Several copper orebodies are discovered in the deeper portion of the Mozumi mine during a recent development. Some results of the investigation on the geologic structure, mineralization and occurrence of ore minerals are summarized as follows:
1) The Mozumi ore deposits have been developed more than 900 meters in depth. A remarkably vertical zonal arrangement of the ore minerals is observed as follows; in descending order, none mineralized limestone, lead-zinc ore with calcite-quartz (shiroji ore), lead-zinc ore with skarn (mokuji ore), copper-zinc ore with skarn (mokuji ore), copper ore bearing pyrrhotite with skarn (mokuji ore), barren skarn.
2) Copper orebodies occur generally in the center of mineralized area.
3) Copper ores can be classified into four types by the mineral assemblage. It is observed that the mineral assemblage is simpler in the center of mineralization.
4) These copper orebodies are considered to be formed during two mineralization stages. The earlier mineralization stage was mainly lead-zinc, which was associated with small amount of copper. The mineralization of later stage which was overlapped to the earlier stage in some places, was mainly copper.
5) The main copper mineral is chalcopyrite. Generally in these copper orebodies, it is observed that sphalerite includes fine grained chalcopyrite and pyrrhotite as exsolution paragenesis
6) The iron content of sphalerite in copper orebodies are higher than that of sphalerite in lead-zinc orebodies.
7) Two types of pyrrhotite are recognized; One is a monoclinic type and another is a hexagonal type. The hexagonal pyrrhotite occurs usually in the center of the mineralization. In an orebody, the hexagonal pyrrhotite occurs usually at the core. In some cases, it is observed that these arrangements are disturbed and, microscopically, they show exsolution lamellae texture.

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Pyrometasomatic lead and zinc deposits at the Nakatatsu mine occur in skarn masses of the Paleozoic limestone. Main ore minerals are sphalerite, galena, pyrrhotite and magnetite. Subordinate ore minerals are chalcopyrite, molybdenite, etc. Regarding skarnization and mineralization at the mine, the following features have been clarified;
1) Three ore mineral zones of the inner Mt-Po zone, the intermediate Po-Cu-Zn-Pb-zone and the outer Zn-Pb zone are distinguished. These three zones seem to be arranged surrounding the quartz porphyry.
2) In the skarn masses, garnet zone and hedenbergite zone are recognized. The garnet skarn forms a dome at Nakayama deposits, and both skarn zones have a steep contact at Hitokata deposits.
3) Many ore deposits, especially high-grade and large-scale ore deposits, are localized in the hedenbergite skarn zone in the outer periphery of the garnet skarn zone.
4) The characters of the ore deposits, such as their situation, shape, scale, continuity, grade of ore and variety of ore minerals, are strongly controlled by the distribution of skarn minerals and the zonal distribution of ore minerals, as well as the geologic structure.
These features may suggest an important key to promote exploration works effectively.

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The oldest rocks of the Hirase mine area are various gneissose and granitic rocks of the so-called Hida Complex. They crop out in the northeastern and southwestern parts of this area. The Jurassic to Cretaceous Tedori Formation overlies these rocks uncomformably in the southwestern part of this area. The Cretaceous Nohi Rhyolites Group is most extensively distributed in this area. It is composed of acidic welded tuffs intercalated with rhyolite lava, its tuff and tuff breccia, and mudstone.
Granitic rocks, K-Ar ages of which are about 60 m.y., intrude the Nohi rhyolites. They crop out as several. stocks along the Sho-gawa (river) and are called "Shirakawa Granites." Fine-to medium-grained biotite granite and hornblende-biotite granodiorite are their major facies. The Shirakawa granitic rocks show contact aureoles in the surrounding Nohi rhyolites. Andalusite-bearing assemblage is seen around some of the plutons, such as Hatogaya and Hirase stocks. Dykes of quartz diorite porphyry, hornblende andesite, pyroxene andesite and basalt occur in these stocks mainly along fault zones.
Metamorphic rocks of the Hida complex thrust up to the Nohi rhyolites along the Morimo tectonic line. It strikes north-northwest. A similar fault zone passing through the Mihoro dum reservoir is called "Mihoro tectonic line." There are many faults of NW-trend diversing from the Mihoro tectonic line, some of which cut throngh the Hirase granitic stock.
There are many kinds of mineral deposits in the area, namely Cu-Pb-Zn veins in the Fcdori formation, Au-Ag quartz veins in the Nohi rhyolite, graphite deposits in the Hida complex and molybdenite-quartz veins in the Shirakawa stocks. Yet, only molybdenum deposits, those of the Hirase mine in particular, are productive. The Hirase mine is one of the most important molybdenite mines in Japan.
The Hirase deposits are composed of 29 molybdenite-quartz veins. The veins strike N-S to NNE and dip steeply west. Productive veins occur in the marginal part of the Hirase stock. The granitic rocks of this part are very heterogeneous and become homogenous toward the interior. The veins also become poor or thin out in the interior.
Molybdenite occurs along walls of quartz veins as fine-grained crystals or very coarse-grained cuhedral ones. The latter predominates in drusy parts of the quartz veins and accompanies coarse-grained calcite crystals in some places. Molybdenite seams occur in some parts of the altered Nohi rhyolites. Molybdenum grade of this ore is very low, 100 to 200 ppm, but the quantity is large. The amount of MoS₂ in the altered rhyolites at Kitani (about 3 km north of the Hirase mine) is estimated about twice as much as the total historical production of the Hirase mine. Molybdenites in any mode of occurrence have been recognized in rocks between the Morimo and Mihoro tectonic lines.

