【作者】 王颖；

【导师】 徐仲元；

【作者基本信息】 吉林大学 ， 构造地质学， 2020， 硕士

【摘要】 得耳布尔位于内蒙古根河市,地处大兴安岭北段。该地区经历了自古生代以来的一系列地质构造活动,形成了种类丰富的火山岩。通过野外地质调查,了解该地区区域地质背景。利用火山岩岩相学、年代学及岩石地球化学,讨论岩浆活动期次、岩石成因和构造背景,结合前人研究成果,进而还原大兴安岭地区构造演化过程。本文取得的成果如下:1.塔木兰沟组以安山岩、安山质凝灰岩、辉石安山岩及玄武安山岩为主。LA-ICP-MS锆石U-Pb分析测试结果表明,塔木兰沟组多为捕获锆石,通过资料整理分析,推测其形成时代为中侏罗世。其中捕获锆石年龄1625±36²661±27Ma,可知地块存在前寒武纪基底。岩石富铝（Al₂O₃=16.68%¹6.91%）,富镁（Mg^#=50.37⁵2.34）,为中基性高钾钙碱性准铝质岩石。大离子亲石元素Ba、Sr的强烈富集,高场强元素Nb、Ta亏损,微弱的负Eu异常（δ Eu=0.92⁰.96）,大陆岛弧元素分配模式相似。岩石成因为俯冲流体交代的大陆岩石圈地幔部分熔融,形成于俯冲的活动大陆边缘构造背景。2.满克头鄂博组以流纹岩、球粒流纹岩、流纹质凝灰岩和流纹质火山角砾岩为主。LA-ICP-MS锆石U-Pb测年结果为155±1.8Ma,形成时间为晚侏罗世。为富硅（Si₂O=74.7%⁷5.44%）、富钾（K₂O=4.97%⁵.85%）、贫钠（Na₂O=0.1%⁰.12%）、贫钙（CaO=0.14%⁰.16%）的过铝质高硅流纹岩。满克头鄂博组火山岩Rb/Sr比值为4.1¹0.3,La_N/Yb_N比值为13.98²0.83,富集Zr、Cs及Rb元素,亏损Ba、Nb、Ta及P元素,Sr和Ti强烈亏损,明显的负铕异常（δEu=0.59⁰.7）。满克头鄂博组具有S型花岗岩特征,为加厚下地壳部分熔融的岩浆在岩浆房内经晶粥体模型（MUSH）再次演化形成。中侏罗世晚期,区域上为陆-陆碰撞的构造背景。3.玛尼吐组以安山岩、安山质凝灰岩和英安质凝灰岩为主。LA-ICP-MS锆石U-Pb测年结果为122.8±1.3Ma和124.1±0.8Ma,形成时间为早白垩世。轻重稀土元素分馏明显,富集Zr、Rb、Th和U,亏损Sr、Ba、Nb、Ta、P和Ti,明显的负Eu异常（δEu=0.65⁰.76）。La_N/Yb_N比值为9.22¹0.36,Rb/Sr比值为0.31¹.21,平均值为0.58,具有A型花岗岩特征,是在伸展构造背景下通过地壳降压熔融形成。4.火山岩成岩年龄呈现出从北向南逐渐年轻的特征。结合前人研究成果,认为大兴安岭地区中生代晚期,构造背景由中侏罗世的蒙古-鄂霍茨克洋洋壳向南俯冲环境,中侏罗世晚期为蒙古-鄂霍茨克洋闭合后的的陆-陆碰撞环境,早白垩世变为陆-陆碰撞造山后的伸展环境。推断中生代晚期大兴安岭地区火山活动主要受蒙古-鄂霍茨克洋构造域控制。更多还原

【Abstract】 Deerbuer is located in Genhe city,Inner Mongolia,belong to the northern segment of the Great Xing’an Rang.It has experienced a series of geological tectonic activities since the Paleozoic,forming a variety of volcanic rocks.Through the field geological surveying to get the regional geological background in this area.Based on the study of petrography,chronology and geochemistry,this paper discusses the magmatic activity,rock genesis and tectonic background,combined with previous research,restore the tectonic evolution process of the Great Xing’an Rang.The main results are as follows:（1）Tamulangou Formation is mainly composed of andesite,andesitic tuff,pyroxene andesite and basaltic andesite.LA-ICP-MS zircon U-Pb dating show that the most zircon of Tamulangou Formation are captured zircon,based on the analysis of stratigraphic contacts,it is inferred that Tamulangou Formation was formed in the Middle Jurassic.The age of captured zircon ranged from（1625±36）to（2661±27）Ma,indicating the existence of Precambrian basement.Rocks rich in aluminum（Al₂O₃=16.68%¹6.91%）and magnesium（Mg^#=50.37⁵2.34）,belong to high-K calc-alkaline series,quasi-aluminous volcanic rocks.It is similar to the distribution pattern of continental island arc elements which intense enrichment in LILEs（Ba,Sr）,depletion in HFSEs（Nb,Ta）and weak negativeδEu（δEu=0.92⁰.96）.The Tamulangou Formation were formed in the tectonic setting of subducting active continental margin,result from partial melting of continental lithospheric mantle by subduction fluid replacement.（2）The Manketouebo Formation is mainly composed of rhyolite,spherulite rhyolite,rhyolitic tuff and rhyolite volcanic breccia.The LA-ICP-MS zircon U-Pb dating show that the age of Manketouebo Formation is 155±1.8Ma,which is Late Jurassic.The Manketouebo Formation is composed of peraluminous high-silica rhyolite,which is enriched in silicon（Si2O=74.7%⁷5.44%）and K（K₂O=4.97%⁵.85%）,depleted in Na（Na₂O=0.1%⁰.12%）and Ca（CaO=0.14%⁰.16%）.The volcanic rocks of the Manketouebo Formation have the characteristics of S-type granite which the Rb/Sr ratio is 4.1¹0.3,the La_N/Yb_N ratio is 13.98²0.83,enrichment of Zr,Cs and Rb,depletion of Ba,Nb,Ta and P,strong depletion of Sr and Ti,obvious negative anomaly ofδEu（δEu=0.59⁰.7）.It is product of further evolution of magma under MUSH model in magma chamber,which originally formed by the partial melting of thickened lower crust.During the late Middle Jurassic,the tectonic setting of the regional continental collision.（3）The Manitu Formation is mainly composed of andesite,andesitic tuff and dacite tuff.The LA-ICP-MS zircon U-Pb dating show that the age of Manitu Formation is between 122.8±1.3Ma and 124.1±0.8Ma,which is Early Cretaceous.HREE and LREE are obviously fractionated,enriched Zr,Rb,Th and U,defective Sr,Ba,Nb,Ta,P and Ti,and obviously negative Eu abnormal（δEu=0.65⁰.76）.The volcanic rocks have the characteristics of A-type granite with the ratio of LaN/YbN is 9.22¹0.36 and the Rb/Sr ratio is 0.31¹.21（average value is 0.58）,it was formed by crustal decompression melting in extension background.（4）The age of volcanic diagenesis is characterized by a gradual youth from north to south.Combined with previous researches,it is concluded that the tectonic environment in the Great Xing’an Range was that the Mongolia-Okhotsk Ocean crust experienced southward subduction in Middle Jurassic.In the Late Middle Jurassic,the Mongolia-Okhotsk Ocean was closed with continental collision environment.In Early Cretaceous,the Great Xing’an Range was in a post orogenicextensional tectonic environment.It is concluded that the Late Mesozoic volcanic activities in the Great Xing’an Range were mainly controlled by the Mongolia-Okhotsk Ocean tectonic domain.更多还原