Metallogenesis,Ore-Controlling Factors And Prospecting Direction Of The Daqingshan Gold Deposit In Beishan Area,Xinjiang Province

The Daqingshan Au deposit is located in Daqingshan-Hongshijing-Baishan gold-copper-iron-salt metallogenic belt,in the west section of southern subzone of Beishan Paleozoic rift,the northeast edge of Tarim plate.For a long time,most studies on the Daqingshan ore deposit were focused on geological characteristics,the metallogenic age,feature and source of metallogenic fluid system,and ore genesis even no research has been carried out.Therefore,the prospecting work of this area and other similar areas in this metallogenic belt have been restricted to some extent.Based on comprehensive field investigations and synthetic studies on metallogenesis and ore-controlling factors by applying multiple disciplines and methods such as tectonic geology,petrology,mineralogy,mineral deposits,element geochemistry,fluid inclusions geology and isotope geology,the metallogenic laws of the deposit are concluded in this paper.Furthermore,the ore prospecting orientation was proposed in this district.The deposit is hosted by early Carboniferous metamorphic rocks of Hongliuyuan formation.Their protoliths were graywacke,subgraywacke,feldspar sandstone and claystone.Three periods of metamorphisms and deformations were identified,corresponding with three quartz veins in this area.Among these,quartz veins of the second period are the main gold-bearing quartz veins.The gold veins controlled by Kuluke brittle-ductile shear zone and a series of secondary faults,whose strike is NEE.There are two types of ore in the mineral deposit,quartz vein and altered rock.Native gold,arsenopyrite,pyrite,chalcopyrite,galena,sphalerite,pyrrhotine,covellite and hematite are primary metallic minerals in the ore,while quartz,sericite,calcite,chlorite,ankerite siderite and albite are main non-metallic minerals.Wall rock alterations are dominated by silicification,sericitization,pyritization,arsenopyritization,chloritization,albitization and carbonatization.Fluid inclusion and isotope studies indicate that quartz veins in the Daqingshan gold deposit mainly contain liquid-vapor two-phase aqueous inclusions and CO₂-H₂O three-phase inclusions.The ore-forming fluids of main mineralizing stage belonged to the H₂O-CO₂±CH₄±N₂ system of medium-high temperature（205⁴23℃）,low salinity（0.22⁸.80 % NaCleqv）and medium density（0.55⁰.85 g/cm³）generally.The ore-forming fluid mainly derived from metamorphism,and isotope exchange occurred between fluid and wall rock.Fluid immiscibility was considered to be the primary mechanism leading to precipitation of ore-forming elements.Mineralization occurred in Early Permian（274 Ma）,this age is consistent with the forming epoch of metamorphic zircon of host strata（269.6 Ma）.Metallogenic materials mainly derived from the Sanfengshan VMS Cu deposit and its ore-hosting basalt.The Daqingshan ore deposit shows features of orogenic gold deposits mineralized in regional metamorphism of late Hercynian period.The integrated study suggested that the Daqingshan gold deposit is controlled by the factors such as strata,structures,country rock alteration etc.Based on this,tectonism-mineralizaiton is discussed,and genetic model is established.Num.4,37,41,68,104,109 and 115 veins have a good ore prospecting potential.