Hongo Mine
Kaize, Sakuho city, Minami-Saku county, Nagano pref., Japan
Occurrence
Acidic metasomatic rocks of Pyrophyllite zone
Hydrothermal deposit associated with the late Miocene (11 Ma) pyrophyllitization formed by hydrothermal alteration by the middle Miocene (14 Ma) Moraisan Granodiorite. The Moraisan Granodiorite is I-type (Magnetite-series). The basement of the deposit is the early Miocene (17 Ma) Uchiyama Formation and the Early Jurassic (175 Ma) Northern Chichibu accretionary complex. The Uchiyama Foramtion unconformably overlies the Northern Chichibu accretionary complex. The sediments of the Northern Chichibu accretionary complex in this locality is probably the Sumaizuku Unit or the Kamiyoshida Unit. Approximately 2 km apart from the Moraisan Granodiorite, the heat source. Ages of sedimentary rocks were determined by radiolarians and microfossils, granodiorite by K-Ar radiometric dating of biotite, and pyrophyllitization by K-Ar radiometric dating of whole rock.
A very old adit of Hongo Mine.
Reported Minerals
Mineral Assemblages
- Quartz(Host) - Enargite
- Quartz(Host) - Pyrite - Zunyite
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)