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Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge

Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge
Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge
A geochemical investigation has been conducted of a suite of four sediment cores collected from directly beneath the hydrothermal plume at distances of 2 to 25 km from the Rainbow hydrothermal field. As well as a large biogenic component (>80% CaCO3) these sediments record clear enrichments of the elements Fe, Cu, Mn, V, P, and As from hydrothermal plume fallout but only minor detrital background material. Systematic variations in the abundances of "hydrothermal" elements are observed at increasing distance from the vent site, consistent with chemical evolution of the dispersing plume. Further, pronounced Ni and Cr enrichments at specific levels within each of the two cores collected from closest to the vent site are indicative of discrete episodes of additional input of ultrabasic material at these two near-field locations. Radiocarbon dating reveals mean Holocene accumulation rates for all four cores of 2.7 to 3.7 cm.kyr?1, with surface mixed layers 7 to 10+ cm thick, from which a history of deposition from the Rainbow hydrothermal plume can be deduced. Deposition from the plume supplies elements to the underlying sediments that are either directly hydrothermally sourced (e.g., Fe, Mn, Cu) or scavenged from seawater via the hydrothermal plume (e.g., V, P, As). Holocene fluxes into to the cores’ surface mixed layers are presented which, typically, are an order of magnitude greater than "background" authigenic fluxes from the open North Atlantic. One core, collected closest to the vent site, indicates that both the concentration and flux of hydrothermally derived material increased significantly at some point between 8 and 12 14C kyr ago; the preferred explanation is that this variation reflects the initiation/intensification of hydrothermal venting at the Rainbow hydrothermal field at this time—perhaps linked to some specific tectonic event in this fault-controlled hydrothermal setting.
SEDIMENTS, FLUX, HYDROTHERMAL PLUMES, MID ATLANTIC RIDGE, HOLOCENE
0016-7037
1905-1923
Cave, R.R.
98fdbc47-66c2-4029-a2e0-f42bb394cd2a
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069
Thomson, J.
3395054f-e507-4841-9758-a06ed37f7d6b
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Cave, R.R.
98fdbc47-66c2-4029-a2e0-f42bb394cd2a
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069
Thomson, J.
3395054f-e507-4841-9758-a06ed37f7d6b
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4

Cave, R.R., German, C.R., Thomson, J. and Nesbitt, R.W. (2002) Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge. Geochimica et Cosmochimica Acta, 66 (11), 1905-1923. (doi:10.1016/S0016-7037(02)00823-2).

Record type: Article

Abstract

A geochemical investigation has been conducted of a suite of four sediment cores collected from directly beneath the hydrothermal plume at distances of 2 to 25 km from the Rainbow hydrothermal field. As well as a large biogenic component (>80% CaCO3) these sediments record clear enrichments of the elements Fe, Cu, Mn, V, P, and As from hydrothermal plume fallout but only minor detrital background material. Systematic variations in the abundances of "hydrothermal" elements are observed at increasing distance from the vent site, consistent with chemical evolution of the dispersing plume. Further, pronounced Ni and Cr enrichments at specific levels within each of the two cores collected from closest to the vent site are indicative of discrete episodes of additional input of ultrabasic material at these two near-field locations. Radiocarbon dating reveals mean Holocene accumulation rates for all four cores of 2.7 to 3.7 cm.kyr?1, with surface mixed layers 7 to 10+ cm thick, from which a history of deposition from the Rainbow hydrothermal plume can be deduced. Deposition from the plume supplies elements to the underlying sediments that are either directly hydrothermally sourced (e.g., Fe, Mn, Cu) or scavenged from seawater via the hydrothermal plume (e.g., V, P, As). Holocene fluxes into to the cores’ surface mixed layers are presented which, typically, are an order of magnitude greater than "background" authigenic fluxes from the open North Atlantic. One core, collected closest to the vent site, indicates that both the concentration and flux of hydrothermally derived material increased significantly at some point between 8 and 12 14C kyr ago; the preferred explanation is that this variation reflects the initiation/intensification of hydrothermal venting at the Rainbow hydrothermal field at this time—perhaps linked to some specific tectonic event in this fault-controlled hydrothermal setting.

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Published date: 2002
Keywords: SEDIMENTS, FLUX, HYDROTHERMAL PLUMES, MID ATLANTIC RIDGE, HOLOCENE

Identifiers

Local EPrints ID: 5991
URI: http://eprints.soton.ac.uk/id/eprint/5991
ISSN: 0016-7037
PURE UUID: cd9c8360-8dac-4076-a04c-c5067f1790f0

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Date deposited: 07 Jun 2004
Last modified: 15 Jul 2019 19:38

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Contributors

Author: R.R. Cave
Author: C.R. German
Author: J. Thomson
Author: R.W. Nesbitt

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