New experimental data on the stability of the pollucite-analcime series: application to natural assemblages
European Journal of Mineralogy Volume 7 Number 2 (1995), p. 319 - 324
published: Mar 29, 1995
ArtNo. ESP147050702007, Price: 29.00 €
Abstract Ion-exchange hydrothermal experiments have been carried out in the stoichiometric (Cs,Na)[AlSi2O6]·nH2O system pollucite (Poll)-analcime (Anl) in the absence of an excess of quartz, using 1M chloride solutions. At 450 °C, 1.5kbar, the solid solution is continuous from Poll100 to Anl100. At 600 °C, 1.5 kbar, the solid solution is continuous from Poll100 to PoII38 where a mixture of PoII38 + albite + nepheline (or sodalite) replaces the homogeneous cesian analcime phase. Under these experimental conditions, no solvus appears as proposed by Teertstra et ah (1992) to explain, in rare-element pegmatites, the existence of textures of (Na,Si)-rich pollucite intergrown with (Cs,Al)-rich pollucite.