Early Solar System Dynamics Inferred from Molybdenum Isotope Anomalies in Meteorites
Early Solar System Dynamics Inferred from Molybdenum Isotope Anomalies in Meteorites
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发表时间：
2018-03
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通讯作者：
G. Budde;C. Burkhardt;T. Kleine
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作者：
G. Budde;C. Burkhardt;T. Kleine
简介：核合成同位素异常来自于同位素异常的太阳前物质的不均匀分布，是通过建立行星体之间的遗传关系来研究早期太阳系动力学的有力工具。例如，在以前的工作[1]的基础上，Budde等人[2]证明了大块陨石中的核合成Mo同位素异常揭示了陨石遗传遗产的基本二分法，区分了碳质（CC）和非碳质（NC）材料。CC和NC储层之间的同位素差异不能反映盘组成的时间变化，因为两组都含有方解石和铁陨石，它们形成于CAI形成后<1 ~4 Ma之间[2- 4]。相反，这些观察表明CC和NC陨石来自两个空间上不同的水库，共存并保持分离了数百万年，最有可能是由于木星在它们之间形成[2，4]。然而，这种解释关键取决于是否有陨石的成分是中间的NC和CC水库。因此，我们获得了以前没有调查过的陨石群的钼同位素数据，以评估钼同位素二分法是否适用于所有陨石。这些数据不仅对测试NC和CC陨石之间的基本二分法很重要，而且还为地球的吸积历史提供了重要的新见解。样品和方法：到目前为止，我们已经获得了CK，CH，CBb和Rumuruti（R）辉长岩以及mesosiderites，accountcoites，bracchinites，和许多reulilites的钼同位素数据。所有样品均仔细清洁，并在Savillex烧杯中使用HF-HNO 3-HClO 4和反王水消化。按照我们建立的程序[2，3]，通过离子交换色谱法从样品基质中分离钼，并在Münster使用Neptune Plus MC-ICP-MS测量Mo同位素组成。将同位素数据内部标准化为Mo/Mo并报告为ε-单位偏差（即，0.01%）。Mo同位素分析的精确度和准确度通过重复测量BHVO-2岩石标准来评估，BHVO-2岩石标准与每组样品一起处理，并且其定义了外部再现性（2 s.d.）Mo同位素比值约为0.1-0.3ε（每次分析消耗约80 ng Mo）。-0.5 0 0.5 1 1.5 2
Introduction: Nucleosynthetic isotope anomalies arise from the heterogeneous distribution of isotopically anomalous presolar matter, and are powerful tools for investigating early solar system dynamics by establishing genetic relationships among planetary bodies. For instance, building on previous work [1], Budde et al. [2] demonstrated that nucleosynthetic Mo isotope anomalies in bulk meteorites reveal a fundamental dichotomy in the genetic heritage of meteorites, distinguishing between carbonaceous (CC) and noncarbonaceous (NC) materials. The isotopic difference between the CC and NC reservoirs cannot reflect a temporal change in the disk composition because both groups contain chondrites and iron meteorites, which formed between <1 and ~4 Ma after CAI formation [2– 4]. Instead, these observations indicate that CC and NC meteorites derive from two spatially distinct reservoirs that coexisted and remained separated for several million years, most likely as a result of the formation of Jupiter in between them [2,4]. However, this interpretation critically depends on whether or not there are meteorites with compositions that are intermediate between those of the NC and CC reservoirs. Therefore, we obtained Mo isotope data for meteorite groups that have not been investigated before to evaluate whether the Mo isotope dichotomy holds for all meteorites. These data are not only important for testing the fundamental dichotomy between NC and CC meteorites, but they also provide critical new insights into the accretion history of the Earth. Samples and methods: To date, we have obtained Mo isotope data for CK, CH, CBb, and Rumuruti (R) chondrites as well as for mesosiderites, acapulcoites, brachinites, and numerous ureilites. All samples were carefully cleaned and digested in Savillex beakers using HF-HNO3-HClO4 and inverse aqua regia. Molybdenum was separated from the sample matrix by ion exchange chromatography following our established procedures [2,3], and Mo isotope compositions were measured using the Neptune Plus MC-ICP-MS at Münster. The isotope data are internally normalized to Mo/Mo and reported as ε-unit deviations (i.e., 0.01%) relative to the bracketing solution standard. The precision and accuracy of the Mo isotope analyses were assessed by repeated measurements of the BHVO-2 rock standard, which was processed together with each set of samples and which defines an external reproducibility (2 s.d.) for the Mo isotope ratios of about 0.1–0.3ε (for ~80 ng Mo consumed per analysis). -0.5 0 0.5 1 1.5 2