Low-temperature silicified zone
Chemical Process (Alteration) - Open system under ground (Acidic-Neutral metasomatism)
Correlated: High-T zeolite facies
Index Minerals
Quartz, Smectite
Required Geological Setting
Metasomatic rocks (Intermediate acidic)
Occurrence
Metasomatic zone formed by acidic-neutral hydrothermal fluid of 100-250 degree associated with Rhyolitic to Dacitic magma activities. This alteration is called low-temperature silicification. Protoliths are felsic rocks. Low-temperature silicified zone may be associated with Low-T hydrothermal deposits.
Distribution of low-temperature silicified zones described in this site. Yellow lines are volcanic fronts.
Change of mineral assemblages
- [ Extinct ] Cristobalite
- [ Appear ] Quartz, Smectite/Illite, Smectite/Chlorite
Mineral Assemblages
- Quartz, Pyrite, Smectite/Illite, Smectite/Chlorite, (Anhydrite)
Localities
- Narayama (Rhyolite, Ferrierite-K)
- Katsura Island (Andesite, 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)