發(fā)布時(shí)間：2018-01-02 16:01

  本文關(guān)鍵詞：海拉爾北部八大關(guān)地區(qū)花崗巖的年代、地球化學(xué)特征與成因研究　出處：《吉林大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 花崗巖 鋯石U-Pb測(cè)年 Hf同位素 地球化學(xué) 巖石成因 八大關(guān)

【摘要】：海拉爾北部八大關(guān)地區(qū)位于中俄兩國(guó)交界處,大地構(gòu)造位置屬于額爾古納地塊,處在著名的德?tīng)柌几蓸?gòu)造帶上。額爾古納地塊北側(cè)為蒙古-鄂霍茨克褶皺帶,南緣被南蒙晚古生代古海洋沉積物所覆蓋,是古亞洲洋構(gòu)造域、環(huán)太平洋構(gòu)造域與蒙古鄂霍茨克構(gòu)造域強(qiáng)烈疊加、復(fù)合、轉(zhuǎn)換部位,構(gòu)造形跡極其復(fù)雜,對(duì)研究東北地區(qū)構(gòu)造演化起著重要作用。近年來(lái),諸多學(xué)者對(duì)額爾古納地塊北部花崗巖時(shí)代、地球化學(xué)特征與巖石成因進(jìn)行了詳細(xì)研究,積累了一大批高精度鋯石U-Pb和40Ar/39Ar同位素年齡與地球化學(xué)資料,然而對(duì)其西緣即八大關(guān)地區(qū)的花崗巖年代學(xué)和地球化學(xué)特征的研究相對(duì)薄弱,尤其是Hf同位素的研究更為少見(jiàn),前人主要是依據(jù)花崗巖與地層之間的接觸關(guān)系、變質(zhì)程度、變形特征與K-Ar定年結(jié)果,但是由于八大關(guān)地區(qū)構(gòu)造形跡復(fù)雜,花崗巖大部分都經(jīng)過(guò)后期改造,破壞了樣品中原有的同位素體系,因此這些花崗巖年齡不能反應(yīng)八大關(guān)地區(qū)花崗巖的巖漿侵位年齡,而地化數(shù)據(jù)缺失制約了對(duì)其成因的深入理解。鑒于此,本文對(duì)八大關(guān)地區(qū)的花崗巖進(jìn)行了年代學(xué)與地球化學(xué)及鋯石Hf同位素研究,精準(zhǔn)地界定了花崗巖的具體形成時(shí)期,探討了其形成機(jī)制以及所產(chǎn)生的構(gòu)造環(huán)境,為東北地區(qū)區(qū)域構(gòu)造演化提供了新的依據(jù)。1.花崗巖的組合類(lèi)型及形成時(shí)代八大關(guān)地區(qū)花崗巖由正長(zhǎng)花崗巖和二長(zhǎng)花崗巖組成。鋯石U-Pb同位素測(cè)年結(jié)果顯示,正長(zhǎng)花崗巖年齡為216~226Ma,二長(zhǎng)花崗巖年齡為212~220Ma,總體來(lái)看,八大關(guān)地區(qū)花崗巖的形成時(shí)代非常接近,均為晚三疊世。2.花崗巖的地球化學(xué)特征正長(zhǎng)花崗巖SiO_2含量較高,w(SiO_2)=71.34%~76.41%,鋁弱過(guò)飽和,w(Al_2O_3)=10.86%~15.61%,A/CNK比值為1.02~1.10(分子數(shù)),全堿含量較高,w(K_2O)+w(N_2O)=7.37%~10.00%,K_2O/Na_2O=1.12~1.35,相對(duì)富鉀,鎂鈣含量較低,w(MgO)=0.08%~0.31%,w(CaO)=0.33%~0.44%,花崗巖分異程度較高(DI=92.48~95.80),稀土配分曲線呈右傾型,稀土總量∑REE=112.37×10~(-6)~193.13×10~(-6),具有中等的負(fù)銪異常(δEu=0.51~0.71),微量元素富集大離子親石元素Zr、Hf、Rb、Th、K,虧損高場(chǎng)強(qiáng)元素P、Ti、Nb、Ta等。二長(zhǎng)花崗巖主量元素分析結(jié)果顯示,w(SiO_2)=75.86%~77.75%,w(Al_2O_3)=10.99%~11.78%,A/CNK比值介于1.01~1.10之間,為弱過(guò)鋁質(zhì),w(MgO)=0.27%~0.31%,w(CaO)=0.33%~0.62%,含量偏低,全堿含量高w(K_2O)+w(N_2O)=6.59%~8.01%,花崗巖分異指數(shù)介于93.35~94.14之間。稀土總量(∑REE)為141.66×10~(-6)~164.75×10~(-6),在其配分曲線中顯示為輕稀土富集的右傾型特征,銪為中等負(fù)異常型(δEu=0.56~0.65),微量元素上,Rb、Th、K等大離子親石元素(LILE)較為富集,Nb、Ta、P、Ti等高場(chǎng)強(qiáng)元素(HFSE)較為虧損。綜上所述,八大關(guān)地區(qū)花崗巖具有相似的主、微量元素特征和變化規(guī)律,如均富硅、高堿、貧鎂鈣,均為弱過(guò)鋁質(zhì)花崗巖,其稀土配分曲線均為右傾型,分異指數(shù)均較高(DI90)等,根據(jù)地球化學(xué)特征,判斷其八大關(guān)地區(qū)的正長(zhǎng)花崗巖和二長(zhǎng)花崗巖均為高分異的I型花崗巖。3.花崗巖的巖石成因及構(gòu)造背景八大關(guān)地區(qū)花崗巖鋯石Hf同位素?cái)?shù)據(jù)顯示:正長(zhǎng)花崗巖和二長(zhǎng)花崗巖εHf(t)均為正值,介于4.50~10.45,兩種花崗巖在t-εHf(t)圖解上均落入球粒隕石演化線之上并且比較集中,二階段Hf模式年齡較為年輕,為新元古代(0.59~0.97 Ga)。結(jié)合地球化學(xué)特征及區(qū)域構(gòu)造演化等方面成果,認(rèn)為花崗巖漿來(lái)源于蒙古鄂霍茨克洋板塊向南俯沖背景下新元古代新增生的基性地殼物質(zhì)部分熔融。
