Study On Geological And Geochemical Characteristics And Genesis Of Boniangou Copper-gold Deposit,Muli,Sichuan Province

The Boniangou copper-gold deposit is located in the southern part of the Garze-Litang suture zone and is located on the northern edge of the Geza arc porphyry polymetallic metallogenic belt.The deposit is still in the exploration stage with a low degree of research.Based on the field investigation,this paper systematically studies the basic geological characteristics of the deposit,diagenesis and mineralization age,metallogenic physicochemical conditions,ore-forming fluid characteristics and metallogenic dynamics background,and compares it with similar mineral deposits in the region.Determine the genetic type of the deposit,and provide a theoretical basis for revealing the prospecting potential of the copper-gold deposit in the Garze-Litang suture zone and further prospecting direction.1.The main strata exposed in the mining area are Triassic and Permian strata,the most important of which are the Upper Triassic Qugasi Formation?T₃q?and the Middle Triassic Nasongyun Formation?T₂n?.The structural attributes and types of the mining area basically inherit the structural characteristics of the Garze-Litang suture zone.There are mainly a group of NNW,a group of NE and a group of near EW three faults.Copper-molybdenum mineralization belongs to porphyry copper-molybdenum.The ore-controlling factors are mainly a set of compound porphyry rocks.These intrusive bodies are located in a set of sedimentary facies limestone and feldspar quartz sandstone of Qugasi Formation?T₃q?and Nasongyun Formation?T₂n?.2.The SiO₂ content of the quartz monzonite porphyry in the Boniangou deposit is65.67%-68.49%;the total alkali content is 7.11%-7.89%;the Litman index is 2.21².62;the aluminum saturation index A/CNK The value is 0.88⁰.94,the tie value is 0.91?<1.1?;the consolidation index?SI?is 13.16¹5.29,the differentiation index?DI?is 73.71⁸0.88;the LREE/HREE ratio is 9.53¹3.56,?La/Yb?_N The ratio is 11.44¹7.89,which indicates the characteristics of light rare earth enrichment.The value of?Eu is 0.71⁰.84,which is weak negative anomaly.The rock belongs to the high-calcium-calcium-alkaline series I type granite,and its source rock has shell-shell mixing.The characteristics of the source and the magma differentiation are more thorough.3.The ore-forming fluid of the Boniangou deposit belongs to medium-temperature,medium-slall,low-salt CO₂-rich fluids with a salinity range of 2 to 18 wt%NaCleqv.The density of the fluid can be calculated from the temperature and salinity data of 0.70 to 0.94g/cm³.The average value is 0.80 g/cm³,the pressure of the fluid is 421.9¹088.49×10⁵ Pa,and the average is 781×10⁵ Pa.The ore-forming depth of the deposit is 5.15-8.64 km,and the average depth is 7.17 km.The source of fluid is mainly magmatic water.The degree of precipitation participation during migration is not obvious.The precipitation of minerals is mainly caused by the boiling of fluid when the temperature and pressure conditions of the system change.4.The diagenetic age of the zircon U-Pb age represented by the Boniangou deposit is216±1.6 Ma,and the ore age of the molybdenite Re-Os isotope age is 212±1.8 Ma.Combined with the tectonic setting background,it is believed that the Boniangou deposit is formed on the transition node of the Yidun Island Arc Orogenic Belt from the subduction orogeny to the collisional orogeny,indicating the diversity of mineralization phenomena.Re content of molybdenite is 248.5×10^-6357.9×10^-6,indicating that the ore-forming material is mainly mixed with mantle material and part of the earth's crust.