Ore-Forming Environment And Genesis Of Leqingla Lead-Zinc Deposit, Tibet

The east segment of Longgeer-Nianqingtanggula magmatic arc is delimited by Dangxiong-Yangbajing fault in the west, Yongzhu-Jiali-Bomi suture zone in the north and east, and Shamole-Luobadui-Milashan fault in the south. The magmatic activity in this region was very fierce and frequent. Either volcanic or granitoid rocks are widely present. In addition, since Late Paleozoic, this area has been characterized by extensively distributed carbonate-clastic rock associations sedimentated from shallow sea, epineritic environment , marine-continent exchange environment. All of these exceptionally geologic conditions contributed significantly to the formation of Skarn deposits.Leqingla lead-zinc deposit is located in the south margin of east Longgeer-Nianqingtanggula magmatic arc, falling into the Nianqingla-Shangchayu Pb-Zn(Cu)-Fe mineralized sub-zone. During the research, the geological features of Leqingla lead-zinc deposit is studied in detail. On the basis of analysis of ore-controlling factors such as strata, structure, and intrusion body, the ore-forming environment is discussed. The formation time and ore sources of the deposit are determined by using geochemical data. The genesis of the deposit is analyzed as well as its metallogenic model is constructed, combined with the regional research achievements, and directed by theories of Plate Tectonics, Metallogeny of collisional Orogeny and Skarn Deposit. Based on some other Skarn Deposits and concluding their ore-forming regulations in this region, the prospecting direction of Skarn Deposits is pointed out.The results show that the Leqingla deposit was generated by the collision of Indian Plate and Eurasian plate, formed during the transition from syn-collision(65~46Ma) to late collision(45~21Ma), which was a period of compression-extension conversion of collisional orogeny. Due to the violent compression, the materials in the deep crust melted partially, followed by magma ascent and emplacement, which extracted mineralizing materials from surrounding strata. Then, the magmatic fluids were separated from the magma and mixed with meteoric water. These mixed fluids reacted with the carbonate strata and the ores were formed. The deposit is classified into Skarn type.Overall, the prospecting direction of Skarn Deposits in the region should be focused on both sides of large faults, mainly the superposition area of near EW sub-faults and intermediate-acidic intrusions and carbonate-clastic rock associations. In addition, Skarn deposits are always in coexistence with Porphyry Deposits. Moreover, these two type deposits share close genetic relationship. Therefore, porphyry deposits can act as a mark to help the exploration of skarn deposits.