1991 Volume 41 Issue 230 Pages 339-349
Stability relations of minerals in the system CaSiO3-MnSiO3-H2O have been determined experimentally by means of ion exchange in the temperature range from 400 to 800°C under lkbar. Aqueous chloride solution was used as a transport and exchange medium for cations Ca 2+ and Mn 2+. Stable minerals under the experimental conditions are wollastonite, bustamite, rhodonite, pyroxmangite, xonotlite and johannsenite.
Rhodonite is a high temperature polymorph of pyroxmangite and the transition temperature depends on the chemical composition. Pure pyroxmangite inverts to rhodonite at 725°C. Three phases, rhodonite, pyroxmangite and bustamite can coexist with each other at 525°C. Bustamite shows a wide stability field concerning temperature and composition. Johannsenite becomes stable below 450°C. The transition temperature between wollastonite and xonotlite was obtained to be 475°C for the end member composition.
The experimental results revealed that manganese ion is preferentially partitioned into the minerals, whereas calcium ion into the aqueous chloride solution. This tendency is enhanced with decreasing temperature.
