著者

Toshitaka Gamo Harue Masuda Toshiro Yamanaka Kei Okamura Junichiro Ishibashi Eiichiro Nakayama Hajime Obata Kiminori Shitashima Yoshiro Nishio Hiroshi Hasumoto Masaharu Watanabe Kyohiko Mitsuzawa Nobukazu Seama Urumu Tsunogai Fumitaka Kouzuma Yuji Sano

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.38, no.6, pp.527-534, 2004-12-20 (Released:2008-04-08)

参考文献数

31

被引用文献数

12 32

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This paper reports a series of studies leading to the discovery of a submarine hydrothermal field (called Nakayama Field) at an arc seamount (12°43′N, 143°32′E) in the southernmost part of the Mariana Trough, western Pacific Ocean. We first detected hydrothermal plumes characterized by water column anomalies of temperature, light transmission, Mn, Fe, Al, O2, CH4, and δ13C of CH4 above the summit caldera of the seamount. Then deep-tow camera surveys confirmed the existence of hydrothermal activity inside the caldera, and an ROV dive finally discovered white smoker-type fluid venting associated with vent fauna. A high concentration of aluminum in the plume and white smoker-type emissions imply acidic hydrothermal activity similar to that observed at the DESMOS Caldera in the eastern Manus Basin, Papua New Guinea. Anomalously low δ13C (CH4) of −38‰ of a vent fluid sample compared to other arc hydrothermal systems along the Izu-Bonin and Mariana Arcs suggests an incorporation of biogenic methane based on a subsurface microbial ecosystem.

著者

Toshitaka GAMO Kiminori SHITASHIMA

出版者

The Japan Academy

雑誌

Proceedings of the Japan Academy, Series B (ISSN:03862208)

巻号頁・発行日

vol.94, no.1, pp.45-55, 2018-01-11 (Released:2018-01-11)

参考文献数

35

被引用文献数

9

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Vertical profiles of potential temperature, salinity, and some chemical components were obtained at a trench station (29°05′N, 142°51′E; depth = 9768 m) in the Izu-Ogasawara (Bonin) Trench in 1984 and 1994 to characterize the hadal waters below ∼6000 m depth. We compared portions of both the 1984 and 1994 profiles with nearby data obtained between 1976 and 2013. Results demonstrated that the hadal waters had slightly higher potential temperature and nitrate and lower dissolved oxygen than waters at sill depths (∼6000 m) outside the trench, probably due to the effective accumulation of geothermal heat and active biological processes inside the trench. The silicate, iron, and manganese profiles in 1984 showed slight but significant increases below ∼6000 m depth, suggesting that these components may have been intermittently supplied from the trench bottom. Significant amounts of 222Rn in excess over 226Ra were detected in the hadal waters up to 2675 m from the bottom, reflecting laterally supplied 222Rn from the trench walls.