著者

Shinsuke Kawagucci Sanae Sakai Eiji Tasumi Miho Hirai Yoshihiro Takaki Takuro Nunoura Masafumi Saitoh Yuichiro Ueno Naohiro Yoshida Takazo Shibuya James Clifford Sample Tomoyo Okumura Ken Takai

出版者

Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.38, no.2, pp.ME22108, 2023 (Released:2023-06-16)

参考文献数

114

被引用文献数

1

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Post-mega-earthquake geochemical and microbiological properties in subseafloor sediments of the Japan Trench accretionary wedge were investigated using core samples from Hole C0019E, which was drilled down to 851‍ ‍m below seafloor (mbsf) at a water depth of 6,890 m. Methane was abundant throughout accretionary prism sediments; however, its concentration decreased close to the plate boundary decollement. Methane isotope systematics indicated a biogenic origin. The content of mole­cular hydrogen (H2) was low throughout core samples, but markedly increased at specific depths that were close to potential faults predicted by logging-while-drilling ana­lyses. Based on isotopic systematics, H2 appeared to have been abundantly produced via a low-temperature interaction between pore water and the fresh surface of crushed rock induced by earthquakes. Subseafloor microbial cell density remained constant at approximately 105‍ ‍cells‍ ‍mL–1. Amplicon sequences revealed that predominant members at the phylum level were common throughout the units tested, which also included members frequently found in anoxic subseafloor sediments. Metabolic potential assays using radioactive isotopes as tracers revealed homoacetogenic activity in H2-enriched core samples collected near the fault. Furthermore, homoacetogenic bacteria, including Acetobacterium carbinolicum, were isolated from similar samples. Therefore, post-earthquake subseafloor microbial communities in the Japan Trench accretionary prism appear to be episodically dominated by homoacetogenic populations and potentially function due to the earthquake-induced low-temperature generation of H2. These post-earthquake microbial communities may eventually return to the steady-state communities dominated by oligotrophic heterotrophs and hydrogenotrophic and methylotrophic methanogens that are dependent on refractory organic matter in the sediment.

著者

Kentaro Nakamura Shinsuke Kawagucci Kazuya Kitada Hidenori Kumagai Ken Takai Kyoko Okino

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.49, no.6, pp.579-596, 2015-11-26 (Released:2015-12-05)

参考文献数

40

被引用文献数

37 61

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Polymetallic sulfides deposited in seafloor hydrothermal vents have recently attracted attention as potential deep-sea mineral resources for base, rare, and precious metals such as Cu, Zn, Pb, In, Ga, Ge, Au, and Ag. For future exploitation of this type of deep-sea mineral resources, development of effective methods for exploring seafloor hydrothermal activity is a key to provide the most promising list of fields. However, conventional exploration methods are likely laborious and time-consuming, and a more efficient methods for exploration of seafloor hydrothermal vents are to be further developed. In the last decade, water column observation using multibeam echo souder (MBES) systems have become successfully applied to exploration of seafloor hydrothermal vents. In 2013 and 2014, we conducted extensive water column surveys using MBES systems in the mid-Okinawa Trough. During the surveys, we detected 10 hydrothermal vent sites, including previously known sites, belonging to four relatively large hydrothermal vent fields, located at the Izena Hole, Iheya North Knoll, Iheya Small Ridge, and a seamount 15 km northwest of the Izena Hole. All of the hydrothermal vent sites are in groups of 2–3 vent sites belonging to a hydrothermal field. Morphological features of the acoustic water column anomalies (rising vertically up to ~1000 m from the seafloor without a significant change of width) implied that the acoustic water column anomalies were not caused directly by hydrothermal vent fluid flows. The depth of the top of the acoustic water column anomalies (~500 m) corresponded rather well to the depth of the CO2 phase transition from liquid/clathrate-hydrate to vapor. This suggests that the acoustic water column anomalies are attributed to water mass including dense liquid CO2 droplets with clathrate-hydrate crusts, which are originally derived from the seafloor hydrothermal fluid discharges.

著者

JUN-ICHIRO ISHIBASHI TAKUROH NOGUCHI TOMOHIRO TOKI SHUNSUKE MIYABE SHOSEI YAMAGAMI YUJI ONISHI TOSHIRO YAMANAKA YUKA YOKOYAMA ERIKO OMORI YOSHIO TAKAHASHI KENTA HATADA YUZURU NAKAGUCHI MOTOKO YOSHIZAKI UTA KONNO TAKAZO SHIBUYA KEN TAKAI FUMIO INAGAKI SHINSUKE KAWAGUCCI

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.48, no.4, pp.357-369, 2014-07-20 (Released:2014-07-31)

