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Yunosawa Mine

Ikarigaseki, Hirakawa city, Aomori pref., Japan


Moderate-T hydrothermal deposit

Moderate temperature hydrothermal deposit in welded tuff of the late Pliocene (3.5 Ma) Obirakiyama Tuff Formation. The Obirakiyama Tuff Formation is a member of the Yunosawa Caldera Complex, and is composed of continental rhyolite lava, welded tuff, and submarine pumice tuff. There is the early Pleistocene (2.3 Ma) Ikarigaseki Caldera in the Yunosawa Caldera. The deposit was formed by the volcanic activity of the Yunosawa Caldera or the Ikarigaseki Caldera. The type locality of Tsugaruite.

Yunosawa Mine

Outcrop of a moderate-T hydrothermal vein in rhyolitic welded tuff of the Obirakiyama Tuff Formation. The black vein is a hydrothermal vein composed of Pb sulfide such as jordanite. The surrounding pale gray host is rhyolitic welded tuff, and the host near the vein turn yellow by alteration. The vein is parallel to the ground surface, and is 5 m in length.

Reported Minerals

Mineral Assemblages

  • Jordanite - Baryte - Tsugaruite - Gratonite
  • Jordanite - Wurtzite


  • 1600's: Ag was mined by the domain of Tsugaru (Hirosaki).
  • Middle of Meiji era: Mined by Komaki mine.
  • Baryte was mined.
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