TrekGEO > Mineral Trail > Koshinetsu region > Yamanashi pref. > Katsunuma Rosekiyama

Japanese page

Katsunuma Rosekiyama

Katsunuma, Koshu city, Yamanashi pref., Japan

Occurrence

Hornblende-hornfels facies serpentinite

Serpentinite subjected to Albite-Epidote-hornfels facies contact metamorphism by the Tonoki body of the late Miocene (10 Ma) Tokuwa Granite. The serpentinite is a block in the early Oligocene (30 Ma) Sasago Unit of the Sagamiko Group, a member of the Shimanto accretionary complex. The Tonoki body is the S-type (Ilmenite-series) margin of the I-type (Magnetite-series) Tokuwa Granite. The S-type (Ilmenite-series) margin was formed by reduction reation of granite magma with surrounding pelitic rocks. The origin of this serpentinite block is considered as sedimentary serpentinite from serpentinite seamounts at the fore-arc slope. Ages of sedimentary rocks were determined by radiolarians, and granite age by K-Ar radiometric dating of biotite and whole rock.

Katsunuma Rosekiyama

Outcrop of talc-actinolite rock in the Sasago Unit. This outcrop is mostly composed of shale with clear bedding planes. The massive talc-actinolite rock is at the right of the hammer of the wooden grip at the right end of this photograph. The talc-actinolite rock contacts harmonically with the bedding planes of the host shale. The origin of this talc-actinolite rock is interpreted as a serpentinite block subjected to contact metamorphosed by granite.

Reported Minerals

  • Talc
  • Actinolite
  • Magnesiohornblende

Mineral Assemblages

  • Talc - Actinolite - Magnesiohornblende

History

  • 1949: Mining talc was started for baby powder.
  • 1952: Closed.
Copyright (c) 2022 NariNari, All Rights Reserved.