別子付近の三波川変成帯とこれに伴う含銅硫化鉄鉱鉱床(I)その研究の史的変遷と現況について

抄録

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.