Scheelite Sm-Nd dating and quartz Ar-Ar dating for Woxi Au-Sb-W deposit, western Hunan

Scheelite Sm-Nd and quartz Ar-Ar dating were accomplished for the Woxi Au-Sb-W deposit in western hunan. The results show that the Sm and Nd concentrations of scheelite are relatively high, and Sm/Nd ratios are usually high and variable. In the Sm-147/Nd-144 vs. Nd-143/Nd-144 diagram, the disseminated scheelites show a good linear array, which corresponds to an isochron age of 402 +/- 6 Ma and an initial Nd-143/Nd-144 ratio of 0.510544 +/- 9 (2sigma) with a epsilon(Nd)(t) value of -30.7. The Ar-Ar age spectra for 2 quartz samples display the saddle shape. The minimum apparent age, plateau age and isochron age of each quartz sample generally overlap within errors; and both the minimum apparent ages of 420 +/- 20 and 414 +/- 19 Ma coincide well with the scheelite Sm-Nd age. Both Sm-Nd and Ar-Ar dating results reveal that the Au-Sb-W mineralization at Woxi district took place in the Late Caledonian. This is in good agreement with the tectonic evolution of the Xuefengshan district and with some geochronological data available for Au, Sb and W deposits in this area. The low initial Nd isotope ratio of scheelites suggests that the fluid responsible for Au-Sb-W mineralization at the Woxi is of deep crustal origin and probably originated from the underlying Archaean continental basement rather than the host Proterozoic strata in western Hunan. The constraints on the mineralization time and on the fluid source provide insight into the genesis of the Woxi deposit.