No abstract

No abstract

Heterogeneous fluid equilibria in the second type H 2 O-Na 2 CO 3 system in the presence of SiO 2 or SiO 2 + NaAlSi 3 O 8 were studied experimentally. Phase diagrams of the second type systems are briefly described. Fluid inclusions in quartz were synthesized by healing of fractures in 1 M Na 2 CO 3 solution at 700°C and under 1, 2, and 3 kbar pressure. Some runs were carried out in the presence of albite gel. The microthermomemtric study of the synthesized inclusions showed that under experimental conditions the fluid was heterogeneous and did not remain inert with respect to quartz and albite. Some inclusions contained a glass like phase, and liquid released from this phase by heating. Having been heated, some inclusions revealed liquid immiscibility. Comparison of the water-silicate-sodium carbonate system with similar sys tems containing sodium sulfate and fluoride Kotel'nikov, 2008, 2010) shows that they have much in common. In all cases, the aqueous salt bearing fluid did not remain inert relative to the quartz under relatively low PT conditions. The inclusions entrapped in the upper heterogeneous region revealed immisci bility in the presence of vapor within a temperature range of 200 to 400°C. The solutions of various concen trations, including oversaturated solutions in the presence of solid phase, underwent recurrent heterogeniza tion. Near 400°C, vapor is either dissolved in one of immiscible liquids or absorbs this liquid. When heating progresses to higher temperature, inclusions commonly become unsealed.

Abstract. Structural parameters and thermodynamic properties of strontianite -witherite solid solutions have been studied by X-ray powder diffraction, heat flux Calvet calorimetry and cation-exchange equilibria technique. X-ray study of the synthetic samples have Cation-exchange reactions between carbonates and aqueous SrC12-BaC12 supercritical solutions (fluids) were carried out at 973 and 1073 K and 2 kbar. Calculated Margules model parameters of the excess free energy are: for orthorhombic carbonate solid solutions Wsr=WBa=ll.51+0.40kJ*mo1-1 (973 K) and Wsr= W~,= 12.09_+0.95 kJ,mo1-1 (1073 K); for trigonal carbonate solid solutions WSr = WBa = 13.55___ 0.40 kJ* mol-1 (1073 K).