新疆伊吾县北晚石炭世侵入岩地球化学特征、锆石U-Pb年龄及其后碰撞构造环境的确定

Geochemistry,ziron U-Pb ages of Late Carboniferous intrusive rocks in the north of Yiwu County,Xinjiang and determination of past-collision tectonic environment

新疆伊吾县北晚石炭世侵入岩产于哈尔里克复合岛弧带。用SHRIMP技术测得伊吾县北花岗闪长岩和钾长花岗岩的锆石U-Pb年龄分别为(299±3)Ma(MSWD=0.48)和(301±4)Ma(MSWD=0.54),属晚石炭世。岩石化学特征表明,伊吾县北晚石炭世侵入岩为弱过铝质高钾钙碱性岩系,轻稀土元素富集,重稀土元素平坦,具中等程度的负Eu异常。微量元素中富集轻稀土元素及Ba、Th等大离子亲石元素,而相对亏损Nb、Ti、P元素,P元素较强亏损可能与磷灰石分离结晶作用有关,元素地球化学组成指示其与大陆地壳物质具有明显的亲缘性;以上资料揭示,伊吾县北晚石炭世已经处于后碰撞构造环境。

The Late Carboniferous intrusive rocks in the north of Yiwu County,Xinjiang are located in the harlik composite island arc zone.The U-Pb ages of zircons from the northern Yiwu granodiorite and kali-syenite were(299±3)Ma(MSWD=0.48)and(301±4)Ma(MSWD=0.54),respectively,measured by LA-ICP-MS,which belong to the late carboniferous.Petrochemistry shows that the Late Carboniferous intrusive rocks in the north of Yigu are weakly peraluminiferous and high potassium calc-alkaline rocks,with light rare earth elements enriched,heavy rare earth elements flat,with a moderate degree of negative Eu anomaly.Light rare earth elements and large ionic lithophile elements such as Ba and Th are enriched in trace elements,while relative losses of Nb,Ti and P may be related to the separation and crystallization of apatite.The above data reveal that the Late Carboniferous in the north of Yiwu was already in a post-collision tectonic environment.