Metallogenesis Study Of Huayuan MVT Type Pb-Zn Ore Concentration Area,Hunan

The Huayuan lead-zinc deposit is the most representative super-large lead-zinc deposit in the western Hunan-western Hubei Pb-Zn metallogenic belt.The prospect reserves are more than 10 million tons,the lead and zinc grade is high,the scale is large,has high economic value and study value.In this paper,the geochemical characteristics of trace elements and rare earth elements,S,Pb,Sr,C,H,O isotopic geochemical characteristics and fluid inclusions were analyzed systematically based on the geological characteristics of the regional geological and ore deposits.The mineralization of the Huayuan lead-zinc deposit is discussed from the source of ore-forming material,the source of ore-forming fluid,the relationship of stratigraphy,structure,and organic matter with mineralization.On the basis of this theory,the genetic model of deposit is established,and the low temperatured mineralization of western Hunan-western Hubei metallogenic field is discussed.The sphalerite and galena in the lead zinc deposit in Huayuan ore field are the sedimentary hydrothermal transformation genesis related to the brine of the basin.The sulfide contains dispersed elements,and the cadmium content in sphalerite is abundant,it is the typical characteristics of MVT type lead zinc deposits.The REE composition of ore minerals and surrounding rocks is quite different.The total REE content of the former is obviously lower than that of the latter,and the ore bearing strata are not the main source of ore-forming materials.The reduction of sulfur in lead-zinc ores mainly comes from the reduction of the formation of marine sulfate.The lead isotope probably originates from the Ordovician-Cambrian strata.Strontium isotope ratios of ore-forming fluid is higher than that of ore bearing strata,the waterrock reaction and isotope exchange happened when metallogenic fluid flows through the shale of Niutitang Formation which with high strontium isotope ratios.The Systematic C,H and O isotope study results of the calcite and sphalerite in the main mineralization period show that 13 C,18O isotopes of calcite in the main ore-forming period in the Tuanjie,Li Mei,Tudiping,Fengtang and the Dashigou deposits show successively decreasing characteristics.The C in the ore-forming fluids of lead-zinc deposits mainly comes from the dissolution of marine carbonate rocks.The main source of ore-forming fluids is the construction water and atmospheric precipitation.Ore-forming fluid of Huayuan lead-zinc deposits is hot-brine solution with low temperature,medium and high salinity,high density,sodium and calcium chloride mainly.The homogenization temperature of ore-forming fluids has a tendency of decreasing from north to south,and the migration direction of ore-forming fluids is shown.CO2,CH4 and H2 are developed in the vapor phase of fluid inclusions.Sphalerite,galena,calcite,fluorite and other gangue minerals should be the precipitation products of the same ore-forming fluids with ore elements.The geological age of the Limei lead-zinc deposit in the Huayuan area is the Middle Ordovician,and the geological age of the Shizishan lead-zinc deposit is early Devonian.The calcite may be formed in the Late Cambrian.The multi-stage mineralization occurred in the Caledonian period,and the mineralization age was later than the ore-bearing surrounding rock.The distribution of lead-zinc deposits in Huayuan area is obviously controlled by lithology,stratigraphy and lithofacies.The metallogenic model is divided into ore-forming fluid formation stage and metallogenic hydrothermal migration enrichment stage.The first stage occurred in the basin burial and tectonic extrusion period.Deep fluid,formation water and meteoric water mixed with extensive water/rock reaction to form ore-forming fluids rich in zinc and other metal elements.The second stage occurred in Stretched tectonic environment,the ore-forming fluids happened large-scale migration,and the thermochemical sulfate reduction reaction occurred,ore minerals precipitated and mineralized at the edge of the platform and other favorable parts.The ore-forming fluid in Western Hunan-Western Hubei is low temperature,middle-high salinity,high density hot brine composed of sodium and calcium chloride.The lead zinc deposits in this area are the result of mineralization by extensive low temperature fluid,it may be related to the large-scale fluid flow in the basin caused by the tensional rift in Southern China area.