Dating of the Giant Huize Zn-Pb Ore Field of Yunnan Province, Southwest China: Constraints from the Sm-Nd System in Hydrothermal Calcite

摘要

The Huize ore field, which is the most famous high-grade Mississippi Valley-type Zn-Pb ore field in China, consists of the Kuangshanchang and Qilinchang deposits. The Sm-Nd isotopic compositions of gangue calcite were analyzed to constrain the timing of mineralization. Eight calcite samples from the No. 6 orebody in the Qilinchang deposit have Sm and Nd concentrations of 1.82-25.93 and 15.25-79.02 ppm, respectively, and yielded an age of 225 +- 9.9 Ma with epsilon Nd = -10.6 and MSWD = 0.13. Five calcites from the No. 1 orebody in the Kuangshanchang deposit contain 2.37-2.90 ppm Sm and 8.18-16.85 ppm Nd, and yielded an age of 228 +- 16 Ma, with epsilon Nd = -10.6 and MSWD = 0.28. These two ages are close to the age of the Emeishan flood basalt, which is ca 255 Ma, and agree with the reported ~(40)Ar/~(39)Ar plateau and isochron ages of the native copper mineralization related to the Emeishan flood basalt in this region, which are 226-228 Ma. Moreover, previous study shows that the magnitude of uplift resulting from the Emeishan flood basalts is >1000 m. It indicates that the Kuangshanchang and the Qilinchang deposit formed during the same geological event and originated by fluid migration during uplift resulting from the Emeishan flood basalt.