Fluid Inclusion Characteristics And Genesis Of Zhuxi W(Cu) Deposit,Northeastern Jiangxi Province

The Zhuxi tungsten copper polymetallic ore area in northeastern Jiangxi is located between the Yangtze plate and the Huaxia plate,in the eastern part of the qinhang metallogenic belt,belonging to the pre Tarim Fuchun polymetallic metallogenic belt.The complicated genesis of the deposit has not been solved,which restricts the further exploration.The formation of superlarge deposits requires a large amount of fluids,while the study of fluid inclusions in the study area is still weak.In this paper,combined with detailed field exploration and systematic fluid inclusions study,the fluid properties of different mineralization stages will be analyzed,the fluid evolution characteristics will be revealed,and the metallogenic mechanism of superlarge deposits will be discussed.The core shows that there are three main types of mineralization in Zhuxi tungsten deposit:calcareous skarn type,magnesian skarn type and greisen type.There are seven stages in the formation of scheelite,The homogenization temperature is concentrated in(291-131)?,in which the homogenization temperature of calcareous skarn type tungsten ore is concentrated in three stages,which are(291-259)?,(231-197)?and(161-131)?;the homogenization temperature of magnesia skarn type tungsten ore is concentrated in two stages,which are(267-178)?and(177-148)?;the homogenization temperature of dolomite type tungsten ore is concentrated in two stages,which are respectively(291-221)?and(200-142)?.The fluid salinity related to scheelite is concentrated in(6.59-0.71)wt%NaCl equiv.on the whole,the salinity of the ore-forming fluid in these seven stages decreases with the decrease of temperature.The density of fluid related to scheelite is concentrated in(0.81-0.95)g/cm~3.As a whole,the density of fluid increases with the decrease of temperature.The density of fluid related to scheelite in the third stage of calcareous skarn type is the largest,and that related to scheelite in the first stage of calcareous skarn type is the smallest.As for the ore-forming pressure,the largest is 250.93bar of fluid pressure related to scheelite in the second stage of magnesia skarn type,and the lowest is 37.57bar of fluid pressure related to scheelite in the first stage of calcareous skarn type.The shallowest is 375.7m,and the deepest is 2509.3m.There are three types of scheelite between them.Fluid boiling and mixing promote the precipitation of scheelite,fluid boiling promotes the vertical zoning of scheelite,expands the range of fluid activity,and extends the time of contact and metasomatism with surrounding rock,which provides a strong barrier for the formation of world-class giant scheelite.