Uplifts formation features in continental collision structures (evolution modeling)

Abstract

The investigation of collision structures is conducted based on the complex model of the thermal and mechanical evolution of overthrusting process for the rheologically layered lithosphere, which includes brittle upper crust and the lower crust and lithospheric upper mantle with different effective viscosity values. Finite element models with Lagrangian approach were used for the problem simulation. Horizontal shortening leads to the upper crust overthrusting along the fault zone, additional loading to the lower layers which is redistributed in the process of erosion of the uplift. These processes are compensated by ductile flow at the level of the lower crust and the upper mantle. The results of modeling of collision belts evolution during and after the convergence process have been compared for main governing parameters: shortening velocity (strain rate), viscosity contrast, erosion rate and dip angle of thrusting. The calculations with different erosion rates (0.25--5~mm/yr) show that this process has a weak effect on the postcollisional uplift evolution, which is governed mainly by the viscosity values of the lower crust and lithosphere upper mantle and initial geometry of the structure. But denudation results in surface exposure of metamorphic sequences, typical for thrust faults.