Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area, South China Sea

doi:10.1007/s13131-018-1241-1

	Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area, South China Sea
	Zhang Mei 2; Lu Hongfeng 1; Guan Hongxiang 2,3; Liu Lihua 2; Wu Daidai 2; Wu Nengyou 3,4
刊名	ACTA OCEANOLOGICA SINICA
	2018-07-01
卷号	37 期号:7 页码:20-27
关键词	pyrite tube authigenic gypsum sulfur isotopes methane seepage northern South China Sea
ISSN号	0253-505X
DOI	10.1007/s13131-018-1241-1
通讯作者	Zhang Mei(zhangmei@ms.giec.ac.cn)
英文摘要	The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments. Anaerobic oxidation of methane (AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment, including pyrite and gypsum. Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor (cmbsf) in the entire core sediment of HS328 from the northern South China Sea. Most pyrites are tubes consisting of framboidal cores and outer crusts. Gypsum aggregates occur as rosettes and spheroids consisting of plates. Some of them grow over pyrite, indicating that gypsum precipitation postdates pyrite formation. The sulfur isotopic values (delta S-34) of pyrite vary greatly (from-46.6aEuro degrees to-12.3aEuro degrees V-CDT) and increase with depth. Thus, the pyrite in the shallow sediments resulted from organoclastic sulfate reduction (OSR) and is influenced by AOM with depth. The relative high abundance and delta S-34 values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone (SMTZ). The sulfur isotopic composition of gypsum (from-25aEuro degrees to-20.7aEuro degrees) is much lower than that of the seawater sulfate, indicating the existence of a S-34-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR. Pyrite oxidation is controlled by ambient electron acceptors such as MnO2, iron (III) and oxygen driven by the SMTZ location shift to great depths. The delta S-34 values of gypsum at greater depth are lower than those of the associated pyrite, revealing downward diffusion of S-34-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate. These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral, which will be favor to the formation of gypsum. Overall, the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities, and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.
资助项目	Qingdao National Laboratory for Marine Science and Technology[QNLM2016ORP0210] ; National Natural Science Foundation of China[41306061] ; National Natural Science Foundation of China[41473080] ; National Natural Science Foundation of China[41376076] ; China National Petroleum Corporation ; Chinese Academic of Sciences[2015A- 4813]
WOS关键词	DRIVEN ANAEROBIC OXIDATION ; HYDRATE-ASSOCIATED SEDIMENTS ; NORTHERN CONTINENTAL-SLOPE ; GAS-HYDRATE ; AUTHIGENIC CARBONATES ; SULFATE REDUCTION ; COLD SEEP ; BLACK-SEA ; ENVIRONMENTAL-CONDITIONS ; HYDROGEN-SULFIDE
WOS研究方向	Oceanography
语种	英语
出版者	SPRINGER
WOS记录号	WOS:000440454600003
资助机构	Qingdao National Laboratory for Marine Science and Technology ; National Natural Science Foundation of China ; China National Petroleum Corporation ; Chinese Academic of Sciences
内容类型	期刊论文
源URL	[http://ir.giec.ac.cn/handle/344007/23670]
专题	中国科学院广州能源研究所
通讯作者	Zhang Mei
作者单位	1.Guangzhou Marine Geol Survey, Guangzhou 510760, Guangdong, Peoples R China 2.Chinese Acad Sci, Guangzhou Inst Energy Convers, Key Lab Gas Hydrate, Guangzhou 510640, Guangdong, Peoples R China 3.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266061, Peoples R China 4.Minist Land & Resources, Qingdao Inst Marine Geol, Key Lab Gas Hydrate, Qingdao 266071, Peoples R China
推荐引用方式 GB/T 7714	Zhang Mei,Lu Hongfeng,Guan Hongxiang,et al. Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area, South China Sea[J]. ACTA OCEANOLOGICA SINICA,2018,37(7):20-27.
APA	Zhang Mei,Lu Hongfeng,Guan Hongxiang,Liu Lihua,Wu Daidai,&Wu Nengyou.(2018).Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area, South China Sea.ACTA OCEANOLOGICA SINICA,37(7),20-27.
MLA	Zhang Mei,et al."Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area, South China Sea".ACTA OCEANOLOGICA SINICA 37.7(2018):20-27.