The Kosaka mine is located in the northern part of Akita Prefecture, and is well known for the Kuroko-type deposits, namely the Motoyama, the Uchinotai and the Uwamuki deposits. These deposits occur in the Miocene tuff breccia at the flank of the so-called white rhyolite, and consist of Kuroko(black ore), Oko(yellow ore), Keiko(siliceous ore) and gypsum ore, in descending order. The black ore and yellow ore bodies are generally bedded in form, while the siliceous ore and gypsum ore bodies are massive.
Recently, another type of siliseous ore body was discovered within the white rhyolite. It is a stockwork siliceous ore body having a cylindrical shape and standing vertically. Sulfide minerals occur in the mode of vein, micro-veinlet and dissemination in the ore body. Vertical zonal arrangement, sphalerite-galena-barite, sphalerite-chalcopyrite and pyrite in descending order, has been recognized. This sequence is the same as that found in common Kuroko deposits.
The stockwork siliceous ore deposits have been found in several places about 100 meters apart. The exploration of these deposits in the white rhyolite is now under way at the Kosaka mine.

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The gold-silver ore deposit has been discovered in the Tochibora mine area through the recent prospecting and here is given a summary of the several features of this deposit as follows ;
1) The gold-silver ore deposit occurs in the hydrothermally altered gneisses, adjacent to the skarn ore deposits. Gold and silver minerals are concentrated heavily in quartz veins and also disseminated weakly in the altered zone.
2) The emplacement of the gold-silver ore deposit is controlled by the general geo-logical structure, showing plunge of 26°-38° to SW, concordant with that of the surrounding skarn ore deposits.
3) The ore minerals of the deposit are mainly native gold and pyrargyrite, associated with galena, sphalerite, chalcopyrite, arsenopyrite and pyrite. The deposition of these minerals is considered to have succeeded the skarnization of the main Tochibora ore deposits, and tc represent the latest stage of the mineralization in this area.

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The Ooe-Inakuraishi mine, located in Shakotan Peninsula, southwestern part of Hokkaido Island has been known as a manganese producer.
The major geological units of this area are volcanic and pyroclastic formations of Miocene which are intercalated with thin beds of conglomerate, sandstone and shale. There are also intrusives of quartz diorite, basalt and dacite. The NW tectonic trend is predominant as shown by the folds and faults of the same direction.
The Ooe deposits consist of the veins which fill the several subparallel shear fractures of N50°-60°W trend as well as a great number of accompanied tension fractures with minor extension in N80°W direction. The wall rock is mostly quartz diorite, and the ore shoots are located near to the peripheral shell of the intrusive body.
The Inakuraishi deposits, the veins in the "propylitized" andesite, fill the shear fractures of N55°W trend, many tension fractures of small extension in N80°W direction and also fill the several fractures of N70°E trend of much greater extension. The occurrence of the shoots at the intersections of the two kinds of fractures are remarkable.
These two fracture systems may be interpreted as to depend upon the stress set up by the intrusion of the quartz diorite and to the horizontal stress which caused the folding too, respectively. The formation of the Ooe deposits are more closely related to the former stress, while the Inakuraishi deposits more closely to the latter.

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The Chaucha porphyry copper deposit, located in the northern Andean Cordillera of Azuay Province, Ecuador, is related to the quartz dioritic Andean batholith intruded in the Paleozoic metamorphics and "Diabase and porphyrite formation" of Cretaceous age. The intrusive complex is constituted of quartzdiorite, granodiorite, tonalite and quartz porphyry. The granodiorite batholith has an oval form in plan elongated along the regional northeast trend with 11 km major and 4 km minor axis. The tonalite stock shows nearly circular outline with 2.7 km diameter, and appears to have intruded in the southern margin of granodiorite. Then quartz porphyry emplaced in the southern part of the tonalite stock.
Weak mineralization occurs anywhere within the tonalite, not in quartz porphyry. Relatively intense primary mineralization is localized in tonalite side on the contact with Paleozoic quartzite and has been enriched forming chalcocite blanket of 800 m in length, 400 m in width and thickness of several tense of meters.
Characteristic alteration of the district, if it could be called alteration, is the extensively distributed recrystallized biotite clot which might relate with quartz porphyry intrusion, however, it does not show any direct relation to the mineralization. Other alteration pattern of the area is controlled by the outline of tonalite stock. The propylitic alteration more or less is ubiquitous in tonalite stock. In some part along tonalite boundary relatively sericitized propylitic rock develops. Main orebody occurs in such comparatively intense sericitized area, though even in the orebody half of the wall rock is still showing incomplete propylitic alteration. Neither potash silicate core, nor usual zonal arrangement of wall rock alteration around orebody is found.
P. E. DAMON determined the age of Chaucha deposit as 9.77 m. y. Minor supergene enrichment may be caused by the relatively recent emplacement.

