Kita-Tomida
Kita-Tomida, Daigo city, Kuji county, Ibaraki pref., Japan
Occurrence
Intermediate acidic metasomatic rocks of low-T silicified zone
Chalcedony veins by silicification alteration in dacitic pyroclastics of the middle Miocene (15 Ma) Nantaisan Volcanic Breccia. The silicification was by the volcanic activity of the Nantaisan Volcanic Breccia. The Nantaisan Volcanic Breccia is composed of oceanic tholeiitic dacite and dacitic pyroclastics associated with icelandite. The Nantaisan Volcanic Breccia is submarine sediments and was formed in a subtropical climate. The Nantaisan Volcanic Breccia conformably overlies the Asakawa Formation, and conformably underlies the Naeshiroda Formation. Ages of volcanic rocks were determined by fossils and fission track dating, and climate by floras.
Outcrop of chalcedony vein in dacitic volcanic breccia of the Nantaisan Volcanic Breccia. The white vein is chalcedony with open spaces at the center. The reniform aggregates are observed near the coin. The gray host is dacitic volcanic breccia.
Reported Minerals
- Chalcedony
- Quartz/Amethyst
Mineral Assemblages
- Chalcedony - Quartz/Amethyst
History
- 1600-1800: Chalcedony was mined as flint.
- 1800-1975: Chalcedony was mined as ornamental stone.
- 1975: Stopped mining.
Localities
- Narayama (Rhyolite, Ferrierite-K)
- Katsura Island (Rhyolite, Ferrierite-Mg)
- Kita-Tomida (Dacite, Chalcedony)
- Shibusawa Mine (Gypsum deposit)
- Nanataki fall (Pyrite)
Related Occurrences
- Halloysite zone (Alunite zone, Argillized zone)
- Kaolinite zone (Alunite zone, Argillized zone)
- Minamiite-Alunite zone (Alunite zone)
- Pyrophyllite zone
- Smectite zone (Argillized zone)
- Interstratified mineral zone (Argillized zone)
- Illite-Chlorite zone (Propylite zone)
- Epidote-Actinolite zone
- Stilbite-Mordenite zone (Zeolite zone)
- Heulandite-Analcime zone (Zeolite zone)
- Laumontite-Albite zone (Zeolite z., Propylite z.)
- Wairakite-Albite zone (Zeolite zone)