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Article ; Online: Estimation of the depth of origin of fluids using noble gases in the surface sediments of submarine mud volcanoes off Tanegashima Island

Yuki Mitsutome / Tomohiro Toki / Takanori Kagoshima / Yuji Sano / Yama Tomonaga / Akira Ijiri

Scientific Reports, Vol 13, Iss 1, Pp 1-

2023 Volume 12

Abstract: Abstract The helium isotope ratio (3He/4He), concentration ratio of neon-20 to helium-4 (20Ne/4He), argon (Ar), krypton (Kr), and xenon (Xe) concentrations were measured in the porewater of surface sediments of several submarine mud volcanoes. From the ... ...

Abstract	Abstract The helium isotope ratio (3He/4He), concentration ratio of neon-20 to helium-4 (20Ne/4He), argon (Ar), krypton (Kr), and xenon (Xe) concentrations were measured in the porewater of surface sediments of several submarine mud volcanoes. From the 3He/4He values (0.18–0.93RA), the estimated He origin is almost 90% crustal He, with little contribution from mantle-derived He. The determined Ar, Kr, and Xe concentrations lie within the solubility equilibrium range expected for temperatures from 83 °C up to 230 °C and are consistent with the temperature range of the dehydration origin of clay minerals. Considering the geothermal gradient in the investigated region (25 °C/km), these gases are considered to have reached dissolution equilibrium at a depth of about 3.3 km to 9.2 km below the seafloor. As the depth of the plate boundary is 18 km below the seafloor, the noble gas signatures are likely to originate from the crust, not from the plate boundary. This is consistent with the results presented by the He isotope ratios.
Keywords	Medicine ; R ; Science ; Q
Subject code	550
Language	English
Publishing date	2023-04-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Author Correction

Takako Masuda / Keisuke Inomura / Naoto Takahata / Takuhei Shiozaki / Yuji Sano / Curtis Deutsch / Ondřej Prášil / Ken Furuya

Communications Biology, Vol 6, Iss 1, Pp 1-

Heterogeneous nitrogen fixation rates confer energetic advantage and expanded ecological niche of unicellular diazotroph populations

2023 Volume 1

Keywords	Biology (General) ; QH301-705.5
Language	English
Publishing date	2023-06-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Older magma at Aso caldera than at Unzen stratovolcano in south west Japan as recorded through helium isotopes

Yuji Sano / Takanori Kagoshima / Maoliang Zhang / Naoto Takahata / Tetsuji Onoue / Tomo Shibata / Yoshiro Nishio / Ai-Ti Chen / Hyunwoo Lee / Tobias P. Fischer / Dapeng Zhao

Communications Earth & Environment, Vol 4, Iss 1, Pp 1-

2023 Volume 8

Abstract: Helium isotopes from groundwater and hot springs at the stratovolcano, Unzen, have a stronger mantle signature than for the nearby caldera volcano, Aso, which suggests that magma at Unzen is younger still supplied with primordial mantle helium. ...

Abstract	Helium isotopes from groundwater and hot springs at the stratovolcano, Unzen, have a stronger mantle signature than for the nearby caldera volcano, Aso, which suggests that magma at Unzen is younger still supplied with primordial mantle helium.
Keywords	Geology ; QE1-996.5 ; Environmental sciences ; GE1-350
Language	English
Publishing date	2023-01-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Seismic Reflection Images of Possible Mantle-Fluid Conduits and Basal Erosion in the 2011 Tohoku Earthquake Rupture Area

Jin-Oh Park / Tetsuro Tsuru / Gou Fujie / Ehsan Jamali Hondori / Takanori Kagoshima / Naoto Takahata / Dapeng Zhao / Yuji Sano

Frontiers in Earth Science, Vol

2021 Volume 9

Abstract: Multi-channel seismic reflection and sub-bottom profiling data reveal landward-dipping normal faults as potential conduits for mantle-derived fluids in the coseismic slip area of the 2011 Tohoku earthquake (Mw9.0). Normal faults below the helium isotope ... ...

