An internally consistent thermodynamic model for the subsolidus system CaO‐MgO‐Al2O3‐SiO2 (CMAS) was developed and refined using primarily data from phase equilibrium experiments. The solution properties of pyroxenes and garnet were approximated with an ionic model, with independent mixing on adjacent crystallographic sites. This approach simplified the calculation of phase relations by allowing sequential calculation of the site occupancies. Enthalpy, entropy, and volume differences, nominally at 970 K, were derived for all participating phases by matching as closely as possible the experimentally observed phase relations. Although thermochemical measurements were not used directly in the refinement, the results were continuously monitored and compared with the thermochemical data to achieve a close match. The new model can be used to calculate phase diagrams for the CMAS system and its subsystems in the whole pressure range of the upper mantle. Simple empirical corrections for the effects of Na, Fe, Cr, etc., could potentially be introduced to make the model applicable to the thermobarometry of chemically complex mantle materials. Application of the new model to garnet lherzolite xenoliths from northern Lesotho and garnet peridotites from Norway supports the proposals for higher temperatures of the continental lithosphere.

中文翻译：

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CaO-MgO-Al2O3-SiO2 系统的内相一致热力学模型主要来自相平衡数据

亚固相系统 CaO-MgO-Al2O3-SiO2 (CMAS) 的内部一致热力学模型被开发和完善，主要使用来自相平衡实验的数据。辉石和石榴石的溶液性质用离子模型近似，在相邻的结晶位点上独立混合。这种方法允许按顺序计算场地占用，从而简化了相位关系的计算。焓、熵和体积差异，名义上为 970 K，是通过尽可能匹配实验观察到的相位关系为所有参与相导出的。尽管热化学测量并未直接用于精炼，但会持续监测结果并与热化学数据进行比较，以实现密切匹配。新模型可用于计算CMAS系统及其子系统在上地幔整个压力范围内的相图。可能会引入对 Na、Fe、Cr 等影响的简单经验修正，使该模型适用于化学复杂地幔材料的热气压测量。将新模型应用于莱索托北部的石榴石锂辉石捕虏体和挪威的石榴石橄榄岩支持了大陆岩石圈温度升高的建议。