Elemental and isotopic abundances of lithium in chondrule constituents in the Allende meteorite
Elemental and isotopic abundances of lithium in chondrule constituents in the Allende meteorite
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DOI：
10.1016/j.gca.2008.10.039
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发表时间：
2009-02
影响因子：
5
通讯作者：
S. Maruyama;Masaki Watanabe;T. Kunihiro;Eizo Nakamura
中科院分区：
文献类型：
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作者：
S. Maruyama;Masaki Watanabe;T. Kunihiro;Eizo Nakamura
利用二次离子质谱法测定了阿连德CV 3陨石球粒成分中锂的元素和同位素丰度。橄榄石和中静态相的Li含量分别为<1μgg-1和0.1-0.6μgg-1。低钙辉石和以富钠相为主的中稳相富集Li（分别为0.1 -8μgg-1和0.4-3.5μgg-1），球粒间基质普遍富集Li（平均为0.20 μgg-1）。橄榄石的Li同位素丰度范围为δ 7 Li ~（-32）~ δ 7 Li ~（-21）。橄榄石中Li元素和同位素丰度的空间分布在单个球粒内没有系统的模式。这表明，在阿连德陨石母体上的水蚀变或热变质过程中，Li在橄榄石中的分布没有受到干扰。虽然中稳态是球粒熔体的最后结晶阶段，预计将富含锂，但在阿连德陨石中，它通常缺乏锂。我们认为，在CV小行星上的水蚀变过程中，Li在中稳态中被水流体浸出。富锂的富钠的中稳态可能是后来产生的富钠流体的渗透。这似乎是可能的，水流体隔离的碱性元素从Allende球粒陨石地区的CV母小行星，虽然大量的锂被保存在铁橄榄石的球粒间矩阵。
Elemental and isotopic abundances of lithium in chondrule constituents in the Allende CV3 meteorite were determined using secondary ion mass spectrometry. Olivines and mesostasis dominated by a feldspathic phase are depleted in Li (<1μgg-1and 0.1–0.6μgg-1, respectively). In contrast, low-Ca pyroxenes and mesostasis dominated by a Na-rich phase are enriched in Li (∼1–8μgg-1and 0.4–3.5μgg-1, respectively) and the interchondrule matrix is generally enriched in Li (∼2.0μgg-1on average). The Li isotopic abundance of olivine ranges from δ7Li∼-32 to 21. The spatial distributions of elemental and isotopic abundances of Li in olivines within individual chondrules exhibit no systematic pattern. This suggests that the distribution of Li in olivine was not disturbed during aqueous alteration or thermal metamorphism on the Allende meteorite parent body. Although mesostasis is the last crystallizing phase from a chondrule melt and is expected to be enriched in Li, in the Allende meteorite it is generally depleted in Li. We suggest that during aqueous alteration on the CV asteroid, Li in mesostasis was leached out by aqueous fluids. The Li-enriched Na-rich mesostasis was probably produced later by infiltration of Na-rich fluids. It seems likely that aqueous fluids sequestered alkali elements from the Allende–chondrite region in the CV parent asteroid, although significant amounts of Li are preserved in ferrous olivine in the interchondrule matrix.