georefid:2007-087746georefid:2007-087742SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.209.005.2007<gco:CharacterString>Hybridization of dunite and gabbroic materials in Hole 1271B from Mid-Atlantic Ridge 15 degrees N; implications for melt flow and reaction in the upper mantle</gco:CharacterString>2007-01-01publicationgeorefid:2007-087746doi:10.2973/odp.proc.sr.209.005.2007Takazawa, EiichiNiigata University, Department of Geology, Niigata, JapanauthorAbe, NatsueWoods Hole Oceanographic Institution, United StatesauthorSeyler, MoniqueOcean Drilling Program, United StatesauthorMeurer, William P.University of Houston, United StatesauthorTexas A&M University, Ocean Drilling Program, College Station, TX, United StatespublisherdocumentDigitalIn: Kikawa, Eiichi, Kelemen, Peter B., Miller, D. Jay, Abe, Natsue, Bach, Wolfgang, Carlson, Richard L., Casey, John F., Chambers, Lynne M., Cheadle, Michael, Cipriani, Anna, Dick, Henry J. B., Faul, Ulrich, Garces, Miguel, Garrido, Carlos J., Gee, Jeffrey S., Godard, Marguerite M., Graham, David W., Griffin, Dale W., Harvey, Jason, Ildefonse, Benoit, Iturrino, Gerardo J., Josef, Jennifer A., Meurer, William P., Paulick, Holger, Rosner, Martin, Schroeder, Timothy, Seyler, Monique, Takazawa, Eiichi, Proceedings of the Ocean Drilling Program; scientific results; drilling mantle peridotite along the Mid-Atlantic Ridge from 14 degrees to 16 degrees N; covering Leg 209 of the cruises of the drilling vessel JOIDES Resolution; Rio de Janeiro, Brazil, to St. George, Bermuda; Sites 1268-1275; 6 May-6 July 2003209Dunite and gabbroic materials recovered from Hole 1271B, Ocean Drilling Program (ODP) Leg 209, were examined for mineral chemistry to understand melt flow and melt-mantle reactions in the shallowest upper mantle of the Mid-Atlantic Ridge near the 15 degrees 20' Fracture Zone. Hole 1271B was drilled to 103.8 meters below seafloor on the inner corner high along the south wall of the 15 degrees 20' Fracture Zone. The total length of core collected was 15.9 m (recovery = approximately 15%). The dominant rock type in Hole 1271B is dunite, followed by brown amphibole gabbro, olivine gabbro, and troctolite, along with minor amounts of harzburgite and olivine gabbronorite. A large proportion of the dunite is associated with gabbroic rocks in Hole 1271B, similar to those observed in the Mohorovicic (Moho) transition zone of the Oman ophiolite, indicating significant magmatic activity in this region near the 15 degrees 20' Fracture Zone. Olivine Fo content varies from 89.2 to 91.2 in impregnated dunite and from 85.6 to 88.6 in troctolite, olivine gabbro, and olivine gabbronorite. Spinel Cr# (= 100XCr/[Cr+Al] molar ratio) ranges from 38.9 to 62.7 in dunite and from 46.3 to 57.6 in troctolites, olivine gabbro, and olivine gabbronorite. Compositional trends for spinel from dunite through troctolite toward olivine gabbro/gabbronorite are characterized by increases in TiO (sub 2) , Cr#, and Fe (super 3+) #, very similar to those reported from Hess Deep Site 895. Olivine gabbro, olivine gabbronorite, and troctolite in Hole 1271B are considered to have formed as hybrid rocks between dunite and an evolved melt in the walls of a melt channel in the shallowest upper mantle that is tens of meters wide. The melt trapped in the wall rock crystallized plagioclase and clinopyroxene. On the other hand, dunite in the center of the melt channel became more refractory by melt-mantle reactions, increasing spinel Cr# to 62.5.completedIgneous and metamorphic petrologyGeochemistry of rocks, soils, and sedimentsamphibole groupAtlantic Oceanboreholeschain silicateschemical ratioscoresdunitegabbrosgeochemistryharzburgitehybridizationigneous rocksLeg 209magmasmantlemeltsMid-Atlantic Ridgemineral compositionmodelsnesosilicatesNorth AtlanticOcean Drilling ProgramODP Site 1271olivineolivine gabbroolivine grouporthosilicatesoxidesperidotitespetrographyplutonic rockssilicatesspatial variationsspineltroctoliteultramaficsupper mantleurn:org.iodp:exp:209urnlargerWorkCitationcampaignurn:org.iodp:exp:209:site:1271urnlargerWorkCitationstudyurn:org.iodp:exp:209urnlargerWorkCitationcampaignEnglishgeoscientificInformation-44.5700-44.570015.020015.0200application/pdfunknownSEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContacthttp://www-odp.tamu.edu/publications/209_SR/VOLUME/CHAPTERS/005.PDFdownload