Zircon U-Pb age of the ore-bearing granite and molybdenite Re-Os isotopic age of the Donggebi Mo deposit, Xinjiang and their geological significance

The Donggebi Mo deposit, located in Eastern Tianshan, Xinjiang, is a supper-large porphyry type deposit with a reserve of over 0.5 million tons of molybdenum. The porphyritic granite and the granitic porphyry underlying the ore bodies are believed to have played important roles in the Mo mineralization. The Re-Os isotope results for the molybdenites from the ores yield an isochron age of 233.2±2.2 Ma and the weighted average age of 235.4±2.5 Ma. Zircon U-Pb ages of the porphyritic granite and the porphyry are 237.0±4.7 Ma and 237.0±4.7 Ma, respectively. These dating results indicate that the Donggebi porphyry Mo deposit and the related granites were formed in the late Triassic epoch. The granitic intrusion probably provided the ore-forming metals which led to the formation of the Donggebi deposit. The occurrence of the Donggebi porphyry Mo deposit demonstrates that the Indosinian orogeny is an important metallogenic period in East Tianshan. Based on the regional magmatism, we suggest that the Donggebi Mo deposit was related to a regional extension and the granitic magmas were produced by intrusion of mantle material into the continental crust.