An Integrated Study of Layer 3 of the Southwest Indian Ridge

大洋地壳通常被认为是从枕状熔岩的喷发层向下倾斜到辉长岩下面的侵入的席状岩墙杂岩，最后是底部的橄榄岩。在大洋钻探计划第118段，500米辉长岩被取心于位于印度洋西南部大西洋II断裂带东部横脊的浅(700米)波切割顶端的735B号单孔中。这是迄今获得的辉长岩层最完整的剖面，为进一步了解洋壳形成的岩浆过程提供了机会。该项目将开发构造、变质和火成岩地层学，并对从735B站点获得的样品进行主要、微量和稀土化学分析。

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.