Textural implications of high-pressure fluid flow controlled by pre-subduction deformation and alteration patterns

Pillow lavas from the Corsican ophiolite (France) were metamorphosed to ecl ogite-facies conditions during the Alpine Orogeny. The mineralogical and te xtural evolution of these pillows, the patterns of fluid infiltration aroun d and through them, and their mechanical response to subduction zone metamo rphism and subsequent exhumation were primarily controlled by the pattern o f intrapillow fracturing that occurred during sub-seafloor alteration durin g much earlier crustal accretion. Primary rheological differences establish ed on the seafloor between pillow clasts and intrapillow fracture zones pla yed a fundamental role in controlling the extent of subduction-related flui d flow during Alpine Orogenesis in these units. (C) 2000 Elsevier Science B .V. All rights reserved.