The "chalcopyrite disease" texture as found in the Kuroko ores, was experimentally reproduced under hydrothermal conditions using a temperature-gradient transporting method. The amounts of chalcopyrite crystals intergrown with sphalerite in the run products are similar to those in some sphalerite-rich Kuroko ores. These facts suggest that fine-grained blebs of chalcopyrite in low-Fe sphalerite have been generated in the process of coprecipitation. The results of thermodynamic calculations of the saturation indices for sphalerite and chalcopyrite under the experimental conditions indicate that the saturation index for chalcopyrite is more temperature-dependent than that for sphalerite. This explains a common texture found in the run products, which suggests that chalcopyrite precipitated first and served as heterogeneous nucleation centers for the growth of sphalerite.

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Strata-bound manganese oxide and manganiferous iron deposits are distributed in the Tokoro Belt. The manganiferous iron deposits are found between the bedded chert and greenstone whereas the manganese oxide deposits usually occur within the radiolarian chert. These deposits are regarded to have been formed by submarine hydrothermal activities, as inferred from the mode of occurrence of the country rocks.
The manganese oxide ores are characterized by low Fe/Mn ratios which are similar to those of the submarine hydrothermal deposits. The average Fe/Mn ratios of manganese oxide and manganiferous iron deposits are 0.017 and 6.41, respectively. It is considered that the fractionation between Fe and Mn takes place during their formation. According to the distribution of the trace elements (Co, Ni, Cu, and Zn) in the manganese oxide ores, two types can be distinguished: one type has rather high chemical concentrations as hydrogenous deposits, the other has low concentrations as submarine hydrothermal deposits.
These compositional trends and geological evidences on the occurrence of manganese deposits suggest that they are syngenetic and have been formed by precipitation from submarine hydrothermal activities with limited hydrogenetic effects during early Cretaceous.

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The ore deposit of the Kato mine consists principally of narrow gold-silver-bearing lead-zinc veins emplaced along fissures in the Cretaceous Kanmon Group. The primary ore minerals are sphalerite, galena, pyrite, chalcopyrite, bornite and electrum. Small grains of hessite and sylvanite have been firstly found. Associated secondary minerals, covellite, brochantite and a digenite-like mineral are mineralogically described. The homogenization temperatures of liquid rich two-phase fluid inclusions in quartz range from 220°C to 290°C. Using this temperature range and the FeS content (1.1-1.7 mole%) in sphalerite, the sulfur fugacity of chalcopyrite-sphalerite-galena-pyrite assemblage is estimated to have the range of-13.1 to -8.4 on a log scale.

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Spinel, magnesioferrite and magnetite are found in the Shinyemi magnesian skarn-type iron deposit. There are close relationships between the mode of occurrence and the chemical composition of these minerals. Spinel formed during the metamorphic stage has a chemical composition close to MgAL₂O₄. Metasomatic spinel, nearly simultaneously formed with "magnetite I" during the progressive skarn formation, can be expressed in the spinel-hercynite binary system with ranging from 24.1 to 34.5 mole% FeAL₂O₄ component. "Magnetite I", commonly associated with olivine, ranges in composition from 62.4 to 98.3 mole% FeFe₂O₄, from 0.0 to 30.3 mole% MgFe₂O₄, from 0.0 to 7.3 mole% FeAL₂O₄, and from 0.6 to 3.1 mole% MnFe₂O₄ components. It generally contains exsolu-tion bodies of spinel with the composition of 68.7-83.1 mole% MgAL₂O₄, 6.2-21.3 mole% FeAL₂O₄ and 5.5-9.7 mole% MgFe₂O₄ components. "Magnetite I" is frequently replaced by the late formed magnetite ("magnetite II") associated with Mg-rich chlorite, serpentine and carbonate minerals during the retrogressive process. Compositions of "magnetite II" are represented in the MgFe₂O₄-FeFe₂O₄-MnFe₂O₄ ternary system. It extends to about 28.2 mole% MnFe₂O₄. During the almost same stage to that of "magnetite I", "magnesioferrite I" was crystallized in dolostone near the magnetite ore bodies, it contains 59.1-70.7 mole% MgFe₂O₄, 5.7-11.7 mole% MgAL₂O₄, 2.6-27.3 mole% FeFe₂O₄ and small amounts of FeAL₂O₄ and MnFe2O4 components. The late formed magnesioferrite ("magnesioferrite II") has considerable amounts of FeFe₂O₄ and MnFe₂O₄ components.

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