The investigators will use the chemistry of fluids rising through mud volcanoes on the Mariana forearc to infer pressure-temperature and chemical conditions at the top of the subducting slab, to constrain processes in the shallow subduction zone, and to estimate mass fluxes through the Mariana forearc resulting from this process. They will do this by 1) thermodynamic modeling of water-rock interaction under a range of blueschist-facies conditions beneath the forearc, for both sediment and basalt, using the observed spring compositions and recovered metamorphic rocks as constraints; 2) modeling of the progressive reaction of these metamorphic fluids with harzburgite during their ascent; and 3) comparing the composition of subducting oceanic basalt and sediment with fluxes represented by the springs and the ascending serpentinite.
