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Sources of REE in sediment cores from the Rainbow vent site (36,14'N, MAR)

Sources of REE in sediment cores from the Rainbow vent site (36,14'N, MAR)
Sources of REE in sediment cores from the Rainbow vent site (36,14'N, MAR)
A geochemical investigation was carried out on two sediment cores collected at 2 and 5 km from the Rainbow hydrothermal vent site. Bulk sediment compositions indicate that these cores record clear enrichments in Fe, Cu, Mn, V, P and As from hydrothermal plume fallout (Cave et al., 2002) [Cave, R.R., German, C.R., Thomson, J., Nesbitt, R.W., 2002. Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge. Geochim. Cosmochim. Acta 66 (11), 1905–1923]. Sequential dissolution of the bulk sediments has been used to discriminate between a leach (biogenic and oxy-hydroxide) component and a residual phase (detrital and sulphide/sulphate fractions). Major element data (Al, Fe, Ti, Mn, Mg, Ca, Si and index%) reveal that the hydrothermal input, as recorded in the leach phase, is much stronger than apparent from bulk sediment analyses alone. REE patterns for the leach phase record contributions from both biogenic carbonate (mimicking seawater REE patterns) and hydrothermal oxy-hydroxides, with the latter exhibiting positive Eu anomalies (hydrothermal derived) and negative Ce anomalies (seawater derived). Based on major element and REE data, the residue contains contributions from aeolian dust input, local MORB material and a hydrothermal component. Ternary REE mixing calculations indicate that most of the REE within the residual fraction (80%) is derived from hydrothermal material, while detrital contributions to the REE budget, as deep-sea clay and volcanic debris, are <20%. By combining bulk and REE data for the various end-member components of the residue, we calculate that the chemical composition of the residue hydrothermal end-member is high in Ca (6–15%) and with a Nd/Sr ratio of 0.004. These characteristics indicate the presence of low-solubility hydrothermal sulphate (rather than sulphide) material within the residue component of Rainbow hydrothermal sediments.
Hydrothermal, Geochemistry, Sulphate, Sediment, Sequential dissolution, Rainbow vent field, REE
0009-2541
329-352
Chavagnac, V.
0824a679-684f-47ba-8ccd-f8d36cc18d90
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069
Milton, J.A.
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Palmer, M.R.
d2e60e81-5d6e-4ddb-a243-602537286080
Chavagnac, V.
0824a679-684f-47ba-8ccd-f8d36cc18d90
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069
Milton, J.A.
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Palmer, M.R.
d2e60e81-5d6e-4ddb-a243-602537286080

Chavagnac, V., German, C.R., Milton, J.A. and Palmer, M.R. (2005) Sources of REE in sediment cores from the Rainbow vent site (36,14'N, MAR). Chemical Geology, 216 (3-4), 329-352. (doi:10.1016/j.chemgeo.2004.11.015).

Record type: Article

Abstract

A geochemical investigation was carried out on two sediment cores collected at 2 and 5 km from the Rainbow hydrothermal vent site. Bulk sediment compositions indicate that these cores record clear enrichments in Fe, Cu, Mn, V, P and As from hydrothermal plume fallout (Cave et al., 2002) [Cave, R.R., German, C.R., Thomson, J., Nesbitt, R.W., 2002. Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge. Geochim. Cosmochim. Acta 66 (11), 1905–1923]. Sequential dissolution of the bulk sediments has been used to discriminate between a leach (biogenic and oxy-hydroxide) component and a residual phase (detrital and sulphide/sulphate fractions). Major element data (Al, Fe, Ti, Mn, Mg, Ca, Si and index%) reveal that the hydrothermal input, as recorded in the leach phase, is much stronger than apparent from bulk sediment analyses alone. REE patterns for the leach phase record contributions from both biogenic carbonate (mimicking seawater REE patterns) and hydrothermal oxy-hydroxides, with the latter exhibiting positive Eu anomalies (hydrothermal derived) and negative Ce anomalies (seawater derived). Based on major element and REE data, the residue contains contributions from aeolian dust input, local MORB material and a hydrothermal component. Ternary REE mixing calculations indicate that most of the REE within the residual fraction (80%) is derived from hydrothermal material, while detrital contributions to the REE budget, as deep-sea clay and volcanic debris, are <20%. By combining bulk and REE data for the various end-member components of the residue, we calculate that the chemical composition of the residue hydrothermal end-member is high in Ca (6–15%) and with a Nd/Sr ratio of 0.004. These characteristics indicate the presence of low-solubility hydrothermal sulphate (rather than sulphide) material within the residue component of Rainbow hydrothermal sediments.

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More information

Published date: 2005
Keywords: Hydrothermal, Geochemistry, Sulphate, Sediment, Sequential dissolution, Rainbow vent field, REE

Identifiers

Local EPrints ID: 15389
URI: http://eprints.soton.ac.uk/id/eprint/15389
ISSN: 0009-2541
PURE UUID: 21d16dc9-bc0d-49fa-aac5-5a497f44a487
ORCID for J.A. Milton: ORCID iD orcid.org/0000-0003-4245-5532

Catalogue record

Date deposited: 07 Apr 2005
Last modified: 16 Mar 2024 02:51

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Contributors

Author: V. Chavagnac
Author: C.R. German
Author: J.A. Milton ORCID iD
Author: M.R. Palmer

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