江西武功山中生代花岗岩的锆石U-Pb年龄、Hf同位素特征及其地质意义  

Zircon U-Pb ages, Hf isotopic characteristics, and geological significance of the Mesozoic granites in Wugong Mountains area, Jiangxi

作　　者：张垚垚 刘凯 何庆成 郝美英[1] 郭朝斌 白俊杰 余廷溪 ZHANG Yaoyao;LIU Kai;HE Qingcheng;HAO Meiying;GUO Chaobin;BAI Junjie;YU Tingxi(Chinese Academy of Geological Sciences,Beijing,100037;China University of Geosciences(Beijing),Beijing,100083;China University of Mining and Technology(Beijing),Beijing,100083)

机构地区：[1]中国地质科学院,北京100037 [2]中国地质大学(北京),北京100083 [3]中国矿业大学(北京),北京100083

出　　处：《地质论评》2022年第4期1301-1319,共19页Geological Review

基　　金：中国地质调查项目(编号:DD20221677-2、DD20201165);中央财政基本科研业务费资助项目(编号:JKY202004、JKY202011)的成果。

摘　　要：江西省武功山地区主要发育早古生代和中生代两期花岗岩,后者主要为二云二长花岗岩和黑云母二长花岗岩等,分布于三江村、明月山及和平村等地区,为了研究其形成时代、岩石成因、源区特征和构造环境,分别选取三江地区和和平地区的细中粒斑状黑云母二长花岗岩及细粒斑状二云二长花岗岩进行岩石学、矿物学、地球化学、锆石U-Pb同位素测年和锆石Lu—Hf同位素研究。花岗岩SiO_(2)含量为72.96%~74.16%,Na_(2)O+K_(2)O含量为6.68%~8.42%,MgO含量为0.29%~0.70%,铝饱和指数A/CNK为1.11~1.36,为强过铝质高钾钙碱性花岗岩。ΣREE较低,稀土配分曲线呈右倾型,具强烈δEu负异常,为S型花岗岩。花岗岩锆石n(206 Pb)/n(238U)年龄加权平均值为152.41±0.89 Ma和149.31±0.71 Ma,为晚侏罗世岩浆活动的产物。花岗岩f_(Lu/Hf)值均小于-0.9,ε_(Hf)(t)均为负值,岩浆来源于演化的元古宙陆壳物质。地质演化背景结合样品构造判别图解,综合分析认为武功山中生代花岗岩形成于陆内俯冲环境。Objectives:This paper provided petrography,geochemical characteristics,LA-ICP-MA zircon U-Pb age,and zircon Lu-Hf isotopes of the Mesozoic granite in the Wugong Mountains area,Jiangxi,south China.The formation age,genesis,and tectonic significance of granites are discussed.Methods:Based on the field work,through the microscopic observation,the whole rock chemical analysis,the LA-ICP-MS zircon U-Pb isotopic chronology,and the LA-ICP-MS zircon Lu-Hf isotopes of granites.Results:The zircons of the Mesozoic granite in Wugong Mountains area were mostly long columns and developed oscillatory belts,showing the characteristics of magmatic origin.Zircon LA-ICP-MS U-Pb isotopic chronology shows that the Mesozoic granites in the Wugong Mountains area were formed at 149.31~152.41 Ma.The rocks are riched in silicon(SiO_(2)=72.96%~74.16%),alkali(Na_(2)O+K_(2)O=6.68%~8.42%),and poor in calcium(CaO=0.55%~1.82%),magnesium(MgO=0.29%~0.70%).Aluminum saturation index(A/CNK=1.11~1.36).It is enriched in large ion lithophile elements such as Rb,U,Th and K,and relatively depleted in high field strength elements such as Sr and Ti.The ratio of light and heavy rare earth elements(La/Yb)_(N)=10.79~25.43,with a high degree of differentiation and moderate-weak negative Eu anomaly(δEu=0.17~0.28).The rare earth distribution curves are right-leaning,indicating the characteristics of S-type granite.Zircon f_(Lu/Hf) values of the Wugong Mesozoic granite are all less than-0.9,andε_(Hf)(t)are all negative.Conclusions:Collectively,it is suggested that the granite belongs to strong peraluminous high-potassium calc-alkaline granite.It is S-type granite.The wugong granite was formed in Mesozoic,and the test results are relatively concentrated.The zircon Lu-Hf isotopic characteristics indicate that the magma source area is Neoproterozoic continental crust material.The Wugong granite was formed in an intracontinental subduction environment.

关 键 词：中生代 二云二长花岗岩 Lu—Hf同位素 地质意义 武功山 

分 类 号：P534.5[天文地球—古生物学与地层学] P588.121[天文地球—地质学] P597.3