Quantitative Mineral Analysis of Ordinary Chondrites and Primitive Achondrites Using Reflectance Spectroscopy

Abstract Visible and near‐infrared spectroscopy is a widely used method to determine the mineral compositions of meteorites and asteroids. In this study, we first investigated the association of multiple spectral parameters with mineral compositions using published laboratory spectra and mineral analysis of ordinary chondrites and primitive achondrites. New models for deriving the abundances of mafic silicate minerals were determined. Second, the influence of different mineral compositions on the 1.25 μm region is discussed. Finally, a method to distinguish the ordinary chondrites from primitive achondrites is developed. Our results suggest that the 1.25–1 μm band depth ratio (BDR 1.25) and 1 μm band width (BW I) are mainly associated with mineral abundances and to a lesser extent, compositions. Olivine is the dominant mafic mineral phase that affects the 1.25 μm region in ordinary chondrites and primitive achondrites. The plot of the BDR 1.25 versus the BW I is a useful method for correctly distinguishing about 90% of the primitive achondrites from ordinary chondrites. It relies largely on differences in olivine abundance and olivine/pyroxene ratios and to a lesser extent, olivine composition. The quantitative mineral analysis in this study based on the correlation between the spectra and mineralogy of ordinary chondrites and primitive achondrites provides a chance for understanding the petrology and geochemistry of S‐type asteroids. This study can also distinguish the partially melted S‐type asteroids (parent body of primitive achondrites) from the unmelted S‐type asteroids (parent body of ordinary chondrites).

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