大興白雲石鑛山의 地質鑛床 槪査報告

A preliminary report on the geology and ore deposit of Daeheung dolomite mine

The Daeheung Dolomite Mine, which is about 6km south of Danyang, Chungcheongbugdo, is coincided with almost central portion of the Danyang quardrangle scaled in 1:50,000. The purpose of this report is to prepare a information for the economic evaluation on the mine. Geology of the region is composed of worm-eaten limestone, crystalline limestone, crystalline dolomite rock, sandstone and shale from bottom, those are applicable to so-called Dumugol and Maggol formation of Ordovician, and batholithic biotite granite is intruded the west-side of the ditto sedimentary rocks. The dolomite bed, emplaced in bottom of the upper limestone formation, so-called Maggol formation, is about 270m in thickness, and dips 30°~50° northwest. The facies of the dolomite rock contained many brucite crystals is not only coarse-grained crystalline, but also micro-crystalline in contact metasomatic parts. 25 samples were taken from the two series, A and B, in the nearly crossed direction to the strike of the dolomite bed as shown in the geological map. They were chemically analysed on the components of MgO, CaO, and SiO₂ as shown in Table 2. The estimate ore reserves total some 107,200,000 metric tons above the 320m level with the following average contents: MgO 21.80%, CaO 29.27% and SiO₂ 0.64%. It is caused by brucite minerals that MaO content in the dolomite rock is higher than pure dolomite (21.7%). The dolomite ore is possible in use for magnesian fertilizer, magnesian cement and refractory material, especially the microcrystalline dolomite ore is useful for a refractory material in furnaces of iron industries.