Combined phase equilibrium and thermal modelling has been used to investigate the evolution of asteroid 4 Vesta. Orthopyroxene compositions of 200 natural diogenite meteorites are used as a basis for constructing a staged mantle melting model for Vesta, which is then used to develop a staged thermal evolution model. Our pMELTS models find that removal of 15–20% of a mean eucrite component from an initial Vestan mantle composition allows a second stage of melting that crystallises low-calcium orthopyroxenes that match the observed compositions of those in natural diogenites, whereas single stage melting produces orthopyroxenes that are too calcic. Using the compositions generated by the pMELTS modelling, THERMOCALC models were created for an initial Vestan mantle composition and an evolved composition generated by a melt extraction stage. These models suggest that melt production for second-stage diogenite generation required considerably hotter temperatures (>1340 °C) than for eucrites (<1240 °C). Staged and layered thermal evolution models developed using these composition and temperature constraints, based on the decay of ²⁶Al and ⁶⁰Fe, suggest that Vesta accreted 1.50 to 1.75 Myr after calcium-aluminium inclusion (CAI) formation. Earlier accretion results in conditions that are inconsistent with the petrology of the HED meteorites, whereas later accretion predicts temperatures that are insufficient to produce diogenites. We suggest that upward migration of ²⁶Al-rich melt initially created a convecting shallow magma ocean of <20 km depth that rapidly crystallised to form a ²⁶Al-rich eucritic crust that acted as a hot insulating lid. The second stage of crust formation began once the depleted mantle residue reached high enough temperatures to produce diogenite-forming magmas. These results further support the view that diogenites likely formed as crustal intrusions rather than as magma ocean cumulates.

组合相平衡和热建模已被用于研究小行星 4 灶神星的演化。200 颗天然双生陨石的斜方辉石成分被用作构建灶神星分阶段地幔熔化模型的基础，然后用于开发分阶段热演化模型。我们的 pMELTS 模型发现，从最初的 Vestan 地幔成分中去除 15-20% 的平均晶辉石成分，可以进行第二阶段熔融，结晶出与观察到的天然双闪石中的成分相匹配的低钙斜方辉石，而单阶段熔融产生太钙质的正辉石。使用 pMELTS 建模生成的成分，为初始 Vestan 地幔成分和由熔体提取阶段生成的演化成分创建了 THERMOCALC 模型。 °C) 比 eurite (<1240  °C)。基于²⁶ Al 和⁶⁰ Fe的衰变，使用这些成分和温度限制开发的分阶段和分层热演化模型表明，灶神星在钙铝夹杂物 (CAI) 形成后吸积了 1.50 到 1.75 Myr。较早的吸积导致与 HED 陨石的岩石学不一致的条件，而较晚的吸积预测温度不足以产生双生岩。我们认为²⁶富铝熔体的向上迁移最初形成了一个深度小于 20 公里的对流浅岩浆海洋，并迅速结晶形成了²⁶充当热绝缘盖的富含铝的易晶质外壳。一旦耗尽的地幔残余物达到足够高的温度以产生形成双闪石的岩浆，地壳形成的第二阶段就开始了。这些结果进一步支持了异生岩可能形成为地壳侵入体而不是岩浆海洋累积的观点。