Molybdenite Re-Os Precise Dating for Molybdenite from Cu-Au-Mo Deposits in the Middle-Lower Reaches of Yangtze River Belt and Its Implications for Mineralization
MAO Jingwen1,2) ,Holly STEIN3) ,DU Andao4),ZHOU Taofa5) ,MEI Yanxiong1), LI Yongfeng1), ZANG Wenshuan2),LI Jinwen1,2) 1) Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, 100037 2) Faculty of Geosciences and Resources, China University of Geosciences, Beijing, 100083 3) AIRIE Program, Department of Earth Resources, Colorado State University, Fort Collins, USA 4) National Research Center of Geoanalysis, Chinese Academy of Geological Sciences, Beijing, 100037 5) Department of Resource and Environmental Sciences, Hefei University of Technology, Hefei, 230009
The Middle-Lower Yangtze River metallogenic belt is an important corridor for Cu-Au-Mo-Fe deposits in East China. Because there are porphyry-skarn Cu-Au-Mo deposits, and stratabound Cu-Au-Mo deposits, their origin have been strongly controversial for a long time. We obtained eleven molybdenite samples from five skarn-porphyry Cu-Au-Mo deposits and the other five samples from the Datuanshan stratabound Cu-Au-Mo deposit for Re-Os dating. The total 16 samples are dated with ICP-MS method and 9 of them are dated by NTIMS. The results from the two methods of ICP-MS and NTIMS are almost concordant each other. Re-Os model ages of 16 molybdenite range from 134. 7±2. 3 to 143. 7±1. 6Ma (2σ) in which the model ages of the five samples from the Datuanshan deposit are quite close, varying from ?38. 0±3. 2 to 140. 8±2. 0 Ma, averaging 139. 3±2. 6 Ma, their corresponding isochron is 139. l±2. 7 Ma with initial Os value of 0. 7±8.1 (MSDW =0. 29). These data definitely reflect the porphyry-skarn-Cu-Au-Fe-Mo deposits and the stratabound skarn Cu-Au-Mo deposits share the same forming ages and are the products of a same metallogenic system. They all occurred at the time of the transition stage of geodynamic regimes i. e. from the main compression regime in north-south direction to quickly significant extension in EW-direction.