Mineralogical and spectroscopic investigation of enstatite chondrites by X‐ray diffraction and infrared reflectance spectroscopy

Abstract

[1] The mineralogy and infrared reflectance spectra of 13 Enstatite (E) chondrite meteorite finds spanning the full range of textural alteration grades in both EL and EH classes have been investigated. Rietveld refinement of high-resolution powder X-ray diffraction (XRD) data was used to determine quantitative major mineral abundances. Sample-correlated mid-infrared (2.0 to 25.0 mm; 4500 cm −1 to 400 cm −1 ) reflectance infrared spectra were collected for each meteorite. Spectral features due to the fundamental lattice vibrations of the silicates, primarily enstatite, dominate the spectra of these meteorites over most of the spectral range investigated. The spectral features related to primary (i.e., pre-terrestrial) mineralogy include fundamental stretching and bending lattice modes (∼8.3-25.0 mm; 1200-400 cm), overtones and combinations of the fundamental modes (∼4.5-6.1 mm; 2200-1650 cm −1 ), and the principle Christensen feature (∼8.3 mm; 1200 cm −1 ). Terrestrial weathering products including Fe-oxyhydroxides, gypsum, and carbonates occur in most of these meteorites and contribute to some spectral features: particularly an asymmetric feature near ∼2.6 to 3.8 mm (3800 to 2600 cm

High surface porosity as the origin of emissivity features in asteroid spectra

“…3). The similarity between the KBr-diluted meteorite and the asteroid spectra suggests that the new sample preparation method (Izawa et al, 2010;King et al, 2011, K12) better reproduces the actual properties of asteroid regolith. This suggests a high level of porosity of the surface regolith for those asteroids as independently indicated by both the objects thermal inertia and radar albedo (see next section).…”

Modal mineralogy of CI and CI-like chondrites by X-ray diffraction

“…These values are within those generally considered to represent a good fit (e.g. Young, 1993;Izawa et al, 2010). The model pattern is constructed by summing the mineral standard patterns (i.e.…”

A plausible link between the asteroid 21 Lutetia and CH carbonaceous chondrites

“…), and also that these meteorites do not show the Christiansen peak around 9.3 μm (~1075 cm −1 ), reported in a spectrum of 21 Lutetia and common in CCs (Izawa et al. ; Barucci et al. ).…”