Solubility of Simple Pelitic and Granitic Mineral Assemblages in Chloride Rich Aqueous Solutions at 2 kbar, and 400°–650°C

Abstract

Alkali chlorides complexes are the principal solutes of most hydrothermal fluids. An understanding of the solubility of alkali metal silicates will thus provide insight into the origins of hydrothermal fluids, and physical and chemical condi-tions of fluid-rock interaction during alkali metasomatism and ore formation. Several studies have shown the mobility of alkali metals during regional metamorphic processes (e.g. Dipple et al, 1990; Ague, 1991). Similarly, potassic alteration in porphyry copper deposits is abundant (e.g. Hemley, 1959). In order to obtain a better under-standing of fluid-rock interaction during such metamophic events, we have mea-sured the solubility of the assemblages albite(ab)+K-feldspar(kfs)+andalusite (and) +quartz (qtz) at 600 ~ and 650~ and ab+muscovite(mu)+and+qtz at 550~ at 2kbar over a total chloride range of 0.01 to 4 m C1 t~ These assemblages were selected to approximate high grade pelitic assemb-lages in contact aureoles. Additional studies with the simplified granitic mineral assemblage ab+mu+kfs+qtz were obtained over a temperature range of 400 ~ to 600~ at 2kbar total pressure and 1 m total chloride. The rapid-quench technique was used. Na, K, A1, Si, and pH were measured on quench. Starting