Obira Mine
Obira-Kozan, Ogata, Bungo-Ono city, Oita pref., Japan
Occurrence
Skarn formed by the middle Miocene (14 Ma) Okueyama Granites intruded in serpentinite mélange, the Kurosegawa Tectonic Zone, The pneumatolytic deposit associated with the skarn was formed by th ring dike of granite porphyry. The Okueyama Granites are S-type (Ilmenite-series), and is approximately 15 km apart from this locality. The sulfide deposits are in contact with the ring dike of granite porphyry. The age of limestone is late Silurian (420 Ma). The Okueyama Granites and the ring dike of granite porphyry are members of the Miocene Okueyama Caldera Complex, and the Okueyama Granites are the center pluton of the caldera complex. Ages of sedimentary rocks were determined by microfossils, and igneous rocks by K-Ar radiometric dating of biotite and Rb-Sr isochron age.
Reported Minerals
- Axinite-(Fe)
- Ilvaite
- Schorl
- Stilpnomelane
- Hedenbergite
- Grossular
- Grunerite
- Datolite
- Hastingsite
- Sphalerite
Mineral Assemblages
- Axinite-(Fe) - Datolite
- Grunerite - Ilvaite - Stilpnomelane
- Hastingsite - Sphalerite
Produced metal(1941)
- Ore: 53,222 tons
- Metal Tin: 391 tons
History
- 1547: There is a record that silver was mined.
- 1617: Started to mine tin.
- 1940: Concentrator was built.
- 1954: The mine was closed.
Localities
- Kamioka Mine (Pb-Zn)
- Kiura Mine (Emery)
- Toroku Mine (Arsenate)
- Obira Mine (Granite porphyry)
- Hoei Mine (Granite porphyry)