Onna-Saka
Furuseki village, Kofu city, Yamanashi pref., Japan
Occurrence
Prehnite-Pumpellyite facies metamorphic rocks
The Takahagi basalt and dacitic tuff of the middle Miocene (14 Ma) Ashikawa formation, the Nishi-Yatsushiro group, subjected to Prehnite-Pumpellyite facies metamorphism by the Ashikawa quartz diorite in the middle Miocene (12 Ma). The Ashikawa quartz diorite is I-type (Magnetite-series). Approximately 5 km apart from quartz diorite, the heat source. Ages of sedimentary rocks were determined by microfossils, quartz diorite by K-Ar radiometric dating of biotite and hornblende.
Outcrop of basalt of the Takahagi Basalt subjected to Prehnite-Pumpellyite facies contact metamorphism. White spots are zeolite. Most of zeolite spots in this photograph are chabazite.
Reported Minerals
- Calcite
- Laumontite
- Prehnite
- Mesolite
- Analcime
- Wairakite
- Chabazite
- Epidote
- Pumpellyite
Mineral Assemblages
- Laumontite - Pumpellyite
- Quartz - Prehnite
- Calcite - Epidote
Localities
- Onna-Saka (Basalt)
- Hirayama (Basalt)
- Kouragahana (Pillow lava)
- Nakayashiki (Hyaloclastite)
- Iwakake (Hyaloclastite)
- Yadoriki (Tuff)
- Heguri (Sandstone, Gabbro)
- Mount Chiba (Datolite)
- Kami-Ochiai (Axinite-Datolite)
- Nyushima (Axinite-Datolite)
- Nanasawa (Celadonite)
- Oisawa (Celadonite)
- Mount Gozen (Celadonite)
Related Occurrences
- Albite-Epidote-hornfels facies
- Hornblende-hornfels facies
- Pyroxene-hornfels facies
- Sanidinite-hornfels facies