本文選題：大興安嶺 + 鋯石U-Pb年齡��； 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：論文選取大興安嶺中段索倫地區(qū)廣泛發(fā)育的瑪尼吐組火山巖為研究對(duì)象,在結(jié)合前人研究成果的基礎(chǔ)上,進(jìn)一步查證了瑪尼吐組火山巖的巖石組合特征與分布規(guī)律,厘定了火山巖形成的時(shí)代,分析了火山巖的地球化學(xué)特征,探討了火山巖的巖漿源區(qū)性質(zhì)、巖石成因以及構(gòu)造動(dòng)力學(xué)背景,其成果為大興安嶺中段晚侏羅世-早白堊世的火山活動(dòng)時(shí)間及其構(gòu)造演化歷史提供了新的資料。1.火山巖的巖石學(xué)特征火山巖以安山巖,粗安巖和英安巖、安山質(zhì)凝灰熔巖為主,見少量安山質(zhì)凝灰?guī)r、英安質(zhì)凝灰?guī)r,其間夾有零星沉凝灰?guī)r。其中安山巖是該組火山巖的主要組成部分。2.瑪尼吐組火山巖的年代學(xué)特征鋯石LA-ICPMS U-Pb測年結(jié)果顯示,三件安山巖樣品形成時(shí)代分別為132±2Ma、130±3Ma、130±1Ma,表明研究區(qū)內(nèi)瑪尼吐組火山巖主要形成于早白堊世。3.火山巖的地球化學(xué)特征SiO_2含量介于52.11-69.63%之間。在TAS圖解中,分別落入玄武安山巖、粗面玄武質(zhì)安山巖、粗安巖、粗面巖區(qū)域,為高鉀鈣堿性弱過鋁質(zhì)巖石�？傮w表現(xiàn)為富堿,及貧鈣、鎂的特征。微量元素特征顯示富集大離子親石元素(LILE)K、Rb、Th和輕稀土元素;虧損高場強(qiáng)元素(HFSE)Nb、Ta、P、Ti。同時(shí)微量元素具高Sr(多499)和低Yb(最大值為2.833.6)、Y(多29.9)、和高Sr/Y和低Rb/Sr比值。同時(shí)參考各構(gòu)造環(huán)境微量元素對(duì)比數(shù)值,均顯示了弧火山巖的特征。4.火山巖的源區(qū)性質(zhì)及巖漿演化特征研究區(qū)瑪尼吐期火山巖Rb/Sr比值變化于0.01~0.28之間,平均為0.11,高于原始地幔(0.03)、E-MORB(0.033)、OIB(0.047)的Rb/Sr比值,也低于殼源巖漿(0.5);Th/U比值在2.03~4.40之間,平均為3.34,介于殼源巖石(≈6)與原始地幔之間;εHf(t)值為+9.10±1.10,處于更靠近虧損地幔線的位置�，斈嵬缕诎采劫|(zhì)巖石源區(qū)主要為巖石圈地幔的部分熔融,且?guī)r漿形成的過程中受到了流體的改造作用。5.瑪尼吐組火山巖形成的構(gòu)造背景瑪尼吐組火山巖形成于島弧構(gòu)造環(huán)境。該島弧構(gòu)造背景的產(chǎn)生可能與受古太平洋板塊俯沖作用有關(guān)。
[Abstract]:In this paper, the widely developed volcanic rocks of Manitu formation in the middle part of the Daxing'anling Mountains are selected as the research objects. On the basis of the previous research results, the rock assemblages and distribution of the volcanic rocks in the Manitu formation are further verified.The forming age of volcanic rocks is determined, the geochemical characteristics of volcanic rocks are analyzed, and the magmatic origin, petrogenesis and tectonic dynamic background of volcanic rocks are discussed.The results provide new data for the late Jurassic-early Cretaceous volcanic activity time and tectonic evolution history of the central Daxing'anling Mountains.The petrological characteristics of volcanic rocks are composed of andesite, trachyandite and dacite, andesite tuff, a small amount of anshanian tuff and dolomite tuff, which are intercalated with sporadic tuff.Andesite is the main component of volcanic rocks in this group.Zircon LA-ICPMS U-Pb dating of volcanic rocks in Manitu formation shows that the age of formation of the three andesite samples is 132 鹵2 Ma, 130 鹵3 Ma, 130 鹵1 Ma, respectively, indicating that the volcanic rocks of the Manitu formation in the study area were mainly formed in the early Cretaceous. 3.The SiO_2 content of volcanic rocks is between 52.11-69.63%.In the TAS diagram, they fall into Black Tortoise andesite, rough Black Tortoise andesite, coarse andesite and rough rock area, which are high potassium calc alkaline weak peraluminous rocks.The general performance is rich in alkali, as well as the characteristics of poor calcium and magnesium.The characteristics of trace elements show that they are enriched in large ion lithophile element LILEN Ku RbN Th and light rare earth elements, and are depleted in high field strength elements such as HFSEE, NbSe, NbSe, Pnb, Th, Th, Th, Th and Th.At the same time, the trace elements have high Sr (more than 499) and low Yb (the maximum value is 2.833.6) (more than 29.9%), and high Sr/Y and low Rb/Sr ratio.At the same time, the characteristics of arc volcanic rocks are shown by referring to the comparative values of trace elements in each tectonic environment.The Rb/Sr ratio of the volcanic rocks in Manitu period varies from 0.01 to 0.28, with an average of 0.11, which is higher than the Rb/Sr ratio of 0.03 and E-MORBN 0.033 OIBN 0.047 in the primitive mantle, and is also lower than that of the crust-derived magma in the range of 2.034.40.The average value is 3.34, which is between crust-derived rocks (鈮，

本文編號(hào)：1771209