The Matsuo ore deposits are divided into sulphur ore deposit and iron-sulphide deposit according to free sulphur and combined sulphur contents respectively.
The sulphur ore deposit takes the shape of a mushroom, and the bottom of deposit seems to be controlled by the original surface of footwall rocks with a ship-bottom form originated in marsh.
It is 1, 500m in. width along E-W, and the plunge is about 10°E.
On the other hand, the iron-sulphide ore deposit assumes the form of an amoeba, and consists of four bodies, each of them covering an area of 20, 000-90, 000². The surface of the deposit is concordant with the structure of hanging wall rock in accordance with the topographical features.
The sulphur and iron-sulphide deposits maintain an oblique relation between them, but partially a mixed relation exists.
It appears that the sulphur metallization took place from the surface of lower lava bed, and diffused to the upper middle bed along a fissured zone of 300/100m² in area.
The iron-sulphide deposit was succesively formed outside the sulphur deposit in the upper layer of middle lava bed, and the surface complied with the geochemical and geomorphological conditions of hanging wall rock.

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1.The Suihei-Danso (Horizontal fault, literally translated), as conventionally named by geologists and engineers, occurs in many coal fields of Japan. It comprises two different sorts of fault-low-angle fault and strike-slip fault.
Low-angle faults may be grouped into the following two types:
A.Thrust fault and gravitational gliding which are originally horizontal or low-dipping (Fig.1).
B.Normal or reverse faults which originated as high-angle faults but turned low-angle through. the later crustal movement (Fig.2, 3, 4).
2.Strike-slip or wrench fault in which horizontal component is larger than the vertical one, is not uncommon, as shown by many examples in the Ishikari, Kushiro and Chikuho coal fields (Fig.7, 9-12, 14-18). It is highly probable that many more similar faults may be discovered if sufficient attention. be paid in studies of faults, because a shearing stress or a couple of stresses producing strike-slip faults is believed to have influenced the structural development of the coal fields in Japan during the late Tertiary.
3.As a reasonable suggestion for the condition of a coal seam in an area beyond a fault encountered is one of the important tasks of a coal mine geologist, it must be necessary to know the direction of shifting, at least, whether vertical or horizontal component is bigger than the other, before reaching a conclusion.
4.The following features may be taken up as important keys for detection of strike-slip faults:
(1) Occurrence of low-angle striae on the fault plane.
It must be noticed that the observed striae indicate, in most cases, only the direction of the last movement of the block concerned, and the fault movement is usually very complicated.
(2) Occurrence of auxiliary faults.
They are usually branching from the main fault with high angle, more than 60 degrees, sometimes at right angle to the strike of the main fault, and most of them are running parallel to each other. Their extensions are much shorter than that of the master fault.
They are always normal faults, their dip being not necessarily in the same direction, and the amount of vertical displacement becomes larger as they approach the main fault.
(3) Occurrence of horizontal drag.
In case of steeply dipping strata, the shape of horizontal drag which is expressed by a change of strike, immediately suggests a horizontal movement. But this cannot be taken as a good key in an area where the strata are gently dipping.
(4) Non-coincidence of geology between two blocks dislocated by a fault.
When geologic features of one block of a fault, irrespective to stratigraphic or structural natures, are corresponding but are discontinuous to those of the other block, that is, when those features of one block are same in order of aerial distribution but is being shifted in the same direction relative to the other one, they are probably regarded as evidences of a horizontal movement, if they cannot be interpreted by a rotational or a hinge fault.

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The writer, as a resident geologist, has been engaged in surveying and prospecting in the Besshf and Sazare mines in the Sanbagawa metamorphic zone, central Shikoku.
This area of the Sanbagawa series is composed of the oldest rocks, represented by the crystalline schists which comprise green schists, graphite schist, schistose sandstone and quartz schist. The green schists include epidote-chlorite schist, spotted chlorite schist, epidote-amphibole schist and spotted. amphibole schist.
In regard to the geologic structure of this area, there are two anticline-axes and one main syncline-axes running N 75°W. They are called the Yakushi anticline-axis, the Tomisato syncline-axis and the-Nakahichiban anticline-axis from north to south. Between the above anticline-axes, there is a large bilge, the so-called Tomisato syncline. According to the relations between the present topography and. the abovementioned geologic structures of this area the surface geology shows apparently a big sigmoid. form.
The metamorphic zone is composed of the following formations and is divided into some subzones by their metamorphic grade :
Name of formation
(upper) Tomisato
Minawa{upper middle lower
Koboke
Kawaguchi
(Lower) Oboke
Thickness
800m
4, 500m
500m
1, 200m
1, 500m
Metamorphic grade
high high middle}spotted zone
low low low low}non-spotted zone
Many bedded cupriferous pyrite deposits are found in the Kawaguchi and the Minawa formations, but the famous ore-deposits, for example, the Besshi, the Sazare and the Shirataki deposits, belong to the latter formation. The Besshi mine, above all, having had the output of 650, 000 tons of copper during the past 270 years, is well known as a representative of the Besshi type copper deposits or Kieslager type in Japan. Recently the Sazare mine has made a remarkable progress as a result of positive prospecting.
Scince 1895 the geneses of the ore-deposits of the Besshi type has been discussed by many geologists, from 1895 to 1910 syngenetic theories prevailed, and after 1910 up to date epigenetic theories have been advocated.
The prospecting policy for mine-working has applied with various methods under the influence of the genetic theories. Judging from the result of these prospectings, it seems effective to trace the horizon in which the ore-deposits occur from the standpoint, of a. syngenetic. theory which is related to the geologic structure.
By the fact that the Besshi deposits on the north limb of the Nakahichiban anticline and the Sazare deposits on south limb of the Yakushi anticline are situated opposits to each other in the center of the Tomisato syncline, the. prospecting policy has come to bear importance in discovery of blind bedded. ore deposits belonging to the Minawa formation; having the accumulation of the intense submarine volcanic activities below the Tomisato Syncline.

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