The Characteristics And Evolution Of Ore-Forming Fluids Of Pb-Zn-Cu-Ag Deposits In Lanping Basin

The Lanping basin is located in westerm Sanjiang Tethys experieced a complex tectonic evolution process.There is few study for the whole ore-forming fluids of deposits in Lanping basin.In this paper,we will aim at the deposits in Lanping basin,while paying particular attention to Jinman-Liancheng and Baiyangping deposits.Based on analyses of fluid inclusions,we combine the pre-researches of fluid inclusions and C-H-O isotopes,focusing on the source of ore-forming fluids and the relationship of ore-forming fluid and mineralization.The main conslusions are as follows:(1)There exist three types deposits in Lanping Basin:Mesothermal vein type Cu-Ag-Pb-Zn deposits,the Mississippi Valley-Type Pb-Zn deposits and epithermal Sb-Hg-As deposits.The age of Cu mineralization of mesothermal vein type deposits mainly range from 56Ma to 46 Ma.The mineralization age of epithermal Sb-Hg-As deposits range form 40Ma to 33Ma.The age of Pb-Zn mineralization of mesothermal vein type and the Mississippi Valley-Type Pb-Zn deposits mainly range 33Ma to 21Ma.(2)The homogenization temperature of mesothermal vein type Cu-Ag-Pb-Zn deposit primarily range from 120.0?320.0?with the salinity of 2.00?24.00%,indicating basinal the source of ore-forming fluids are basinal brines.However,influenced by the collision of Indian and Eurasian plate,the ore-forming fluids of Jinman-Liancheng deposit was influenced by a minor CO₂-bearing metamorphic fluids;Fluid inclusions of the Mississippi Valley-Type Pb-Zn deposits have characterized by homogenization temperature of 100.0?200.0?and salinities of 4.00?16.00%,revealing that ore-forming fluids are from basinal brines;Epithermal Sb-Hg-As deposits,as an example of Bijiashan Sb deposit.Fluid inclusions have characterized by homogenization temperature of 120.0?160.0?and salinities of 0.00?6.00%,indicating the existence of meteoric water.