The Metallogenic Regularity And Metallogenetic Prediction Of Au And Cu-Zn Polymetallic Deposits In The South Margin Of Western Altay Range,Xinjiang

The southern margin of Altay is located in the western part of the Central Asian Orogenic Belt,the Siberian plate and the northern margin of the kazakh-junggar plate convergence belt.Regional geological structure development experiences:pre-sinian continental formation stage,the early sinian period-late Paleozoic ocean basin formation and evolution of subduction and closing stage,late Paleozoic middle-late stage of continental plate collision,the Mesozoic Asian continental margin and Cenozoic intracontinental orogenic four complex evolutionary stages,is the important noble metals,nonferrous and rare metal collection area.The western part of the southern margin of Altay is characterized by the development of gold,copper-zinc polymetallic deposits.The typical VMS deposits are the Ashele copper-zinc deposit and the Sarsuk-gold polymetallic deposit.Mesothermal hydrothermal vein type deposits include Duolanasayi gold deposit,Tokuzibayi gold deposit and Jinba gold deposit.The VMS deposits are mainly produced in a set of volcanic sedimentary rocks/subvolcanic rocks of Ashele Formation.Mineralization generally experienced the superposition of Marine volcanic-syngenetic hydrothermal deposition and late deformation and metamorphic hydrothermal deposition.The mesothermal hydrothermal vein type deposits are mainly controlled by the secondary faults of the Maerkakuli ductile shear zone,and the mineralization generally experienced magmatic hydrothermal and metamorphic hydrothermal processes.Studies on fluid inclusions show that a large number of liquid-rich inclusions?LV type?,a small number of gas-rich inclusions?VL type?and daughter mineral inclusions?S type?are mainly developed in the quartz veins as well ore in VMS type deposit.The homogenization temperature of inclusion decreased gradually from early to late,and the salinity also decreased gradually.The H₂O-CO₂-NaCl system with medium temperature and low salinity in the early stage evolved into the hydrothermal solution of the H₂O-NaCl system with low temperature and low salinity in the later stage.A comprehensive study of isotopes C,H,O and fluid inclusions shows that the ore-forming fluid was the source of magma at the initial stage of mineralization,and seawater was mixed into the ore-forming fluid at the later stage.S and Pb isotopic data suggest that metallogenic materials are derived from magmatic hydrothermal fluids and strata.The inclusion types of the medium-temperature hydrothermal vein type gold deposits mainly include liquid-rich inclusion?LV type?,gas-rich inclusion?VL type?,CO₂-containing inclusion?LC type?and pure CO₂-containing inclusion?C type?.The homogenization temperature of inclusions decreased gradually from morning to night,and the salinity decreased gradually.Ore-forming fluid from H₂O-CO₂-NaCl system with medium temperature and low salinity gradually evolved into hydrothermal fluid of H₂O-NaCl system with low temperature and low salinity.The study of stable isotopes C,H and O shows that the ore-forming fluid in the early stage of the gold deposit is the source of magma,and atmospheric water is constantly mixed in the middle and late stage.The S and Pb isotopic values suggest that the metallogenic materials in the gold deposits are mainly from magmatic hydrothermal fluids and strata.Systematic studies on U-Pb dating of magmatic,volcanic and subvolcanic zircon and pyrite Re-Os isotope dating of major deposits in the study area show that the metallogenic ages of VMS type deposits are:Ashele copper-zinc deposit?342Ma?and Sarsuk gold polymetallic deposit?383Ma?.The metallogenic ages of the mesothermal hydrothermal vein type deposits are:Duolanasayi gold deposit,Tokuzibayi gold deposit and Jjinba gold deposit?300-290Ma?.The above results indicate that there are two stages of mineralization in the study area:?1?the mineralization of the Early middle Devonian-Early Carboniferous oceanic plate continuously subducting northward under the tectonic background of the Siberian plate.?2?mineralization in the extensional tectonic background of late Carboniferous-early Permian plate collision.The spatial and temporal distribution of different types of ore deposits is obvious.Spatially speaking,the VMS type and mesothermal hydrothermal vein type gold deposits are distributed in middle devonian,Ashele Formation and Tuokesalei Formation,moreover,the distribution of ore deposits is in the same direction as the fault extending in the NW direction,and the structure controls and influences the production of ore deposits in different degrees.The gold deposits are usually distributed along the edge of the intrusive body.The development of wall rock alteration with certain zonation also indicates the distribution of ore body.In terms of time,there are two stages of mineralization in the study area,namely the 380³40Ma Cu-Zn-Au polymetallic mineralization and290-300Ma gold mineralization.On the basis of systematically summarizing the metallogenic geological conditions and prospecting criteria of gold and copper-zinc polymetallic deposits in the study area,the spatial database for metallogenic prediction of different types of deposits in the study area was established by using the ArcGIS platform and the conceptual model for metallogenic prediction of gold and copper-zinc polymetallic deposits in the western part of the southern margin of Altay.Based on the spatial database,the ore-forming information was extracted,analyzed and the target area was delineated.Taking the quantitative spatial data analysis and integration method as the main line,metallogenic prediction of regional gold,copper-zinc and polymetallic deposits,geology,geophysical,geochemical exploration and comprehensive remote sensing information was carried out,and the metallogenic prospect area was delineated,Delineate five prospecting target areas of gold mineralization,In the copper-zinc polymetallic metallogenic four prospecting target areas.