Insights into slab detachment dynamics from 0D to 3D numerical 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). The negative buoyancy force associated with a slab at depth and its progressive removal during detachment results in a reorganization of forces within the lithosphere and the detaching slab. However, it is not yet clear to which extent slab detachment is the primary cause of the different observations. Deciphering the impact of slab detachment on the observations mentioned above therefore requires a thorough understanding of the physical processes controlling deformation within and around the detaching slab. 

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 difficult to pinpoint the first order controls on the time scale of this process. As a first step, we therefore develop a simplified 0D necking model that describes the temporal evolution of the thickness of a detaching slab, additionally taking into account the effects of the nonlinear coupling between upper mantle and detaching slab. This allows us to derive a set of nondimensional numbers which ultimately control the slab detachment process.  

Based on these findings, we then use 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 the 2D and 3D experiments sufficiently well if simple slab geometries are used. 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 efficiently determine first order controls on slab detachment and thus also on specific geological observations such as seismicity and surface response.