Omiya Mine
Niihori, Hidaka city, Saitama pref., Japan
Synonym
Hidaka Mine
Occurrence
Pumpellyite-Actinolite facies bedded manganese deposit
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 adit is on the outcrop of bedded chert of the Kashiwagi Unit. The creek in front of this adit is buried by a huge amount of dump.
Reported Minerals
- Pyrite
- Calcite
- Rhodochrosite
- Rhodonite
- Caryopilite
- Unidentified mineral(white to pink, acicular)
Mineral Assemblages
- Caryopilite - Rhodochrosite - Quartz
- Rhodonite - Rhodochrosite - Quartz
- Quartz - Hematite - Pyrite
- Quartz - Rhodochrosite - Unidentified mineral
History
- around 1900: Mn was mined in adits.
- after 1945: Mined at an open pit.
Localities
- Omiya Mine (Hausmannite)
- Iwaisawa Mine (Braunite)
- Hinozawa Mine (Rhodochrosite)
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)