The impact history and prolonged magmatism of the angrite parent body
The impact history and prolonged magmatism of the angrite parent body
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DOI：
10.1111/maps.14102
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发表时间：
2023-11
影响因子：
2.2
通讯作者：
B. G. Rider-Stokes;M. Anand;L. F. White;J. Darling;R. Tartèse;M. Whitehouse;I. Franchi;R. C. Greenwood;G. Degli-Alessandrini
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文献类型：
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作者：
B. G. Rider-Stokes;M. Anand;L. F. White;J. Darling;R. Tartèse;M. Whitehouse;I. Franchi;R. C. Greenwood;G. Degli-Alessandrini
作为我们太阳系中最古老的分化物质，角闪石陨石可以为行星演化的最早阶段提供独特的见解。然而，行星混合的时间，证明了在淬火的角闪石的氧同位素的变化，以及岩浆作用的程度上的角闪石母体（APB）仍然知之甚少。在这里，我们报告的微结构指导的原位地球化学和Pb-Pb同位素测量的红铁矿，旨在更好地了解岩浆过程的时间和性质，以及影响事件，对APB。淬冷的角闪石西北非洲（NWA）12320产生的Pb-Pb年龄为4571.2 ± 9.4 Ma，我们解释为对应于行星混合的时间。唯一已知的冲击淬灭角闪石，NWA 7203，也获得了4562.9 ± 9.3 Ma的古老Pb-Pb年龄，这与结构中间角闪石NWA 10463获得的4563.6 ± 7.9 Ma的Pb-Pb年龄相同。对NWA 8535纯安质钠长岩中磷酸盐的Pb-Pb分析表明，该岩石的年龄为4514 ± 30 Ma，这是有记录以来钠长岩中最年轻的Pb-Pb年龄。基于证据从缺乏冲击变形，橄榄石的主要和微量元素组成，并没有明显的污染，在NWA 8535的氧同位素组成，我们的研究结果是一致的，延长岩浆活动的APB。这一发现与APB的大尺寸一致。
As some of the oldest differentiated materials in our solar system, angrite meteorites can provide unique insights into the earliest stages of planetary evolution. However, the timing of planetary mixing, as evidenced by oxygen isotope variations in the quenched angrites, and the extent of magmatism on the angrite parent body (APB) remain poorly understood. Here, we report on microstructurally guided in situ geochemical and Pb–Pb isotopic measurements on angrites aimed at better understanding of the timing and nature of magmatic processes, as well as impact events, on the APB. The quenched angrite Northwest Africa (NWA) 12320 yielded a Pb–Pb date of 4571.2 ± 9.4 Ma, which we interpret as corresponding to the timing of planetary mixing. The only known shocked quenched angrite, NWA 7203, also yielded an ancient Pb–Pb date of 4562.9 ± 9.3 Ma, which is identical to the Pb–Pb date of 4563.6 ± 7.9 Ma obtained for the texturally intermediate angrite NWA 10463. Pb–Pb analyses in phosphates in the dunitic angrite NWA 8535 yielded a much younger date of 4514 ± 30 Ma, representing the youngest Pb–Pb date ever recorded for an angrite. Based on the evidence from the lack of shock deformation, olivine major and trace element compositions, and no apparent contamination in the oxygen isotope composition of NWA 8535, our findings are consistent with prolonged magmatism on the APB. This finding is consistent with a large size for the APB.