Limonite Deposits of the Chokai-Shunomata Mine, Akita Prefecture, with Special Reference to the Occurence of Phosphorus in the Deposits

Abstract

The limonite depsits of the Chokai-Shunomata Mine, in the Chokai volcano area, are located about 28km south of Yashima City, Akita Prefecture, Japan.
The area is covered by lavas of Chokai valcano.
The deposits are of bedded type precipitated from cold ferruginous spring water.
Microscopic observation shows that the ores are formed mainly of goethite-and jarosite-like minerals which cover the inner walls of cavities in the ores.
Such elements as Al, Si, K, Ti, and P have been detected in the ores by spectrographic methods.
Phosphorus content of the ores is about 0.5-2.0 per cent, which is considerably higher than that of ordinary limonitic ores of Japan.
The limonitic bed of this mine may be classified into the following three zones:
1: zone of high phosporus content (more than 1.4%P)
2: zone of intermediate phosphorus content (14-1.0%P)
3: zone of low phosphorus content (less than 1.0%P)
As noted in Fig.5, showing the distribution of phosphorus in the limonite deposits, lateral changes of ore characteristics are marked.
The distribution of the three zones mentioned above, are shown in figs. 6 and 7.
In general, the zones of both high and low content are limited in distribution. whereas that of intermediate phosphorus content is more extensive in the ore bed down stream as compared to upstream.