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Kami-Suwa

Suwa village, Hitachi city, Ibaraki pref., Japan

Occurrence

Greenschist facies metamorphic rocks

Chloritoid schist and limestone of the Cambrian Series 3 (500 Ma) Daioin Formation subjected to Greenschist facies metamorphism in the Late Cretaceous (100 Ma) medium-P Abukuma metamorphic belt. The protolith of chloritoid schist is Terra Rossa formed by weathering of limestone under tropical condition. The chloritoid schist was discovered in 1889. Monoclinic and Triclinic polytypes were recongized. Age of limestone was determined by coral fossil, and metamorphic age by K-Ar radiometric dating of muscovite.

Kami-Suwa

Outcrop of chloritoid schist of the Daioin Formation with clear schistosity. The scale coin is on the chloritoid schist. The massive grayish-white parts on both sides are metamorphosed limestone. The protolith of chloritoid schist is Terra Rossa, high Fe-Al soil, formed by weathering of reef limestone under tropical condition.

Reported Minerals

  • Chloritoid
  • Calcite

Mineral Assemblages

  • Calcite
  • Chloritoid - Chlorite - Muscovite - Quartz

History

  • 1889: Described as Ottrelite.
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