TrekGEO > Mineral Trail > Kanto region > Gunma pref. > Yashio Mine

Japanese page

Yashio Mine

Onishi, Fujioka city, Gunma pref., Japan


Greenschist facies serpentinite

Cr deposit associated with serpentinite in the Late Jurassic (150 Ma) to Early Cretaceous (130 Ma) accretionary complex subjected to Greenschist facies metamorphism as a part of the high-P Sambagawa metamorphic belt in the Late Cretaceous (70 Ma). The Sambagawa metamorphic rocks are considered that it has been near the ground surface since early Paleocene (65 Ma). The origin of this serpentinite block is considered as sedimentary serpentinite mélange from serpentinite seamounts at the fore-arc slope. Metamorphic age was determined by K-Ar radiometric dating of muscovite.

Reported Minerals

Mineral Assemblages

  • Serpentine - Chromite - Kämmererite
  • Serpentine - Coalingite
  • Serpentine - Hydromagnesite - Aragonite
Copyright (c) 2015 NariNari, All Rights Reserved.