Ureilite Meteorite Record of Shock Metamorphism and Parent Body Processes
Abstract
Ureilites are an abundant non-chondritic meteorite class that are petrographically similar to terrestrial ultramafic rocks, consisting mostly of coarse-grained olivine and pyroxene, with remarkably low occurrence of plagioclase feldspar. This work examines a suite of ureilites (six monomict ureilites and one polymict ureilite), primarily focusing on the mineral olivine as a recorder of shock damage. Optical petrography and Raman spectroscopy provide context information, and in-situmicro-X-ray diffraction (𝜇XRD) is used to obtain quantitative measurements of diffraction peak Full-Width-Half Maxima upon integration along the chi direction on 2D XRD patterns. Ureilites show an increasing streak length of FWHMχ and asterism (discrete subdomains showing spots) correlated with optical observation of increased shock in olivine grains. A peak fitting program is also developed by Matlab to fit complex peaks. This quantitative method contributes to a comprehensive shock classification system specifically for ureilites. In addition, the peak-fitting method, as it is a user-friendly design, can be easily applied to other samples for XRD analysis or spectroscopic analyses to estimate peak locations and intensities.