Preliminary Results of Material Transport Model of Rigid Block Extrusion Driven by Crustal Flow Beneath the SE Tibetan Plateau: insights from high-resolution 3-D Magnetotelluric Imaging

Abstract

     The collision between the Indian and Eurasian plates in the Cenozoic eras resulted in the formation of the world's largest and highest plateau. The intensive collision, subduction, and related deep dynamic processes led to significant crustal shortening, uplifting, and expansion of the Plateau, accompanied by eastward extrusion of plateau materials. The southeastern Tibetan Plateau (SETP) is one of the most important channels for escaping plateau materials. The widespread existence of crustal weak material flow in the SETP has become widely accepted. However, previous research has mostly been limited to two-dimensional profiles or spaced data measurement points. Therefore, obtaining reliable and high-resolution geophysical models of the lithosphere is crucial for understanding the deformation mechanisms of the plateau.    Our three-dimensional resistivity model shows unprecedented resolution of the Simao Block of the Indochina Block, offering new insights into the material transport and deformation mechanisms of the SETP. Two consecutive large-scale high-conductivity anomalies observed in the middle-lower crust are speculated to be partial melting associated with crustal flow. The rigid lithosphere separated by significant strike-slip faults on the SETP may be pulled by ductile materials flow, where plastic flows in the middle-lower crust drive the rigid blocks to extrude and escape along the boundary faults, thus dominating the deformation of the lithosphere. The large-scale delamination of the continental lithosphere leads to upwelling of the asthenosphere along mechanically weak areas. Upwelling hot materials continue to heat the entire crust, and the expanding and diffusing lower crust further accelerates partial melting and plastic flow in the middle-lower crust.