西天山昭苏阿登套地区大哈拉军山组火山岩LA-ICP-MS锆石U-Pb年龄及其意义

摘要

西天山昭苏阿登套山地区广泛出露大哈拉军山组火山-沉积体系,形成时代分歧很大.阿登套山大哈拉军山组火山岩主要由玄武岩、安山岩、英安岩、流纹岩及其一系列紫色、灰色、紫红色火山碎屑岩组成,笔者选取流纹质火山角砾岩进行LA-ICP-MS锆石U-Pb定年,结果表明锆石年龄为(344.4±6.1)Ma,结合锆石的矿物学特征CL图像特点及其地质资料,初步得到结论:阿登套山地区大哈拉军山组形成时代不晚于早石炭世,这不仅准确约束了该区大哈拉军山组火山地层的形成时代,也为研究西天山岩浆作用及构造演化提供了新的年代学证据.%Dahalajunshan Formation volcanic-sedimentary rocks are widespread in Adengtao area of Zhaosu County,West Tianshan,and there is great disparity in its age identification.The volcanic rocks in the Dahalajunshan Formation of Adengtao area are composed of basalt,andesite,dacite,rhyolite and series of relevantpurple,grey,mauve volcaniclastic rocks.Zircon LA-ICP-MS dating has been used to determine the formation ageofrhyolitic volcanic breccia.The results showthat the age of zircon was (344.4±-6.1) Ma.Combining with the CL image features of zircons as well as the geological data,the following conclusionshave been reached:the Dahalajunshan Formation was formed not later than early Carboniferous in Adengtao area,West Tianshan.The findings has accurately constrained the period of volcanic strata inthis area,which provides new chronological evidence for volcanic magmatism and tectonic evolution of West Tianshan.