The authors restudied the zonal distribution of ore contents in the Mozumi mining area, using the distribution of ρPb defined as Pb%÷(Pb%+Zn%)×100 and other methods. The results are as follows.
1) From the ρPb distribution, it is suggested that there are two mineralized zones in the Mozumi mining area. The relation between the ρPb distribution and grade-and-size of ore deposits indicates that there were three stages of the mineralization.
2) It had been predicted from the ρPb distribution by the authors that there should be a new mineralized zone in the periphery of the Mochigakabe granite porphyries, located in the footwal.l side of the Kita No. 20 fault. We believe the orebodies being found at -500 meter level may be parts of the predicted ore deposits.
3) It is evident that ρPb method is quite practical for the prospecting of ore deposits at least in the Kamioka mine. But in the zones as low as below 10 of ρPb value, the zonal distribution is not clear and it is recommended to apply other indicator for the prospecting in such zones.
4) Iron content in sphalerite increases towards the outer zone of the mineralization. It is thought by the authors that this is because pressure decrease played more important role than temperature change during the formation of sphalerite minerals.

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The Akagane mine is well known for the typical contact-pyrometasomatic copper and iron deposits, the mine is located in the southern part of Kitakami mountains.
The deposit shows the following geological characteristics:
(1) There are two types of ore bodies; one is massive ore bodies in the Carboniferous limestone layers, and the other includes disseminated or vein type deposits in quartz porphyry or gabbro.
(2) The mineralizations are controlled by several geological structures such. as configuration of limestone layers, fissure systems and shape of igneous stocks. Individual unit ore bodies have comparatively small size, 30-300 thousands tons, and occur in various shapes, massive lenses, veins, or disseminations.
(3) Average grade of ores (1968-1972) is 0.68%Cu, 22%Fe, 5%S, 1.0g/tAu, and 10g/tAg.
Principal results of the prospecting for the last7 years are as follows.
(1) In the Sakae-Seibu deposit ores were found in the contact zone of limestone and gabbro and also within gabbro. Hozumi and Akagane-Kita deposits were found in the skarn zones by tracing geological structures.
(2) The IP method combined with magnetic survey has been effective, especially for distinguishing the deposits from the igneous stocks with strong magnetism.
(3) Occurrences of some valuable minor mineral components such as gold, silver, bismuth and tungsten in the ores were clarified.

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The deposits of the Yaguki mine consist of massive or disseminated iron, copper and tungsten ores. The deposits are of typical contact metasomatic type and occur in an extensive skarn zone which is formed along the footwall side of gently folded limestone bed. The skarn zone consists mainly of garnet skarn in the lower part and of clinopyroxene skarn in the upper part. Principal ore minerals are magnetite, chalcopyrite, pyrrhotite and scheelite. Sulphide and scheelite mineralizations seem to have been introduced by hydrothermal sulutions in the last stage of contact metasomatism which is closely related to granodiorite intrusion.
In the Shin-bu tungsten deposit, the scheelite mineralized zone is divided into five subzones from bottom to top as follows based on the mineral assemblages and modes of occurrence: A. massive epidotized subzone, B. epidote-quartz network subzone, C. massive and lenticular sericite-quartz subzone, D. banded and stratiform chlorite-quartz subzone, and E. epidote network subzone. The B subzone is included in A subzone and E subzone grades to limestone. The B and C subzones are most intensely mineralized by scheelite.
The scheelite mineralization took place in two stages. In the first stage A subzone was formed in following successive mineralization; clinopyroxene in skarn zone was partly replaced by actinolite, actinolite was in turn replaced by epidote and scheelite, then scheelite, calcite and quartz were precipitated. Later remaining clinopyroxene and actinolite were replaced by chlorite. In this stage only the clinopyroxene skarn was attacked by hydrothermal solution. It is likely that the mineralization occurred homogeneously in the skarn and gradually advanced upward. The scheelite mineralization is not associated clearly with much quartz and calcite but closely related to pistacitic epidotization.
In the second stage, B, C, D, and E subzones were formed. The epidotized clino-pyroxene of A subzone seems to have become more stable in this stage. Hydrothermal solution ascending through numerous cracks in skarn reached just below the limestone bed and mineralization occurred there. Fractured part of A subzone was also replaced by clinozoicitic epidote, sericeite, chorite, quartz and calcite in the main period of the second stage. Toward the end of the second stage, even limestone was replaced by much of quartz, chlorite, and sericite. The replacement in this stage indicates typical hydrothermal characteristics and scheelite mineralization is closely associated with epidotization and sericitization.

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The Fujigatani mine is located in Kuga District, Yamaguchi Prefecture. Palaezoic formation is composed of slate, chert, sandstone and limestone. The formation shows a synclinal structure and is intruded by granitic rocks. A number of small mineralized limestone lenses interbedded with slate and chert are distributed in a distinct horizon at intervals of 150-300m in the synclinal concave.
Skarnization is developed in the rim around lenticular limestone bodies and hydrothermal quartz veins occur in fractures in the limestone. Although scheelite mineralization continued from high temperature metasomatic stage or skarnization stage to hydrothermal stage which produced quartz veins, the latter was more intense mineralization stage for scheelite.

