阿尔泰造山带伟晶岩年代学及其地质意义

LA-ICPMS U-Pb Zircon Geochronology of the Altai Pegmatites and Its Geological Significance

利用LA-ICPMS技术对阿尔泰造山带19条伟晶岩脉中锆石进行U-Pb年代学研究,结果显示,阿尔泰伟晶岩可划分为4个主要形成时期:加里东期,形成年龄约476 Ma;海西晚期,形成年龄约260～280 Ma;印支期,形成年龄主要分布在205～250Ma;燕山期,形成年龄主要分布在180～200 Ma范围。其中以二叠纪、三叠纪-侏罗纪为主,形成于构造体制由挤压转换为伸展的背景。另外,阿尔泰地区分布有大量稀有金属伟晶岩,综合前人和本文研究结果,认为这些稀有金属伟晶岩主要形成于印支期。

In this paper, we report new LA-ICPMS U-Pb zircon ages for 19 pegmatite veins in the Altai area, NW China. According to zircon ages, the pegrnatite can be divided into four periods ： （ 1 ） Caledonian Period, about 476 Ma; （2） late Hercynian period, 260-280 Ma; （3） lrtdosinian Period, 205-250 Ma; （4） Yanshan Period, 180 -200 Ma. Our resuhs suggest that the Altai pegmatites were mainly formed in Permian and Trias-Jurassie. And In- dosinian is an important rare-metal mineralization epoch in the Altay area. After early Permian （ 〈 280 Ma）, the re- gional tectonic regime changed from compressional to extensional Pegrnatite formation is controlled by the extensional regime.