Characteristics and genesis analysis of ore-forming fluids in Yikeguole copper-molybdenum polymetallic deposit in the eastern part of East Kunlun Mountains

The Yikeguole deposit is located in the eastern part of the East Kunlun orogenic belt. It is a porphyry copper-molybdenum polymetallic deposit discovered in recent years. In order to find out the nature of ore-forming fluids and the source of ore-forming materials, and to explore the genesis of the deposit, detailed petrographic observation of fluid inclusions, micro-thermometry, laser Raman and H-O-S isotope studies were carried out in this paper. According to the results of petrography and micro-thermometry of inclusions, fluid inclusions in main metallogenic stage (quartz-sulfide stage) include three types: liquid phase, gas-liquid two-phase and CO2-containing three-phase inclusions. The ore-forming fluids are characterized by medium-high temperature (165 ℃~330 ℃), medium salinity (2.24%~10.70%) and medium density (0.706~0.935 g/cm3). The ore-forming depth is 1.30~3.05 km and formed in a medium-shallow environment. The H-O isotope reveals that the ore-forming fluid is a mixed source of magmatic water and atmospheric precipitation, but the main body is magmatic water. The S isotope shows that the ore-forming materials are mainly derived from the deep magma. Combined with the regional tectonic evolution, it is considered that the Yikeguole deposit was formed because of the strong crust-mantle mixing in the Early Triassic of the East Kunlun area, forming a mixed magma rich in ore-forming elements. The ore-bearing fluid was decompressed during the rise of the mixed magma and mixed with atmospheric precipitation to cool down, resulting in a sharp change in the physical and chemical conditions of mineralization, which in turn promoted the precipitation of ore-forming materials.