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Authigenic carbonates from newly discovered active cold seeps on the northwestern slope of the South China Sea: Constraints on fluid sources, formation environments, and seepage dynamics
Liang, QY; Hu, Y; Feng, D; Peckmann, J; Chen, LY; Yang, SX; Liang, JQ; Tao, J; Chen, DF; feng@scsio.ac.cn
2017
Source PublicationDEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
Volume124Pages:31-41
AbstractAuthigenic carbonates recovered from two newly discovered active cold seeps on the northwestern slope of the South China Sea have been studied using petrography, mineralogy, stable carbon and oxygen isotopic, as well as trace element compositions, together with AMS C-14 ages of shells of seep-dwelling bivalves to unravel fluid sources, formation conditions, and seepage dynamics. The two seeps (ROV1 and ROV2), referred to as 'Haim seeps' herein, are approximately 7 kilometers apart, and are typified by abundant carbonate rocks represented bycrusts and nodules. Aragonite and high-Mg calcite are the main carbonate minerals. Based on low delta C-13(carbonate) values ranging from -43.0 parts per thousand to -27.5 parts per thousand (V-PDB) methane is apparently the predominant carbon source of seep carbonates. The corresponding 8180 values, varying from 2.5 parts per thousand to 5.8 parts per thousand (V-PDB), mostly are higher than calculated values representing precipitation in equilibrium with seawater (2.5%o to 3.8 parts per thousand), which probably reflects past destabilization of locally abundant gas hydrates. In addition, we found that carbonates with bivalve shells are generally aragonite-dominated, and bear no barium enrichment but uranium enrichments, reflecting shallow formation depths close to the seafloor. In contrast, carbonate crusts without bivalve shells and nodules contain more calcite, and are characterized by major molybdenum enrichment and different degrees of barium enrichment, agreeing with precipitation at greater depth under strictly anoxic conditions. AMS 14C ages suggest that a major episode of carbonate precipitation occurred between 6.1 ka and 5.1 ka BP at the Haima seeps, followed by a possibly subordinate episode from approximately 3.9 ka to 2.9 ka BP. The common occurrence of dead bivalves at both sites indicates that chemosynthesis-based communities flourished to a greater extent in the past, probably reflecting a decline of seepage activity in recent times. Overall, these results confirm that authigenic carbonates from gas hydrate-bearing areas can provide insight into long-term seepage dynamics and the genesis and fate of marine gas hydrate reservoirs.
Department[Liang, Qianyong; Yang, Shengxiong; Liang, Jinqiang; Tao, Jun] China Geol Survey, Guangzhou Marine Geol Survey, MLR Key Lab Marine Mineral Resources, Guangzhou 510070, Guangdong, Peoples R China; [Hu, Yu; Chen, Linying; Chen, Duofu] Shanghai Ocean Univ, Coll Marine Sci, Shanghai Engn Res Ctr Hadal Sci & Technol, Shanghai 201306, Peoples R China; [Feng, Dong] Chinese Acad Sci, South China Sea Inst Oceanol, CAS Key Lab Ocean & Marginal Sea Geol, Guangzhou 510301, Guangdong, Peoples R China; [Peckmann, Joern] Univ Hamburg, Inst Geol, D-20146 Hamburg, Germany; [Peckmann, Joern] Univ Vienna, Dept Geodynam & Sedimentol, A-1090 Vienna, Austria
KeywordCold Seep Authigenic Carbonate Fluid Source Formation Environment Seepage Dynamic C-14 Age South China Sea
Funding ProjectMSG
Document Type期刊论文
Identifierhttp://ir.scsio.ac.cn/handle/344004/16510
Collection中科院边缘海地质重点实验室
Corresponding Authorfeng@scsio.ac.cn
Recommended Citation
GB/T 7714
Liang, QY,Hu, Y,Feng, D,et al. Authigenic carbonates from newly discovered active cold seeps on the northwestern slope of the South China Sea: Constraints on fluid sources, formation environments, and seepage dynamics[J]. DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS,2017,124:31-41.
APA Liang, QY.,Hu, Y.,Feng, D.,Peckmann, J.,Chen, LY.,...&feng@scsio.ac.cn.(2017).Authigenic carbonates from newly discovered active cold seeps on the northwestern slope of the South China Sea: Constraints on fluid sources, formation environments, and seepage dynamics.DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS,124,31-41.
MLA Liang, QY,et al."Authigenic carbonates from newly discovered active cold seeps on the northwestern slope of the South China Sea: Constraints on fluid sources, formation environments, and seepage dynamics".DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS 124(2017):31-41.
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