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Ashigawa village, Fuefuki city, Yamanashi pref., Japan


Albite-Epidote-hornfels facies contact metamorphic rocks

Dacitic tuff of the middle Miocene (14 Ma) Ashikawa Formation, the Nishi-Yatsushiro group, subjected to Albite-Epidote facies metamorphism by the Ashikawa quartz diorite in the middle Miocene (12 Ma). The Ashikawa quartz diorite is I-type (Magnetite-series). Approximately 500 m apart from the Ashikawa quartz diorite, the heat source. Ages of sedimentary rocks were determined by microfossils, quartz diorite by K-Ar radiometric dating of biotite and hornblende.


Outcrop of dacitic tuff of the Ashikawa Formation subjected to Albite-Epidote-hornfels facies contact metamorphism. Most parts are covered with green moss. Grayish-white parts are metamorphosed tuff composed of quartz and epidote. Epidote was formed by alteration of anorthite.

Reported Minerals

Mineral Assemblages

  • Epidote - Quartz
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