The role of continental crustal strength in controlling deformation and P–T evolution during collision

A significant portion of deformation accommodated during continent–continent collision is localized within mechanically weak domains, particularly those inherited from earlier tectonic phases. While previous studies have highlighted the role of rift-inherited thermal and structural heterogeneities in controlling collision dynamics, the mechanical strength of the continental crust itself is expected to exert a first-order control on crustal accretion, burial, and exhumation processes. In particular, variations in crustal strength may strongly influence the pressure–temperature (P–T) evolution of accreted continental material during collision.

In this study, I investigate the effect of continental crustal strength on the thermo-mechanical evolution of accreted crust using two-dimensional geodynamic numerical modelling. I employ the finite-difference code Norma, using a fully staggered Eulerian grid coupled with a Lagrangian marker field to track material properties and P–T histories. The numerical experiments consist of an initial phase of lithospheric extension, followed by tectonic quiescence and subsequent convergence leading to continental collision. All experiments use an identical rifted margin architecture and thermal setup, while systematically varying the rheological strength of the continental crust.

The parametric study explores a range of crustal strength profiles depending on published crustal flow laws, thereby isolating the mechanical effect of crustal rheology on collision dynamics. The resulting models reveal pronounced differences in deformation style, crustal accretion mechanisms, and P–T paths of accreted crustal slivers. Weaker crust promotes distributed deformation, enhanced crustal thickening, and prolonged residence at mid- to lower-crustal pressures and temperatures, whereas stronger crust favors localized accretion, steeper burial trajectories, and more efficient exhumation along discrete shear zones.