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Helium isotopes of seawater in adjacent sea of Nansei Islands, Southwest Japan

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Title: Helium isotopes of seawater in adjacent sea of Nansei Islands, Southwest Japan
Authors: Takahata, Naoto1 Browse this author
Watanabe, Tsuyoshi2 Browse this author →KAKEN DB
Shirai, Kotaro3 Browse this author
Nishizawa, Manabu4 Browse this author
Sano, Yuji5 Browse this author
Authors(alt): TAKAHATA, NAOTO1
Keywords: ^3He/^4He ratio
mantle helium
heavy noble gas
Okinawa Trough
Issue Date: 1-Dec-2004
Publisher: Geochemical Society of Japan
Journal Title: Geochemical journal
Volume: 38
Issue: 6
Start Page: 593
End Page: 600
Abstract: We have measured helium isotopic ratios of 43 water samples with various depths collected in Eastern East China Sea and Northwestern Philippine Sea, adjacent region of Nansei Islands, Southwestern Japan. The 3He/4He ratios vary significantly from 0.994 Ratm to 1.242 Ratm where Ratm is the atmospheric ratio of 1.39 × 10-6. Mid-depth (750-1500 m) samples in this study would be affected by the source of subduction-type mantle helium in the Okinawa Trough. Noble gas abundances (neon, argon, krypton and xenon) were measured in 24 water samples with various depths collected in Northwestern Pacific Ocean and Northwestern Philippine Sea (Nansei Trench). Neon abundances show slight excess relative to air saturated seawater at ambient temperature and salinity. This may be due to either air bubble effect or contamination during the sampling. When these effects are corrected using the neon anomaly, heavier noble gas abundances (argon, krypton and xenon) of samples with the temperature higher than 5°C (shallower than 500 m) agree well with those of calculated air saturated seawater, while the lower temperature samples (deeper than 500 m) indicate anomaly of -7% to +10%.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 渡邊 剛

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