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The polymetallic ore deposits of the Akenobe Mine are of xenothermal type and are worked for copper, zinc, tin, and tungsten, owned by Mitsubishi Metal Corporation.
The mine area belongs to the Maizuru Folded Belt trending ENE-WSW, being composed mainly of the Permo-Carboniferous green rocks (basic lava and its tuff) at the lower part and slate. The green rocks crop out extensively at the eastern part of the Akenobe Fault, while at the western part black slate is predominant on the surface, which grades into the green rocks in the deeper part.
Igneous rocks in the area are composed of intrusive meta-gabbro and granite porphyry of the Triassic age (Yakuno complex). Granodiorite which belongs to the Miyazu granite of the Late-Cretaceous or Early Tertiary age also occur in the northeastern part of the area. The writers believe that ore deposits of the area are genetically related to this granite.
The geologic structure of the Paleozoic sedimentary rocks is characterized by two or three stages folding. The trend of the folding axis is roughly NE-SW, WNW-ESE and NW-SE. Dome structure has been recognized in the southern part of the mine. The fracture patterns including veins are characterized by NW-trending tension fractures dipping NE and also by NE-trending shears dipping NW in the eastern part of the mine.
In the western part the veins follow shear fractures parallel to the outer rim of the folded Palaeozoic rocks, making ring-shape arrangement. Many of these veins dip outwards, while those occurring in the inside of the ring structure dip inwards.
The fracture patterns formed by the latteral pressure that caused the fold structures are thought to be very complex. Based on the distribution of the lodes of the mining area, the writers guess that the vein fissures and faults were formed originally by the lateral compression in the older age, and then, some of them were removed by the stress due to upheaval of the granitic cryptobatholith in adjacent age of the mineral deposition.

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Some geochemical features of the diabase intrusives and lavas associated with the bedded cupriferous iron sulphide deposits of the Shimokawa Mine are preliminarily studied to obtain the key for the method of lithogeochemical exploration of the area.
About 850 samples of hand specimens from underground workings and drill cores were analyzed for twelve elements such as B, Co, Cr, Cu, Pb, Mg, Mn, Mo, Ni, Ti, V and Zn by emission spectrography.
Some notable features of the several minor and trace elements of diabasic rocks are found. The outline will be described as follows;
1) There are no remarkable difference between the coarse grained ophytic diabase and the fine grained variolitic diabase, and also between the fresh diabase and the altered one in regared to the contents of above mentioned minor and trace elements.
2) On each diabase sill and lava, especially on the coarse grained diabase sheet, contents of cobalt, magnesium, manganese, nickel and some other elements are increased towards the upper surface of the sheet and vanadium is increased towards the bottom.
3) These behaviors of the elements are observed in all diabase sheets, whether the sheet is associated with ore or not and also whether the sheet located above the ore or below the ore. Therefore these features suggest that the elements may have disparsed syngenetically.
4) There are some differences between the diabase sheet above the ore and below the ore in regard to the contents of several elements. Namely cobalt, nickel, and manganese are concentrated in the diabase sheets above the ore and vanadium is concentrated in the sheets below the ore.
This distribution mentioned above suggests the effect of "primary epigenetic dispersion" of geochemical elements associated with mineralization.
Therefore this epigenetic pattern can be applied to recognize the ore-horizon of the bed-ded cupriferous iron sulphide deposits associated with diabase sheets. In other words the diabase sheets with ore may be determined among many of the same kinds of sheets by the geochemical method.

