The University of Southampton
University of Southampton Institutional Repository

Helium isotopes at the Rainbow hydrothermal site (Mid-Atlantic Ridge 36,14'N)

Helium isotopes at the Rainbow hydrothermal site (Mid-Atlantic Ridge 36,14'N)
Helium isotopes at the Rainbow hydrothermal site (Mid-Atlantic Ridge 36,14'N)
The 3He/4He ratio and helium concentration have been measured in the vent fluids and the dispersing plume of the Rainbow hydrothermal site, on the Mid-Atlantic Ridge (MAR). The 3He/4He ratio (7.51 Ra) and 3He end-member concentration (25 pmol/kg) are in the range of observed values elsewhere on mid-ocean ridges, pointing to the relative homogeneity of the upper mantle with respect to helium isotope geochemistry. 3He is linearly correlated with methane and manganese throughout the plume, with CH4/3He and Mn/3He ratios identical to those measured in the hot fluids. The bulk residence time of the plume in the rift valley estimated from the plume 3He budget is V20 days. The 3He flux transported by the plume, calculated from current-meter data, is 12.3: 3 nmol/s, requiring a flux of 490 kg/s of high-temperature fluid. The scaling of the heat flux emitted by the Rainbow site to that of 3He, using the 3He/heat ratio measured in the hydrothermal fluids (9.3 :2U10318 mol/J), indicates a heat output of 1320 MW. With a regional spreading rate of V25 mm/year, we calculate that the annual 3He flux for this section of the MAR is of the order of 0.5:0.2 mmol per kilometre of ridge per millimetre of newly formed crust. This figure compares well with the flux calculated for the neighbouring Lucky Strike segment. Although the uncertainties remain large, both fluxes are V40-50% above the world average (0.33 mmol/km/mm), thus supporting earlier suggestions that the intensity of the hydrothermal activity south of the Azores is higher than expected from the regional spreading rate.
helium, hydrothermal vents, isotopes, heat flux, Mid-Atlantic Ridge
0012-821X
325-335
Jean-Baptiste, P.
c386ba5d-4ce1-448c-868f-d59002035eee
Fourre, E.
85d7a0f5-5d20-4923-bf19-c5a9d5acb593
Charlou, J.
4be2b14b-1987-43a8-9025-3a4ed063f009
Radford-Knoery, J.
9a3f1906-64ba-4b1c-ac18-47a21bd3c1b6
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069
Jean-Baptiste, P.
c386ba5d-4ce1-448c-868f-d59002035eee
Fourre, E.
85d7a0f5-5d20-4923-bf19-c5a9d5acb593
Charlou, J.
4be2b14b-1987-43a8-9025-3a4ed063f009
Radford-Knoery, J.
9a3f1906-64ba-4b1c-ac18-47a21bd3c1b6
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069

Jean-Baptiste, P., Fourre, E., Charlou, J., Radford-Knoery, J. and German, C.R. (2004) Helium isotopes at the Rainbow hydrothermal site (Mid-Atlantic Ridge 36,14'N). Earth and Planetary Science Letters, 221 (1-4), 325-335.

Record type: Article

Abstract

The 3He/4He ratio and helium concentration have been measured in the vent fluids and the dispersing plume of the Rainbow hydrothermal site, on the Mid-Atlantic Ridge (MAR). The 3He/4He ratio (7.51 Ra) and 3He end-member concentration (25 pmol/kg) are in the range of observed values elsewhere on mid-ocean ridges, pointing to the relative homogeneity of the upper mantle with respect to helium isotope geochemistry. 3He is linearly correlated with methane and manganese throughout the plume, with CH4/3He and Mn/3He ratios identical to those measured in the hot fluids. The bulk residence time of the plume in the rift valley estimated from the plume 3He budget is V20 days. The 3He flux transported by the plume, calculated from current-meter data, is 12.3: 3 nmol/s, requiring a flux of 490 kg/s of high-temperature fluid. The scaling of the heat flux emitted by the Rainbow site to that of 3He, using the 3He/heat ratio measured in the hydrothermal fluids (9.3 :2U10318 mol/J), indicates a heat output of 1320 MW. With a regional spreading rate of V25 mm/year, we calculate that the annual 3He flux for this section of the MAR is of the order of 0.5:0.2 mmol per kilometre of ridge per millimetre of newly formed crust. This figure compares well with the flux calculated for the neighbouring Lucky Strike segment. Although the uncertainties remain large, both fluxes are V40-50% above the world average (0.33 mmol/km/mm), thus supporting earlier suggestions that the intensity of the hydrothermal activity south of the Azores is higher than expected from the regional spreading rate.

This record has no associated files available for download.

More information

Published date: 2004
Keywords: helium, hydrothermal vents, isotopes, heat flux, Mid-Atlantic Ridge

Identifiers

Local EPrints ID: 9827
URI: http://eprints.soton.ac.uk/id/eprint/9827
ISSN: 0012-821X
PURE UUID: ee9a91e5-182f-4776-a91b-b1fce3ab6076

Catalogue record

Date deposited: 13 Oct 2004
Last modified: 07 Jan 2022 21:58

Export record

Contributors

Author: P. Jean-Baptiste
Author: E. Fourre
Author: J. Charlou
Author: J. Radford-Knoery
Author: C.R. German

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×