Diana Bolser¹, Thomas J. Zega^2,3, Abu Asaduzzaman³, Stefan Bringuier³, Steven B. Simon⁴, Lawrence Grossman⁴, Michelle S. Thompson² and Kenneth J. Domanik^1
1Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA
²Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, Tucson, Arizona, USA
³Department of Materials Science & Engineering, University of Arizona, Tucson, Arizona, USA
⁴Department of Geophysical Sciences, University of Chicago, Chicago, Illinois, USA

A coordinated, electron-backscatter-diffraction (EBSD) and transmission electron microscope (TEM) study was undertaken to obtain information on the origin of rims on refractory inclusions in the Allende and Axtell CV3 chondrites. These measurements were supported by theoretical modeling using density functional theory. Crystal-orientation analysis of Wark-Lovering rims via EBSD revealed pyroxene grains with similar crystallographic orientations to one another in both inclusions. An epitaxial relationship between grains within the diopside and anorthite rim layers was observed in Allende. TEM examination of the rims of both samples also revealed oriented crystals at depth. The microstructural data on the rims suggest that grain clusters grew in the form of three-dimensional islands. Density functional theory calculations confirm that formation of oriented grain islands is the result of energy minimization at high temperature. The results point toward condensation as the mode of origin for the rims studied here.

Reference
Bolser D, Zega TJ, Asaduzzaman A, Bringer S, Simon SB, Grossman L, Thompson MS and Domanik KJ (2016) Microstructural analysis of Wark-Lovering rims in the Allende and Axtell CV3 chondrites: Implications for high-temperature nebular processes. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12620]
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