Honzawa Mine

Magi, Otsuki city, Yamanashi pref., Japan

Occurrence

Au-Bi-Te-bearing low temperature hydrothermal deposit at the boundary between the late Miocene (10 Ma) Tokuwa Granite and the middle Eocene (45 Ma) Gongenyama Unit of the Sagamiko Group, a member of the Shimanto accretionary complex. Granite at this locality is the S-type (Ilmenite-series) margin of the I-type (Magnetite-series) Tokuwa Granite. The S-type (Ilmenite-series) margin was formed by reduction reation of granite magma with surrounding pelitic rocks. The Gongenyama Unit at this locality has been subjected to Albite-Epidote-hornfels contact metamorphism. Ages of sedimentary rocks were determined by radiolarians, and granite age by K-Ar radiometric dating of biotite and whole rock.

Au-bearing quartz vein in shale of the Gongenyama Unit subjected to contact metamorphism by granite. The light gray part at the upper left is metamorphosed shale. The scale coin is on the milky white quartz vein. Au-Bi-Te minerals are in this quartz vein.

Reported Minerals

Gold
Sulphur
Bismuth
Joséite(Joseite)
Bismuthinite
Pyrite
Arsenopyrite
Ilmenite
Bismutite
Scorodite
Chabazite

Mineral Assemblages

Quartz(Gangue) - Joséite(Joseite) - Gold - Bismuthinite - Bismutite
Quartz(Gangue) - Pyrite
Quartz(Gangue) - Arsenopyrite - Scorodite
Granite(Host) - Chabazite

Produced metal(1942-1943)

Gold ore: 16 tons

History

1942: Began to mine at the open pit.
1943: Closed.

Localities

Honzawa Mine (Granite)
Hara Mine (Granite)
Koshu Mine (Granite)

Related Occurrences

Other Occurrences