A Study On The Mineralizing Fluid,Ore-bearing Geochronology And Geochemistry Of Wulunbulake Copper Deposit In Xinjiang,China

Wulunbulake copper deposit located at the Yemaquan-Qiongheba Cu-polymetallic metallogenic belt,eastern Junggar,Xinjiang,which is the representative deposit to syudy the mineralization regularities of porphyry copper deposit.However,their research level were lower,lack of the study on the characteristics of mineralizing fluids and precise chronology of rock mass,which leads to great differences in the evolution of mineralizing fluids,the genetic type,the host rock and mineralization age.Therefore,this study selected Wulunbulake copper deposit as the research object,study on the geological characteristics,fluid inclusions,zircon U-Pb dating and geochemistry,summarize the ore geological characteristics and fluid inclusions characteristics,determine the rock-forming age and ore-forming age,explore the geological background and the evolution of mineralization,The main results are followed:?1?The ore-bearing and country rocks are quartz diorites,which is controlled by fractures and distribution to?N?NW-SE in the plane,the ore body produced in the quartz diorites as lamellar,veined and lenticular.Ore minerals are mainly chalcopyrite,pyrite,bornite etc;Ore structure mainly for the xenomorphic granular texture,intersertal texture,metasomatic texture.Structure of ores is disseminated structure,veinlet structure,mesh-vein structure.According to the characteristics of mineral assemblages,the mineralization is divided into the porphyry period,hydrothermal period and supergene stage.The alteration of country rock is development and from the interior to the outer part of this deposits is silica alternation-potassic alternation,phyllic alternation,and propylitization.?2?The dominant fluid inclusions in Wulunbulake copper deposit is liquid-rich type,with low homogenization temperature?136.9²24.5??,low salinity?1.7%⁵.6%NaCleqv?and low density?0.97¹.01 g/cm³?,the mineralizing pressure between 2.76×10⁷⁴.49×10⁷ Pa and the corresponding depth between 1.04¹.95km,indicating that the deposit belongs to shallow environment.The ore-forming fluids component is relatively simple,the liquid phase is H₂O and inclusion gas is CH₄,N₂ and H₂.?3?LA-ICP-MS zircon U-Pb dating results show that the formation age of ore-bearing quartz diorite is 440.5±3.3Ma and 430.3±2.3Ma,belongs to early-middle Silurian,the quartz porphyry is 419.7±3.3Ma,belongs to late Silurian.?4?The element geochemistry study show the rocks are rich in SiO₂?64.92%,70.49%?and Al₂O₃?16.12%,15.14%?,relatively poor in MgO?2.32%,1.53%?,TiO₂?0.70%,0.30%?and P₂O₅?0.20%,0.09%?,which belong to peraluminous,calc-alkaline granitoid.The rocks have low?REE and LREE is more enriched than HREE,the fractionation degree of LREE is more obvious than HREE,no Eu and Ce anomaly;The content of LILE such as K,Sr is enrich and HFSE such as Ta,Nb,Ti is low,which is similar with typical island arc magmatic rocks;the trace elements?Rb,Y,Ta,Hf?diagrams for discrimination of structural environment show that the rocks were formed in island-arc tectonic setting.?5?The petrography and mineralogy study indicate the formative time?mainly during Silurian?of mineralization and magmatic rocks is basic period or later,related to the southward subduction of the Paleo-Asian oceanic crust in the Early Paleozoic Era.Through domestic and international famous porphyry copper contrast,found Wulunbulake copper deposit and they have the similar geological setting of mineralization,fluid properties and geological features,indicate Wulunbulake copper deposit is a typical porphyry copper deposit.