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

Li and Li isotopic composition of hydrothermally altered sediments at Middle Valley, Juan De Fuca
Li and Li isotopic composition of hydrothermally altered sediments at Middle Valley, Juan De Fuca
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 δ7Li value of the detrital clays is +5.8‰. Hydrothermal clays and carbonates have δ7Li 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.
Juan de Fuca Ridge, ODP Leg 139, Isotopes, Lithium, Hydrothermal alteration, Oceanic sediments
0009-2541
363-373
Decitre, S.
9c111a6a-4db6-45d0-8c83-7786f40280e5
Buatier, M.
3ff8d05d-4cab-47d1-8b13-13fc5c026516
James, R.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Decitre, S.
9c111a6a-4db6-45d0-8c83-7786f40280e5
Buatier, M.
3ff8d05d-4cab-47d1-8b13-13fc5c026516
James, R.
79aa1d5c-675d-4ba3-85be-fb20798c02f4

Decitre, S., Buatier, M. and James, R. (2004) Li and Li isotopic composition of hydrothermally altered sediments at Middle Valley, Juan De Fuca. Chemical Geology, 211 (3-4), 363-373. (doi:10.1016/j.chemgeo.2004.07.005).

Record type: Article

Abstract

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 δ7Li value of the detrital clays is +5.8‰. Hydrothermal clays and carbonates have δ7Li 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.

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More information

Published date: 2004
Keywords: Juan de Fuca Ridge, ODP Leg 139, Isotopes, Lithium, Hydrothermal alteration, Oceanic sediments
Organisations: Marine Geoscience

Identifiers

Local EPrints ID: 210105
URI: http://eprints.soton.ac.uk/id/eprint/210105
ISSN: 0009-2541
PURE UUID: 4b23b421-a3d3-45da-951a-973e90aa1e2e
ORCID for R. James: ORCID iD orcid.org/0000-0001-7402-2315

Catalogue record

Date deposited: 06 Feb 2012 13:27
Last modified: 10 Jul 2020 00:30

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