Computer Science
Scientific paper
Jun 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006gecoa..70.3059p&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 70, Issue 12, p. 3059-3074.
Computer Science
2
Scientific paper
The thermal expansivities of 10 compositions from within the anorthite wollastonite gehlenite (An Wo Geh) compatibility triangle have been investigated using a combination of calorimetry and dilatometry on the glassy and liquid samples. The volumes at room temperature were derived from densities measured using the Archimedean buoyancy method. For each sample, density was measured at 298 K using glass that had a cooling-heating history of 10 10 K min-1. The thermal expansion coefficient of the glass from 298 K to the glass transition interval was measured by a dilatometer and the heat capacity was measured using a differential scanning calorimeter from 298 to 1135 K. The thermal expansion coefficient and the heat flow were determined at a heating rate of 10 K min-1 on glasses which were previously cooled at 10 K min-1. Supercooled liquid density, molar volume and molar thermal expansivities were indirectly determined by combining differential scanning calorimetric and dilatometric measurements assuming that the kinetics of enthalpy and shear relaxation are equivalent. The data obtained on supercooled liquids were compared to high-temperature predictions from the models of (Lange, R.A., Carmichael, I.S.E., 1987. Densities of Na2O K2O CaO MgO FeO Fe2O3 Al2O3 TiO2 SiO2 liquids: New measurements and derived partial molar properties. Geochim. Cosmochim. Acta51, 2931 2946; Courtial, P., Dingwell, D.B., 1995. Nonlinear composition dependence of molar volume of melts in the CaO Al2O3 SiO2 system. Geochim. Cosmochim. Acta59 (18), 3685 3695; Lange, R.A., 1997. A revised model for the density and thermal expansivity of K2O Na2O CaO MgO Al2O3 SiO2 liquids from 700 to 1900 K: extension to crustal magmatic temperatures. Contrib. Mineral. Petrol.130, 1 11). The best linear fit combines the supercooled liquid data presented in this study and the high temperature data calculated using the Courtial and Dingwell (1995) model. This dilatometric/calorimetric method of determining supercooled liquid molar thermal expansivity greatly increases the temperature range accessible for thermal expansion. It represents a substantial increase in precision and understanding of the thermodynamics of calcium aluminosilicate melts. This enhanced precision demonstrates clearly the temperature independence of the melt expansions in the An Wo Geh system. This contrasts strongly with observations for neighboring system such as anorthite diopside and raises the question of the compositional/structural origins of temperature dependence of thermal expansivity in multicomponent silicate melts.
Dingwell Donald B.
Potuzak Marcel
Solvang Mette
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