The Kohnomai mine, the greatest gold deposits in Japan is situated in the northeast part of Hokkaido island. The ore deposits are of epithermal fissure-filling Au-Ag veins occurring in the sedimentary rocks (tuff, mudstone and shale) and volcanic rocks (propylite and rhyolite) of Miocene age. The area is divided into three blocks by two shearing fractures trending N35°-45°E direction. The volcanic activities occurred in these blocks, being controlled by the fractures of second order which originated from the master fractures, and the deposits are closely related to the andesitic activities. The fractures of second order standing at 45 degrees with the master shearing fractures are predominate in the northern parts and some radial arrangements of fractures caused by doming in the southern parts. The representative deposits filling the former fractures are the No. 5 and the Sanno deposits while the Sumiyoshi, Motoyama and Fujishima deposits are of the latter. The No. 8 and Toyoshima deposits are formed along the shearing fractures.

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Exploration of the Inakuraishi mine has been developed remarkably since 1955. As a result of prospectings, it was found that the fractures in this area may be divided into three types by their attitudes.
1) [I] system……master fault striking NW_SE direction.
2) [IIa] system……secondary tention fracture with NW_SE direction.
3) [IIb] system……secondary tention fracture with NE_SW direction.
The writers describe vein pattern and ore shoot of this mining area, as related to the geologic structure.

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The newly designed thin wall diamond bit with specially prepared core barrel of which inner diameter is 27.00mm instead of conventional 21.46mm for 38mm outer diameter of EX size has many advantages. This tool increases in drilling speed from 3-5cm/min to 5-15cm/min, and decreases in troubles caused from core blocking, still keeping good balance for each parts, and as the result, getting 158% up on metres per drill shift. This new bit could be used for drilling of any hard or semihard rocks.

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Deposits of the Toyoha Mine are composed of many fissure-filling veins. Main ore minerals are galena, sphalerite, pyrite and manganese minerals. Fissures and. mineralizations of these veins are classified into two stages, the early and later ones. There are two kinds of fissures in the early stage. One of them occurs along the E_W trend sheared zone and the other is tension cracks of NW_SE trend. The minerals of early stage mineralization are quartz, galena, sphalerite and pyrite. The later stage veins are composed of the combination of fissures with NW_SE and E_W trends. Ore minerals of the later mineralization are abundant manganese minerals, coarse-graimed galena and sphalerite with minor silver minerals, pyrrhotite, stibnite, chalcopyrite and barite.

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The ore deposits of the Tatsumata and Akarimata mines are the complex veins composed of the xenothermal and epithermal type veins. The igneous activity related most closely to the formation of those ore deposits is the "volcanoplutonism" in the middle-late Nishikurozawa stage. During the activity in the Nishikurozawa stage liparite lavas flowed on one hand and the holocrystalline rocks intruded on the other. Location of the intrusion of holocrystalline rocks was governed by the folding structure. Formation of ore-shoot in fissure-filling vein was controlled by the shearing cracks due to thrusting or depression accompanying to the igneous intrusion and by the tension cracks formed by the lateral pressure accompanying to the folding movement. Therefore, the major veins occur always in dome or anticline in the complicated anticlinorium.

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The Myoho mine is located in the southern part of Kii peninsula, southwestern Japan. Geology of the mine area consists of sandstone, shale and breccia of Miocene age, and of the Kumano acidic igneous, complex. The Miocene formation is divided into K, A, B and C beds in ascending order. The ore deposits of the mine are chalcopyrite-pyrite-calcite-quartz-chlorite veins, partially containing chalcocite, bornite, sphalerite and galena, in the Miocene formation, The ore shoots are mostly bound in sandstone of C bed. The Kumano acidic igneous complex consists of rhyolite and granite porphyry. The rhyolite forms a large ring dike. It runs at the northern part of the mine. where it branches off several minor dikes. Vein fractures are intimately related to the, ring dike and the branches., Granite porphyry covers the Miocene formation and forms a part of the ring dike. The igneous rocks intruded and extruded prior to the vein formation. The ore deposits were formed in three stages; 1 st stage : Deposition of pyrite, calcite, quartz and chlorite with small amount of chalcopyrite ; 2 nd stage : Deposition of chalcopyrite, pyrite, calcite, quartz and chlorite ; and 3rd stage : Deposition of chalcocite, bornite, chalcopyrite and pyrite.

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The Yamato mercury mine is located in the central part of Nara Prefecture and one of the oldest mercury mines in Japan. The mine area is composed of plutonic rocks and mylonitic rocks of the post-Palaeozoic period, Tertiary quartz andesite and Quaternary sediments. The ore deposits of this mine are controlled by fissure systems such as EW and NW striking shear fractures, and WNW striking tentional fractures which are considered to be formed by the compression of WNW-ESE direction that is connected closely with the movement of the Median Tectonic Line. The ore deposits exist as a group of stringers, ore-pipe and pocket filling these fissure systems. The main Alterations of the country rocks are silicification, argillization, pyritization, carbonatization and chloritization. Ore shoots are formed where the fissures and veins cross, or where they dip at a low angle. It is considered that these ore shoots are controlled by structures of the fissures and the country rock.

