Yoka
Futomi, Kamogawa city, Chiba pref., Japan
Occurrence
High-temperature zeolite facies metamorphic rocks
Zeolites produced in pockets of tholeiitic to alkali basaltic pillow lava and hyaloclastite of the early Miocene (20 Ma) Mineoka Group, an accretionary complex corresponding to the Setogawa Group of the Shimanto accretionary complex. Tholeiitic to alkali basalt is middle Eocene (47-38 Ma). Ages of sediments were determined by radiolarians, basalt by microfossils.
Reported Minerals
Mineral Assemblages
- Natrolite - Thomsonite
- Analcime
- Gabbro(Host) - Magnesiohornblende
Localities
- Nakadomari (Analcime)
- Naka-Kawabe (Heulandite)
- Kaneyama (Heulandite)
- Yoka (Natrolite)
- Nomaki (Analcime)
Related Occurrences
- Albite-Epidote-hornfels facies
- Hornblende-hornfels facies
- Pyroxene-hornfels facies
- Sanidinite-hornfels facies