Recently, from 1969 to 1971, the new "black ore" -type deposits were discovered near the central part of the Hokuroku district, Akita Prefecture. The ores of about 3 million tons were confirmed by drillings, and it was named the "Fukazawa Ore Deposits", which consist of three main ore bodies with several small ones.
Until 1968, drillings for black ore deposits had never been done in this area. The authors previously investigated the geology of this area with geological information of the known black ore deposits, such as those at the Kosaka and the Hanaoka mine, and planed the drilling on the basis of the following ore indicators. They are the presence of :
(1) pyroclastic rocks in the ore horizon,
(2) volcanic activities in the Onnakawa and the Nishikurosawa stages,
(3) faults showing the structually weak zone,
(4) the dacite lava of the forerunning volcanism, and
(5) net work and impregnated ore deposits, for instance, those at "the Takarakura mine"
Geologically, the Fukazawa deposits are ore beds in the tuff breccia of the upper Nishikurosawa stage of the middle Miocene in age as similarly as other Kuroko deposits in the district. It has black ores as the main constituents, however, siliceous and gypsum ores are the accessories. The black ores can be classified into the following three types; a "compact type" consisting of mainly massive sphalerite, galena, barite, pyrite, chalcopyrite and tetrahedrite; a "broken type" consisting of the compact ore broken into breccia and sand ; and a "disseminated type" consisting of sphalerite and galena in matrix of the tuff breccia.
As shown by the result of the investigation on volcanic activities and sedimentation in the Miocene age, it became clear that the Fukazawa mineralization belt runs from the northwest to the southeast direction. The haloes of alteration of the pyroclastics in the area have been playing available role for exploration of black ore deposits.

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The Iwami mine is located in Isotake Machi, Ooda City, Shimane Prefecture, Western Honshu, and is producing black ore ("Kuroko") and gypsum.
The upper part of the black ore deposits is of bedded type and the lower part is of network and disseminated type. The gypsum deposits are found between these two deposits.
Since 1966 the lower network and disseminated deposits have been developed.
The following geologic features are found:
1) The Iwami deposits were embedded in the breccia pipe of the Yoneyama quartz andesite, which is believed to represent the earlier episode of volcanic activity in "Kuri" age of the Miocene.
2) Network and disseminated deposits are closely related to small bodies of rhyolite, which intruded repeatedly into the breccia pipe, and high copper concentration has been found in the periphery of the small rhyolite bodies.
The relationship of ore grade to host rocks such as small rhyolite bodies and enclosed various kinds of the brecciated rocks has been studied in detail. Based on those results, the exploration has been carried out and the new ore bodies, W No. 4 and W No. 6 deposits, have been found. Also the important areas to be explored are the periphery and deeper parts of the known ore bodies.
The mining plan and the grade control for network and disseminated deposits with extremely variable grades are successfully achieved by detailed study on character and occurrence of the host rocks, so that the stable mining operation has been maintained.

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On the basis of the studies of the geologic structure and the mode of mineralization, an intensive exploration work, accompanied with an application of the induced polarization method, was carried out since 1969 at the Inari adit area of the Ani Mine located in Akita Prefecture.
The main criteria drawn for the prospecting work can be summerized as follows :
1) As the past studies have revealed, basaltic rocks may play an important and favourable role for ore deposition and may sometimes control formation of bonanzas of veins which correspond to the extension of sheets and dykes of the basaltic rocks.
2) Anomalies of frequency effects of induced polarization will serve as indices to locate the area of mineralization and hydrothermal alteration.
3) Judging from the distribution of the resistivity values, trachyandesite will take the shape of a funnel at depth.
4) It is presumed that concentric fissures caused by intrusion of trachyandesite will exist around the center of the trachyandesite body.
As a result of exploratory adit works, some new blind copper viens were found at depth in the area covered by seemingly non-mineralized lava flows of trachyandesite and dacite.

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Pyrometasomatic lead and zinc deposits at the Nakatatsu mine, occur in skarn masses of the Paleozoic limestone. Regarding the geologic structure and mineralization of the ore deposits, the following features have been clarified;
1) The E-W trend faults, which are the most fundamental structure in the regional scale, are characterized by a vertical movement.
2) The N-S trend faults, which are characterized by a horizontal movement, have the character of echelon faults and have been related to the mineralization closely.
3) In the limestone beds, which show general trend of E-W to N 50°E and which are the host rocks of ore deposits, the folding structure of reverse Ω shape have been recognized. The plunge of the folding structure is 45°-50°to S 20°W. Ore deposits of the mine is strongly controlled by this geological structure.
4) Many ore deposits are localized in the hedenbergite skarn zone in the outer periphery of garnet skarn zone.
Based upon the above features, the relation, between the ore deposition and the geological structure have been verified, and consequently the exploration works have been carried out effectively.

