Three lines of evidence which support the magmatic hydrothermal origin of kuroko deposits are evaluated.
(1) Mineralization of kuroko deposits took place around 15 Ma, at the same time as several other geologic episodes including a major shift in the tectonic stress field, a peak of bimodal volcanic activity, and a maximum degree of subsidence. The style of eruption of rhyolite changed from lava flows, acid hyaloclastites, and lithic tuff breccias before mineralization to extensive post-ore pumiceous pyroclastic flows. In an analogy with the Yellowstone caldera, absence of pre-ore basalt directly below the known kuroko deposits suggests that contemporaneous acidic magma existed at a depth of a few kilometers with the potential to release magmatic fluid. Basalt lava is often seen in the hanging-wall sequence of kuroko deposits; it extruded after the acidic pluton had solidified subsequent to mineralization. The post-ore pumiceous pyroclastics could have been produced by violent submarine eruptions similar to those related to the formation of Valles type calderas from resurgent acidic magma. Apparently such an abrupt release of material from the magma chamber was not suitable for conditions to develop and form kuroko deposits. (2) Based on oxygen and hydrogen isotopic study, sea water cannot be the sole source of the kuroko ore solution. Metals cannot be leached from footwall volcanic rocks, because an outward flow of hydrothermal fluids within the volcanic units is deduced from wall-rock alteration study. In addition, the notable homogeneity of isotopic compositions of ore minerals rules out the possibility that the ore metals were largely derived from basement rocks by leaching. (3) The rhyolitic magma which was contemporaneous with ore deposition had a large potential to result in separation of a metal-rich aqueous solution during its crystallization. This aqueous phase would have been a very efficient ore-forming solution, even after dilution by convecting sea water. This magmatic hydrothermal model of kuroko deposits is more consistent with the observed geological features than other models.

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The copper, zinc and tin veins of the Akenobe mine are of polymetallic xenothermal type deposits. The following mechanism of metal precipitation is deduced based on the assay contour maps of the veins.
(i) Ore shoots in a vein coincide with wider parts of the vein fracture and plunge northwest.
(ii) These ore shoots in a vein are aligned along a zone which plunges southeast.
(iii) A southwestward dipping plane is obtained by connecting these zones of parallel running veins in the mining area.
(iv) A Zn-rich zone is situated at levels upper than that of Cu-rich zone throughout the ore field. A Sn-rich zone is situated at the lowest level in the northeast area. However, in the south area, it is situated at the same level as the Cu and/or the Zn-rich zones.
These modes of metal zoning can be explained by reasonable assumption that the hydrothermal solution rose perpendicularly to the flat-lying isothermal planes passing mainly through the wider part of vein fractures.
The isothermal plane is considered to be nearly horizontal at a discharge area as is the case of recent geothermal systems. Therefore, it is estimated that the Akenobe ore deposits are wholly tilted by post ore tectonic phenomena toward south.
The volume of the ore-forming solution, the total thermal energy, and metal concentration in the solution are estimated to be 4.8×10¹⁰m³, 4.7×10¹⁶kJ and 20mg/kg, respectively.

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Southern Kamuikotan tectonic belt, including the Mukawa-Sarugawa ultramafic mass, is well known for occurrence of chromite, from where 400×10³ metric tons of high-chromium ores were produced. Recently, clinopyroxenite-hosted podiform chromite-bodies in which abundant kämmererite and chromium-bearing hydrogrossular occur have been found at the Tomiuchi mine in the Mukawa-Sarugawa ultramafic mass. The clinopyroxenite in the Tomiuchi mine is composed mainly of coarse-grained chromian diopside. Kämmererite, faint violet in color, occurs extensively within the chromite-body, whereas chromium-bearing hydrogrossular, grass green in color, is exclusively found in a pectolite vein at the contact with the chrome-ore. As a consequence, we came to a conclusion that chromian diopside is of igneous phase, while kämmererite and chromium-bearing hydrogrossular belong to deuteric and hydrothermal phases, respectively.

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Sulfurs in the crude oils and kuroko sulfides from the Green Tuff region of northeastern Japan are isotopically indistinguishable from each other. The observation calls for re-evaluation of the role of biogenic sulfur in "volcanogenic" sulfide mineralization.

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K-Ar ages for adularia from the Fuke, Okuchi, Hishikari, Kuronita, and Hanakago gold-silver deposits are determined as 1.40±0.19, 1.1±0.5, 0.86±0.12, 1.3±0.7, and 1.1±0.5 Ma, respectively. The results suggest that these deposits in the eastern zone of the Satsuma district were formed in the Pleistocene age. There are gold-silver deposits of latest Miocene to early Pliocene in age in the western zone. On the other hand, the active geothermal systems are observed along the volcanic front in the eastern margin of the district. It is considered, therefore, that the centers of both volcanic activity and mineralization migrated from west to east since the late Miocene age.

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