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

Isotopic signature of dissolved iron delivered to the Southern Ocean from hydrothermal vents in the East Scotia Sea
Isotopic signature of dissolved iron delivered to the Southern Ocean from hydrothermal vents in the East Scotia Sea
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.
0091-7613
351-354
Klar, Jessica K.
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James, Rachael H.
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Gibbs, Dakota
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Lough, Alastair
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Parkinson, Ian
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Milton, J. Andrew
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Hawkes, Jeffrey A.
19e298a9-b5bf-4987-bfea-07780ca5bd69
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8
Klar, Jessica K.
3beaa216-b22d-43f3-8a1b-9683c949939b
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Gibbs, Dakota
a33a8182-5e94-4c4b-8645-59bc4d44f7c8
Lough, Alastair
64be5e9d-9ca2-438c-b566-cfee88ff1a37
Parkinson, Ian
fbf4a823-b4fd-465e-921e-772b342d0d10
Milton, J. Andrew
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Hawkes, Jeffrey A.
19e298a9-b5bf-4987-bfea-07780ca5bd69
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8

Klar, Jessica K., James, Rachael H., Gibbs, Dakota, Lough, Alastair, Parkinson, Ian, Milton, J. Andrew, Hawkes, Jeffrey A. and 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. (doi:10.1130/G38432.1).

Record type: Article

Abstract

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.

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Accepted/In Press date: 13 December 2016
e-pub ahead of print date: 7 February 2017
Published date: 1 April 2017
Organisations: Geochemistry, Marine Geoscience

Identifiers

Local EPrints ID: 403962
URI: http://eprints.soton.ac.uk/id/eprint/403962
ISSN: 0091-7613
PURE UUID: 0df70e76-a6e3-4bec-9c2c-7d6c85f05cee
ORCID for Rachael H. James: ORCID iD orcid.org/0000-0001-7402-2315
ORCID for J. Andrew Milton: ORCID iD orcid.org/0000-0003-4245-5532

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Date deposited: 16 Dec 2016 10:24
Last modified: 16 Mar 2024 03:57

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Contributors

Author: Jessica K. Klar
Author: Dakota Gibbs
Author: Alastair Lough
Author: Ian Parkinson
Author: Jeffrey A. Hawkes
Author: Douglas P. Connelly

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