The Ma On Shan Mine is a typical contact-metasomatic iron ore deposit in the New Territories of Hong Kong. The ore deposits occur in the skarn zone along the contact plane between the Mesozoic formation and granite instrusive, and the cupola of the granite controls the ore deposition. Most of skarn minerals are rich in magnesium : diopside mainly occurrs in the outer zone of the skarn area, and amphibole in the inner zone. The former is formed in an earlier stage and the latter in a later stage. A large quantity of magnetite is found in the diopside skarn and small quantities of sulphide minerals in the amphibole skarn. High-grade magnetite ore deposits are found in two zones, and there are barren amphibole skarn and thick dolomitic limestone between the two zones.
It is concluded that the original rock of the deposits was dolomite, such ingredients as FeO, Fe₂O₃, AL₂O₃ and F were added in large quantity, and CaO, MgO and CO₂ were lost.

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Up to date, many metal mines are using of circulating mud in prospecting diamond drills.
Since 1960, the writer has been experimenting on the circulating mud method. This paper explains the outline of the circulating mud method, adjustment of mud fluid and merits of this method as follows :
1. Increase in drilling speed.
2. Lowering of drilling cost per meter.
3. Prevention of hole wall caving.
4. Rapid and perfect removal of slime in the drill hole.
5. Mobilization of rods.

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The Omine Mine is located at about 20 km east of Tono City, Iwate Prefecture, or about 1.2 km northwest of the Sahinai iron ore deposit of the Kamaishi Mine.
Geology of the mine area consists of Permian slate, sandy slate, sandstone and hornfels, intruded by quartz diorite and granodiorite.
The genesis of the ore deposit is intimately related to the granodiorite intrusien. The deposit is a contact metasomatic-high temperature hydrothermal cupper ore deposit, and is characterized by abundant occurrence of cubanite along with chalcopyrite.
The skarn of the ore deposit comprises four types, namely, "banded skarn", "breccia skarn", "green skarn" and "garnet skarn". The "breccia skarn" characteristically contains a large amount of microcline in its brecciated part, and the ore is found in the green-tinted interspace of the breccia. The ore, occurring in network or impregnation, or forming veinlets, has high contents of gold and silver.
Prospecting is performed by geological survey, land survey and boring, keeping a close contact with the mining team. Recently the "underground wireline method" has been adopted to the boring work, by which the efficiency has been greatly raised.

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Results of geophysical prospectings for the pyrometasomatic zinc-lead deposits in the vicinity of the Kamioka mine since 1954, are summarized in this paper. Also details of the resistivity and magnet surveys in the Nakagoya area in 1963 are given.
Using both resistivtiy and magnet methods, skarn and graphite-rich limestone can be distinguished from gneiss and limestone including a great quantity of lenticular quartz mass, but it is very difficult to make distinction between ore skarn and barren one.
For developement of a more effective method, the writers are now testing the applicability of the I.P. method for the Kamioka-type deposits, getting considerably hopeful results.

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The Komori Mine is located in Kyoto Prefecture in the western part of Japan.
Geology of the mine area is composed of the Yakuno basic intrusives such as serpentine, gabbro, diabase, and the Palaeozoic formation (Permian system) consisting of hornfelsic slate, quartzite and sandstore, accompanied by granites.
The ore deposits are classified into two types, one being fissure-filling chalcopyrite-pyrrhotite vein in shear zone of the serpentine, the other massive chalcopyrite-pyrrhotite impregnated ore body which replaced diabase.

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The Osarizawa Mine is known as one of the largest mines of vein type in Japan. A group of the Tanosawa veins, located in the southern part of the Osarizawa Mine area, has recently been developed. The stratigraphical succession of this area is as follaws:
Upper Miocene : Matsukozawa Formation
-unconformity-
Middle Miocene : Wakiagari Formation
Shishizawa Formation (Upper and Lower Members)
These formations consist of pyroclastic rocks and mudstone. The volcanic rocks as observed are; Akasawa Rhyolite, Shishizawa Propylite, Akasawa Dacite; and Tanosawa Basalt. Mineralzation of the Tanosawa area appears to have taken place some after the Akasawa Dacite intrustion (late Onnagawa stage-early Funagawa stage).
Two prominent veins, Tanosawa veins 3 and 5, are in the group of the Tanosawa veins. These two veins show a pattern of the shear fracture. In other veins, a pattern of the tension fracture is observed.
It is interesting to note that the position of their bonanza has been controled by sedimentary rocks and intrusives. In regard to the zonal arrangement of ore minerals, the veins appear to be a type identical with that of the eastern vein groups of the Osarizawa Mine.
This is noticeable from the top to the bottom, namely, galena-sphalerite zone, chalcopyrite-galena-sphalerite-pyrite-barite zone and chalcopyrite zone. It is extremely difficult to determine the temperature at which the ore deposits were formed, but it is estimated to be about 210°(C) from insufficient fluid inclusion data obtained by heating-stage method.

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The Iimori mine is one of the cupriferous pyrite deposits in southwestern Japan, well known throughout the country for its long continuous ore shoot measurable over 7, 000 meters. The mine area is composed of spotted crystalline schists of the Sambagawa series arranged in a scaphoid structure with an east-west axis. The orebody of limori mine is situated in the northern wing of the structure, lying in the monoclinal zone which continues to the flat and wavy zone in the north.
The "Kuronendo" fault, cutting the orebody, was named after its black gouge when we encountered it in 1961. Our prospecting work principally aimed to know its exact nature and structural situation in relation to the orebody. It was finally ascertained that the fault took place near the boundary of two structural units, the "monoclinal zone" and the "flat and wavy zone, " forming a visible sheared zone due to shearing stress which was most probably caused by compression in the N-S direction with a horizontal dislocation of 350 meters.
In 1963, writers found the western extension of the dislocated ore shoot as a result of 1, 075 meters drift and 933 meters drilling.

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The Ryushoden Mine is located in the northern part of the Hidaka range, Hokkaido.
The mine area consists of sandstone and shale of the Pliocene formation (Yasoshi formation) unconformably overlying black slate and hard sandstone of the Cretaceous formation.
The ore minerals are cinnabars and a small amount of native mercury impregnated in sandstone.
The writer believes that ore shoot is controlled by porosity and breccia zone of the Yasoshi formation.
The existence of pre-ore fault is important for the genesis of these deposits.

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