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

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。

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

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.