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The "M.E.S" (Mine Evaluation System) is an integrated computer application system for mine evaluation designed to supply various data and estimation which are necessary for the feasibility study. This system is composed of a set of procedures as follows:
(1) Estimating grade distribution
(2) Assigning economic value for each mining block
(3) Designing ultimate pit
(4) Making mine schedule and evaluation
Drill core assays, topography and various economic conditions are input to the procedures and the judgement on the profitableness of the mine is finally settled through the D.C.F.(Discounted Cash Flow) methods. These procedures are carried out not only individually but also successively from the estimating grade distribution to D.C.F. under the control of the "M.E.S. "control language which is especially developed for this system. This system has several kinds of methods for the analysis designed to choose those that permit best use of methods according to the objective. Distance Weighting Method and Trend Surface Analysis for the estimation of grade distribution, and Graph Oriented Method, Dynamic Programing Method and Moving Multi-Cone Method for the ultimate pit design are put and set in this system
From September, 1973 to January, 1974 this system was applied to several projects. Two case histories are reported in this paper for gaining a better comprehension of this system; one is to check the adaptability of this system to idealized porphyry copper mine and the other is for analyzing the potentialities of a porphyry copper mine in Canada. These two trials prove dthree merits as follows:
(1) This system has complete flexiblility in applying to the different types of mines.
(2) It is very speedy and accurate in calculating to get the information and estimation for the mine.
(3) Any users can perform this system with a little knowledge of computer programing.

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The northern Hachimantai geothermal field is located in the backbone ranges at the northern parts of Akita and Iwate Prefectures. It has been explored and developed by Mitsubishi Metal. Corporation since 1965, and a 10 MW power plant is now under the testdriving.
The geophysical results obtained through the exploration may be summarized as follows:
1) The regional gravitational survey indicates that the geothermal field occupies a part of the regionally depressed zone along the western flank of the backbone ranges.
2) A remarkable negative anomaly is found in the depressed zone. This is considered an ancient caldera or crater.
3) The electrical survey reveals many occurrences of hydrothermal reservoir. A sheared zone confirmed by the seismic method is interpreted as the conduit for the geothermal water.

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The Tono uranium deposits were first detected by a carborne survey team of the Geological Survey of Japan in 1962. Following this discovery, exploration in the area has been carried out by the Power Reactor and Nuclear Fuel Development Corporation. There are four major uranium deposits so far discovered in the Tono district, namely Tsukiyoshi, Misano, Jorinji and Utozaka.
The basement of the area is composed of late Cretaceous to early Tertiary granites and Paleozoic rocks. The Neogene sedimentary rocks overlying the basement are stratigraphically divided into two groups, the Mizunami group of Miocene age and the Seto group of Pliocene age.
Uranium deposits are exclusively found in the Toki lignite-bearing formation of the Miziinami group, and their distribution is generally controlled by the so-called "channel structure". The "channel" is defined as shallow trough excavated on the erosional surface off the basement rocks by pre-Miocene streams. The most favourable position in the channel for the deposition of uranium is the bottom part, where conglomerate and/or coarse-grained sandstone are well developed as the permeable bed.
The principal uranium minerals found in the Tono district are as follows.
(1) Tetravalent uranium minerals; uraninite, coffinite.
(2) Hexavalent uranium minerals; autunite, uranocircite.
(3) Minerals adsorbing uranium; zeolite, montmorillonite, carbonaceous matter.
At the prospecting tunnel of the Tsukiyoshi ore deposits, uranium has been recognized mainly in such mineral as coffinite and uraniferous zeolite. Most of, the uranium in the ores are considered to be adsorbed by zeolite (heulandite-clino ptilolite group). Coffinite has been found as a main mineral of high grade ores, and usually accompanying pyrite and carbonaceous matter.

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An ore deposit of the so-called porphyry copper type has been found by the systematic and integrated exploration near Yauri town in Cuzco Prefecture, Southern Peru.
In 1970, airphoto and airborne magnetic surverys were conducted to extract possible ore zones in the vast area of about 12, 000km² and an area of 360km² including seven potential zones was picked up by these surveys.
This area was reduced to 50km² of three more favorable zones by the geological reconnaissance surveys, and finally a zone of the highest potentiality in the are was taken up by the detailed geological and geochemical surveys as well as by the induced polarization method. In 1973, disseminated sulphide ores were intersected by the diamond drillings. The present estimation of the ore reserves is several tens cf million tones of disseminated sulphide ores. This successful result gives an excellent example of a systematic and integrated approach of the exploration.
Due to the depth of the ore zone and the disseminated character of most of the ores, the induced polarization method was the only geophysical technique useful for the direct detection of the mineralized zone.
The usefulness of the IP method can be read by the correlation of the geological observation to the inferred structures interpreted from the IP data.

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For the purpose of saving time of the work to hoist up and down drill rods in each occasion exchanging drill bit, Sumitomo Metal Mining Co., Ltd. has manufactured trial equipments which enable to attach a drill bit to the top of an inner tube of a wire line core barrel. Exchange and examination of the bit can be done easily while operating the wire line. This is called the Retractable Drilling System (RDS), and has been tested for the drilling about 2000 m in total at 20 places.
A characteristic structure of the RDS is that a reaming bit attached to the lower part of the inner tube can be pulled into the inner tube when the inner tube is hoisted up in operating wire line.
Distinctive merits of the new system are to save working time substantially and to prevent the destruction of wall rock of a drill hole because it is not necessary to hoist up and down drill rods for exchanging a drill bit. A comparison with a conventional system has been made on drill holes up to 150 m in depth and the RDS has been proved to reduce the working time for drilling to the one-third of the conventional system.

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