Petrogeochemistry, Zircon U-Pb Dating and Geological Significance of Two-Mica Granites from Wuduoshan Granite in Nanzhao County, Eastern Qinling Mountains
Li Kaiwen
Fang Huaibin
Guo Jungong
Liu Kun
Zhao Huan
Wang Xiaojuan
Abstract：The Qinling orogenic belt, located in the suture zone of the North China Plate and the Yangtze Plate, has undergone a complicated tectonic evolution process however, its plate combination mechanism and collision time limit have been controversial.In this study, petrogeochemistry analyses and LA-ICP-MS zircon U-Pb dating are undertaken for the two-mica granites from Wuduoshan in Nanzhao County, eastern Qinling mountains.Results show that the two-mica granites have SiO2=69.32％-74.28％, Al2O3=14.14％-17.28％, Na2O+K2O=7.68％-9.03％, and belong chemically to peraluminous series of S type.Meanwhile, the two-mica granites have a moderate amount of rare earth elements, with medium fractionation characteristics between light rare earth elements and heavy rare earth elements and medium negative Eu anomalies.The trace elements diagram shows enrichment of large ion lithophile elements (LILEs) and depletion of Ba, Nb, Sr, P and Ti, indicating that the two-mica granites may have been formed in the thickened crust caused by the collision between continents.Zircons from the two-mica granites in this study display fine-scale oscillatory growth and high ratios of Th/U (>0.4) , indicating a magmatic origin.The dating of the two-mica granites yields a LA-ICP-MS zircon U-Pb age of 433±2Ma.Combined with constructional environment, it is concluded that it was transformed from plate subduction to continental collision in the Nanzhao County at late of Early Silurian.
Keywords：two-mica granitespetrologygeochemistryLA-ICP-MS zircon U-Pb datingNanzhao Countyeastern Qinling mountains
Publication Date：2019-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：12( 123-134 )