ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Marine Biogeochemistry
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1653453
The process of trace metals enrichment in pyrite under methane seepage in the northern South China Sea
Provisionally accepted
Yanting Ling1,2
Xuan Chen1,2
Daidai WU1,2*
Qinyi Zhang2,3Shengyi Mao1,2
Guangrong Jin2Jie Liu2
Haizhen Zhai2
Chao Yang1,2
Zheng Su1,2
Nengyou Wu4- 1University of Science and Technology of China, Hefei, China
- 2Chinese Academy of Sciences Guangzhou Institute of Energy Conversion, Guangzhou, China
- 3Universitat Hamburg, Hamburg, Germany
- 4Qingdao Institute of Marine Geology, Qingdao, China
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Pyrite plays an important role in indicating methane seep. The effects of organic sulfate reduction (OSR) and sulfate-driven anaerobic oxidation of methane (SD-AOM) on the trace metals in pyrite have aroused interest; however, further researches about how these two pathways control the trace elements patterns are still required. Therefore, we applied laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to analyzed the trace elements patterns of pyrites in core Z22-3 sampled from the northern South China Sea. Sr/Ca-Mg/Ca, (Mo/U) EF values, chromium reducible sulfur (CRS) content, TOC, δ34S and δ13C values of bulk sediments are used to determine the position of sulfate-methane transition zone (SMTZ). Progressively more positive δ34S values (up to -36.54‰) of the CRS and the increase of Mg/Ca indicate the enhancement of SD-AOM, suggesting that the position of SMTZ is located at the depths from 181 to 481 cmbsf and 1101 to 1401 cmbsf. Within SMTZ, pyrites exhibit obvious enrichments in Co, Ni, Mo and Pb; depletion in Mn, Zn, Cu and V. We summarize the process of methane seepage affecting trace elements in pyrite: Co, Mo, and Ni are transported by the water column to the sediment-water interface (SWI) and adsorbed by iron and manganese oxyhydroxide aggregates. When it comes to suboxic sediments, oxyhydroxides released these trace elements because of the reduction; methane seepage promotes the combination and further immobilization of these trace elements with authigenic pyrite; simultaneously the high SD-AOM rates lead to the enhanced precipitation of Mn, Cu, Zn and et al. as independent metal sulfides, resulting in the depletion of these trace elements in pyrites.
Keywords: methane seep, South China Sea, pyrite, Trace metals, Biogeochemical cycle
Received: 25 Jun 2025; Accepted: 15 Sep 2025.
Copyright: © 2025 Ling, Chen, WU, Zhang, Mao, Jin, Liu, Zhai, Yang, Su and Wu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Daidai WU, wudd@ms.giec.ac.cn
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