Experimentally determined compositions of diopside-jadeite pyroxene in equilibrium with albite and quartz at 1200–1350°C and 15–34 kbar |
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| Authors: | Tibor Gasparik |
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| Institution: | Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794, USA |
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| Abstract: | Equilibrium compositions of diopside-jadeite pyroxene coexisting with albite and quartz were experimentally determined at 25 different P-T conditions, using an electron microprobe for analysis. The new data and the 600°C data of Holland (1983) provided the following mixing properties of the diopside (Di)-jadeite (Jd) solid solution (J, K): Gxs = XJdXDi12600 ? 9.45T + (12600 ? 7.6T)(XJd ? XDi) ? (21400 ? 16.2T)(XJd ? XDi)2]. The Di-Jd solution is close to ideal above 1000°C but immiscible below 565°C. The Di-Jd solvus is slightly asymmetric with the crest at composition Di42.4Jd57.6. Excess enthalpy is positive but smaller than indicated by the enthalpy of solution measurements of Woodet al. (1980). Disorder in the Di-Jd solution is significantly smaller than complete disorder implied by the ionic two-site model. |
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