Cold-water corals as archives of seawater Zn and Cu isotopes
Cold-water corals as archives of seawater Zn and Cu isotopes
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DOI：
10.1016/j.chemgeo.2021.120304
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发表时间：
2021-05
期刊：
影响因子：
3.9
通讯作者：
S. Little;David J. Wilson;M. Rehkämper;J. Adkins;L. Robinson;T. Flierdt
中科院分区：
文献类型：
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作者：
S. Little;David J. Wilson;M. Rehkämper;J. Adkins;L. Robinson;T. Flierdt
传统的碳酸盐沉积档案已被证明具有挑战性，以利用锌和铜同位素，由于高浓度的微量金属在潜在的污染物（例如，Fe-Mn涂层）和它们在碳酸盐中的低浓度。在这里，我们提出了冷水珊瑚的δ 66 ZnJMC-Lyon和δ 65 CuSRM 976值的第一个数据集，并解决了它们作为海水档案的潜力。对两种具有发达的富铁锰涂层的珊瑚进行了广泛的清洁实验，结果表明，彻底的物理和化学清洁可以有效地去除碎屑和自生污染物。接下来，我们提出了金属/钙比和δ 66锌和δ 65铜值的地理上不同的样本集全新世冷水珊瑚。将冷水珊瑚δ 66 Zn值与环境海水δ 66 Zn值（Δ 66 Zn coral-sw = δ 66 Zn coral- δ 66 Zn海水）进行比较，发现Δ 66 Zn coral-sw = +0.03 ± 0.17‰（1 SD，n= 20）。因此，第一顺序，冷水珊瑚记录海水锌同位素组成没有分馏。全新世珊瑚Cu同位素组成平均值为+0.59 ± 0.23‰（1 SD，n= 15），与已发表的深海δ 65 Cu值平均值（+0.66 ± 0.09‰）相近，但变化较大。最后，δ 66锌和δ 65铜数据的一个小的子集的四个冰川时代的珊瑚。这些值与各自的全新世珊瑚数据集重叠，暗示在有限的冰川间冰期海洋锌和铜循环的变化。
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-Lyonand δ65CuSRM 976values 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.