北淮阳早白垩世金刚台组火山岩LA-ICP-MS锆石U-Pb年龄及其地质意义

金刚台组火山岩是大别造山带北缘北淮阳晚中生代火山岩带的重要组成部分,选取金刚台组的粗面安山岩、熔结凝灰岩以及紧邻火山岩的正长斑岩,用LA-ICP-MS锆石U-Pb法进行了年龄测定,结果显示:两个火山岩样品的年龄分别为128.8±0.7 Ma和127.6±0.5 Ma,紧邻火山岩的正长斑岩的年龄为129.8±0.7 Ma,这3组年龄值在误差范围内近于一致,说明金刚台组火山岩和紧邻火山岩的正长斑岩是在很短的时间内形成的。这些年龄与整个苏鲁-大别造山带内早白垩岩世岩浆活动年龄的峰值区间一致,可能意味着它们形成于相同的动力学条件下。

LA-ICP-MS zircon U-Pb ages of Early Cretaceous volcanic rocks from Jingangtai Formation in Beihuaiyang belt on the northern margin of the Dabie Orogen and their geological implications

The Jingangtai Formation constitutes an important component part of the Beihuaiyang Late Mesozoic volcanic rock belt.In this paper,the zircon U-Pb age of an ignimbrite sample was determined,and a trachyandesite sample from the Jingangtai Formation and an orthophyre sample collected near the volcanic rocks were dated by LA-ICP-MS method.According to the results,the ages of the 3 sample are almost identical within the error range,which means that the volcanic rocks of Jingangtai Formation and the orthophyre were formed in a very short period.Meanwhile,these ages are very close to the concentrated ages of the Cretaceous magmation in Sulu-Dabie orogen,which implies that they might have been generated under the same dynamic condition.