Petrological Studies on Chondrules in Yamato-74 Meteorites
Crystallization of chondrule is investigated through the study of Yamato-74191,-74155,-74079,-74371,and -74647 meteorites. Bulk compositions of chondrules are calculated from modal analyses and mineral compositions, and are projected in the MgO-Al_2O_3-SiO_2 system with the compositions of glasses i...
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Department of Geology and Mineralogy, Faculty of Science, Hokkaido University
1979
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ftnipr:oai:nipr.repo.nii.ac.jp:00000963 2023-05-15T17:10:58+02:00 Petrological Studies on Chondrules in Yamato-74 Meteorites Makoto Kimura Kenzo Yagi Kosuke Onuma 1979-03 https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=963 http://id.nii.ac.jp/1291/00000963/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=963&item_no=1&attribute_id=18&file_no=1 en eng Department of Geology and Mineralogy, Faculty of Science, Hokkaido University https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=963 http://id.nii.ac.jp/1291/00000963/ AA00733561 Memoirs of National Institute of Polar Research. Special issue, 12, 114-133(1979-03) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=963&item_no=1&attribute_id=18&file_no=1 Departmental Bulletin Paper P(論文) 1979 ftnipr 2022-11-12T19:41:48Z Crystallization of chondrule is investigated through the study of Yamato-74191,-74155,-74079,-74371,and -74647 meteorites. Bulk compositions of chondrules are calculated from modal analyses and mineral compositions, and are projected in the MgO-Al_2O_3-SiO_2 system with the compositions of glasses in chondrules, from which the process of crystallization of chondrule is suggested. According to the investigation in the peritectic system, chondrules may be regarded as products of supercooling crystallization. Variety of textures of chondrules, which are classified into porphyritic, barred, radiating, and cryptocrystalline types, is also explained by various degrees of supercooling of droplet (chondrule). Abnormal FeO/FeO+MgO ratios of the olivines, pyroxenes, and glasses, and extraordinary high K_D^ _<Mg-Fe> values show the change of atmosphere in chondrule. It possibly resulted from a reaction in ambient gas and its diffusion into chondrule. On the basis of mineralogy of chondrules and matrix in the Yamato-74191,a possible process of accretion of chondrules to parent body is discussed. Evidences of recrystallization of chondrules often occurring before accretion are suggested. Most of chondrules have thin rims around them, whose average composition is similar to that of the silicate portion of the L-chondrites. The rims might have been attached to chondrules after recrystallization and before accretion. Distinct shapes of chondrules mean that their accretion speeds to parent body were fairly low. Report Memoirs of National Institute of Polar Research Polar Research National Institute of Polar Research Repository, Japan Yamato ENVELOPE(35.583,35.583,-71.417,-71.417) |
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Open Polar |
collection |
National Institute of Polar Research Repository, Japan |
op_collection_id |
ftnipr |
language |
English |
description |
Crystallization of chondrule is investigated through the study of Yamato-74191,-74155,-74079,-74371,and -74647 meteorites. Bulk compositions of chondrules are calculated from modal analyses and mineral compositions, and are projected in the MgO-Al_2O_3-SiO_2 system with the compositions of glasses in chondrules, from which the process of crystallization of chondrule is suggested. According to the investigation in the peritectic system, chondrules may be regarded as products of supercooling crystallization. Variety of textures of chondrules, which are classified into porphyritic, barred, radiating, and cryptocrystalline types, is also explained by various degrees of supercooling of droplet (chondrule). Abnormal FeO/FeO+MgO ratios of the olivines, pyroxenes, and glasses, and extraordinary high K_D^ _<Mg-Fe> values show the change of atmosphere in chondrule. It possibly resulted from a reaction in ambient gas and its diffusion into chondrule. On the basis of mineralogy of chondrules and matrix in the Yamato-74191,a possible process of accretion of chondrules to parent body is discussed. Evidences of recrystallization of chondrules often occurring before accretion are suggested. Most of chondrules have thin rims around them, whose average composition is similar to that of the silicate portion of the L-chondrites. The rims might have been attached to chondrules after recrystallization and before accretion. Distinct shapes of chondrules mean that their accretion speeds to parent body were fairly low. |
format |
Report |
author |
Makoto Kimura Kenzo Yagi Kosuke Onuma |
spellingShingle |
Makoto Kimura Kenzo Yagi Kosuke Onuma Petrological Studies on Chondrules in Yamato-74 Meteorites |
author_facet |
Makoto Kimura Kenzo Yagi Kosuke Onuma |
author_sort |
Makoto Kimura |
title |
Petrological Studies on Chondrules in Yamato-74 Meteorites |
title_short |
Petrological Studies on Chondrules in Yamato-74 Meteorites |
title_full |
Petrological Studies on Chondrules in Yamato-74 Meteorites |
title_fullStr |
Petrological Studies on Chondrules in Yamato-74 Meteorites |
title_full_unstemmed |
Petrological Studies on Chondrules in Yamato-74 Meteorites |
title_sort |
petrological studies on chondrules in yamato-74 meteorites |
publisher |
Department of Geology and Mineralogy, Faculty of Science, Hokkaido University |
publishDate |
1979 |
url |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=963 http://id.nii.ac.jp/1291/00000963/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=963&item_no=1&attribute_id=18&file_no=1 |
long_lat |
ENVELOPE(35.583,35.583,-71.417,-71.417) |
geographic |
Yamato |
geographic_facet |
Yamato |
genre |
Memoirs of National Institute of Polar Research Polar Research |
genre_facet |
Memoirs of National Institute of Polar Research Polar Research |
op_relation |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=963 http://id.nii.ac.jp/1291/00000963/ AA00733561 Memoirs of National Institute of Polar Research. Special issue, 12, 114-133(1979-03) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=963&item_no=1&attribute_id=18&file_no=1 |
_version_ |
1766067722832052224 |