Intellectual Merit: This research addresses fundamental questions of the role of water in convergent plate margins requires by using geochemical indicators to determine the flux of fluids from a subducting plate and the stresses imposed by subduction affect the overriding plate's mantle. Samples mantle material erupted from serpentinite mud volcanoes on the Mariana forearc will be examined from sites 15 to 90 km from the trench and up to ~720 km along strike. Mineralogy and textures of the rocks will be examined quantitatively to determine the history and evolution of stress regimes in the forearc mantle. Middle-infrared (MIR) spectroscopy will be used to determine rough mineral percentages, with the data being verified by petrography. Micro-Raman mapping will be used to determine for detailed mineralogy. Electron backscatter diffraction will give orientation of olivine grains (microtextures reflect stress patterns in the forearc mantle). Selected samples will then be subjected to seismic velocity measurements to relate textural anisotropy and degree of serpentinization to seismic field measurements. This research provides the first integrated regional data set on the effects of serpentinization of natural samples and of evolution of strain in the forearc mantle. The data will allow better interpretation of geophysical field data and the controls on subduction-zone seismicity. The MIR data coupled with detailed petrographic and textural analysis will enable more accurate analysis of field samples and interpretation of remote sensing data.
Broader Impacts: This research has broad implication to large subduction zone fault studies, such as those on the San Andreas and Calvert faults. It will train both graduate and undergraduate students in the US, Japan and Canada. The work enhances the infrastructure for research and education by involving multidisciplinary research at three institutions. It also supports two female PIs, both of whom are at an EPSCoR institution (University of Hawaii). Results will be presented on the internet and on CD for informal and formal education for K-12 students, undergraduates, and the general public. The project will enhance the NSF-funded MARGINS-supported efforts in the Mariana region and ODP/IODP drilling in the Mariana forearc.
