There is a great thickness of bathyal- and slope-facies volcanic-volcaniclastic sedimentary sequence at Baogutu area in southeast of western Junggar, which are named as Tailegula Formation, Baogutu Formation and Xibeikulas Formation, respectively. There have been controversies about the geological ages and stratigraphic subdivision about these strata for a long time. So we surveyed the stratum section at Baogutu area and separated zircons from basalt of the Tailegula Formation and tuff of Baogutu Formation and Xibeikulas Formation. LA-ICP-MS U-Pb dating on these zircon grains gives the 206Pb/238 U weighted mean ages of 357. 5 ± 5. 4Ma, 332. 1 ± 3. 0Ma and 336.3 ± 2. 5Ma, respectively, indicating that the strata sequence from bottom to top should be Tailegula Formation, Baogutu Formation and Xibeikulas Formation in turn, which were formed from Tournaisian to Visean of Early Carboniferous.
西准噶尔包古图铜矿是近几年新疆发现的又一个中型斑岩铜矿,其成岩成矿年代学的研究可以对矿床成因、区域成矿规律的认识有更好的制约.包古图地区出露一系列中酸性小岩体,前人按照出露面积大小将这些岩体编号为Ⅰ～Ⅹ号.目前,Ⅴ号岩体已经进行了详勘,探明为中型铜矿,其他几个岩体也都程度不同的投入了勘探工作量,并且发现了较好的成矿迹象.本文利用锆石SHRIMP U-Pb法和单矿物K-Ar法对Ⅴ号岩体进行了成岩成矿年代学研究,其中锆石25个测点的206Pb/238U SHRIMP 年龄大致可以分为加权平均值(335.6±7.8)Ma和(311.4±3.3)Ma的两组,前者被解释为捕获锆石,可能来源于包古图组凝灰岩或者深部的花岗质岩基,有待于进一步研究;后者为含矿岩体侵位年龄.本次研究获得成矿期黑云母的K.Ar年龄为(296.0±3.7)Ma和(297.3±3.8)Ma,结合我们以前所获得的辉钼矿Re-Os年龄310 Ma,确定成矿时代为310～296 Ma.花岗斑岩和闪长玢岩脉的K-Ar年龄为278～240 Ma,根据穿插关系可以判定它们为成矿后脉岩.据此基本建立了包古图斑岩铜矿成岩成矿年代学框架.
伊吾县铜华岭中酸性侵入体位于新疆北部东准噶尔阿尔曼太断裂和克拉麦里断裂之间的野马泉岛弧区,岩性主要为闪长玢岩、英云闪长岩和二长花岗岩等.通过锆石LA-ICP-MS U-Pb年代学方法,对这3种岩性进行精确定年,其206Pb/238U的加权平均年龄分别为427.4±3.2,422.8±3.2和418.5±2.6 Ma,说明铜华岭岩体是早古生代岩浆活动的产物,为东准噶尔早古生代造山带演化提供了花岗岩证据.
