Heat capacity and thermodynamic properties for two samples of prismatine
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Open-File Report↗
Geology topics
Lawrence M. Anovitz
Publications and source records attributed to Lawrence M. Anovitz.
Thermodynamics of boron minerals: Summary of structural, volumetric and thermochemical data
[No abstract available]
Reviews in Mineralogy↗
Heat capacity measurements for cryolite (Na3AlF6) and reactions in the system NaFeAlSiOF
The heat capacity of cryolite (Na 3 AlF 6 ) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S 0 298 = 238.5 J / mol K "> S 0 298 = 238.5J/mol K S 0 T − S 0 298 = 145.114 ln T+ 193.009∗10 −3 T− 10.366∗ 10 5 T 2 − 872.89 J / mol K (273−836.5 K ) "> S 0 T −S 0 298 = 145.114lnT+ 193.009∗10 −3 T−10.366∗ 10 5 T 2 − 872.89J/mol K(273−836.5K) Δ S Trans = 9.9 J / mol K "> ΔS Trans = 9.9J/mol K S 0 T − S 0 298 =198.414 ln T+73.203∗ 10 −3 T−63.814∗ 10 5 T 2 −1113.11 J / mol K (836.5−1153 K ) "> S 0 T −S 0 298 =198.414 ln T+73.203∗ 10 −3 T−63.814∗10 5 T 2 −1113.11J/mol K(836.5−1153K) with the transition temperature between α- and β-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system Na Fe Al Si O F. The resultant phase diagrams allow constraints to be placed on the f O 2 , f F 2 , a SiO 2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log f O 2 is approximately −19.2, log f F 2 is −31.9 to −33.2, and a SiO 2 is −1.06 at assumed P T "> PT conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland.
Geochimica et Cosmochimica Acta↗
The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O
Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO 3 ) from 5 to 1000 K. These measurements yield S 298 0 = 108.9 J /( mol · K ). Calculations from published experimental data on the reduction of ilmenite yield Δ 298 0 ( I 1) = −1153.9 kJ /( mol · K ). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of ƒO 2 ">ƒ ƒO2 are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookite ss and hematite-ilmenite ss . Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling.
Geochimica et Cosmochimica Acta↗