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Oki Metamorphic Rocks

Invalid synonym: Oki Gneisses

• Low P/T metamorphic rocks (580 - 630�x, 0.29 - 0.39 GPa)
• Protolith: Carboniferous (350 Ma�ȍ~: 200 Ma, Sm-Nd; 230 - 170 Ma, U-Pb; 240 - 180 Ma, SHRIMP; 350 - 300 Ma, CHIME)
• Metamorphism: Permian - Triassic (250 - 240 Ma; 250 Ma, CHIME; 236 Ma, SHRIMP)
• Cooling (500 degree C): Early Jurassic (199 - 192 Ma, Ar-Ar)
• Cooling (400 degree C): Middle Jurassic (168 - 167 Ma, Ar-Ar)
• Cooling (350 degree C): Late Jurassic (161 Ma, Rb-Sr)
• Cooling (240 degree C): Early Cretaceous (133.8 Ma, FT)
• Cropping out: late Oligocene - early Miocene
• Intruded by: Dogo-Minamidani Granite, Daimanjisanminami Basalt, Andesite dikes

• Metamorphic facies: Low temperature granulite, Amphibolite
• Lithofacies: Pelitic gneiss, Psammitic gneiss, Migmatitic gneiss, Gneissose granite, Amphibolite
• Lithofacies (Minor): Calcareous gneiss, Siliceous gneiss

• Distribution (Diameter): ca. 16 km
• Upper limit: Unconformity (Tokihariyama Formation, Kori Formation, Mukogaoka Formation, Daimanjisan Basalt, Minamidani Basalt, Saigo Basalt), Abut unconformity (Tsuzurao Formation)

• Distribution: Mount Tsuzuraoyama - Choshigawa river - Okugawa river - Fuse - Togogawa river - Arikigawa river - Nakadanigawa river, Okinoshima city, Oki county, Shimane pref.

• Yamauchi et al. (2009) Geology of the Saigo District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 118p. (in Japanese with English abstract 3p.)