摘要
辽东凤城地区出露的大面积花岗岩一直是华北克拉通北缘岩石圈减薄的研究热点,但花岗岩的岩石年龄、成因及构造环境等方面的研究尚不够深入.以辽东凤城地区帽盔山二长花岗岩、蛟羊峪花岗闪长岩、清凉山二长花岗岩为研究对象,采用岩石学、岩石地球化学及LA-ICP-MS锆石U-Pb测年方法,讨论了花岗岩的岩石成因及构造意义.帽盔山二长花岗岩、蛟羊峪花岗闪长岩、清凉山二长花岗岩中锆石具有典型的岩浆振荡生长环带和较高的钍铀比(Th/U>0.4),LA-ICP-MS锆石U-Pb年龄分别为127.2±0.6 Ma、122.9±1.1 Ma、129.0±0.8 Ma,均形成于早白垩世.岩石地球化学特征显示帽盔山二长花岗岩和清凉山二长花岗岩为高钾钙碱性A型花岗岩,具有富Si、富碱,贫Al、Fe、Ca、Mg的特征,Eu负异常较为明显;蛟羊峪花岗闪长岩为准铝质到过铝质岩石,微量元素富集Nd、Tb、La,亏损Sr、P、Ti.构造环境判别结果显示,上述3个花岗岩体均形成于伸展拉张的构造环境.以上研究表明,辽东凤城地区在早白垩世时期处于非造山的伸展环境,是华北克拉通岩石圈减薄和克拉通破坏作用的缩影.
The magmatic rocks,which is widely distributed in Fengcheng area,Liaodong peninsula,is always a hot spot for study of North China Craton(NCC)thinning in recent years.However,due to lack of precise age and geochemical constraints in previous research,its petrogenesis and tectonic setting still remain controversial.In this paper,three granite plutons were studied by the petrology,petrogechemistry and LA-ICP-MS zircon U-Pb ages.The Maokuishan monzogranite,Jiaoyangyu granodiorite and Qingliangshan monzogranite were emplaced with the ages of 127.2±0.6 Ma,122.9±1.1 Ma and 129.0±0.8 Ma,respectively.These granites were all constrained to Early Cretaceous.The zircons of granites have the characteristics of oscillatory growth zonation and high ratios of Th and U(Th/U>0.4),indicating a magmatic origin for the zircons.Geochemical characteristics suggest that Maokuishan and Qingliangshan monzogranites are both metaluminum A-type and peraluminous high-K calc alkaline granites,and the major elements are characterized by high Si,alk and low Al,Fe,Ca and Mg.The chondrite-normalized REE patterns have a moderate negative Eu anomalies.Jiaoyangyu granodiorites are metaluminum-peraluminous granodiorites,and the trace elements are enriched in Nd,Tb,La,and depleted in Sr,P,Ti.Combined with geological background,the three granite plutons in Fengcheng area discussed above were all formed in anorogenic extensional tectonic setting during Early Cretaceous,and also is the epitome of the lithosphere thinning and cratonic destruction of the North China Craton.
作者
刘永俊
韩晓涛
刘正宏
吴文彬
王玉平
李海洋
王晓亮
Liu Yongjun;Han Xiaotao;Liu Zhenghong;Wu Wenbin;Wang Yuping;Li Haiyang;Wang Xiaoliang(Liaoning Research Institute of Geology and Mineral Resources,Shenyang 110032,China;College of Earth Sciences,Jilin University,Changchun 130061,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第1期145-155,共11页
Earth Science
基金
中国地质调查局地质矿产调查二级项目(No.DD20160049).
关键词
早白垩世花岗岩
锆石U-PB年龄
伸展环境
辽东凤城地区
地球化学
Early Cretaceous granites
zircon U-Pb ages
extensional tectonic environment
Fengcheng area of eastern Liaoning Province
geochemistry
