Research On The Minerals And Source Of Ore-forming Fluids Of The Luziyuan Iron-copper-lead-zinc Polymetallic Deposit In Western Yunnan

The Luziyuan lead-zinc-iron polymetallic deposit is located in the southern part of the Baoshan block and is one of the important lead-zinc deposits in the Baoshan block.The formation of the deposit is closely related to the evolution of the Baoshan block and its tectonic belts.The study shows that the structural and magmatic activity are complex,and the structure and magmatism of the Hualixi,Indosinian,Yanshanian and Himalaic periods had varying degrees of impact on the production of deposits.Comprehensive REE,fluid inclusion data,S and Pb isotopes,source of mineral deposits and minerals,and analyse the evolution of tectonic frameworks in the mining area to have a detailed analysis of the properties,migration characteristics and sedimentation mechanism of ore-forming fluids.Finally,the minerals and fluid sources are summarized in relation to the ore-bearing strata and the relationship between magmatism and mineralization in each period,and the understanding of the genesis of the deposit is proposed.The main knowledge gained is as follows:(1)Characteristics of rare earth elements show:(1)The enrichment degree of rare earth elements from marble to mineralized marble to ore to the skarn increases sequentially,which may be related to the decrease of erosion intensity when fluid temperature and salinity reduce;(2)The values of ?Ce and ?Eu in the ore samples are all less than 1,suggesting that the sulfides are mainly formed in the reducing environment;(3)The distribution curves of rare earth elements of core is quite similar with the rare earth distribution curves of Zhibenshan and Kejie granites,reflecting the formation of this deposit is related to the regional magmatism activity,which also proves that the deep concealed granite in the mining area is closely related to the formation of the deposit.(2)The Zircon U-Pb dating study of the Muchang granite shows that the diagenetic age is 240.5±3.7 Ma(MSWD=0.48),which is the product of Indosinian movement.(3)Combined analysis of isotopes,rare earth elements,inclusions and other previous study shows that:(1)the early ore-forming fluids in this area are mainly derived from the magmatic hydrothermal fluids of the concealed granites,In the later period,a large amount of groundwater was added.(2)The main source of minerals is the hidden granites in the deep part of the mining area;(3)The sedimentation mechanism of ore in different ore-forming stages is mainly the decrease of temperature and salinity of ore-forming fluids,boiling of local fluids and water-rock reaction;The bottom-up temperature,salinity,and pressure gradient differences drive the migration of fluid to the surrounding rock from the top of the deep concealed rock mass.(4)The fluids and minerals of the Luziyuan deposit mainly originate from the hidden granite body,but it is not the only source.The initial source layer of the Shahechang Formation and the magma activities of Hualixi period-Indosinian-Xishan period may also provide part of the minerals or ore-forming fluid.Luziyuan ironcopper-lead-zinc polymetallic deposit is formed by multi-stage superimposed mineralization.