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

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

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...

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Bibliographic Details
Published in:Meteoritics & planetary science Vol. 53; no. 3; pp. 416 - 432
Main Authors: Kaeter, David, Ziemann, Martin A., Böttger, Ute, Weber, Iris, Hecht, Lutz, Voropaev, Sergey A., Korochantsev, Alexander V., Kocherov, Andrey V.
Format: Journal Article
Language:English
Published: Hoboken Wiley Subscription Services, Inc 01-03-2018
Subjects:
Chondrites
Crystallization
Crystals
Deformation
Electron microscopy
Elongation
Grain boundaries
Graphite
Immiscibility
Lithology
Melting
Melts
Metals
Meteorites
Meteors & meteorites
Miscibility
Olivine
Pegmatite
Plagioclase
Spectroscopy
Sulfides
Thermometry
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Summary: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.
ISSN:1086-9379
1945-5100
DOI:10.1111/maps.13027