georefid:2013-001301SEDIS 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=10.1016/j.gca.2012.08.0262012-01-01publicationgeorefid:2013-001301doi:10.1016/j.gca.2012.08.026Fliegel, DanielUniversity of Bergen, Department of Earth Science, Bergen, NorwayauthorKnowles, EmilyUniversity of Alberta, CanadaauthorWirth, RichardUniversity of Colorado at Boulder, United StatesauthorTempleton, AlexisGerman Research Centre for Geosciences, GermanyauthorStaudigel, HubertScripps Institution of Oceanography, United StatesauthorMuehlenbachs, KarlisauthorFurnes, HaraldauthorElsevier, New York, NY, InternationalpublisherdocumentHardcopyGeochimica et Cosmochimica Acta9680-93The habit, mineralogy, crystallography, and Fe speciation of tubular and granular alteration textures in basaltic glass recovered from DSDP Hole 418A, which have previously been associated with biologically mediated alteration, were investigated using an integrated suite of microscopic and spectroscopic approaches in order to shine light on their formation and mineralization history. Two different analytical approaches were used: (1) micro scale investigations with conventional petrographic optical microcopy and microscale X-ray fluorescence mapping and X-ray absorption spectroscopy, and (2) nano scale analyses with FIB (focused ion beam milling) to prepare cross-sections for TEM (transmission electron microscopy), EELS (electron energy loss spectroscopy), and STXM (scanning transmission electron microscopy) analyses. The integrated data show that tubular and granular textures are similar in chemical, mineralogical and structural habit. Both granular and tubular alteration textures show a marked transition from ferrous iron in the glass matrix to ferric iron in the textures. Granular and tubular textures are filled with sheet silicates of similar chemistry, and both exhibit thin amorphous alteration rims approximately 10-20 nm wide. The alteration rims are typically depleted in Ca and Fe. Ca is enriched at the contact between the secondary mineralization and the alteration rims, whereas Fe is enriched throughout the alteration features and is mainly present as Fe (super III) in contrast to Fe (super II) in the host glass. Carbon is enriched only in a few areas, and could possibly be of organic origin but is not bound in carbonate. The mineralization of the features follows the sequence: dissolution of the glass; formation of a leached amorphous rim; mineralizing the cavities by smectide type clays and subsequently congruent growing of the texture diameter by diffusing of the elements through the alteration layer. None of the features could be linked solely to a biogenic origin and hence the biogenicity of the textures can neither be refuted nor supported by this micro- and nano-scale data set. Abstract Copyright (2012) Elsevier, B.V.completedIgneous and metamorphic petrologyGeochemistry of rocks, soils, and sedimentsalterationAtlantic OceanbasaltsBermuda Risebiogenic processescharacterizationchemical compositionchemical fractionationclastic sedimentsclayCretaceouscrustDeep Sea Drilling ProjectDSDP Site 418igneous rocksIPODironlavaLeg 51Leg 52Leg 53Mesozoicmetalsmicroscope methodsnanoparticlesNorth AtlanticOcean Drilling Programoceanic crustoptical mineralogypillow lavasedimentsspectraTEM datatexturesvolcanic rocksX-ray fluorescence spectraX-ray spectraXANES spectraurn:org.iodp:exp:51urnlargerWorkCitationcampaignurn:org.iodp:exp:52urnlargerWorkCitationcampaignurn:org.iodp:exp:53urnlargerWorkCitationcampaignurn:org.iodp:exp:52:site:418urnlargerWorkCitationstudyurn:org.iodp:exp:52urnlargerWorkCitationcampaignurn:org.iodp:exp:53:site:418urnlargerWorkCitationstudyurn:org.iodp:exp:53urnlargerWorkCitationcampaignEnglishgeoscientificInformation-68.0327-68.032625.020525.0207Includes appendices