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Mikawa Mine

Araya, Aga city, Higashi-Kambara county, Niigata pref., Japan


Otani Mine


Moderate-T hydrothermal deposit

Moderate temperature hydrothermal deposit associated with rhyolite of the early Miocene (21 Ma) Mikawa Formation. The Mikawa Formation is composed of andesite-dacite-rhyolite lava and those pyroclastic rocks formed in the continental circumstance. The Mikawa Formation unconformably overlies Tamba-Mino-Ashio accretionary complex and the middle Paleocene (60 Ma) granite. The Tamba-Mino-Ashio accretionary complex in this area is probably the Early Jurassic (180 Ma) Funafuseyama Unit by lithology. The Mikawa Formation unconformably underlies the middle Miocene (14 Ma) Tsugawa Formation. Ages of sedimentary rocks were determined by microfossils.

Mikawa Mine

Outcrop of rhyolite of the Mikawa Formation associated with hydrothermal sulfide veins aligned in en échelon arrangement. The brown host is altered rhyolite, and vertical light gray veins are lodes. A single platy vein was cut by small vertical faults. Veins are filled with clay by argillization.

Reported Minerals

Mineral Assemblages

  • Quartz(Gangue) - Chalcopyrite
  • Quartz(Gangue) - Sphalerite - Smithsonite
  • Siderite - Dolomite
  • Quartz(Gangue) - Baryte - Siderite
  • Galena - Anglesite


  • 1534: Mosuke discovered the deposit, and started to mine Au.
  • 1891: Ag was mined under the name of Otani mine.
  • 1906: Started to mine Cu.
  • 1932: Renamed to Mikawa mine.
  • 1946: Started to mine Pb and Zn.
  • 1956: The concentrator was built.
  • 1961: Closed.
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