Calcium Isotope Evolution During Differentiation of Vesta and Calcium Isotopic Heterogeneities in the Inner Solar System
Calcium Isotope Evolution During Differentiation of Vesta and Calcium Isotopic Heterogeneities in the Inner Solar System
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DOI：
10.1029/2022gl102179
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发表时间：
2023-02
影响因子：
5.2
通讯作者：
Ke Zhu;Hejiu Hui;M. Klaver;Shiying Li;Lu Chen;W. Hsu
中科院分区：
文献类型：
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作者：
Ke Zhu;Hejiu Hui;M. Klaver;Shiying Li;Lu Chen;W. Hsu
我们采用 MC-ICP-MS 来测量灶神星相关陨石的质量依赖性 Ca 同位素组成。锂辉石和闪长岩表现出不同的 Ca 同位素组成，这是由同位素重的斜方辉石结晶引起的。 Ca 同位素数据支持两种岩性相互关联的模型，其中闪长岩主要由从真晶熔体结晶而成的斜方辉石组成。由于正常的锂辉石是灶神星上的主要 Ca 储层，因此它们的 δ44/40Ca 值（相对于 NIST 915a 的每密耳 44Ca/40Ca 比率）最能代表灶神星上块状硅酸盐的值 (0.83 ± 0.04‰)。该值与地球大体（0.94±0.05‰）和火星（1.04±0.07‰）不同，表明太阳系内天体之间存在显着的Ca同位素异质性。球粒和这些行星之间的 δ44/40Ca 差异并不支持卵石吸积模型作为行星生长的主要机制。
We employed MC‐ICP‐MS to measure the mass‐dependent Ca isotope compositions of Vesta‐related meteorites. Eucrites and diogenites show distinct Ca isotope compositions, which is caused by crystallization of isotopically heavy orthopyroxene. The Ca isotope data support a model where the two lithologies are linked, where the diogenites, mainly composed of orthopyroxene crystallized from an eucritic melt. As normal eucrites are the main Ca reservoir on Vesta, their δ44/40Ca values (per mil 44Ca/40Ca ratios relative to NIST 915a) best represents that of bulk silicate Vesta (0.83 ± 0.04‰). This value is different from those of bulk Earth (0.94 ± 0.05‰) and Mars (1.04 ± 0.07‰), suggesting that there exists notable Ca isotope heterogeneity between inner solar system bodies. The δ44/40Ca difference between chondrules and these planets does not support the pebble accretion model as the main mechanism for planetary growth.