Zircon U-Pb dating and Hf isotopic compositions of intrusions in the Erdaohe silver-lead-zinc deposit, Inner Mongolia and the metallogenic process of the deposit

The Erdaohe silver-lead -zinc deposit is a newly discovered large skarn deposit in central Great Xing' an Range, and its formation is closely related to multi -stage intrusions. The ore bodies in the deposit mainly occur in skarns, marble, and fine-grained granodiorites. In this study, we conducted LA-ICP-MS zircon U-Pb dating, Hf isotopic analysis, and the electron microprobe analysis ( EPMA) of garnets for the major intrusions and garnet granites in the deposit. Zircon grains from the epidotized fine-grained granodiorites, epidotized fine-grained diorites, and granite porphyry yielded weighted mean Pb-206/U-238 ages of 506 +/- 4. 3Ma, 213 +/- 2. 8Ma, and 128 +/- 1. 1Ma, respectively. The garnet skarns and epidote skarns in the Erdaohe deposit are frequently interspersed with each other, and the ore minerals such as sphalerite and galena in the deposit are characterized by recrystallization. Moreover, the EPMA results of garnets in the skarns show there were at least two stages of fluid activities with different natures. All these indicate that the Erdaohe deposit has undergone at least two stages of mineralization events. Zircons from three types of intrusions obtained yielded epsilon(Hf) (t) values of 0. 9 similar to 6. 9, 8. 3 similar to 15. 1, and 7. 9 similar to 14. 1, respectively, with t(DM2) values of 1. 6 similar to 1. 1Ga, 0. 8 similar to 0. 3Ga, and 0. 8 similar to 0. 3Ga, respectively. This indicates that all these granitoids are originated from the partial melting of the juvenile crust, and their formation may be related to the combination of the Erguna and Xing' an blocks, the closure of the Mongol -Okhotsk Ocean, and the subduction of the Paleo-Pacific Plate, respectively. The superimposition and evolution of tectonic systems play a crucial role in the formation and enrichment of the Erdaohe silver-lead-zinc deposit.