东天山镜儿泉伟晶岩与花岗岩成因关系:来自锆石U-Pb定年和Hf同位素证据  

Genetic linkage between pegmatites and granites from Jingerquan,East Tianshan Mountains:Evidence from zircon U-Pb geochronological and Hf isotopic data

作　　者：李寄邦 张辉[1] 吕正航[1] LI Ji-bang;ZHANG Hui;LÜZheng-hang(Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地球化学研究所地球内部物质高温高压重点实验室,贵州贵阳550081 [2]中国科学院大学,北京100049

出　　处：《地球化学》2020年第4期385-403,共19页Geochimica

基　　金：国家自然科学基金(91962222、41372104);新疆有色金属工业(集团)有限责任公司科研项目(2011YSKY-02)。

摘　　要：对东天山镜儿泉矿区花岗岩岩石地球化学以及花岗岩和伟晶岩锆石U-Pb定年、锆石Hf同位素组成特征进行了研究,以便确定它们的形成时代、构造背景及伟晶岩与花岗岩的成因关系。研究结果显示,镜儿泉矿区花岗岩属于高分异的过铝质花岗岩,其中黑云母花岗岩、二云母花岗岩和白云母花岗岩形成时代分别为(223.6±1.5)Ma、(223.2±1.3)Ma和(220.2±1.4)Ma,锆石εHf(t)值分别变化于+10.7^+11.8、+6.2^+12.6和+6.2^+10.7范围;镜儿泉伟晶岩I号脉形成年龄为(218.0±1.8)Ma,锆石中εHf(t)值分布于+10.6^+12.3范围。伟晶岩与花岗岩均具有相似的形成时代、同位素组成以及相对年轻的模式年龄(tDM2=453~864 Ma),表明镜儿泉伟晶岩与花岗岩有成因上的联系。因此,镜儿泉伟晶岩成因应是后碰撞造山背景下不成熟新生地壳部分熔融形成的花岗质岩浆高度分异演化的产物。In this study,the characteristics of petrogeochemistry,zircon U-Pb dating,and zircon Hf isotopic composition of pegmatites and granites in the Jingerquan mining area in the East Tianshan Mountains were assessed to determine the formation age,tectonic setting,and genetic relationship between the pegmatites and granites.The results show that the granites in the Jingerquan mining area are highly fractionated peraluminous granite.The intrusion ages of the biotite,two-mica,and muscovite granites are(223.6±1.5)Ma,(223.2±1.3)Ma,and(220.2±1.4)Ma with zirconεHf(t)values varying in a range of+10.7–+11.8,+6.2–+12.6,and+6.2–+10.7,respectively.The formation age of the No.1 pegmatite is(218.0±1.8)Ma with zirconεHf(t)values in the range of+10.6–+12.3.In addition,the pegmatite and granites have relatively young modal age characteristics(tDM2=453–864 Ma)indicating that they have a genetic relationship.Therefore,this study suggests that the Jingerquan pegmatites were generated via a high fractionation process of granitic magma from the partial melting of immature juvenile crust during the post-collisional stage.

关 键 词：岩石成因论 锆石U-PB定年 HF同位素 伟晶岩 花岗岩 

分 类 号：P597[天文地球—地球化学] P588.121[天文地球—地质学]