On the Manganese Deposit and its Prospecting of Nodatamagawa Mine

Abstract

The lenticular manganese ore deposit of the Nodatamagawa mine in the northern part of Iwate Prefecture is concordant in Paleozoic quartzite and was formed after the high grade thermal metamorphism by granitic rock intruded as a batholith near the mine. The ore bodies, constituting the ore deposit of this mine, lie concordantly on near a single horizon of quartzite. This horizon is called "the horizon of ore deposition" for convenience.
The Misago Ore Body is largest and has a very complex form controlled by folding of the country rock; the bonanza is elongated along the fold axis to more than 420 meters from the outcrop. The inner part of the ore body generally consists of manganese oxides, namely pyrochroite and hausmannite with small amounts of manganosite, alabandite, rhodochrosite, braunite, etc., the outer part consists of the manganese silicates, rhodonite and tephroite.
The authors were able to distinguish easily the quartzite of the hanging wall from that of the foot wall on the basis of their appearance and microsocpic features, especially the texture, and the accessory minerals, biotite, garnet, etc.. Therefore in this mine, a prospecting method based on microscopic study and a survey of folding in the country rock was very useful and successful.