论文标题

从单个软骨中Cr-Ti-O同位素推断出的太阳能积聚的早期演变

Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules

论文作者

Schneider, Jonas M., Burkhardt, Christoph, Marrocchi, Yves, Brennecka, Gregory A., Kleine, Thorsten

论文摘要

软骨中的同位素异常具有有关太阳能积聚磁盘中混合和传输过程动力学的重要线索。这些异常已被解释为表明软骨的整个磁盘转运或软骨前体的局部异质性。但是,所有以前的研究都依赖于单个元素(CR,Ti或O)的同位素数据,该数据不允许将源和前体特征区分开为软骨同位素异常的原因。在这里,我们获得了来自Enstatite,普通和碳质软管的单个软骨的第一个组合O,Ti和Cr同位素数据。我们发现来自非碳质(NC)软骨的软骨具有相对均匀的Δ17O,ε50TI和ε54CR,它们与宿主软骨的组成相似。相比之下,来自碳质软管(CC)的软骨具有更多可变成分。尽管分析的CC和NC软骨的组成可能重叠在多相位空间中的ε50TI,ε54CR或Δ17O中,但在NC软骨的组成场中均无CC软骨图,没有NC CHONDRULE的组成场中的CC软骨图,也不是CC CC CCCC Chondrites的领域。因此,我们的数据揭示了NC和CC软骨之间的基本同位素差异,这与跨盘跨盘跨NC和CC储层之间的盘范围跨盘的运输不一致。 Instead, the isotopic variations among CC chondrules reflect local precursor heterogeneities, which most likely result from mixing between NC-like dust and a chemically diverse dust component that was isotopically similar to CAIs and AOAs.The same mixing processes, but on a larger, disk-wide scale, were likely responsible for establishing the distinct isotopic compositions of the NC and CC reservoirs, which represent in inner and outer磁盘分别。

Isotopic anomalies in chondrules hold important clues about the dynamics of mixing and transport processes in the solar accretion disk. These anomalies have been interpreted to indicate either disk-wide transport of chondrules or local heterogeneities of chondrule precursors. However, all previous studies relied on isotopic data for a single element (either Cr, Ti, or O), which does not allow distinguishing between source and precursor signatures as the cause of the chondrules isotope anomalies. Here we obtained the first combined O, Ti, and Cr isotope data for individual chondrules from enstatite, ordinary, and carbonaceous chondrites. We find that chondrules from non-carbonaceous (NC) chondrites have relatively homogeneous Δ17O, ε50Ti, and ε54Cr, which are similar to the compositions of their host chondrites. By contrast, chondrules from carbonaceous chondrites (CC) have more variable compositions. Although the compositions of the analyzed CC and NC chondrules may overlap for either ε50Ti, ε54Cr, or Δ17O, in multi-isotope space none of the CC chondrules plot in the compositional field of NC chondrites, and no NC chondrule plots within the field of CC chondrites. As such, our data reveal a fundamental isotopic difference between NC and CC chondrules, which is inconsistent with a disk-wide transport of chondrules across and between the NC and CC reservoirs. Instead, the isotopic variations among CC chondrules reflect local precursor heterogeneities, which most likely result from mixing between NC-like dust and a chemically diverse dust component that was isotopically similar to CAIs and AOAs.The same mixing processes, but on a larger, disk-wide scale, were likely responsible for establishing the distinct isotopic compositions of the NC and CC reservoirs, which represent in inner and outer disk, respectively.

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