Simple analytic model for subduction zone thermal structure

A new analytic model is presented for the thermal structure of subduction zones. It applies to the deeper regions of a subduction zone, where the overriding mantle is no longer rigid but flows parallel to the slab surface. The model captures the development of one thermal boundary layer out into the mantle wedge, and another into the subducting slab. By combining this model with the analytic model of Royden (1993a,b), which applies to regions in which the overriding plate is rigid, a nearly complete analytic model for the thermal structure of a steady-state subduction zone can be achieved. A good agreement is demonstrated between the output of the combined analytic model and a numerical finite element calculation. The advantages of this analytic approach include (1) efficiency (only limited computing resources are needed); (2) flexibility (non-linear slab shape, and processes such as erosion, and shear heating are easily incorporated); and (3) transparency (the effect of changes in input variables can be seen directly).