Figure 4. Estimates of H2O input and output fluxes for the Marianas subduction zone. Height of bar gives the flux for each parameter (scale on the left); bars are placed side-by-side to show competing estimates (as for Site 801 vs. Site 800 sediment) and are stacked to show cumulative input (on the right) and output (on the left). Shaded bars represent "continental" fluxes; unshaded bars are pristine igneous fluxes. Note that continental inputs and outputs may be very closely balanced; however, the balance depends critically on the real alteration fluxes for Hole 801C, which can only be constrained by further drilling. Cretaceous overprint given for both the East Mariana Basin (EMB) and Pigafetta Basins (PB); lines show fluxes resulting from different layer thickness.