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[in Japanese]

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The Dowa Mining Co., Ltd. carried out an exploration program at Matachewan area, East Canada using Helicopterborne Electromagnetic system for the first stage of the program in 1971.
The aim of this program was to find out massive sulfide orebodies in Canadian Shield with thin surface cover of glacial deposits.
We used DIGHEM system for this work which has three receiving coils with perpendicular orientations to each other. We believe that this system is superior to other systems in the discrimination and the resolution between conductors.
As the results of DIGHEM survey in this program, we picked up twenty target areas from the record for the next stage program. After the cover of ground follow-up survey for each of those target areas, sixteen angle diamond drill holes (average length 100m) were completed in the eleven target areas.
All of those drill holes intersected more or less amount of uneconomic pyrite, pyrrhotite or magnetite mineralization just below the zone of conductive bedrock detected by DIGHEM and ground EM survey.
We have not discovered the economical ore deposit, but this result makes our confidence stronger about the prospecting approach mainly based on geophysical methods.

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The Kurikoma district is located in the volcanic region of the northeastern part of Japan, and is well known as a hot-spring area.
The Dowa Mining Co., Ltd. organized exploration team for the geothermal area in 1972, and geological and geophysical works were made and also five drill holes were sunk up to the end of 1974. The drilling techniques adopted for this area are described in this paper in comparison with ordinary techniques for the exploration of mineral deposits.

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Diabase sheets and pillow lavas in which the Shimokawa bedded cupriferous iron sulphide deposits occur are shown to be chemically quite similar to abyssal or oceanic ridge tholeiite. It is suggested that the origin and geologic setting of these tholeiitic rocks are comparable to those of “geosynclinal basalt”in the Palaeozoic formation in southwest and central Japan, although Shimokawa tholeiitic rocks occur in the Hidaka Geosyncline of the Mesozoic time.
Variation of major, some minor and trace element abundances of diabase within each single sheet was revealed, and discussed in terms of magmatic differentiation. It seems that diabase sheets above the ores are less differenciated than sheets below the ore horizon.

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At the Chitose mine, subvolcanic hydrothermal Au-Ag quartz veins occur in a propylitic volcanic complex. The emplacement of the deposits is controlled by fractures arranged en echelon fashion in the upper level and in cymoid loop in the middle. The deposits grade to simple veins in the lower level.
The flow directions of ore solution which produced the Fukujinzawa and Maizuru deposits were deduced by the analysis of the assay patterns.

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The Fukazawa kuroko deposits were discovered in the nearly central part of the socalled Hokuroku basin, northern Akita Prefecture, by drillings in 1969. The deposits consist of three main ore bodies and several small ones.
The following geological characteristics were revealed as a result of the development of the Tsunokakezawa ore body, one of the major ore bodies.
(1) The Tsunokakezawa ore body is a typical stratiform type kuroko deposit having lateral continuity. The ore body hardly shows any post-ore deformation.
(2) The ore body shows a vertical zonal arrangement, silicified rock, siliceous ore, gypsum ore, yellow ore, black ore, barite ore and ferruginous chert zone in ascending order.
(3) There are some isolated siliceous ore bodies accompanied by the yellow ore and the mineralized hanging wall basalt nearby.
(4) The nature of mineralization of the siliceous ore bodies alters gradually simple veins, network veins, network veins-impregnation and stratiform ores from bottom to top.
(5) The stratiform ore body is concordant with the thin bedded fine tuff of the hanging wall and the black mudstone of the footwall.
(6) In some places reworked sedimentary textures of the ores are found especially near the upper portion and marginal part of the ore body.

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Furutobe mine is located in the northern part of Akita Prefecture. The deposit of the mine is known as one of the typical Kuroko deposits occurring in the acidic pyroclastic rocks of Miocene age. The deposit shows following characters :
(1) A definite succession, siliceous ore, yellow ore, black ore, and ferruginous chert in ascending order, is seen in the deposit.
(2) Bedded sulphide ore occurring at the upper part of the deposit contains various fragments of ores and rocks.
Modes of occurrence of the siliceous ore and the results of its exploration are reported in this paper.
Siliceous ore is divided into two types on the basis of modes of occurrence and host rocks. One type of the siliceous ore occurs in rhyolite (lower siliceous ore zone) and the other in rhyolitic pyroclascic rocks (upper siliceous ore zone). The lower siliceous ore zone has cylindrical or tabular shape standing vertically. In the ore zone, a zonal distribution of ore-forming minerals, chalcopyrite zone, chalcopyrite-pyrite zone, and pyrite zone from center to periphery of the ore body is recognized. Silicification gradually becomes strong as approching to the central part of the mineralized zone. Clay minerals occurring in the mineralized zone are sericite and inter-stratified sericite/montmorillonite. Sericite is found mainly in the central part and interstratified sericite/montmorillonite is observed in general in the outer part of the ore zone.
The exploration was conducted on the basis of geological and mineralogical investigation and some ore bodies and bonanzas have been found in the lower siliceous ore zone.

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