Abstract	Multi-channel seismic reflection and sub-bottom profiling data reveal landward-dipping normal faults as potential conduits for mantle-derived fluids in the coseismic slip area of the 2011 Tohoku earthquake (Mw9.0). Normal faults below the helium isotope anomaly sites appear to develop through the forearc crust (i.e., the seafloor sedimentary section and Cretaceous basement) and to evolve to lower dip angles as extension progresses deeper, potentially extending down to the mantle wedge, despite their intermittently continuous reflections. The faults are characterized by high-amplitude, reverse-polarity reflections within the Cretaceous basement. Moreover, deep extension of the faults connecting to a low-velocity region spreading from the Cretaceous basement into the mantle wedge across the forearc Moho suggests that the faults are overpressured by local filling with mantle-derived fluids. The locations of the normal faults are roughly consistent with aftershocks of the 2011 Tohoku earthquake, which show normal-faulting focal mechanisms. The 2011 Tohoku mainshock and subsequent aftershocks can lead the pre-existing normal faults to be reactive and more permeable so that locally trapped mantle fluids can migrate up to the seafloor through fault fracture zones. The reactivated normal faults may be an indicator of shallow coseismic slip to the trench. Locally elevated fluid pressures can decrease the effective normal stress for the fault plane, facilitating easier slip along the fault and local tsunami. The landward-dipping normal faults developing from the seafloor down into the Cretaceous basement are predominant in the middle slope region of the forearc. A possible shear zone with high-amplitude, reverse-polarity reflections above the plate interface, which is almost localized to the middle slope region, suggests more intense basal erosion of the overlying plate in that region.
Keywords	fluid migration ; seismic reflection ; normal fault ; shallow coseismic slip ; basal erosion ; Science ; Q
Subject code	550
Language	English
Publishing date	2021-07-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Mantle degassing along strike-slip faults in the Southeastern Korean Peninsula

Hyunwoo Lee / Heejun Kim / Takanori Kagoshima / Jin-Oh Park / Naoto Takahata / Yuji Sano

Scientific Reports, Vol 9, Iss 1, Pp 1-

2019 Volume 9

Abstract: Abstract On September 12, 2016, a ML 5.8 earthquake hit Gyeongju in the southeastern part of the Korean Peninsula (SeKP), although the area is known to be far from the boundary of the active plate. A number of strike-slip faults are observed in heavily ... ...

Abstract	Abstract On September 12, 2016, a ML 5.8 earthquake hit Gyeongju in the southeastern part of the Korean Peninsula (SeKP), although the area is known to be far from the boundary of the active plate. A number of strike-slip faults are observed in heavily populated city areas (e.g., Busan, Ulsan, Pohang, and Gyeongju). However, dissolved gases related to the active faults have rarely been studied despite many groundwater wells and hot springs in the area. Here we report new results of gas compositions and isotope values of helium and carbon dioxide (CO2) in fault-related fluids in the region. Based on gas geochemistry, the majority of gas samples are abundant in CO2 (up to 99.91 vol.%). Measured 3He/4He ratios range from 0.07 to 5.66 Ra, showing that the mantle contribution is up to 71%. The range of carbon isotope compositions (δ13C) of CO2 is from −8.25 to −24.92‰, showing mantle-derived CO2 is observed coherently where high 3He/4He ratios appear. The weakening of faults seems to be related to enhanced pressures of fluids containing mantle-derived helium and CO2 despite the ductile lower crust underneath the region. Thus, we suggest that the SeKP strike-slip faults penetrate into the mantle through ductile shearing.
Keywords	Medicine ; R ; Science ; Q
Subject code	550
Language	English
Publishing date	2019-10-01T00:00:00Z
Publisher	Nature Publishing Group
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: High nitrogen solubility in stishovite (SiO2) under lower mantle conditions

Ko Fukuyama / Hiroyuki Kagi / Toru Inoue / Sho Kakizawa / Toru Shinmei / Shunichi Hishita / Naoto Takahata / Yuji Sano

Scientific Reports, Vol 10, Iss 1, Pp 1-

2020 Volume 8

Abstract: Abstract Nitrogen is a crucial volatile element in the early Earth’s evolution and the origin of life. Despite its importance, nitrogen’s behavior in the Earth's interior remains poorly understood. Compared to other volatile elements, nitrogen is ... ...

Abstract	Abstract Nitrogen is a crucial volatile element in the early Earth’s evolution and the origin of life. Despite its importance, nitrogen’s behavior in the Earth's interior remains poorly understood. Compared to other volatile elements, nitrogen is depleted in the Earth’s atmosphere (the so-called “missing nitrogen”), calling for a hidden deep reservoir. To investigate nitrogen’s behavior in the deep Earth including how the reservoir formed, high-pressure and high-temperature experiments were conducted at 28 GPa and 1,400–1,700 °C. To reproduce the conditions in the lower mantle, the redox was controlled using a Fe–FeO buffer. We observed that depending on the temperature conditions, stishovite can incorporate up to 90–404 ppm nitrogen, experimentally demonstrating that stishovite has the highest nitrogen solubility among the deep mantle minerals. Stishovite is the main mineral component of subducted nitrogen-rich sedimentary rocks and eroded continental crust that are eventually transported down to the lower mantle. Our results suggest that nitrogen could have been continuously transported into the lower mantle via subduction, ever since plate tectonics began.
Keywords	Medicine ; R ; Science ; Q
Subject code	550
Language	English
Publishing date	2020-07-01T00:00:00Z
Publisher	Nature Publishing Group
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Coseismic changes in groundwater level during the 2018 Hokkaido Eastern Iburi earthquake

