Re-Os Molybdenite Ages of the Shenduolong Skarn Mo-Pb-Zn Deposit and Geodynamic Framework, Qinghai Province

The Shiduolong skarn Mo-Pb-Zn deposit is located in the multi-metal metallogenic belt of E'lashan. The precise age of the ore deposit limits our understanding of the ore-forming processes and geodynamical setting. In spite of the K-Ar methods of analysis and testing in the Shiduolong mining area and the periphery of intrusives (188-208 Ma and 368 Ma), whether or not thest ages can represent real mineralization times requires to be tested further. In this study, we carried out a Re-Os study of molybdenite from the Shuangqing deposit, providing fundamental data to build the mineral deposit model and reflect the geodynamical setting in this area. 6 molybdenite samples of the deposit yield Re-Os isotopic model ages ranging from 234.2 Ma to 240.1 Ma, with a weighted mean age of (236.1±2.1) Ma. A similar isochron age of (233.4±9.6) Ma is also obtained by the isochron regression. This result suggests that the Mo mineralization occurred in last Triassic. The Re contents of molybdenite indicate that ore-forming materials are derived from crust and aqueous fluids involved in the ore-forming stage. Based on the same of rock-forming in E'lashan and mineralization in Shiduolong Mo-Pb-Zn deposit, rock-forming and ore-forming were regarded as the same geodynamic background of India-Eurasia collision. The tectonic regime changing from developing oceanic rift to collision-extension make the thickened lower crust melt partially in the Indosinian magmatic-tectonic-metallogenic event.