摘要
对内蒙古大兴安岭中段阿尔山金江沟花岗岩体岩相学研究表明,该花岗质岩体主要岩性组合为正长花岗岩和黑云母二长花岗岩。应用锆石U-Pb LA-ICP-MS测年方法。测定2组年龄,正长花岗岩锆石年龄为311.6±2.5 Ma,黑云母二长花岗岩锆石U-Pb年龄为312.0±1.1 Ma。地球化学特征显示金江沟花岗岩为弱过铝质高钾钙碱性-钾玄质高分异I型花岗岩,具有高硅、高碱和低CaO、Fe_2O_3、MgO和P_2O_5的特征,轻稀土元素(LREE)富集,重稀土元素(HREE)相对亏损,具有明显的负铕异常;微量元素原始地幔标准化蛛网图中高场强元素Zr,Hf和大离子亲石元素Rb、Th相对富集,而Ba、Nb、Ti、Sr,和P具明显的亏损。结合地球化学资料与区域地质研究成果,区内花岗岩应形成于局部拉张的构造背景,其可能与兴安地块和松嫩地块之间的古亚洲洋的俯冲作用有重要关系。
The Jinjianggou granite is located in the middle part of Daxing＇ anling and mainly composed of syenogranite and biotite monzonitic granite in lithology. The LA-ICP-MS U-Pb dating results reveal that the syenogranite emplaced in 311. 6 ± 2. 5 Ma and the biotite monzonitic granite emplaced in 312. 0 ± 1. 1 Ma. The geochemical data indicate that the Jingjianggou granite is featured by weakly peraluminous,high content of Si O2 and alkaline,low contents of Ca O,Mg O,Fe_2O_3 and P_2O_5,enrichment of LREE with Zr,Hf,Rb,Th,depletion of HREE with Ba,Nb,Ti,Sr and P,and negative Eu anomalies. These characteristics suggest that the Jinjianggou granite is highly differential potassium calc-alkali I-type. The Jinjianggou granites probably emplaced in regional extensional background and related to the subduction of Paleo Asian Ocean between Xing＇ an and Songneng plates.
出处
《世界地质》
CAS
2016年第1期89-99,共11页
World Geology
基金
中国地质调查局项目(1212011120674
1212011220420)资助
