Tabi
Tabi, Numazu city, Shizuoka pref., Japan
Occurrence
Fe-Mn deposit associated with andesitic tuff of the late Miocene to early Pleistocene (9.0-2.0 Ma) Shirahama Group. The deposit is concordant with the bedding plane but some veins of Fe-Mn minerals cut the bedding plane. It was formed probably by low temperature hydrothermal activity. Andesite is calc-alkaline to tholeiite series. Ages of sediments were determined by microfossils and K-Ar radiometric dating.
Outcrop of Fe-Mn deposit by low temperature hydorthermal activity in andesitic tuff of the Shirahama Group. The massive black part at the bottom is aggregate of various Mn minerals. The reddish-brown part at the middle is hematite-rich zone. The light gray beds above the deposit is andesitic tuff, and the massive part at the top is andesitic tuff breccia. This andesitic tuff with Fe-Mn deposit overlies the andesite basement.
Reported Minerals
- Pyrolusite
- Todorokite
- Cryptomelane
- Braunite
- Hausmannite
- Hematite
Mineral Assemblages
- Pyrolusite - Braunite - Todorokite - Cryptomelane - Hausmannite
- Hematite
Localities
- Tabi (Metasomatism, Braunite)
- Ikeshiro Mine (Metasomatism, Todorokite)
- Cape Osaki (Basalt lava, Ranciéite)