Heterogeneous accretion of Earth inferred from Mo-Ru isotope systematics
Heterogeneous accretion of Earth inferred from Mo-Ru isotope systematics
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DOI：
10.1016/j.epsl.2020.116065
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发表时间：
2020-03-15
影响因子：
5.3
通讯作者：
Kleine, Thorsten
中科院分区：
文献类型：
--
作者：
Hopp, Timo;Budde, Gerrit;Kleine, Thorsten
陨石和块状硅酸盐地球（BSE）的Mo和Ru同位素组成为地球建筑材料的来源提供了重要线索。先前的研究认为，非碳质（NC）和碳质（CC）陨石群共同定义了钼-钌的“宇宙”相关性，而BSE图对这种相关性的延伸。这些观测结果被认为是地球最后10-15%的吸积物质来自于一个均匀的内部盘储层，其同位素组成类似顽火辉石。在这里，使用新的钼和钌同位素数据以前未经调查的陨石群，我们表明，钼-钌相关性只存在于NC陨石，和BSE和CC陨石脱落这种钼-钌相关性。这些观测表明，地球吸积的最后阶段是异质的，由NC和CC材料的混合物组成。钼钌同位素系统是最好的占无论是NC遗产的后期单板结合CC遗产的月球形成的巨大的冲击，或由混合NC-CC组合物的两个组件。CC机构参与地球的后期增生组合与核幔分化的化学模型是一致的，它主张增加更多的氧化和挥发性丰富的物质对地球的形成结束。因此，这项研究解决了均匀吸积模型的基础上的陨石的MoRu系统学和地球的异质吸积的化学证据的先前解释之间的不一致。(C)2020作者（S）由爱思唯尔公司出版
The Mo and Ru isotopic compositions of meteorites and the bulk silicate Earth (BSE) hold important clues about the provenance of Earth's building material. Prior studies have argued that non-carbonaceous (NC) and carbonaceous (CC) meteorite groups together define a Mo-Ru 'cosmic' correlation, and that the BSE plots on the extension of this correlation. These observations were taken as evidence that the final 10-15% of Earth's accreted material derived from a homogeneous inner disk reservoir with an enstatite chondrite-like isotopic composition. Here, using new Mo and Ru isotopic data for previously uninvestigated meteorite groups, we show that the Mo-Ru correlation only exists for NC meteorites, and that both the BSE and CC meteorites fall off this Mo-Ru correlation. These observations indicate that the final stages of Earth's accretion were heterogeneous and consisted of a mixture of NC and CC materials. The Mo-Ru isotope systematics are best accounted for by either an NC heritage of the late veneer combined with a CC heritage of the Moon-forming giant impactor, or by mixed NC-CC compositions for both components. The involvement of CC bodies in the late-stage accretionary assemblage of Earth is consistent with chemical models for core-mantle differentiation, which argue for the addition of more oxidized and volatile-rich material toward the end of Earth's formation. As such, this study resolves the inconsistencies between homogeneous accretion models based on prior interpretations of the MoRu systematics of meteorites and the chemical evidence for heterogeneous accretion of Earth. (C) 2020 The Author(s). Published by Elsevier B.V.