Intellectual Merit. The process of mantle melting and the generation of lavas are strongly influenced by H2O, but water plays apparently different roles depending on tectonic setting. This research addresses the role of water in the melting regime of a normal mid-ocean ridge far from the influence of subduction or plumes, as well as in ridges influenced by subduction. Hypotheses will be tested with geochemical analyses of mid-ocean ridge and back-arc basin basalt glasses that are already in-hand. This study will use the ion probe (SIMS) to develop high-spatial-resolution data sets of volatile (e.g., H2O, CO2, etc.) and trace elements for glasses from lavas from two seafloor spreading regimes: a normal mid-ocean ridge (East Pacific Rise) and four back-arc basins that transition between ridge and subduction zone systematics (the Woodlark, N. Fiji, Manus and Northern Lau basins). Using the data, a comprehensive model of the influence of H2O on the melting processes beneath normal mid-ocean ridges will be developed using MELTS. The model will then be tested within the framework of the four back-arc basins. Results ultimately should lead to a clearer model of how H2O influences the mantle melting process, how mantle temperature and volatile contents impact the composition and structure of the oceanic crust, and how H2O is distributed and transported throughout the earth's upper mantle. Broader Impacts. This research supports an early career female PI at the University of Rhode Island, which is in an EPSCoR state. The project also fosters national and international collaboration and supports one graduate student who will gain unique, hands-on analytical and modeling experience. Summer undergraduate interns will also be engaged in the research through an NSF REU program. The work is compatible with the NSF-funded RIDGE science plans and objectives.
