Mineral/melt partition coefficients have been widely used to provide insights into magmatic processes. Olivine is one of the most abundant and important minerals in the lunar mantle and mare basalts. Yet, no systematic olivine/melt partitioning data are available for lunar conditions. We report trace element partition data between host mineral olivine and its melt inclusions in lunar basalts. Equilibrium is evaluated using the Fe-Mg exchange coefficient, leading to the choice of melt inclusion-host olivine pairs in lunar basalts 12040, 12009, 15016, 15647, and 74235. Partition coefficients of 21 elements (Li, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were measured. Except for Li, V, and Cr, these elements show no significant difference in olivine-melt partitioning compared to the data for terrestrial samples. The partition coefficient of Li between olivine and melt in some lunar basalts with low Mg# (Mg# < 0.75 in olivine, or < ~0.5 in melt) is higher than published data for terrestrial samples, which is attributed to the dependence of DLi on Mg# and the lack of literature DLi data with low Mg#. The partition coefficient of V in lunar basalts is measured to be 0.17 to 0.74, significantly higher than that in terrestrial basalts (0.003 to 0.21), which can be explained by the lower oxygen fugacity in lunar basalts. The significantly higher DV can explain why V is less enriched in evolved lunar basalts than terrestrial basalts. The partition coefficient of Cr between olivine and basalt melt in the Moon is 0.11 to 0.62, which is lower than those in terrestrial settings by a factor of ~2. This is surprising because previous authors showed that Cr partition coefficient is independent of fO2. A quasi-thermodynamically based model is developed to correlate Cr partition coefficient to olivine and melt composition and fO2. The lower Cr partition coefficient between olivine and basalt in the Moon can lead to more Cr enrichment in the lunar magma ocean, as well as more Cr enrichment in mantle-derived basalts in the Moon. Hence, even though Cr is typically a compatible element in terrestrial basalts, it is moderately incompatible in primitive lunar basalts, with a similar degree of incompatibility as V based on partition coefficients in this work, as also evidenced by the relatively constant V/Cr ratio of 0.039 ± 0.011 in lunar basalts. The confirmation of constant V/Cr ratio is important for constraining concentrations of Cr (slightly volatile and siderophile) and V (slightly siderophile) in the bulk silicate Moon.

中文翻译：

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月球玄武岩中橄榄石与熔体的微量元素分配

矿物/熔体分配系数已被广泛用于提供对岩浆过程的见解。橄榄石是月幔和母马玄武岩中最丰富和最重要的矿物之一。然而，没有系统的橄榄石/熔体划分数据可用于月球条件。我们报告了月球玄武岩中主矿物橄榄石及其熔体包裹体之间的微量元素分配数据。使用 Fe-Mg 交换系数评估平衡，导致在月球玄武岩 12040、12009、15016、15647 和 74235 中选择熔体包裹体-主橄榄石对。 21 种元素（Li、Mg、Al、Ca、测量了 Ti、V、Cr、Mn、Fe、Co、Y、Zr、Nb、Gd、Tb、Dy、Ho、Er、Tm、Yb 和 Lu)。除了 Li、V 和 Cr，与陆地样品的数据相比，这些元素在橄榄石熔体分配方面没有显着差异。在一些低 Mg# 的月球玄武岩中（橄榄石中 Mg# < 0.75，或熔体中 < ~0.5），Li 在橄榄石和熔体之间的分配系数高于已发表的陆地样品数据，这归因于 DLi 对Mg# 和缺乏低 Mg# 的文献 DLi 数据。V 在月球玄武岩中的分配系数测量为 0.17 至 0.74，显着高于陆地玄武岩（0.003 至 0.21），这可以用月球玄武岩中较低的氧逸度来解释。显着较高的 DV 可以解释为什么演化的月球玄武岩中的 V 含量低于陆地玄武岩。月球中橄榄石和玄武岩熔体之间的 Cr 分配系数为 0.11 至 0.62，比陆地环境中的低约 2 倍。这是令人惊讶的，因为以前的作者表明 Cr 分配系数与 fO2 无关。开发了一个基于准热力学的模型，以将 Cr 分配系数与橄榄石和熔体成分以及 fO2 关联起来。月球中橄榄石和玄武岩之间较低的 Cr 分配系数可以导致月球岩浆海洋中更多的 Cr 富集，以及月球中地幔源玄武岩中更多的 Cr 富集。因此，尽管 Cr 通常是陆地玄武岩中的相容元素，但它在原始月球玄武岩中是适度不相容的，根据这项工作中的分配系数，其不相容程度与 V 相似，这也证明了相对恒定的 V/Cr 比率在月球玄武岩中为 0.039 ± 0.011。