The Chelyabinsk meteorite: New insights from a comprehensive electron microscopy and Raman spectroscopy study with evidence for graphite in olivine of ordinary chondrites

1,2,3David Kaeter,1Martin A. Ziemann,2Ute Böttger,4Iris Weber,5Lutz Hecht,6Sergey A. Voropaev,6Alexander V. Korochantsev,7Andrey V. Kocherov
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13027]
1Institute for Earth and Environmental Sciences, University of Potsdam, Potsdam, Germany
2Institute of Optical Sensor Systems, German Aerospace Center, Berlin, Germany
3iCRAG, School of Earth Sciences, University College Dublin, Dublin D04 N2E5, Ireland
4Institute of Planetology, University of Münster, Münster, Germany
5Museum für Naturkunde, Berlin, Germany
6Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia
7Chelyabinsk State University, Chelyabinsk, Russia
Published by arrangement with John Wiley & Sons

We present results of petrographic, mineralogical, and chemical investigations of three Chelyabinsk meteorite fragments. Three distinct lithologies were identified: light S3 LL5, dark S4–S5 LL5 material, and opaque fine-grained former impact melt. Olivine–spinel thermometry revealed an equilibration temperature of 703 ± 23 °C for the light lithology. All plagioclase seems to be secondary, showing neither shock-induced fractures nor sulfide-metal veinlets. Feldspathic glass can be observed showing features of extensive melting and, in the dark lithology, as maskelynite, lacking melt features and retaining grain boundaries of former plagioclase. Olivine of the dark lithology shows planar deformation features. Impact melt is dominated by Mg-rich olivine and resembles whole-rock melt. Melt veins (<2 mm) are connected to narrower veinlets. Melt vein textures are similar to pegmatite textures showing chilled margins, a zone of inward-grown elongated crystals and central vugs, suggesting crystallization from supercooled melt. Sulfide-metal droplets indicate liquid immiscibility of both silicate and sulfide as well as sulfide and metal melts. Impact melting may have been an important factor for differentiation of primitive planetary bodies. Graphite associated with micrometer-sized melt inclusions in primary olivine was detected by Raman mapping. Carbon isotopic studies of graphite could be applied to test a possible presolar origin.

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