伊尔施花岗岩位于大兴安岭中段，出露面积约260km2，由中细粒二长花岗岩、中粗粒斑状正长花岗岩和中粗粒正长花岗岩三期侵入体构成。岩体侵入于石炭-二叠系地层，被晚侏罗世火山岩不整合所覆。锆石LA-ICP-MS U-Pb年龄为（226．3±1．4） Ma ，表明为晚三叠世花岗岩。花岗岩具有高硅、富碱、低钙的特征，属于弱过铝质岩石。稀土元素总量较高，轻稀土相对富集，重稀土相对亏损，Eu负异常明显。强不相容元素富集，亏损Ba、S r、P和T i。总体属于高钾钙碱性系列向碱性系列过渡的花岗岩，具有后造山花岗岩类（POG ）的特征，形成于挤压造山向拉张体制转变阶段的构造环境，暗示该区受西伯利亚板块和华北板块碰撞造山作用的影响持续到三叠纪。%Yi’ershi granite located in the middle of Daxing ’anling area ,about 260 km2 .It consists of three phase intrusions , the middle-fine grained adamellite ,coarse-grained grained porphyritic orthoclase granite and coarse-grained orthoclase granite ,respectively .Pluton intruded into the Carboniferous-Permian strata ,and the Late Jurassic volcanic rocks are unconformably overlying them .Zircon LA-ICP-MS U-Pb dating ages of the pluton is (226 .3 ± 1 .4) Ma ,indicates that the Late Triassic granite .The granitoid has the characteristics of high silica ,alkali-rich ,low calcium ,belongs to the weakly peraluminous rocks .Total REE abundance is variable ,rich of HREE ,and the fractionation of LREE is more than that of HREE relatively ,and by obivious Eu anomalies .Strong incompatible elements are enrichment ,lack of Ba ,Sr ,P and Ti .Overall belong to the transition series from high-K series to calc-alkaline series granite ,shows the characteristics of typical post-orogenic granite (POG ) .It mainly formed in the transition phase from the extrusion orogenic to extensional regime tectonic environment , which suggesting the collision orogeny between Siberian Plate and North China Plate affected by continued to Triassic in the region .
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