Rheological heterogeneities of the upper plate control the deformation diversity in different continental collision systems along the Tethyan tectonic belt

Summary Continental collision is prevalent along the Tethyan tectonic belt, characterized by diverse deformation patterns across regions, including concentrated deformation in the Alps, integral deformation throughout the Tibetan Plateau, and separate deformation within the Iranian Plateau. However, the mechanisms governing the diversity of deformation in different collisional orogens along the Tethyan tectonic belt remain poorly understood. Accretion of continental terranes during the closure of the Paleo- and Neo-Tethys oceans generated a highly heterogeneous lithosphere along the southern margin of Eurasia, a crucial factor in interpreting continental deformation. This study employs 2D thermo-mechanical numerical modeling to assess how tectonic inheritance-induced rheological heterogeneities govern deformation patterns in continental collision orogens. Our simulation results reveal three end-member deformation patterns resulting from variations in the rheology of the upper plate within the collision system. When the upper plate is uniformly strong, it prevents deformation from propagating into the interior of the continent, resulting in concentrated deformation in the collision front. If the upper plate is uniformly weak, deformation occurs throughout the entire upper plate, resulting in an integral deformation pattern. When a rheologically weak block is embedded in the strong upper plate, deformation concentrates in the collision zone and the weak block, resulting in separate deformation within the upper plate. Changes in the rheology of the bounding plates, the convergence rate, and the total convergence amount would not alter the basic deformation pattern of the continental collision system, if the rheology of the upper plate remain unchanged. Based on our simulation results, we suggest that the rheological characteristics of the upper plate govern the deformation patterns in continental collision systems. Our simulation results provide first-order explanations for the observed diversity of deformation in different continental collision systems along the Tethyan tectonic belt.