Tsukiyoshi
Sanbagawa, Fujioka city, Gunma pref., Japan
Occurrence
Greenschist facies bedded manganese deposit
Chert-hosted bedded manganese deposit 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 is considered that it has been near the ground surface since early Paleocene (65 Ma). Metamorphic age was determined by K-Ar radiometric dating of muscovite.
Outcrop of piemontite schist of Sambagawa Metamorphic Rocks. This outcrop is composed of pale pink piemontite schist showing clear schistosity. The white vein at the right of the scale coin is a quartz vein concordant with the schistosity. Spessartine, Ardennite-(As), or Malachite were associated with these quartz veins.
Reported Minerals
- Piemontite
- Ardennite-(As)
- Spessartine
- Malachite
- Braunite
Mineral Assemblages
- Quartz - Piemontite - Spessartine - Ardennite-(As)
- Quartz - Braunite
- Quartz - Malachite
Localities
- Tone Mine (Braunite, High-P)
- Oyahana Bridge (Piemontite, High-P)
- Tsukiyoshi (Piemontite, High-P)
Related Occurrences
- Bedded Mn (Diagenesis)
- Bedded Mn (Low-T zeolite facies)
- Bedded Mn (High-T zeolite facies)
- Bedded Mn (Prehnite-Pumpellyite facies)
- Bedded Mn (Pumpellyite-Actinolite facies)
- Bedded Mn (Greenschist facies)
- Bedded Mn (Epidote-Amphibolite facies)
- Bedded Mn (Amphibolite facies)
- Bedded Mn (Albite-Epidote-hornfels facies)
- Bedded Mn (Hornblende-hornfels facies)
- Bedded Mn (Pyroxene-hornfels facies)