Abstract
The activity of the jadeite (NaAlSi2O6) component in synthetic pyroxenes on the binary join NaAlSi2O6-CaMgSi2O6 has been measured at 600° C by equilibration of pyroxene with quartz and high albite in hydrothermal experiments. The results are in good agreement with recent calorimetry (Wood et al. 1980) for pyroxenes not close to the Jd50Di50 composition for which a considerable degree of short range ordering on the omphacite scheme is indicated by the activity measurements. For compositions close to Jd50Di50, the activity of the jadeite component is approximately equal to its mole fraction.
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Holland, T.J.B. The experimental determination of activities in disordered and short-range ordered jadeitic pyroxenes. Contr. Mineral. and Petrol. 82, 214–220 (1983). https://doi.org/10.1007/BF01166616
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DOI: https://doi.org/10.1007/BF01166616