Abstract
Summary Spatio-temporal variability in arc geochemistry and the conditions recorded by exhumed rocks suggest subduction zone thermal structure evolves in time and along-strike. Although much effort has been dedicated to studying subduction zone thermal structure, we lack an understanding of spatio-temporal temperature variability during time-dependent subduction. We model three-dimensional, dynamic subduction and examine the time evolution of the along-strike temperature difference of the slab’s upper surface (“slab-top”) at the center relative to the edge of the subduction zone. We examine this slab-top temperature variability for subduction systems of different widths and with different plate mobilities (i.e., fixed vs. free subducting and overriding plates). In all of our models, the main control on slab-top temperature is convergence rate; either by simply controlling the rate of slab sinking or via the effect it has on the decoupling depth (DD). In the early stages of subduction, more rapid convergence at the plate center produces a cooler slab relative to warmer slab edges. For mature subduction, this flips; a shallower DD at the slab center produces warmer temperatures with respect to the edge. Importantly, our maximum along-strike temperature changes are reduced (≤ 50○C) relative to previous kinematically-driven modeling studies, due to a reduced role for slab-top heating via toroidal flow. Our dynamic subduction models, therefore, point towards a strong time dependence in the sense of along-strike temperature variation, but with relatively low absolute values in geometrically simple subduction zones.
