Complex mantle flow around heterogeneous subducting oceanic plates

The foundering of oceanic lithospheres controls the circulation patterns of the mantle around subducting slabs. Here, we investigate the sensitivity of the mantle flow to slab buoyancy variations along convergent margins using three-dimensional numerical models of subduction in a viscous mantle. The models illustrate that in a buoyancy-driven system varying subduction velocity arising from negative buoyancy variations effectively drives pressure gradients and confers a general flow component sub-parallel to the margin s strike, allowing for material transport over large distances around the slabs. The along-slab velocity component introduces widespread horizontal simple shear in the mantle flow which is maximized beneath the slab between similar to 100 and similar to 350 km. Mantle flow complexities develop rapidly, although not instantaneously, upon subduction of heterogeneous plates.