AI 中文总结
结合改进的热演化与发电机模型，重新评估两类陨石母体性质，发现其形成与撞击相关，为分异星子演化提供了新见解。
AI 中文摘要
含有金属和硅酸盐的陨石表明，一些星子发生了部分分异，且部分星子在分异后发生了核与幔的混合过程。这类陨石群中的时间分辨古地磁记录可为这类天体的分异与混合历史提供线索。此前研究对IIE型铁陨石和主群橄榄陨铁这两类陨石的古地磁剩余磁性进行了测量，并结合热演化与发电机产生模型反演了母体天体的性质。但这些研究假设这些陨石仅记录了由核固化产生的磁场，该假设近期被证实不成立。我们采用一种改进的星子热演化与发电机产生模型，该模型同时考虑了发电机产生的热驱动与成分驱动，以此重新评估IIE型铁陨石和主群橄榄陨铁的母体天体性质，并限定这些陨石的形成机制。研究发现，所有剩余磁性均不要求核固化，但后期形成的剩余磁性更可能记录由核固化驱动的发电机。主群橄榄陨铁和IIE型铁陨石的母体半径约为400km，核半径分数分别约为0.5和0.7。撞击塑造了这两个母体天体：主群橄榄陨铁的形成位置距离核幔边界过远，无法由铁岩浆作用形成，而是由撞击形成；IIE型铁陨石的核半径分数表明其母体经历了幔剥离碰撞。总体而言，将陨石古地磁学与热演化及发电机产生模型结合，可为分异星子的长期演化、内部结构以及这类天体上的金属-硅酸盐混合过程提供见解。
英文摘要
Meteorites containing both metal and silicates indicate that some planetesimals were partially differentiated and/or processes mixed planetesimal cores and mantles post-differentiation. Time-resolved paleomagnetic records in these meteorite groups can shed light on the differentiation and mixing histories of such bodies. Previous studies measured paleomagnetic remanences in two such meteorite groups, the IIE irons and the Main Group pallasites, and used thermal evolution and dynamo generation modelling to recover parent body properties. However, these studies assumed that these meteorites only recorded magnetic fields generated by core solidification; an assumption recently shown to be invalid. We use a refined planetesimal thermal evolution and dynamo generation model that considers thermal and compositional drivers of dynamo generation simultaneously to re-evaluate the parent body properties of the IIE irons and Main Group pallasites and constrain the formation mechanisms of these meteorites. We find that none of the remanences require core solidification, but later formed remanences are more likely to record dynamos driven by core solidification. The Main Group pallasites and IIE iron parent bodies likely had radii of $\sim$400km with core radius fractions of $\sim$0.5 and $\sim$0.7, respectively. Impacts shaped both parent bodies: the Main Group pallasites formed too far from the core-mantle-boundary to result from ferromagmatism and instead formed by impacts, and the IIE iron's core radius fraction suggests the parent body experienced mantle-stripping collisions. Overall, combining meteorite paleomagnetism with thermal evolution and dynamo generation models provides insights into the long-term evolution of differentiated planetesimals, their interior structures, and metal-silicate mixing on these bodies.
Comments29 pages, 7 figures. Supplementary materials are a pdf in the TeX source file. Submitted to Earth and Planetary Science Letters
