辽东半岛金家岭花岗岩体LA-ICP-MS锆石U-Pb年代学、地球化学特征及地质意义

LA-ICP-MS zircon U-Pb chronology,geochemical characteristics and geological significances of Jinjialing granite in Liaodong Peninsula

对辽东半岛凤城地区金家岭花岗岩体进行了LA-ICP-MS锆石U-Pb测年、主量和微量元素地球化学分析,进一步探讨了岩浆成因及构造环境。金家岭花岗岩为中细粒黑云母二长花岗岩,形成时代为早白垩世((127±1) Ma和(122±1) Ma);具较高的w(SiO_(2))(72.44%~77.30%),富碱(7.90%~9.05%),贫w(CaO)(0.48%~1.10%)、w(MgO)(0.12%~0.54%),铝饱和指数为0.87~1.07,为准铝质-过铝质过渡类型;稀土元素配分曲线右倾,轻稀土富集且分馏明显,重稀土相对亏损,无分馏,Eu具强烈负异常的特征,富集大离子亲石元素Rb、K和高场强元素Th、Hf,亏损Ba、Sr、P、Nb、Ta、Y。岩石类型为A1型花岗岩,岩浆可能来源下地壳的部分熔融,形成于伸展的构造背景中,与华北克拉通岩石圈减薄密切相关。

LA-ICP-MS zircon U-Pb dating and geochemical analysis(major and trace elements)of Jinjialing granitic pluton in Fengcheng area of Liaodong Peninsula have been carried out,in order to reveal its petrogenesis and tectonic environment.The Jinjialing granite is a medium-fine grained biotite monzogranite,which was formed in Early Cretaceous((127±1)Ma and(122±1)Ma).It is characterized by high w(SiO_(2))(72.44%~77.30%),rich alkali(7.90%~9.05%),poor w(CaO)(0.48%~1.10%)and w(MgO)(0.12%~0.54%),with aluminum saturation index of 0.87~1.07,which belongs to metaaluminous to peraluminous transition type.The REE distribution pattern is right-leaning,and the LREE is enriched and fractionated obviously,while the HREE is relatively depleted without fractionation.It shows strong Eu negative anomalies,with enrichments of large ion lithophile elements of Rb,K and high field strength elements of Th,Hf,depletions of Ba,Sr,P,Nb,Ta,Y.The above geochemical features indicate that the Jinjialing granitic pluton belongs to A1-type granite.The magma may have originated from partial melting of the lower crust and was formed in an extensional tectonic setting,which is closely related to the lithosphere thinning of the North China Craton.