The Daiichi ore deposits of the Shakanai mine are of the socalled "Kurokô" type, having a zonal arrangement of Kurokô (black ore : sphalerite-galena-chalcopyrite-pyrite-barite), Oko (yellow ore : chalcopyrite-pyrite), siliceous ore (pyrite-chalcopyrite-quartz) and gypsum ore, from top to bottom. The hanging wall consists of pumice tuff and mudstone, while the foot wall rocks are rhyolite, rhyolitic tuff, lapilli tuff and tuff breccia. The Kurokô can be divided into several "unit-bodies", most of which are flat and concordant to the sedimentary rocks mentioned above. The Kurokô is classified into "massive Kurokô" and "breccia-like Kurokô" by the mode of occurrence. The breccia-like Kurokô is very similar to turbidite. It has sole marks on the foot wall, imbrication of ore fragments, and vertical sorting of ore fragments. Within each unit-body, the direction of current assumed by the imbrication of ore fragments is from the massive Kurokô toward the margin of the breccia-like Kurokô in agreement with isopach. It is suggested by the shape of ore fragments in breccia-like Kuroko that the fragments were considerably plastic when they were emplaced. Thus, it is reasonable to assume that the massive colloidal Kurokô was formed at the sea bottom. Some parts of the mass was broken down into ore turbidite forming breccia-like Kurokô.
To be more specific, all the unit-bodies are not on the same horizon, but thin mudstones containing fossils of radiolaria, are between them. In a plan view, the unit-bodies are arranged along the NE-SW direction. It is possible that the ore solution passed through the NE-SW fissures of the foot wall rhyolite, and that the mineralization of the Kuroko took place intermittently.

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The Shakanai mine in the northern part of Ôdate district, Akita Prefecture, is one of the largest Kurokô mines in Japan.
Recently, the character of gold and silver in black ores (Kurokô) has become one of practical problems in ore-dressing and refining. Nevertheless, the studies of native gold in these ores are scarce, if at all, less than those of vein type ores. By microscopic examination, the authors discovered native gold in the Shakanai ores. Thus, they studied the properties of native gold by using an electron probe microanalyser, a microphotometer and a microhardness tester.
The gold-bearing ores occur only within compact fine-grained black ores and, banded or colloform finegrained black ores. near vein-like ores rich in chalcopyrite.
Native gold is closely associated with galena. It's average grain size is 10 to 20 μ in diameter, though they are sometimes irregular-shaped. Some are dark yellow, while others are light yellow. The reflectivity ranges from high to low at wavelength 530 mμ. The etch test by CrO₃+HCl brings about a dark spotted texture or an appearance of sun-spot. The electron probe microanalyser examination revealed that the native gold is a impartial mixture of Au and Ag. The ratios, Au : Ag, however, grain by grain.
It is suggested that features of native gold in black ores may be useful for the interpretation of the varies process of black ore deposition.

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Uranium deposits in the vicinity of Nakatsugô-Ombara are distributed apparently on marginal terraces of an ancient river. The richest uranium ore occurs in the thinner basal conglomerate of which thickness is 2 to 3 meters. In the best ore body of the Southern ore body (Nambu-kotai), the abundance of the uranium is closely related to those of S, P, Fe, Ni and Co. Thus, the ore body can be classified into three zones by the zonal distribution of these elements from the center to the rim : Ni-Co-S-P-Fe-U zone, Co-S-P-Fe-U zone and S-P-Fe-U zone. On the other hand, abundances of these elements in the main ore body (Hon-kotai) of shale type are considerably lower. The uranium does not have a good correlation with S, P and As.
Kaolinization and sericitization, regardless of the host rocks (i. e., conglomerate, sandstone and granite), occur around these uranium deposits. This suggests that these alterations might have been genetically related to the minerallization. Montmorillonitization is also found. This alteration is, however, more closely related to the distributions of andesitic, dikes in the granitic basement. Beside the bedded uranium deposits in conglomerate, sandstone and shale, vein type minerallization occurs. in the granite as lenses or veins. They are controlled by joints or dikes of aplite and andesite.
The uranium deposits appears to have been due to an ascending ore solution of relatively low temperatures through cracks of the granitic basement. The uranium of the leached granite must have been enriched in the hot-spring-like solution. As soon as the solution reached to the conglomerate bed, the temperature was lowered by mixing with ground water and other physico-chemical conditions might have been changed. Thus, the uranium was precipitated with such elements of the solution as P, S, Fe, Ni and Co. The upper limit of the ascending solution was controlled by impermeable beds (mainly shale) and a ground water level at the time of mineralization. The uranium in the shale lying over the conglomerate was either a secondly origin dispersed from the conglomerate bed or a primary origin precipitated from the ore solution.

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