Hotokezaki
Tokiwa, Omachi city, Nagano pref., Japan
Occurrence
Dolomite skarn deposit formed in the Permian Guadalupian (270 Ma) dolomite-limestone block of the Early Jurassic (180 Ma) Funafuseyama Unit of the Tamba-Mino-Asho accretionary complex. The dolomite-limestone block has been subjected to contact metamorphism by the early Paleocene (63 Ma) Ariake Granite. The Ariake Granite is I-type (Magnetite-series). Approximately 500 m apart from the Ariake Granite, the heat source. Sediments were attributed to the Funafuseyama Unit based on the lithology and distribution of the Kamiaso Unit in the southern area. Ages of sedimentary rocks were determined by radiolarians.
Outcrop of dolomite skarn of the Funafuseyama Unit. The black parts are composed of spinel, forsterite, clinohumite, and phlogopite. The white parts are calcite. The purple parts between black and white parts are rich in clinohumite. The brown part at upper left is limonite crusts formed by weathering of pyrrhotite inclusions.
Reported Minerals
- Spinel
- Forsterite
- Clinohumite
- Phlogopite
- Grossular
- Diopside
- Wollastonite
- Actinolite
- Pyrrhotite
- Serpentinite
Mineral Assemblages
- Calcite - Spinel - Forsterite - Clinohumite - Phlogopite - Pyrrhotite
- Grossular - Diopside - Actinolite
- Calcite - Forsterite - Serpentinite
- Wollastonite - Calcite
Localities
- Kasuga Mine (Dolomite skarn)
- Hotokezaki (Dolomite skarn)
- Ishibaiyama (Dolomite skarn)
- Mount Hiiragi (Dolomite skarn)
Related Occurrences
- Skarn (I-type, Magnetite-series)
- Skarn (S-type, Ilmenite-series)
- Skarn (Sanidinite facies)
- Dolomite Skarn