Geochemistry of some gases in hydrothermal fluids from the southern Juan de Fuca Ridge
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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 μmol/kg), CH4 (82–118 μmol/kg), and CO2 (3920–4460 μmol/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 (δ13C = −17.8 to −20.8) and CO2 (δ13C = −3.6 to −4.7) suggest that at least some of the CH4 and CO2 in the fluids is basalt-derived. The range of δ13C values for the basalt-derived CO2 is −6.8 to −9.7, calculated by assuming conservation of recharge ΣCO2 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.
| 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 Solid Earth |
| DOI | 10.1029/JB093iB12p15305 |
| Volume | 93 |
| Issue | B12 |
| Year Published | 1988 |
| Language | English |
| Publisher | American Geophysical Union |
| Description | 9 p. |
| First page | 15305 |
| Last page | 15313 |
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