Mercury (Hg) geochemistry of mid-ocean ridge sediments on the Central Indian Ridge: Chemical forms and isotopic composition SCIE SCOPUS

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Title
Mercury (Hg) geochemistry of mid-ocean ridge sediments on the Central Indian Ridge: Chemical forms and isotopic composition
Author(s)
Kim, Ji Hun; Lim, Dhong Il; Jeong, Do Hyun; Xu, Zhaokai; Kim, Haryun; Kim, Jonguk; Kim, Dong Sung
KIOST Author(s)
Kim, Ji Hun(김지훈)Lim, Dhong Il(임동일)Jeong, Do Hyun(정도현)KIM, Ha Ryun(김하련)Kim, Jonguk(김종욱)Kim, Dong Sung(김동성)
Alternative Author(s)
김지훈; 임동일; 정도현; 김하련; 김종욱; 김동성
Publication Year
2022-08
Abstract
To geochemically characterize mercury (Hg) in the deep-sea ridge environment, the total concentration, chemical forms (sequential leaching extraction), and isotopic compositions of Hg in surface sediments from the middle portion of the Central Indian Ridge were investigated. Highly elevated Hg concentrations (up to 13,000 ng/g) in sediments near the hydrothermal vent are associated with intense hydrothermal activity driven by serpentinization. The hydrothermal impact on these sediments is also evident in the REECN fractionation pattern with a remarkably strong positive europium (Eu) anomaly. Most volcanic and hydrothermal Hg in the study area is preferentially precipitated with sulfides; in the hydrothermal vent area, however, scavenging by Fe-Mn hydroxides is another significant removal pathway of Hg. Thus, such precipitation and production of sulfides and hydroxides are a major cause of local enrichment of Hg around the mid-ocean ridge. Most sediments show limited or no mass-independent fractionation (Δ199Hg = +0.02 ± 0.21‰, 2σ, n = 15), indicating that syngenetic magmatic or mantle-derived materials are the dominant Hg source. However, the large variation in mass-dependent fractionation was observed, especially in the vent-distal sediments (δ202Hg = −1.10 ± 0.80‰, 2σ, n = 11), which occurred mainly during the formation of the sulfides and may be associated with preferential precipitation of lighter isotopes. Our study demonstrates that an off-axis high-temperature hydrothermal system driven by exothermic serpentinization of ultramafic mantle rocks may serve as a significant Hg source and provides further insights into grasping the behavior of hydrothermal and volcanogenic Hg in active deep-sea ridge systems.
ISSN
0009-2541
URI
https://sciwatch.kiost.ac.kr/handle/2020.kiost/42516
DOI
10.1016/j.chemgeo.2022.120942
Bibliographic Citation
Chemical Geology, v.604, 2022
Publisher
Elsevier BV
Keywords
Chemical fractionation; Isotope; Mercury; Hydrothermal vents; Mid-ocean ridge sediments
Type
Article
Language
English
Document Type
Article
Publisher
Elsevier BV
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