Nakano-Tsuchiyama Mine
Gongendo, Moroyama city, Iruma county, Saitama pref., Japan
Occurrence
Oxidation zone of Pumpellyite-Aclinolite facies bedded manganese deposit
Manganese dioxide deposit formed by oxidation of chert-hosted bedded manganese deposit in a chert block of the Early Cretaceous (130 Ma) Kashiwagi unit, a member of the Northern Chichibu accretionary complex. The kashiwagi unit has been subjected to Pumpellyite-Actinolite facies metamorphism as a low grade part of the Sambagawa metamorphic belt in the Late Cretaceous (100 Ma). The age of chert is Permian Guadalupian (270 Ma) or Late Jurassic (145 Ma). Ages of sedimentary rocks were determined by radiolarians, and metamorphic age by K-Ar or Ar-Ar radiometric dating of muscovite.
An old mine of oxidation zone of bedded Mn deposit in bedded chert of the Kashiwagi Unit. There are two adits on an outcrop of bedded chert. It seems that manganese dioxide ore was mined for manure or battery, not for metal Mn.
Reported Minerals
- Pyrolusite
- Rhodochrosite
- Barite
- Pyrite
Mineral Assemblages
- Rhodochrosite - Pyrolusite
- Chert(Host) - Barite
- Chert(Host) - Pyrite
Localities
- Nakano-Tsuchiyama Mine (Gossan zone)
- Kitamukai-Jizo (Gossan zone)
- Mount Obira (Gossan zone)
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)