The Targen monzogranite was sheared by the Tuoli fault in the middle of west Junggar and the maximum intial 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 dearly indicated that the initiation of left-lateral slip of the Tuoli fault took place after 295 Ma.%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同住素测定,共测得29个颗粒的31个数据.这31个数据中,<'206>Pb/<'238>U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<'206>Pb/<'238>U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.
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