摘要
以辽东地区大兴岩体为研究对象,对花岗岩的岩石学、岩石地球化学以及锆石U-Pb年龄进行了研究,确定了花岗岩形成的时代,探讨了花岗岩的岩石成因及构造意义。结果表明：大兴花岗岩中锆石具有典型的岩浆振荡生长环带和较高的w（Th）/w（U）值（0.54~1.27）,反映了岩浆成因特征;LA-ICP-MS锆石U-Pb定年结果为（120±1）Ma,表明大兴岩体主要形成于早白垩世晚期;地球化学特征显示大兴花岗岩为过铝质高钾钙碱性花岗岩,具有富Si,富碱和贫CaO、Fe2O3、MgO和P2O5的特征,以及稀土元素含量较高,轻稀土元素相对富集和重稀土元素相对亏损的特征,Eu负异常较为明显,稀土元素配分模式具有右斜＂V＂字型的特征,明显富集Rb、Th、U、Ta、Hf、Gd等元素,亏损Ba、Sr、P和Ti等元素;花岗岩熔体的锆石饱和温度（724℃~816℃）明显低于白垩纪A型花岗岩（868℃~928℃）。以上特征表明,辽东大兴地区花岗岩应属于高分异I型花岗岩,形成于局部伸展拉张构造背景。
The petrology,geochemistry and zircon U-Pb ages of Daxing pluton in Liaodong area were studied,and the formation ages of granites were measured,and the petrogenesis and tectonic significance of granites were discussed.The results show that the zircons of Daxing granite have the characteristics of oscillatory growth zonation of typical magmatic origin and high ratios of the contents of Th and U（0.54-1.27）,indicating a magmatic origin for the zircons;LAICP-MS zircon U-Pb age of Daxing pluton is（120±1）Ma,showing that the granites are formed in the late Early Cretaceous;geochemical characteristics suggest that Daxing granite is peraluminous high-K calc alkaline,and is featured by high SiO2 and alkaline,and low CaO,Fe2O3,MgO and P2O5,and high rare earth element（REE）;the chondrite-normalized REE pattern with right oblique and V-shaped feature is characterized by enrichment of light rare earth element（LREE）relative to heavy rare earth element（HREE）and distinct negative Eu anomalies,and Rb,Th,U,Ta,Hf and Gd are enriched,and Ba,Sr,P and Ti are depleted;zircon saturation temperatures（724 ℃-816℃）of granite melt are significantly lower than Cretaceous A-type granites（868℃-928℃）.These characteristics indicate that the granites in Daxing area of Liaodong should belong to highly fractionated I-type granites,which are formed in local extensional tectonic surrounding.
出处
《地球科学与环境学报》
CAS
2016年第5期623-637,共15页
Journal of Earth Sciences and Environment
基金
国家自然科学基金项目(41272223)
中国地质调查局地质大调查项目(1212011220247)
