A detailed µ-FTIR study of Hermean glasses: Spectral mainband shape and flank, what do they tell us?

Abstract

Understanding the unique spectral signatures of glasses is relevant in a remote sensing context. Three basaltic glasses characterized by the system SiO₂-Al₂O₃-MgOCaO, with up to 0.3–3.7 wt. % FeO, 0 to 7.0 wt. % Na₂O, and <1 wt. % of TiO₂, Cr₂O₃, MnO, and K₂O are investigated spectrally in this study. We found a flank-like attachment to the dominant mainband vibration (∼ 1060 and 944cm^-1) located between 800 – 650cm^-1 in the reflectance mid-infrared spectra (MIR) that correlates well with the respective polymerization degree of the glass. We furthermore report the occurrence of a peak splitting in the mainband vibration in the sodium – poor glass batch between 1180 and 900cm^-1, which is not attributable to incipient crystallization processes, but is probably caused by Mg²⁺ assuming roles as both, charge balancing cation and modifier. The results of this study were compared with glasses from Chang'E lunar samples reported by Zeng et al. [1].