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Isotopic signature of dissolved iron delivered to the Southern Ocean from hydrothermal vents in the East Scotia Sea

Klar, Jessica K.; James, Rachael H.; Gibbs, Dakota; Lough, Alastair; Parkinson, Ian; Milton, J. Andrew; Hawkes, Jeffrey A.; Connelly, Douglas P.. 2017 Isotopic signature of dissolved iron delivered to the Southern Ocean from hydrothermal vents in the East Scotia Sea. Geology, 45 (4). 351-354. 10.1130/G38432.1

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Copyright © 2016 Geological Society of America This document is the author’s final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. Some differences between this and the publisher’s version remain. You are advised to consult the publisher’s version if you wish to cite from this article. The definitive version is available at http://www.gsapubs.org/
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Abstract/Summary

It has recently been demonstrated that hydrothermal vents are an important source of dissolved Fe (dFe) to the Southern Ocean. The isotopic composition (?56Fe) of dFe in vent fluids appears to be distinct from other sources of dFe to the deep ocean, but the evolution of ?56Fe during mixing between vent fluids and seawater is poorly constrained. Here we present the evolution of ?56Fe for dFe in hydrothermal fluids and dispersing plumes from two sites in the East Scotia Sea. We show that ?56Fe values in the buoyant plume are distinctly lower (as low as ?1.19 ‰) than the hydrothermal fluids (?0.29 ‰), attributed to (i) precipitation of Fe-sulfides in the early stages of mixing, and (ii) partial oxidation of Fe(II) to Fe(III), > 55 % of which subsequently precipitates as Fe-oxyhydroxides. By contrast, the ?56Fe signature of stabilized dFe in the neutrally buoyant plume is ?0.3 to ?0.5 ‰. This cannot be explained by continued dilution of the buoyant plume with background seawater; rather, we suggest that isotope fractionation of dFe occurs during plume dilution due to Fe ligand complexation and exchange with labile particulate Fe. The ?56Fe signature of stabilized hydrothermal dFe in the East Scotia Sea is distinct from background seawater and may be used to quantify the hydrothermal dFe input to the ocean interior.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1130/G38432.1
ISSN: 0091-7613
Date made live: 16 Dec 2016 11:19 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/515538

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