Geological And Geochemical Characteristics Of Granitic Rocks From The Tongshan Copper Deposit,Heilongjiang Province

The Tongshan copper deposit is located in Nenjiang County in Heilongjiang Province.Its tectonic position belongs to the Early Paleozoic continental margin(Duobaoshan Ordovician island arc type active belt)located in the northern Daxing'anling.The deposit is one of the most important porphyry copper deposits in the Dabaoshan Ore field.To find the metallogenic background of Tongshan copper deposit,major,trace,rare earth element and chronology of granitic rocks from the deposit are studied in detail.The granodiorite sample of ZK64-4 zircon SHRIMP U-Pb dating results show that the concordant age is 490 ± 6Ma,which is close to 521 ? 476 Ma of the molybdenum dating data in Tongshan area.Combined with the regional structure of the background,the mineralization of the Tongshan copper started since the early Ordovician.Zircon SHRIMP U-Pb dating of the granodiorite sample of TS03(in the middle of the orebody)gave concordant age of 234 ± 4Ma,which indicates that the granodiorite is late than mineralization.This is consistent with the geological fact that cut through the ore body.By using CIPW and QAP,the granite rock proves to be quartz monzonite and monzonite granite.The geochemical data show that the granitic rock has the characteristics of low silicon,high potassium,high aluminum,high sodium,high magnesium and high calcium,and the rock belongs to the calc-alkaline sequence.And it's relatively lack of Nb,Ta,Ti and other high field strength elements,and rich in Sr,K,Hf and other lively LILE.In addition,The both show the relative enrichment of LREE.Fractionation of LREE and HREE is not obvious.?Eu average is 0.92.Positive Eu anomaly is very weak.Based on the analysis of the characteristics of major,trace and rare earth elements,it is concluded that the granitic rock mass in the mining area is formed in the tectonic environment after the plate collision and the plate transition after the collision,but also has the geochemical characteristics of volcanic arc granite.Combined with the tectonic setting,it is considered that the tectonic setting of the granitic rock mass is the volcanic arc environment.