Experimental Constraints on Volatiles in Subduction Zones

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9973066HollowayRegions on the Earth above subduction-zones are the location of almost all known explosive volcanoes. The explosivity is due to the presence of carbon dioxide and water (C02 and H20) dissolved in the magmas. This proposal is to continue the research we have been doing on the storage and release of the C02 and H20 that occur in subduction zones. Some of our work has centered on the determination of C02 solubility in a range of magma compositions, and on the effect of H20 on those solubilities. Other experiments have focused on the stability of water-containing minerals in subducting slabs. These results bear on a range of processes, but aim primarily at understanding aspects of subduction zone magmatism. The proposed research is to continue the work on subduction zone processes by (1) Experimentally determination of the pressure-temperature range for various hydrous minerals in hydrated basalt compositions under subduction zone conditions; and (2) Experimentally determining the beginning of melting and hornblende-out equilibria in hydrous mantle material at depths of 60 to 300 kilometers in the Earth. The experiments will be carried out by two Ph. D. students and will form the basis of their dissertations.