内蒙古巴林右旗东梁岩体LA-ICP-MS锆石U-Pb定年及地球化学特征

LA-ICP-MS zircon U-Pb age of Dongliang pluton in Balinyouqi,Inner Mongolia and its geochemical characteristics

本文对内蒙古巴林右旗东梁岩体进行的岩石学、年代学和地球化学研究显示,东梁岩体岩性为石英闪长岩,LA-ICP-MS锆石U-Pb定年加权平均年龄为（251.9±4.4）Ma,指示东梁岩体形成于早三叠世。地球化学特征表明岩石富硅、铝、钠,贫镁、钾,A/CNK=0.98~1.11,属于钙碱性准铝质-弱过铝质岩石,轻稀土富集,重稀土亏损,不具Eu和Ce异常,具有高Sr、低Y、低Yb的特征,属于埃达克岩。结合区域已有研究成果,认为东梁岩体的岩浆可能来源于西伯利亚板块和华北板块碰撞拼合所导致的新生地壳部分熔融。

The study of the petrologic,chronological and geochemical characteristics of Dongliang pluton in Balinyouqi,Inner Mongolia shows that the lithology of Dongliang pluton is of quartz diorite,while the LA-ICP-MS zircon U-Pb dating shows the weighted average age as（ 251. 9 ± 4. 4） Ma,representing the Dongliang pluton formed in the Early Triassic. The geochemical characteristics indicate that the rocks are enriched in Si,Al,Na,and depleted in Mg,K. The A / CNK is 0. 98 ~ 1. 11,showing the pluton is of calc-alkalic metaluminous-weakly peraluminous rocks. The quartz diorite is rich in LREE,depleted in HREE and without Eu,Ce anomaly,which shows the characteristics of high Sr,low Y and Yb,belonging to adakite rocks. Combined with previous researches,the authors believe that the magma of Dongliang pluton may be originated from the partial melting of juvenile crust caused by the collision and suturing of Siberian Plate and North China Plate.