Geochemistry of some gases in hydrothermal fluids from the southern Juan de Fuca Ridge

Journal of Geophysical Research
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Five samples of hydrothermal fluids from two vent areas on the southern Juan de Fuca Ridge were analyzed for dissolved gases. Concentrations in the end-member hydrothermal fluid of H2 (270-527 ??mol/kg), CH4 (82-118 ??mol/kg), and CO2 (3920-4460 ??mol/kg) are well above values in ambient seawater and are similar to concentrations reported for other ridge crest hydrothermal systems. The carbon isotopic ratios of the CH4(??13C=-17.8 to -20.8) and CO2(??13C=-3.6 to -4.7) suggest that at least some of the CH4 and CO2 in the fluids is basalt-derived. The range of ??13C values for the basalt-derived CO2 is -6.8 to -9.7, calculated by assuming conservation of recharge ??CO2 during hydrothermal circulation. Apparent temperatures of equilibration between the CH4 and the basalt-derived CO2 range from 640??C to 750??C. Small amounts of ethane (C2H6/CH4??? 0.9 ?? 10-3-2.2 ?? 10-3), propane, and butane detected in the samples may also have formed in the basalt. One sample of almost pure (95.5%) hydrothermal fluid contained a significant fraction, up to 63% and 74%, respectively, of the recharge Ar and N2. This suggests that the fluid has not undergone extensive vapor-liquid phase separation. -Authors
Publication type Article
Publication Subtype Journal Article
Title Geochemistry of some gases in hydrothermal fluids from the southern Juan de Fuca Ridge
Series title Journal of Geophysical Research
Volume 93
Issue B12
Year Published 1988
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research
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