We investigated mid-infrared reflectance spectra of anorthosite samples from Mt. Briand near the Manicouagan impact structure. Microprobe analyses of the plagioclase minerals reveal that they have a similar chemical composition (labradoritic), which is corroborated by the location of the Christiansen Feature at around 7.96 m (1256 cm⁻¹). However, their respective spectral shapes differ from each other in the region of the reststrahlen bands. This is linked to the degree of Al,Si order within the plagioclase minerals, which also correlates with the previously assumed distance of the sample site to the impact melt. Powdering and sieving led to remarkable changes in the spectra resulting from different mechanical stability of minerals contained in the sample. Our data show that even very weakly shocked (6–10 GPa, shockstage S2) anorthosites could show spectra of Al,Si disordered plagioclase which we attribute to post shock heating after the impact shock. Consequently, the degree of Al,Si order has to be taken into account in the interpretation of remote sensing data. A comparison of synthetic linear mixture with an average Mercury spectrum reveals the possible presence of more or less anorthositic material with reduced degree of Al,Si order of the plagioclase component on Mercury's surface. The results of our study are helpful for the interpretation of data returned by space missions, especially for MERTIS - an infrared spectrometer on its way to Mercury.

中文翻译：

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加拿大 Manicouagan 火山口附近斜长岩样品的中红外光谱，作为水星和其他陆地太阳系物体遥感的类似物

我们研究了来自 Mt. 的斜长岩样品的中红外反射光谱。马尼科根撞击结构附近的布里安德。斜长石矿物的微探针分析表明它们具有相似的化学成分（拉长石），Christiansen Feature 位于约 7.96  m（1256 cm ^-1）。然而，它们各自的光谱形状在其余光谱带的区域中彼此不同。这与斜长石矿物中铝、硅的有序度有关，这也与之前假设的样品点到冲击熔体的距离有关。由于样品中所含矿物质的不同机械稳定性，粉化和筛分导致光谱发生显着变化。我们的数据表明，即使是非常微弱的冲击（6-10 GPa，冲击阶段 S2）斜长石也可以显示 Al、Si 无序斜长石的光谱，我们将其归因于冲击冲击后的冲击后加热。因此，在解释遥感数据时必须考虑铝、硅的有序程度。合成线性混合物与平均水银光谱的比较揭示了可能存在或多或少的斜长石材料，水星表面上斜长石组分的铝、硅有序度降低。我们的研究结果有助于解释太空任务返回的数据，特别是对于 MERTIS - 前往水星途中的红外光谱仪。