北大别岳西岩体和飞旗寨岩体的LA-ICPMS锆石U-Pb定年及其地质意义  

LA-ICPMS zircon U-Pb dating of the Yuexi and Feiqizhai plutons in the north Dabie region and its geological significance

作　　者：刘晓强[1] 闫峻[1] 王爱国[2] 李全忠[1] 姚洪忠 

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009 [2]中国地质调查局南京地质矿产研究所,江苏南京210016

出　　处：《地球化学》2015年第2期155-166,共12页Geochimica

基　　金：国家自然科学基金(41272074);中国地质调查局基础地质项目(12120 11220546)

摘　　要：大别造山带发育大量早白垩世侵入体, 前人对北大别岳西岩体和飞旗寨岩体的形成时代的认识存在差异.选取岳西岩体和飞旗寨岩体为研究对象, 对其进行全岩主元素分析和LA-ICPMS 锆石U-Pb 定年.锆石的高Th/U 比值特征及典型岩浆锆石环带显示其为岩浆成因.岳西岩体的26 个测点的加权平均年龄为（128.5±1.4） Ma, 飞旗寨岩体的15 个测点的加权平均年龄为（127.4±1.7） Ma, 说明岳西岩体和飞旗寨岩体均形成于早白垩世.结合目前大别造山带高精度火成岩年代学数据, 大别造山带腹地侵入岩可以划分为早晚两期, 分别为143-130 Ma 和130-119 Ma.早期火成岩具有高钾钙碱性和埃达克质地球化学属性, 而晚期火成岩具有向碱性岩过渡的性质, 在120 Ma 左右出现少量A 型花岗岩, 暗示130 Ma 为本地区深部过程转换的重要时期.Early Cretaceous intrusive plutons are distributed extensively in the Dabie orogen. How to identify theformation ages for the Feiqizhai and Yuexi plutons remains a topic of controversy. We choose the Yuexi andFeiqizhai plutons as the study object, and carried out LA-ICPMS zircon U-Pb dating. The high Th/U ratios andtypical magmatic oscillatory zoning of zircons indicate their magmatic origin. The 206Pb/238U weighted averageage of 26 analyses for the Yuexi pluton is （128.5±1.4） Ma, the 206Pb/238U weighted average age of 15 analyses forthe Feiqizhai pluton is （127.4±1.7） Ma. These results indicate that both Yuexi and Feiqizhai plutons are formed inearly Cretaceous. Based on high precision geochronology data of magmatic rocks in the Dabie orogen, theintrusive rocks can be categorized into two stages： the early stage （143-130 Ma） rocks exhibit the characteristicsof high-K calc-alkaline series and show adakitic affinity, whereas the late stage （130-119 Ma） rocks show thecharacteristics of alkaline rocks with occurrence of small amount of A-type granite at ~120 Ma. This may suggestthat 130 Ma is an important period for deep process transformation in the Dabie orogen.

关 键 词：火成岩 锆石定年 白垩纪 大别造山带 岳西岩体 飞旗寨岩体 

分 类 号：P59[天文地球—地球化学] P597.3[天文地球—地质学]