Original paper

Importance of fluid immiscibility in the H2O-NaCl-CO2 system and selective CO2 entrapment in granulites: experimental phase diagram at 5-7 kbar, 900°C and wetting textures

Gibert, François; Guillaume, Damien; Laporte, Didier

European Journal of Mineralogy Volume 10 Number 6 (1998), p. 1109 - 1124

59 references

published: Dec 1, 1998
manuscript accepted: May 19, 1998
manuscript received: Apr 6, 1998

DOI: 10.1127/ejm/10/6/1109

BibTeX file

ArtNo. ESP147051006003, Price: 29.00 €

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Abstract New experimental data on fluid immiscibility in the H2O-NaCl-CO2 system at 900°C and 5-7 kbar have been obtained using the synthetic fluid-inclusion technique. The main result is a significant enlargement of the immiscibility field as pressure decreases from 7 to 5 kbar. Combined with previous data, our experiments show that immiscibility is probably a widespread phenomenon in low-pressure granulite-facies rocks. Because CO2-rich fluids and Nad-rich aqueous fluids have very contrasting wetting behaviour, fluid unmixing could result in a selective entrapment of the CO2-rich component in granulites (Watson & Brenan, 1987). To check this hypothesis, we performed an experiment in which polycrystalline quartz was heat-treated in the presence of small volume percentages of the two immiscible fluids. The observed pore geometry is characterized by a combination of large, isolated CO2-rich bubbles, and an interconnected network of NaCl-H2O-filled channels along quartz edges. A model combining unmixing and the subsequent escape of the aqueous fluid by porous flow could therefore explain the CO2-rich fluid inclusions in low-pressure granulites


immiscibilityH2O-CO2-NaCl systemsynthetic fluid inclusionwetting texturegranulite facies