Another goal of drilling was characterization of hydrothermal alteration of mantle peridotite and plutonic rocks to quantify chemical changes at a variety of temperatures. Systematic geochemical studies of samples with different extents and types of alteration will be necessary to discriminate between major and trace element features retained from igneous processes vs. those that are dominantly imposed during open system alteration. It is now recognized that a large proportion of slow-spreading lithosphere is composed of serpentinized peridotite, which is eventually subducted, but the composition of this geochemical reservoir is poorly characterized and understood. As for melt transport veins, discussed above in "Interpretation of Melt Transport Features in Mantle Peridotites," continuous core was used for detailed studies of the size/frequency and spatial distribution statistics of alteration veins. Postcruise analysis of these data will provide important information on the mechanisms of vein formation and fluid transport (e.g., Kelemen et al., 2000; Magde et al., 1995).
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