气候变化领域集成服务门户(CCPortal): Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark

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DOI	10.1029/2019JB018283
	Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark—Quantities and Dynamics
	Pape T.; Ruffine L.; Hong W.-L.; Sultan N.; Riboulot V.; Peters C.A.; Kölling M.; Zabel M.; Garziglia S.; Bohrmann G.
发表日期	2020
ISSN	21699313
卷号	125 期号:9
英文摘要	The evolution of submarine pockmarks is often related to the ascent of fluid from the subsurface. For pockmarks located within the gas hydrate stability zone, methane oversaturation can result in the formation of gas hydrates in the sediment. An ~600 m-wide sea floor depression in deep waters offshore Nigeria, Pockmark A, was investigated for distributions and quantities of shallow gas hydrates, origins of hydrocarbons, and time elapsed since the last major fluid ascent event. For the first time, pressure coring of shallow sediments and drilling of more than 50 m-long cores with the sea floor drill rig MARUM-MeBo70 were conducted in this pockmark. Unusually, high hydrate saturations of up to 51% of pore volume in the uppermost 2.5 m of sediment in the pockmark center substantiate that deepwater pockmarks are a relevant methane reservoir. Molecular and stable C and H isotopic compositions suggest that thermogenic hydrocarbons and secondary microbial methane resulting from petroleum biodegradation are injected into shallower sediments and mixed with primary microbial hydrocarbons. Two independent pore water chloride and sulfate modeling approaches suggest that a major methane migration event occurred during the past one to three centuries. A rough sea floor topography within the pockmark most likely results from combined sediment removal through ascending gas bubbles, hydrate clogging and deflection of migration pathways, gas pressure build-up, and hydrate sea floor detachment. This study shows for the first time the chronological interrelationship between gas migration events, hydrate formation, and sea floor shaping in a deep sea pockmark. © 2020. The Authors.
英文关键词	gas hydrate; MeBo; methane; pockmark; pore water modeling; pressure coring
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187590
作者单位	MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany; IFREMER, Département Ressources physiques et Ecosystèmes de fond de Mer (REM), Unité des Géosciences Marines, Plouzané, France; CAGE – Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology, UiT The Arctic University of Norway, Tromsø, Norway; Marine Geology, Geological Survey of Norway, Trondheim, Norway; Now at Department of Geological Sciences, Stockholm University, Stockholm, Sweden; Ocean Frontier Institute, Dalhousie University, Halifax, NS, Canada
推荐引用方式 GB/T 7714	Pape T.,Ruffine L.,Hong W.-L.,等. Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark—Quantities and Dynamics[J],2020,125(9).
APA	Pape T..,Ruffine L..,Hong W.-L..,Sultan N..,Riboulot V..,...&Bohrmann G..(2020).Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark—Quantities and Dynamics.Journal of Geophysical Research: Solid Earth,125(9).
MLA	Pape T.,et al."Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark—Quantities and Dynamics".Journal of Geophysical Research: Solid Earth 125.9(2020).