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Title :Origin of methane-rich natural gas at the West Pacific convergent plate boundary
Authors :Sano, Yuji
Kinoshita, Naoya
Kagoshima, Takanori
Takahata, Naoto
Sakata, Susumu
Toki, Tomohiro
Kawagucci, Shinsuke
Waseda, Amane
Lan, Tefang
Wen, Hsinyi
Chen, Ai-Ti
Lee, Hsiaofen
Yang, Tsanyao F.
Zheng, Guodong
Tomonaga, Yama
Roulleau, Emilie
Pinti, Daniele L.
Issue Date :15-Nov-2017
Abstract :Methane emission from the geosphere is generally characterized by a radiocarbon-free signature and might preserve information on the deep carbon cycle on Earth. Here we report a clear relationship between the origin of methane-rich natural gases and the geodynamic setting of the West Pacific convergent plate boundary. Natural gases in the frontal arc basin (South Kanto gas fields, Northeast Japan) show a typical microbial signature with light carbon isotopes, high CH4/C2H6 and CH4/3He ratios. In the Akita-Niigata region – which corresponds to the slope stretching from the volcanic-arc to the back-arc –a thermogenic signature characterize the gases, with prevalence of heavy carbon isotopes, low CH4/C2H6 and CH4/3He ratios. Natural gases from mud volcanoes in South Taiwan at the collision zone show heavy carbon isotopes, middle CH4/C2H6 ratios and low CH4/3He ratios. On the other hand, those from the Tokara Islands situated on the volcanic front of Southwest Japan show the heaviest carbon isotopes, middle CH4/C2H6 ratios and the lowest CH4/3He ratios. The observed geochemical signatures of natural gases are clearly explained by a mixing of microbial, thermogenic and abiotic methane. An increasing contribution of abiotic methane towards more tectonically active regions of the plate boundary is suggested.
URL :https://doi.org/10.1016/j.bbrc.2016.12.03610.1038/s41598-017-15959-5
Type Local :雑誌掲載論文
ISSN :2045-2322
Publisher :Nature Publishing Group
URI :http://hdl.handle.net/20.500.12000/37627
Citation :Scientific Reports Vol.7
Appears in Collections:Peer-reviewed Journal Articles (Faculty of Science)

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