Neoarchean Crustal Accretion In The Western Shandong Province:Evidence From Granite,Granodiorite And Monzonite In Western Shandong

The Western Shandong Province(WSP)is aexclusive area where the TTG and greenstone belts of the early Neoarchean are completely preserved.It is a typical area for studying the types of Archean magma evolution,crust-mantle interaction and tectonic model of the Archean.Based on field geological surveys,wediscusses the geochemical characteristics and formation of Neoarchean granites,granodiorites and monzonitein western Shandong by means of trace element geochemistry,isotope geochemistry and isotope chronology.The U-Pb ages of Neoarchean granite,granodiorite and monzonitic in The Western Shandong Province(WSP)are mainly 2520Ma and 2560Ma.The?Hf(t)value of granite is-4.00?+6.35,the average is 1.42,the second-stage model age is about2.8Ga,the granodiorite?Hf(t)value is-1.61?+6.40,the average is 1.45,the second The age of the stage model is about 2.8 Ga,the?Hf(t)value of monzonite is-0.31?+4.69,the average is 2.33,and the age of the second stage model is about 2.8 Ga,indicating that the Neoarchean granite,granodiorite and monzonitie in the western Shandong area originated from the remelting product of the ancient crust of?28Ga.The Neoarchean granites,granodiorites and monzonitie in western Shandong are characterized by high Si O₂,high Al₂O₃ and rich Na₂O,all of which belong to quasi-aluminum rocks.In the standardization diagram of rare earth elements,they all show the enrichment of light rare earth elements(LREE)and the depletion of heavy rare earth elements(HREE),and the fractionation of medium and heavy rare earth elements.In the trace element standardization diagram,it is manifested as the enrichment of large ion stonephilic elements such as K,Rb,Ba and Th,and the depletion of Nb,Ta,and Ti.The Neoarchean granite,granodiorite and monzonite in the western Shandong area are syn-collision backgrounds,which are the effective accretion of continental crust.