ABSTRACT

A simple gas chromatographic technique was developed for the determination of dissolved gases in the aqueous samples taken out from Dickson-type hydrothermal apparatus, and H₂ concentration was measured at temperatures below 500°C and pressures below 1, 000 bars in aqueous systems containing magnetite-hematite, Ni-NiO and fayalite-magnetite-quartz oxygen buffers. Oxygen-fugacity ratios between buffers A and B can be obtained by using a relation: f_O2 (A)/f_O2 (B) = [C_H2 (B)/C_H2 (A)]², where C_H2 (A) and C_H2 (B) are equilibrium H₂ concentrations in the systems A-water and B-water under the same P-T condition. Using a few f_O2 ratios thus obtained, corrections were evaluated for the f_O2–T relationships of the buffers given by a thermochemical compilation of ROBIE et al. (1979).