The Ore Deposits of the Kishu Mine as Related to Structural Features

Abstract

The Kishu Mine, about 18km NNW from Shingu, is in the southern part of the Kii peninsula. The principal products of this mine are copper ores and pyrite. The rocks in the vicinity of the mine consist of sandstones and shales of Mesozoic formation and the Tertiary formation called. the "Miyai series", and acidic igneous rocks usually called "Kumano acidic rocks".
The ore deposits of this mine are of shallow vein type and are found along normal faults in the Itaya formation, the upper part of the Miyai series.
On the basis of the rock facies, the Itaya formation may be divided into the following members in descending order:
Member Thickness
G-sandstone …………………………………………………………………150m
F-shale ………………………………………………………………………50m
E-sandstone …………………………………………………………………70m
D-alternation of sandstone and shale ……………………………20-25m
C-sandstone …………………………………………………………………60m
B-shale ………………………………………………………………………50m
A-alternation of sandstone and shale ………………………………… ?
Ore shoots are usually formed in the E-sandstone member as shown in Fig. 5. The favorable openings of the E-sandstone member are due to its own physical properties and also to the relative difference. of the physical characters of each member at the warped fault plane. As a whole, the veins become wider just under the F-shale, which is considered to be the "cap rock" in the formation of the ore veins.
The detailed geologic relation between veins and the persemic garnet-bearing biotite-liparite dike, an off-shoot from the main mass of the Kumano acidic rocks, is also described in this paper.