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Title Transcription
オキ ドウゴ チュウシンセイグン ルイソウ ニ ミイダサレタ デイガンチュウ ノ ホウフッセキ コンクリーション
Title Alternative (English)
Analcime concretion found in mudstone of Miocene Koori Formation in Dogo Oki Island, Japan
File
language
jpn
Author
Suzuki, Noriyuki
Oosaka, Osamu
Akasaka, Masahide
Description
An analcime concretion was found in mudstone of Miocene Koori Formation in Dogo Oki Islands, Japan. The Miocene Koori Formation was mainly formed in a non-marine depositional environment. The analcime concretion consists of distinctly separated outer crust and inner core. The soft inner core is mainly composed of kaolinite, well crystallized metahalloysite (halloysite 7Å), and montmorillonite. While analcime with some detrital quartz and authigenic pyrite are major constituents of hard outer crust. No carbonate minerals are present in the analcime concretion. Porosity of the inner core was evaluated as about 50 to 60%, suggesting that this concretion was formed in the very early stage of diagenesis. Kaolin minerals characterized by low Si/Al in the inner core indicate that the inner core was formed in a relatively acidic and fresh pore water. The abundant analcime and pyrite in the outer crust show that the outer crust was formed in a Na^+ and SO_4^(2-) rich saline pore water. Analcime, however, can not be considered to be the primary mineral, since its formation temperature is generally more that 80℃. Clinoptilolite can be a candidate as a possible primary mineral formed from saline pore water rich in dissolved silica derived from felsic pyroclastic rocks which are commonly observed in this stratigraphic horizon. No evidence of hydrothermal alteration is observed. The occurrence of analcime concretion is possibly concemed with that the marine water invaded the fresh water depositional environment in late Koori Formation deposition.
Journal Title
Geological reports of Shimane University
Volume
10
Start Page
89
End Page
95
ISSN
0287816X
Published Date
1991-07-30
NCID
AN00054980
Publisher
島根大学理学部地質学教室
Publisher Aalternative
Department of Geology, Faculty of Science, Shimane University
NII Type
Departmental Bulletin Paper
Format
PDF
Text Version
出版社版
OAI-PMH Set
Faculty of Science and Engineering
Remark
1-11 / 1982-1992
島田昱郎教授退官記念論誌集
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