Abstract
The phase state of fluid in the H2O-NaF-Na2SO4 system in the presence of silicates (quartz and albite) was experimentally explored using the method of synthetic fluid inclusions in quartz at 700°C and pressures of 1 and 2 kbar. Parallel experiments were conducted under identical conditions with either two silicates (quartz and albite) or quartz only. The presence of albite affects heterogeneous fluid equilibria both at different pressures and at different solution compositions. This indicates high solubilities of silicates in a saltwater fluid containing NaF and Na2SO4. The absence of inclusions homogenizing to a gas phase in the experimental products provides compelling evidence that liquid-liquid rather than liquid-vapor equilibria are characteristic of the H2O-SiO2-NaF-Na2SO4 and H2O-SiO2-NaF-Na2SO4-NaAlSi3O2 systems in the heterogeneous region. It can be concluded that critical equilibria in saturated solutions can exist in these systems. In addition, it was shown that the phase diagrams of these systems are complicated by the formation of immiscible liquids in the presence of vapor. This allowed us to conclude that there are two critical curves describing equilibria with two different salts. Fluids containing two salts (NaF and Na2SO4) are similar to fluids containing only one of these salts: (a) two liquids are in equilibrium under the parameters of the upper heterogeneous region, (b) each of them can in turn undergo unmixing at decreasing temperature and pressure, and (c) owing to chemical interaction between silicate and fluid components, a glassy phase can be formed and trapped in inclusions.
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Z. A. Kotel’nikova and A. R. Kotel’nikov, “The phase state of NaF-containing fluid at 700°C and 1, 2, and 3 kbar (from the results of study of synthetic fluid inclusions in quartz),” Russ. Geol. Geophys., No. 11, 1666–1676 (2011).
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Original Russian Text © Z.A. Kotelnikova, A.R. Kotelnikov, 2014, published in Geokhimiya, 2014, No. 9, pp. 827–836.
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Kotelnikova, Z.A., Kotelnikov, A.R. Experimental evidence for the coexistence of two liquids in the H2O-SiO2-NaF-Na2SO4 System at T = 700°C and P = 2 kbar. Geochem. Int. 52, 758–766 (2014). https://doi.org/10.1134/S0016702914070039
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DOI: https://doi.org/10.1134/S0016702914070039