HR: 16:45h
AN: V34A-04    [Abstracts]
TI: Experimental determination of the critical PVTX properties of H$_{2}$O-NaCl-KCl-CaCl$_{2}$ brines
AU: * Azbej, T
EM: tazbej@vt.edu
AF: Virginia Tech, Dept of Geosciences, 4044 Derring Hall, Blacksburg, VA 24061 United States
AU: Bodnar, R J
EM: rjb@vt.edu
AF: Virginia Tech, Dept of Geosciences, 4044 Derring Hall, Blacksburg, VA 24061 United States
AB: Near-critical and supercritical fluids are of great scientific interest because of their unique thermodynamic and physical properties, such as anomalously high heat capacity, large compressibility, low viscosity versus density ratio, high diffusivity and light scattering. Geochemists - among other scientists - have long studied these characteristics to understand the role of critical and supercritical fluids in various geological environments. Such fluids play an important role in numerous geologic processes. Supercritical fluids are important mass transfer media in hydrothermal systems (e.g. ore deposit formation), or are present as metamorphic fluids in most of the middle to upper grade metamorphic facies. They are also responsible for metasomatic processes: for example, those related to subducting slabs at converging plate margins. Economic and industrial interests have also turned to critical and supercritical fluid systems, since high P-T fluids have successfully been applied as high efficiency solvents, often used for contaminant removal. The objective of our research is to examine the critical behavior and phase equilibrium properties of complex, four-component (H$_{2}$O-NaCl-KCl-CaCl$_{2}$) aqueous solutions using synthetic fluid inclusions. Critical PVTX properties in some of the binary subsystems in the H$_{2}$O-NaCl-KCl-CaCl$_{2}$ system have already been studied by previous authors. Experimental data have been published on critical phase relations in the system H$_{2}$O-NaCl, in dilute H$_{2}$O-KCl solutions, and in H$_{2}$O-CaCl$_{2}$ solutions up to 3 molal. Until recently, no experimental work has been done on the critical properties of more than two component systems, even though these solutions approximate the complexity of natural fluids. In order to examine these properties we used the synthetic fluid inclusion technique introduced by Bodnar and Sterner (1987). Critical points of brines up to 3 molal salinity have been determined. Our results show that 2 molal H$_{2}$O-KCl solutions have a higher critical temperature than H$_{2}$O-NaCl and H$_{2}$O-CaCl$_{2}$ brines of the same molality, whereas the latter one has significantly higher critical pressures. Critical points of three component solutions fall on slightly curved lines in P-T space and fall between the critical points of the corresponding binary end members. The critical point of the quaternary system falls in a triangle defined by the critical points of the three binary end members.
DE: 8424 Hydrothermal systems (8135)
DE: 3630 Experimental mineralogy and petrology
DE: 0350 Pressure, density, and temperature
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting