本文關鍵詞： 河流碎屑鋯石 中國西南 青藏高原 U-Pb年齡 Hf同位素　出處：《中國地質(zhì)大學(北京)》2015年碩士論文　論文類型：學位論文

【摘要】：目前,地質(zhì)學的一個熱點課題即探討大陸地殼的形成機制及其演化過程。近年來,越來越多的地質(zhì)工作者致力于分析河流碎屑鋯石,從而探討大陸地殼的形成機制與演化過程。青藏高原位居全球之巔,國內(nèi)外學者都非常重視它是如何形成,又具有怎樣的演化歷程。中國西南三江分別是:金沙江、瀾滄江、怒江。三條江沿著三條縫合帶流淌,分別是:班公湖-怒江縫合帶、龍木錯-雙湖-瀾滄江縫合帶和西金烏蘭-金沙江縫合帶。三條縫合帶是松潘-甘孜地塊、北羌塘-昌都地塊、南羌塘-保山地塊及拉薩地塊之間的界限。我們通過對金沙江、瀾滄江、怒江河流沉積物鋯石的U-Pb年齡結(jié)果來探討三條江可能的源區(qū),源區(qū)重大地質(zhì)事件發(fā)生的時間,相鄰地塊的碰撞拼貼時間,以及古特提斯洋的形成演化歷史;通過對金沙江、瀾滄江、怒江河流碎屑鋯石的Hf同位素研究來探討源區(qū)新生地殼的產(chǎn)生時間,及形成歷史演化。本文獲得的認識有下面4點:1)金沙江河流沉積物U-Pb年齡分為5個階段:98Ma,175~355 Ma,402~639 Ma,730~1200 Ma和1409~3160Ma。主要年齡峰值為229 Ma,832 Ma,1722和2487Ma。瀾滄江河流沉積物U-Pb年齡分為5個階段:177 Ma,201~418 Ma,428~544 Ma,581~1189 Ma和1406~2533 Ma。主要年齡峰值為260 Ma,788 Ma,1827 Ma和2474 Ma。怒江河流沉積物U-Pb年齡分為6個階段:50~74 Ma,84~235 Ma,275~413 Ma,451~569 Ma,657~1429Ma,1602~3436 Ma。主要峰值年齡為65 Ma,110 Ma,500 Ma和900 Ma。2)金沙江和瀾滄江河流碎屑鋯石的源區(qū)可能都是北羌塘地塊,怒江河流碎屑鋯石的源區(qū)主要是中拉薩地塊,北拉薩地塊可能為其提供了很少的物質(zhì)。3)金沙江洋盆于早石炭世打開,并于石炭紀持續(xù)擴張,二疊紀進入消減階段,早、中三疊世羌塘地塊與松潘-甘孜地塊碰撞拼貼,大洋閉合的時間是晚三疊世。瀾滄江洋盆的開裂時間為泥盆紀-早石炭世,發(fā)展到最大面積是在早二疊世,經(jīng)歷了俯沖消減之后,南、北羌塘地塊碰撞拼貼,洋盆最終于晚三疊世末封閉。怒江洋盆于三疊紀形成并和拉薩地塊碰撞,早白堊世俯沖結(jié)束,拉薩地塊與羌塘地塊連接在一起。4)金沙江和瀾滄江河流碎屑鋯石的Hf二階段模式年齡可以共同限定北羌塘地塊的形成演化歷史。新太古代-中元古代,是北羌塘地塊從虧損地幔物質(zhì)增生到地殼的持續(xù)生長階段,此階段增生的地殼物質(zhì)構成現(xiàn)今北羌塘地塊全部地殼物質(zhì)的70%以上。中拉薩地塊東段的形成與演化歷史由怒江河流碎屑鋯石Hf二階段模式年齡得出,地殼最為快速的增生時期是在2.0~1.2 Ga之間。
[Abstract]:At present, a hot topic in geology is to study the formation mechanism and evolution process of continental crust. In recent years, more and more geologists have devoted themselves to the analysis of river detrital zircon. Therefore, the formation mechanism and evolution process of the continental crust are discussed. The Qinghai-Tibet Plateau is at the top of the world, and scholars at home and abroad attach great importance to its formation and evolution. The three rivers in southwest China are the Jinsha River and the Lancang River, respectively. Nujiang River. The three rivers flow along three suture zones, namely, the Bangonghu and Nujiang suture zones, the Longmuco-Shuanghu-Lancang River suture zone and the Xijin Wu Lan Jinsha River suture zone. The three suture zones are the Songpan-Ganzi block. The boundary between the northern Qiangtang Changdu block, the southern Qiangtang Baoshan block and the Lhasa block. The U-Pb age results of zircon from sediments of Jinsha, Lancang and Nujiang rivers are used to study the possible source regions of the three rivers. The time of major geological events in the source area, the time of collision and collage of adjacent blocks, and the history of the formation and evolution of the ancient Tethys ocean. HF isotopic study of detrital zircon from the Nujiang River to study the time of the birth of the new crust in the source region, The U-Pb age of Jinsha River sediment is divided into five stages: 9: 1) the U-Pb age of Jinsha River sediment is divided into five stages: 9: 98 Ma, 175,355 Ma-402U 639 Ma, 7301200Ma and 1409 Ma, 3160 Ma. The main age peaks are 229 Ma, 832 Ma, 1722 and 2487 Ma. the U-Pb age of the sediments of the Jinsha River is divided into five stages. The U-Pb age of the sediments of the Jinsha River is divided into five stages. The U-Pb age of the sediments of the Jinsha River is divided into 5. The main age peaks are 260 Ma, 788 Ma, 1827 Ma and 2474 Ma. The U-Pb age of the Nujiang River sediment is divided into six stages, the U-Pb age of the Nujiang River is divided into 6 stages, namely, the U-Pb age of the Nujiang River, consisting of 6 stages, namely, the U-Pb age of 275413 Ma451 569 Ma 657 1429 Ma 1602N 3436. The main peak age is 65 Ma110 Mai 500 Ma and 900 Ma.2) the Jinsha River and Lancang rivers. The source region of the detrital zircon may be the northern Qiangtang block. The source region of the detrital zircon of the Nujiang River is mainly the Middle Lhasa block, and the northern Lhasa block may have provided it with very little material .3) the Jinsha River ocean basin opened in the early Carboniferous and continued to expand during the Carboniferous, and the Permian period entered the stage of subduction. The middle Triassic Qiangtang block collided with the Songpan-Ganzi block, and the time of ocean closure was the late Triassic. The cracking time of the Lancang River ocean basin was Devonian and early Carboniferous, and the largest area developed in the early Permian. After subduction, the southern and northern Qiangtang blocks collide and collage, and the ocean basin is finally closed at the end of the late Triassic. The Nujiang ocean basin formed in the Triassic and collided with the Lhasa block, and the early Cretaceous subduction ended. The HF two-stage age of zircon from the Jinsha and Lancang rivers can jointly define the formation and evolution history of the northern Qiangtang massif. It is a stage of sustained growth from depleted mantle material to crustal growth in the northern Qiangtang block. The formation and evolution history of the eastern segment of the Middle Lhasa block is derived from the age of detrital zircon HF model of the Nujiang River. The fastest period of crustal growth is between 2.0 and 1.2 Ga.
【學位授予單位】：中國地質(zhì)大學(北京)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P597.3;P588.21

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