Adjoint traveltime tomography unravels a scenario of horizontal mantle flow beneath the North China craton

Xingpeng Dong,Ping Tong,Shaolin Liu,Fenglin Niu,Dinghui Yang

doi:10.1038/s41598-021-92048-8

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 adjoint 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.

Highlights

The thick lithosphere with low density and water content enables cratons to float on the asthenosphere and remain stable as indicated by lack of large-scale crustal deformation and magmatism[1,2]
Geochemical studies of basalts collected from the area indicate that the highly depleted Paleozoic lithosphere was somehow replaced by fertile peridotites in the Cenozoic, and seismic studies suggest that the present-day lithospheric thickness of the eastern North China craton (NCC) is approximately 80 ~ 120 km[13,14]
At a depth of 20 km, the Bohai gulf shows clear high shear wave velocity that further extends to the south of North China Basin, in contrast to eastern central tectonic belt and western North China Basin, which are dominated by a large-scale low velocity anomaly

Summary

Introduction

The thick lithosphere with low density and water content enables cratons to float on the asthenosphere and remain stable as indicated by lack of large-scale crustal deformation and magmatism[1,2]. In contrast to the consensus on the replacement of mantle lithosphere beneath the eastern NCC, debates continue regarding the mechanism and dynamic processes leading to the destruction of the cratonic root. To obtain high-resolution 3D lithospheric images beneath the NCC, we collected waveform data from 67 earthquakes, and recorded by 270 broadband stations of the permanent seismic network of the China Earthquake Administration[50] (Fig. 1).

Results

Conclusion