Thermochemical study of glasses in the system CaMgSi2O6-CaAl2SiO6

Alexandra Navrotsky, Hans D. Zimmermann, Richard Hervig

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22 Scopus citations


High temperature solution calorimetry of glasses in the system CaMgSi2O6 (Di)-CaAl2SiO6 (CaTs) show them to have negative enthalpies of mixing with a regular enthalpy parameter, WH, of -11.4 ± 0.7 kcal. Negative heats of mixing between alumina-rich and alumina-poor glasses seem to be a general phenomenon in aluminosilicates and are not confined only to glassy systems containing anorthite as a component. The thermodynamic behavior of glasses in the system SiO2-Ca0.5;AlO2-CaMgO2 appears to vary in a smooth fashion, with small positive heats of mixing near SiO2 and substantial negative heats of mixing for other compositions. The exothermic behavior with increasing A1 (Al + Si) may be related to local charge balance of M2+ and Al3+. The negative heats of mixing in MgCaSi2O6-CaAl2SiO6, MgCaSi2O6-CaAl2Si2O8 and NaAlSi3O8-CaAl2Si2O8 glasses are in contrast to the positive heats of mixing found in MgCaSi2O6-CaAl2SiO6 (pyroxene) and NaAlSi3O8-CaAl2Si2O8 (high plagioclase) crystalline solid solutions.

Original languageEnglish (US)
Pages (from-to)1535-1538
Number of pages4
JournalGeochimica et Cosmochimica Acta
Issue number8
StatePublished - Aug 1983

ASJC Scopus subject areas

  • Geochemistry and Petrology


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