Geochronology and geochernistry of Paleozoic granitic plutons from the eastern Central Qilian and their tectonic implications

The Dongjiazhuang and Xindian Plutons are emplaced in Proterozoic metamorphic rocks of the Central Qilian.LA-ICP MS zircon U-Pb data indicate that the emplaced ages of these two plutons are Paleozoic.The plutons are peraluminous,showing characteristics of high K and K/Na,and low Mg,Fe,and Ca.The rocks are enriched in Rb,Th,Pb,LREE and depleted in Ba,Nb, Sr,P,and Ti,with Eu positive anomaly.Their(~(87)Sr/~(86)Sr)_i are respectively 0.7129 and 0.7106,ande_(Nd)(t)are-6.6 and-5.2. Based on these geochemical characteristics,we conclude that the plutons are S-type granites whose source rocks were metagreywacke, and their tectonic settings belong to syn-collision.