High-precision double-spike Cd isotopic measurements of seawater by MC-ICP-MS and its application to seawater affected by hydrothermal vent fluids

• 作者: OA Chuanwei Zhu Yunzhu Wu Hanjie Wen Guanghai Wu Wenrui Song Yuxu Zhang Bo Zhao .State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences .School of Earth Resources China University of Geosciences .School of Earth Sciences and Resources Chang'An University .College of Earth and Planetary Sciences University of Chinese Academy of Sciences .Key Laboratory of Submarine Geosciences Second Institute of Oceanography MNR .Institute of Land Engineering and Technology Shaanxi Provincial Land Engineering Construction Group Co. Ltd.
• 来源期刊: 地球化学学报(英文）
• 学科: 地球科学
• 年，卷（期）: 2025,（5）
• 页码范围: 132-140
• 页数: 9页
• 语种: 中文

摘要

Cadmium（Cd） isotopes in seawater have been proven as an important geochemical tool for tracing ocean Cd circulation in the modern ocean. In this study, we evaluated a new method to separate Cd（～ 60 ng） from seawater using Chelex resin（1.0 g） coupled with AG-MP-1M resin. The results show that the Chelex resin is sufficient to remove Cd from Na and Mg matrix with Cd recoveries at 98.3 ± 3.5 %（2SD, N = 6）; while AG-MP-1M resin could separate Cd from the residual Na, Mg, and isobaric inferences. The total Cd recoveries of the method are 96.3 ± 1.5 %（2SD; N = 4） and the salinity of the samples has no significant impacts on Cd recovery. Cd isotope ratios were measured using a Nu Plasma Ⅲ MC-ICP-MS and111Cd–110Cd double spike technique. By comparing the δ114/110Cd values（0.00 ± 0.06‰） of synthetic seawaters doped with Cd isotope standard（NIST-3108; treated by Chelex + AG-MP-1M resin） and the reference value（～ 0.00 ‰）, no variations were observed.We also analyzed the Cd isotope compositions of three deep seawaters from a column at the Southwest Indian Ocean Ridges（SWIR）. The δ114/110Cd values of the column are decreased from 1.05 ± 0.05 ‰ at 3200 m to 0.36 ± 0.05 ‰ at 2800 m, differing from reported δ114/110Cd values of deep seawater in other oceans. Considering the spatial distance between the column and active hydrothermal vents in SWIR（～ 13 km）, we propose that such positive δ114/110Cd values of deep seawater were likely contaminated by vent fluids, which could provide heavy Cd isotope to deep seawaters. This study demonstrates that Cd isotope is more sufficient to distinguish the impact of plumes on deep seawater.