Orihara
Orihara, Yorii city, Osato county, Saitama pref., Japan
Occurrence
Greenschist facies serpentinite
Actinolite-bearing talc schist included in Sanbagawa Metamorphic Rocks. Formation of talc can be explained by the reaction of serpentinite with quartz in surrounding sedimentary rocks. The origin of this serpentinite block is considered as sedimentary serpentinite mélange from serpentinite seamounts at the fore-arc slope.
Outcrop of talc schist and pelitic schist of Sanbagawa Metamorphic Rocks. The upper black part with horizontal schistosity is spotted pelitic schist. The boundary between the upper pelitic schist and lower white talc schist is a small horizontal fault. There is another pelitc schist bed below the talc schist and it is subjected to strong deformation. The scale coin is at the lower right. Formation process of carbonate-absent talc schist can be explained by reaction of serpentinite with quartz as follows:
Mg3Si2O5(OH)4 (Serpentine) + 4SiO2 >> Mg3Si4O10(OH)2 (Talc) + H2O
Reported Minerals
- Actinolite
- Talc
- Fuchsite
- Albite
Mineral Assemblages
- Talc - Actinolite
- Pelitic schist(Host) - Fuchsite
Localities
- Orihara (Talc, High-P)
- Matsunaga Mine (Talc, High-P)
- Arai (Diopside, High-P)
- Osaka (Ophicalcite, High-P)
- Miyazawa (Dolomite, High-P)
- Onara (Fe-Ni, High-P)
- Yashio mine (Fe-Cr, High-P)