methaneseepageintensitiestracedbysulfurisotopesofpyriteandgypsuminsedimentfromtheshenhuareasouthchinasea

	methaneseepageintensitiestracedbysulfurisotopesofpyriteandgypsuminsedimentfromtheshenhuareasouthchinasea
	Zhang Mei 1; Lu Hongfeng 2; Guan Hongxiang1 ; Liu Lihua 1; Wu Daidai1 ; Wu Nengyou3
刊名	actaoceanologicasinica
	2018
卷号	37 期号:7 页码:20
ISSN号	0253-505X
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] ; [National Natural Science Foundation of China] ; [China National Petroleum Corporation] ; [Chinese Academic of Sciences]
语种	英语
内容类型	期刊论文
源URL	[http://ir.giec.ac.cn/handle/344007/19437]
专题	中国科学院广州能源研究所
作者单位	1.中国科学院广州能源研究所 2.中国科学院广州地球化学研究所 3.黑龙江省环境保护科学研究院
推荐引用方式 GB/T 7714	Zhang Mei,Lu Hongfeng,Guan Hongxiang,et al. methaneseepageintensitiestracedbysulfurisotopesofpyriteandgypsuminsedimentfromtheshenhuareasouthchinasea[J]. actaoceanologicasinica,2018,37(7):20.
APA	Zhang Mei,Lu Hongfeng,Guan Hongxiang,Liu Lihua,Wu Daidai,&Wu Nengyou.(2018).methaneseepageintensitiestracedbysulfurisotopesofpyriteandgypsuminsedimentfromtheshenhuareasouthchinasea.actaoceanologicasinica,37(7),20.
MLA	Zhang Mei,et al."methaneseepageintensitiestracedbysulfurisotopesofpyriteandgypsuminsedimentfromtheshenhuareasouthchinasea".actaoceanologicasinica 37.7(2018):20.