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

Abstract: 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.