The Katsuraoka mining district lies on the northern periphery of the Hiyama Palaeozoic massif which forms the core of the Oshima peninsula, Hokkaido. So-called Palaeozoic slates intercalated with limestone and thin layers of chert form the basement members of the district; they are covered by a Neogene Tertiary pyroclastic formation.
Among the basement members a narrow N 20°W trending mineralized zone is noticeable, in which small deposits of magnetite, pyrrhotite and pyrite are scattered. The deposits are found along the N-S trending sheared zone, and most of them are associated with diabase dykes.
The ore deposits can be classified into the following three types; 1) magnetite deposits, 2) pyrrhotite deposits, and 3) pyrite depasit. Pyrometasomatic êffects are indicated by a lime-silicate association produced upon the surrounding diabase. The alteration of wall rocks is succeeded, without exeeption, by later hydrothermal chloritization, sericitization or silicification. The pyrite mineralization corresponds to a hydrothermal candition, while the mineralization of magnetite and pyrrhotite corresponds to the earlier pyrometasomatic condition.
The geological circumstances and the character of mineralization of the ore deposits indicate that they belong to a cupriferous iron sulphide deposit.

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In the Sangasho district, Miyazaki Prefecture, there are a number of diabase sheets or flows in the Paleozoic strata of geosynclinal deposition. These diabases have an areal extention and behave like the country rock of the "Kieslager".
This paper describes the relationships between the mineralization and alteration of the wall rocks, and the distribution of the major chemical elements in the altered diabases, on the basis of distance from the ore bodies. The features of the alteration seem to support the following conclusions.
(1) As a result of autometamorphism of the basaltic diabase in the course of cooling, it became the green rock which is characterized by amphibole, chlorite, zoisite, and albite and later the hematitized chlorite diabase by some hydrothermal solutions.
(2) There is some possibility that the "Kieslager"of the Sangasho-type might have been deposited by a hot spring(containing gas)on the floor of an oceanic basin or geosyncline, just after the submarine eruption of the diabase.

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In order to determine the range of formation temperatures of ore deposits, the liquid inclusions occurring in minerals from the following four mines in Japan were studied by the heating microscope method. In this experiment, the filling temperatures were determined by observing the disappearance of gas bubbles in the liquid inclusions.
Minerals whose filling temperatures were determined are quartz and calcite. The specimens of quartz were collected from three mines, Seigoshi, Amagi and Akatani, and those of calcite from the Nakatenjo mine, a branch mine of the Nakadatsu mine. They are closely associated with the ore minerals in each deposit.
Judging from the modes of occurrence of the host minerals, most liquid inclusions occurring in these specimens seem to be of primary origin.
Temperature data obtained in this study are shown in Table 1 and Figs. 3-4.
Ore deposits of both the Seigoshi and Amagi mines consist of gold quartz veins and are said to be of typically epithermal origin. Large parts of the hematite deposits of the Akatani mine are of the replacement type in Paleozoic limestone and are considered to be of hydrothermal origin. Lead and zinc deposits of the Nakatenjo mine may also belong to hydrothermal deposits of a low temperature type.
Therefore, the temperature data obtained in this study agree well with the formation temperatures which have been estimated, though qualitatively for these deposits, from other geological phenomena. The data give quantitative evidence to the former qualitative estimate.

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There are two types of lead-zinc deposits in the Tertiary greentuff region of Japan. One is a vein-type deposit and tbe other is a massive black ore deposit, the so-called "Kuroko" deposit.
The author concluded that the original ore solutions for both types of deposits have alinost the same characteristics, but formed different types of deposits according to the geologic environment of their precipitation.
The rocks surrounding the vein deposits are mainly massive and easily fissured. On the other hand in the case of the massive black ore deposits, the country rocks consist of a tuffaceous shale of plastic character. These rocks became folded and, as a result of exogenetic forces, some bedding slips occurred so that the precipitation of the ore minerals probably took place in the enclosed cracks.
The author also discusses the analogous conditions of formation between the black ore deposits and some of the cupriferous pyritic bedded deposits in southwestern Japan.

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Because of the intrusive and eruptive activity of rhyolite, the Tertiary formations in the Ikuno District have a basin-like structure. Many intrusives of various rock types, from acidic to basic, occupied fractures which occurred under stress caused by structural deformation, especially sheets and dikes of basalt controlled the formation of are veins at the Ikuno Mine.

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