Paper No. 215-4
Presentation Time: 9:15 AM
IMAGED AND PREDICTED MANTLE STRUCTURE OF THE SUBDUCTED IZANAGI-PACIFIC RIDGE UNDER EAST ASIA
WU, Jonny1, LIN, Yi-An1 and FLAMENT, Nicolas2, (1)Department of Earth and Atmospheric Sciences, university of Houston, 3507 Cullen Blvd, Houston, TX 77204, (2)School of Earth and Environmental Sciences, University of Wollongong, Wollongong, 2522, Australia, jwu40@central.uh.edu
Ridge subduction geometric models predict the formation of gaps or ‘windows’ within a subducted slab, which we will herein refer to as ‘slab gaps’. Seismic tomographic imaging of these slab gaps offers potential first-order constraints for convergent margin plate reconstructions, as many competing plate tectonic models often show first-order differences in the reconstructed location and configuration of ridge-trench interactions. At East Asia, for example, Seton et al. (2015) argued for a laterally-extensive and low-angle Izanagi-Pacific ridge subduction along the East Asian margin in the late Cretaceous to early Cenozoic. In contrast, other plate reconstructions have implemented localised high-angle Pacific-Izanagi ridge subduction around Japan at ~90 Ma (Maruyama et al., 1997). Another study precluded any Pacific-Izanagi ridge subduction along East Asia due to the persistence of marginal ocean basins since the Cretaceous (Itoh et al., 2017).
In this study, we show for the first time a 4000 km-long, laterally-continuous and NE-SW trending slab gap mapped from tomography within the well-imaged East Asian mantle. Using both mantle flow models (Flament et al., 2017) and slab reconstruction methods (Wu et al., 2016) we argue that our mapped slab gap is the tomographic signature of the subducted Izanagi-Pacific ridge as modeled by Seton et al. (2015). Our study demonstrates that identifiable slab gaps from ancient ridge subductions can be imaged by seismic tomography and can persist within the mantle for at least 40 Ma. The mapping of ridge subduction-related slab gaps may offer new constraints for other convergent regions including western North America, where published plate reconstructions differ by up to 3000 km on the location of a Kula-Farallon ridge subduction in the late Cretaceous to early Cenozoic, with important consequences for potentially rapid northward terrane motions (i.e. the Baja-British Columbia hypothesis).
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