TrekGEO > Mineral Trail > Tokai region > Gifu pref. > Kurotani

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Okuhida-Onsengo-Nakao, Takayama city, Gifu pref., Japan


Hornblende-hornfels facies peridotite

Peridotite and serpentinite associated with the Cambrian-Devonian (500-400 Ma) sedimentary rocks of the Hida marginal belt. Peridotite and serpentinite contacts with the early Pleistocene (1.5 Ma) Takidani granodiorite, and have been subjected to contact metamorphism. The Takidani granodiorite is I-type (Magnetite-series). The peridotite-serpentinite blocks is possibly a part of ophiolite as banded structures were recognized in the block. These basements underlies the Nakao pyroclastic flow deposits associated with the late Holocene (2.3 ka) volcanic activity of the Yakedake lava dome. Ages of sedimentary rocks were determined by coral and trilobite fossils, granodiorite by K-Ar radiometric dating of hornblende and biotite, Rb-Sr radiometric dating of biotite, and fission track dating of zircon. The Takidani granodiorite is one of the youngest granitoids in the world.

Kurotani Valley

The dark green boulders at the right are serpentinite, ant the outcrop at the center is metamorphosed peridotite. Serpentinite and peridotite are parts of the Hida marginal belt. The thick light brown bed overlying serpentinite and peridotite is the Nakao pyroclastic flow deposits erupted from Mount Yakedake.

Reported Minerals

  • Magnetite
  • Magnesioferrite
  • Pentlandite
  • Valleriite
  • Tochilinite
  • Haapalaite
  • Troilite
  • Calcite
  • Dolomite
  • Ludwigite
  • Chalcedony
  • Moganite
  • Forsterite
  • Clinothulite
  • Tremolite
  • Actinolite
  • Talc
  • Brucite
  • Hydrotalcite
  • Hornesite?

Mineral Assemblages

  • Forsterite - Ludwigite - Pentlandite
  • Forsterite - Valleriite - Tochilinite - Haapalaite - Troilite
  • Serpentine - Brucite - Talc - Magnetite - Tremolite
  • Chalcedony - Moganite


  • The outcrop had been mined for talc.
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