Thermal Structure and Metamorphic Evolution of Subducting Slabs

Subducting lithospheric plates are the cool, downwelling limbs of mantle convection and the negative buoyancy of subducting slabs (slab pull) drives plate tectonics [Forsyth and Uyeda, 1975]. Subduction zones are regions of intense earthquake activity, explosive volcanism, and complex mass transfer between the crust, mantle, hydrosphere, and atmosphere. In this contribution, I present subduction-zone thermal models that provide a framework for discussing the petrological and seismological processes that occur in subducting slabs (defined herein as the subducting sediments, oceanic crust, and oceanic mantle). Specific issues to be discussed include uncertainties regarding mantle-wedge convection, metamorphic reactions in the subducting plate, the origin of arc magmas, and subduction-zone earthquakes.