In near-infrared spectral studies, the relationship between the 1-μm absorption (Band I) center and the band area ratio (BAR, the area ratio of 2–1-μm absorption features) is useful in compositional and mineralogical analyses of ferrous mineral-bearing mixtures. Zhang and Cloutis (2020), https://doi.org/10.1029/2020ea001153, investigated various lunar ferrous iron-bearing rocks and minerals and found that pyroxene-bearing materials rich in ilmenite (Ilm), plagioclase (Pl), or glass are offset from the lunar olivine-clinopyroxene-orthopyroxene (Ol-Cpx-Opx) mixing line in the plot of the BAR versus the Band I center. To analyze the variation trends of the spectral properties of these mixtures with different components, this study presents a systematic evaluation of laboratory spectra of terrestrial and synthetic ferrous iron-bearing mineral mixtures based on published databases. In general, the mixing trends of the Pl-pyroxene mixtures, the glass-pyroxene mixtures, and the Ilm-basalt mixtures are consistent with the findings of Zhang and Cloutis (2020), https://doi.org/10.1029/2020ea001153. Moreover, this study also finds that the BAR of the Pl-pyroxene mixtures varies nonlinearly with different relative abundances and that the BAR is generally not sensitive to Pl abundances below 60%. For glass-pyroxene mixtures, the corresponding data points are usually appreciably offset from the Ol-Cpx-Opx mixing line at glass abundances above 20%. The BAR of the Ilm-basalt mixtures increases with increasing Ilm content, mainly due to the weakening of 1-μm absorption generally being greater than that of 2-μm absorption.

中文翻译：

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不同相对丰度的亚铁矿物混合物近红外光谱特性的变化

在近红外光谱研究中，1-μm 吸收（Band I）中心和带面积比（BAR，2-1-μm 吸收特征的面积比）之间的关系可用于黑色金属的成分和矿物学分析-轴承混合物。Zhang 和 Cloutis (2020)，https://doi.org/10.1029/2020ea001153，调查了各种月球含铁的含铁岩石和矿物，发现富含钛铁矿 (Ilm)、斜长石 (Pl) 或玻璃的含辉石材料在 BAR 与波段 I 中心的图中，从月球橄榄石-斜辉石-斜辉石 (Ol-Cpx-Opx) 混合线偏移。为了分析这些具有不同组分的混合物的光谱特性的变化趋势，这项研究基于已发表的数据库，对陆地和合成含铁亚铁矿物混合物的实验室光谱进行了系统评估。总的来说，Pl-辉石混合物、玻璃-辉石混合物和 Ilm-玄武岩混合物的混合趋势与 Zhang 和 Cloutis (2020), https://doi.org/10.1029/2020ea001153 的发现一致。此外，本研究还发现，Pl-辉石混合物的 BAR 随不同的相对丰度呈非线性变化，并且 BAR 通常对低于 60% 的 Pl 丰度不敏感。对于玻璃-辉石混合物，当玻璃丰度高于 20% 时，相应的数据点通常会明显偏离 Ol-Cpx-Opx 混合线。Ilm-玄武岩混合物的 BAR 随着 Ilm 含量的增加而增加，