Geological And Geochemical Characteristics And Genesis Of Granite Porphyry In The Zhalageamu Copper Deposit,Inner Mongolia

The Zhalageamu copper deposit is located in south of Xilinhot City of the Inner Mongolia Autonomous Region,which is the southern part of the southern slope of the Greater Khingan Range.The ore body occurred in the contact zone between the Permian Dashizhai Group and Permian granodiorite.Based on the systematic field geological survey and laboratory study,petrography,geochemistry,zircon U-Pb dating and Sr-Nd isotope analysis of the granite porphyry were studied in detail.So that the genetic types and formation age of the granite porphyry,and the relationship of granite porphyry and mineralization,petrogenesis and diagenetic metallogenic dynamics background can be identified.The geochemical data show that the granite porphyry of the Zhalageamu copper deposit are characterized by high SiO₂,Al₂O₃,with low Mg O,and granite porphyry exhibit pronounced enrichment of Rb,K,La,Th and depletion in Ta,Nb,Ti,P.All of the samples are characterized by the enrichment of LREE relative to HREE,and weak Eu negative anomaly,and?_Nd(t)values ranging from+2.1 to+3.3 and young Nd-model age(740?980Ma),.These data indicated that the granite porphyry belong to high-K,calc-alkaline I-type granite,the formation of granite porphyry original magma is related to the mixture of crust and mantle source material.Granite porphyry formation age is 255.2±2.0Ma,consistent with the tectonic-magmatic activity of Indo-China period in the south of the Greater Khingan.Referring to other previous research,we believe that the Zhalageamu copper deposit was formed in lithosphere extensional tectonic environment.Comprehensive study show that this region has entered the extensional tectonic environment after north China plate collides with the Siberia plate.The magma material formed from the lithosphere delamination and subsequent mantle-derived magma underplating and during the process of the magma material ascent to the crust shallow,due to the decrease of pressure and temperature,a large number of metallogenic elements and volatile components were separated out,then deposit in the contact zone between granodiorite and stratum,and in the surrounding rock fractures,that is key factor for deposit formation.