Fluid Inclusion And Isotope Studies Of The Weilasituo Tin Polymetallic Deposit In Inner Mongolia

The Weilasituo tin polymetallic deposit is situated in Keshiketeng,northwest of Chifeng city,Inner Mongolia,and is located in the western slope of the southern Great Xing'an Range metallogenic belt.Based on the geological background of existing data and previous studies,this work summarizes the ore-forming fluid and metal source.The genesis of the deposit was summarized by comprehensive geological features and geochemical characteristics.Based on the crosscutting relationships of ore bodies,ore mineral and alteration assemblages,the ore-forming process can be divided into the following four stages:amazonitization stage,greisenization stage,quartz+cassiterite+sphalerite stage and sulfide stage.The major wall rock alteration types include greisenization and silicification.Fluid inclusions are dominated by vapor-liquid type.Homogenization temperature show a range from 209.2 to 383.3?,mainly between 220 and 280?.The final ice melting temperatures range from-7.9 to-1.2?.The salinity ranges from2.95 to 10.43‰,and the density ranges from 0.65 to 0.95 g/cm³.In summary,the ore-forming fluid is middle-low temperature,low salinity and low density.The results of laser Raman analysis showed that H₂O was the main component of the liquid phase,and the vapor phase contains CH₄,CO₂ and H₂O.The results of hydrogen and oxygen isotope analysis show that the ore-forming fluid is mainly derived from a magmatic water,and a small amount of meteoric water is involved in the late stage.The results of sulfur isotope analysis show that that the?³⁴S ranges from-4.16 to 6.09‰.The distribution of the samples is concentrated and has obvious a tower distribution.It is suggested that sulfur of the deposit shows a magmatic origin.The Pb isotope compositions indicate that the Pb is originated from magma with a mixed mantle and lower crust source.The comprehensive analysis shows that the Weilasituo tin polymetallic deposit is a greisen Sn deposit.