Integrated Spectroscopy of Pyroxenes: Pushing Remote Geochemical Analyses Further

With the new generation of missions flying high spectral resolution spectrometers to the Moon, it is critical to strengthen the laboratory framework for remote mineralogical analyses. While mafic minerals are readily identifiable in the near-infrared, methods to better quantify specific chemistry and mineralogy are being improved. Pyroxenes, in particular, offer exciting possibilities for characterizing both the composition and thermal history of outcrops on the lunar surface. We will present integrated results from electron microprobe analyses, near-infrared and Mössbauer spectroscopy of a suite of pure Mg-Fe-Ca synthetic pyroxenes that allow us to directly link spectral parameters with specific absorptions and the crystal chemistry that produces them. Our results suggest that it is possible to go beyond the commonly used groupings of ‘high-Ca' and ‘low-Ca' pyroxene in remote analyses and further group pyroxenes as ortho- or clino- pyroxenes. The degree of Mg-Fe ordering between the M1 and M2 sites in pyroxene can also be assessed with high-spectral resolution remotely detected spectra. These results will then be applied to a suite of lunar pyroxene mineral separates and bulk rock samples to validate our methods with natural lunar samples.