Characterization of Northwest Africa 6410 L6 ordinary chondrite using scanning electron microscopy, X‐ray diffraction and Mössbauer spectroscopy

Abstract Ordinary chondrites preserve important information on the mineralogical and phase evolution as well as thermal metamorphism of their parent bodies. Quantitative characterization of minerals/phases and cation distributions in silicates using complementary analytical techniques provides valuable constraints on their crystal chemistry and thermal history. In this study, we investigate the Northwest Africa (NWA) 6410 L6 ordinary chondrite using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), and 57 Fe Mössbauer spectroscopy. Optical microscopy revealed significant porosity of the polished section together with abundant chondrules and chondrule relics. The mineralogical/phase composition and crystal chemistry of the meteorite were characterized by SEM, EDS, XRD, and Mössbauer spectroscopy. XRD identified the major mineral phases, whereas Mössbauer spectroscopy resolved the Fe‐bearing mineral/phase compounds and the distribution of Fe 2+ between the M1 and M2 crystallographic sites in olivine and orthopyroxene. The occupancies of Fe 2+ and Mg 2+ at the M1 and M2 sites were determined from XRD refinements, while the ratios of Fe 2+ site populations in silicates were derived from Mössbauer spectra. The Fe 2+ M1/M2 site‐occupancy ratios obtained independently by XRD and Mössbauer spectroscopy are in good agreement, demonstrating the consistency of the two approaches. The temperatures of cation equilibrium distribution calculated from XRD and Mössbauer spectroscopy are 570 and 626 K, respectively, for olivine and 679 and 686 K, respectively, for orthopyroxene. Classification based on the relative spectral areas (roughly the relative Fe fractions) of characteristic Mössbauer components confirms that NWA 6410 belongs to the L group of ordinary chondrites.