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Evidence for hydrothermal venting in Fe isotope compositions of the deep Pacific Ocean through time

Evidence for hydrothermal venting in Fe isotope compositions of the deep Pacific Ocean through time
Evidence for hydrothermal venting in Fe isotope compositions of the deep Pacific Ocean through time
Temporal variations in Fe isotope compositions at three locations in the Pacific Ocean over the last 10 Ma are inferred from high-resolution analyses of three hydrogenetic ferromanganese crusts. Iron pathways to the central deep Pacific Ocean appear to have remained constant over the past 10 Ma, reflected by a remarkably constant Fe isotope composition, despite large changes in the Fe delivery rates to the surface ocean via dust. These results suggest that the Fe cycle in the deep ocean is decoupled from that in surface waters. By contrast, one ferromanganese crust from the Izu-Bonin (IB) back-arc/marginal basin of the W. Pacific exhibits large ?56Fe variations. In that crust, decreases in ?56Fe values correlate with increases in Mn, Mg, Ni, Cu, Zn, Mo, and V contents, and consistent with periods of intense hydrothermal input and increased growth rates. A second crust located within 100 km of the first IB sample does not record any of these periods of enhanced hydrothermal input. This probably reflects the isolated pathways by which hydrothermally sourced Fe may have migrated in the back arc, highlighting the high degree of provinciality that Fe isotopes may have in the modern (oxic) oceans. Our results demonstrate that despite efficient removal at the source, hydrothermal Fe injected into the deep ocean could account for a significant fraction of the dissolved Fe pool in the deep ocean, and that hydrothermally sourced Fe fluxes to the open ocean may have lower ?56Fe values than those measured so far in situ at hydrothermal vents. Correlation between ?56Fe values and elements enriched in hydrothermal fluids may provide a means for distinguishing hydrothermal Fe from other low-?56Fe sources to the oceans such as dissolved riverine Fe or porewaters in continental shelf sediments.
Fe isotopes, ferromanganese crusts, hydrothermal, Izu-Bonin, Pacific Ocean
0012-821X
202-217
Chu, N-C.
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Johnson, C.M.
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Beard, B.L.
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German, C.R.
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Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Frank, M.
ed321a25-101f-4e29-80b8-093ff3bfa76c
Bohn, U.
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Kubik, P.W.
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Usui, A.
7fd568c6-a438-48c6-a67c-f8a2907fa4ad
Graham, I.
c2dd7e21-80c3-46ae-9e14-4892a475f8d2
Chu, N-C.
172006e7-7bfd-4927-8cdc-0b7910231332
Johnson, C.M.
10fcaff9-857e-4610-9751-a2a1daf95432
Beard, B.L.
1ea59b19-78e9-492b-a3ea-f1e4440c0f47
German, C.R.
cd0eedd5-1377-4182-9c8a-b06aef8c1069
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Frank, M.
ed321a25-101f-4e29-80b8-093ff3bfa76c
Bohn, U.
a1eb9e0a-bdb8-4850-a6b5-c0dd9bc50c88
Kubik, P.W.
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Usui, A.
7fd568c6-a438-48c6-a67c-f8a2907fa4ad
Graham, I.
c2dd7e21-80c3-46ae-9e14-4892a475f8d2

Chu, N-C., Johnson, C.M., Beard, B.L., German, C.R., Nesbitt, R.W., Frank, M., Bohn, U., Kubik, P.W., Usui, A. and Graham, I. (2006) Evidence for hydrothermal venting in Fe isotope compositions of the deep Pacific Ocean through time. Earth and Planetary Science Letters, 245 (1-2), 202-217. (doi:10.1016/j.epsl.2006.02.043).

Record type: Article

Abstract

Temporal variations in Fe isotope compositions at three locations in the Pacific Ocean over the last 10 Ma are inferred from high-resolution analyses of three hydrogenetic ferromanganese crusts. Iron pathways to the central deep Pacific Ocean appear to have remained constant over the past 10 Ma, reflected by a remarkably constant Fe isotope composition, despite large changes in the Fe delivery rates to the surface ocean via dust. These results suggest that the Fe cycle in the deep ocean is decoupled from that in surface waters. By contrast, one ferromanganese crust from the Izu-Bonin (IB) back-arc/marginal basin of the W. Pacific exhibits large ?56Fe variations. In that crust, decreases in ?56Fe values correlate with increases in Mn, Mg, Ni, Cu, Zn, Mo, and V contents, and consistent with periods of intense hydrothermal input and increased growth rates. A second crust located within 100 km of the first IB sample does not record any of these periods of enhanced hydrothermal input. This probably reflects the isolated pathways by which hydrothermally sourced Fe may have migrated in the back arc, highlighting the high degree of provinciality that Fe isotopes may have in the modern (oxic) oceans. Our results demonstrate that despite efficient removal at the source, hydrothermal Fe injected into the deep ocean could account for a significant fraction of the dissolved Fe pool in the deep ocean, and that hydrothermally sourced Fe fluxes to the open ocean may have lower ?56Fe values than those measured so far in situ at hydrothermal vents. Correlation between ?56Fe values and elements enriched in hydrothermal fluids may provide a means for distinguishing hydrothermal Fe from other low-?56Fe sources to the oceans such as dissolved riverine Fe or porewaters in continental shelf sediments.

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Published date: 2006
Keywords: Fe isotopes, ferromanganese crusts, hydrothermal, Izu-Bonin, Pacific Ocean

Identifiers

Local EPrints ID: 44693
URI: https://eprints.soton.ac.uk/id/eprint/44693
ISSN: 0012-821X
PURE UUID: d4667f36-6e8c-472d-a70a-b158238b376d

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Date deposited: 08 Mar 2007
Last modified: 13 Mar 2019 21:06

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Contributors

Author: N-C. Chu
Author: C.M. Johnson
Author: B.L. Beard
Author: C.R. German
Author: R.W. Nesbitt
Author: M. Frank
Author: U. Bohn
Author: P.W. Kubik
Author: A. Usui
Author: I. Graham

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