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

WEN HSINYI Naoto Takahata Akizumi Ishida Kentaro Tanaka Yama Tomonaga Takanori Kagoshima Kotaro Shirai Jun-Ichiro Ishibashi Hisayoshi Yokose Urumu Tsunogai Yuji Sano

出版者

日本地球化学会

雑誌

日本地球化学会年会要旨集

巻号頁・発行日

vol.61, 2014

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The aim of this study is to get information of gas geochemical characteristics at hydrothermal vent sites in the adjacent region of Tokara Islands by using helium isotopes and methane concentration and its stable carbon isotope ratio to estimate the 3He flux and understand the mechanism of carbon cycling.

著者

Yuji SANO Kotaro SHIRAI Naoto TAKAHATA Takafumi HIRATA Neil C. STURCHIO

出版者

The Japan Society for Analytical Chemistry

雑誌

Analytical Sciences (ISSN:09106340)

巻号頁・発行日

vol.21, no.9, pp.1091-1097, 2005 (Released:2006-01-10)

参考文献数

34

被引用文献数

43 45

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Concentrations of minor (Mg and Sr) and trace (Ba and U) elements in four natural calcium carbonate samples were first analyzed by inductively coupled plasma mass spectrometry (ICP-MS) after chemical dissolution and calibrated against a standard dolomite. Their homogeneities were checked by in situ laser ablation (LA) ICP-MS with 10 - 20 spots. The carbonate samples were measured by using a high lateral resolution secondary ion mass spectrometer (Nano-SIMS NS50). A ∼4 nA O- primary beam was used to sputter a 5 - 6-µm diameter crater on the sample surface, and secondary positive ions were extracted for mass analysis using an accelerating voltage of 8 kV and a Mattauch-Herzog geometry. A multi-collector system was adjusted to detect 26Mg+, 43Ca+, 88Sr+, 138Ba+, 238U16O+ and 238U16O2+ ions at the same time. A resolving power of 2500 - 5000 at 10% peak height was attained by an entrance slit set at 40 µm, and each exit slit at 50 µm with adequate flat-topped peaks. The observed 26Mg/43Ca, 88Sr/43Ca, 138Ba/43Ca and 238U16O2/43Ca ratios agreed well with those measured by LA-ICP-MS. Foraminifera shells were analyzed at 5 - 6 µm scale by Nano-SIMS. There was a large variation of the Mg/Ca ratios, up to ±38%, even in a single fragment of the shell, suggesting that although the ratios provide a useful paleoceanographic proxy at bulk scale, they may reflect a more complex pattern at <10 µm scale.