Regarding the Shibetsu Limestone Mine and its Developement

Abstract

Many limestone layers are intercalated in the Pre-Cretaceous system (so-called the Kamui holizon of the Hidaka Group) which developes at the border area of Shibetsu city and Asahi town in Kamikawa province. Especially the limestone mass which is found in the south-eastern range of Kamishibetsu 27 area is comaratively large and its quantity is also good.This limestone has been developed by the Shibetsu Sekkai Kogyo K.K. since 1960, and its production of both slaked lime and quick lime shows 60% of whole Hokkaido in recent.During this time, the company has been attempting the rationalization of management, promotion of outdoor minig of ore, improvement of equipment and calcination method. However recent economical depression of limestone industry forced every limestone mine to cost down its mining charge. So, it is urgently necessary to reinvestingate the ore body and re-examine its un-mined reserve.This area is a mountainous high-land, showing 400-600m from sea-level, and is occupied mostly by PreCretaceous Hidaka Group. This group is striking alomost NS and dipping toward E. Owing to the existence of many severe foldings, faults and crushing zones, the detailed Seological succession is not clear. However generally speaking it will be said that the lower part is mainly consist of black slate, sandststone, the upper is of schalstein, limestone, siliceous rock and shale.In some parts hornfels and gneiss are formed, and dioritic rocks are also observed.Workable limestone is intercalated in the schalstein of the Kamui-holizon as irregular masses, and are developed along NE-SE mountain range containing 644.7m peak. These limestones are grayish white-dark gray in color, compact, generally microcrystalline, and sometimes phanerocystalline in nature. The marginal parts of limestone are changed to hard siliceous limestone and calcareous schalstein frequently. The destribution of ore is traced about 2km, and separated into 3 parts, No. 1 ore, No. 2 ore and No. 3 ore.No. 1 ore is situated at the northern end of the ores and is now under working.Average value of limestone is as follow;CaO 54.95% SiO2 0.06% Fe2O3+Al2O3 0.19%MgO 0.07% Ig. Loss 43.46%Fig. 2 shows holizontal figure of each 20m distance from 315m to 455m from sea level. In this body, the excllent part is a northern half (part A) which is now working, and a part of northern side (part B). The extention of A is 250m and 70m wide, and the lower part is like a bilge shape, extending irregulary. The extention of B is 180m and 30m wide forming a lenticular shape. The ore reserve of A part is estimated as 2, 840, 000t and B part is 920, 000t (each 5m contour, specific gravity of ore-2.6 and safty security 90%). However the workable reserve will be as follows;A 1, 420, 000t B 460, 000tFurther more 700, 000t of ore has already been mined out of A part. So the workable reserve of A is 720, 000t. The Shibetsu Sekkai Kogyo K.K. started to business by the schedule of 72, 000t yeary production (40, 000t for construction, 32, 000t for slaked and quick lime). Actual production in 1960 was 87, 000t (30, 000t for construction, 57, 000t for slaked and quick lime).The first pit was settled at the center of No. 1 ore body, 315m high from sea level. At first main level transportation way was made aiming against the No. 1 ore bodycenter, then the main druft and the subdruft were made by 55° upward at the point of 120m pit mouth. These drufts are settled in order to connect the working face of the north side of the eastern part of No. 1 ore. Another main drufts, No. 2, No. 3 and No. 4 are completed lately after, and the glory hole mining method was started. As mining method, underground mining and sub level method were adopted mainly, and sometimes bench-cut method was also used.