Experimental study of heterogeneous fluid equilibria in silicate-salt-water systems

Fluid inclusions in quartz have been synthesized from Na2SO4 and NaF solutions at 700–800°C and 1 and 2 kbar using the fracture healing method. Some experiments have been carried out in the presence of albite gel. Microthermometry of the synthesized inclusions showed that under experimental conditions, the fluid was heterogeneous and reactive in respect to quartz and albite. Soluble sodium silicates formed in the presence of (alumino)silicate matter, whereas malladrite appeared when fluid interacted with NaF. When the fluid was entrapped in inclusions cooled from 400 to 250°C, it became heterogeneous again. Appearance of the second liquid phase depended on the composition of the (alumino)silicate phase. It has been shown that three noncrystalline phases coexist at such a low temperature. Silicate matter affects heterogeneous fluid equilibria, even when the salts of the second type are contained in fluid in insignificant amounts. Fluid immiscibility appears to be more widespread than is commonly suggested and is the most important mechanism of matter redistribution, including ore substances.