内蒙古乌拉特中旗新太古代变质侵入岩的地球化学特征及构造意义  

Geochemical Characteristics and Its Tectonic Significance of Neoarchean Metamorphic Intrusions in Urad Zhongqi Area,Inner Mongolia

作　　者：李剑波 王新亮 侯丽玉 高军锋 古艳春 焦朕 LI Jianbo;WANG Xinliang;HOU Liyu;GAO Junfeng;GU Yanchun;JIAO Zhen(Geological and Mineral Survey Institute of Inner Mongolia,Hohhot,010010;School of Earth Science and Resources,China University of Geosciences,Belting,100083;No.6 Gold Geological Party of PAP,Xining,810000;Inner Mongolia Key Laboratory of Magmatic Mineralization and Ore-Prospecting,Hohhot,010020;Geological Survey Institute of lnner Mongolia,Hohhot,010020)

机构地区：[1]内蒙古地质矿产勘查院,呼和浩特010010 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]武警黄金第六支队,西宁810000 [4]内蒙古自治区岩浆活动成矿与找矿重点实验室,呼和浩特010020 [5]内蒙古自治区地质调查院,呼和浩特010020

出　　处：《地质论评》2018年第5期1167-1179,共13页Geological Review

基　　金：中国地质调查局区域地质调查项目(编号:1212011120707)的成果~~

摘　　要：内蒙古乌拉特中旗地区新太古代变质侵入岩具有明显的Adakite(高锶低钇中酸性岩,亦有人音译为埃达克岩)及TTG岩系特征,空间上与新太古代色尔腾山岩群绿岩密切伴生。其SiO_2含量介于58.24%～71.19%,全碱含量高(Na_2O+K_2O>7%),富钠(Na_2O>3.82%),Na_2O/K_2O>1,铝含量高(Al_2O_3含量通常在13.89%～16.92%之间)。微量元素显示岩石较低的Rb/Sr值(0.06<Rb/Sr<0.28),富集Rb、Sr大离子亲石元素,亏损Th、Nb、Ta高场强元素。稀土元素配分曲线为右倾型,岩石强烈富集LREE,亏损HREE,具弱Eu正异常。采样高灵敏度离子探针(SHRIMP)对其锆石进行了U-Pb测年,测得其年龄分别为2616±24 Ma和2577±19 Ma,表明形成于新太古代,为岩体的结晶年龄。另外,通过对锆石边部进行了变质年龄测试,获得年龄为2504±15 Ma和2486±26 Ma,属于新太古代晚期—古元古代早期,代表了变质年龄。本区新太古代变质侵入岩富Sr、Rb/Sr值低,Mg~#均值为0.53,低于板片俯冲熔融形成高锶低钇中酸性岩的Mg~#值(0.65～0.80),说明本区TTG岩系是加厚下地壳部分熔融形成的。结合区域资料和所分析锆石U-Pb定年数据,乌拉特中旗新太古代岩浆事件在区域上广泛分布,其对应的变质事件在区域上也广泛分布,表明岩浆事件和变质事件是同一热构造事件的产物。因此,我们认为本区的新太古代变质侵入岩岩浆事件是地幔柱底侵导致的,该期的广泛岩浆事件可能与华北克拉通的形成机制有关。Objectives： The Neoarchean intrusions in Urad zhongqi（ Central Urad Banner） area,Inner Mongolia,possesses obvious characteritics of Adakite（ high Sr low Yb intermediate—acid rocks） and TTG rock series.It is associated intently with greenstone of Seertengshan Group Neoarchean in space distribution.It possesses important signifcance in studying the early Earth evolution of the Norh China Craton.Methods： This articale did the study to the Neoarchean granites via SHRIMP ziron U-Pb dating and whole rock geochemistry analysis collected from the Urad Zhongqi Region,Inner Mongolia.Results： The SiO2 content of these intrusive rocks is in the range of 58.24% ～ 71.19%,with a high alkali content（ Na2O＋K2O7%）,enriched in Na（ Na2O 〉3.82%）,Na2O/K2O〉1,high-alumina（ Al2O3 content usually between 13.89% ～ 16.92%）.Trace elements show low Rb/Sr ratio（ 0.06 〈Rb/Sr 〈0.28）,enriched in LILE（ Rb、Sr） and depleted in HFSE（ Th、Nb、Ta）.The SHRIMP was used for the zircon U-Pb dating of the intrusive rocks,and the isotope age is 2616±24 Ma and 2577±19 Ma,indicating that it was formed at the Late Neoarchaean and representing the hydrothermal age.By the edge of zircon testing,obtained isotope is 2504±15 Ma and 2486±26 Ma respectively.between with the Late Neoarchaean to Early Paleoproterozoic,Representing the metamorphic age.The Neoarchaean intrusions in this area enriched in Sr,low Rb/Sr value,the average Mg^# value is 0.53.And result is lower compared with Mg^# （ 0.65～0.80） of adakite formed by slab subduction melting,shows the TTG of this area was formed by partial melting of the thickened crust.Conclusions： Combined with regional geological data and the zircon U-Pb ages,the Neoarchean magmatic activity of Urad zhongqi area is widespread in the whole North China Craton（ NNC） and its corresponding metamorphic event is also widely distributed in area,revealing that both the magmatism and metamorphism were derived from the same tectonic thermal geodynamic precesses.And th

关 键 词：新太古代 侵入岩 SHRIMP 乌拉特中旗 华北克拉通 

分 类 号：P534.2[天文地球—古生物学与地层学] P588.3[天文地球—地质学]