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Distribution of the porphyry copper-molybdenum deposits in British Columbia, Canada, is confined to the area where eugeosynclinal volcanic rocks were developed during late Triassic and early Jurassic age. These volcanic rocks contain significant amount of copper minerals and syngenetic origin for this type of mineralization is now widely accepted. It is also noted that the contact type ore deposits, as well as "Kieslager" or volcanogenic ore deposits, have been found on a certain stratigraphic horizon of upper Triassic formations. The porphyry deposits, mostly located to the east of the quartz diorite line, are accompanied by the acidic to intermediate intrusions of the Nevadan or Laramide Orogeny. Regarding chemical composition, the typical porphyry deposits are associated with intrusions of calc-alkali suite but more alkalic suite is the case for the Copper Mountain deposits. Cu-Mo ratio is closely related to the mineral composition of intrutions. The deposits of higher copper content occur in close relation to the intrusions of which mineral composition ranges from granitic to quartz dioritic, while the intrusions associated with the porphyry "molybdenum" deposits are closer to the acidic extrimity in mineral composition. Hydrothermal alteration, typical for the porphyry mineralization, has been observed but alteration zoning has not been recognized in most of the deposits in British Columbia.
In conclusion, ore fluid for the porphyry copper deposits may have been formed in the process of crystallization differentation of magma which originated in relatively shallow depth of the earth's crust and assimilated those highly cupriferous formations of upper Triassic and lower Jurassic. Copper, with unusually larger ionic radius, precipitated as sulphides independent to rock forming minerals, while molybdenum, with similar ionic radius as of iron or magnesium, replaced ferro-magnesian elements of mafic minerals in relatively basic magma and precipitated as sulphides only in association with highly acidic magma.
The argument may be extended to the possiblity that metallic elements, one introduced in the earth's crust, repeat to form various types of ore deposits in accordance with geological events.

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The Kushikino mine, one of the largest gold-silver mines in Japan, is located in the south-western Kyushu gold deposits field, Kagoshima Prefecture, Japan. More than twenty veins are found in two pyroxene andesite lava and its pyroclastics of Miocene age. Tectonic movements of this district after the Miocene age are;
1) Deformation caused by NW-SE trends compression at the early Oligocene, which have brought the Hokusatsu bending structure and several faults with a trend of NW-SE.
2) Marine transgression from the middle Oligocene to the early Pleistocene.
3) Upheaval movement in the middle Pleistocene.
As a result of failures of the country rocks that have experienced different stresses, fracturings and mineralizations were happened following the next three stages. The first stage is semi-opaque quartz intrusion forming linked veins and intense silicification to the wall rocks. Fractures of this stage are closely related to warped folding of the country rocks with the axis direction of E-W or ENE.
In the second stage, milky quartz and calcite were deposited along the repeated cracks and fissures. Deposition of gold and silver took place in this stage, which shows crustification bandings, ring shapes and brecciated structure. It is considered that these cracks and fissures have been produced by the marine transgression immediatedly after the first stage mineralization.
The last stage is faulting which shows small displacement. This is chracterized by shear-ing and minor pyritization. The upheaval movement in the middle Pleistocene may have formed these shear faults.
General trends of the first stage veins are classified into the following three groups.
strike
N60°E
N40°W
N80°W
dip
40°-50°S
75°W
80°S
(thrust plane)
(normal stress plane)
(shear plane of second order)
Because of the tendency of reappearance of these veins at intervals of about 800 meters, vein pattern shows mesh-like arrangement in the mine area. Moreover, bonanza in the veins is controlled by the respective charactristics of each stage's vein structures. Based on interpretation of these geological peculiarities, exploration in the Kushikino mine area since 1968 has resulted discovery of Arakawa No. 3 vein and confirmed the lower parts of Arakawa No. 2 vein.

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The Takatama mine, situated in the southern part of Northeast Japan, has been in operation more than eighty years since 1890. Current exploration work is concentrated in the deeper parts of the mine. This paper describes a summary of the exploration and geological studies during the past several years.
Ore deposits of the mine are of epithermal Au-Ag quartz veins occurring in Neogene clastic and volcanic rocks, and also intrusive rhyolite. Nearly 1, 500 veins in total have been known. Ore minerals are electrum, pyrargyrite, cerargyrite, and native silver. Quartz and adularia are the main vein-forming minerals.
A few layers of gently-dipping clay beds occur in the mudstone horizon of the Neogene rocks. These beds generally confine the upper or lower limits of the vein swarms. Several bonanzas have been found just below these beds. Steeply-dipping sheared zones are another factor to control localization of bonanza. The so-called Kinton clay occurs in parts of the sheared zone. This clay is a good indicator of ores. The exploration work at the deeper levels also revealed shape of the intrusive rhyolite. This rhyolite seems to be related to the mineralization.

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The reverse circulating method was applied for vertical drill hole penetrating Neogene bedded-type uranium deposits (soft and loose) for the first time in Japan. The drilling was completed successfully by P.N.C. at the end of 1971.
In this method, the mud fluid is to circulate down along the outer side of drilling pipe and up through the inside bringing out cuttings and core to surface. A core kicker was developed to cut the core for suitable size. The drilling efficiency could be increased significantly with this method, because of continuous drilling without changing rods.

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