Three samples of adularia from the different veins of Yatani Pb-Zn-Au-Ag deposits give 3.61±0.27, 3.37±0.13, and 3.25±0.26 Ma. One sample of sericitized rock from Otoge kaolin-pyrophyllite deposits gives 5.16±1.95 Ma. These results indicate that (1) Age of Au-Ag mineralization in the Yatani deposits is nearly same to that of Pb-Zn mineralization in the same deposits, (2) Intense hydrothermal activities occurred at ca. 5±2 million years ago in the Yatani-Otoge mining district, and (3) Vein-type mineralizations occurred in Green tuff region of northeastern part of Honshu during a period of ca. 15-3 Ma.

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Massive sulfide ores from the Shimokawa mine have been studied to approach the ore genesis. A number of polished sections covering almost all part of the Shimokawa orebodies were observed microscopically and the vicissitude of the ore mineral assemblages in the orebodies has been revealed. To consequent, two phases of mineralization related to the formation of the Shimokawa ores have been distinguished, i.e. the early phase mineralization is characterized by precursory cubic or colloform pyrite (py(I)), indicating that it was created in an oceanic ridge as an extrusive magmatic activity, whereas the subsequent one is marked by the presence of chalcopyrite-pyrrhotite assemblage associated with sphalerite, worm-like pyrite (py(II)), cubanite, mackinawite and cobaltpentlandite as accessory minerals. Pyrrhotite has been divided into three types; a) hexagonal, b) monoclinic and c) hexagonal-monoclinic mixture. Hexagonal pyrrhotite tends to occur in lower level and monoclinic one in upper level of the orebodies, while hexagonal-monoclinic mixture occpcupies the intermediate part.
Chemical analyses of some ore minerals have disclosed that Ni in pyrite and pyrrhotite, and Ni, Co in chalcopyrite and cubanite are almost nil, mackinawite shows a notable substitution between Co and Cu, Co/Ni of monoclinic pyrrhotite is extremely high, Co/Ni of cobaltpentlandite is higher in the ores at upper level.
Geochemical profile of the Shimokawa orebodies led us to a conclusion that there is a geochemical zonation suggesting the ore-forming conditions of later phase mineralization varies methodically from southern bottom toward northern top of the orebodies.

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The Minamishiraoi kuroko-type massive barite deposit is located at Morino, Shiraoi Town, Hokkaido. The deposit occurs in Miocene volcanics, consisting of upper barite ore body, lower barite-bearing silicified breccia and footwall clay zone.
X-ray diffraction analyses, DTA-TG and microscopic observation of the clay samples revealed that the footwall clay zone consists of kaolinite, nacrite, dickite, montmorillonite, illite/montmorillonite mixed layer minerals and chlorite/montmorillonite mixed layer minerals together with sulfide minerals such as pyrite, marcasite, chalcopyrite, sphalerite, tetrahedrite and galena.
The clay mineral-sulfide associations are subdivided into two zones in spatial distribution. That is, nacrite, dickite, illite/montmorillonite mixed layer minerals, which are associated with pyrite and chalcopyrite, are distributed in the central zone below the barite-bearing silicified breccia, while kaolinite and montmorillonite, which are associated with marcasite and sphalerite, occur in the peripheral zone.
Judging from the mode of distribution of the clay minerals and their stability data in literatures, it is estimated that the central clay zone below the barite-bearing silicified breccia formed at a temperature range of 100 to 200°C, and the peripheral zone at temperatures lower than 100°C.

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