Title: Viscosity and mixing in molten (Ca, Mg) pyroxenes and garnets
Abstract: A creep apparatus has been built to measure, with inaccuracies of less than 0.04 log poise, viscosities of supercooled silicate melts in the range 109–1014 poises. Measurements on seven pyroxene and five garnet supercooled liquid compositions along the joins MgSiO3-CaSiO3 and Mg3Al2Si3O12Ca3 Al2Si3O12 made between 1000 and 1150 K show deep minima in the viscosity-composition relationship for both joins. These minima reduce when the temperature increases and disappear eventually. Within the framework of the configurational entropy theory of relaxation processes, these observations can be accounted for quantitatively in terms of the contribution of ideal (Ca, Mg) mixing to the total configurational entropy of the melts. The configurational entropies determined from the viscosity measurements agree with the values determined by calorimetry for liquid CaSiO3, CaMgSi2O6, MgSiO3, and Mg3Al2Si3O12. The heat capacities of Ca3Al2Si3O12 glass and liquid have also been obtained from dropcalorimetry measurements.
Publication Year: 1991
Publication Date: 1991-04-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 209
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