The Role of Lithospheric-Deep Mantle Interactions on the Style and Stress Evolution of Arc-Continent Collision

We investigate how the mechanical properties of intra-oceanic arcs affect the collision style and associated stress-strain evolution with buoyancy-driven models of subduction that accurately reproduce the dynamic interaction of the lithosphere and mantle. We performed a series of simulations only varying the effective arc thickness as it controls the buoyancy of intra-oceanic arcs. Our simulations spontaneously evolve into two contrasting styles of collision that are controlled by a 3% density contrast between the arc and the continental plate. In simulations with less buoyant arcs (15–31 km; effective thickness), we observe arc-transference to the overriding plate and slab-anchoring and folding at the 660 km transition zone that result in fluctuations in the slab dip, strain-stress regime, surface kinematics, and viscous dissipation. After slab-folding occurs, the gravitational potential energy is dissipated in the form of lithospheric flow causing lithospheric extension in the overriding plate. Conversely, simulations with more buoyant arcs (32–35 km; effective thickness) do not lead to arc-transference and result in slab break-off, which causes an asymptotic trend in surface kinematics, viscous dissipation and strain-stress regime, and lithospheric extension in the overriding plate. The results of our numerical modeling highlight the importance of slab-anchoring and folding in the 660 km transition zone on increasing the mechanical coupling of the subduction system.