Tomo Shibata / Ryo Takahashi / Hiroaki Takahashi / Takanori Kagoshima / Naoto Takahata / Yuji Sano / Daniele L. Pinti

Earth, Planets and Space, Vol 72, Iss 1, Pp 1-

2020 Volume 8

Abstract: Abstract Six wells were continuously monitored in Hokkaido, northern Japan, to relate groundwater level changes to regional seismic activity. Groundwater level changes following the 2018 Hokkaido Eastern Iburi earthquake were detected in three of the six ...

Abstract	Abstract Six wells were continuously monitored in Hokkaido, northern Japan, to relate groundwater level changes to regional seismic activity. Groundwater level changes following the 2018 Hokkaido Eastern Iburi earthquake were detected in three of the six wells, even though they are located hundreds of kilometers from the epicenter. The groundwater level changes are qualitatively consistent with the volumetric strain induced by the earthquake. We analyzed groundwater level responses to the M2 tidal constituent before and after the earthquake, but related changes in amplitude and phase shifts remained within the usual variation. Observed coseismic change was explained by the response to the M2 tidal constituent component and the calculated volumetric strain for one of the wells, where groundwater level decreased. The observed change in the other two was found to be much greater than the corresponding estimates of the volumetric strain.
Keywords	Groundwater level ; Coseismic change ; 2018 Hokkaido Eastern Iburi earthquake ; Tidal response ; Geography. Anthropology. Recreation ; G ; Geodesy ; QB275-343 ; Geology ; QE1-996.5
Subject code	550
Language	English
Publishing date	2020-02-01T00:00:00Z
Publisher	SpringerOpen
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Distribution of helium-3 plumes and deep-sea circulation in the central Indian Ocean

Naoto Takahata / Kotaro Shirai / Kazuto Ohmori / Hajime Obata / Toshitaka Gamo / Yuji Sano

Terrestrial, Atmospheric and Oceanic Sciences, Vol 29, Iss 3, Pp 331-

2018 Volume 340

Abstract: We report helium isotope data collected in the central Indian Ocean, from the Arabian Sea to the Southern Ocean, during a Japanese GEOTRACES cruise in 2009 - 2010. We found hydrothermal helium-3 plumes and confirmed that 3He/4He ratio anomalies were ... ...

Abstract	We report helium isotope data collected in the central Indian Ocean, from the Arabian Sea to the Southern Ocean, during a Japanese GEOTRACES cruise in 2009 - 2010. We found hydrothermal helium-3 plumes and confirmed that 3He/4He ratio anomalies were almost the same as those observed in WOCE cruises conducted in 1990s, which indicates the hydrothermal activity and abyssal currents have not changed largely for the last few decades. Maximum δ3He value over 14% was observed at mid-depth (2000 - 3000 m) in the northern part (north of 30°S) in the central Indian Ocean, whereas lower δ3He was found in the southern part at the same depth, where δ3He is defined as the percent deviation of the helium isotopic ratio relative to the atmospheric standard. The vertical distribution of δ3He shows a similar trend with dissolved iron and manganese distributions in the hydrothermal plume. Lateral δ3He distribution at mid-depth using our GEOTRACES data together with WOCE data suggest that the helium-3 plume in the central Indian Ocean derived from the Central Indian Ridge around 20°S. It does not flow northward along the ridge but flows eastward as previously reported. The source of the helium-3 plume observed in the region adjacent to the Indian subcontinent might be in the Gulf of Aden as inferred from water properties. The δ3He distribution could reveal clockwise deep-water circulation in the Arabian Sea.
Keywords	Geography (General) ; G1-922 ; Geology ; QE1-996.5
Subject code	551
Language	English
Publishing date	2018-01-01T00:00:00Z
Publisher	Chinese Geoscience Union
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Importance of seagrass-mangrove continuum as feeding grounds for juvenile pink ear emperor Lethrinus lentjan in Setiu Lagoon, Malaysia: Stable isotope approach

Le, Dung Quang / Kentaro Tanaka / Kotaro Shirai / Kusuto Nanjo / Yii Siang Hii / Yuji Sano

Journal of sea research. 2018 May, v. 135

2018

Abstract: The commercially important pink ear emperor fish, Lethrinus lentjan, often occurs as a juvenile in subtropical and tropical interlinked mangrove and seagrass ecosystems, but little is known about its feeding habits and habitat use. Here, we used gut ... ...

