georefid:2001-000791georefid:2001-000779SEDIS Publication Catalogue

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http://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.168.004.20002000-01-01publicationgeorefid:2001-000791doi:10.2973/odp.proc.sr.168.004.2000Porter, SeanGeorgia State University, Department of Geology, Atlanta, GA, United StatesauthorVanko, David A.Geological Survey of Canada, CanadaauthorGhazi, A. MohamadOcean Drilling Program, United StatesauthorTexas A & M University, Ocean Drilling Program, College Station, TX, United StatespublisherdocumentDigitalIn: Fisher, Andrew T., Davis, Earl E., Firth, John V., Andersson, Eva M., Aoike, Kan, Becker, Keir, Brown, Kimberly A., Buatier, Martine D., Constantin, Marc, Elderfield, Henry, Goncalves, Carlos A., Grigel, Jens S., Hunter, Arlene G., Inoue, Atsuyuki, Lawrence, Roisin M., Macdonald, Robert D., Marescotti, Pietro, Martin, Jeffrey T., Monnin, Christophe, Mottl, Michael J., Pribnow, Daniel F. C., Stein, Joshua S., Su, Xin, Sun, Yue-Feng, Underwood, Michael B., Vanko, David A., Wheat, C. Geoffrey, Miller, Christine M. (editor), Peters, Lorri L. (editor), Proceedings of the Ocean Drilling Program, scientific results, hydrothermal circulation in the oceanic crust, eastern flank of the Juan de Fuca Ridge; covering Leg 168 of the cruises of the drilling vessel JOIDES Resolution, San Francisco, California, to Victoria, British Columbia, sites 1023-1032, 20 June-15 August 1996168149-157A drilling transect across the sedimented eastern flank of the Juan de Fuca Ridge, conducted during Leg 168 of the Ocean Drilling Program, resulted in the recovery of samples of volcanic basement rocks (pillow basalts, massive basalts, and volcanic glass breccias) that exhibit the effects of low-temperature hydrothermal alteration. Secondary clays are ubiquitous, with Mg-rich and Fe-rich saponite and celadonitic clays commonly accounting for several percent, and up to 10%-20% by volume. Present-day temperatures of the basement sites vary from 15 degrees to 64 degrees C, with the coolest site being about 0.8 Ma, and the warmest site being about 3.5 Ma. Whereas clays are abundant at sites that have been heated to present temperatures of 23 degrees C and higher, the youngest site at 15 degrees C has only a small trace of secondary clay alteration. Alteration increases as temperatures increase and as the volcanic basement ages. The chemical compositions of secondary clays were determined by electron microprobe, and additional trace element data were determined by both conventional nebulization inductively coupled plasma-mass spectroscopy (ICP-MS) and laser-ablation ICP-MS. Trioctahedral saponite and pyrite are characteristic of the interior of altered rock pieces, forming under conditions of low-oxygen fugacity. Dioctahedral celadonite-like clays along with iron oxyhydroxide and Mg-saponite are characteristic of oxidized haloes surrounding the nonoxidized rock interiors. Chemical compositions of the clays are very similar to those determined from other deep-sea basalts altered at low temperature. The variable Mg:Fe of saponite appears to be a systematic function both of the Mg:Fe of the host rock and the oxidation state during water-rock interaction.completedGeochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrologyalkaline earth metalsalterationbasaltsbasementchemical compositionclay mineralogyEast Pacificelectron probe datageochemistryhydrothermal alterationICP mass spectraigneous rocksironJuan de Fuca RidgeLeg 168low temperaturemagnesiummajor elementsmass spectrametalsmetasomatismmineral compositionNorth PacificNortheast PacificOcean Drilling ProgramPacific Oceanpillow structuresecondary mineralsspectratemperaturetrace elementsvolcanic rocksX-ray diffraction dataurn:org.iodp:exp:168urnlargerWorkCitationcampaignEnglishgeoscientificInformation-129.0000-127.300047.450048.0000application/pdfunknownSEDIS Publication Catalogue

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