Journal Article

Sharp thermal transition in the forearc mantle wedge as a consequence of nonlinear mantle wedge flow

Rychert, Catherine A., Wada, Ikuko, Wang, Kelin

2011

Overview

In the forearc mantle wedge, the thermal field depends strongly on slab‐driven mantle wedge flow. The flow is in turn affected by the thermal field via the temperature dependence of mantle rheology. Using thermal modeling, we show that the nonlinear feedback between the thermal and flow fields always leads to complete stagnation of the mantle wedge over a shallow, weakened part of the slab‐mantle interface and an abrupt onset of mantle flow further down‐dip. The abrupt increase in flow velocity leads to a sharp thermal transition from a cold stagnant to a hot flowing part of the wedge. This sharp thermal transition is inherent to all subduction zones, explaining a commonly observed sharp arc‐ward increase in seismic attenuation. Key Points The temperature dependence of mantle rheology causes nonlinear wedge flow The nonlinear wedge flow always results in a sharp thermal transition The thermal transition can explain the observed change in seismic attenuation

• Publisher: Blackwell Publishing Ltd,American Geophysical Union
• Subject: Earth sciences / Earth, ocean, space / Exact sciences and technology / mantle rheology / mantle wedge / seismic attenuation / subduction zone / thermal structure