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タイトルヨミ
オキ ドウゴ マッキ チュウシンセイ ツズラオソウ カドウカクレキガン ト ソメンガン ガンペンチュウ ノ アルカリ チョウセキ K AR ネンダイ
タイトル別表記
Geology and petrography of vent breccias of the Latest Miocene Tsuzurao Formation, and alkali feldspar K-Ar age from a trachyte essential fragment, Oki-Dogo Island, SW Japan
ファイル
言語
日本語
著者
澤田 順弘
當銘 あかね
北川 博也
小林 伸治
今岡 照喜
板谷 徹丸
内容記述(抄録等)
 The Tsuzurao Formation is distributed in the northeastern part of Oki-Dogo Island in an area about 4.5 km E-W by 6 km N-S. It unconformably covers the Oki metamorphic rocks and the Tokibariyama Formation(Figs. 1 and 2). The Tsuzurao Formation consists mainly of rhyolitic pyroclastic flow deposits, with a small volume of rhyolitic air fall deposits and associated rhyolite lavas, dikes, and trachyte essential fragments and xenoliths. Vent breccias and feeder dikes are distributed in the eastern and southwestern parts of the Tsuzurao Formation(Figs. 2 and 3). Vent breccias are intruded into the basement as a fissure vent 1500 m long and 400 m wide. The vent breccias are massive, and are composed of rhyolite and trachyte essential fragments and accidental fragments derived from the basement. The vent breccia matrix consists of rhyolitic pyroclastic material. Many trachyte fragments are elongated, and some are enclosed by rhyolite fragments or are mixed with them. Trachyte fragments consist of alkali feldspar, fayalite, hedenbergite, alkali amphiboles(arfvedsonite, riebeckite), magnetite, and apatite. Rhyolite is composed of alkali feldspar, quartz, alkali amphiboles(arfvedsonite, riebeckite), annite, magnetite, apatite. The alkali feldspars in rhyolite are albite(An1.8-1.7 Ab90.4-93.0 Or7.8-5.3)and anorthoclase - sanidine(An0.0-2.0 Ab34.6-58.2 Or41.8-86.0). In trachyte they are anorthoclase - sanidine(An3.8-6.4 Ab36.0-50.9 Or41.5-52.0 and An0.0 Ab46.8 Or53.2).
 Alkali feldspar from a trachyte essential fragment in the vent breccia yields a K-Ar age of 5.45±0.17 Ma. This is similar to the radiometric ages of the Omosu Formation and Hei Trachyte Group in Oki-Dogo Island.
掲載誌名
島根大学地球資源環境学研究報告
27
開始ページ
11
終了ページ
20
ISSN
13439774
発行日
2008-12-25
NCID
AA11455176
出版者
島根大学総合理工学部地球資源環境学教室
出版者別表記
Department of Geoscience, Interdisciplinary Faculty of Science and Engineering, Shimane University
資料タイプ
紀要論文
部局
(旧組織)大学院総合理工学研究科 地球資源環境学領域
備考
12-14,16+ / 1993+
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