georefid:2006-012381georefid:2006-012366SEDIS 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=2006-0123812004-01-01publicationgeorefid:2006-012381Banerjee, Neil R.University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, CanadaauthorHonnorez, JoseUniversity of Hawaii, United StatesauthorMuehlenbachs, KarlisUniversity of Oregon, United StatesauthorGeological Society of London, London, United KingdompublisherdocumentHardcopyIn: Fitton, J. Godfrey (editor), Mahoney, John J. (editor), Wallace, Paul J. (editor), Saunders, Andrew D. (editor), Origin and evolution of the Ontong Java Plateau229259-273We present a detailed mineralogical and petrological description of the low-temperature alteration patterns in basalts from four new sites drilled during ODP Leg 192 on the Early Cretaceous Ontong Java Plateau. Three main alteration types have been identified: pervasively altered dark grey basalt; black or dusky green halos; and brown halos. Dark grey basalts are the most common and represent the least intensive, but most pervasive, alteration phase. Early interaction of the basalt with low-temperature sea-water-derived hydrothermal fluids lead to the development of black and dusky green halos characterized by the replacement of groundmass and olivine phenocrysts by celadonitic phyllosilicates and smectite. Later interaction of basalts with cold oxidizing sea water produced brown halos characterized by replacement of primary phases and mesostasis by smectite and iron oxyhydroxides. Secondary minerals in order of decreasing abundance include phyllosilicates, calcite, iron oxyhydroxides, pyrite, chalcedony, quartz and zeolites. Veins, resulting from symmetrical infilling of open cracks, commonly contain phyllosilicates, iron oxyhydroxide or pyrite, and late calcite. Carbonate veins cross-cut all other alteration features and stable isotope analyses of vein carbonates indicate formation from marine bicarbonate below about 40 degrees C. A positive correlation between vein density and overall degree of alteration is observed resulting in pervasive development of brown alteration halos in highly fractured rocks. Overall, alteration of basalts from the Ontong Java Plateau is similar to that observed from other DSDP/ODP sites throughout the oceans.completedIgneous and metamorphic petrologySolid-earth geophysicsalterationbasaltsC-13/C-12carboncrustgeochemistryigneous rocksisotope ratiosisotopesLeg 130Leg 192low temperaturenesosilicatesO-18/O-16Ocean Drilling Programoceanic crustODP Site 1183ODP Site 1185ODP Site 1186ODP Site 1187ODP Site 807olivineolivine groupOntong Java PlateauorthosilicatesoxygenPacific Oceanpetrographysamplingsea-floor spreadingsecondary mineralssilicatesstable isotopestemperatureveinsvolcanic rocksWest Pacificurn:org.iodp:exp:130urnlargerWorkCitationcampaignurn:org.iodp:exp:192urnlargerWorkCitationcampaignurn:org.iodp:exp:192:site:1183urnlargerWorkCitationstudyurn:org.iodp:exp:192urnlargerWorkCitationcampaignurn:org.iodp:exp:192:site:1185urnlargerWorkCitationstudyurn:org.iodp:exp:192urnlargerWorkCitationcampaignurn:org.iodp:exp:192:site:1186urnlargerWorkCitationstudyurn:org.iodp:exp:192urnlargerWorkCitationcampaignurn:org.iodp:exp:192:site:1187urnlargerWorkCitationstudyurn:org.iodp:exp:192urnlargerWorkCitationcampaignurn:org.iodp:exp:130:site:807urnlargerWorkCitationstudyurn:org.iodp:exp:130urnlargerWorkCitationcampaignEnglishgeoscientificInformation155.0000165.0000-5.00005.0000