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Spatial variation in fluid flow and geochemical fluxes across the sediment–seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz)

Spatial variation in fluid flow and geochemical fluxes across the sediment–seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz)
Spatial variation in fluid flow and geochemical fluxes across the sediment–seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz)
Submarine mud volcanism is an important pathway for transfer of deep-sourced fluids enriched in hydrocarbons and other elements into the ocean. Numerous mud volcanoes (MVs) have been discovered along oceanic plate margins, and integrated elemental fluxes are potentially significant for oceanic chemical budgets. Here, we present the first detailed study of the spatial variation in fluid and chemical fluxes at the Carlos Ribeiro MV in the Gulf of Cadiz. To this end, we combine analyses of the chemical composition of pore fluids with a 1-D transport-reaction model to quantify fluid fluxes, and fluxes of boron, lithium and methane, across the sediment–seawater interface. The pore fluids are significantly depleted in chloride, but enriched in lithium, boron and hydrocarbons, relative to seawater. Pore water profiles of sulphate, hydrogen sulphide and total alkalinity indicate that anaerobic oxidation of methane occurs at 34–180 cm depth below seafloor. Clay mineral dehydration, and in particular the transformation of smectite to illite, produces pore fluids that are depleted in chloride and potassium. Profiles of boron, lithium and potassium are closely related, which suggests that lithium and boron are released from the sediments during this transformation. Pore fluids are expelled into the water column by advection; fluid flow velocities are 4 cm yr?1 at the apex of the MV but they rapidly decrease to 0.4 cm yr?1 at the periphery. The associated fluxes of boron, lithium and methane vary between 7–301, 0.5–6 and 0–806 mmol m?2 yr?1, respectively. We demonstrate that fluxes of Li and B due to mud volcanism may be important on a global scale, however, release of methane into the overlying water column is suppressed by microbial methanotrophy.
0016-7037
1124-1144
Vanneste, Heleen
09098953-c28c-4d59-aa6d-8789f17220d1
Kelly-Gerreyn, Boris A.
0774749f-e27b-44e9-bad9-6c68391c060e
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Haeckel, Matthias
8b05c8db-8426-4270-88e1-80d3bd38df76
Fisher, Rebecca E.
7ebc6bb2-2ad7-4481-9513-3ab490d0c43d
Heeschen, Katja
4ab1f404-78d1-4c16-a982-54d13abc8f18
Mills, Rachel A.
a664f299-1a34-4b63-9988-1e599b756706
Vanneste, Heleen
09098953-c28c-4d59-aa6d-8789f17220d1
Kelly-Gerreyn, Boris A.
0774749f-e27b-44e9-bad9-6c68391c060e
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Haeckel, Matthias
8b05c8db-8426-4270-88e1-80d3bd38df76
Fisher, Rebecca E.
7ebc6bb2-2ad7-4481-9513-3ab490d0c43d
Heeschen, Katja
4ab1f404-78d1-4c16-a982-54d13abc8f18
Mills, Rachel A.
a664f299-1a34-4b63-9988-1e599b756706

Vanneste, Heleen, Kelly-Gerreyn, Boris A., Connelly, Douglas P., James, Rachael H., Haeckel, Matthias, Fisher, Rebecca E., Heeschen, Katja and Mills, Rachel A. (2011) Spatial variation in fluid flow and geochemical fluxes across the sediment–seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz). Geochimica et Cosmochimica Acta, 75 (4), 1124-1144. (doi:10.1016/j.gca.2010.11.017).

Record type: Article

Abstract

Submarine mud volcanism is an important pathway for transfer of deep-sourced fluids enriched in hydrocarbons and other elements into the ocean. Numerous mud volcanoes (MVs) have been discovered along oceanic plate margins, and integrated elemental fluxes are potentially significant for oceanic chemical budgets. Here, we present the first detailed study of the spatial variation in fluid and chemical fluxes at the Carlos Ribeiro MV in the Gulf of Cadiz. To this end, we combine analyses of the chemical composition of pore fluids with a 1-D transport-reaction model to quantify fluid fluxes, and fluxes of boron, lithium and methane, across the sediment–seawater interface. The pore fluids are significantly depleted in chloride, but enriched in lithium, boron and hydrocarbons, relative to seawater. Pore water profiles of sulphate, hydrogen sulphide and total alkalinity indicate that anaerobic oxidation of methane occurs at 34–180 cm depth below seafloor. Clay mineral dehydration, and in particular the transformation of smectite to illite, produces pore fluids that are depleted in chloride and potassium. Profiles of boron, lithium and potassium are closely related, which suggests that lithium and boron are released from the sediments during this transformation. Pore fluids are expelled into the water column by advection; fluid flow velocities are 4 cm yr?1 at the apex of the MV but they rapidly decrease to 0.4 cm yr?1 at the periphery. The associated fluxes of boron, lithium and methane vary between 7–301, 0.5–6 and 0–806 mmol m?2 yr?1, respectively. We demonstrate that fluxes of Li and B due to mud volcanism may be important on a global scale, however, release of methane into the overlying water column is suppressed by microbial methanotrophy.

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More information

Published date: 15 February 2011
Organisations: Marine Geoscience

Identifiers

Local EPrints ID: 174621
URI: http://eprints.soton.ac.uk/id/eprint/174621
ISSN: 0016-7037
PURE UUID: 9835a5c5-7779-4af7-a624-9a93bf4f589d
ORCID for Rachael H. James: ORCID iD orcid.org/0000-0001-7402-2315
ORCID for Rachel A. Mills: ORCID iD orcid.org/0000-0002-9811-246X

Catalogue record

Date deposited: 15 Feb 2011 10:24
Last modified: 09 Nov 2021 03:18

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Contributors

Author: Heleen Vanneste
Author: Boris A. Kelly-Gerreyn
Author: Douglas P. Connelly
Author: Matthias Haeckel
Author: Rebecca E. Fisher
Author: Katja Heeschen
Author: Rachel A. Mills ORCID iD

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