Feldspathic Meteorites MIL 090034 and 090070: Late Additions to the Lunar Crust
Feldspathic Meteorites MIL 090034 and 090070: Late Additions to the Lunar Crust
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长石陨石 MIL 090034 和 090070：月壳的后期添加
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
M. Ebihara
中科院分区：
文献类型：
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作者：
L. Nyquist;N. Shirai;A. Yamaguchi;C. Shih;Jisun Park;M. Ebihara
我们对米勒岭月球陨石MIL 090034、090036和090070的研究表明，它们是来自月球高地的一组不同的岩石，下文分别称为MIL 34、MIL 36和MIL 70。MIL 34和MIL 70是本次工作的重点，是结晶熔融角砾岩。斜长石的成分在An 96 -97附近都有明显的峰值。橄榄石的Mg值从58-65不等，有几个更高的值。MIL 36为风化角砾岩。MIL 34和MIL 70在月球高地陨石中具有最高的Al 2 O3丰度，这表明它们是月球陨石中斜长石模态丰度最大的陨石之一。除了Dho 081、Dho 489和Dho 733外，它们的Sc和Cr丰度比几乎所有的月球高地陨石都要低。MIL 34和MIL 70也有类似的宇宙射线暴露（CRE）年龄，约为1-2 Ma，表明它们是成对发射的。（MIL 36的CRE年龄较大，约大于70 Ma）。Park等人发现MIL 34和MIL 70的子样品之间的Ar-Ar年龄存在差异，但MIL 34钙长石的“暗”相的年龄优选为3500+/-110 Ma，MIL 70的“亮”相的年龄优选为3520+/-30 Ma。Bouvier等人报告了MIL 34的一个碎屑岩的Pb-Pb年龄为3894+/-39 Ma，熔融岩石的年龄相似。在这里，我们重新检查的Rb-Sr和Sm-Nd同位素数据，这表明定性的Ar-Ar和Pb-Pb数据的复杂性一致。特别是Sm-Nd数据表明，MIL 34和MIL 70在初始月球地球化学分异过程中形成的蓝宝石成分，REE模拟表明相对较晚的形成阶段。
Our studies of the Miller Range lunar meteorites MIL 090034, 090036, and 090070 show them to be a diverse suite of rocks from the lunar highlands hereafter referred to as MIL 34, MIL 36, and MIL 70, resp. MIL34 and MIL70, the focus of this work, are crystalline melt breccias. Plagioclase compositions in both peak sharply around An96-97. Mg numbers of olivine vary from 58-65 with a few higher values. MIL36 is a regolith breccia. MIL 34 and MIL 70 have some of the highest Al2O3 abundances of lunar highland meteorites, indicating that they have among the largest modal abundances of plagioclase for lunar meteorites. They have lower Sc and Cr abundances than nearly all lunar highland meteorites except Dho 081, Dho 489 and Dho 733. MIL34 and MIL70 also have similar cosmic ray exposure (CRE) ages of approximately 1-2 Ma indicating they are launch paired. (MIL36 has a larger CRE age approximately greater than 70 Ma). Park et al. found a variation in Ar-Ar ages among subsamples of MIL 34 and MIL70, but preferred ages of 3500+/-110 Ma for the "Dark" phase of MIL 34 anorthite and 3520+/-30 Ma for the "Light" phase of MIL70. Bouvier et al. reported a Pb-Pb age of 3894+/-39 Ma for a feldspathic clast of MIL 34 and a similar age for a melt lithology. Here we reexamine the Rb-Sr and Sm-Nd isotopic data, which show complexities qualitatively consistent with those of the Ar-Ar and Pb-Pb data. The Sm-Nd data in particular suggest that the feldspathic compositions of MIL 34 and MIL 70 formed during initial lunar geochemical differentiation, and REE modeling suggests a relatively late-stage formation.