On the Successful Exploration at the Lower Part of the Mozumi Mining Area, Kamioka Mine

Abstract

It has been proved that shapes of the mineralized zones depend on the location of intrusive granite porphyry, which appears to be the ore bringer, large fractures and fissures, and plunges of limestone bodies. In the mineralized zones, the zonal distribution of ores were clearly recognized. Namely, surrounding the molybdenite-bearing granite porphyry the zones of predominant ore metals are in the following order : Mo-Cu-Cu : Zn-Zn-Zn⋅Pb-Pb. Metal ratio, ρ_Pb=Pb%/Pb%+Zn%×100, is very useful index for the quantitative indication of the zonal distribution. It was shown that ρ_Pb values for the different zones become higher outwards as the distance from the granite porphyry increases. The geological structure shows a reverse S-letter pattern which was caused by the movement of Nanagohi drag fault, with folded limestone bodies plunging 45 to 50 degree to southwest.
Consideration on the shape of the mineralized zone, zonal distribution, and structure of limestone suggested the location of the mineralization, sort of ores and grade of ores at the deeper part of the Mozumi mining area. It was also inferred that workable ore deposits should be expected even under barren limestone zone merging with slightly mineralized zone downward in the southern part of the Mozumi area.
As the result of explorations based on the above-mentioned ideas, new ore reserves, 1, 518, 000 tons of lead-Zinc ore and 171, 000 tons of copper ore, totalling 1, 689, 000 tons, have been discovered since 1962 to 1968. In future exploration, discovery of more ore bodies can be expected in the southern district, where active prospecting works have been in progress on the -320 meter level, becouse of several indications of hidden ores and many other mineralization.