吉林中部梨花沟石英闪长岩锆石U-Pb年龄和岩石地球化学特征OA

To explore the final closure time of the eastern segment of the Paleo-Asian Ocean,this study focuses on the quartz diorite in the Lihuagou area of central Jilin,analyzing its geochemical characteristics and zircon U-Pb ages.LA-ICP-MS zircon U-Pb dating results indicate that the crystallization age of the Lihuagou quartz diorite is Late Triassic(208±2 Ma).The rock is rich in silicon,aluminum,calcium,and sodium,but poor in iron,magnesium,and potassium.The rare earth elements exhibit a rightward sloping distribution,with weak Eu anomalies(δEu=0.63～0.92).Trace element characteristics show enrichment of large-ion lithophile elements(such as Rb,Ba,Eu)and depletion of high-field strength elements(such as Ta,Nb,Ti).The low Cr(17.7× 10-6～45.2 × 10-6),MgO(1.32％～2.36％),and Mg#(42～44)values suggest that the magma source mainly originates from partial melting of the lower crust.The Nd/Th(1.81～4.66)and Rb/Sr(0.09～0.40)ratios indicate the involvement of mantle-derived components during its formation.Based on previous studies,it is inferred that the eastern segment of the Paleo-Asian Ocean closed in the Early to Middle Triassic,with post-collisional extension occurring in the Late Triassic.The geochemical characteristics of the Lihuagou quartz diorite suggest that its formation is related to extensional tectonic activity following the closure of the Paleo-Asian Ocean.