Modeling Deep Rooted Thrust Mechanism of Crustal Thickening in Eastern Tibet

Abstract

To test Eastern Tibet crustal thickening modes, we compare 2‐D numerical models of two emblematic end‐member models, with either an obstacle in the low viscosity lower crust or a thrust embedded in the high viscosity one. We show that the obstacle halts the viscous lower crustal flow potentially initiated by the weight of the high Central Tibet, generating a smooth exhumation gradient at the edge of the plateau, not observed in Eastern Tibet. On the contrary, including a low viscosity discontinuity in the upper crust, mimicking a shallow steep listric fault as inferred in the region, reproduces a sharper exhumation profile, as constrained from thermo‐kinematic inversions of thermochronological data, and the lack of foreland basin, as observed in the field. Moreover, such fault drives deformation throughout the entire crust, suggesting a deep crustal ductile shear zone limiting the more ductile deformation in the lower crust although no discontinuity is imposed.