Abstract	The commercially important pink ear emperor fish, Lethrinus lentjan, often occurs as a juvenile in subtropical and tropical interlinked mangrove and seagrass ecosystems, but little is known about its feeding habits and habitat use. Here, we used gut contents and stable isotopic (Î´Â¹Â³C and Î´Â¹âµN) ratios to determine temporal changes in food sources and foraging habits of juvenile and sub-adult fish collected in mangrove forests and seagrass beds in the Setiu Lagoon. Gut content examination identified the main food sources as crustaceans, gastropods, bivalves, and annelids. Stable isotope analysis of food sources showed marked differences between the mangroves (Î´Â¹Â³Câ¯=â¯â26.8â¯Â±â¯2.0â°; Î´Â¹âµNâ¯=â¯4.3â¯Â±â¯1.7â°) and the seagrasses (meanâ¯Â±â¯S.D. Î´Â¹Â³Câ¯=â¯â20.5â¯Â±â¯5.5â°; Î´Â¹âµNâ¯=â¯5.8â¯Â±â¯1.2â°). The isotopic composition of L. lentjan revealed that it mainly utilized seagrass-based food sources. Rainfall and the semi-diurnal tidal regimes may affect the foraging habitats of fish in the lagoon. A significant depletion of Â¹Â³C related to body size was observed, suggesting that mangroves provided some benefits to sub-adult fish. In contrast, trophic position increased with fish growth, although this increase was negligible. A stable isotope mixing model confirmed that the seagrass bed constituted the main carbon source for the fish, but with an increasing contribution of mangrove prey, such as sesarmid crabs, related to fish growth. This study provided novel information on seasonal variations in feeding areas and flexible habitat use in L. lentjan in the Setiu Lagoon, which will help optimize management strategies for sustainable use and wildlife conservation.
Keywords	animal growth ; Annelida ; Bivalvia ; body size ; carbon ; crabs ; Crustacea ; digestive system ; ecosystems ; fish ; foraging ; Gastropoda ; habitat preferences ; habitats ; juveniles ; Lethrinus ; mangrove forests ; mangroves ; nitrogen ; rain ; seagrasses ; seasonal variation ; stable isotopes ; statistical models ; wildlife management ; Malaysia
Language	English
Dates of publication	2018-05
Size	p. 1-10.
Publishing place	Elsevier B.V.
Document type	Article
ISSN	1385-1101
DOI	10.1016/j.seares.2018.02.004
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Mantle-derived helium released through the Japan trench bend-faults

Jin-Oh Park / Naoto Takahata / Ehsan Jamali Hondori / Asuka Yamaguchi / Takanori Kagoshima / Tetsuro Tsuru / Gou Fujie / Yue Sun / Juichiro Ashi / Makoto Yamano / Yuji Sano

Scientific Reports, Vol 11, Iss 1, Pp 1-

2021 Volume 9

Abstract: Abstract Plate bending-related normal faults (i.e. bend-faults) develop at the outer trench-slope of the oceanic plate incoming into the subduction zone. Numerous geophysical studies and numerical simulations suggest that bend-faults play a key role by ... ...

Abstract	Abstract Plate bending-related normal faults (i.e. bend-faults) develop at the outer trench-slope of the oceanic plate incoming into the subduction zone. Numerous geophysical studies and numerical simulations suggest that bend-faults play a key role by providing pathways for seawater to flow into the oceanic crust and the upper mantle, thereby promoting hydration of the oceanic plate. However, deep penetration of seawater along bend-faults remains controversial because fluids that have percolated down into the mantle are difficult to detect. This report presents anomalously high helium isotope (3He/4He) ratios in sediment pore water and seismic reflection data which suggest fluid infiltration into the upper mantle and subsequent outflow through bend-faults across the outer slope of the Japan trench. The 3He/4He and 4He/20Ne ratios at sites near-trench bend-faults, which are close to the isotopic ratios of bottom seawater, are almost constant with depth, supporting local seawater inflow. Our findings provide the first reported evidence for a potentially large-scale active hydrothermal circulation system through bend-faults across the Moho (crust-mantle boundary) in and out of the oceanic lithospheric mantle.
Keywords	Medicine ; R ; Science ; Q
Subject code	550
Language	English
Publishing date	2021-06-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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