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Yashu Mine

Funyu, Shioya city, Shioya county, Tochigi pref., Japan


Moderate-T hydrothermal deposit

Moderate temperature hydrothermal deposit associated with rhyolite dikes in the middle Miocene (15 Ma) Tamanyu welded tuff member of the Kazami-Yamada Formation. The Kazami-Yamada Formation uncomformably overlies the early Paleocene (65 Ma) Okunikko Rhyolites. The Tamanyu welded tuff member was formed under shallow marine environment, and uncomformably underlies the Oya Formation. Ages were determined by microfossils and fission track dating of zircon.

Yashu Mine

Outcrop of amethyst vein in welded tuff of the Tamanyu Welded Tuff Member, Kazami-Yamada Formation. The white host with purple patches is welded tuff. The purple vein is amethyst, and crystals are vertical to the vein walls.

Reported Minerals

  • Chalcopyrite
  • Hematite
  • Malachite
  • Covellite
  • Amethyst

Mineral Assemblages

  • Chalcopyrite - Covellite
  • Hematite - Quartz
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