The distribution of epithermal base metal deposits in the Lanping basin, Yunnan province, SW China is controlled by Cenozoic thrust-nappe systems. The Baiyangping and Wudichang Ag-bearing polymetallic deposits are representative of the epithermal base metal deposits in the Lanping basin. Hydrothermal calcites associated with base metal sulfides in these two deposits yield similar Sm-Nd isochron ages of 30.1 +/- 1.9 to 27.4 +/- 1.8 Ma, respectively. These results indicate that the ages of mineralization of the Baiyangping Cu-Ag-Co and Wudichang Pb-Zn-Ag ore deposits are contemporaneous with the Cenozoic Indo Asian continental collision. Such temporal correlation, combined with the apparent regional structural control of the distribution of these type of deposits suggests that Cenozoic thrust-nappe tectonics and associated hydrothermal activity played an important role in the formation of the epithermal Ag-bearing polymetallic base metal ore deposits in the Lanping basin.