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ID 13917
Eprint ID
13917
FullText URL
Thumnail ESR_4_33.pdf 1.11 MB
Title Alternative
Ferroglaucophane schist from the Ohsa-yama srea, Okayama Prefecture, Japan
Author
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.
Keywords
ferroglaucophane
petrology
tectonic block
serpentinite
high P/T metamorphism,
Ohsa-yama
Sangun metamorphic terrane
Southwest Japan
Published Date
1997-09-20
Publication Title
Okayama University Earth Science Report
Publication Title Alternative
岡山大学地球科学研究報告
Volume
volume4
Issue
issue1
Publisher
岡山大学理学部地球科学教室
Publisher Alternative
Department of Earth Sciences Faculty of Science, Okayama University
Start Page
33
End Page
40
ISSN
1340-7414
NCID
AN10506284
Content Type
Departmental Bulletin Paper
language
日本語
Copyright Holders
岡山大学地球科学研究報告編集委員会
File Version
publisher
Refereed
False
Eprints Journal Name
esr