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Li and Li isotopic composition of hydrothermally altered sediments at Middle Valley, Juan De Fuca

Decitre, Sylvie; Buatier, Martine and James, Rachael (2004). Li and Li isotopic composition of hydrothermally altered sediments at Middle Valley, Juan De Fuca. Chemical Geology, 211(3-4) pp. 363–373.

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Li and Li isotopes have been measured in the clay fraction of sediments recovered from the Middle Valley hydrothermal site on the Juan De Fuca Ridge. The Li content of pure detrital clays is 51 ppm while hydrothermal clays and carbonates have lower Li (22±11 ppm). However, there is no clear relationship between the mineralogy of the hydrothermal alteration products and their Li content. The δ7 Li value of the detrital clays is +5.8‰. Hydrothermal clays and carbonates have δ7 Li in the range of -3.9‰ to +7.8‰; these values do not seem to be dependent on the temperature at which they formed. Modelling of the Li and Li isotope systematics indicates that the fluid from which the alteration products form is significantly enriched in Li (higher than 10,000 μmol kg-1) relative to pore fluids recovered from within the sediments (up to 589 μmol kg-1; [Wheat, C.G., M.J. Mottl, 1994. Data report: trace metal composition of pore water from Sites 855 through 858, Middle valley, Juan De Fuca Ridge. In Mottl, M.J., Davis, E.E., Fisher, A.T., Slack, J.F. (Eds.), Proc. ODP, Sci. Res. 139: 749–755]), and that this Li is derived from sediment. Thus, the alteration products are not in equilibrium with their conjugate pore fluids; rather, the alteration minerals formed at lower water/sediment ratios. This suggests that fluid flow pathways at Middle Valley were more diffuse in the past than they are today

Item Type: Journal Item
Copyright Holders: 2004 Elsevier B.V.
ISSN: 0009-2541
Keywords: Juan de Fuca Ridge; ODP Leg 139; Isotopes; Lithium; Hydrothermal alteration; Oceanic sediments
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 10487
Depositing User: Rachael James
Date Deposited: 31 Mar 2008
Last Modified: 04 Oct 2016 10:08
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