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Nakauri Mine

Nakauri, Shinshiro city, Aichi pref., Japan

Occurrence

Serpentinization

Cu-Fe-Ni deposit in serpentinite of the Mikabu Greenrocks associated with the Middle Jurassic (170 Ma) Kamiyoshida unit or the Early Cretaceous (120 Ma) Kashiwagi unit, members of the Northern Chichibu accretionary complex. The Mikabu Greenrocks is probably a part of the Middle Jurassic to Early Cretaceous accretionary complex cropped out between the Nothern Chichibu acretional complex and the Sambagawa metamorphic rocks. The Mikabu Greenrocks are composed of Carboniferous to Triassic Basalt lava, basaltic tuff breccia, basaltic tuff, and gabbro, and has been subjected to Pumpellyite-Actinolite facies metamorphism as a low grade part of the Sambagawa metamorphic belt in the Late Cretaceous (100 Ma). The protolith of the Mikabu Greenrocks is considered as mafic volcanic rocks and ultramafic rocks of oceanic plateaux and seamounts. Serpentinite is possibly serpentinite seamount and/or sedimentary serpentinite at the fore-arc slope. Ages of sedimentary rocks were determined by conodont, and metamorphic age by K-Ar or Ar-Ar radiometric dating of muscovite. The type locality of nakauriite.

Nakauri mine

Outcrop of Cu-Fe-Ni deposit in serpentinite of the Mikabu Greenstones. The pale blue crust on the surface is nakauriite, and the white crust is artinite. The dark green basement is serpentinite, the host of the deposit.

Nakauri mine

Outcrop of Cu-Fe-Ni deposit in serpentinite of the Mikabu Greenstones. The bright green parts are malachite and brochantite. The dark green parts are the host serpentinite. The brown parts are limonite crusts. This outcrop is approximately 1.0 m apart from the above outcrop, and no artinite and nakauriite was observed.

Reported Minerals

  • Copper
  • Magnetite
  • Cuprite
  • Tenorite
  • Chalcocite
  • Djurleite
  • Bornite
  • Heazlewoodite
  • Cobalt-pentlandite
  • Malachite
  • Brochantite
  • Hydromagnesite
  • Artinite
  • Aragonite
  • Nakauriite
  • Antigorite

Mineral Assemblages

  • Serpentine - Magnetite - Hydromagnesite - Artinite
  • Serpentine - Copper - Chalcocite - Djurleite - Malachite - Brochantite
  • Serpentine - Heazlewoodite - Cobalt-pentlandite
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