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Published Papers 【 display / non-display 】

Published Papers 【 display / non-display 】

• Sr isotopic ratios of hydrothermal fluids from the Okinawa Trough and the implications of variation in fluid–sediment interactions

  Tomohiro Toki, Tasuku Nohara, Yoshiaki Urata, Ryuichi Shinjo, Shuko Hokakubo-Watanabe, Jun-ichiro Ishibashi, and Shinsuke Kawagucci

  Progress in Earth and Planetary Science ( Springer Nature )  9 ( 1 ) 59   2022.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  沖縄トラフにおける海底熱水中のSr同位体比を比較すると，海水の混入を補正しても，海水よりもはるかに高い同位体比を示すことがわかった。このことから，海水よりもはるかに高い固体と反応していることが示唆され，沖縄トラフに供給されている大陸地殻を起源とする粘土鉱物と反応していることが示唆された。こういった高いSr同位体比は，堆積物が被覆している海底熱水系で見られる共通の特徴であると言える。

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• Origin of helium in basement rocks and carbonate veins in Yonaguni Island

  Toki, T; Yasumura, K; Takahata, N; Miyajima, Y; Miyaki, H; Oohashi, K; Otsubo, M

  GEOCHEMICAL JOURNAL ( 一般社団法人日本地球化学会 )  58 ( 6 ) 293 - 303   2024 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  <p>Minerals formed in high-temperature environments are distributed along faults on Yonaguni Island. Volcanic activity is thought to be a possible heat source. In this study, samples from the carbonate veins distributed around the basement rocks and faults of Yonaguni Island were melted in vacuum, and the concentrations and isotope ratios of the noble gases in the furnace were investigated. The observed isotope ratios suggest that the noble gases were dominated by crustal helium, with little influence from mantle helium. These results suggest that there was some kind of non-volcanic heat supply at Yonaguni Island (e.g., eruption of non-volcanic hot springs).</p>

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• Identification of a large mud volcano field in the Hyuga-nada, northern end of the Ryukyu trench, offshore Japan

  Asada, M; Yamashita, M; Fukuchi, R; Yokota, T; Toki, T; Ijiri, A; Kawamura, K

  FRONTIERS IN EARTH SCIENCE ( Frontiers in Earth Science )  11   2023.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  We identified 27 new mud volcanoes, including potential ones, in a part of the Hyuga-nada area, southwest offshore Japan, at the northern end of the Ryukyu Trench, based on subseafloor geological structures using geophysical investigations. These mud volcanoes exhibited high density and breadth and were likely connected to other mud volcano fields in the south. Acoustic investigations indicated subseafloor structures. Multiple acoustically transparent bodies were interpreted as a region containing gas. They were likely to appear along faults and below the bottom of valleys and sometimes reached the seafloor, expressing mud volcanoes onto the seafloor. They also indicated the wide distribution of subseafloor free-gas throughout the area. These acoustic investigations suggested that a swarm of mud volcanoes exists over the Hyuga-nada area, heterogeneously distributed along a series of plate convergent margins, the Nankai Trough, and the northern part of the Ryukyu Trench.

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• Distribution of dissolved methane in seawater from the East China Sea to the Ryukyu forearc

  Toki, T; Chibana, H; Shimabukuro, T; Yamakawa, Y

  FRONTIERS IN EARTH SCIENCE ( Frontiers in Earth Science )  11   2023.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Assessing the activity of mud volcanism using boron isotope ratios in pore water from surface sediments of mud volcanoes off Tanegashima (SW Japan)

  Mitsutome, Y; Agena, K; Toki, T; Song, KH; Shinjo, R; Ijiri, A

  FRONTIERS IN MARINE SCIENCE ( Frontiers in Marine Science )  10   2023.09 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Mud volcanoes can cause various geohazards, so it is very important to know their activity level and their distribution. Surface sediments were collected from four submarine mud volcanoes (MVs) off Tanegashima (SW Japan), namely, MV1, MV2, MV3, and MV14. We extracted pore water from the surface sediments and investigated its chemical and isotopic compositions. The sodium (Na) and chloride (Cl^-) concentrations decreased and the boron (B) and lithium (Li) concentrations increased with increasing depth, suggesting that some fluids with lower Na and Cl^- concentrations and higher B and Li concentrations than seawater were supplied upward from the deep sub-seafloor. The fluid advection velocities estimated from the pore-water profiles differed for each MV, and those of MV3 were the fastest (14 cm/yr) in this study. The estimated equilibrium temperature with clay minerals using Na and Li concentrations were 93-134°C, corresponding to the temperature of environments around 3.7 to 5.3 km below the seafloor. This indicates that these components originated from these depths and that the origin depth did not reach the plate boundary in this area. The B isotope ratio in the pore water was extremely high up to +57 ‰, suggesting that it was strongly affected by adsorption onto the surface of the sediments. A higher B isotope ratio (+57 ‰) was detected in MV3, which was considered to be more active, indicating that more B was adsorbed onto clay minerals supplied from deeper depths.

