-Pacific ridge. Our study suggests that slab gaps from ancient ridge subduction can be identified from seismic tomography models, and can persist within the mantle for at least 40 Ma. S-wave velocity perturbation converted temperatures shows the slab window is 100-250 K hotter than the surrounding slabs. We further investigate the plate reconstruction of the western Pacific Ocean basin during Jurassic to Cretaceous time by assimilating four different plate models with three mantle viscosity profiles; predicted and imaged mantle structures are compared. A synthetic geoid is also calculated and compared against the observed geoid. The results support intra-oceanic subduction in the western Pacific, contrary to popular Andean-style models that show continuous westward subduction along East Asia.

Description

Keywords

Plate tectonics, Proto-South China Sea, Geodynamic model, Global mantle convection, Seismic tomography, Ridge subduction, Slab window, Izanagi-Pacific ridge, East Asia plate models, Seismic-temperature conversion, Panthalassa, Western Pacific plate models

Citation

Portions of this document appear in: Lin, Yi‐An, Lorenzo Colli, Jonny Wu, and Bernhard SA Schuberth. "Where are the proto‐South China Sea slabs? SE Asian plate tectonics and mantle flow history from global mantle convection modeling." Journal of Geophysical Research: Solid Earth 125, no. 12 (2020): e2020JB019758.