Baoshan Cu-Mo-Pb-Zn-Ag polymetallic ore deposit is located at the west of Guiyang county, Hunan Province. This deposit is genetically related to the granodioritic porphyry and granitic porphyry. The mineralization at Baoshan shows an apparent spatial zonation, which centered within the Baoling reverse anticline. The orebodies at the center zone are located in the inside and outside contact zones of granodioritic (granitic) porphyry, which are dominantly skarn-type Cu-Mo mineralization. The orebodies at the periphery, such as the eastern Baoshan, the western Baoshan and the Caishenmiao deposit, were mainly Pb-Zn-Ag mineralization occurring in the Carboniferous carbonate rocks. Based on the precise SHRIMP U-Pb dating of zircons, we obtained an age of 158 +/- 2Ma (MSWD = 0.26, Probability = 0.61, n = 12) for the granodioritic porphyry related to the mineralization. Combining our data with those previous published SHRIMP data (Wu et al., 2005), we got a precise U-Pb concordant age of 161 +/- 1Ma (MSWD = 0.66, Probability = 0.42, n = 23), which can represent the intrusive age in the Baoshan ore-field. Based on the precise Re-Os dating of the molybdenite from skarn-type ore, the mineralization age is 160 +/- 2Ma. In this paper, we suggest that both granitic rocks and ore deposits at Baoshan have the same formational ages, which indicate that the granodioritic porphyry is genetically related to the Baoshan deposit. Compiling all available ages for granitiods and mineralization in the region, we suggest that 155 similar to 165Ma was the first peak stage for Mesozoic large-scale magmatism and mineralization in Hunan and in the middle segment of the Nanling Ranges. During this period, the Baoshan polymetalic deposits were formed. Our new data provide important isotope chronology evidence for further study of the regional mineralization rules.
