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Research ArticlesDrilling to Gabbro in Intact Ocean Crust  
Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.
1 Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA.
2 National Oceanography Centre, Southampton, University of Southampton, SO14 3ZH, UK. 3 Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA. 4 Integrated Ocean Drilling Program, Texas A&M University, College Station, TX 77845, USA. 5 Department of Biology and Geosciences, Shizuoka University, Shizuoka 422–8529, Japan. 6 Department of Geology, Niigata University, Niigata 950–2181, Japan. 7 Department of Geology, University of California, Davis, CA 95616, USA. 8 Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305–8572, Japan. 9 Department of Geology, University of Leicester, Leicester LE1 7RH, UK. 10 Laboratoire de Géophysique et d'Hydrodynamique en Forage, Institut des Sciences de la Terre, de l'Environnement et de l'Espace de Montpellier, 34095 Montpellier, France. 11 Laboratoire de Géologie, École Normale Supérieure, 75231 Paris, France. 12 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331–5503, USA. 13 Institut Universitaire Européen de la Mer (IUEM), CNRS/UBO, F-29280, Plouzané, France. 14 Dipartimento per lo Studio del Territorio e delle sue Risorse, Università di Genova, 16132 Genova, Italy. 15 Department of Earth Sciences, Florida International University, Miami, FL 33199, USA. 16 Department of Earth Sciences, Università di Milano, 20133 Milano, Italy. 17 Department of Geosciences, University of Houston, Houston, TX 77204, USA. 18 Leibniz Institute for Marine Sciences Kiel, Instituts für Meereskunde–Forschungszentrums für Marine Geowissenschaften, 24148 Kiel, Germany. 19 Maritime Studies Program, Williams College and Mystic Seaport, Mystic, CT 06355, USA. 20 Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708, USA. 21 Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, HI 96822, USA. 22 Department of Geology and Geophysics/School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822, USA. 23 Graduate School of Environmental Studies, Tohoku University, Sendai 980–8579, Japan. 24 Department of Geology, University of St. Thomas, St. Paul, MN 55105, USA. 25 Department of Geological Sciences, Florida State University, Tallahassee, FL 32306–4100, USA. 26 Bundesanstalt für Geowissenschaften und Rohstoffe, 30655 Hannover, Germany. 27 Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, USA. 28 Institut für Mineralogie, Universität Hannover, 30167 Hannover, Germany. 29 Laboratoire de Pétrologie Magmatique, Université Paul Cézanne Aix-Marseille III, 13397 Marseille 20, France. 30 Department of Geoscience, University of Las Vegas, Las Vegas, NV 89154–4010, USA. 31 Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK. 32 School of Earth Sciences, University of Leeds, West Yorkshire LS2 9JT, UK. 33 Polar Research Institute, Incheon 406–840, Korea. 34 Department of Earth and Planetary Science, University of Tokyo, Tokyo 113–0033, Japan. 35 Department of Geology and Paleontology, The National Science Museum, Tokyo 169–0073, Japan. 36 Department of Earth and Planetary Sciences, Macquarie University, Sydney 2109, Australia. 37 Institut für Mineralogie und Geochemie, Universität Karlsruhe, 76131 Karlsruhe, Germany. 38 Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. 39 Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180–3590, USA. 40 Department of Oceanography, Texas A&M University, College Station, TX 77843–3146, USA. 41 Department of Earth and Planetary Sciences, Hokkaido University, Hokkaido 060–0810, Japan. 42 Department of Earth Sciences, Boston University, Boston, MA 02215, USA. * Ocean Drilling Program (ODP) Leg 206 Shipboard Scientific Party.
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Integrated Ocean Drilling Program (IODP) Expedition 309 Shipboard Scientific Party. 
IODP Expedition 312 Shipboard Scientific Party. 
To whom correspondence should be addressed. E-mail: Science. ISSN 0036-8075 (print), 1095-9203 (online)
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