ID | 13949 |
JaLCDOI | |
Sort Key | 8
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タイトル(別表記) | Rb-Sr age of K-rich LL-chondrite Yamato-74442
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フルテキストURL | |
著者 |
西谷 七代
岡山大学理学部地球科学科
加々美 寛雄
岡山大学地球内部研究センター
中村 昇
神戸大学理学部地球科学科
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抄録 | Yamato-74442, a brecciated LL-group chondrite, consists of fragments with igeous texture, chondrules, mineral fragments, and host. The fragments involve K-rich fragments as well as normal ones. Typically, both fragments consist mainly of euhedral porphyritic olivines and a few orthopyroxenes in a glassy grundmass. EPMA analyses for these fragments indicate that olivines and orthoptroxenes have a range of Fe/(Fe+Mg) ratio of 27.19~31.33 and 20.10~26.91 mol%, respectively. There is no significant difference in these rations between K-rich (Na2O/K2O<1) and normal framents. The K2O contents of groundmass for K-rich fragments range from 0.51 to 4.89 wt% and that of the normal fragments is 0.38~090 wt%. K2O contents of groundmass vary from fragment to fragment but are rather homegeneous in a single fragment.
Rb-Sr isotopic determination on eighteen K-rich fragments (1.5 to 9.5mg in weight) gave an internal isochron age of 4.514±0.022 (2σ) Ga (λ87Rb=1.42×10-11y-1) and initial 87Sr/86Sr ratio of 0.7016±0.0024. This age is somewhat old compared with a whole rock isochron age of LL chondrites (4.493±0.18 Ga; Minster and Allegre, 1981). From a comoarison of the present result with others so far reported, it is inferred that the alkali differentiation as observed in Yamato-74442 probably occurred prior to or during a process of accumulation from LL chondrite parent material in the early solar nebula.
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キーワード | LL-chondrite
Rb-Sr age
Sr isotope
K-rich fragment
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出版物タイトル |
Okayama University Earth Science Report
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発行日 | 1995-09-20
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巻 | 2巻
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号 | 1号
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出版者 | 岡山大学理学部地球科学教室
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出版者(別表記) | Department of Earth Sciences Faculty of Science, Okayama University
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開始ページ | 91
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終了ページ | 102
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ISSN | 1340-7414
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NCID | AN10506284
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資料タイプ |
紀要論文
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OAI-PMH Set |
岡山大学
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言語 |
日本語
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著作権者 | 岡山大学地球科学研究報告編集委員会
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論文のバージョン | publisher
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NAID | |
Eprints Journal Name | esr
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