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Yahazu Mine

Nishiba village, Ashikaga city, Tochigi pref., Japan


Bedded manganese deposit (Diagenesis)

Bedded manganese deposit preserving original chemical composition and sedimentary structures. This deposit is in the Permian Cisuralian (280 Ma) bedded chert block of the Early Jurassic (180 Ma) Omama Unit. The Omama Unit corresponds to the Funafuseyama Unit of the Tamba-Mino-Ashio accretionary complex. Ages of sedimentary rocks were determined by radiolarians.

Yahazu Mine

Remain of a mine recovered manganese dioxide in chert of the Omama Unit. An adit is at the center of this photograph. The adit wall is composed of grayish-white to grayish-yellow bedded chert, and a few black beds are ore body of manganese dioxide. Manganese dioxide beds are approximately parallel to chert beds, but it partially cuts the chert bed.

Reported Minerals

  • Manganese dioxide

Mineral Assemblages

  • Quartz - Manganese dioxide
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