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Wen HY, Sano Y, Takahata N, Tomonaga Y, Ishida A, Tanaka K, Kagoshima T, Shirai K, Ishibashi JI, Yokose H, Tsunogai U, Yang TF. Helium and methane sources and fluxes of shallow submarine hydrothermal plumes near the Tokara Islands, Southern Japan. Sci Rep 2016; 6:34126. [PMID: 27671524 PMCID: PMC5037448 DOI: 10.1038/srep34126] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 09/02/2016] [Indexed: 11/29/2022] Open
Abstract
Shallow submarine volcanoes have been newly discovered near the Tokara Islands, which are situated at the volcanic front of the northern Ryukyu Arc in southern Japan. Here, we report for the first time the volatile geochemistry of shallow hydrothermal plumes, which were sampled using a CTD-RMS system after analyzing water column images collected by multi-beam echo sounder surveys. These surveys were performed during the research cruise KS-14-10 of the R/V Shinsei Maru in a region stretching from the Wakamiko Crater to the Tokara Islands. The 3He flux and methane flux in the investigated area are estimated to be (0.99–2.6) × 104 atoms/cm2/sec and 6–60 t/yr, respectively. The methane in the region of the Tokara Islands is a mix between abiotic methane similar to that found in the East Pacific Rise and thermogenic one. Methane at the Wakamiko Crater is of abiotic origin but affected by isotopic fractionation through rapid microbial oxidation. The helium isotopes suggest the presence of subduction-type mantle helium at the Wakamiko Crater, while a larger crustal component is found close to the Tokara Islands. This suggests that the Tokara Islands submarine volcanoes are a key feature of the transition zone between the volcanic front and the spreading back-arc basin.
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Affiliation(s)
- Hsin-Yi Wen
- Department of Geosciences, National Taiwan University, Taiwan.,Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | - Yuji Sano
- Department of Geosciences, National Taiwan University, Taiwan.,Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | - Naoto Takahata
- Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | - Yama Tomonaga
- Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | - Akizumi Ishida
- Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | - Kentaro Tanaka
- Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | | | - Kotaro Shirai
- Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
| | | | - Hisayoshi Yokose
- Graduate School of Science and Technology, Kumamoto University, Japan
| | - Urumu Tsunogai
- Graduate School of Environmental Studies, Nagoya University, Japan
| | - Tsanyao F Yang
- Department of Geosciences, National Taiwan University, Taiwan
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Helium anomalies suggest a fluid pathway from mantle to trench during the 2011 Tohoku-Oki earthquake. Nat Commun 2015; 5:3084. [PMID: 24430337 DOI: 10.1038/ncomms4084] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 12/10/2013] [Indexed: 11/09/2022] Open
Abstract
Geophysical evidence suggests that fluids along fault planes have an important role in generating earthquakes; however, the nature of these fluids has not been well defined. The 2011 magnitude 9.0 Tohoku-Oki earthquake ruptured the interface between the subducting Pacific plate and the overlying Okhotsk plate. Here we report a sharp increase in mantle-derived helium in bottom seawater near the rupture zone 1 month after the earthquake. The timing and location indicate that fluids were released from the mantle on the seafloor along the plate interface. The movement of the fluids was rapid, with a velocity of ~4 km per day and an uncertainty factor of four. This rate is much faster than what would be expected from pressure-gradient propagation, suggesting that over-pressurized fluid is discharged along the plate interface.
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Sano Y, Fischer TP. The Analysis and Interpretation of Noble Gases in Modern Hydrothermal Systems. ADVANCES IN ISOTOPE GEOCHEMISTRY 2013. [DOI: 10.1007/978-3-642-28836-4_10] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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