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language
eng
Author
Kabir, Md. Fazle
Matsuura, Hiroaki
Kuraya, Itsuki
Description
The Tonaru metagabbro mass occurs as a large lenticular body in the highest-grade (oligoclase-biotite zone) portions of the Sambagawa schists in the Besshi district. The Tonaru mass consists of diopside amphibolite and garnet-epidote amphibolite accompanied by small amounts of eclogite and marble. Kyanite-garnet amphibolites from the Tonaru metagabbro mass are composed of amphibole (calcic-amphibole; magnesiohornblende, actinolite, tremolite and tschermakite), zoisite, kyanite, garnet, phengite, paragonite, margarite, chlorite, quartz and pyrite. Amphiboles in the kyanite-garnet amphibolite exhibit three different modes of occurrence (Amp1-3). Amphiboles (Amp1) occur as inclusions in the porphyroblastic garnets are calcic in compositions (magnesiohornblende, actinolite and tremolite). Some are zoned, with magnesiohornblende core and actinolite / tremolite rim. Amphiboles (Amp2) in the matrix are mostly magnesiohornblende, and are zoned with magnesiohornblende core and actinolite / tschermakite rim. Amphiboles (Amp3) filling the fractures of the garnets are magnesiohornblende and tschermakite, and display a compositional zoning with magnesiohornblende core and tschermakite rim. The metamorphic evolution of the kyanite-garnet amphibolite from the Tonaru metagabbro mass is probably divided into two metamorphic events. The amphiboles (Amp1, 2) represent prograde metamorphism from the epidote-blueschist facies to the peak eclogite facies metamorphism. The actinolite rim of both occurrences suggests a retrograde metamorphism after the peak conditions. Amphiboles (Amp3) occur in fractures of the porphyroblastic garnets, and provide evidence of the second high-P metamorphic event. This metamorphic event is similar to that of the prograde Sambagawa metamorphism of the oligoclase-biotite zone.
Subject
Sambagawa (Sanbagawa) metamorphic belt
Tonaru metagabbro mass
amphibole
high-Mg garnet
kyanite
Journal Title
島根大学地球資源環境学研究報告
Volume
34
Start Page
31
End Page
39
ISSN
13439774
Published Date
2016-03-05
NCID
AA11455176
DOI(SelfDOI)
Publisher
島根大学大学院総合理工学研究科地球資源環境学教室
NII Type
Departmental Bulletin Paper
Format
PDF
Text Version
出版社版
OAI-PMH Set
Interdisciplinary Graduate School of Science and Engineering
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