Origin and Emplacement of the Oceanic Core Complex at IODP Site 735

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Under this award, the PIs will analyze videotapes, still camera images, and do petrography of dredge, rock drill, and dive samples from 5 site survey cruises to the Atlantis Bank Oceanic Core Complex on the SW Indian Ridge. They will complete the shore based analysis of the field programs and synthesize the data to publish a geologic map, and interpretive cross-sections documenting the stratigraphy, and emplacement the complex. The site is located adjacent to the Atlantis II F.Z. on 11 My old crust exposing a 400 km2 lower crustal gabbro massif in contact with the mantle along the transform wall. It is the location of 1.5 km deep ODP Hole 735B, the only deep hole in the lower ocean crust, and the location of a pending IODP proposal for a new hole to 3 km. The work will provide the geological context for the drilling and tests of ideas on the structure and lithology of ocean crust.