Studies on the Bedded Limonitic Iron-Ore Deposits in Japan with Special Reference to their Genesis and Minor Elements

Abstract

The bedded limonitic iron-ore deposits found in Japan are genetically classified into two major types, i. e., the hypogene type and the supergene type. Furthermore, the hypogene type may be subdivided into the simple hypogene and the complex hypogene type, and the supergene type may be subdivided into the secondary-enrichment supergene and the concentration supergene type.
Though all the ores from any of these deposit types are mainly composed of goethite, the types are characterized by the minor elements. Some of these elements are useful as indicators in prospecting for iron-sulphide deposits under or near the limonitic iron-ore deposits.
Around many volcanic craters, the following zonal arrangement can be observed outward from the center : solfatara, sulphur deposits, strongly acidic hot springs, limonite deposits of the simple hypogene type, ferruginous springs, moderately to weakly acidic hot springs, and neutral or weakly alkalic hot springs. This arrangement is a useful geologic tool in discovering new limonite deposits of the simple hypogene type.
As plants-particularly the living bryophyta-are considered to play a more important role than ironbacteria, the writer describes the mechanism of iron-ore deposition from the botanical point of view.
The limonitic iron-ore bed of the Kamikita mine was sampled systematically along the Okuno-sawa valley. This bed is of the secondary-enrichment supergene type. The samples were analyzed spectrogr-aphically for minor elements, and the behaviour of these elements is explained from the viewpoint of their ion-potential.