吉林中部红旗岭北沟花岗岩锆石U-Pb定年、地球化学特征及其地质意义

摘要

对华北板块北缘碰撞造山带东段吉林中部红旗岭北沟花岗岩岩体进行了岩相学、地球化学和LA-ICP-MS U-Pb定年研究.锆石测年结果显示红旗岭北沟花岗岩的结晶年龄为263 Ma,形成于中二叠世晚期.北沟花岗岩为准铝质高钾钙碱性I型花岗岩类,富集轻稀土(LREEs)和大离子亲石元素(LILEs,Cs、Ba、K和Sr),亏损重稀土(HREEs)和高场强元素(HFSEs,Nb、Ta和Ti),同时显示埃达克岩的地球化学特征,为加厚镁铁质下地壳部分熔融的产物.花岗岩的侵位暗示了中二叠世晚期在吉林中部可能已经发生了华北板块北缘东段与松嫩地块的初始碰撞.%Petrography,geochemistry and LA-ICP-MS U-Pb dating of Beigou granites have been obtained in central Jilin of the northern margin of North China plate.LA-ICP-MS zircon U-Pb dating indicate that the granites from Beigou pluton formed during the later period of Middle Permian(～263 Ma).Beigou granites belong to calc-alkaline,metaluminous I-type granites with high K2O content.They show strong enrichment in LREEs and LILEs(Cs,Ba,K and Sr),depletions in HREEs and HFSEs(Nb,Ta and Ti),with geochemical characteristics of adakite.The primary magma for Beigou pluton could be mainly derived from partial melting of the thickening mafic lower crust.The emplacement of Beigou pluton indicated that the initial collision in central Jilin between the north-eastern margin of the North China Plate and the Songnen terrain occurred during the later period of Middle Permian.