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Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica)

Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica)
Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica)
In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (Eh) were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition (87Sr/86Sr = 0.708776 at core base) compared with modern seawater (87Sr/86Sr ?0.70918), indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column Eh anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in Eh, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota.
1932-6203
e54686
Aquilina, Alfred
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Connelly, Douglas P.
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Copley, Jon T.
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Green, Darryl R.H.
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Hawkes, Jeffrey A.
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Hepburn, Laura E.
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Huvenne, Veerle A.I.
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Marsh, Leigh
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Mills, Rachel A.
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Tyler, Paul A.
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Aquilina, Alfred
a5ce0174-e2d4-40ee-baa5-86ba2f24058c
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8
Copley, Jon T.
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Green, Darryl R.H.
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Hawkes, Jeffrey A.
ecec24fe-f87f-4dfb-8e82-60d3e30bca8f
Hepburn, Laura E.
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Huvenne, Veerle A.I.
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Marsh, Leigh
d8e1a926-092f-4cab-83f3-3345e2815086
Mills, Rachel A.
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Tyler, Paul A.
d1965388-38cc-4c1d-9217-d59dba4dd7f8

Aquilina, Alfred, Connelly, Douglas P., Copley, Jon T., Green, Darryl R.H., Hawkes, Jeffrey A., Hepburn, Laura E., Huvenne, Veerle A.I., Marsh, Leigh, Mills, Rachel A. and Tyler, Paul A. (2013) Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica) PLoS ONE, 8, (1), e54686. (doi:10.1371/journal.pone.0054686).

Record type: Article

Abstract

In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (Eh) were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition (87Sr/86Sr = 0.708776 at core base) compared with modern seawater (87Sr/86Sr ?0.70918), indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column Eh anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in Eh, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota.

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Published date: 25 January 2013
Organisations: Geochemistry, Marine Geoscience

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Local EPrints ID: 347646
URI: http://eprints.soton.ac.uk/id/eprint/347646
ISSN: 1932-6203
PURE UUID: 105f9ab9-3110-4ba4-8c24-b1f37d0080ae
ORCID for Rachel A. Mills: ORCID iD orcid.org/0000-0002-9811-246X

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Date deposited: 28 Jan 2013 14:44
Last modified: 03 Oct 2017 16:40

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Contributors

Author: Alfred Aquilina
Author: Douglas P. Connelly
Author: Jon T. Copley
Author: Darryl R.H. Green
Author: Jeffrey A. Hawkes
Author: Laura E. Hepburn
Author: Veerle A.I. Huvenne
Author: Leigh Marsh
Author: Rachel A. Mills ORCID iD
Author: Paul A. Tyler

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