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ID 13941
Eprint ID
13941
フルテキストURL
Thumnail ESR_2_23.pdf 2.34 MB
タイトル(別表記)
A suggestion on the origin of biotite gneisses of the Ryoke belt in the Seto Inland Sea (Seto-nai-kai) region : Some biotite gneisses were derived from a different geologic unit to the Kuga froup
著者
濡木 輝一 元岡山大学理学部地学教室
抄録
The Kuga group is a Jurassic accretional complex that has been believed by many workers to be a unique geologic unit transformed into the Ryoke gneisses in the Seto Inland Sea region. I will now suggest the presence of a different geologic unti in addition to the Kuga group. Most of the biotite gneisses found at the Iwakuni-Yanai area are probably derived from rocks of the Kuga group, but the rest biotite gneisses that occur in the Murotu Peninsula, the Yashiro-jima, the E-no-shima, and the other several islands in the Seto Inland Sea region were derived from a un-known and a different geologic unit to the Kuga froup. Some pieces of evidence proving the distinct origin of the latter biotite gneisses are: (1) the biotite gneisses commonly occur as small to large fusiform bodies generally enclosed in the older Ryoke granite or as large masses contacting only with the older Ryoke granite; (2) tight folds with parallel axial surfaces are very common, and dupli-cated fold systems are found in many localities; (3) microtextures of some minerals, e.g. garnet and K-feldspar, often suggest a plural metamorphic history of the gneisses (Nuraki et al., 1982a; Miyashita % Komatsu,1993); and (4) the sillimanite zone (Ikeda,1991 : Okudaira et al.,1993) is only a metamorphic zone that can be found. The sillimanite zone is interpreted to be excluded from the progressive metamorphism in the Iwakauni-Yanai area (Wallits et al.,1992). Biotite gneisses of the sillimanite zone are found here and there and show no zonal arrangement of distribu-tion in the Ryoke belt. The estimated metamorphic temperature and pressures for the biotite gneisses of the silliman-ite zone are 530-710℃ and 2-4kb respectively, both of which are lower than of the peak metamorphism, estimated as 550-820℃ and 5-6kb, at the Iwakuni- Yanai area.
キーワード
Kuga group
Ryoke belt
biotie gneisses
Sillimanite Zone
Iwakuni-Yanai area
発行日
1995-09-20
出版物タイトル
Okayama University Earth Science Report
出版物タイトル(別表記)
岡山大学地球科学研究報告
2巻
1号
出版者
岡山大学理学部地球科学教室
出版者(別表記)
Department of Earth Sciences Faculty of Science, Okayama University
開始ページ
23
終了ページ
54
ISSN
1340-7414
NCID
AN10506284
資料タイプ
紀要論文
言語
Japanese
OAI-PMH Set
岡山大学
著作権者
岡山大学地球科学研究報告編集委員会
論文のバージョン
publisher
査読
無し
Sort Key
3
Eprints Journal Name
esr