中亚造山带东南缘额仁淖尔地区早二叠世花岗岩锆石U-Pb年代学、源区特征及其意义  

Zircon U-Pb ages and isotope characteristics of Early Permian granitoids in Eren Nur area on the southeastern margin of Central Asian Orogenic Belt and their tectonic implications

作　　者：郭磊[1] 童英[1] 莫南[2] 王涛[1] 焦永艳 王文志[2] 赵辉[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学,北京100029

出　　处：《岩石矿物学杂志》2015年第5期601-619,共19页Acta Petrologica et Mineralogica

基　　金：国家重点基础研究发展计划(973计划)课题(2013CB429803);国家自然科学基金面上项目(41372006;41372077);中国地质调查局地质调查子项目(12120115069701;12120113094000)

摘　　要：位于中蒙边境额仁淖尔地区的查干德勒含角闪石黑云母二长花岗岩和卫境黑云母二长花岗岩锆石U-Pb年龄分别为276±2Ma和279±1Ma,均为早二叠世岩体。地球化学数据显示两个岩体均具有高SiO2含量(67.63%~74.75%)和高K2O含量(2.94%~6.13%),具弱的铕负异常(δEu=0.53~0.80),A/CNK均小于1.1,属弱过铝质的高钾钙碱性系列,具有I型花岗岩的特征。查干德勒岩体锆石εHf(t)值为-18.65^-10.95,模式年龄tDM2在2 470~1 989Ma之间,反映了深部源区可能存在古老地壳物质。卫境岩体锆石εHf(t)值为+1.71^+5.44,模式年龄tDM2在1 193~954Ma之间,具有年轻的源区特征,反映了年轻地壳的生长。额仁淖尔地区同时代两个花岗岩的锆石Hf同位素反映了完全不同的物源性质,也说明古老物质的再循环和新地壳的生长可以发生在同一个区域。Located in the Eren Nur area of China-Mongolia border region, the Qagan Dele amphibole- and biotite-bearing monzogranitic pluton and the Weijing biotite monzogranitic pluton have zircon U-Pb ages of 276±2 Ma and 279±1 Ma, respectively. They are both Early Permian plutons. Geochemical data show that these two granite bodies have high SIO2（67.63% --74.75% ）, K20 （2.94% --6.13% ） values and weak Eu negative anomalies with A/CNK ratios less than 1.1, thus belonging to weakly peraluminous high potassium calc-alkaline series and exhibiting I-type granitoids features. Qagan Dele granites have zircon εHf（ t ） values between - 18.65 to - 10.95 and older model ages （tDM2） in the range of 2 470-1 989 Ma, suggesting the probable existence of older crustral materials in the source. Weijing granites have zircon εHf（ t ） values between ＋ 1.71 and ＋ 5.44 and younger model ages （tDM2） in the range of 1 193-954 Ma, implying juvenile source at depth and crustal growth. Combined with regional tectonic evolution, it is held that these granitoids might have been formed in a syn-eollisional to post-collisional setting. The fact that the two different plutons in the same area have different zircon Hf isotopes indicates completely different sources, which implies that recycling of old crust and crustal growth could occured in the same region.

关 键 词：早二叠世 I型花岗岩 深部地壳信息 构造环境 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]