Hydrogen and Oxygen Isotope Compositions of Ore Fluid in the Dongyang Talc Deposit, Korea

摘要

Mineralized zone in the Dongyang talc deposit occurs on the lowest dolomite layer of the Hyangsauri Dolomite belonging to the Okcheon Super Group. Ore bodies are emplaced as pipe-like body along the axis of minor fotds plunge 40° to the N76° ~ S3°W developed in these dolomite layers. Amphibolites arts I*-luid niong the upper or lower contact of ali ore bodies and amphibolite itself is mineralized to talc at the contnct. This amphibolite was suggested to be related to the mineralization of talc in the area[ll]. Oxygen and hydrogen isotopic dala of talc shows that 5I8O and 5D range from 7.4 to 15.4 %o (vs. SMOW) and from -65 to -90 % respectively. Water content of talc extracted in the hydrogen is near 4.0 wt.% and agrees with that calculated from chemical formula. BD values of tremolite te talc schist are in the similar range to those of talc. 5D values of amphibolite ranges2 to -104 per mil, which are lower than those of talc. SISO and 5D values of the metainorphio nenr the area have quite different range of values compared with those of talc. Based on the fluid inclusion and mineral assemblage data, the pressure and temperature of talc formation are estimated as I,64O~2,530bnr, and 440~480"C, respectively for talc I (early stage). The P-T condition of talc II (late stage ) formation was l,400~2,200lwr, and 360--390T, respectively. The isotopio coin Posil ion of the fluid related to the talc formation fall in or veiy close to those of magmatic water in S C> and 8D. These data imply that the ore fluid was from the hydrothennnl solution of igneous origin ailtt lws tiiic I'onned in much higher temperature compared to the clay minerals of the surface environment.