Original paper

High-pressure fluid-absent melting experiments in the presence of graphite: oxygen fugacity, ferric/ferrous ratio and dissolved CO2

Holloway, John R.; Pan, Vivian; Gudmundsson, Gisli

European Journal of Mineralogy Volume 4 Number 1 (1992), p. 105 - 114

36 references

published: Feb 13, 1992
manuscript accepted: May 14, 1991
manuscript received: Nov 2, 1990

DOI: 10.1127/ejm/4/1/0105

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ArtNo. ESP147050401009, Price: 29.00 €

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Abstract

Abstract Graphite capsules are commonly used to prevent loss of iron from iron-bearing samples in high-pressure melting experiments. The graphite is not inert in such experiments and reacts with Fe2O3 in the melt to form dissolved CO2 and FeO. This equilibrium can be quantified if the activity-composition relations of CO2 in the melt are known. The presence of graphite is shown to limit the maximum ƒO2 possible, but places no limit on the minimum ƒO2. The ƒO2 in the system, the ferric/ferrous ratio in the melt, and the concentration of dissolved CO2 are proportional to the concentration of ferric iron in the starting material. The dissolved CO2 content cannot be controlled independently of ƒO2, but for values of ƒO2 appropriate to mantle melting, the amount of dissolved CO2 can be controlled over values ranging from about 0.1 wt% to saturation

Keywords

high pressuremeltingexperimentsredoxthermodynamics