Structural control, and Correlation of Uranium Distribution and Mineralogy of Meta-pelites in Ogcheon Terrain, Korea

한반도(韓半島) 옥천대(沃川帶)에 분포(分布)하는 함(含)우라늄층(層)의 지질구조규제(地質構造規制) 및 조성광물(組成鑛物)과 우라늄분포(分布)와의 상관관계연구(相關關係硏究)

The rock units of Goesan area in the Ogcheon metamor phic terrain established on the basis of field criteria should be redefined into following sequence. Based on shear senses in secondary small structures which are usually observable in the investigated area, the stratigraphy can be lithologically divided into the lower pelite, pebbly mudstone, upper pelite, quartzite and psammite unit in ascending order. This conclusion is in discordance with a previous opinion; Munjuri formation and Guryongsan formation may be equivalent to upper pelite unit, Iwonri formation and Hwanggangri formation to pebbly mudstone. From this, it may be inferred that isoclinal overturned folds repeatly occur in the area. The uranium bearing coaly thin layers in upper pelite unit have relatively broad exposures in Deogpyeongri block of Goesan area along culmination zone in the central part of the investigated area. It is believed that structural feature in the block recognized complexly refolded synform plunging to southwest. Mineralogical and radiometric studies were made on 135 representative samples from the Ogcheon Group of Korea. The mineralogy of all black slate samples is qualitatively similar but quantitatively ·different. The uranium distribution in the studied area show approximately log normal. Uranium in the black slates of the Ogcheon Group was deposited together under same physico-chemical environmental conditions. The chemical and geological factors that controlled the abundance of organic carbon and iron oxides also controlled the uranium content. The relationship of the major components to uranium can be expressed by the following regression equation: $Log(U\times10^4+1)$= 1.70999-0.00367(quartz)0.00512(micas)-0.00930 (other silicates)+0.01911 (iron oxides)-0.03389(other opaques)+0.02062(organic carbon).