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Books 【 display / non-display 】

Books 【 display / non-display 】

• Nature in the Ryukyu Archipelago

  Tomohiro Toki ( Part: Single Author ,  When do you research hydrothermal systems? Now! )

  Change and Coral Reef/Island Dynamics Faculty of Science, University of the Ryukyus  2015

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  沖縄トラフの海底熱水研究の最新トピックをわかりやすく英語で紹介。

• Deep-sea Life - Biological observations using research submersibles

  Jun-ichiro Ishibashi, Tomhiro Toki ( Part: Multiple Authorship )

  Tokai University Press  2008.02

Other Papers 【 display / non-display 】

Other Papers 【 display / non-display 】

• Contribution and mission of geochemistry to mud volcano study

  Tomohiro Toki

  Bulletin of the Faculty of Science, University of the Ryukyus ( Faculty of Science, University of the Ryukyus )  ( 108 ) 1 - 26   2020.03

   

• 多良間海丘熱水活動域での鉄利用微生物の解明

  牧田寛子, 毛利諒子, 坂本貴大, 鈴木優美, 鹿島裕之, 宮崎淳一, CHEN Chong, 松井洋平, 吉梅剛, 山中寿朗, 倉場可織, 横田瑛里, 岡村慶, 野口拓郎, 中村謙太郎, 土岐知弘, 崎山智彦, 橋本泰志, 高村岳樹, 高井研

  ブルーアース要旨集   2018   88   2018

   

  J-GLOBAL

• 地質調査で採取された堆積物試料中の間隙水の地球化学的解析

  石橋純一郎, 正木裕香, 岡村慶, 野口拓郎, 土岐知弘, 新城竜一

  SIP 『次世代海洋資源調査技術』(海のジパング計画) 海底熱水鉱床の調査技術プロトコル     2017

   

• Simple method of collecting pyrolysis gas from bagasse

  Ryo Itou, Keiko Nakasone, Tomohiro Toki

  Bulletin of the Faculty of Science, University of the Ryukyus ( Faculty of Science, University of the Ryukyus )  ( 102 ) 1 - 11   2016.09

   

• Community structure of a microbial mat from the methane seep off Yagaji Island

  Tomohiro Toki, Hisako Hirayama, Syogo Oshima

  Bulletin of the Faculty of Science, University of the Ryukyus ( Faculty of Science, University of the Ryukyus )  ( 100 ) 5 - 12   2015.09

   

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Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Origin of fluids in surface sediments of submarine mud volcanoes off Hyuga-nada, Tanegashima Island, and Kikaijima Island

  Kantaro Yamada, Tomohiro Toki, Hironori Otsuka, Takuya Itaki, Masafumi Murayama, Akira Ijiri

  Abstracts of Annual Meeting of the Geochemical Society of Japan  2024  -  2024 

  CiNii Research

• A Future-Oriented Trial Using Board Games Produced by Residents on Yoron Island

  Toki Tomohiro, Shimabukuro Miyuki, Shimabukuro Hitoshi, Kubo Yoshiaki

  Proceeding of Annual Conference  2023  -  2023 

  CiNii Research

• Cold axis or Hot axis? Investigating the geothermal structure of a pre-break-up backarc basin, southern part of Okinawa Trough

  Otsubo Makoto, Arai Ryuta, Toki Tomohiro, Kinoshita Masataka, Misawa Ayanori, Oohashi Kiyokazu, Kubota Yoshimi, Miyakawa Ayumu, Ikegami Fumihiko, Regalla Christine, Su Chih-Chieh

  Annual Meeting of the Geological Society of Japan  2022  -  2022 

  CiNii Research

• The roots of helium in surface sediments of submarine mud volcanoes off Tanegashima

  Yuki Mitsutome, Tomohiro Toki, Takanori Kagoshima, Naoto Takahata, Yuji Sano, Yama Tomonaga, Akira Ijiri

  AGU Fall Meeting 2021  (New Orleans, LA & Online Everywhere)  2021.12  -  2021.12 

• Roots and reservoir of venting fluid at Taketomi submarine hot spring

  Tomohiro Toki, Ryuichi Shinjo, Yuki Mitsutome, Syogo Oushima, Harue Masuda, Akira Ijiri, Shinji Nakaya

  AGU Fall Meeting 2021  (New Orleans, LA & Online Everywhere)  2021.12  -  2021.12 

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Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Can seamount subduction weaken locking of megathrust earthquake? Test at 2 seamounts in Nankai Trough

  Grant-in-Aid for Scientific Research(S)

  Project Year: 2024.04  -  2029.03 

  Direct: 152,900,000 (YEN)  Overheads: 198,770,000 (YEN)  Total: 45,870,000 (YEN)

• Geosphere-hydrosphere-biosphere connected by submarine mud volcanism: Diffusion processes of deep life and carbon, and their effects on the ocean

  Grant-in-Aid for Scientific Research(A)

  Project Year: 2024.04  -  2029.03 

  Direct: 36,800,000 (YEN)  Overheads: 47,840,000 (YEN)  Total: 11,040,000 (YEN)

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2023.04  -  2027.03 

  Direct: 3,600,000 (YEN)  Overheads: 4,680,000 (YEN)  Total: 1,080,000 (YEN)

• Fluid flow in the uppermost part of the incoming plate seaward of the trench: Regional variations and influence on processes around the plate interface

  Grant-in-Aid for Scientific Research(B)

  Project Year: 2023.04  -  2026.03 

  Direct: 14,400,000 (YEN)  Overheads: 18,720,000 (YEN)  Total: 4,320,000 (YEN)

• Construction of a model for the diffusion and circulation of deep subsurface life and carbon to the ocean via submarine mud volcanism

  Grant-in-Aid for Scientific Research(B)

  Project Year: 2020.04  -  2023.03 

  Direct: 13,500,000 (YEN)  Overheads: 17,550,000 (YEN)  Total: 4,050,000 (YEN)

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Other External funds 【 display / non-display 】

Other External funds 【 display / non-display 】

• Project Name: Research Project

  Project Year: 2019.04  -  2027.03 

  Offer Organization: Research Institute for Humanity and Nature

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