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The recent exploration which was carried out at the lower levels of the Shimokawa mine has provided some favorable geological information which appears to warrant further prospecting.
Although the diabases occurring in this mine consist of various facies as observed by nacked eyes, it is noted that they are tholeiitic in chemical composition.
Amphibolization in diabase and sericitization in slate are characteristically predominant in this mining area.
The ore bodies are believed to occur along the boundary between crushed-diabase and phyllite. On the other hand, the distribution of minor elements in wall rocks and ore bodies indicates interesting features.
The relationships among altered rocks, mineral assemblages and ore bodies are as. follows:

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The Brenda mine, which is a low-grade copper and molybdenum deposit located at 5, 400 feet elevation some 17 miles northwest of Peachland, British Columbia, Canada, is now in full production at the rate of 24, 000 tons daily.
The area is composed of stratified tuffs, tuff breccias, argillites and limestones of the Nicola Group, and is intruded by a composite quartz diorite called Brenda Stock. The quartz diorite unit has been strongly fractured and the ore minerals, chalcopyrite and molybdenite with quartz stringers, occur as fillings of fractures. The grade of the Brenda ore body is wholly dependent upon the intensity of the fracturing.
The exploration and feasibility program, 1965-1967, have been conducted as follows;
1) Three AX and H diamond drill holes are compared with the 1956's EX holes.
2) An induced polarization survey is carried out in order to delineate the area containing sulphides.
3) Prelinary flotation tests are carried out using the crushed ores of H cores.
4) Diamond drilling of 74 B.Q. wire line drill holes totalling 42, 573 feet and rotarypercussion drilling of 19 holes totalling 7, 323 feet.
5) Bulk sampling : drifting 1, 475 feet, cross cutting 400 feet and 4 inclined raises 960 feet.
6) 100 tons per day pilot plant operations for the purpose of the flow sheet study and the mill design.
7) Ore reserve calculation estimating at 175, 000, 000 tons grading 0.183% Cu and. 0.049% Mo.
8) Economic studies and others.

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A geochemical exploration for copper ore was carried out over 7, 700km² in the Cordillera Central area of the Dominican Republic. The steps of the work were as follows; 1 st stage : Reconnaissance drainage sediments survey was applied in this stage. More than six thousand samples were collected (0.8 sample/km²) and analyzed for total copper and heavy metals, some for molybdenum as well. The results revealed 18 anomalies.
2 nd stage : The 11 anomalies were selected for detailed stream sediments survey, and about 7, 300 samples were collected from the area of 784km² (9 samples/km²).
3 rd stage : Preliminary geochemical soil surveys were carried out as a follow-up study on the favorable sections of about 57km² in total which were selected based on the results of the 2nd stage work.
4 th stage : Various kind of works, geological, geochemical and geophysical, including diamond drilling were done on the several targets chosen from the 3rd stage study area.
Some geochemical features obtained are discussed in this paper on the following items.
1. The relations between copper contents in stream sediments and geology of sample sites.
2. The relations between soil- and stream sediments anomalies.
3. The relations between soil- and bedrock anomalies.
In conclusion, such a geochemical investigation over the vast area is proved to be very serviceable even by single or two elements method, provided the objective ore of the exploration is fixed and the data are. suitably analyzed.

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The writer has studied the geochemical behavior of heavy metals, especially cadmium, in various kinds of rocks, natural and paddy soils, aud river and underground water throughout the Jintsu River area.
The results are summerized as follows :
(1) The amount of cadmium as well as zinc cotained in various rocks in the Jintsu River area is remarkably high, especially in the upper valley area, where many lead and zinc ore deposits had been found.
(2) The cadmium contents in natural soils are generally much higher than that in the original rocks.
Cadmium contents in soils of fine grain size is higher than in those of coarse grain size. Especially the finer particle of soil, suspended in river water, is extremely high in cadmium.
(3) The cadmium contents in soils from the river terrace or the down-stream fan are also remarkably high, reflecting the back ground of up-stream rocks and soils.
The eroded remnants from the outcrop of the ore deposits have also been found in the river terrace, which is supposed to be formed about 40, 000 years ago.
(4) Detailed geochemical soil survey has been carried out in the Toyama plain, a down-stream area of the Jintsu River, where the "Itai-Itai Byoo" disease had been localized.
The cadmium contents in soils are characteristically distributed in three different fan levels;and in the same fan levels the lower and swampy area is a little higher in cadmium content, as the finer particles of sediments were deposited during formation of the fan. Likewise, paddy soil contains more cadmium than other soil within the same fan level, as paddy had been made in lower and swampy area since the ancient time. Also the river water, which suspends finer particle of soil, has fed little additional cadmium into the paddy by irrigation for as long as 200 or 300 years.
Consequently the writer believes that the origin of cadmium in paddy soil in the down-stream area had mostly been derived from the environmental rocks during the sedimentary deposition of the fan and little addition from the irrigated river water for hundreds of years, but not for decades of years, when the mining operation might have influenced the pollution of the river water.

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