Japan

Misawa Japan and Environs

Japan Mines

by James Mallonee

excerpt from the Geologic Survey of Japan

Taro Mine: This is a copper, zinc, and lead mine. The Taro mine is situated on the east side of the Kitakami mountain land and 5 KM from the coast (south of Omoto). The ore deposit occurs in Paleozoic sandstone and clay slate lying on the porphyrite as a roof-pendant. The porphyrite preceded granites, but is genetically related to the igneous activity. No ore bodies are found in the porphyrite. Schistosity is frequently developed in the porphyrite near the ore bodies. Porphyrite of this kind resembles sericite schist. In the mining area, along a zone 10-30 KM from the boundary plane with porphyrite, the roof-pendant Paleozoic formation is composed of black clay slate and sandstone. To the east, a silicified zoneíe is developed it is 30-40 KM wide and extends i the strike direction. Farther to the east, ie:in the formation underlying the silicified zone, a cupriferous pyrite zone occurs. In the silicified zone, the original textures of the sandstone and clay slate are commonly lost. The ores in the black clay slate and sandstone zone and the silicified zone are massive aggregates of sphalerite and galena, closely resembling the "Kuroko" (Black Ore). In the cupriferous pyrite zone, the ore bodies are bedded in the sericitized or chloritized sandstone or clay slate. Near the ore bodies, sericitization or chloritization of the country rocks is conspicuous. Lenticular ore shoots occurs here and there along the bedding plane, generally arranged in a horizon of the sedimentary rock. The ore in this zone is composed of pyrite, chalcopyrite and pyrrhotite. The country rock surrounding each ore shoot is impregnated with pyrite. The ore shoots are linked by tabular ore zones. Kamaishi Mine: South of the Taro Mine (and Taro). The largest magnetite deposit of pyrometasomatic type in Japan.

Just south of the Taro Mine, between Taro and Miyako. Both the Kamaishi and the Yamaguchi are the same type... The Yamaguchi deposit exists in the limestone of a roof-pendant Carboniferous formation on the younger granite. The ore minerals are chalcopyrite and pyrite, with small amounts of sheelite (bearing a powelite molecule), cubanite, molybdenite, sphalerite, ilmenite, and uranite. The skarn and gange minerals in the deposit are garnet, diopside, amphibole, titanite, apatye, allanite, chlorite, etc.