新疆东准噶尔老鸦泉岩体的锆石U-Pb年龄和地球化学组成

Zircon U-Pb Ages and Geochemical Characteristics of the Laoyaquan A-type Granites in East Junggar,North Xinjiang,China

老鸦泉岩体是贝勒库都克锡矿带内最大的花岗岩体,它主要由黑云母钾长花岗岩组成。通过对2件样品的锆石LA-ICP-MS U-Pb同位素年龄测定,获得其206Pb/238U年龄值分别为301±2 Ma和300±5 Ma,指示该岩体侵位时代为晚石炭世。岩石地球化学组成表明,老鸦泉碱长花岗岩具有富硅、富碱,相对富集Rb、K、Th、U、Nd、Hf等元素,而贫Ba、Sr、P、Ti等元素,具强负Eu异常,总体显示A型花岗岩的地球化学特征。锆石U-Pb年龄及岩石地球化学特征都表明老鸦泉岩体的形成与晚石炭世北疆强烈的后碰撞岩浆活动有着密切关系。

Laoyaquan granitic pluton is the largest pluton containing tin deposit in the Beilekuduk tin metallogenic belt.It is mainly composed of biotite alkali-feldspar granites.LA-ICP-MS U-Pb dating for zircons from two samples yielded the 206Pb/238U ages of 301±2 Ma（2σ,MSWD=1.03） and 300±5 Ma（2σ,MSWD=5.90）,suggesting that the emplacement of the pluton occurred at the end of Late Carboniferous.The Laoyaquan alkali-feldspar granite is enriched in silica,alkalis,REE,Rb,K,Th,U,Nd,Hf and depleted in Ba,Sr,P,and Ti,with a strong Eu negative anomaly,showing the features of A-type granites.Both the geochemical characteristics and the zircon U-Pb ages indicate that the formation of the pluton is related to the post-collision and the magmatic activity during Late Carboniferous in northern Xinjiang.