内蒙古阿巴嘎旗白音图嘎地区晚石炭世花岗岩地球化学特征、锆石U-Pb定年及其地质意义  

Geochemical Characteristics,Zircon U-Pb Ages of the Late Carboniferous Granite in Baiyintuga Area,Abaga Banner,Inner Mongolia and Their Geological Significance

作　　者：杨多[1] 陈满[1] 龚全德[1] 陈天红[1] 黄菲[2] 吴昊[1] 李昊璐 

机构地区：[1]武警黄金第四支队,辽宁辽阳111000 [2]东北大学,沈阳110819

出　　处：《地质论评》2017年第5期1209-1225,共17页Geological Review

基　　金：中国地质调查局项目(编号:12120113072500)的成果~~

摘　　要：内蒙古白音图嘎地区位于西伯利亚板块东南缘晚古生代陆缘增生带,地处二连—贺根山板块对接带西北侧,该区发育大量晚古生代花岗岩,主要岩石类型为斑状二长花岗岩和碱长花岗岩。本文对该区花岗岩进行了LA-ICP-MS锆石U-Pb测年和岩石地球化学测试。结果表明:斑状二长花岗岩和碱长花岗岩锆石U-Pb年龄分别为302.8±1.3Ma(MSWD=1.4)和301.1±0.6 Ma(MSWD=0.84),属于晚石炭世;岩石地球化学数据显示,岩体属钾玄岩系,具有高硅(SiO_2=70.83%~75.01%),富碱(Na_2O+K_2O=11.58%~13.20%),贫钙(CaO=0.50%~1.22%)和镁(MgO=0.11%~0.33%)特征。铝饱和指数A/CNK=0.81~1.01,为准铝—弱过铝质花岗岩。岩体整体富集Rb、Th、U等大离子亲石元素(LILEs),亏损Ba、Sr以及高场强元素(HFSEs)Nb、Ta、P、Ti;LERR富集,HERR相对亏损,具有明显的负Eu异常(δEu=0.11~0.43)。初始岩浆温度(759.33℃~801.81℃)和岩石地球化学分析表明,白音图嘎花岗岩具有A型花岗岩特征。同时,低的Nb/Ta(7.38~19.50)、Zr/Hf(29.61~35.26)和Sm/Nd(0.22~0.32)比值指示其源岩为壳源。综合研究表明,白音图嘎花岗岩为陆壳变杂砂岩部分熔融的产物,形成于晚石炭世早期西伯利亚板块和华北板块后碰撞作用的板内伸展环境,为兴蒙造山带晚古生代构造岩浆演化及古亚洲洋闭合的时限提供了新的约束和佐证实例。Located in the northwest part of the Erlian—Hegenshan fault belt, Baiyintuga area has wide distribution of Late Paleozoic granite, comprising mainly byporphyriticmonzogranite andalkali granite, which is a part of the accretion zone on the Late Paleozoic continental margin of southeast Siberian plate. Zircon LA ICP MS U Pb datingage of monzogranite and alkali granite, and petrogeochemical testing were conducted, gained ages 3028±13Ma（MSWD=14）and 3011±06Ma（MSWD=084）of the graniterespectively, belonging toLate Carboniferous.Petrogeochemicalresearches indicate that the granites belong to Potassium basaltic seriesand is characterized by high in silicon （SiO2=7083%～7083%）,alkali （Na2O＋K2O=1158%～132%）, low calcium （CaO=050%～122%） and magnesium （MgO =011%～033%）. The granite is metaluminous to weak peraluminous with A/CNK=081～101.The granite rockare enriched in Rb, Th, U （large ion lithophile elements （LILEs））, but depleted in Ba, Sr and high field strength elements （HFSEs） Nb, Ta, P, Ti; LREE is enriched and HREE relativelydepleted,with obvious negative Eu anomaly （δEu=011～043）.The initial magma temperature （75933～80181℃） and Petrogeochemical analysis showed that the Baiyintuga granite has the characteristics of A type granite. The low Nb/Ta（738～1950）,Zr/Hf （2961～3526） and Sm/Nd （022～032）values indicatedthat its source rock iscontinental crust. Comprehensive studies have shown thatthe Baiyintuga granite were from partial melting of continental crust greywacke and formed in extensional tectonic system of the post collisional Siberian plate and north China plate inLate Carboniferous,which provided new constraints and a supporting instance on the tectonic—magmatic evolution of the Great Hinggan（Da Hinggan）—Inner Mongolia Orogenic Belt in Late Carboniferous and on close time of the Paleo Asian Ocean.

关 键 词：锆石U-PB年龄 A型花岗岩 晚石炭世 后碰撞作用 白音图嘎 

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