TrekGEO > Mineral Trail > Koshinetsu region > Nagano pref. > Iri-Karuizawa

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Iri-Karuisawa, Soehi, Sanada village, Ueda city, Nagano pref., Japan


Neutral metasomatic rocks of Illite-Chlorite zone

Epidote Group minerals formed by hydrothermal alteration by the late Miocene (9 Ma) Sugadaira Quartz Diorite of dacitic-rhyolitic tuff, dacite, and rhyolite of the Takeshi Member in the early Miocene (17 Ma) Uchiyama Formation. The Sugadaira Quartz Diorite is I-type (Magnetite-series). Approximately 5 km apart from the Sugadaira Quartz Diorite, the heat source. Ages of sedimentary rocks were determined by microfossils, quartz diorite by K-Ar radiometric dating of whole rock.

Reported Minerals

  • Thulite
  • Epidote
  • Quartz
  • Beta quartz

Mineral Assemblages

  • Thulite
  • Epidote - Quartz
  • Rhyolite(Host) - Beta quartz

Details of the mine

Production of thulite has been known since 1900's.


Related Occurrences

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