The Study On The Metallogenesis And Prospecting Of The Baiyinnuoer Pb-zn Deposit, Chifeng City, Inner Mongolia

The Baiyinnuoer Pb-Zn deposit in Chifeng, Inner Mongolia is the largest skarn-type Pb-Zn deposit in Northern China. In order to constrain the ore-forming age, the zircons from granodiorite,dacite-detritus crystal tuff, feldspar porphyry, trachyte- crystal tuff which are closely related to mineralization were dated by using the LA-MC-ICP-MS method, and yield（242.1±1.2） Ma^244.4±1.1 Ma,（249.6±1.1） Ma,（136.0±1.7） Ma^137.6±1.8 Ma,（136.1±1.1） Ma^139.6±1.2 Ma, respectively. In combination with previous dating result of（129±1.4 Ma） of feldspar quartz porphyry which cuts the ore bodies in the ore district, it indicates that there is a superimposed mineralization in the Baiyinnuoer Pb-Zn deposit, with the Pb-Zn mineralization related to granodiorite taking place during the Early Indosinian epoch（±243 Ma）, and the superimposed Pb-Zn mineralization related to hydrothermal fluid afrer the volcano eruption taking place during the middle Yanshannian epoch.The detailed unvestigation shows that the mineralization and alteration zoning formed during the Early Indosinian epoch has the typical contact metasomatic skarn zoning characteristics, while the mineralization and alteration zoning formed during the middle Yanshannian epoch with hydrothermal fluid filling metasomatic characteristics. In combination with the deposit geology, it is suggested that the typical contact metasomatic skarn-type Pb-Zn mineralization related to granodiorite took place during the Early Indosinian epoch, whereas the hydrothermal Pb-Zn mineralization related to the Baiyinwula volcano in the southewest of the ore district occurred during the middle Yanshannian epoch.By testing and analyzing the S and Pb isotopics of ores in the Baiyinnuoer Pb-Zn deposit, it indicates that ore-forming materials were mainly derived from the Early Indosinian granodiorite with partly from Cretaceous volcano-sedimentary rocks and Permian marble.Geochemical survey on the No.3 orebody of 750-level in the Baiyinnuoer Pb-Zn deposit shows that the high temperature metallogenic elements anomalies mainly appear in the southwest of the sampling area, the middle temperature metallogenic elements anomalies are widely distributed, and the middle-low temperature metallogenic elements anomalies appear in the middle part and northeast of the sampling area. It suggests that the ore-forming fluid migrated from southwest to northeast in the ore district. Combined with the previous analysis of the ore-forming elements zoning and geophycical characteristics, it is proposed that there is ore-prospecting potential in the deep of the southwest of the Baiyinnuoer Pb-Zn deposit.