Sharp Ocean serpentinites contain a high concentration of water-soluble chlorides, and should be an important carrier responsible for removal of Cl from the exosphere as a source for high-salinity fluids in subduction zones. Four goals are proposed: 1) to better constrain the Cl content of serpentinites and their abundance by characterizing ODP cores and obducted equivalents, 2) to characterize the mineralogical siting of Cl - in serpentine using electron microbeam and TEM techniques, 3) to examine weakly and more highly-metamorphosed serpentinite bodies and associated wallrocks for evidence of high salinity fluids and their metamorphic/metasomatic effects and 4) measure chlorine isotope ratios of serpentinite and related lithologies in order to identify the origin of Cl. This work will include direct measurements of anion concentrations, salinity determinations of fluid inclusions, H, O and Cl isotope ratios, and evaluation of metasomatism in veins and shear zones as indirect evidence for element migration during passage of high-salinity fluids. Broader impacts - The integrated approach outlined in this proposal will lead to a better understanding of the importance of high-salinity fluids in deep subduction-related metamorphism, and the source of such fluids. The work will be carried out by the three PIs, a Ph.D. student and undergraduate (honor's thesis) and high school students (NASA SHARP summer internship). The project will include a large number of students at all levels, including minority high school students who will benefit from hands-on experience of a real scientific inquiry.
