Re-Os age of molybdenite from the Baoshan copper polymetallic deposit in the Jiurui ore concentration area along the middle-lower Yangtze River region and its geological significance

Porphyry-skarn deposits in Jiurui area constitute an important part of the middle-lower Yangtze River Cu-Au-Mo(Fe)polymetallic ore belt. Since the implementation of the prospecting breakthrough strategy, the Baoshan deposit has been the first medium-size porphyry-skarn copper polymetallic deposit discovered at the core of Jieshou-Daqiao anticline in Jiurui area. In this paper, molybdenite Re-Os dating was used to study the mineralization time of the Baoshan deposit and, as a result, six molybdenite Re-Os model ages of 147.2±3.6 Ma to 150.5±2.7 Ma and weighted average age of 148±1 Ma(MSWD=1.03) were obtained. These six molybdenite Re-Os model ages yielded an isochron age of 148.6±2.6 Ma(MSWD=1.9), which represents the ore-forming age of the Banshan deposit. The ore-forming age of the Baoshan deposit is similar to ages of other porphyry-skarn type copper polymetallic deposits in Jiurui area(e.g., Wushan, Chengmenshan, Fengshandong of Hubei, Jilongshan, Songjiachong, Dengjiashan and Tongjiangling), as well as in Tongling and southeastern Hubei areas within the middle-lower Yangtze River region. All of them are products of granitic magma activities related to the crust-mantle syntexis resulting from the upwelling asthenosphere and the underplating basaltic magma in the Yanshanian period.