本文選題：班公湖—怒江縫合帶 + 改則地區(qū)　； 參考：《成都理工大學》2015年碩士論文

【摘要】：班公湖—怒江縫合帶是青藏高原內(nèi)部一條極為重要的地質(zhì)界線,分隔了兩側(cè)的羌塘地塊和拉薩地塊,并保留著中、新特提斯洋演化的重要信息。目前對班公湖-怒江洋盆的性質(zhì)、演化模式、俯沖極性和閉合機制等關(guān)鍵的大地構(gòu)造問題都存在著激烈爭論,這直接影響了對班公湖—怒江縫合帶構(gòu)造演化的理解。本文通過1:5萬、1:1萬地質(zhì)填圖及野外露頭構(gòu)造詳細解析,對研究區(qū)構(gòu)造期次進行劃分。在已有的地質(zhì)調(diào)查和研究基礎之上,以巖石學、巖石地球化學為基礎,以同位素年代學研究為主線,采用地質(zhì)學、地球化學、同位素年代學等多學科結(jié)合的研究方法,查明班公湖—怒江縫合帶中西段改則地區(qū)的火山、巖漿巖的形成時代、構(gòu)造環(huán)境,依此確定洋盆不同階段的存在時限,演化特征。初步研究表明:(1)由于經(jīng)歷班怒洋長期復雜的開合演化并遭受后碰撞期火山巖斷陷盆地疊加以及印-亞大陸碰撞高原隆升期強烈的構(gòu)造改造,展現(xiàn)出區(qū)塊分隔、南北分帶、東西分段和垂向分層的構(gòu)造格局。研究區(qū)處于泛華夏大陸晚古生代羌塘-三江造山系的班公湖-雙湖-怒江-昌寧對接帶(I級大地構(gòu)造單元)南側(cè)。II級構(gòu)造單元劃分以打格弄-扎茬亞-尼布斷裂為界,北部屬南羌塘增生弧盆地(II),南歸班公湖-怒江洋結(jié)合帶。(2)研究區(qū)主要經(jīng)歷了三期構(gòu)造變形:第一期變形(D1)與班公湖—怒江縫合帶同造山擠壓事件有關(guān),主要表現(xiàn)為近S-N向構(gòu)造擠壓作用力下(包含NW-SE向)形成了區(qū)域上近E-W向構(gòu)造帶,以發(fā)育透入性的S1面理為標志。第二期構(gòu)造變形(D2)與晚造山期近N-S向擠壓左旋擠壓事件相關(guān),主要表現(xiàn)以蛇綠巖帶中S1左旋剪切面理以及沙木羅組(J3K1s)中不對稱傾豎褶皺和斜歪褶皺為標志,形成了區(qū)域性的軸面劈理S2。第三期構(gòu)造變形(D3)與后造山期近N-S向(包含NE-SW向)右旋擠壓事件相關(guān),主要表現(xiàn)以以蛇綠巖帶中S2右旋剪切面理、色哇組右旋剪切面理、日干配錯組中右旋走滑背景下的局部左旋不對稱傾豎褶皺以及去申拉組中近東西向與近SN向?qū)捑忨薨櫙B加以及褶皺軸向的向南偏轉(zhuǎn)為標志,在色哇組中形成了軸面劈理S2。(3)綜合研究區(qū)的地層學、巖石學、地球化學、年代學和構(gòu)造地質(zhì)記錄分析,研究區(qū)構(gòu)造地質(zhì)演化經(jīng)歷了4個演化階段:①班公湖-怒江洋擴張階段(P-T1),通過對第I類高壓榴輝巖的研究結(jié)果表明班公湖—怒江洋盆的裂解時間至少可以提前至晚二疊世—三疊紀;②班公湖-怒江洋俯沖和高壓變質(zhì)巖折返階段(T2-J2),通過對第II類高壓榴輝巖的研究結(jié)果表明至少在早侏羅世班公湖—怒江洋盆已經(jīng)開始俯沖,將俯沖的下限時間延至早侏羅世;③班公湖-怒江洋閉合和碰撞造山階段(J3-K1);④后碰撞階段(K1至今),通過對去申拉組兩件火山巖進行同位素U-Pb年齡分析表明其加權(quán)平均年齡為106.7±0.7 Ma和106.0±0.8 Ma,時代為早白堊世晚期,形成的構(gòu)造環(huán)境為大陸板內(nèi)裂谷,代表洋盆碰撞后陸內(nèi)伸展階段形成的火山巖。
[Abstract]:The ban Gong Lake Nu River suture zone is a very important geological boundary inside the Qinghai Tibet Plateau, which separates the Qiangtang and Lhasa blocks on both sides, and maintains important information on the evolution of the new Tethys ocean in the middle of the Qinghai Tibet Plateau. At present, the key geodetic problems such as the nature, evolution model, subduction polarity and closed mechanism of the ban Gong Hu Nu River oceanic basin are all stored. In the intense debate, this directly affects the understanding of the tectonic evolution of the ban Gong Lake - Nu River suture zone. This paper, through the detailed analysis of the 1:5 million, 1:1 million geological mapping and outcrop structure, divides the tectonic period of the study area. Based on the existing geological survey and research, it is based on petrology, rock geochemistry and isotopic years. As the main line of study, the study methods of geology, geochemistry and isotopic chronology have been used to find out the volcano in the region of the middle and western section of the Nu River suture zone, the age of the formation of magmatic rocks, the tectonic environment, and the time limit and the evolution characteristics of the different stages of the oceanic basin. The long and complex evolution of the banyan ocean and the tectonic transformation of the volcanic rock fault basin in the post collision period and the uplift period of the collision plateau of India and Asia, show the structural pattern of the partition, the South and the north, the East and the West and the vertical stratification. The