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Nishinomaki Mine

Minami-Nomaki, Shimonita city, Kanra county, Gunma pref., Japan

This locality is closed to collecting.

Synonym

Saimoku Mine

Occurrence

Low-T hydrothermal deposit

Low-T hydrothermal deposit associated with the late Miocene (6.0 Ma) andeste-dacite dikes intruded in andesitic tuff breccia of the Motojuku Formation of the same age. The Motojuku Formation is composed of andesitic tuff breccia and andesitic-dacitic dikes filling the late Miocene-Pliocene Motojuku Caldera. Approximately 1 km apart from the Ichinokaya Caldera Complex, the caldera complex of the Motojuku caldera. Ages of volcanic rocks were determined by K-Ar radiometric dating.

Nishinomaki Mine

Outcrop of realgar veins in andesitic tuff breccia of the Motojuku Formation. The grayish-white host is altered andesitic tuff breccia. The red to orange parts are realgar. Fine realgar grains are scattered in the host.

Reported Minerals

Mineral Assemblages

  • Realgar - Pyrite - Stibnite
  • Realgar - Orpiment - Quartz - Wakabayashilite
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