御來山地域의 褐簾石鑛床

Allanite Mineralization in the Mt. Eorae Area

A study of rare-earth mineralization in Kyemyungsan metasedimentary formation of Precambrian Ogcheon Group was carried out in the Mt. Eore Area near Choongju City based on the thorium (Th) and uranium (U) count data of geophysical airborne survey. This rare-earth mineralization was found in the magnetite-bearing banded quartizite which contains diagnostically some amounts of the metamict allanite. The brown colored allanites are distributed as aggregates of fine grains and sometimes banded structures with magnetite (inter growth) along the banding. The ore bed is displaced by the small faults and granite intrusions, and separated 5 ore blocks. The dimensions of the outcrop are 50-80 m in width, 1,500 m in length with the strike of N70-80°E and dip of 50-80°NW. In the field, the values of total gamma ray count of GR-101A scintillometer were able to measure more than 400 cps and maximum 1,500 cps, which data are coincided with the values of GR-310 gamma ray spectrometer and the gamma ray count of well logging data. The chemical compositions of the allanites from EPMA data are ranged fromΣTR₂O₃ 18.57% to 26.00%, and the cerium oxides (Ce₂O₃) of allanite are positive relation with La₂O₃, MgO, FeO, MnO and negative relation with SiO₂, Al₂O₃, Nd₂O₃. The result of Neutron Activation Analysis (N.A.A.), Multi-Channel Analysis (M.C.A.) and wet chemistry of 25 outcrop samples for the elements of REE, Zr, U, Th shows strong anomalies. The good correlation elements with the thorium (Th) are the elements of La, Ce, LREE, TR₂O₃, Pr, Sm, Yb, Lu by the increasing order.