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Mount Chiba

Chiba, Shimada city, Shizuoka pref., Japan


Prehnite-Pumpellyite facies metamorphic rocks

Basaltic tuff breccia with laumontite and datolite veins in the Eocene to early Miocene (50-20 Ma) Setogawa Group, a member of the Shimanto accretionary complex. Setogawa Group of this locality has been subjected to Prehnite-Pumpellyite facies metamorphism. The age of basaltic tuff breccia is approximately early Eocene (48 Ma), and paleomagnetism suggests it was erupted at 23 degree north latitude. Ages of sedimentary rocks were determined by radiolarians.

Mount Chiba

Outcrop of basaltic tuff breccia of the Setogawa Group. The network of white veins are datolite. Clear crystals are in open spaces of this vein. The dark grayish-green host is tuff breccia. The vein is composed of many thin veins, which means vein formation was repeated many times.

Reported Minerals

Mineral Assemblages

  • Calcite - Laumontite
  • Laumontite - Datolite
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