To address the bulk compositions of CAIs from CH-CB chondrites we have used a new thermodynamic method to model the evaporation of CAI-like melts. The model calculations agree closely with the results of evaporation experiments on individual bulk compositions, and thus could provide a general means of predicting the evaporation trajectory of any CAI bulk composition melt. The model calculations and evaporation experiments show that the initial stages of CAI melt evaporation are controlled by the relative evaporation rates of MgO and SiO₂, whereas the late stages are dominated by the initial CaO/Al₂O₃ ratio of the melt. Application of the model to the puzzling bulk compositions of very refractory CAIs from CH-CB chondrites, many of which are grossite-, hibonite-, and spinel-rich, shows that such compositions can be derived via evaporation of precursors unusually enriched in Al₂O₃ with CaO/Al₂O₃ ratios (weight %) < 0.3. This rules out most silicate-rich CAI varieties. Only spinel- and spinel-hibonite-rich fine-grained inclusions with group II REE patterns (common in CV3 chondrites), which may have been present in the region where CH CAIs formed, could be precursors for the grossite- and hibonite-rich igneous CAIs.

为了解决CH-CB球粒陨石中CAI的大部分成分，我们使用了一种新的热力学方法来模拟CAI类熔体的蒸发。模型计算与单个散​​装物料的蒸发实验结果非常吻合，因此可以为预测任何CAI散装物料熔体的蒸发轨迹提供一般手段。模型计算和蒸发实验表明，CAI熔体蒸发的初始阶段受MgO和SiO ₂的相对蒸发速率控制，而后期则受初始CaO / Al ₂ O _{3的控制。}熔体的比例。将模型应用于CH-CB球粒陨石中非常难熔的CAI令人费解的本体组成的过程中，其中很多都是富含岗石，菱铁矿和尖晶石的，这些组成可以通过蒸发异常地富含Al ₂的前驱体获得。ø ₃与CaO的/ Al的_2分ö ₃比（重量％）<0.3。这排除了大多数富含硅酸盐的CAI品种。只有富杂尖晶石和尖晶石-日bon石的细颗粒夹杂物（在CV3球粒陨石中常见），可能存在于形成CH CAI的区域，具有II类REE模式，才可能是富含杂石和火成石的火成岩的前兆。 CAI。