Karasawa Mine
Itaga, Kanuma city, Tochigi pref., Japan
Occurrence
W-Bi pneumatolytic deposit associated with the early Paleocene (63 Ma) Karasawa Granodiorite intruded in the Late Jurassic (145 Ma) Kurohone-Kiryu Unit. The Karasawa granodiorite is S-type (Ilmenite-series). The Kurohone-Kiryu Unit corresponds to the Kanayama Unit of the Tamba-Mino-Ashio accretionary complex. Ages of sedimentary rocks were determined by radiolarians, and granodiorite by K-Ar radiometric dating of muscovite and biotite.
Outcrop of the Karasawa Granodiorite, the host of a W-Bi pneumatolytic deposit. The silver-white muscovite was formed in the granodiorite by strong alteration. The brown part at the upper right is the ilmonite crust formed by weathering of sulfide minerals.
Reported Minerals
- Bismuth
- Joséite(Joseite)
- Ferberite
- Bismutite
- Bismuthinite
- Muscovite
- Schorl
Mineral Assemblages
- Quartz - Bismuth - Bismutite
- Quartz - Joséite(Joseite)
- Quartz - Ferberite
Locality
- Takatori Mine (Ferberite)
- Ebisu Mine (Wolframite)
- Togane Mine (Wolframite)
- Komaki Mine (Wolframite)
- Itaga Mine (Andalusite)
- Otani Mine (Cassiterite, Scheelite)
- Taisho Mine (Cassiterite)
- Ichiyanagi Mine (Löllingite)
- Takane Mine (Bismuth)
- Karasawa Mine (Bismuth)
- Takemori (Dravite)