Metallogenic Characteristics And Genesis Of The Huachangshan Lead-zinc Polymetallic Deposit In Yunnan

The Huachangshan lead-zinc polymetallic deposit is located in the eastern margin of the Tibetan Plateau and is a lead-zinc polymetallic deposit in the thrust structure system of the Lanping Basin.It is representative of the MVT lead-zinc deposits in the regional fold and thrust belt.This paper finds out the geological characteristics of the deposit,the characteristics of ore-controlling structures,the characteristics of ore-forming fluids and the source of ore-forming materials,and proposes the ore-forming model of the deposit.The ore body controled by secondary faults and occurs in the limestone strata.The mineral assemblage including sphalerite,galena,tetrahedrite series minerals,stibnite,calcite,quartz,etc.The sulfide mainly exists in the form of vein-like cemented limestone/calcite.Three sets of faults with different attributes were identified by cataloging key flats,and correspondingly developed three different hydrothermal fluids:mineral-free fluid,copper-silver fluid,and lead-zinc fluid.The three sets of fluids all develop hydrothermal mineral calcite.The in-situ rare earth element analysis of the third-stage calcite found that the third-stage fluids are all hydrothermal fluids.The different REE distribution,different Y/Ho-La/Ho distribution and different Yb/Ca-Yb/La distribution indicate that the three phase fluids have different sources or homology but are modified by different effects.The carbon,oxygen and hydrogen isotope characteristics indicate the carbon comes from the dissolution of marine carbonate rocks,where organic water is mixed in the fluids of the carbonate period and the copper-silver metallogenic period,and atmospheric precipitation is mixed in the fluid of the lead-zinc metallogenic period.Through isotopic analysis of sulfur in sulfide and sulfate minerals,the?³⁴S_V-CDTvalues in sulfides are all negative,and the range of variation is large,indicating that the sulfur in the copper-silver period and the lead-zinc-antimony period is mainly BSR;mineral-forming sulfur mainly comes from the sedimentary strata containing sulfate and organic matter in the basin.This paper tests the lead isotopes in in-situ sulfides and collects previous test results to comprehensively compare the Meso-Cenozoic sedimentary strata,basement strata,arc magmatic rocks at the edge of the basin,and new generation on the east side of the basin.The source of lead in the Huachangshan lead-zinc-copper-silver deposit is more complex,mainly from sedimentary strata(Cretaceous and Tertiary),arc magmatic rocks(Middle Triassic)at the edge of the basin,and the Cenozoic high-potassium magmatic rocks(syenite porphyry and syenite)on the east side of the basin.