新疆阿尔泰友谊峰地区木孜他乌岩体锆石U-Pb年龄及地质意义

摘要

Large quantities of granites are developed in the southern margin of Altay orogenic belt.The previous studies have focused on the formation age and structural setting of the granites from the eastern section of Altay orogenic belt,but the research its western section is still limited.Muzitawu Plutons are located in Muzitawu area of Western Friendship Peak,Burqin County,Altay,Xinjiang,which are mainly consist of biotite granite,porphyritic biotitesyenogranite and muscovite syenogranite.In these plutons,the pegmatite veins are very developed,with rare metal mineralization.The LA-ICP-MS zircon U-Pb method was used to study the chronology of porphyritic biotitesyenogranite,and the zircon 206Pb/238U weighted average age of the plutons is (198.3±3.8) Ma (MSWD=2.0),indicating that these plutons were formed in early Jurassic.This age is basically in line with the metallogenic epoch of pegmatite vein-type rare metals in the eastern section of Altay orogenic belt,which provides a chronological restriction for the study on the mineralization epoch of rare metal-muscovite-gemstone relating to pegmatite in this area.%新疆阿尔泰造山带南缘发育有大量的花岗岩,前人对阿尔泰造山带东段花岗岩的形成时代和构造环境等方面进行了大量的研究,而对西段研究较为局限.木孜他鸟岩体位于新疆阿勒泰布尔津县境内友谊峰西木孜他乌一带,主要由黑云母花岗岩、斑状黑云母正长花岗岩、白云母正长花岗岩组成.岩体内花岗伟晶岩脉发育,并具有稀有金属矿化显示.运用LA-ICP-MS锆石U-Pb方法对木孜他乌岩体进行年代学研究,获得斑状黑云母正长花岗岩锆石206 pb/238 U加权平均年龄为(198.3±3.8)Ma(MSWD=2.0),表明该岩体形成于早侏罗世,与阿尔泰造山带东段伟晶岩脉型稀有金属成矿时代基本一致,为研究本区伟晶岩型稀有金属-白云母-宝石等成矿作用时代提供了年代学约束.