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Kurohai village, Choshi city, Chiba pref., Japan


Andesite vesicules

Minerals in vesicules of bronzite andesite of the early Miocene (22 Ma) Senninzuka Formation. The Senninzuka Formation is composed of andesite and tuffaceous sandstone, and sediments of continental to very shallow marine facies. This andesite is high-Mg andesite at the fore-arc side of the island arc. The Senninzuka Formation unconformably overlies the Early Cretaceous (120 Ma) Nagasakihana Formation, the top member of the Choshi Group, and unconformably underlies the early Miocene (17 Ma) Metogahana Formation. Ages of sedimentary rocks were determined by microfossils and ammonites, andesite by K-Ar radiometric dating.


Outcrop of andesite in the Senninzuka Formation. The massive black parts are bronzite andesite. Cracks were filled with white dolomite calcite.

Reported Minerals

Mineral Assemblages

  • Aragonite - Calcite - Celadonite


Related Occurrences

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