島根県江津市東部に分布する波積南テクトニック・メランジ : 地質・岩石・構造

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The Hazumi-minami tectonic melange, which is a fault-bounded and isolated unit of 3×6 km of the Sangun metamorphic rocks in the eastern Goutsu City, central Shimane Prefecture, Japan sea side of SW Japan, is composed of scattered blocks of mafic schist with comparatively wide range of metamorphic grade and matrices of pelitic schist and serpentinite. Blocks of mafic schist vary in their shape and size ranging from a few ten centimeters to several hundred meters. Thin sheared zones are commonly observed between blocks of mafic schist and matrix of pelitic schist. The metamorphic facies series observed in the rocks and matrices is comparable to that of the Sanbagawa metamorphic belt and the grade ranges from the low temperature part of the chlorite zone to the low temperature part of the biotite zone. The higher grade rocks such as barroisite schist and garnet bearing pelitic schist tend to distribute in and around a serpentinite body. On the other hand, low grade rocks such as lawsonite-bearing pelitic schist or winchite-bearing mafic schist are found in the southern part. However, mixing of varing metamorphic grade rocks is essential in the Hazumi-minami tecnotic melange. Diapir of serpentinite and flow of pelitic schists in the ductile shear zone related to underplating process, suggested by sheath fold of siliceous schist, contribute to the early stage of the formation of melange. Brittle deformation of the later stage is also significant for the melange-formation and suggests change of shear direction during the uplift of the Hazumi-minami tectonic melange. This whole disturbance seems to have occurred in Jurassic time judging from K-Ar ages for the metamorphic rocks.
日本地質学会の論文
1989-04-26

島根県江津市東部に分布する波積南テクトニック・メランジ : 地質・岩石・構造

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