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The Kishu mine, where the output of copper ore is about 27, 000 tons a month, is situated in the southern part of Mie Prefecture. The rocks around the main area of the mine consist of sandstones and shales of the Miyai group which is of middle Miocene age. The fissures in which ore deposits were are divided into three groups, namely, N-S, NW-SE and E-W group in their strike. On the other hand, four stages of mineralization in the main district can be recognized. They are Cu-Py, Pb-Zn, Au-Ag and calcite stages. The first is the most important. In the northern area, the Yunokuchi and the Hakko district, ore shoots were formed in the C member (medium sandstone) of the Itaya formation that belongs to the Miyai group, generally extending along bedding planes. The recent exploration in the southern area, the Kiyadani and the Josen district gave us some information on the shape of ore shoot of another type. The ore shoots of this type occur more vertically to the bedding planes.

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The Sazare mine is one of bedded cupriferous pyritic deposits occurring in the Sambagawa crystalline schists in the central Shikoku, and is well noted for the peculiar oblique intersection at high angle between the axis of ore shoot parallel to the unusual lineation in southwest direction and the regionally prevailing linear trend in the area.
For the purpose of prospecting the lower extension of the known ore bodies, and of finding new ore body, morphological and structrual analyses of both ore bodies and country rocks were made.
Planar and linear structures of the Kinsha ore body were analyzed and described on several levels, and the study of special features of "Sazare fold" was made in the western cross-cut on the 24th level.
The conclusion is as follows : (1) The ore bodies are morphologically classified into two types, named type I and type II. The former is a typical bedded deposit having a simple planar or sheetlike feature. The latter is an irregular shaped one with complicate foldings, and sometimes is called massive rather than planar. Authors consider that type I is a deformed equivalent of type II by later. tectonic movement. (2) Sazare fold is a kind of isoclinal fold plunging 40° in southwest direction with an axial plane trending east-westerly and dipping 40-45 to the south. This fold is considered to have 'been originally formed in the stage of the formation of the high angle lineation which plunges southwestwards and reformed by the later tectonic movement in which the transformation of the ore bodies was involved. (3) Kinsha ore body and Sazare fold are in close interrelation both in the original state and the later tectonic movement.

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The Kushikino mine which is one of the leading gold-silver producer in Japan is located in the Hokusatsu gold deposits area, Kagoshima Prefecture, Japan.
In Kushikino mine, more than twenty gold-silver quartz veins are found in propylite, which is probably of Miocene in age.
Main fractures are classified into following three groups :
strike dip
I N45°-65°E 40°E (shear fracture)
II N40°W 70°E (do)
III EW 35°SE (tension fracture)
The trend of main veins are controled by the two sets of fractures (the shear fracture I and the tension fructure III), which are linked each other.
Those tension fractures in the main veins are generally high grade, but the shear fractures I are of mostly low grade.
The several main veins in Kushikino mine, are distributed in the NW shearing trend.
The direction of each principal stress read from the vein patterns of the Kushikino mine and several other mines in the district, is closely related to the direction of warped folding axis in the basement rock (mesozoic and palaeozoic formations).

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Taishu mine, well known as one of the high-grade lead-zinc deposits in Japan, is located in Tsushima islands, Nagasaki Prefecture, Japan. The ore deposits are of mesothermal or xenothermal veins of the late Miocene age, composing predominantly of galena, sphalerite and pyrrhotite with minor amo-unts of chalcopyrite, arsenopyrite and pyrite. There are two-type veins in the Taishu mine, that is N-S veins occurring in the N-S normal faults and bedding plane veins formed in the bedding plane faults. Bedding plane fault is reverse fault being developed along the bedding plane in sandstone and alternation of sandstone and shale, and was formed at the same age when the Taishu formation of the Tertiary age was folded prior to the N-S normal fault. The following places are favorable to the formation of ore shoot in sandstone.
(1) The curved part of strike where strike of sandstone shows nearly N-S direction, whereas general strike is N35°E.
(2) The low dipped part where dip of sandstone shows about 15°-20° E, whereas general dip is 35°E.
(3) The part where shear fracture or tension fracture of the second order is developed in sandstone.
(4) The part where drag fold accompanied by the bedding plane fault is developed in sandstone.
(5) The part where the N-S normal fault intersects sandstone.
Therefore, ore shoot in sandstone on a large scale was formed in places wheres many abovementi-oned structures occurred overlappingly. It seems that mineralizing solution penetrated into the N-S normal fault after firstly ascended through the bedding plane fault, and then deposited the bedding plane deposits and N-S deposits. As a result of prospecting since 1962 based on the abovementioned analysis on the structural controls, new bedding plane ore bodies have been discovered.

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The Condenstable mine is located in central Peru, South America. The monthly production is about 7, 500 tons of crude ore with a grades of 2.8% copper. Rocks in the Condestable area are sedimentary rocks of Jurassic-Cretaceous and basic igneous rocks of Cretaceous-early Tertiary age. Ore deposits of the mine are classified into two types, one is the hydrothermal metasomatic vein type (the Manto type) and the other is the fissure-filling vein type. The former occurs in shear zones in the porphyrite near the contact with the diabase or sedimentary rocks. Ore minerals are chalcopyrite, pyrite, pyrrhotite, magnetite, atacamite, malachite, chrysocolla, etc., and skarn minerals are actinolite, tremolite, epidote and chlorite.

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