Complex fragmentation of Permo-Triassic and jurassic accreted terranes in the Chugoku region, southwest Japan and the formation of the Sangun metamorphic rocks

1987 ◽  
pp. 275-289 ◽  
Author(s):  
Teruo Watanabe ◽  
Takao Tokuoka ◽  
Takahito Naka
Keyword(s):  
Metamorphic Rocks ◽  
Southwest Japan ◽  
Accreted Terranes

scholarly journals Quartz Microstructures from the Sambagawa Metamorphic Rocks, Southwest Japan: Indicators of Deformation Conditions during Exhumation

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1038
Author(s):  
Toru Takeshita
Keyword(s):  
Large Scale ◽  
Boundary Migration ◽  
Metamorphic Rocks ◽  
Grain Boundary Migration ◽  
Structural Level ◽  
Southwest Japan ◽  
Physical Conditions ◽  
Subgrain Rotation ◽  
Garnet Zone ◽  
Quartz Grains

The Sambagawa metamorphic rocks in central Shikoku, southwest Japan consist of an inverted metamorphic sequence from the upper chlorite to oligoclase-biotite zones at the lower structural level (LSL), which is overlain by a normal metamorphic sequence consisting of the albite-biotite and garnet zones at the upper structural level (USL). These sequences form a large-scale recumbent fold called the Besshi nappe. To unravel the mechanism of recrystallization and physical conditions in quartz, and their relation to exhumation tectonics, microstructures of recrystallized quartz grains in quartz schist from the Asemi-Saruta-Dozan River traverse were analyzed. The recrystallized quartz grain size increases with increasing structural level from 40 µm in the upper chlorite zone to 160 µm in the garnet zone of the USL. Further, the mechanism of dynamic recrystallization of quartz changes from subgrain rotation to grain boundary migration with increasing structural level across the uppermost garnet zone of the LSL. From these data, the deformation temperatures in quartz schist are calculated to increase with increasing structural level within the range between 300 and 450 °C using paleopiezometers and experimental flow laws. It could be interpreted that a rapid cooling of the Besshi nappe from above is responsible for the deformation temperatures recorded in quartz schist.

scholarly journals Rb-Sr and K-Ar ages of the Higo metamorphic rocks and related granitic rocks, Southwest Japan.

1995 ◽  
Vol 101 (8) ◽  
pp. 615-620 ◽  
Author(s):  
Takashi Nakajima ◽  
Katsuhisa Nagakawa ◽  
Masaaki Obata ◽  
Shigeru Uchiumi
Keyword(s):  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Southwest Japan
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