The Sources Of Ore-Forming Material And Evolution Of Ore-Forming Fluid In The Jinchanghe Fe-Cu-Pb-Zn Polymetallic Deposit,Baoshan,Western Yunnan Province

Jinchanghe Fe-Cu-Pb-Zn polymetallic deposit,which is located in the northern of Baoshan block,Yunnan Province,is one of the known large size skarn polymetallic deposits in the southern of Sanjiang Tethys domain,and has high economic value and important scientific research significance.Based on detailed field geological survey and petrographic observation,we studied the deposit from geological characteristics,petrogeochemistry,fluid inclusions geochemistry and stable isotopes in this paper.The origin and evolution process of ore-forming fluid and materials are identified,the migration mode and precipitation mechanism of metals are revealed,and the genetic type of the deposit is further discussed.The main results of this study are as follows:(1)Through field and petrographic observations,it is clarified that the mineralization alteration characteristics of the deposit are Fe-bearing ilvaite actinolite skarn,Cu-bearing garnet actinolite skarn,Pb-Zn actinolite skarn from east to west in horizontal direction and from deep to shallow in vertical direction.Accordingly,ore-forming fluids migrate from bottom to top and from east to west in long distance.(2)In terms of petrogeochemistry,according to the variation trends with elevation of major elements and trace and rare earth elements,it is determined that ore-forming materials originate from deep magma with Eu depleted,and the magmatic body related to mineralization is located in the depth of the deposit.(3)The microthermometry results of fluid inclusions in quartz at different stages show that the homogenization temperature decreases gradually from the retrograde alteration stage to the carbonate stage,and the salinity increases and then decreases.The homogenization temperatures of the quartz-sulfide stage are between 151 and266?,the salinities of WL-type inclusions range from 1.9 to 18.9 wt.%Na Cl_eq,and the salinities of S-type inclusions are between 31.9 and 33.5 wt.%Na C l_eq.Laser Raman spectroscopic analysis of single inclusions shows that the ore-forming fluid is mainly composed of H₂O with a small amount of N₂,and bornite has been newly discovered in the daughter minerals.The ore-forming fluid belongs to a H₂O-Na Cl system.(4)The S and Pb isotopic characteristics of sulfide show that the sulfur source is a mixture of the magmatic sulfur derived from deep mantle and the sulfur from strata,with the fractionation of sulfur isotopes reaching the equilibrium in each metallogenic stage.Sulfides are rich in uranium lead and slightly deficient in thorium lead,showing the characteristics of orogenic belt lead,and lead is derived from the mixture of upper crust lead and a small amount of deep crust and mantle magmatic lead.(5)Based on the abo ve results,the source of the ore-forming fluid and its evolution process are reconstructed,and it is deduced that metal elements carried by the ore-forming fluid mainly migrate in the form of stable complexes,and the ore-forming materials undergo the change of oxidation-reduction environment caused by fluid boiling and water-rock reaction and precipitate.It is inferred that the intermediate-acid rock mass related to mineralization is concealed deep underground,and the deposit is an stratabound skarn type Fe-Cu-Pb-Zn polymetallic deposit.