On the Ore Deposit and Prospecting in the Taisyu Mine Nagasaki Prefecture
1959 Volume 9 Issue 37 Pages 265-275
Details
1959 Volume 9 Issue 37 Pages 265-275
The Taisyu Mine, famous in Japan for the excellent high grade Pb-Zn ore it produces, is in the western part of Tsusima island.
The sedimentary rocks of Tsusima are said to belong to the Taisyu formation of Palaeogene age and consist of sandstone, shale, and an alternation of the two.
The Utiyama granite batholith, with its long axis trending N30°-40°E, intruded the sedimentary rocks and converted them to hornfels.
There is a synclinal axis in the southeastern part of the mine, and the Komoda fault group is in the northwestern part. Both parallel the long axis of the granite. The principal ore deposit of the mine is a mesothermal fissure-filling galena-zincblende-pyrrhotite vein, found in the N-S fault, which is developed in the zone between the synclinal axis and the Komoda fault group.
The more than thirteen known veins form three main vein groups-east, central, and west-that are arranged en echelon with a 700 to 800m interval.
Vein inclination of this mine has been recognized as being related to the granite. The prominent geologic features that dominantly controlled placement of the ore deposits are the synclinal axis, hornfels, quartzporphyry, the N-S fault, and the reverse fault in sandstone.
The mode of occurrence of the ore-body has the following characteristics:
(1) The zonal arrangement of minerals is remarkable in each vein.
(2) In the N-S fault, the main path of ore-solutions has followed the axes of bends in the strike of the fault plane, and ore bodies have formed in favorable places near these axes.
(3) Likely places for the formation of ore bodies are the intersecting lines between the N-S fault and a N 40°-50°W fault, the sandstone, the quartz-porphyry dikes, and bedding faults, and also the junctions between small faults.
A "standard program of prospecting" was made in this mine from the recognized relations of geologic structure and ore deposition mentioned above. The prospecting practices following this program have been effective and, as a result, many new ore bodies have been discovered.
