Partitioning of chlorine between muscovite and HCl-buffered solutions from 400 to 600°C at 2 kbar
Volfinger, Marcel; Pascal, Marie-Lola
European Journal of Mineralogy Volume 1 Number 6 (1989), p. 791 - 800
published: Dec 21, 1989
manuscript accepted: Aug 22, 1989
manuscript received: Mar 24, 1989
ArtNo. ESP147050106005, Price: 29.00 €
Abstract The Cl partitioning between muscovite and a chloride aqueous solution has been measured experimentally at 2 kbar from 400 to 600 °C. The OH-Cl exchange between muscovite and fluid was performed with a muscovitesanidine- quartz assemblage used as a HCl° buffer. The Cl content of muscovite, less than 400 ppm, was measured by counting a radioactive 36C1 tracer. For a given solution chlorinity, the Cl content of the mica increases with HC1 activity. The results show a very large variation of the partition coefficient D (ppm Cl mus/molality HC1 solution) with the temperature: it is 100 times higher at 400 °C than at 600 °C. D is independent of the chlorinity in the whole investigated range: 0.5 to 9 m. The Cl content of micas can thus be used as an acidity probe for hydrothermal solutions. When expressed according to the bulk chlorinity of the solution (ppm Cl mus/molality KCl+ HCl), the partitioning is independent of temperature in the system muscovite-sanidine-quartz-KCl-HCl-H2O. A similar behaviour is predicted for the system muscovite-perthite-plagioclase-quartz-fluid.