辽北地区中生代石英闪长岩的形成时代

Formation Age of Mesozoic Quartz-Diorite in Northern Liaoning

辽北地区位于华北陆块和华北北缘古生代坳陷带2个Ⅱ级大地构造单元上,后期构造岩浆作用强烈,尤以侏罗纪岩浆活动最为强烈,广泛发育不同类型的花岗岩。关于研究区内中生代石英闪长岩的形成时代,一直缺乏深入的年代学研究。笔者在区内进行1∶5万区域地质调查中,对石英闪长岩采样并作LA-ICP-MS测年,获得锆石U-Pb年龄为(173±0.88)Ma(MSWD=5.8),在一定误差范围内,综合所测锆石的CL图像特征,准确约束了区内中生代石英闪长岩的形成时代。结合前人资料将区内中生代石英闪长岩的形成时代确定为中侏罗世。这一成果为研究辽北地区岩浆作用及其构造演化提供了新的年代学证据。

The northern Liaoning is located in two secondary tectonic units of North China Craton and Paleozoic depression zone in northern margin of North China,with strong late tectonic magmatic activities,especially Jurassic magmatic activity is most intense,when different types of granites were widely developed.However,the formation times of the Mesozoic tonalite in this area is lack of depth research.When carrying out the 1∶50 000 regional geological survey,the quartz diorite samples have been collected to carry out the LA-ICP-MS dating.The obtained UPb ages of zircons are（173＋0.88）Ma（MSWD=5.8）,which is in a certain error range.Based on the CL images of these zircons,the formation age of Mesozoic quartz diorite in this area has been restrained precisely.According to the previous results,the formation age of this quartz diorite has been defined as Middle Jurassic.This achievement provides a new chronology evidence for studying the magmatism and tectonic evolution of northern Liaoning.