REE composition in scheelite and scheelite Sm-Nd dating for the Xuebaoding W-Sn-Be deposit in Sichuan

摘要

The scheelite with large size and euhedral shape from Xuebaoding, Sichuan Province is an ideal mineral to study REE patterns and Sm-Nd dating of non-gold deposits. The scheelite has diameters of 1 — 10 cm and colors of pale beige to deep orange. Most of these scheelites occur in association with beryl, cassiterite and muscovite. The rare earth elements indicate that scheelite samples from Xuebaoding W-Sn-Be deposits contain high concentrations of rare earth elements with total IREE+Y contents in the range of 369—1725 μg·g~(-1) and nearly all of these scheelite samples are enriched in LREE and depleted in HREE and have negative Eu anomalies. The REE patterns of the scheelites are similar to those of A-type granite with obvious tetrad effect, similar to that of type II scheelites. Based on reported fluid inclusion studies, the mineralizing-fluid of the Xuebaoding W-Sn-Be deposit indicates low Na activity. The REE patterns of the scheelite are probably controlled by partition coefficient in hydrothermal fluid. In the ~(147)Sm/~(144)Nd-~(143)Nd/~(144)Nd diagram, the scheelites show a linear array corresponding to an isochron age of 182.0±9.2 Ma (MSWD = 0.52). The Sm-Nd age represents the formation age of the scheelite and can indicate that the W, Sn and Be mineralization at Xuebaoding took place in the Early Yanshanian. The Sm-Nd dating result is important for the study of the multi-metal resources in western Sichuan Province.