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Shiraki village, Toba city, Mie pref., Japan


Greenschist facies serpentinite

Serpentinite block along the Gokasho-Arashima Tectonic Line. This serpentinite is probably blocks of the Permian Guadalupian (270 Ma) Sawadani unit, a member of the Northern Chichibu accretionary complex. Serpentinite has been subjected to Greenschist to lower Amphibolite facies metamorphism in the Early Jurassic (200 Ma). The protolith of serpentinite is dunite and harzburgite, and considered as refractory peridotite of the wedge mantle. The origin of this serpentinite block is considered as sedimentary serpentinite mélange from serpentinite seamounts at the fore-arc slope. Ages of sedimentary rocks were determined by radiolarians, and metamorphic age by K-Ar radiometric dating of muscovite.


Outcrop of the boundary between serpentinite sedimentary rocks of the Sawadani Unit. The dark green part from the middle to the right is serpentinite. The brown part at the left of the trench is sedimentary rocks such as sandstone and shale. The white block at the lower left is rodingite in serpentinite. Note that the serpentinite is not massive but is foliated vertically probably as the result of regional metamorphism.

Reported Minerals

Mineral Assemblages

  • Serpentine - Aragonite
  • Serpentine - Hydromagnesite - Artinite
  • Serpentine - Pectolite - Vuagnatite
  • Rodingite - Aragonite - Coalingite - Suolunite
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