georefid:2007-087882georefid:2007-087881SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.2204/iodp.proc.304305.101.20062005-01-01publicationgeorefid:2007-087882doi:10.2204/iodp.proc.304305.101.2006Blackman, Donna K.Scripps Institution of Oceanography, La Jolla, CA, United StatesauthorIldefonse, BenoitUniversite de Montpellier II, CanadaauthorJohn, Barbara E.University of Wyoming, United StatesauthorOhara, YasuhikoHydrographic and Oceanographic Department of Japan, JapanauthorMiller, D. JayIntegrated Ocean Drilling Program, United StatesauthorMacLeod, Christopher J.Cardiff University, United KingdomauthorEinaudi, FlorenceUniversity of Jena, Federal Republic of GermanyauthorAbratis, Michael W.Kanazawa University, JapanauthorAndal, Eric S.Institut de Physique du Globe de Paris, FranceauthorAndreani, MurielUniversity of Tokyo, JapanauthorAwaji, ShunsakuUniversity of Connecticut, United StatesauthorCharney, AllisonOregon State University, United StatesauthorChristie, DavidDuke University, United StatesauthorDrouin, MarionKyoto University, JapanauthorFrost, Bryce R.Woods Hole Oceanographic Institution, United StatesauthorGee, Jeffrey S.Hokkaido University, JapanauthorGodard, Marguerite M.University of Leeds, United KingdomauthorGrimes, Craig B.University of Plymouth, United StatesauthorHayman, Nicholas W.Tohoku University, JapanauthorHirose, TakehiroUniversity of Durham, United KingdomauthorHirth, James GregoryMax-Planck-Institut fuer Chemie, Federal Republic of GermanyauthorMaeda, JinichiroUniversity of Leicester, United KingdomauthorMcCaig, Andrew M.Japan Marine Science and Technology Center, JapanauthorMorris, AntonyVirginia Museum of Natural History, United StatesauthorNakagawa, TatsunoriLaboratoire Pierre Suee-DRECAM, FranceauthorSearle, Roger C.Eidgenoessiche Technische Hochschule Zuerich, Switzerlandauthorvon der Handt, AnetteUniversite Pierre et Marie Curie, FranceauthorDelius, HeikeUniversity of Hawaii at Manoa, United StatesauthorAbe, NatsueUniversity of Liverpool, United KingdomauthorBeard, James S.University of Bergen, NorwayauthorBrunelli, DanieleUniversity of Rhode Island, United StatesauthorDelacour, Adelie G.Lamont-Doherty Earth Observatory, United StatesauthorEscartin, JavierRheinisch-Westfaelische Technische Hochschule Aachen, Federal Republic of GermanyauthorFryer, Patricia B.Shizuoka University, JapanauthorHalfpenny, AngelaOkayama University, JapanauthorHansen, Heidi-ElisabethUniversitaet Koeln, Federal Republic of GermanyauthorHarris, Amber C.University of California, Santa Cruz, United StatesauthorHasebe, Akihiro TamuraUniversite de Montpellier II, FranceauthorHellebrand, EricUniversity of Wyoming, United StatesauthorIshimaru, SatokoHydrographic and Oceanographic Department of Japan, JapanauthorJohnson, Kevin T. M.Integrated Ocean Drilling Program, United StatesauthorKarner, Garry D.Cardiff University, United KingdomauthorLinek, MargaretUniversity of Jena, Federal Republic of GermanyauthorMason, Olivia U.Kanazawa University, JapanauthorMichibayashi, KatsuyoshiInstitut de Physique du Globe de Paris, FranceauthorNozaka, ToshioUniversity of Tokyo, JapanauthorRosen, MartinUniversity of Connecticut, United StatesauthorSuhr, GuenterOregon State University, United StatesauthorTominaga, MasakoDuke University, United StatesauthorYamasaki, ToruKyoto University, JapanauthorZhao, XixiWoods Hole Oceanographic Institution, United StatesauthorIODP Management International, Washington, DC, United StatespublisherdocumentDigitalIn: Blackman, Donna K., Ildefonse, Benoit, John, Barbara E., Ohara, Yasuhiko, Miller, D. Jay, MacLeod, Christopher J., Einaudi, Florence, Abratis, Michael W., Andal, Eric S., Andreani, Muriel, Awaji, Shunsaku, Charney, Allison, Christie, David, Drouin, Marion, Frost, Bryce R., Gee, Jeffrey S., Godard, Marguerite M., Grimes, Craig B., Hayman, Nicholas W., Hirose, Takehiro, Hirth, James Gregory, Maeda, Jinichiro, McCaig, Andrew M., Morris, Antony, Nakagawa, Tatsunori, Searle, Roger C., von der Handt, Anette, Delius, Heike, Abe, Natsue, Beard, James S., Brunelli, Daniele, Delacour, Adelie G., Escartin, Javier, Fryer, Patricia B., Halfpenny, Angela, Hansen, Heidi-Elisabeth, Harris, Amber C., Hasebe, Akihiro Tamura, Hellebrand, Eric, Ishimaru, Satoko, Johnson, Kevin T. M., Karner, Garry D., Linek, Margaret, Mason, Olivia U., Michibayashi, Katsuyoshi, Nozaka, Toshio, Rosner, Martin, Suhr, Guenter, Tominaga, Masako, Yamasaki, Toru, Zhao, Xixi, Oceanic core complex formation, Atlantis Massif; Expeditions 304 and 305 of the riserless drilling platform from and to Ponta Delgada, Azores (Portugal), Sites U1309-U1311, 17 November 2004-7 January 2005; and from and to Ponta Delgada, Azores (Portugal), Site U1309, 7 January-2 March 2005304/305Integrated Ocean Drilling Program Expeditions 304 and 305 composed a two-expedition program at Atlantis Massif, Mid-Atlantic