ID | 13917 |
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Sort Key | 3
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Title Alternative | Ferroglaucophane schist from the Ohsa-yama srea, Okayama Prefecture, Japan
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Abstract | A ferroglaucophane schist occurs in fault contact with serpentinites at the Ohsa-yama area, Southwest Japan. It consists of albite, ferroglaucophane and actinolite with small amounts of stilpnomelane, sphene, apatite and K-feldspar. Petrological studies reveal that the schist was originally igneous rock of felsic or intermediate composition and has suffered two stages of metamorphism : ferroglaucophane has been formed at the first stage and actinolite at the second stage. In a basic schist from the same outcrop that the ferroglaucophane schist occurs, tremolitic amphibole instead of alkali amphibole has been formed along with chlorite, phengite and albite. Such a difference in mineral association between the schists is ascribed to a difference in whole rock composition, particu-larly in Fe/Mg ratio.
Some of the schists from th Ohsa-yama area characteristically contain glaucophane or ferroglaucophane and have low Fe2O3/FeO ratios, forming a striking contrast to the crossite schists that commonly occur in the so-called "Sangun metamorphic terrane". These facts suggest that the alkali amphiboles of the Ohsa-yama schists were formed under higher P/T and more reducing conditions than those of the regional metamrphic rocks. On the other hand, development of the second-stage actinolite in the ferroglaucophane schist is consistent with the meta-morphic parageneses of greenschists from adjacent areas. Consequently the ferroglaucophane schist is considered one of the tectonic blocks that were captured by mobile serpentinites and have suffered the regional metamor-phism after the emplacement of the serpentinites into the present geologic position.
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Keywords | ferroglaucophane
petrology
tectonic block
serpentinite
high P/T metamorphism,
Ohsa-yama
Sangun metamorphic terrane
Southwest Japan
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Publication Title |
Okayama University Earth Science Report
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Published Date | 1997-09-20
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Volume | volume4
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Issue | issue1
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Publisher | 岡山大学理学部地球科学教室
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Publisher Alternative | Department of Earth Sciences Faculty of Science, Okayama University
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Start Page | 33
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End Page | 40
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ISSN | 1340-7414
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NCID | AN10506284
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Content Type |
Departmental Bulletin Paper
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OAI-PMH Set |
岡山大学
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language |
Japanese
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Copyright Holders | 岡山大学地球科学研究報告編集委員会
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File Version | publisher
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NAID | |
Eprints Journal Name | esr
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