Quantitative Mineralogy of Planetary Silicate Ternary Mixtures using Raman Spectroscopy

Several Raman payloads are being or planning to detect minerals on lunar and planetary surfaces. The proportion of minerals could provide clues about the processes that formed them and hence help decipher the planet's geological history. However, previous studies on planetary materials using Raman spectroscopy mainly focused on mineral identification. In this study, we introduce new Raman quantitative models based on spectral measurements of silicate ternary mixtures in the laboratory. The linear relationships between Raman integrated intensities and mineral proportions are observed. We demonstrate that our quantitative models based on this linear relationship are more accurate than previous attempts and are independent of instrumental setup. Using these models, we obtain the relative mineral proportions of lunar soil (CE5C0600) and find that augite is the dominant mineral at the Chang'e-5 landing site. Besides, our results indicated that the intrinsic relative Raman scattering cross section of feldspar, olivine, and augite is 1.4: 2.4: 1. This coefficient is helpful for more accurate mineral quantification.