Ridge 30 degrees N, designed to investigate the processes that control oceanic core complex formation and the exposure of ultramafic rocks in young oceanic lithosphere. Geophysical interpretations of unaltered mantle rock occurring <1 km below the seafloor suggested we could drill through an alteration front in ultramafic rocks and obtain fresh mantle peridotite. In order to accomplish these objectives, we drilled at two sites: one in the footwall through an exposed detachment fault and one in the hanging wall. Drilling the fractured basalt in the hanging wall was thwarted by difficulties, whereas drilling in the footwall was very successful. The main hole at Site U1309 penetrated 1415.5 meters below seafloor, and recovery averaged 75%. Igneous rocks recovered from the hole are the most primitive ever cored in slow-spreading ocean lithosphere and provide an exceptional record of magmatic and tectonic accommodation to extension in this environment. The core recovered was dominantly crustal rock types: basalt ( approximately 3%) and gabbroic ( approximately 91%). A series of olivine-rich rocks ( approximately 5%; dunites, wehrlites, troctolites), grouped as olivine-rich troctolites, part of which likely represent primitive cumulates, are interlayered with gabbroic rocks. A few thin mantle peridotite intervals are recognized in the upper 180 m of the section. Overall, the section is moderately altered at conditions ranging from granulite to zeolite facies. The rocks record initial alteration at low strains under granulite- and amphibolite-facies conditions and subsequent, more fully developed, lower temperature alteration (greenschist facies). Fault zone(s) comprising the detachment system must be highly localized to within tens of meters of the present-day seafloor. The existence of a fault at the top of the domal surface is supported by fragments of brecciated talc-tremolite fault schist and fractured metadiabase recovered in Hole U1309B and during the series of shallow cores drilled. Extensive amphibolite facies deformation is lacking, and high-strain ductile shear zones are rare. The absence of a thick, high-temperature ductile deformation zone in the footwall, and the apparent tectonic history (less rotation in the upper 180 m and variable rotations between several distinct, few-hundred meter sections downhole) suggested by paleomagnetic inclination measurements indicate complexity in structural evolution that differs from the simplest models of deep-rooted detachment faults, predicted to be associated with high-temperature deformation, and with constant or monotonically varying footwall rotation with depth. Another challenge is that the central dome is clearly not an uplifted dominantly upper mantle section, as had been inferred prior to drilling. The exposures of peridotite along the southern wall of Atlantis Massif, the geophysical results suggesting at least portions of the dome contain fresh olivine-rich rock, and the downhole variability at Site U1309 all likely indicate significant lateral heterogeneity over short distances across the footwall.completedIgneous and metamorphic petrologySolid-earth geophysicsAtlantic OceanAtlantis Massifbasaltsbody wavesboreholesBouguer anomalieschemical ratioscorescrustcumulatesdensitydiabasedrillingelastic wavesExpedition 304Expedition 305faciesfaultsgabbrosgeochemistrygeophysical methodsgeophysical profilesgeophysical surveysgravity anomaliesheat flowhydrothermal alterationigneous rocksIntegrated Ocean Drilling ProgramIODP Site 1309IODP Site 1310IODP Site 1311lithospheremagnetic propertiesmagnetic susceptibilitymagnetostratigraphymarine drillingmetamorphismmetasomatismMid-Atlantic Ridgemid-ocean ridgesmineral compositionNorth Atlanticoceanic crustoceanic lithosphereolivine gabbroP-wavespaleomagnetismperidotitespetrofabricspetrographypetrologyphysical propertiesplutonic rocksresistivityseismic methodsseismic profilesseismic stratigraphyseismic wavesseismogramsserpentinizationshear zonesspatial variationsstructural analysissurveyssynthetic seismogramsthermal conductivitythin sectionstroctoliteultramaficsveinsvelocityvolcanic rockswell logsurn:org.iodp:exp:304urnlargerWorkCitationcampaignurn:org.iodp:exp:305urnlargerWorkCitationcampaignurn:org.iodp:exp:304:site:U1309urnlargerWorkCitationstudyurn:org.iodp:exp:304urnlargerWorkCitationcampaignurn:org.iodp:exp:305:site:U1309urnlargerWorkCitationstudyurn:org.iodp:exp:305urnlargerWorkCitationcampaignurn:org.iodp:exp:304:site:U1310urnlargerWorkCitationstudyurn:org.iodp:exp:304urnlargerWorkCitationcampaignurn:org.iodp:exp:304:site:U1311urnlargerWorkCitationstudyurn:org.iodp:exp:304urnlargerWorkCitationcampaignEnglishgeoscientificInformation-42.0800-42.030030.100030.1200application/pdfunknownSEDIS Publication Catalogue

ana.macario@awi.de

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