Geochronology,geochemistry and genesis of the Qingxi complex pluton in Dongyuan,Guangdong Province
By means of LA-ICP-MS zircon U-Pb dating,zircon Lu-Hf isotope testing,and major and trace element analysis,it is revealed that two main lithologic types of the Qingxi complex pluton in Dongyuan area,Guangdong are medium-fine grained(porphyritic)biotite monzonite granite(J1c3 ηγ)and coarse medium-grained biotite monzonite granite(K3b1ηγ),whose weighted average ages are(158.2±1.3)Ma and(112.8±2.9)-(116.1±1.7)Ma,respectively,indicating that the Qingxi complex pluton was formed in the Late Jurassic and the Early Cretaceous.Their geochemical characteristics are high silica(SiO2 mass fraction is 74.32％-78.73％),quasi-aluminous-peraluminous(A/CNK is 0.97-1.08),high differentiation(DI is 92.55-94.78 and Zr/Hf is 17.9-26.3).They are enriched in Rb,Th,U,La,Nd,Sm,Lu and LREE,and deficient in Ba,Nb,Sr,P and Ti.The Eu values of the two intru-sions are obviously negative(δEu is 0.1,0.1-0.2 respectively),and the 104Ga/Al is high(104Ga/Al is 2.68-2.79,2.90-3.79).The geochemical characteristics indicate that the Qingxi complex pluton belongs to aluminous A2-type granite with high differentiation.εHf(t)values range from-8.6 to 6.9,with most values ranging from-6.7 to-0.3 and corresponding TDMC ranging from 0.73 to 1.76 Ga.Comprehensive analysis shows that the Qingxi complex pluton was formed in the extensional tectonic environment of the late Yan-shan period when the paleo-Pacific plate subducted and the crust thinned.The Qingxi complex pluton was the product of partial melting of the ancient lower crust and the mantle rock under the high-temperature heat flow.
A2-type granite with high differentiationisotopic agegeochemical characteristicQingxi complex plutongenesisDongyuan in Guangdong
万方数据
维普
