Relative role of slab tearing and oblique continental collision in along-strike mountain growth: Insights from 3D thermo-mechanical modeling

Slab tearing or the lateral propagation of slab break-off in collisional belts has been suggested to control progressive along-strike mountain uplift and adjacent foreland basin development. However, along-strike differential collision due to oblique and/or irregular passive margin geometry can introduce additional complexities, influencing the progressive topographic growth. In this study, we employ 3D thermo-mechanical numerical modeling approach to differentiate the topography growth driven by propagation of slab tearing from along-strike differential collision. We test several control parameters, which include (1) obliquity of the passive margin, (2) presence of the continental micro-block parallel to the original passive margin, (3) age of the subducting oceanic slab, and (4) velocity of the convergence between two colliding plates, in order to investigate the role of these key factors in the along-strike variable growth of the mountains. In our models, slab break-off is triggered by the transition from oceanic to continental subduction, which occurs earlier on one side of the passive margin than on the other due to its initial oblique configuration. However, once slab break-off begins, it spreads horizontally at extremely high speed and always reaches the opposite side of the former passive margin within a few Myr. Importantly, the along-strike migration of subsequent continental collision is typically much slower (~2-34 cm yr^-1) than slab tearing (~38-118 cm yr^-1). Similarly, the vertical magnitude of surface uplift caused by slab tearing is higher than during the following phase of continental collision (>4 mm yr^-1 and <4 mm yr^-1, respectively). The parametric analysis reveals that the slab tearing and the associated horizontal propagation of mountain uplift mainly depend on the obliquity of the passive margin and the age of the slab, whereas the migration of collision-induced topographic growth is expectedly controlled by the obliquity angle and the convergence velocity. Furthermore, our modeling reveals that the presence of microcontinental block separated from the passive margin during the previous phase of extension leads to spatial and temporal transition from horizontal to vertical slab tearing and to more intense syn-collisional mountain building. Finally, we demonstrate the applicability of our modeling results for understanding natural orogenic systems in the Alps, the Apennines, the Taiwan, and the Bismarck arc of Papua New Guinea.