A simple gas analytical technique for the Dickson-type hydrothermal apparatus and its application to the calibration of MH, NNO and FMQ oxygen buffers

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: fO2(A)/fO2(B) = [ch2(b)/ch2(A)]2 where ch2 (A) and ch2(B) are equilibrium H2 concentrations in the systems A-water and B-water under the same P-T condition, Using a few fO2ratios thus obtained, corrections were evaluated for the fO2-T relationships of the buffers given by a thermochemical compilation of Robie et al. (1979). © 1984, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.