中祁连西段巴嘎德尔基岩体LA-ICP-MS锆石U-Pb年龄及地质意义

摘要

The Bagadeerji granitic plutons mainly made up of moyite and adamellite occur in the Yemananshan area, central Qilian Mountains, Gansu. The LA-ICP-MS zircon U-Pb age dating gives an emplacement age of 462. 5 ± 1.4 Ma for the Bagadeerji granitic plutons. Geochemically, the Bagadeerji plutons are characterized by strong peraluminous granites, high K and K/Na ratios, low Mg, Fe and Ca contents, enriched K, Rb, Ba and Th elements, depleted Zr, Hf, Y and Yb elements, and slight Eu negative anomaly. The trace element discrimination plots indicate that these intrusions have a " syn-collision" affinity as defined by Pearce et al. (1984) , and thus may be interpreted to be the continent-continent collisional products formed during the late Caledonian orogeny.%巴嘎德尔基岩体位于中祁连山西段的野马南山地区,主要由钾长花岗岩和二长花岗岩组成.LA-ICP-MS锆石U-Pb测年表明,巴嘎德尔基岩体侵位年龄为462.9±1.4Ma.该岩体地球化学方面表现出强过铝、高K、K/Na,低Mg、Fe、Ca的主量元素特征,并富集K、Rb、Ba、Th,亏损Zr、Hf、Y、Yb等微量元素,轻稀土富集,弱的Eu负异常.在微量元素判别图解上,所有岩石投影点均落入同碰撞区域.结合区域地质背景,认为巴嘎德尔基岩体是加里东造山作用晚期陆陆碰撞的产物.