Miyanohira

Occurrence

Low-temperature zeolite facies metamorphic rocks

Sr and Ba-bearing minerals in basaltic pyroclastics and sedimentary rocks associated with limestone in the Early Jurassic (175 Ma) Yusugawa Unit, a member of the Northern Chichibu accretionary complex. The Yusugawa unit has been subjected to Zeolite facies metamorphism as a low grade part of the Sambagawa metamorphic belt in the Late Cretaceous (100 Ma). The age of limestone is Carboniferous Late Pennsylvanian (300 Ma) to Permian Guadalupian (260 Ma). Ages of sedimentary rocks were determined by radiolarians, and metamorphic age by K-Ar or Ar-Ar radiometric dating of muscovite. The Ohirayama unit of the Southern Chichibu accretionary complex is distributed in this area but this locality was classified into the Yusugawa unit as the limestone is associated pyroclastics subjected to Zeolite facies metamorphism.

Reported Minerals

• Chabazite-Sr
• Harmotome
• Baryte
• Calcite

Mineral Assemblages

• Chabazite-Sr
• Harmotome