發(fā)布時間：2018-07-04 17:45

  本文選題：特提斯喜馬拉雅 + 中生代��； 參考：《成都理工大學(xué)》2017年碩士論文

【摘要】：特提斯喜馬拉雅東段的中生代沉積記錄對認識特提斯構(gòu)造演化具有重要意義。本文對特提斯喜馬拉雅東段洛扎-隆子一帶的中生代裂谷盆地進行了初步研究。研究區(qū)裂谷盆地的發(fā)育時限為晚三疊世到早白堊世,經(jīng)歷了晚三疊世-中侏羅世和晚侏羅世-早白堊世兩個擴展過程,其西南邊界可能位于打隆-洛扎-曲卓木一帶。研究區(qū)的盆地充填過程可分為兩個階段,第一階段為初始陸緣裂谷盆地階段,包括涅如組大陸斜坡相復(fù)理石序列、日當組陸棚邊緣盆地相序列、陸熱組淺海陸棚序列;第二階段為以強烈的火山噴發(fā)活動為特色的陸緣裂谷盆地階段,主要包括了遮拉組火山-細碎屑淺海沉積序列、維美組濱�！侵尴喑练e序列和桑秀組火山-細碎屑沉積序列。物源分析表明,從涅如組到維美組,它們均以450-650Ma和750-1000Ma的優(yōu)勢年齡為特征,顯示了強烈的印度親緣性,但是區(qū)域上的涅如組存在拉薩物源區(qū)。維美組鉻尖晶石以低Al2O3(0.50%-20.82%)、高Cr#(0.51-0.99)和Fe2+/Fe3+比值(2.14-41.27)、以及具有變化的TiO2含量(0.00%~1.95%)為特征,母巖可能為特提斯喜馬拉雅石炭二疊紀地層。通過沉積充填序列和物源對比分析,本文認為涅如組和朗杰學(xué)群是兩套不同的地層單元,并進一步提出在晚三疊世末期班公湖怒江洋向南俯沖于拉薩地體之下引起的板片回轉(zhuǎn)導(dǎo)致拉薩地體與印度北緣之間發(fā)生弧后裂谷作用,由于裂谷很狹窄,以至于拉薩地體能同時為朗杰學(xué)群和涅如組提供物源,只是朗杰學(xué)群接收了更多的拉薩物源供給,而涅如組具有更多的印度物源親緣性。早侏羅世初期,俯沖板片進一步回轉(zhuǎn)導(dǎo)致拉薩地體開始向北漂移和新特提斯弧后洋盆開始擴張,此時,印度北緣成為研究區(qū)侏羅系地層的唯一物源區(qū)。
[Abstract]:Mesozoic sedimentary records in the eastern part of the Tethys Himalayas play an important role in understanding the tectonic evolution of Tethys. The Mesozoic rift basin in the eastern part of the Tethys Himalayas is studied in this paper. The development time of rift basin in the study area is from late Triassic to early Cretaceous, and it has undergone two extension processes: late Triassic-Middle Jurassic and late Jurassic-early Cretaceous. The southwestern boundary of rift basin may be located in the area of Dalon-Luoza-Quzomu. The filling process of the basin in the study area can be divided into two stages. The first stage is the initial continental margin rift basin stage, which includes the sequence of continental slope facies of the Neiru formation, the sequence of the shelf margin basin facies of the Ridang formation, and the sequence of the shallow sea shelf of the continental heat formation. The second stage is the continental margin rift basin stage characterized by strong volcanic eruptive activity, which mainly includes the Jura formation volcanic-fine clastic shallow sea sedimentary sequence. The littoral-delta facies sedimentary sequence and the volcanic-fine clastic sedimentary sequence of the Sangxiu formation in the Weimei formation. The provenance analysis shows that the dominant ages of 450-650 Ma and 750-1000 Ma are the dominant ages from the Neru formation to the Weimei formation, showing strong Indian kinship, but there is a provenance in Lhasa in the Nelu formation. The chrome spinel of the Weimei formation is characterized by low Al _ 2O _ 3 (0.50-20.82%), high Cr # (0.51-0.99) and Fe _ 2 / Fe _ 3 ratios (2.14-41.27), and a variable TIO _ 2 content (0.000.95%). The parent rock may be Tethyan Himalayan Carboniferous Permian formation. Based on the analysis of sedimentary filling sequence and provenance correlation, it is considered that the Nelu formation and the Namgyai group are two different sets of stratigraphic units. Furthermore, it is proposed that the plate rotation caused by the subduction of the Nujiang River in Bangong Lake south under the Lhasa terrane at the end of the late Triassic led to a backarc rift between the Lhasa terrane and the northern margin of India, which is very narrow. The physical ability of Lhasa provides both Namgyai and Neru groups with material resources, but the Namgyai group receives more supplies of Lhasa material sources, and Nelu Group has more affinity of Indian provenances. In the early Jurassic, the subduction plate further turned to cause the Lhasa terrane to drift northward and the Neo-Tethys back-arc ocean basin to begin to expand. At this time, the northern margin of India became the only source of Jurassic strata in the study area.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P542

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