Geological Characteristics And Metallogenesis Of Erdaohezi Pb-Zn Deposit,Inner Mongolia

Erdaohezi Pb-Zn deposit which is situated between the Eurguna Block and Xing’an Block,belongs to the Shanghulin-Xijinuo Metallogenic Subzone lying at the middle part of the Deerbugan metallogenic belt.And this area has good metallogenic conditions and is rich in mineral resources including several middle-large scale Pb-Zn deposit.The mainly exposed stata in mining are Middle Jurassic Tamulangou Formation volcanic strata and quaternary deposition.Volcanic rock strata is gentle,there are andesite volcanic rocks,rhyolite,crystal tuff,tuff,tuffite and volcanic breaaia,alsofrit lithic crystal tuff,sandstone and conglomerate.Regional Deerbugan deep fault through the Southeastern mining,Tectonic framework secondary structure of deerbugan fault is the main structure of the mine.NW-trending faults are well developed and form three broken belt,NW-trending faults control the output of the ore,but NE-trending faults damage ore in varying degrees.Faults have the characteristics of multi-period activities.Mineral deposit is composed by three belts,these ore bodies with lenticular and vein-shape with enlargement and systolic characteristics occurrence in NW-trending faults of Tamulangou stata.Ore body shape is controlled by faults,occurrence of the ore is stable and the ore body have the characteristics of swelling shrinkage at the local area,hickness of the ore body is thicken at the fracture meeting place.Metallic minerals in Erdaohezi Pb-Zn deposit are mainly pyrite,chalcopyrite,dalena,sphalerite,and gangue mineral are mainly quartz,chlorite,calcite,sericite and so on.Major textures of ores are metasomatic texture,hypidiomorphic texture and exsolution.The ma jor structure are vein-stockwork structure,disseminated structure,lumpy structure. The wa ll rock alteration are silicification,sericitization,carbonation,chloritization,and silicification is closed with mineralization.The mineralization can be divided into two periods:the h ydrothermal period and the supergene period, and the hydrothermalperiod can be divid ed into quartz-pyrite stage,quartz-polymetallic sulfide stage and quartz-carbonate stage.Geochemical studies indicate that the most rock pertains to high-k calc-alkaline series and dikes belong shoshonite series,rock with clear REE differentiation features highly enriched LILE and loss HFSE.Reference former isotope data shows that andesites anddikes volcanic rocks originated from the mantle and the involvement of crustal material,but acidic volcanic rocks is the result of partial melting of the crust.Mining volcanic rocks probably formed in tectonic environment of comtinental piate.Liquid and gas-rich inclusions are two main types of inclusions in Erdaohezi Pb-Zn deposit,the homogenization temperature of quartz is between 77℃ ~ 384℃,mainly concentrated in 250℃~ 270℃ and 310℃~ 330℃,the homogenization temperature of sphalerite is 254℃,so 250℃~270℃ basically represents the main mineralization stage temperature.The mineralization fluids are characterized by middle temperature,low salinity and low density, fluids pressure is between 17.85Mpa~31.15 Mpa and mineralization depth is between 0.66km~1.15 km.Mining presence multiperiodic fluid activity and mineralization fluids have evolved to the low temperature characteristics Fluid inclusion composition tests show that mineralization fluids is CO2-H2O-NaCl system and rich in deep source gas,reference regional data of S,Pb,H,O isotope speculate that forming materials comes from the deep earth and that mineralization fluids are mainly composed of magmatic water and atmospheric water.The research demonstrates that the Erdaohezi Pb-Zn deposit which is controlled by fault and closely related to Volcanic-subvolcanic hydrothermal,is a middle-low temperature hydrothermal lead-Pb-Zn deposit formed in continental intaraplate extensional tectonic environment.