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Pockmark activity inferred from pore water geochemistry in shallow sediments of the pockmark field in southwestern Xisha Uplift, northwestern South China Sea
[Luo, Min; Chen, Duofu] Chinese Acad Sci, Guangzhou Inst Geochem, Key Lab Marginal Sea Geol, Guangzhou 510640, Guangdong, Peoples R China; [Chen, Linying; Wang, Shuhong; Yan, Wen; Chen, Duofu] Chinese Acad Sci, South China Sea Inst Oceanol, Key Lab Marginal Sea Geol, Guangzhou 510301, Guangdong, Peoples R China; [Wang, Hongbin] Guangzhou Marine Geol Survey, Guangzhou 510740, Guangdong, Peoples R China; [Luo, Min] Univ Chinese Acad Sci, Beijing 100049, Peoples R China; cdf@gig.ac.cn
2013
Source PublicationMARINE AND PETROLEUM GEOLOGY
ISSN0264-8172
Volume48Pages:247-259
AbstractPockmarks are widespread on the seabed offshore southwestern Xisha Uplift, northwestern South China Sea. Some of them are so enormous that they are rare worldwide, but their activities were previously poorly known. We collected three gravity-piston cores from this pockmark field, one (C9) from outside, but in close proximity to, a giant pockmark and the other two (C14 and C19) from inside two giant pockmarks. The geochemistry of the pore waters, including SO42-, K+, Ca-2+, Mg2+, Sr2+, dissolved inorganic carbon (DIC), delta C-13(DIC) values, and delta S-34 values of sulfate, was analyzed to elucidate the biogeochemical processes associated with sulfate consumption and to evaluate the current pockmark activity. The sulfate concentration depth profiles of C9 and C19 are predominantly in response to organoclastic sulfate reduction (OSR), whereas the sulfate concentrations of C14 exhibit three zones of different concentration gradients resulting from varying proportions of contributions from OSR and anaerobic oxidation of methane (AOM). The estimated lower sulfur isotope fractionation factor suggests a higher microbial sulfate reduction rate in C14 than in C9 as a possible consequence of AOM. Based on the sulfate concentration gradient of C14 below 3.7 mbsf, the depth of the sulfate methane interface (SMI) and the methane diffusive flux in C14 are calculated to be similar to 14.3 mbsf and similar to 0.0144 mol m(-2) yr(-1), respectively. The pore-water Mg/Ca and Sr/Ca weight ratios suggest that high Mg-calcite is in equilibrium with respect to pore water or has recently precipitated from pore water in C14. The delta C-13(DIC) values of C9 and C19 are derived from a binary mixture of delta C-13 from organic matter and of delta C-13(DIC) from bottom water, while DIC from bottom water, OSR, and AOM, concomitant with C-13-enriched DIC from below the SMI possibly all contribute to the DIC pool below 0.66 mbsf in C14. The integrated analysis of pore water geochemistry implies that the pockmark from which C19 was collected may be inactive while the pockmark from which C14 was obtained may currently be sluggish in activity with methane-bearing fluid weakly seeping from subsurface sediments. (c) 2013 Elsevier Ltd. All rights reserved.
Department海洋地质
KeywordSeabed Pockmarks Current Activity Geochemical Process Pore Water Geochemistry Xisha Uplift Northern South China Sea
Subject AreaGeosciences, Multidisciplinary
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Language英语
WOS IDWOS:000328095100020
Citation statistics
Cited Times:19[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.scsio.ac.cn/handle/344004/11102
Collection中科院边缘海地质重点实验室
Corresponding Authorcdf@gig.ac.cn
Recommended Citation
GB/T 7714
[Luo, Min,Chen, Duofu] Chinese Acad Sci, Guangzhou Inst Geochem, Key Lab Marginal Sea Geol, Guangzhou 510640, Guangdong, Peoples R China,[Chen, Linying,et al. Pockmark activity inferred from pore water geochemistry in shallow sediments of the pockmark field in southwestern Xisha Uplift, northwestern South China Sea[J]. MARINE AND PETROLEUM GEOLOGY,2013,48:247-259.
APA [Luo, Min.,Chen, Duofu] Chinese Acad Sci, Guangzhou Inst Geochem, Key Lab Marginal Sea Geol, Guangzhou 510640, Guangdong, Peoples R China.,[Chen, Linying.,Wang, Shuhong.,Yan, Wen.,...&cdf@gig.ac.cn.(2013).Pockmark activity inferred from pore water geochemistry in shallow sediments of the pockmark field in southwestern Xisha Uplift, northwestern South China Sea.MARINE AND PETROLEUM GEOLOGY,48,247-259.
MLA [Luo, Min,et al."Pockmark activity inferred from pore water geochemistry in shallow sediments of the pockmark field in southwestern Xisha Uplift, northwestern South China Sea".MARINE AND PETROLEUM GEOLOGY 48(2013):247-259.
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