The goal of this project is integration of thermal and kinetic models with seismological data for subduction zones that exhibit seismological evidence for sluggish transformation of basalt and gabbro to eclogite. The PIs begin by producing a kinematic thermal model that yields transient and steady-state thermal structures and the pressure-temperature-time evolution of the subducting slab and overlying mantle wedge. Next, equilibrium and kinetic phase transformation models are used to predict mineral assemblages, densities, and seismic wave speeds. The calculated velocity structure is then evaluated by its ability to predict observed seismic properties of waveform dispersion and converted phase amplitudes. Misfit between the petrologically predicted and the seismologically observed velocity structure is then minimized by iterative repetition. If the assumption is made that high fluid pressures are required for intermediate depth earthquakes, then the loci of dehydration reactions and the resultant volatile flux can also be used to predict hypocenter locations and compared to observed earthquake hypocenters. The resulting integrated model of the thermal, petrological, and seismological properties of subducting slabs will yield further insight into other plate boundary processes such as intermediate-depth earthquakes, arc magmatism, and the recycling of volatiles.
