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Cold-water corals as archives of seawater Zn and Cu isotopes

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Title: Cold-water corals as archives of seawater Zn and Cu isotopes
Authors: Little, SH
Wilson, DJ
Rehkämper, M
Adkins, JF
Robinson, LF
Van de Flierdt, T
Item Type: Journal Article
Abstract: Traditional carbonate sedimentary archives have proven challenging to exploit for Zn and Cu isotopes, due to the high concentrations of trace metals in potential contaminants (e.g., Fe-Mn coatings) and their low concentrations in carbonate. Here, we present the first dataset of δ66ZnJMC-Lyon and δ65CuSRM 976 values for cold-water corals and address their potential as a seawater archive. Extensive cleaning experiments carried out on two corals with well-developed Fe-Mn rich coatings demonstrate that thorough physical and chemical cleaning can effectively remove detrital and authigenic contaminants. Next, we present metal/Ca ratios and δ66Zn and δ65Cu values for a geographically diverse sample set of Holocene age cold-water corals. Comparing cold-water coral δ66Zn values to estimated ambient seawater δ66Zn values (where Δ66Zncoral-sw = δ66Zncoral – δ66Znseawater), we find Δ66Zncoral-sw = +0.03 ± 0.17‰ (1SD, n = 20). Hence, to a first order, cold-water corals record seawater Zn isotope compositions without fractionation. The average Holocene coral Cu isotope composition is +0.59 ± 0.23‰ (1SD, n = 15), similar to the mean of published deep seawater δ65Cu values at +0.66 ± 0.09‰, but with considerable variability. Finally, δ66Zn and δ65Cu data are presented for a small subset of four glacial-age corals. These values overlap with the respective Holocene coral datasets, hinting at limited glacial-interglacial changes in oceanic Zn and Cu cycling.
Issue Date: Sep-2021
Date of Acceptance: 2-May-2021
URI: http://hdl.handle.net/10044/1/89294
DOI: 10.1016/j.chemgeo.2021.120304
ISSN: 0009-2541
Publisher: Elsevier BV
Start Page: 1
End Page: 20
Journal / Book Title: Chemical Geology
Volume: 578
Copyright Statement: © 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: 0402 Geochemistry
0403 Geology
0406 Physical Geography and Environmental Geoscience
Geochemistry & Geophysics
Publication Status: Published
Article Number: 120304
Online Publication Date: 2021-05-05
Appears in Collections:Earth Science and Engineering
Faculty of Engineering

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