TrekGEO > Mineral Trail > Kanto region > Tochigi pref. > Higashizawa Mine

Japanese page

Higashizawa Mine

Kami-Kasuo, Kanuma city, Tochigi pref., Japan


Hornblende-hornfels facies bedded manganese deposit

Chert-hosted bedded manganese deposit in the Late Triassic (220 Ma) to Early Jurassic (175 Ma) chert block of the Late Jurassic (145 Ma) Kurohone-Kiryu Unit. The deposit has been subjected to Hornblende-hornfels facies contact metamorphism by the Kobugahara granodiorite in the early Paleocene (64 Ma). Slate near this deposit was metamorphosed to Cordierite-bearing hornfels. The Kurohone-Kiryu Unit corresponds to the Kanayama Unit of the Tamba-Mino-Ashio accretionary complex. The Kobugahara granodiorite is S-type (Ilmenite-series). Approximately 2 km apart from the Kobugahara granodiorite, the heat source. Ages of sedimentary rocks were determined by radiolarians, and granodiorite by K-Ar radiometric dating of biotite.

Reported Minerals

Mineral Assemblages

  • Rhodonite - Mn bearing tremolite
  • Rhodonite - Spessartine - Pyrophanite - Quartz
Copyright (c) 2015 NariNari, All Rights Reserved.