Topography Response to Horizontal Slab Tearing and Oblique Continental Collision: Insights From 3D Thermomechanical Modeling.

The horizontal propagation of slab detachment (slab tearing) is known to control lateral migration of the mountain uplift along the collisional belt. However, along‐strike differential collision due to an oblique passive margin geometry can make the topography response more complex. In this study, we employ 3D thermomechanical modeling to distinguish between the lateral migration of the mountain topography driven by slab tearing and oblique continental collision itself. In our models, slab breakoff is triggered by the transition from oceanic to continental subduction, occurring earlier on one side of the passive margin than on the other due to the initial oblique configuration. However, once slab breakoff has begun, it spreads horizontally in the form of tearing at high velocity (∼38–118 cm yr−1), and associated topographic uplift also propagates with the same velocity. In contrast, the along‐strike migration of subsequent continental collision and related topographic uplift propagation is typically much slower (∼2–34 cm yr−1). Similarly, the vertical magnitude of surface uplift caused by slab tearing is higher (up to 10 mm yr−1) than the following collision phase (<4 mm yr−1). The parametric analysis reveals that slab tearing velocity and the associated horizontal propagation of mountain uplift depends on obliquity angle and slab age, whereas the migration of collision‐induced topographic growth is controlled by the convergence velocity and obliquity angle. Finally, we show that presence of microcontinental block detached from the passive margin leads to spatial and temporal transition from horizontal to vertical slab tearing and more intense syn‐collisional mountain building. Plain Language Summary: Continental collision begins after the complete subduction of the oceanic domain, initially located between the colliding continents. As the oceanic slab has negative buoyancy, it detaches from the positively buoyant continental plate shortly after the start of continental collision. Slab detachment leads to a rapid uplift of the surface topography and usually moves sideways, a process known as slab tearing. Slab tearing in turn results in a lateral propagation of the topographic uplift along the continental margin. However, if the colliding plate margins are initially at an angle to each other, an oblique continental collision occurs, which can also lead to along‐strike migration of the mountain uplift. To differentiate between the topography response to slab tearing and oblique continental collision, we have carried out 3D numerical modeling. Our parametric analysis reveals that the rate of slab tearing and the associated horizontal propagation of mountain uplift primarily depend on the angle of collisional obliquity and the age of the subducting oceanic slab, whereas the velocity of plate convergence controls the migration of collision‐induced topographic growth. Our findings also indicate that the surface uplift associated with slab tearing is more pronounced and spreads laterally much faster than during following oblique continental collision. Key Points: We explored numerically in 3D the topography response to horizontal slab tearing during retreating oblique continental collisionHorizontal slab tearing can initiate before collision due to the transition from oceanic to continental subduction below fore‐ and back‐arc domainSurface uplift associated with slab tearing is more pronounced and spreads laterally much faster than in the subsequent collision phase [ABSTRACT FROM AUTHOR]