Investigation ofFluid Flow in an Ancient Subduction Zone

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The nature of deformation hear the base of accretionary wedges likely involves extensive transport by fluids of silica and other components, brittle crack-seal veining and rock fabrics such as cleavage. However, estimates of the magnitude of fluid interactions and the scale over which they are operative is highly controversial. This project will examine the distribution, orientation, geometry, texture and geochemistry of quartz veins in a well-exposed and well-understood forearc complex on Afognak Island, Alaska. Coupled with measurements of volume change in wall rocks and oxygen isotopic analyses the plumbing system in rocks buried to depths of 8-12km will be reconstructed and used to infer the mechanisms of silica transport and the extent and nature of fluid flow near the base on an accretionary wedge. Results will be relevant to the study of accretionary, wedge development and to the study of the origins of rock deformation fabrics.