ABSTRACT

This project has a research plan to examine the structure and speciation of a variety of impure aqueous fluids using a combination of spectroscopic techniques (particularly infrared spectroscopy) at high pressures and temperatures. Initial studies by the team will focus on halide- and carbonate-bearing water-rich systems to pressures near 10 GPa and temperatures of 600°C. These conditions are compatible with those associated with the slab-mantle interface within the planet, and thus with the dehydration of subducted oceanic crust and sediments. Such fluids are thus representative of the fluids that ultimately generate the initiation of hydrous melting associated with arc volcanism. The main scientific goals are to characterize the structural changes taking place within the water itself as a consequence of both impurities and high pressures and temperatures - changes that have been associated with marked shifts in the chemical behavior of aqueous solutions at high pressures - and to, where feasible, characterize the local bonding environment of the impurity itself. These studies hold the prospect for illuminating one of the most poorly understand features of the subduction process: the behavior of the fluids that ultimately give rise to subduction-related magmatism around the planet.

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