Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration
Ca-Al-rich inclusions (CAIs) in three Antarctic CO chondrites, Yamato (Y)-81020,Y-82050 and Y-790992 have similar overall textures; most CAIs are rimmed or concentric objects. However, there are considerable differences in mineralogy; almost all of the CAIs in Y-81020 consist of primary high-tempera...
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Department of Earth and Planetary Sciences, Faculty of Science, Kobe University/Department of Earth and Planetary Sciences, Faculty of Science, Kobe University/Department of Earth and Planetary Sciences, Faculty of Science, Kobe University
1995
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ftnipr:oai:nipr.repo.nii.ac.jp:00004669 2023-05-15T13:49:02+02:00 Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration Kojima,Tomoko Yada,Satomi Tomeoka,Kazushige 1995-03 https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4669 http://id.nii.ac.jp/1291/00004669/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4669&item_no=1&attribute_id=18&file_no=1 en eng Department of Earth and Planetary Sciences, Faculty of Science, Kobe University/Department of Earth and Planetary Sciences, Faculty of Science, Kobe University/Department of Earth and Planetary Sciences, Faculty of Science, Kobe University National Institute of Polar Research https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4669 http://id.nii.ac.jp/1291/00004669/ AA10784627 Proceedings of the NIPR Symposium on Antarctic Meteorites, 8, 79-96(1995-03) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4669&item_no=1&attribute_id=18&file_no=1 Departmental Bulletin Paper P(論文) 1995 ftnipr 2023-02-04T20:06:16Z Ca-Al-rich inclusions (CAIs) in three Antarctic CO chondrites, Yamato (Y)-81020,Y-82050 and Y-790992 have similar overall textures; most CAIs are rimmed or concentric objects. However, there are considerable differences in mineralogy; almost all of the CAIs in Y-81020 consist of primary high-temperature phases such as melilite, anorthite, fassaite and spinel, while most of the CAIs in Y-82050 and Y-790992 contain major amounts of nepheline and lesser amounts of melilite and anorthite. CAIs in Y-790992 contain more nepheline than those in Y-82050. Small grains (<1μm in diameter) of troilite commonly coexist with nepheline. Spinel in Y-81020 is almost free of Fe, while those in Y-82050 and Y-790992 contain variable amounts of Fe (6 to 60 and 42 to 65 FeAl_2O_4 mol%, respectively). The texture of CAIs suggests that nepheline and troilite are secondary alteration products formed by replacing mainly melilite and anorthite. Spinel in CAIs and olivine in amoeboid olivine aggregates probably became enriched in Fe along with the alteration. As the alteration proceeded, fassaite and spinel were also replaced by nepheline, and perovskite was replaced by ilmenite and ulvospinel. Diopside remained unaltered even in the most heavily altered inclusions. Comparison of mineralogy before and after the alteration suggests that considerable amounts of Na, Fe, S and Cl were introduced into CAIs and some amounts of Ca and Mg were lost. Based on the amounts of nepheline, the relative degrees of alteration of CAIs are as follows : Y-81020<Y-82050<Y-790992. In order to compare the relationship between alteration of CAIs and thermal metamorphism on the parent body, metamorphic grades of the three CO chondrites were petrographically determined. The results indicate that the metamorphic grade increases in the same order as that of the degree of alteration of CAIs, i. e. Y-81020<Y-82050<Y-790992. Therefore, the results raise the possibility that alteration of CAIs may be related to thermal metamorphism which occurred on the ... Report Antarc* Antarctic National Institute of Polar Research Repository, Japan Antarctic Yamato ENVELOPE(35.583,35.583,-71.417,-71.417) |
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National Institute of Polar Research Repository, Japan |
op_collection_id |
ftnipr |
language |
English |
description |
Ca-Al-rich inclusions (CAIs) in three Antarctic CO chondrites, Yamato (Y)-81020,Y-82050 and Y-790992 have similar overall textures; most CAIs are rimmed or concentric objects. However, there are considerable differences in mineralogy; almost all of the CAIs in Y-81020 consist of primary high-temperature phases such as melilite, anorthite, fassaite and spinel, while most of the CAIs in Y-82050 and Y-790992 contain major amounts of nepheline and lesser amounts of melilite and anorthite. CAIs in Y-790992 contain more nepheline than those in Y-82050. Small grains (<1μm in diameter) of troilite commonly coexist with nepheline. Spinel in Y-81020 is almost free of Fe, while those in Y-82050 and Y-790992 contain variable amounts of Fe (6 to 60 and 42 to 65 FeAl_2O_4 mol%, respectively). The texture of CAIs suggests that nepheline and troilite are secondary alteration products formed by replacing mainly melilite and anorthite. Spinel in CAIs and olivine in amoeboid olivine aggregates probably became enriched in Fe along with the alteration. As the alteration proceeded, fassaite and spinel were also replaced by nepheline, and perovskite was replaced by ilmenite and ulvospinel. Diopside remained unaltered even in the most heavily altered inclusions. Comparison of mineralogy before and after the alteration suggests that considerable amounts of Na, Fe, S and Cl were introduced into CAIs and some amounts of Ca and Mg were lost. Based on the amounts of nepheline, the relative degrees of alteration of CAIs are as follows : Y-81020<Y-82050<Y-790992. In order to compare the relationship between alteration of CAIs and thermal metamorphism on the parent body, metamorphic grades of the three CO chondrites were petrographically determined. The results indicate that the metamorphic grade increases in the same order as that of the degree of alteration of CAIs, i. e. Y-81020<Y-82050<Y-790992. Therefore, the results raise the possibility that alteration of CAIs may be related to thermal metamorphism which occurred on the ... |
format |
Report |
author |
Kojima,Tomoko Yada,Satomi Tomeoka,Kazushige |
spellingShingle |
Kojima,Tomoko Yada,Satomi Tomeoka,Kazushige Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration |
author_facet |
Kojima,Tomoko Yada,Satomi Tomeoka,Kazushige |
author_sort |
Kojima,Tomoko |
title |
Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration |
title_short |
Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration |
title_full |
Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration |
title_fullStr |
Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration |
title_full_unstemmed |
Ca-Al-rich inclusions in three Antarctic CO3 chondrites, Yamato-81020, Yamato-82050 and Yamato-790992: Record of lowtemperature alteration |
title_sort |
ca-al-rich inclusions in three antarctic co3 chondrites, yamato-81020, yamato-82050 and yamato-790992: record of lowtemperature alteration |
publisher |
Department of Earth and Planetary Sciences, Faculty of Science, Kobe University/Department of Earth and Planetary Sciences, Faculty of Science, Kobe University/Department of Earth and Planetary Sciences, Faculty of Science, Kobe University |
publishDate |
1995 |
url |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4669 http://id.nii.ac.jp/1291/00004669/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4669&item_no=1&attribute_id=18&file_no=1 |
long_lat |
ENVELOPE(35.583,35.583,-71.417,-71.417) |
geographic |
Antarctic Yamato |
geographic_facet |
Antarctic Yamato |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4669 http://id.nii.ac.jp/1291/00004669/ AA10784627 Proceedings of the NIPR Symposium on Antarctic Meteorites, 8, 79-96(1995-03) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4669&item_no=1&attribute_id=18&file_no=1 |
_version_ |
1766250635410276352 |