The Chelyabinsk meteorite: thermal history and variable shock effects recorded by the 40Ar-39Ar system
We studied three lithologies (light and dark chondritic and impact melt rock) differing in shock stage from the LL5 chondrite Chelyabinsk. Using the 40Ar-39Ar dating technique, we identified low- and high-temperature reservoirs within all samples, ascribed to K-bearing oligoclase feldspar and shock-...
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
2018
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| In: |
Meteoritics & planetary science
Year: 2018, Volume: 53, Issue: 3, Pages: 343-358 |
| ISSN: | 1945-5100 |
| DOI: | 10.1111/maps.13012 |
| Online Access: | Verlag, Pay-per-use, Volltext: http://dx.doi.org/10.1111/maps.13012 Verlag, Pay-per-use, Volltext: https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.13012 
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| Author Notes: | Mario Trieloff, Ekaterina V. Korochantseva, Alexei I. Buikin, Jens Hopp, Marina A. Ivanova, and Alexander V. Korochantsev |
| Summary: | We studied three lithologies (light and dark chondritic and impact melt rock) differing in shock stage from the LL5 chondrite Chelyabinsk. Using the 40Ar-39Ar dating technique, we identified low- and high-temperature reservoirs within all samples, ascribed to K-bearing oligoclase feldspar and shock-induced jadeite-feldspar glass assemblages in melt veins, respectively. Trapped argon components had variable 40Ar/36Ar ratios even within low- and high-temperature reservoirs of individual samples. Correcting for trapped argon revealed a lithology-specific response of the K-Ar system to shock metamorphism, thereby defining two distinct impact events affecting the Chelyabinsk parent asteroid (1) an intense impact event 1.7 ± 0.1 Ga ago formed the light-dark-structured and impact-veined Chelyabinsk breccia. Such a one-stage breccia formation is consistent with petrological observations and was recorded by the strongly shocked lithologies (dark and impact melt) where a significant fraction of oligoclase feldspar was transformed into jadeite and feldspathic glass; and (2) a young reset event 30 Ma ago particularly affected the light lithology due to its low argon retentivity, while the more retentive shock-induced phases were more resistant against thermal reset. Trapped argon with 40Ar/36Ar ratios up to 1900 was likely incorporated during impact-induced events on the parent body, and mixed with terrestrial atmospheric argon contamination. Had it not been identified via isochrons based on high-resolution argon extraction, several geochronologically meaningless ages would have been deduced. |
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| Item Description: | Gesehen am 08.08.2018 Article was first published on 12 December 2017 Im Titel sind die Ziffern "40" und "39" hochgestellt |
| Physical Description: | Online Resource |
| ISSN: | 1945-5100 |
| DOI: | 10.1111/maps.13012 |