Along the Hidaka metamorphic zone, which constitutes the geological back-bone of the Island of Hokkaido, several cupriferous iron sulphide deposits which indicate close connection to gabbroic or diabasic rocks are found. The Koryu mine described here is the representative. Around the mining area zonally arranged metamorphic and gabbroic rocks that resulted from the Alpine orogenic movements are developed.
The ore deposits consist of some variable small bodies which lie sporadically in a shear zone that has some peculiar alterations.
The ore bodies are divided into 1) massive ore body, 2) "Gari" or brecciated ore body and 3) impregnated ore body according to the nature of the ore. They are lenticular or layered in shape and are disposed en echelon in the shear zone. The constituent ore minerals are magnetite, pyrrhotite, chalcopyrite, and pyrite. Some silicate minerals such as bluish-green hornblende, diopside, anthophyllite, cummingtonite, chlorite, epidote, biotite and quartz are also present.
Mineralization of the deposits has proceeded under the influences of dynamic movement and closely related metasomatism. In an earlier stage, magnetite was formed; it was accompanied by Fe-Al metasomatism which is indicated by bluish-green hornblende in the wall rock. Formation of the succeeding sulphide minerals was associated with characteristic Fe-Mg metasomatism as suggested by the presence of anthophyllite and cummingtonite.
The differences between the ore types are probably due to the differing suscptibility of various areas in the shear zone resulting from dynamic movement accompanvinu the ore deposition.

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In Part I of this report, general conclusions were derived from the results of the geological survey and data of deep boring. The processes of formation of the deposits were explained and important previously unknown geological information concerning the prospecting in the ore body were obtained.
The main results are as follows:
(1) The shales accomplished the role of cap rock for the ore deposits.
(2) Fissures have no relation to the location of the ore shoot, there is no use tracing fissures in prospecting.
(3) It is not very important to trace stratigraphic structures of country rocks in prospecting.
(4) In the Matsuo mine, the determination of the position of a diffusion center from which the mineralizers emanated is most important.
(5) The form and location of the deposits depend upon the position of the diffusion center, and also upon the chemical and physical properties of the mineralizer.
(6) The deposits are assumed to be in the area bounded by a hanging wall having the shape of an oblate dome with the diffusion center as a locus and a foot wall parallel to the erosion surface on the underlying lava.
Therefore determination of the assumed limits of the ore body by the above principles is desirable before exploration by deep boring or drifting is undertaken.

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The Kamikita mine located in Aomori Prefecture, North Japan, is one of the most famous black, ore deposits in Japan. The ore deposits consist of several massive and layered epithermal replacement bodies in a breccia zone in liparite and liparitic tuff. The liparite and tuff are. genetically related to Miocene volcanic activity.
Ores of two kinds exist : One consists chiefly of pyrite, and the other, of sphalerite with small quantities of galena, bornite, chalcocite, chalcopyrite, tetrahedrite and other minerals.
The black ore of the First Kaminosawa deposit is very complicated. Ore minerals of this deposit are sphalerite, galena, chalcopyrite, pyrite, bornite, chalcocite, dienite, orange bornite, enargite, luzonite, tetrahedrite, tennantite, sternbergite.(?), stromeyerite (?), pyrargyrite and .occasionally at some places germanite (?) the gangue minerals are quartz, calcite, gypsum, chlorite, etc......
The ores of this mine contain very small amounts of germanium. The following results are obtained by microscope observations and chemical analyses:
(1) The contents of germanium in ores range considerably, from 0 to 280 g/t. Most germanium, is found in sphalerite (50-250 g/t); very little is present in other ore minerals, gangue minerals and the country rocks (less than 10 g/t). Fine grained germanite (?) is found in some sphalerite.
(2) The content of germanium in sphalerite is marked by difference' in the various deposits and depends upon the sequence of mineralization.
(3) A, concentrate of zinc (55. 91% Zn) containing 120 g/t Ge was, obtained by the differential flotation of zinc-copper ores from this mine.

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The Pre-Tertiary Basement underlying the coal-bearing strata, Hanakawa Formation developed in the Joban Coal-fields, often produces buried hills in the overlying beds. The development of workable coal seams have been greatly influenced by the existence of buried hills, namely, the main coal seams all tend to become thinner towards the hill and thin out completely over the top of the hill. These above mentioned events are economically important.
The following two methods were devised by the author to investigate the buried hills:
(1) From the porosity and density of drill core, the amount of closure reflected in the buried hill is approximately calculated by the following equation.
If a constant stress works perpendicular to the section of a cylinder composed of a homogeneous, porous medium, the equation may be expressed as H1/H2=V1/V2=(1-P2)/(1-P1), where H1. H2, V1. V2, P1. P2 denote respectively the height, volume, porosity before and after the stress is applied.
The author believes that these values can outline the area of investigation on the geological-map of this district.
(2) From the following abnormal sedimentation of the coal-bearing strata at the approach of the buried hill in the pit, the author has also tried to get a useful clue to fine it. The following was noted:
(i) The distance between two coal seams decreases from 6m to 0.5m in 300m of horizontal distance, the distance between two partings in the lower main coal seams decreases also from 0.5m to 0.1m for the same horizontal distance. Thus, each coal seams decreases in thickness from its lower part and abruptly or gradually thins out at.the top.
(ii) As the buried hill are mainly composed of amphibole schist and amphibolite, the surrounding coal-bearing strata are dominantly greenish schistose mudstone and contain many large schist fragments and calcite, derived from the schist.
(iii) The cyclothems developed in the coal-bearing strata change from complete ones to incomplete ones towards the buried hills.

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Rhythmic precipitation of a mineral may occur, not only by inward diffusion of solution into a reacting substance, but also by outward growth of precipitating material, due to intermittent coagulation of a substance in a colloidal medium. Zonal precipitation of different minerals may occur both by successive infiltration of different substances or by their simultaneous diffusion from a mixed solution into a reacting medium. In both cases, the order of succession of resultant zones is fixed according to the reacting materials, not by order of infiltration.

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The main object of this survey was to detect some effects of igneous intrusions on the coal-field, by measuring the relative amount of radioactivity of the coal-bearing strata. The measurements of radioactivity were performed both in the field and mines, using Philips' "Pocket Battery Monitor" PW 4010 (for β and γ). Relative radioactive intensity (count/minute) observed in coal mines. was generally as follows : lithoidite>roof shale, andesite> fault plane, water issuing in the mine>floor shale>basalt, sandstone slightly above the coal>background at the pit-mouth>coal, sandstone slightly below the coal. Radioactivity of these objects is highest in the Meiji Saga mine where the coal seam is locally intruded and disturbed by lithoidite intrusions, and is lowest in the Tateyama mine where no igneous intrusions are found in the mine. In the Meiji Saga mine, radioactivity of all subjects increases perceptibly within 10 meters or so of the lithoidite intrusion.

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