Viscosity-temperature relationships at 1 atm in the system diopside-anorthite

Abstract

Laboratory measurements of the viscosities of nine compositions on the diopside-anorthite join were made with a concentric-cylinder viscometer at temperatures between approximately 1200 and 1600 degrees C in air. Viscosities were measured both above the liquidus and in the supercooled liquid region. Viscosities were independent of shear rate, indicating Newtonian viscous behavior for the melts. Viscosities decreased with increasing temperature and, at constant temperature, they decreased with increasing amounts of diopside component in the mixtures. The temperature dependence of the viscosity above the liquidus was fitted to an Arrhenius relationship from which activation energies for viscous flow, ranging from 61 kcal/mole for a melt of anorthite composition to 38 kcal/mole for a melt of diopside composition, were derived. Viscosities over the entire range of melt and supercooled liquid temperatures were fitted by the method of least squares to the Fulcher equation. The fit was better than 0.02 in log viscosity.--Modified journal abstract.