A new empirical approach for modal abundance estimation of olivine and pyroxene in ordinary chondrites using reflectance spectroscopy

Estimating mineral abundance in meteorites provides crucial information about the early solar system and planetary formation processes. This study presents a new empirical approach for the estimation of modal abundance of olivine (Ol), high-calcium pyroxene (HCP), and low-calcium pyroxene (LCP) using band area ratio (BAR), a spectral parameter derived using reflectance spectroscopy. Using spectral data of 22 mineral mixtures acquired from the RELAB spectral library, the BAR values were initially calculated. These BAR values were then plotted against Ol% and HCP%, and based on the trends observed, a set of equations was formulated to get the initial estimate of mineral abundances. To apply these to actual samples, an error reduction framework has been developed that involves determination of a class-specific correction factor (CF) for H, L, and LL types of ordinary chondrites (OCs) to account for the presence of other minerals, metals, and impurities. The CF is a quantitative adjustment that is subtracted from the initial estimates to align calculations with the actual values. After application of the CF, the 1σ uncertainties associated with the abundance estimates were found to be ±1.85% for Ol, ±0.91% for HCP, and ±1.63% for LCP. The study demonstrates the estimation of the mineral abundances of seven OCs, using spectral analysis conducted at the Planetary Remote Sensing Laboratory (PRSL), Physical Research Laboratory (PRL). The proposed approach is robust even for bulk samples analyzed under different viewing geometries and provides a rapid, nondestructive alternative to traditional techniques for mineral abundance estimation in meteorites, planetary samples, and analogs.