大兴安岭中段东南部糜棱岩化花岗岩的Rb─Sr年龄

Rb─Sr Isotopic Dating of Mylonitize Granite in Southeast Mid-Da Hinggan Mountains

东北大兴安岭东南处扎兰屯地区东南部分布着糜棱岩化花岗岩,1∶20万地质图依据其产状及岩石特征将此类变形花岗质岩石划分为混合变质岩系,视为额尔古纳-兴安地块早元古代形成的结晶基底。该区糜棱岩化花岗岩带位于大兴安岭与松辽盆地的过渡带上,呈小面积不连续带状出露。研究表明,该区牦牛沟岩体眼球状糜棱岩化花岗岩的钾长石-全岩Rb─Sr等时线年龄为(173±3.45)Ma,锶初始值为0.733 0±0.000 61,明显高于区域中侏罗世花岗岩的锶初始值(0.705~0.710),糜棱岩化花岗岩的原始结晶年龄可能为古生代。根据野外地质观察和定向标本显微观测,牦牛沟北东向韧性构造变形带具左行走滑性质,该期左行走滑变形时代的确定对大兴安岭地区中生代区域构造演化具有重要意义。

There are mylonitize granite distributing in southeast Mid-Da Hinggan Mountains of Zhalantun area.In 1∶200 000 geologic map,they were considered to be mixed metamorphic rocks judging by the appearance,metamorphic protholith formation and the occurrence,and as the crystalline basement of Erguna-Hinggan terrane formed in early Proterozoic.With the advent of geochronology research upsurge in Da Hinggan Mountains,the mylonitize granite has gone into the table.The Maoniugou pluton located in the transition of so...