[Abstract]:Ba Da Guan in northern Hailar area is located in the Sino Russian border, tectonically belongs to the Eergu'Na block, in the famous Del cloth dry tectonic belt of Eergu'Na block. On the north side of the Mongolia Okhotsk fold belt, southern margin of the late Paleozoic marine sediments were Nanmeng covered, is the paleo Asian Ocean, circum Pacific tectonic domain and Mongolia the Okhotsk tectonic domain strongly superimposed composite conversion parts, structural feature is extremely complex, to study the tectonic evolution of Northeast China plays an important role. In recent years, many scholars of the northern part of the Eergu'Na massif granite age, geochemical characteristics and petrogenesis are studied in detail, the accumulation of a large number of high precision zircon U-Pb and 40Ar/39Ar isotopic age with the geochemical data, however on the west edge of Ba Da Guan area granite geochronology and geochemistry of the study on the weak, especially The Hf isotope study is more rare, the former is mainly based on the contact relationship between the granite and strata metamorphism, deformation features and K-Ar dating results, but because of the Ba Da Guan area with complex structural features of granite mostly after transformation, destroyed the original isotopic system in the sample, so these granite granite age can not be the reaction in the Ba Da Guan area of magmatic emplacement age, and lack of data restricts the understanding of its causes. In view of this, this paper study on geochronology and isotope geochemistry and zircon Hf on the Ba Da Guan area of granite, precise definition of the specific formation period of granite, discusses its formation mechanism and tectonic environment produced the.1. provides a new basis for the combination types of granite granite formation and age of the Ba Da Guan area as the regional tectonic evolution of Northeast China By syenogranite monzogranite and two zircon U-Pb isotopic dating results show that syenogranite ages 216~226Ma, two granite ages 212~220Ma, overall, formation age is very close to the Ba Da Guan area are granite, geochemical characteristics of Late Triassic Granites is three.2. long high granite content of SiO_2, w (SiO_2) =71.34%~76.41%, weakly peraluminous and saturated w (Al_2O_3) =10.86%~15.61%, A/CNK = 1.02~1.10 (number of molecules), total alkali content is higher, w (K_2O) +w (N_2O) =7.37%~10.00%, K_2O/Na_2O=1.12~1.35, relatively rich in potassium, calcium and magnesium content is low, w (MgO) =0.08%~0.31%, w (CaO) =0.33%~0.44%. Granite high degree of differentiation (DI=92.48~95.80), REE distribution curve right type, the total rare earth Sigma REE=112.37 * 10~ (-6) ~193.13 * 10~ (-6), with moderate negative Eu anomaly (delta Eu=0.51~0.71), trace element enrichment in large ion lithophile elements Zr, H f,Rb,Th,K,浜忔崯楂樺満寮哄厓绱燩,Ti,Nb,Ta絳，

本文編號(hào)：1369911