40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa
Studies of meteorites are based mostly on samples that fell to Earth in the recent past (i.e., a few million years at most). The Morokweng LL-chondrite meteorite is a particularly interesting specimen as its fall is much older (ca. 145 Ma) than most other meteorites and because it is the only macro-...
| Main Authors: | , , , |
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| Format: | Journal Article |
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Pergamon-Elsevier Science Ltd
2010
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| Online Access: | http://hdl.handle.net/20.500.11937/34976 |
| _version_ | 1848754370320007168 |
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| author | Jourdan, Fred Andreoli, M. McDonald, I. Maier, W. |
| author_facet | Jourdan, Fred Andreoli, M. McDonald, I. Maier, W. |
| author_sort | Jourdan, Fred |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Studies of meteorites are based mostly on samples that fell to Earth in the recent past (i.e., a few million years at most). The Morokweng LL-chondrite meteorite is a particularly interesting specimen as its fall is much older (ca. 145 Ma) than most other meteorites and because it is the only macro-meteorite clast (width intersected in drill core: 25 cm) found in a melt sheet of a large impact structure. When applied to the Morokweng meteorite, 40Ar/39Ar thermochronology provides an opportunity to study (1) effects associated with pre-impact and post-impact processes and (2) collision events within a potentially distinct and as yet unsampled asteroid population.A single multi-grain aliquot yielded an inverse isochron age of 625 ± 163 Ma. This suggests a major in-space collisional event at this time. We have modeled the diffusion of 40Ar* within the meteorite and plagioclase during and after the 145 Ma impact on Earth to tentatively explain why pre-terrestrial impact 40Ar* has been preserved within the plagioclase grains. The 145 Ma terrestrial impact age is recorded in the low-retentivity sites of the meteorite plagioclase grains that yielded a composite inverse isochron age at 141 ± 15 Ma and thus, confirms that age information about major (terrestrial or extraterrestrial) impacts can be recorded in the K-rich mineral phases of a meteorite and measured by the 40Ar/39Ar technique. More studies on fossil meteorites need to be carried out to understand if the rough 0.6 Ga age proposed here corresponds to major LL-chondrite asteroid population destructions or, rather, to an isolated collision event. |
| first_indexed | 2025-11-14T08:39:20Z |
| format | Journal Article |
| id | curtin-20.500.11937-34976 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:39:20Z |
| publishDate | 2010 |
| publisher | Pergamon-Elsevier Science Ltd |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-349762017-09-13T16:07:33Z 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa Jourdan, Fred Andreoli, M. McDonald, I. Maier, W. Studies of meteorites are based mostly on samples that fell to Earth in the recent past (i.e., a few million years at most). The Morokweng LL-chondrite meteorite is a particularly interesting specimen as its fall is much older (ca. 145 Ma) than most other meteorites and because it is the only macro-meteorite clast (width intersected in drill core: 25 cm) found in a melt sheet of a large impact structure. When applied to the Morokweng meteorite, 40Ar/39Ar thermochronology provides an opportunity to study (1) effects associated with pre-impact and post-impact processes and (2) collision events within a potentially distinct and as yet unsampled asteroid population.A single multi-grain aliquot yielded an inverse isochron age of 625 ± 163 Ma. This suggests a major in-space collisional event at this time. We have modeled the diffusion of 40Ar* within the meteorite and plagioclase during and after the 145 Ma impact on Earth to tentatively explain why pre-terrestrial impact 40Ar* has been preserved within the plagioclase grains. The 145 Ma terrestrial impact age is recorded in the low-retentivity sites of the meteorite plagioclase grains that yielded a composite inverse isochron age at 141 ± 15 Ma and thus, confirms that age information about major (terrestrial or extraterrestrial) impacts can be recorded in the K-rich mineral phases of a meteorite and measured by the 40Ar/39Ar technique. More studies on fossil meteorites need to be carried out to understand if the rough 0.6 Ga age proposed here corresponds to major LL-chondrite asteroid population destructions or, rather, to an isolated collision event. 2010 Journal Article http://hdl.handle.net/20.500.11937/34976 10.1016/j.gca.2009.11.032 Pergamon-Elsevier Science Ltd restricted |
| spellingShingle | Jourdan, Fred Andreoli, M. McDonald, I. Maier, W. 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa |
| title | 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa |
| title_full | 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa |
| title_fullStr | 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa |
| title_full_unstemmed | 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa |
| title_short | 40Ar/39Ar thermochronology of the fossil LL6- chondrite from Morokweng Crater, South Africa |
| title_sort | 40ar/39ar thermochronology of the fossil ll6- chondrite from morokweng crater, south africa |
| url | http://hdl.handle.net/20.500.11937/34976 |