日本海海水中のヘリウム同位体比

概要

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We have measured ^3He/^4He and ^4He/^<20>Ne ratios, and ^4He concentrations in water samples collected at several depths in the eastern Japan Sea. Observed ^3He/^4He and ^4He/^<20>Ne ratios vary from 1.006R_<atm> (where R_<atm> is atmospheric ratio of 1.343×1O^<-6>) to 1.045 R_<atm> and from 0.24 to 0.31, respectively. There is a difference in ^4He concentration between in the samples shallower than 1,500m and those deeper than 2,000m. The discrepancy may be related to the existence of two water masses in the Japan Sea suggested by Gamo and Horibe (1983). Excess ^3He in the shallower samples is attributable to tritium decay in the sea water while that in the deeper samples is not. Emanation of mantle helium is suggested in the Japan Sea bottom. Since the number of present data is small, extensive ^3He/^4He research should be carried out in future to verify the existence of mantle helium in the Jpan Sea.
日本地球化学会の論文
1989-12-30