Study On The Origin And Genesis Of Metallogenic Materials In Baiyun Gold Deposit In Eastern Liaoning Province

The Qingchengzi polymetallic ore concentration area is located in the southeast of Liaodong Peninsula and occurs in Liaodong rift depression.It belongs to the northeast of North China Craton and is an important Pb Zn Au Ag polymetallic ore field in North China.The study shows that the Late Triassic granitic magmatic events,represented by the biotite monzogranite and the Xinling granite in the mining area,should be closely related to the mineralization in this area.The study area is a large magmatic activity area of Late Triassic,mainly composed of granite,lamprophyre and diorite dyke.The Late Triassic mafic magmatism combined with contemporaneous granites provides a window for the early geodynamic changes of the North China Craton.Based on the study of the geochemical characteristics of the Triassic intrusive rocks?including biotite monzonite,quartz diorite porphyrite,quartz monzonite,granite porphyry,lamprophyre,diorite,etc.?in the Qingchengzi Ore Concentration Area,such as the major elements,trace elements,rare earth elements,Sr and Pb isotopes,as well as the chronology and petrography,the genesis and origin of magma and the tectonic environment are explored The relationship between Triassic intrusive rocks and gold polymetallic mineralization is discussed.The chemical composition of the Qingchengzi intrusive rock:Si O₂ is 40%?78.58%,K₂O is 3.53%?5.22%,Na₂O is 3.87%?4.14%,belonging to calc alkaline rock series.Al₂O₃ is in the range of7.6%?15.84%,and A/CNK is mostly less than 1,which is quasi aluminum.Trace element data show that the total amount of rare earth is relatively high,and the fractionation of light and light rare earth elements is relatively obvious,[?La/Yb?N=6.00?102.81,LREE/HREE=4.8?40.7],Eu negative abnormality is obvious??Eu=0.19?1.25?,there is also unobvious Eu positive anomaly.Rich in large ion lithophile elements Rb,Th,U,K,Ba and so on,while loss of high field strength Elements Nb,Zr,Hf,P,Ti and so on.Characterized by high Sr,Ba content and low Y,Yb content,it belongs to A-type granite with adakitic affinity and high Nb/Ta ratio?7.24?30.43?.Sr-Nd-Pb isotopic characteristics show that the magma of Triassic intrusive rocks in the area is derived from the mixture of crust and mantle.The above geochemical characteristics indicate that the magma source area may originate from the partial melting of the thickened lower crust,and may be mixed with the mantle derived basic magma.Combined with the regional geological background,it is inferred that the plate fragmentation during the deep subduction of the Yangtze and North China plates may be the geodynamic cause of the magma related to mineralization.Granites and dykes in the area are closely related to gold polymetallic deposits.Granitic magmas provide ore-forming materials,heat sources and fluid sources for gold polymetallic mineralization.