Wave-equation Traveltime Tomography Unravels a Scenario of Horizontal Mantle Flow Beneath the North China Craton

Abstract

The North China craton (NCC) was dominated by tectonic extension from late Cretaceous to Cenozoic, yet seismic studies on the relationship between crust extension and lithospheric mantle deformation are scarce. Here we present a three dimensional radially anisotropic model of NCC derived from wave-equation traveltime tomography to address this issue. We find a prominent low S-wave velocity anomaly at lithospheric mantle depths beneath the Taihang Mountains, which extends eastward with a gradually decreasing amplitude. The horizontally elongated low-velocity anomaly is also featured by a distinctive positive radial anisotropy (VSH>VSV). Combining geodetic and other seismic measurements, we speculate the presence of a horizontal mantle flow beneath central and eastern NCC, which led to the extension of the overlying crust. We suggest that the rollback of Western Pacific slab likely played a pivotal role in generating the horizontal mantle flow at lithospheric depth beneath the central and eastern NCC.

19th Annual Meeting of the Asia Oceania Geosciences Society

“…Low velocities and high Vp/Vs ratio of the ENCC using the short-distance dataset refute the possibility of the presence of a thin Archean layer at the mantle lithosphere lid beneath the ENCC. A recent adjoint traveltime tomography study (Dong et al 2021) is also consistent with this conclusion. The Ordos Block of the WNCC shows comparable velocities and Vp/Vs ratio with the typical cratons.…”