• Login
    About WHOAS
    View Item 
    •   WHOAS Home
    • Woods Hole Oceanographic Institution
    • Geology and Geophysics (G&G)
    • View Item
    •   WHOAS Home
    • Woods Hole Oceanographic Institution
    • Geology and Geophysics (G&G)
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of WHOASCommunities & CollectionsBy Issue DateAuthorsTitlesKeywordsThis CollectionBy Issue DateAuthorsTitlesKeywords

    My Account

    LoginRegister

    Statistics

    View Usage Statistics

    Observations of Li isotopic variations in the Trinity Ophiolite : evidence for isotopic fractionation by diffusion during mantle melting

    Thumbnail
    View/Open
    Author's final draft (228.5Kb)
    Figures (1.581Mb)
    Date
    2004-08-10
    Author
    Lundstrom, Craig C.  Concept link
    Chaussidon, Marc  Concept link
    Hsui, Albert T.  Concept link
    Kelemen, Peter B.  Concept link
    Zimmerman, Mark  Concept link
    Metadata
    Show full item record
    Citable URI
    https://hdl.handle.net/1912/775
    As published
    https://doi.org/10.1016/j.gca.2004.08.004
    Abstract
    The Trinity peridotite (northern CA) contains numerous lithologic sequences consisting of dunite to harzburgite to spinel lherzolite to plagioclase lherzolite. Previous workers have documented geochemical gradients in these sequences consistent with melt-rock reaction processes occurring around dunites, interpreted to reflect conduits for melt ascent. We have undertaken a study of Li isotope compositions of clinopyroxene and some olivine within these sequences using ion probe techniques in order to test the hypothesis that the geochemical gradients are related to diffusive fluxing of alkali elements into or away from the melt conduit. Results show large variations in 7Li/6Li occurring in a consistent pattern across three transects from dunite to plagioclase lherzolite within the Trinity peridotite. Specifically, measurements of average δ7Li for single thin sections along the traverse reveal a low in δ7Li in the harzburgite adjacent to the dunite returning to higher values farther from the dunite with a typical offset of ~10 per mil in the low δ7Li trough. This pattern is consistent with a process whereby Li isotopes are fractionated during diffusion through a melt either from the dunite conduit to the surrounding peridotite, or from the surrounding peridotite into the dunite conduit. The patterns in 7Li/6Li occur over a length scale similar to the decrease in REE concentration in these same samples. Explaining both the trace element and Li isotopic gradients requires a combined process of alkali diffusion and melt extraction. We develop a numerical model and examine several scenarios of the combined diffusion-extraction process. Using experimentally constrained values for the change in Li diffusion coefficient with isotope mass, large changes in δ7Li as a function of distance can be created in year to decade time scales. The addition of the melt extraction term allows larger Li concentration gradients to be developed and thus produces larger isotopic fractionations than diffusion only models. The extraction aspect of the model can also account for the observed decrease in rare earth element concentrations across the transects.
    Description
    Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 69 (2005) 735-751, doi:10.1016/j.gca.2004.08.004.
    Collections
    • Geology and Geophysics (G&G)
    Suggested Citation
    Preprint: Lundstrom, Craig C., Chaussidon, Marc, Hsui, Albert T., Kelemen, Peter B., Zimmerman, Mark, "Observations of Li isotopic variations in the Trinity Ophiolite : evidence for isotopic fractionation by diffusion during mantle melting", 2004-08-10, https://doi.org/10.1016/j.gca.2004.08.004, https://hdl.handle.net/1912/775
     

    Related items

    Showing items related by title, author, creator and subject.

    • Thumbnail

      Assessing the blank carbon contribution, isotope mass balance, and kinetic isotope fractionation of the Ramped Pyrolysis/Oxidation instrument at NOSAMS 

      Hemingway, Jordon D.; Galy, Valier; Gagnon, Alan R.; Grant, Katherine E.; Rosengard, Sarah Z.; Soulet, Guillaume; Zigah, Prosper; McNichol, Ann P. (2017-03)
      We estimate the blank carbon mass over the course of a typical Ramped PyrOx (RPO) analysis (150 to 1000 °C; 5 °C×min-1) to be (3.7 ± 0.6) μg C with an Fm value of 0.555 ± 0.042 and a δ13C value of (-29.0 ± 0.1) ‰ VPDB. ...
    • Thumbnail

      N isotopic composition of Phenylalanine and Glutamic Acid from a number of organisms, demonstrating new HPLC protocol for precise isotopic measurements 

      McCarthy, Matthew D. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-08-02)
      N isotopic composition of Phenylalanine and Glutamic Acid from a number of organisms, demonstrating new HPLC protocol for precise isotopic measurements. For a complete list of measurements, refer to the full dataset ...
    • Thumbnail

      N isotopic composition of Phenylalanine and Glutamic Acid from a number of organisms, demonstrating new HPLC protocol for precise isotopic measurements 

      McCarthy, Matthew D. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-08-02)
      N isotopic composition of Phenylalanine and Glutamic Acid from a number of organisms, demonstrating new HPLC protocol for precise isotopic measurements. For a complete list of measurements, refer to the full dataset ...
    All Items in WHOAS are protected by original copyright, with all rights reserved, unless otherwise indicated. WHOAS also supports the use of the Creative Commons licenses for original content.
    A service of the MBLWHOI Library | About WHOAS
    Contact Us | Send Feedback | Privacy Policy
    Core Trust Logo