Open AccessNear-infrared spectroscopy of Ca-rich clinopyroxenes revisited: A new interpretation of anomalous type-B spectra and implications for remote sensing of inner solar system bodies
Author(s) -
Yassir A. Abdu
Publication year - 2019
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1258/1/012030
Subject(s) - pigeonite , diopside , meteorite , spectroscopy , pyroxene , spectral line , chemistry , augite , crystallography , analytical chemistry (journal) , mineralogy , materials science , physics , astrobiology , olivine , quartz , chromatography , plagioclase , quantum mechanics , astronomy , composite material
Four Ca-rich clinopyroxene samples (3 terrestrial clinopyroxenes and a druse clinopyroxene from the D’Orbigny meteorite) have been studied by near-infrared (NIR) spectroscopy and X-ray structure refinement in order to address the issue of anomalous type-B NIR spectra seen in some terrestrial and extraterrestrial Ca-rich clinopyroxenes. The D’Orbigny druse clinopyroxene shows a typical type-B NIR spectrum, with two absorption bands located at ~ 1.1 and 2.3 μm. Based on previous Mössbauer and X-ray structure refinement results on synthetic clinopyroxenes, the 1.1 μm band is assigned to Fe 2+ at the M1 site in diopside and high-pigeonite (i.e. pigeonite with C2/c symmetry), and the 2.3 μm band to Fe 2+ at the M2 site in high-pigeonite. A comparison of NIR spectral type and X-ray structure refinement of the studied samples indicates that the average structure refinement of all type-B clinopyroxenes show a residual electron density peak in the difference-Fourier synthesis, corresponding to the split M2’ site which is mainly occupied by Fe 2+ . The results present a new interpretation for type-B NIR spectra of Ca-rich clinopyroxenes.