Dynamics of crustal overthrust versus underthrust in the continental collision zones: Numerical modelling

Abstract

AbstractTrans‐plate crustal overthrust and underthrust are two unusual crustal architectures in nature, the mechanisms of which remain debated. Here, we construct a series of 2D numerical models to investigate the dynamics of trans‐plate crustal overthrust and underthrust. Model results indicate that the favourable conditions of crustal overthrust include low convergence rate, plastically strong crust, rheologically strong upper crust and hot subducting plate, which meanwhile contribute to the formation of ‘crocodile’ crustal structure. In contrast, a combination of a strong and buoyant subducting plate with a hot overriding plate facilitates crustal underthrust. The development of crustal overthrust shows no correlation with the subduction mode of lithospheric mantle, whereas crustal underthrust normally occurs in an advancing subduction system. Development conditions and crustal structures of the modelled overthrust and underthrust are consistent, on the first order, with the natural Dinarides orogen and the southern Tibetan plateau respectively.