Genesis of the Meng'entaolegai Ag-Pb-Zn polymetallic deposit, inner Mongolia, Northeastern China

The large-scale Meng'entaolegai Ag-Pb-Zn polymetallic deposit is located in the Great Hinggan Range metal-logenic belt, northeastern China. To better understand the formation of the Meng'entaolegai deposit, we present in situ S isotope data, zircon U-Pb isotope data, sulfide Rb-Sr data, and molybdenite Re-Os data for the units associated with the deposit and surrounding regions. In situ analyses show that the & delta;34S values of the sulfides (galena, sphalerite, and pyrite) vary from + 2.4%o to + 6.6%o (mean = +4.7%o, n = 60). The data herein confirm that the sulfur was mainly derived from a magmatic source. Zircon U-Pb dating of the medium-to coarse-grained monzogranite, plagiogranite, and fine-grained monzogranite from the Duerji batholiths and granodiorite and monzogranite from the Meng'entaolegai deposit yield weighted mean ages of 244.3 & PLUSMN; 1.7, 243.0 & PLUSMN; 2.1, 151.8 & PLUSMN; 1.5, 232.6 & PLUSMN; 2.2, and 223.1 & PLUSMN; 2.3 Ma, respectively. The Meng'entaolegai deposit yields a molybdenite Re-Os age of 229.5 & PLUSMN; 1.5 Ma, but sulfide Rb-Sr dating yields an isochron age of 147.2 & PLUSMN; 2.3 Ma. These new age data have revealed that the Meng'entaolegai polymetallic deposit formed during two mineralization episodes: an early episode at 230 Ma and a second episode at 147 Ma. The Late Triassic hydrothermal activity and weakly Mo mineralization formed in an extensional setting after the final closure of the Palaeo-Asian Ocean. The Late Jurassic hydrothermal activity and Ag-Pb-Zn mineralization formed in an extensional environment related to the Mongol-Okhotsk Ocean, but these exposed granitic rocks are unlikely to be related to the Ag-Pb-Zn mineralization, suggesting that more research is needed on the magmatic hydrothermal activity within the study area.