Iron‐bearing minerals are a major component of materials on the lunar surface, and many of them can be distinguished based on the diagnostic absorption features in visible and near‐infrared reflectance spectra. The relationship between the 1 µm absorption (Band I) center and the band area ratio (BAR), defined as the ratio of 2–1 µm absorption areas, provides a sensitive way to estimate the relative abundance of olivine (Ol) and pyroxene. In the plot of the BAR value versus the Band I center, the Ol‐orthopyroxene (Opx) mixing line (derived from terrestrial materials) is strictly applicable only to Ol‐Opx mixtures. Based on published database of laboratory spectra and compositional data for lunar rocks and mineral separates, this study investigated the spectral characteristics of a variety of common Fe²⁺‐bearing lunar minerals and rocks, such as clinopyroxene (Cpx), ilmenite‐rich basalt, pyroxene‐bearing anorthosite, and glass‐rich impact melt. The lunar Ol‐Cpx‐Opx mixing line for rocks and minerals is determined, which contains less curvature than the Ol‐Opx mixing line, consistent with both the higher Fe²⁺ content of lunar mafic silicates and the presence of appreciable Cpx. This study suggests that some of the pyroxene‐bearing lunar materials that are rich in ilmenite, glass, or plagioclase can also be distinguished by this method. These results indicate that the plot of the BAR value versus the Band I center is a useful tool for spectral analysis of lunar composition and mineralogy, especially for those having pyroxene‐dominated spectra.

中文翻译：

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月相黑色金属矿物混合物的近红外光谱

含铁矿物是月球表面物质的主要组成部分，其中许多可以根据可见光和近红外反射光谱中的诊断吸收特征加以区分。1 µm吸收（带I）中心与谱带面积比（BAR）之间的关系定义为2–1 µm吸收面积之比，为估算橄榄石（Ol）和辉石的相对丰度提供了一种灵敏的方法。在BAR值相对于Band I中心的曲线图中，邻邻二甲苯（Opx）混合线（源自地面材料）严格仅适用于Ol-Opx混合物。基于已发布的实验室光谱数据库和月球岩石和矿物分离物的成分数据，本研究调查了各种常见的Fe ²⁺的光谱特征含月球的矿物和岩石，例如斜辉石（Cpx），富含钛铁矿的玄武岩，含辉石的钙钛矿和富含玻璃的冲击熔体。确定了岩石和矿物的月球Ol-Cpx-Opx混合线，其曲率比Ol-Opx混合线小，这与月铁镁硅酸盐的Fe ²⁺含量较高和可观的Cpx的存在相一致。这项研究表明，这种方法还可以区分一些富含辉石的月球物质，其中富含钛铁矿，玻璃或斜长石。这些结果表明，BAR值与波段I中心的关系图是有用的工具，可用于分析月球成分和矿物学，特别是对于以辉石为主的光谱。