Pentlandite has been found as a widespread minor or trace mineral in contact-metasomatic type copper and iron-copper ores of the Kamaishi mine. The mineral usually occurs as microscopic grains up to 500 μm across, being relatively abundant in the massive sulphide ore with cubanite-chalcopyrite and pyrrhotite-chalcopyrite assemblages.
In this study, chemical compositions of the Kamaishi pentlandites with various modes of occurrence have been determined using an electron microprobe. The pentlandites vary in their compositions over a wide range from cobaltian pentlandite to cobaltpentlandite, although Ni to Fe atomic ratios are usually close to unity with few exceptions. Their optical and other physical properties including X-ray data are also presented. The relationship between the physical and chemical data is examined. Finally the variation in chemical composition of the pentlandites is discussed in correlation with the difference in mode of occurrence and mineral assemblage.

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The Ohe ore deposits, occurring in the Miocene volcanic pyroclastics and quartz diorite of the "Green Tuff" region in southwestern Hokkaido, belong to the epithermal fissure-filling vein-type of polymetallic character.
This paper presents the data concerning the stages of mineralization, variation in metal content of the ores, ore mineralogy and fluid inclusions, mainly obtained for the representative Senzai vein.
Four stages of mineralization can be discriminated based upon the structural and mineral paragenetic features of the vein. Among them Stages II and III represent the main mineralization, depositing major sulphides of Fe, Cu, Zn, Pb as well as rhodochrosite with various minor sulphides, Au-Ag minerals, Mn-minerals and wolframite. The Senzai vein has 6 major ore zones that have resulted from lateral and vertical changes in its mineralogy and metal content.
The ranges of the homogenization temperature and salinity of fluid inclusions in the minerals of Stage II are 195°-314°C(259°C on the average), and 4.2-6.3wt.% (4.5wt.% on the average) equivalent to NaCl, respectively. The corresponding data for Stage III mineralization are 171°-285°C(211°C), and 1.6-3.1wt.% (2.5wt.%). Temperature gradients of the ore deposition are approximately 0.6°C and 1.5°C per 10 m at Stages II and III, respectively.
The sulphur fugacity and the temperature estimated for a representative phase of the mineralization are in the range of 10 ^-15 to 10^-11 atm., and 187°-275°C, respectively.

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More than five hundred data of nickel and cobalt contents in igneous rocks have been collected from the literatures, and the data are plotted on three diagrams of SiO₂-log Ni, SiO₂-log Co, and log Ni-log Co. Ni content of igneous rocks is higher in continental regions as compared with oceanic regions.The groups, continental and oceanic, can be discriminated on SiO₂-log Ni and log Ni-log Co plots. The boundary between them passes through the points; SiO₂ 40%, Ni 900 ppm, and SiO₂ 70%, Ni 9 ppm on SiO₂-log Ni diagram, or it has ratio of Co/Ni=0.16. Some data from the continental region are plotted in the area of the oceanic group. There is indication that their actual formative environment may be oceanic rather than continental. The data of the submarine volcanics associated with stratabound ore deposits in Japan, such as Kieslager and Kuroko, show the oceanic feature. It is concluded that the nickel content of igenous rock is a convenient tool for discrinimating the regional geological environment in which the magmatism has occurred.

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The Miocene sediments in the Ani area contain coals and dispersed coaly particles. Reflectivity of vitrinite in core samples from boreholes was measured and the reflectivity gradients were determined. Vitrinite reflectivity increases rapidly with depth, and the reflectivity gradient reaches into 1.2% Rmxa oil/100m. This value of the gradient is anomalously high in comparison with the case of normal coalification. The reflectivity-depth curves in the boreholes indicate that the increase in vitrinite reflectivity is due to the thermal alteration caused by hidden intrusive body lying at a moderate depth. The pluton may be connected with the near-surface intrusive a bodies of dacite, which was intruded in middle Miocene times. Absence of a mosaic structure in thermally altered vitrinites indicates that the vitrinites were below bituminous rank at the time of the intrusion.

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The kuroko deposits of the Shakanai mine are restricted in occurrence to the following sedimentological and biostratigraphical settings:
1) Spatially, the deposits occur almost exclusively in the local sedimentary deeps or depressions with no significant influence of the coeval volcanic activity. It appears that the kuroko mineralization primarily took place in "calm" sedimentary environments in the region of active volcanism.
2) In the stratigraphic succession, they occur exclusively within a specific biostratigraphical horizon abundant in foraminifera fossils, i.e., Globorotalia-Hopkinsina-Prunopyle Zonule.
These observations would not only provide us with a fundamental exploration guide for the ores, but also have significant bearing on the problems of kuroko genesis.

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