Effects of upper mantle drag on slab detachment dynamics: insights from 0D and 3D experiments

Slab detachment is a process that has been invoked to explain rapid uplift, deep seismicity, and magmatic activity in several active orogens (e.g., Alps, Himalaya). However, it is not yet clear to which extent slab detachment is the primary cause of these phenomena. Thus, deciphering the physical processes controlling the slab break-off is important to understand its impact on the post-collisional evolution of orogens.

Here, we employ numerical models to investigate the nonlinear coupling between mantle flow and slab detachment. Due to the three-dimensional nature of slab detachment and the variety of involved processes, it is daunting to pinpoint the first order controls on the time scale of this process. We, therefore, started to investigate this issue by developing a 0D necking model that describes the temporal evolution of the thickness of a detaching slab. We accounted for the effects of the nonlinear coupling between upper mantle and detaching slab and derived a set of nondimensional numbers that control the slab detachment process.

Based on these findings, we, then, used 2D and 3D numerical models to further determine higher dimensional geometrical effects on slab detachment. Results show that the predictions from the 0D experiments predict simple 2D and 3D experiments sufficiently well. For more complex slab geometries, higher dimensional results deviate from the 0D predictions. Nevertheless, the combination of 0D and 2D/3D numerical models allows to determine first order controls on slab detachment and thus also on specific geological observations such as seismicity and surface response.