An Integrated Study of Layer 3 of the Southwest Indian Ridge

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The oceanic crust is generally thought to grade downward from an extrusive layer of pillow lavas to an intruded sheeted dike complex underlain by gabbros and finally peridotites on the bottom. During Ocean Drilling Program Leg 118, 500 m of gabbro were cored in a single hole, Site 735B, located on a shallow (700 m) wave-cut summit of the eastern transverse ridge of the Atlantic II fracture zone in the southwest Indian Ocean. This is the most complete section of the gabbroic layer yet obtained and provides the opportunity to gain additional understanding of the magmatic processes responsible for the generation of the oceanic crust. This project will develop a structural, metamorphic and igneous stratigraphy, and obtain major, trace and rare-earth chemical analyses on the samples obtained from Site 735B.