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Tsukuba Metamorphic Rocks

• Low P/T metamorphic rocks
• Protolith: Kasama Formation
• Deposition: Late Jurassic - Early Cretaceous
• Metamorphism: Paleocene (ca. 60 Ma, Radiometric age; 62 - 56 Ma, K-Ar)
• Correlation: Lower Wagakunisan Metamorphic Rocks, Ryoke Metamorphic Rocks
• Intruded by: Tsukuba Granite

• Metamorphic facies (Sillimanite zone): 0.32 - 0.35 GPa, 627 - 667 degrees Celsius
• Metamorphic facies (Sillimanite isograd): 0.3 - 0.35 GPa, 500 - 550 degrees Celsius
• Lithofacies (Protolith): Mudstone-dominant interbedded sandstone and mudstone
• Lithofacies (Protolith, Bottom): Sandstone, Sandstone-dominant interbedded sandstone and mudstone
• Lithofacies (Protolith, Minor): Gravel-bearing mudstone
• Lithofacies (Biotite zone): Biotite slate, Biotite schist
• Lithofacies (Sillimanite zone): K-feldspar-sillimanite-biotite schist

• Thickness (Apparent): 1,600 m or thicker

• Distribution: Hirasawa - Hojo, Tsukuba city, Ibaraki pref.; Negoya, Yasato, Ishioka city, Ibaraki pref.; Kakioka - Mount Ryujinsan - Tsukioka - Saikoin Temple, Ishioka city, Ibaraki pref.

• Takahashi et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.21-31 DOI
• Miyazaki et al. (1996) Geology of the Makabe District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 103p. (in Japanese with English abstract 4p.)