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

Journal of Geophysical Research

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Abstract

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

Additional Publication Details

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