georefid:2012-034046SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2013-07-08T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.2204/iodp.sp.345.20122012-01-01publicationgeorefid:2012-034046issn:1932-9415doi:10.2204/iodp.sp.345.2012Gillis, KathrynUniversity of Victoria, School of Earth and Ocean Sciences, Victoria, BC, CanadaauthorSnow, Jonathan E.University of Houston, United StatesauthorKlaus, AdamTexas A&M University, United StatesauthorIODP Management International, College Station, TX, United StatespublisherdocumentDigitalScientific Prospectus (Integrated Ocean Drilling Program)34556 pp.1932-9415Integrated Ocean Drilling Program Expedition 345 (11 December 2012 to 10 February 2013) will be the second offset drilling program at the Hess Deep Rift to study crustal accretion processes at the fast-spreading East Pacific Rise (EPR). The expedition will take advantage of well-surveyed crustal exposures to recover the first cores of young, primitive plutonic rocks that comprise the lowermost ocean crust. The principal objective for drilling at Hess Deep is to test competing hypotheses of magmatic accretion and hydrothermal processes at fast-spreading mid-ocean ridges. These hypotheses make predictions that can only be tested with drill core, including the presence or absence of modally layered gabbro, the presence or absence of systematic variations in mineral and bulk rock compositions, and the extent and nature of hydrothermal alteration and deformation. With detailed petrological, chemical, and structural data for cores of deep, primitive gabbros, we will be able to address fundamental questions, such as, What proportion of the plutonic lower crust is constructed through crystal subsidence, and what proportion is constructed through in situ crystallization? How is melt transported from the mantle through the crust? What is the origin and significance of layering? How, and how fast, is heat extracted from the lower plutonic crust? What are the fluid and geochemical fluxes in the EPR lower plutonic crust? The highest priority for drilling at the Hess Deep Rift will be to sample one or more 100 to > or =250 m long sections of primitive gabbroic rocks. Three primary drill sites have been identified; however, if coring is proceeding well in the first or second of these sites, it will be continued as long as possible in order to obtain the longest possible continuous sample. The alternate site is located near Ocean Drilling Program Site 894, where shallow-level gabbros are exposed. This plan differs slightly from Proposal 551, as there is no alternate site in upper mantle peridotite. Drilling and coring operations are anticipated to be challenging during the Hess Deep expedition because of water depths >4800 m, a thin sediment cover, and, potentially, unstable basement formations.completedSolid-earth geophysicscrustdrillingEast PacificEast Pacific RiseExpedition 345fluid phasegabbrosgeochemistryHess Deepigneous rocksIntegrated Ocean Drilling Programmagmatismmarine drillingNorth PacificNortheast Pacificoceanic crustPacific Oceanplanningplutonic rockssea-floor spreadingwell-loggingEnglishgeoscientificInformation-101.3254-101.31332.15102.1803Includes appendicesapplication/pdfunknownSEDIS Publication Catalogue

ana.macario@awi.de

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