Fluid Inclusion Study Of The Langshan Huogeqi Cu Polymetallic Deposit In Inner Mongolia

The Huogeqi copper-polymetallic deposit is located in the north slope of Langshan Mountain,the west end of Yinshan Mountains,Inner Mongolia.It is a typical Sedex deposit.Strata-bound characteristic of the deposit is remarkable as most of the ore are in the 2nd formation of the Mesoproterozoic Langshan Group.The major mineralization period of the deposit is sedimentary mineralization,and then it went through the transformation of regional metamorphism and magmatic hydrothermal.Based on the work of field recording,systematic sampling and rock-mineral identification,the author makes the research work including petrography,microscopic thermometry and laser raman spectrum composition analysis of the fluid inclusion from different periods of ore-forming.It is preliminarily discussed the characteristics of the fluid inclusion of Huogeqi deposit.The forms of fluid inclusion are mainly included two-phase aqueous type,pure gas type and pure liquid type.The sizes of fluid inclusion are between 5?m to 10?m,and the homogenization temperature is between 179.9?355.0?.The temperature of main ore-forming liquid is low,ranging from143.9?to 230.1?,while the temperature of regional metamorphism and magmatic hydrothermal transformation is high,ranging from 270.0?to 324.5?and 350.0?to 410.0?.The salinity is at the range of1.40?18.63wt%,then most is in 1.57?11.70wt%,and overall reflected low salinity fluids.The density of ore-forming liquid is low for the range of 0.364?0.956g/cm³,and mainly in 0.513?0.947 g/cm³.According to the estimation of ore-forming pressure through the depth of ore-forming,the pressure of ore-forming is 1.80?213.92MPa,and the depth of ore-forming is 0.18?3.94km.From sedimentation ore-forming stage to regional metamorphism transformation stage to magmatic hydrothermal transformation stage,the temperature of ore-forming liquid rises gradually,and the density gradually declines showing a significant negative linear relationship.The pressure rises showing a significant positive correlation linear relationship,which reflected characteristics of low temperature with low pressure,high temperature with high pressure,while there is no significant correlation between salinity and temperature.According to the test result of laser raman spectrum composition analysis,the metallogenic environment of the sedimentary mineralization stage is relatively reducing environment.Overall,the ore-forming fluid of Huogeqi deposit is mainly H₂O-Nacl-CH₄ system.As a whole,the characteristics of the fluid inclusion indicate that the main mineralization stage of ore-forming is low-temperature sedimentation.The regional metamorphism and magmatic hydrothermal transformation stage has the feature of middle-high temperature.Huogeqi deposit is a Sedex deposit with low salinity ore-forming liquid.It provides practical data for the study of the genesis of the ore deposit,and provides important guidance for the exploration work.