Raman Spectroscopy Analysis of Maskelynite in M-S4 Lonar crater Samples

Introduction

Lonar crater in India offers important mineralogy insights into impact-related processes. One of the key minerals found within the crater is maskelynite, a high-pressure diaplectic glass formed by shock metamorphism during meteorite impacts (Xie et al. 2020). In this study, we conducted a Raman spectroscopy analysis on several samples of M-S4 shocked basalt (maskelynite-bearing from solid state shock pressures and not M-S5 through M-S7 in which labradorite is melted) collected from Lonar crater to identify maskelynite phenocrysts, contributing to our understanding of the crater's geology and the processes involved in maskelynite formation. The presence of maskelynite is an indicator of an intense shock event (Wright et al. 2011; Jaret et al. 2015).

Method

The method prepared thin M-S4 sample sections for Raman spectroscopy. Raman spectra used a red excitation laser (785 nm), 20X objective lens, 10 s exposure time, and 10% laser power. Spectra were obtained from various 30-45 micron maskelynite phenocrysts within M-S4 samples, while smaller needles were ignored. Baselines were subtracted, and an average Raman spectrum was generated by combining 10 individual spectra. The ~570 cm-1 peak is attributed to maskelynite. (Fritz et al. 2005; Kanemaru, et al. 2020).

Discussion

The feature at 576 cm^-1 on the averaged Raman spectrum of Lonar maskelynite in basalts shocked ~20-40 GPa is particularly noteworthy (Fig.1). The presence of maskelynite in FTIR images of shocked soil from Lonar has been shown by Wright and Michalski (2024). Figures 4 and 9 of Wright et al. (2011) investigated the TIR emission spectrum of Lonar maskelynite.

Figure 1. The average Raman spectrum of phenocrysts of maskelynite in MS-4 Lonar samples.

The study connects Lonar crater's maskelynite to Martian meteorites, enhancing understanding of meteorite impacts on Mars' mineral composition and geologic history (Fritz et al. 2005; El Goresy et al. 2013). The findings link Lonar crater's maskelynite to Martian meteorites, providing vital insights into meteorite impacts' effects on Mars' mineral composition and geologic history.

Conclusion

Lonar crater is a great analog for studying Martian surface materials and processes due to its similarities with Mars' impact craters. This study successfully characterized maskelynite phenocrysts within M-S4 Lonar crater samples using Raman spectroscopy (Xie et al. 2021). The average Raman spectra offer crucial insights into the composition and formation of maskelynite. The research highlights Raman spectroscopy's significance as a dependable method for mineral analysis in impact-related samples, with potential applications at meteorite impact sites globally.

References:

El Goresy, A., et al. 2013. G.C.A, 101, pp.233-262.

Fritz, J., et al. 2005. Antarctic Meteorite Research, Vol. 18, p. 96, 18, p.96.

Jaret, S.J., et al. 2015. J.  Geophysical Research: Planets, 120 (3), pp.570-587.

Kanemaru, R., et al. 2020. Polar Science, 26, p.100605.

Wright, S.P., et al. 2011. J. G.R.P. 116 (E9).

Wright, S.P. and J.R. Michalski, 2024, JGR-Planets, doi: 10.1029/2023JE007913.

Xie, T., et al. 2020. M & P Science, 55 (7), pp.1471-1490.

Xie, T., et al. 2021. M & P Science, 56 (9), pp.1633-1651.