Momura
Momura, Nasu-Shiobara city, Tochigi pref., Japan
Synonym
Nasu-Roseki Mine, Kinomata River
Occurrence
Acidic metasomatic rocks of Pyrophyllite zone
B-rich pyrophyllite deposit formed by hydrothermal alteration of rhyolite and ryolitic tuff of the middle Miocene (15 Ma) Fukuwata Formation. The source of the hydrothermal fluid has not been specified but may have relation to Nasu Volcano, approximately 6 km apart from this locality. Ages of volcanic rocks were determined by stratigraphic works.
Outcrop of rhyolite or rhyolitic tuff of the Fukuwata Formation subjected to phyrophyllitization alteration. The white host is massive phyrophyllite. Bluish-gray spherules are radial aggregate of foitite and magnesiofoitite.
Outcrop of rhyolitic tuff of the Fukuwata Formation subjected to hematite-bearing hydrothermal alteration. The black parts are hematite associated with small amount of chlorite. The white host is altered ryolitic tuff, and its bedding planes are clear from the lower left to the lower right. Hematite beds are parallel to the bedding plane.
Reported Minerals
- Pyrite
- Hematite
- Rutile
- Dumortierite
- Foitite
- Magnesiofoitite
- Pyrophyllite
- Diaspore
- Apatite
- Sericite
Mineral Assemblages
- Pyrophyllite - Dumortierite
- Pyrophyllite - Foitite - Magnesiofoitite - Quartz - Pyrite
- Quartz - Hematite - Chlorite
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)