The cosmochemistry of meteorites provides unique clues on asteroids accretion, differentiation, collisional break-up and reassembly, processes of critical importance for understanding planet formation in the early solar system. Mesosiderites are a complex group of achondrites whose nearly 50:50 metal-silicate composition is interpreted in the literature as resulting from the mixing of core and crustal materials derived from differentiated asteroid(s). Because of their complex nature and contrasting geochemical, isotopic, and spectroscopic data, the formation mechanism of mesosiderites is still poorly understood and is open to a large variety of planetary differentiation scenarios and collisional histories. In this study, based on new petrographic and geochemical data of 16 mesosiderites, we investigate in detail the proposal that mesosiderites are related to the howardite-eucrite-diogenite (HED) meteorite group, whose parent body is widely considered to be asteroid 4 Vesta (∼500 km diameter), the target of the recent NASA’s Dawn mission. We present the first high precision oxygen isotope analyses on the matrix of a set of mesosiderite samples, coupled with new chemical and petrographic analyses of mesosiderites Um Hadid, Estherville, and Mount Padbury. Concordant Δ¹⁷O values between mesosiderites (–0.241 ± 0.015 (2σ)) and howardite-eucrite-diogenites (−0.241 ± 0.017‰ (2σ)) indicate that they derived from the same oxygen isotope reservoir, but petrological evidence, in particular the distinctly lower Fe/Mn ratios and the larger lithological diversity in mesosiderites, indicates that they formed within different parent bodies. This suggests that mesosiderites and howardite-eucrite-diogenites originated in distinct parent bodies that accreted in the 4 Vesta source region but experienced different geologic evolution in terms of crustal differentiation and impact history, which were more complex and catastrophic in the mesosiderite parent body.

陨石的宇宙化学为小行星的吸积、分化、碰撞解体和重组提供了独特的线索，这些过程对于理解早期太阳系中的行星形成至关重要。中铁陨石是一组复杂的无球粒陨石，其近 50:50 的金属-硅酸盐组成在文献中被解释为源自不同小行星的核心和地壳物质的混合。由于其复杂的性质和对比的地球化学、同位素和光谱数据，中铁陨石的形成机制仍然知之甚少，并且对各种行星分化情景和碰撞历史持开放态度。在这项研究中，基于 16 颗中铁矿的新岩石学和地球化学数据，我们详细研究了中铁陨石与霍华德陨石-eucrite-diogenite (HED) 陨石群有关的提议，该陨石群的母体被广泛认为是小行星 4 Vesta（直径约 500 公里），这是最近美国宇航局黎明任务的目标。我们对一组中铁矿样品的基质进行了首次高精度氧同位素分析，并对中铁矿 Um Hadid、Estherville 和 Mount Padbury 进行了新的化学和岩相分析。一致的Δ 再加上对中铁矿 Um Hadid、Estherville 和 Mount Padbury 的新化学和岩相分析。一致的Δ 再加上对中铁矿 Um Hadid、Estherville 和 Mount Padbury 的新化学和岩相分析。一致的Δ¹⁷中铁矿 (–0.241 ± 0.015 (2σ)) 和霍华德石-锂辉石-二成岩 (-0.241 ± 0.017‰ (2σ)) 之间的 O 值表明它们来自相同的氧同位素储层，但岩石学证据，特别是明显较低的铁锰比和中铁陨石中较大的岩性多样性表明它们形成于不同的母体中。这表明中铁陨石和霍华德辉石-榴辉石-地金岩起源于灶神星4源区的不同母体，但在地壳分异和影响历史方面经历了不同的地质演化，在中铁陨石母体中更为复杂和灾难性。