On the possibility of a steady state backflow in the mantle wedge

Abstract

Viscous coupling between the subducting slab and the overriding mantle wedge may drive a corner flow in the forearcs and, consequently, may affect the temperature in the mantle wedge. We developed a numerical model of a generic pseudo-plastic subduction plate, in which the steady-state thermal structure of the mantle wedge is calculated without any a priori assumptions on the geometry of the subducting slab. The results showed that both the temperature field and the geometry of the slab are strongly controlled by weakness zones in the topmost part of the subducting plate and in the cold tip of the mantle wedge. We showed that a backward flow may evolve along the plate-wedge interface if the cold portion of the mantle wedge is weak, which, likely, is true as this region is hypothesized to be strongly serpentinized. We concluded that the self-consistent generation of the plate geometry should be addressed in the kinematic subduction models because such a strongly non-linear system may lead to unforseen effects. © 2009 The Authors Journal compilation © 2009 RAS.