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Nonevaporative origin for gypsum in mud sediments from the East China Sea shelf
Liu, Xiting1,2; Li, Anchun3; Dong, Jiang3,4; Zhuang, Guangchao5; Xu, Fangjian6; Wan, Shiming3
Source PublicationMARINE CHEMISTRY
Corresponding AuthorLiu, Xiting( ; Li, Anchun(
AbstractGypsum (CaSO4 center dot 2H(2)O) precipitated in nonevaporative marine environments is rarely reported, and the related diagenetic process and its implications for the sulfur cycle (e.g., sulfide reoxidation) are still not well known. We employ coupled sulfur and oxygen isotopes of authigenic gypsum, as well as sulfur isotopic compositions of pyrite, from core EC2005, which is drilled on the inner shelf of the East China Sea, to constrain the sulfur and oxygen sources for gypsum precipitation. The delta S-34(gypsum) values range from -24.8 to -12.2 parts per thousand, which are much more depleted in S-34 than modem seawater sulfate, suggesting additional S-34-depleted sulfur sources, i.e., coexisting pyrites produced by microbial sulfate reduction. According to a mixing model for paired sulfur isotopes of gypsum and pyrite, > 70% of gypsum sulfur is derived from pyrite reoxidation. The delta O-18(gypsum) values, ranging from 1.1 to 4.6 parts per thousand, suggest that the oxygen isotopes of porewater sulfate should fall between -2.4 and 1.1 parts per thousand, which are more depleted than seawater sulfate in O-18. Two mechanisms are proposed to explain the reoxidation of pyrite at different depths: in the lower section (10-4 m; Unit II), pyrite is oxidized by metal oxides under anaerobic conditions, producing O-18-depleted oxygen from seawater; while in the upper section (4-0 m; Unit I), pyrite reoxidation may occur under aerobic conditions, involving atmospheric oxygen. Either the aerobic or anaerobic mechanisms could cause drops in the porewater pH, leading to carbonate dissolution. These processes could therefore elevate the concentrations of sulfate and calcium ions in porewater, in which authigenic gypsum crystals are precipitated. In addition, both sulfur and oxygen isotopic signals of gypsum indicate a possible influence of methane on sulfate reduction in the mud sediments of core EC2005, which may be related to biogenic gas (dominated by CH4) in this region. Our new findings thus indicate that sulfide reoxidation in marine sediments plays an important role in the biogeochemical sulfur cycle on the continental margin.
KeywordGypsum Pyrite Sulfur isotope Mud sediment East China Sea
Indexed BySCI
Funding ProjectNational Natural Science Foundation of China[41430965] ; National Natural Science Foundation of China[41606062] ; Senior User Project of RV KEXUE[KEXUE2017G1] ; State Key Laboratory of Marine Geology, Tongji University[MGK1824]
WOS Research AreaChemistry ; Oceanography
WOS SubjectChemistry, Multidisciplinary ; Oceanography
WOS IDWOS:000447819800009
Citation statistics
Cited Times:1[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorLiu, Xiting; Li, Anchun
Affiliation1.Ocean Univ China, Coll Marine Geosci, Key Lab Submarine Geosci & Prospecting Technol, Qingdao 266100, Peoples R China
2.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Geol, Qingdao 266061, Peoples R China
3.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Peoples R China
4.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
5.Univ Georgia, Dept Marine Sci, Athens, GA 30602 USA
6.China Univ Petr, Sch Geosci, Qingdao 266580, Peoples R China
Corresponding Author AffilicationInstitute of Oceanology, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
Liu, Xiting,Li, Anchun,Dong, Jiang,et al. Nonevaporative origin for gypsum in mud sediments from the East China Sea shelf[J]. MARINE CHEMISTRY,2018,205:90-97.
APA Liu, Xiting,Li, Anchun,Dong, Jiang,Zhuang, Guangchao,Xu, Fangjian,&Wan, Shiming.(2018).Nonevaporative origin for gypsum in mud sediments from the East China Sea shelf.MARINE CHEMISTRY,205,90-97.
MLA Liu, Xiting,et al."Nonevaporative origin for gypsum in mud sediments from the East China Sea shelf".MARINE CHEMISTRY 205(2018):90-97.
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