The Taiheiyo coal mine is now working under the open sea off Kushiro city, Hokkaido. In this mine, the salt water often spouted out at working face since 1936. Recently, such spout became very dangerous as the mining area have extended to greater depths of the under-sea coal field.
The author has carefully observed the, spouting since 1948, and has drilled underground drainage wells since August 1955 to obtain the materials from the water reservoir.
The followings are rsumed from those observations on the spouting and the reservoir by means of the drainage wells:
1) There are two reservoir horizons. The one is in the medium to coarse Tertiary sandstone in the basal part of the Harutori coal-bearing formation, and the other is in the hard fine Cretaceous sandstone.
2) Both Tertiary and Cretaceous roservoir are of fissure type, and extend in the definite horizon, and spouting may occur mainly in water-filled rock fissures.
3) The spouted water comes from the connate water included originally in the rock, and is not admixed with fresh water from the surface or with marine water.
4) Pressure of the reservoir-water increases with the depth. Gauged reservoir pressure at the top of drainage wells is about 60 per cent of the hydrostatic pressure.
5) The content of Cl in the water corresponds to reservoir depth and possibly to the caluculated contents of CaCL₂ and NaCl.
6) Temperature of water in the Cretaceous reservoir is higher than that of the Tertiary one at the same depth, and a true thickness of the Cretaceous reservoir is assumed to be larger.than the observed thickness.
7) The gas-water ratio in the water at the casing head is observed as 0.3 and the gas contains 93% CH₄. The gas can be separated by casing head and utiliged.
8) It is possible to control the reservoir water by means of drainage well drilling to prevent the water spouting.

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The Okuzu mine is one of the mines working the beds of the Neogene Tertiary of the Inner Zone of Northeast Japan, and is located immediately to the west of the Osarizawa mine. A thick formation of the Miocene "Green Tuff" is widely distributed as the basement complex of the area. It is covered or intruded by various volcanic rocks.
The ore deposits of the Okuzu mine occur chiefly in the "Green Tuff" and the mushroom-shaped dacite body, intruded along the anticlinal part of the "Green Tuff " formation.
The Mitate vein is a typical chlorite-quartz-copper vein, consisting of pyrite, pyrrhotite, bismuthinite, chalcopyrite, sphalerite, galena, native gold, and silver minerals accompanied by chlorite, quartz and calcite.
The association and texture of ore minerals are as follows;
1) Pyrrhotite and bismuthinite in massive chalcopyrite.
2) Native gold is especially associated with bismuthinite.
3) Emulsion sphalerite is in massive chalcopyrite.
4) Emulsion chalcopyrite is in sphalerite.
Based on the paragenesis, association and texture of ore minerals, it is highly probable that the Mitate vein was formed under high temperature conditions (xenothermal condition) prevailing in the Inner Zone of Northeast Japan.

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The Motoyama ore deposits of the Kosaka mine belong to the 'Kuroko (Black ore)' type deposits. They are almost conformable with the bedding of the country rocks. The Kuroko (Black ore) consists mainly of sphalerite, galena, and barite. It occurs in the uppermost horizon of the Motoyama tuff breccia formation which is composed of alternation of sandy tuff and rhyolitic volcanic breccia. The Kuroko is classified into two types in the texture, i. e., stratified (or banded) and breccia-like (or blocky) ores. The stratified ore characterized by well-developed colloform texture in pyrite occurs in, or alternating with, sandy tuff. In the mode of occurrence and texture, the breccia-like ore is very similar to volcanic bomb which is found in the former and also in rhyolitic volcanic breccia.
Judging from these evidences, it seems that the condition of the deposition of Kuroko was substantially the same as that of the sedimentation of the Motoyama tuff breccia formation. Then, it is possible that the materials of the Motoyama ore deposits were syngenetically derived from submarine volcanism.

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The writer has studied the occurrence of the gypsum deposits accompanied by the Kuroko (Brack ore) deposits. The conclusions are follows.
1. The hydrothemal gypsum deposits of the Wanibuchi mine occur as the bedded deposits. But they do not exist in the same horizon.
2. The crystallization stage of the spherical or massive anhydrite is earlier than that of the metallic minerals.
3. The anhydrite alters to the gypsum by hydration, as the temperature falls.
4. The stage of the formation of gypsum vein is same as the hydration stage.
5. The volumetric changes are caused by the hydration of anhydrite.

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The Hi-no-oku ore-deposits are of the bedded cupriferous iron sulfide deposits type and occur generally along the schistosity plane of green schist of the Kawaguchi formation in the Sanbagawa metamorphic zone, Shikoku.
The ore minerals consist chiefly of pyrite, chalcopyrite and pyrrhotite. The ore is rich in pyrrhotite, wich is somewhat different from other ordinary bedded cupriferous iron sulfide deposits in the Sanbagawa metamorphic zone. This kind of deposits is, however, commonly found also in the same zone as the Hi-no-oku ore-deposits.
The colloform texture of pyrite, the intergrowth of pyrite and magnetite, and pyrite and marcasite pseudomorph after pyrrhotite are observed. These textures are found only in pyrrhotite-bearing ores and seem to be secondary texture due to alteration of pyrrhotite.
The writer thinks that there are two types of occurrence of colloform pyrite in the bedded cupriferous iron sulfide deposits ; one is primary type occurring in weakly metamorphosed area, and the other is secondary type occurring in association with pyrrhotite. In the latter case, the country rocks vary in grade of metamorphism.
'Colloform' pyrite and marcasite in the Hi-no-oku ore-deposits may have been. formed by the retrogressive metamorphism in the later stage of the Sanbagawa metamorphism.

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The Takane mine is about 20km northeast of Murakami city, Niigata prefecture. This mine was worked in the wartime as a minor producer of molybdenite.
Uranium is detected from a small clayey veinlet of dark grey materials in the crushed silicified granite, the so-called Kogawa-type granite. This granite has a considerably high radioactivity, and a radioactive anormaly is also found in the basal part of Neogene Tertiary sediments, i. e. in the Tsugawa formation resting unconformably on the granite.
Based on the facts stated above, the Takane area and its vicinity can be favorable for the occurrence of sedimentary type uranium like other areas around the Uetsu massif.

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[in Japanese]

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