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Hydrogen isotopic compositions of hydrogen and methane from some volcanic areas in northeastern Japan

1983; Elsevier BV; Volume: 62; Issue: 1 Linguagem: Inglês

10.1016/0012-821x(83)90069-9

1385-013X

Yasuhiro Kiyosu,

Hydrocarbon exploration and reservoir analysis

D/H ratios of volcanic condensates, hydrogen and methane collected from Hachimantai, Zao¯, Azuma, Nasu and Kusatsu shirane volcanic areas in northeastern Japan were determined together with chemical components. On the basis of the isotopic ratios for volcanic condensates, it is concluded that most of the water vapor is essentially local surface water which has been heated and slightly enriched in18O by exchange with silicates. δD values of hydrogen and methane range from −220 to −515‰ (SMOW) and from −180 to −487‰ (SMOW), respectively. The D/H ratio in volcanic hydrogen indicates that hydrogen may have isotopically equilibrated with water vapor at temperatures between 200 and 400°C. The δD value of methane also suggests that volcanic methane has been in isotopic disequilibrium with the water vapor and hydrogen and that most of the methanes may be thermogenic methanes produced by pyrolysis of carbonaceous materials.