發(fā)布時間：2018-04-15 01:03

  本文選題：大興安嶺中段 + 鋯石U-Pb年代學��； 參考：《吉林大學》2017年碩士論文

【摘要】：大興安嶺位于中亞造山帶東段,以大面積的中生代火成巖分布為主要特征。近年來隨著LA-ICPMS、LA-MC-ICPMS等先進實驗測試技術的應用,前人對大興安嶺一帶花崗質巖石進行了較為細致的研究,取得了大量的成果,但大興安嶺地區(qū)中段晚中生代花崗質巖石的研究程度較低,限制了對大興安嶺地區(qū)中段晚中生代花崗質巖石的形成時代和成因的認識。本文將大興安嶺中段五岔溝地區(qū)晚中生代花崗質巖石作為研究對象,在區(qū)域地質調查為基礎上,對大興安嶺中段五岔溝地區(qū)晚中生代花崗質巖石進行了鋯石U-Pb年代學、Lu-Hf同位素和全巖地球化學研究,從而厘定了花崗質巖石的形成時代,討論了大興安嶺中段五岔溝地區(qū)晚中生代花崗質巖石巖石成因以及相關的地球動力學背景。本文對五岔溝地區(qū)7件花崗質巖石樣品進行LA-ICP-MS鋯石U-Pb同位素分析,測試分析結果顯示,鋯石多為自形-半自形,呈粒狀或短柱狀,發(fā)育清晰的振蕩生長環(huán)帶,具有較高的Th/U比值(0.63~1.84),暗示其巖漿成因。樣品的206Pb/238U加權平均年齡分別為133±1Ma、134±1Ma、127±1Ma、131±2Ma、132±1Ma、129±1Ma、129±2Ma,表明大興安嶺中段五岔溝地區(qū)花崗質巖石的形成時代為早白堊世。巖石地球化學結果顯示,大興安嶺中段五岔溝地區(qū)花崗質巖石普遍具有高硅(SiO2=65.21%~78.43%,平均71.82%),富堿(K2O+Na2O=6.77%~9.66%,平均8.22%),相對低CaO(0.10%~2.55%),MgO(0.07%~1.30%),P2O5(0.01%~0.20%)的特征,A/CNK值介于0.94~1.51,主體為準鋁質-弱過鋁質巖石;微量元素表現(xiàn)出輕稀土富集的“右傾”配分模式,以及不同程度的負Eu異常,富集Rb、Th、U、K等大離子親石元素,虧損Nb、Ta、Ti、P等高場強元素,顯示大興安嶺中段五岔溝地區(qū)花崗質巖石為I型花崗巖;鋯石原位Hf同位素分析表明,大興安嶺中段五岔溝地區(qū)花崗質巖石的176Hf/177Hf比值分布于0.282833~0.282930,εHf(t)值介于4.9~8.4,鋯石Hf二階段模式年齡(654~874Ma)。通過年代學、地球化學以及Hf同位素研究,并結合區(qū)域地質資料及同時期火成巖物質的時空展布規(guī)律,認為大興安嶺中段五岔溝地區(qū)花崗質巖石的源區(qū)為新元古代期間新增生的地殼物質的部分熔融,其形成與古太平洋板塊俯沖作用背景下的伸展環(huán)境有關。
[Abstract]:The Daxingan Mountains are located in the eastern part of the Central Asian orogenic belt and are characterized by large area distribution of Mesozoic igneous rocks.In recent years, with the application of LA-ICPMS-LA-MC-ICPMS and other advanced experimental and testing techniques, the granitic rocks in the Daxing'anling area have been studied in detail and a great deal of achievements have been made.However, the study of late Mesozoic granitic rocks in the middle part of Daxinganling area is relatively low, which limits the understanding of the formation age and genesis of late Mesozoic granitic rocks in the middle part of Daxinganling area.In this paper, the late Mesozoic granitic rocks in Wuchaigou area, central Daxing'anling Mountains, are taken as the research objects, and based on the regional geological survey,The late Mesozoic granitic rocks in the Wuchaigou area of the central Daxinganling Mountains have been studied by zircon U-Pb geochronology, Lu-Hf isotopic and whole-rock geochemistry, and the formation age of the granitic rocks has been determined.The genesis of late Mesozoic granitic rocks and the related geodynamic background in Wuchagou area of Daxing'anling Mountains are discussed.In this paper, LA-ICP-MS zircon U-Pb isotopic analysis of 7 granitic rock samples in Wuchagou area is carried out. The results show that the zircon is mostly self-semiautomorphic, granular or short columnar, and has a clear oscillatory growth ring.It has a high Th/U ratio of 0.63 ~ 1.84, indicating its magmatic origin.The 206Pb/238U weighted mean age of the samples is 133 鹵1 Ma, 134 鹵1 Ma, 127 鹵1 Ma, 131 鹵2 Ma, 132 鹵1 Ma, 129 鹵1 Ma, 129 鹵2 Ma, indicating that the age of granitic rocks in Wuchagou area, Daxing'an Mountains, is early Cretaceous.The petrogeochemical results show that the granitic rocks in the Wuchagou area of the middle part of the Daxing'anling Mountains are generally characterized by high SiO2SiO2 (65.21), with an average of 71.82%, and alkali-rich K2O Na2O6.777.77 with 9.66, with an average of 8.2220, and a relatively low CaO0.102.55MgO0.07 (1.30P2O5 / 0.01 0.20K). The ACNK value of the main body is between 0.941.551 and 0.941.51and the main body is aluminum-weakly peraluminous rock, which is characterized by the relative low CaO0.102.55MgO0.07mg _ 2O _ (0.07) mg _ 2O _ (0.07) and the relative low CaO0.102.55mg _ 2O _ (0.07) mg _ 2O _ (0.07)).The trace elements show a "right-dip" distribution pattern of LREE enrichment, and negative EU anomalies to varying degrees, enriched in large ion lithophile elements, such as Rbtr, Th, U, K, and depleted high field strength elements, such as NbTa-Ta-Ti-P, etc.The results show that the granitic rocks in Wuchagou area are I-type granites and zircon in-situ HF isotopic analysis shows that the 176Hf/177Hf ratio of granitic rocks in Wuchagou area is 0.282833 0.282930 with 蔚 Hftand between 4.9 and 8.4, and the zircon HF two-stage model age is 6540.874MaHU.By means of geochronology, geochemistry and HF isotope studies, combined with regional geological data and temporal and spatial distribution of igneous materials in the same period,It is considered that the source region of granitic rocks in Wuchagou area of Daxing'anling Mountains is the partial melting of newly accretionary crustal materials during the Neoproterozoic, which is related to the extensional environment in the background of paleo-Pacific plate subduction.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P588.1

【相似文獻】

相關期刊論文 前10條

1 李福春,朱金初,張林松,饒冰,張佩華;富氟花崗質熔體形成和演化的實驗研究[J];巖石學報;2003年01期

2 夏祖春,徐學義,夏林圻,李向民,馬中平,王立社;天山石炭-二疊紀后碰撞花崗質巖石地球化學研究[J];西北地質;2005年01期

3 王守信;;甘肅省花崗質巖石的成因探討[J];西北地質;1985年05期

4 Shunso Ishihara;Atsuyuki Mizuno;靳娟娟;;日本九州島西南沿海甑海丘花崗質礫石的年齡[J];世界地質;1988年01期

5 凌賢長;撫順東部地區(qū)紫蘇花崗質巖石特征及成因[J];吉林地質;1995年02期

6 施性明 ,趙元進 ,趙希o，

本文編號：1751800