Asthenospheric Flow Channel From Northeastern Tibet Imaged by Seismic Tomography Between Ordos Block and Yangtze Craton

Abstract

The collision between India and Eurasia forming the Tibetan Plateau since the early Cenozoic had led to the crustal and upper-mantle (asthenospheric) extrusion from the plateau to the east. However, the Ordos and Yangtze cratonic keels next to the northeastern and eastern Tibetan Plateau obstruct this eastward asthenospheric extrusion. With a dense seismic array, for the first time, we imaged a narrow low P-wave and S-wave velocity anomaly characterized with higher Vp/Vs between these two Archean cratons at depths ranging from 150 to 300 km using finite-frequency tomography. We interpret this low-velocity anomaly as a channel of the eastward asthenospheric flow from the Tibetan Plateau. We provide solid seismic observations for a pathway of the Tibetan asthenospheric extrusion due to the ongoing collision of the Indian and Eurasian continents. This asthenospheric extrusion from the Tibetan Plateau could influence the lithospheric reworking in the central and eastern North China Craton.