study area is in the Bangong of the Qiangtang Qiangtang Sanjiang orogenic system of the late Paleozoic in Pan Hua Xia continent. The.II level tectonic units on the south side of the lake double Lake Nu River Changning docking zone (I grade tectonic unit) are divided on the southern side of the TG Nong Zhan Nibu Nibu fault, the northern part of the South Qiangtang accretive arc basin (II), the Bangong Lake and the Nu River ocean zone in the south. (2) the study area has undergone three stages of deformation: the first phase deformation (D1) and the Bangong Lake Nu River suture zone Related to the orogenic extrusion event, it is mainly shown that the near S-N tectonic compression force (including NW-SE direction) has formed a regional near E-W direction structure zone, which is marked by the development of the permeable S1 surface texture. The second phase tectonic deformation (D2) is related to the late orogenic period near N-S compression left lateral extrusion event, mainly manifested by the S1 left-handed shear surface in the ophiolite belt. As well as the asymmetrical tilting fold and skew fold in the J3K1s, the regional axial cleavage S2. third phase structural deformation (D3) is related to the near N-S direction (including NE-SW direction) dextral extrusion events in the post orogenic period, mainly manifested in the S2 right rotation shear surface in the ophiolitic zone, the dextral shear surface of the Shah wow group and the diurnal error group. The local left-hand asymmetrical vertical folds in the middle dextral strike slip background and the superposition of the near east-west and near SN wide slow folds in the Deshen group and the southward deflection of the fold axis are marked. The stratigraphy, petrology, geochemistry, geochronology, geochronology, geochronology, geochronology, and tectonic geological records are formed in the shaxa group in the Shah wow group. The geological evolution of the study area has undergone 4 stages of evolution: (1) the bandgong Lake Nu River ocean expansion phase (P-T1). The results of the study of class I high pressure eclogite show that the splitting time of the bandgong Lake - Nu River ocean basin can be at least to the Late Permian Triassic Period; (2) the bandgong Lake - Wrath Jiang Yang subduction and the high pressure metamorphic rock reentry phase (T2-J2). The results of the study on the type II high pressure eclogite show that at least the early Jurassic band Gong Lake Nu River ocean basin has begun subduction, extending the subduction time to the early Jurassic; (3) the ban Gong Lake Nu River ocean closure and the collision orogenic stage (J3-K1); (4) the post collision stage (K1 today), through the isotopic U-Pb of two volcanic rocks in the Deshen group The age analysis shows that the weighted average age is 106.7 + 0.7 Ma and 106 + 0.8 Ma, and the era is late Early Cretaceous, the tectonic environment formed in the continental plate rift, representing the volcanic rocks formed during the intracontinental extension of the ocean basin.
【學位授予單位】：成都理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P548

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