Scheelite geochemistry of the Sangdong W-Mo deposit and W prospects in the southern Taebaeksan metallogenic region, Korea

We compare the trace element geochemistry of scheelite from the economic Sangdong W-Mo deposit with scheelite from unmineralized or sub-economic prospects in Joongdong and Sangdong area in the southern Taebaeksan metallogenic region, to investigate the ore-forming processes controlling scheelite mineralization and to provide a geochemical model for W exploration. In the Sangdong W-Mo deposit, the Mo substitution into scheelite as a powellite (CaMoO 4 ) component changed colors of scheelite fluorescence under short-wavelength UV from yellow (Mo up to 51,000 µg/g) to blue (Mo up to 3.2 µg/g). Low-Mo scheelite with blue fluorescence occurred in the low-grade periphery of the Sangdong deposit and contained higher concentrations of Sr, possibly indicating a lower degree of fluid-rock interaction of the scheelite-forming fluid with Sr-bearing host. Mo-rich scheelite with yellow fluorescence accumulated in the W-rich center of the Sangdong deposit. Hence, the fluorescence color of scheelite reflected both the fluids oxidation state and the degree of fluid-rock interaction and might be useful for scheelite exploration in the Taebaeksan region. In the Sangdong deposit, Nb concentrations in scheelite were high and negatively correlated with its Eu anomaly values, suggesting extensive batholith-scale fractionation in a large magmatic reservoir. Conversely, much lower Nb concentrations of scheelite in the Joondong area suggests a relatively small or isolated magma reservoir that did not reach the same degree of fractionation at the point of fluid saturation, which would limit the potential for an economic scheelite mineralization. Scheelite Nb/ Ta ratio is found to effectively differentiate economic orebodies and subeconomic prospects in the Taebaeksan metallogenic region and might be a useful parameter for scheelite exploration.