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

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.

LA-ICP-MS zircon U-Pb ages and geological implications for the Bagadeerji granitic plutons in the central Qilian Mountains, Gansu

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.