A Raman spectroscopy-compositional-structural investigation of lunar surface materials and analogues

We investigated the Raman spectroscopy of 35 rock and mineral samples of composition relevant to the lunar surface: pyroxenes, olivine, plagioclase feldspars and oxides. The Raman spectra were analysed in the context of their compositional and structural properties to develop robust correlations to enable their detection on the lunar surface by Raman spectroscopy. We developed and implemented a spectral deconvolution program to model the fluorescence background and various Raman peaks to extract their positions in wavenumber space. Relations were developed between the Raman peak positions of pyroxenes around 325, 670 and 1000 cm(-1) with their compositions in terms of enstatite, ferrosilite and wollastonite components. For olivines, we verified previously determined correlations between the positions of the olivine-related peak doublet between 800 and 880 cm(-1) with forsterite content. We also discuss the main signatures detected in the Raman spectra of plagioclases and oxides. The derived relationships were examined using Raman spectra of the matrix and several inclusions of the lunar meteorite NWA12593. We were able to identify the main endmembers of the selected surface spots as pyroxenes, plagioclase feldspars and olivine. We used the previous correlations to separate orthopyroxene from clinopyroxene signatures and to propose a composition of the inclusions of the meteorite. The results of this study demonstrate the utility of Raman spectroscopy for determining the mineralogy of the lunar surface.