The ore deposits of the Kasuga mine and Akeshi, mine, located about 6km west and 10km east of Makurazaki city, Kagoshima Prefecture, are those of epithermal origin.
The gold deposits of net-work type are found in silicified rocks formed by hydrothermal alteration from the andesitic tuff, tuff breccia and propylite of Tertiary age.
Vertical and horizontal zoning of minerals in alteration zone of silicified rocks are as follows:
i) Vertical zoning from upper part to lower in the central area; silicified zone→alunite zone.
ii) Horizontal zoning from inner part to outer;
Silicified zone→dickite zone→limonite-kaolinite zone→kaolinite zone→original rock.
The metallic minerals of the ores include native gold, luzonite, enargite and pyrite. Among them enargite is the most characteristic in the Kasuga mine, and luzonite in the Akeshi mine.
From the observation of about 1, 000 gold particles on polished sections of gold ore from Akeshi mine, it is concluded that native gold is intimately associated with luzonite and pyrite, and apparent mean size of gold particles is 15μ