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

• Mg 2+ linked to decoupling process of asymmetric stretching vibration in MIR. • Flank intensity correlated to polymerization degree of complex multi-cation glasses. • Cation concentration thresholds affect modifier-, charge balance, and former roles. Understanding the unique spectral signatures of glasses is relevant in a remote sensing context. Three basaltic glasses characterized by the system SiO 2 -Al 2 O 3 -MgO CaO, with up to 0.3–3.7 wt. % FeO, 0 to 7.0 wt. % Na 2 O, and <1 wt. % of TiO 2 , Cr 2 O 3 , MnO, and K 2 O 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 Mg 2+ 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].