Lithospheric reworking at the western margins of the Ordos Block Revealed by Joint inversion of Phase velocities and Receiver Functions

We obtained a high-resolution 3-D shear wave velocity model of the crust and upper mantle beneath the western part of the Ordos block (WOB) by jointly inverting the Rayleigh wave phase velocities over broad period (8-135 s) and P-wave receiver functions. The resulting model clearly reveals lithospheric structural heterogeneities across the WOB and its margins. A nearly trapezoid-shaped high-velocity anomaly in the lithosphere is shown beneath the interior of the WOB. Moreover， we observe low-velocity anomalies extending from the upper mantle to surface beneath the north margin of the WOB， while the upper mantle at the south margin exhibits a NW-SE low-velocity channel. We suggest that the mantle upwelling may be the primary mechanism driving the lithospheric deformation beneath the north margin of the WOB. And the upper mantle of the south margin of the WOB is characterized by the lateral asthenospheric flow， which could be caused by the India–Eurasia collision. Both the dynamic processes at the north and south margins of the WOB have modified the stable cratonic keel of the Ordos block. Overall， our new results provide solid evidence for the lithospheric reworking at the north and south margins of the WOB.