Dohira River
Minami-Nomaki, Shimonita city, Kanra county, Gunma pref., Japan
Occurrence
Alkaline metasomatic rocks of Wairakite-Albite zone
The late Miocene (6.0 Ma) andesitic dike intruded in the Motojyuku Formation of the same age. The Motojyuku Formation is composed of andesitic tuff breccia and andesitic-dacitic dikes filling the late Miocene-Pliocene Motojyuku Caldera. Ages of volcanic rocks were determined by K-Ar radiometric dating.
Outcrop of an andesitic dike intruded in the Motojyuku Formation. The grayish-green host is andesite dike with fine white spots of anorthite phenocrysts. The white to pale brown vein is composed of calcite and wairakite. The white parts are wairakite, and the pale brown parts are calcite. The wairakite crystals are up to 1/3 of the scale coin.
Reported Minerals
- Wairakite
- Calcite
Mineral Assemblages
- Wairakite - Calcite
Localities
- Dohira River (Dike, Wairakite)
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)