Kyonosawa
Mitomi-Kamikamaguchi, Yamanashi city, Yamanashi pref., Japan
Occurrence
Acidic metasomatic rocks of Pyrophyllite zone
B-rich pyrophyllite deposit formed by hydrothermal alteration along the Sekisuiji fracture zone in the Konarayama Rhyolites (Konarayama volcanic rocks), a member of the early Pliocene (5.0 Ma) Higashi-Yamanashi Caldera. The Konarayama Rhyolites are composed of ryolitic-andesitic welded tuff, volcanic breccia, lava. The konarayama volcanic rocks unconformably overlies the Hirose granodiorite, and unconformably underlies the Yamaguchi pumice tuff of the Mizugamori volcanic rocks. The Sekisuiji fracture zone is a fault related to the Higashi-Yamanashi Caldera. The hydrothermal alteration was caused by the activity of the early Pleistocene (2.0 Ma) Mizugamori volcanic rocks. Ages of volcanic rocks were determined by K-Ar radiometric dating of whole rock and biotite. The type locality of magnesiofoitite.
Outcrop of andesite or dacite of the Konarayama Rhyolites subjected to pyrophyllitization alteration. White part is porous quartz, and dark green parts are veins of magnesiofoitite. Blue dumortierite is also included as spots.
Reported Minerals
- Dumortierite
- Magnesiofoitite
- Pyrite
- Sr-Natroalunite
- Rutile
- Muscovite
Mineral Assemblages
- Quartz - Magnesiofoitite - Dumortierite - Muscovite
- Quartz - Dumortierite
- Andesite/Dacite(Host) - Pyrite
Localities
- Momura (B rich)
- Kyonosawa (B rich)
- Shima Mine (B rich)
- Hinomaru-Nako Mine (P rich)
- Yoji Mine (Al,F rich)
- Shin-yo Mine (Al,F rich)
- Mount Kawate (Zunyite)
- Mount Shoko (Al rich)
- Nekoyama (Al rich)
- Mitsuishi (Al rich)
- Isshiki Mine (Al rich)
- Toho Mine (Al rich)
- Hongo Mine (Sulfide deposit)
- Masutomi Mine (Sulfide deposit)
Related Occurrences
- Halloysite zone (Alunite zone, Argillized zone)
- Kaolinite zone (Alunite zone, Argillized zone)
- Minamiite-Alunite zone (Alunite zone)
- Pyrophyllite zone
- Smectite zone (Argillized zone)
- Interstratified mineral zone (Argillized zone)
- Illite-Chlorite zone (Propylite zone)
- Epidote-Actinolite zone
- Stilbite-Mordenite zone (Zeolite zone)
- Heulandite-Analcime zone (Zeolite zone)
- Laumontite-Albite zone (Zeolite z., Propylite z.)
- Wairakite-Albite zone (Zeolite zone)