参考文献数

48

被引用文献数

23 67

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Two active hydrothermal fields, Jade and Hakurei fields have been discovered within the Izena Hole, a rectangular 6 km × 3 km shape depression located in the middle Okinawa Trough back arc basin. In both fields, intense hydrothermal activity is represented by venting of high-temperature fluid (>300°C) and occurrence of sulfide/sulfate ore deposits. We collected hydrothermal fluids during dive expeditions of ROV Hyper Dolphin conducted in 2003, 2010 and 2011, in order to analyze both elemental and gas species. The geochemistry of high temperature hydrothermal fluids collected from the Jade and Hakurei fields is very similar to each other with exceptions in minor gas composition. Little temporal variation was observed in geochemistry of the high-temperature hydrothermal fluid of the Jade field over two decades, since a previous study carried out in 1989. These results suggest that these fluids are derived from a common fluid reservoir where fluid chemistry is basically controlled by fluid-mineral equilibria and gas species are dominantly contributed from the same magma. Venting of low temperature fluid (about 104°C) was discovered in the distal part of the Jade field, which was named as the Biwako vent. Chemical composition of the Biwako vent fluid was distinctive from that of the high temperature fluid in the proximal part of the Jade field, and could not be explained by simple dilution or cooling. This intra-field chemical diversity could be caused by phase separation and segregation during fluid upwelling, based on relationships in concentrations of Cl and major cations. On the other hand, the chemical diversity recognized in minor gas composition between the Jade and Hakurei fields is in accordance with results from previous plume survey. Difference in concentrations of minor gases such as H2 is attributed to contribution from thermal degradation of organic matter in the sediment, during fluid upwelling.

著者

SHINSUKE KAWAGUCCI KOTARO SHIRAI TEFANG FAITH LAN NAOTO TAKAHATA URUMU TSUNOGAI YUJI SANO TOSHITAKA GAMO

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.44, no.6, pp.507-518, 2010-12-20 (Released:2013-03-23)

参考文献数

60

被引用文献数

14 35

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Hydrothermal plumes above the HAKUREI and JADE sites, two high-temperature hydrothermal vent sites in the Izena Cauldron at the mid-Okinawa Trough, were investigated in order to gain a preliminary understanding of gas geochemical characteristics at underlying hydrothermal vent sites. Three geochemical tracers, H2, CH4 and δ3He, covary with each other above the HAKUREI site but only CH4 and δ3He are correlated above the JADE site. The carbon isotope ratio of methane within the Izena Cauldron can be accounted by a combination of the fluid dilution by ambient seawater and microbial consumption with the kinetic carbon isotope effect (KIE) of 1.007. An estimated endmember δ13C value of -32‰ in the HAKUREI fluid was obtained. Both the plumes above the HAKUREI and JADE sites showed C1/C2 ratios between 103∼104. Only the bottom water around the HAKUREI site showed significant N2O excess with isotopically light δ15N and δ18O, suggesting N2O input from microbial activity in the sediment. A linear correlation between H2 and CH4 in the HAKUREI plume gives a H2/CH4 ratio of the HAKUREI fluid of more than 0.022. The estimated H2/CH4 ratio in the HAKUREI fluid is significantly higher than that of the JADE fluid, comparable with those of fluids venting at other sediment-related hydrothermal systems, and also comparable with those of thermogenic gases produced by hydrothermal sediment experiments. These facts suggest that fluid-sediment interaction during fluid upwelling appears to modify gas geochemical characteristics at the HAKUREI site but have little influence at the JADE site. This study demonstrates the availability of the Izena Cauldron hydrothermal field and the HAKUREI and JADE sites as a natural laboratory for investigating the fluid-sediment interaction during fluid upwelling.

著者

UTA KONNO KEN TAKAI SHINSUKE KAWAGUCCI

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.47, no.4, pp.469-473, 2013-08-20 (Released:2013-11-26)

参考文献数

10

被引用文献数

1 2

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An analytical system using continuous-flow isotope ratio mass spectrometry (CF-IRMS) was developed to determine the stable chlorine isotope ratios (δ37Cl) for CH3Cl. By using appropriate devices for sample processing prior to introduction into the spectrometer, the newly developed system successfully reduces sample requirements (>0.6 nmol-CH3Cl) to less than one hundredth of that required by the previous CF-IRMS systems while maintaining comparable precision in the δ37Cl determination (±0.1‰, 1σ). This system is also able to determine carbon isotope ratio for CH3Cl with comparable precision (±0.3‰, 1σ, >0.3 nmol-CH3Cl) to the previous study. δ37ClSMOC and δ13CVPDB values of CH3Cl in commercial tank were determined to be -6.8 ± 0.1‰ and -46.9 ± 0.3‰, respectively.

著者

Shinsuke Kawagucci Yohei Matsui Gretchen L. Früh-Green

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.54, no.3, pp.129-138, 2020 (Released:2020-06-22)

参考文献数

45

被引用文献数

1 5

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Here we quantify radiocarbon (14C) content in CO2 and CH4 from hydrothermal fluids collected at 5 vent sites in the Okinawa Trough. These data provide preliminary insights on how different carbon sources and circulation processes contribute to vent fluids and take into consideration all potential contaminations during sample processing and analysis with accelerator mass spectrometer. For CO2, 14C-dead values observed in fluids of most sites (Hatoma, Hitoshi, Noho) demonstrate the complete removal of the inorganic carbon in the recharged seawater. Conversely, the significantly positive 14CO2 are detected in fluids from the Daiyon-Yonaguni site, which implies the persistence of the recharged seawater-derived inorganic carbon and/or a contribution from thermal degradation of sedimentary 14C-containing carbon during fluid upwelling. The CH4 in these fluids were predominantly 14C-dead or nearly 14C-dead, suggesting a source of deep-buried, 14C-dead sedimentary carbon. The methods outlined in our study exemplify a useful way of elucidating radiocarbon contents of geofluids, and provide future studies with a means to improve our understanding of carbon circulation between hydrosphere and lithosphere.