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.
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.
Localities
- Mount Tanigawa (Serpentinite, Anthophyllite)
- Katsunuma Rosekiyama (Serpentinite, Talc)
- Sasago (Serpentinite, Asbestos)
Related Occurrences
- Serpentinite (Hornblende-hornfels facies)
- Serpentinite (Greenschist facies)
- Serpentinite (Amphibolite facies)