Deformation of the northeastern Tibetan Plateau and adjacent areas: Evidence from MT array data

Abstract

The uplift and growth of the Tibetan Plateau is an essential geologic issue. The closure of the Neo-Tethys Ocean and northward subduction of the Indian Plate formed the Tibetan Plateau and influenced the strain on its northeastern margin. We obtained the lithospheric electrical structure by inversion of MT array data collected at the Alxa and Ordos blocks neighboring the northeastern Tibetan Plateau. It shows the Ordos Block has noticeable electrical differences between the north and south parts. The northern lower crust to the upper mantle characterized large-scale low-resistivity anomaly, while the south is a stable craton block. The retreat of the Paleo-Pacific Plate caused the North China Craton to be in a tensional environment. With the northward subduction of the Indian lithosphere, the Tibetan Plateau continues to grow in a northeastern direction, resulting in an intensification of the subduction of the Alxa Block to the Ordos Block, and the north Ordos Block was pried up and in a weak state. The Asian asthenosphere became active under the influence of Indian lithospheric subduction. It jumped over the rigid Alxa and southern Ordos blocks to deform the northern part of the Ordos Block and form the large-scale partial melting. Since partial melt is more viscous than rigid blocks, it better equilibrates crustal deformation, resulting in flatter topography.