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Minamiite-Alunite zone

Chemical Process (Alteration) - Open system under ground (Acidic metasomatism)


High temperature subzone of Kaolinite zone, Alunite zone (Middle temperature), Argillized zone (Dickite, Nacrite)

Index Minerals

Natroalunite-2c (Minamiite)

Required Geological Setting

Metasomatic rocks (Acidic)


Metasomatic zone formed by acidic hydrothermal fluid of 220-250 degree associated with Rhyolitic magma activities. This alteration is a part of alunitization and argillization. Protoliths are felsic rocks. Minamiite-Alunite zone may be associated with Moderate-T hydrothermal deposits.

Minamiite-Alunite zone

Distribution of Minamiite-Alunite zones described in this site. Yellow lines are volcanic fronts.

Change of mineral assemblages

  • [ Extinct ] Kaolinite, Smectite/Illite, Smectite/Chlorite, Gypsum
  • [ Appear ] Natroalunite-2c (Minamiite), Dickite, Nacrite, Rutile, Illite, Chlorite

Mineral Assemblages

  • Alunite, Natroalunite-2c (Minamiite), Quartz, Pyrite, Dickite, Nacrite, Rutile, Illite, Chlorite, (Anhydrite, Diaspore, Zunyite, Topaz)


  • Sessho creek (Vein type)
  • Funabara mountain pass (Replaced type)
  • Ukusu Mine (Replaced type)

Related Occurrences

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