EFFECTS OF DOWNGOING SLAB ANGLE ON SUBDUCTION ZONE GEODYNAMICS: RESULTS FROM NUMERICAL MODELS

The geodynamics of subduction zones are controlled by many different parameters, including subduction angle, convergence rate, mantle viscosity structure, and the nature of the coupling between the downgoing slab and the mantle wedge. This study uses a series of two dimensional finite element models to assess how temperature and velocity fields are affected by subduction angle, for slabs ranging from relatively steep (~45° dip) to relatively flat (~10° dip). The model domain encompasses a downgoing slab, an overriding plate, and an intervening upper mantle wedge. The treatment of the frictional coupling between the uppermost portion of the downgoing slab and the mantle wedge is also varied as a secondary parameter. Models solve the steady-state equations of mass, momentum, and energy, neglecting heat production and thermal buoyancy and assuming isoviscous mantle flow. Flow in the wedge is driven by kinematic boundary conditions assigned to the downgoing slab. The rigid, overriding plate is assumed to be stationary. The resulting suite of models, which sweep over subduction angle parameter space, provide a generic framework for assessing convergent margin geodynamics in a variety of global geological settings.