西准噶尔托里地区塔尔根二长花岗岩锆石U-Pb年龄——托里断裂左行走滑运动开始的时间约束  

Zircon SHRIMP U-Pb age of Targen monzogranite in western Junggar,Xinjiang,China: Initial time of left-lateral slip of the Tuoli fault

作　　者：宋彪[1,2] 李锦轶[1] 张进[1] 朱志新 王煜[4] 徐新[4] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]北京离子探针中心,北京100037 [3]新疆地质调查研究院,新疆乌鲁木齐830011 [4]新疆自然资源与生态环境研究中心,新疆乌鲁木齐830000

出　　处：《地质通报》2011年第1期19-25,共7页Geological Bulletin of China

基　　金：国家973项目(编号:2007CB411306);中国地质调查局国土资源调查项目(编号:1212010711817;1212010611806)

摘　　要：西准噶尔中部的托里断裂切错了塔尔根岩体,如果确定了该岩体的时代,就可以限定托里断裂左行走滑运动开始的最大时限。所研究的样品为浅肉红色二长花岗岩,采样位置位于托里县城以南、托里断裂南东,距离该断裂面约50m。用SHRIMP对岩石中的锆石进行了U-Th-Pb同位素测定,共测得29个颗粒的31个数据。这31个数据中,206Pb/238U年龄最小值为279.5Ma±2.7Ma,最大值为337.3Ma±2.7Ma,相差达58Ma,差异大于17%。Th/U比为0.31~0.88,U含量为65×10-6~384×10-6,Th含量为23×10-6~142×10-6。根据CL图像,将其中13个点的206Pb/238U年龄进行加权平均计算,将加权平均值295.8Ma±2.5Ma作为岩体的侵位年龄。塔尔根岩体被托里断裂左行错开这一地质现象,以及该岩体的锆石定年结果,清楚地表明托里断裂的左行走滑运动一定是发生在295Ma以后,即其左行走滑运动不是发生在石炭纪期间。The Targen monzogranite was sheared by the Tuoli fault in the middle of west Junggar and the maximum initial time of left-lateral slip of the Tuoli fault will be limited by the emplacement time of the monzogranite.The sample,light fleshred monzogranite,was collected at N45°45.911′,E83°32.584′,located at the south of the Tuoli City,50 meter southeast to the fault plane.The U-Th-Pb isotope data of 29 grains,i.e.31 spots,of zircons in the sample were obtained by using the SHRIMP Ⅱ in Beijing SHRIMP Center.In all of the data,the 206Pb/238U ages of the zircons are between（279.5±2.7）Ma^（337.3±2.7）Ma,with the Th/U ratios of 0.31~0.88,U contents of 65×10-6~384×10-6 and Th contents of 23×10-6~142×10-6.According to the observation of the very similar CL images of the zircons,the weighted average value of 206Pb/238U age of（295.8±2.5） Ma was obtained by the calculation using 13 among the 31 data,which is interpreted as the emplacement time of the Targen monzogranite.Based on the fact of left-lateral slip sheared and the emplacement time of the Targen monzogranite,it is clearly indicated that the initiation of left-lateral slip of the Tuoli fault took place after 295 Ma.

关 键 词：西准噶尔 塔尔根二长花岗岩 托里断裂 左行走滑 锆石SHRIMPU-PB年龄 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]