TrekGEO > Mineral Trail > Kanto region > Kanagawa pref. > Hitodo

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Minasegawa, Yamakita city, Ashigara-Kami county, Kanagawa pref., Japan


Hydrothermal deposit along fault

Minerals associated with the Kannawa reverse fault at the boundary between tuff-tuff breccia of the middle Miocene (15 Ma) Hontanikawa Formation, Oyama Subgroup, Tanzawa group, and conglomerate of the early Pleistocene (1.5 Ma) Seto Formation, Ashigara Group. The sedimentary environment of the Seto Formation is submarine fan delta. The Tanzawa Group is considered as the accreted Izu oceanic arc collided with the Honshu island arc, and the Ashigara Group as trough-fill sediments. This fault has been interpreted as the boundary between the Eurasian plate of the Honshu island arc and the Philippine Sea plate. The age of sedimentary rocks were determined by microfossils.


Outcrop of the Kannawa reverse fault. The dark gray cliff at the center is tuff of the Hontanikawa Formation, Oyama Subgroup, Tanzawa Group. The flat outcrop at the river bed is boulder conglomerate of the Seto Formation, Ashigara Group. The fault is at the talus cone between them.

Reported Minerals

  • Glauconite
  • Hematite
  • Magnetite
  • Aluminoceladonite

Mineral Assemblages

  • Hematite - Glauconite
  • Magnetite
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