本文選題：拉薩地塊 + 鋯石年代學(xué)　； 參考：《中國(guó)地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：本研究對(duì)拉薩地塊北部申扎地區(qū)進(jìn)行研究,通過(guò)野外調(diào)研,巖相學(xué)觀察,Gazzi-Dickinson顆粒統(tǒng)計(jì),鋯石年代學(xué)研究,對(duì)研究區(qū)從晚古生代到中生代的若干地質(zhì)問(wèn)題形成新的認(rèn)識(shí)。早白堊世的昂杰組砂巖中碎屑鋯石年齡分布,以及巖相學(xué)研究結(jié)果,揭示了二疊紀(jì)時(shí)期拉薩地塊應(yīng)處于印度岡瓦納北緣,接受特提斯域的物質(zhì)沉積。拉薩地塊北部三疊系沉積范圍很小。研究區(qū)內(nèi)的晚三疊世多布日組的碎屑鋯石年齡分布與拉薩地塊中北部的古生代地層的鋯石年齡分布相似。結(jié)合巖相學(xué)顆粒統(tǒng)計(jì)結(jié)果,認(rèn)為其物源主要為古生代地層的再旋回物質(zhì),很少有北部羌塘地塊和拉薩地塊南部的二疊紀(jì)-三疊紀(jì)時(shí)期的松多造山帶和巖漿活動(dòng)的物質(zhì)。永珠蛇綠巖帶屬于獅泉河-永珠-納木錯(cuò)蛇綠巖帶的一部分。認(rèn)為其代表一個(gè)拉薩地塊內(nèi)部的縫合帶,是一系列弧后或弧間洋盆的殘余。永珠蛇綠巖的席狀巖墻群中一個(gè)輝長(zhǎng)巖樣品27個(gè)測(cè)點(diǎn)得到平均年齡153±2.3 Ma,指示申扎地區(qū)這一洋盆在晚侏羅世時(shí)期還沒(méi)有閉合。申扎地區(qū)晚侏羅-早白堊時(shí)期的日拉組沉積覆蓋在永珠蛇綠巖之上,沉積過(guò)程有受到斷層活動(dòng)影響的跡象。早白堊世時(shí)期,研究區(qū)有很多巖漿活動(dòng)。區(qū)內(nèi)采集的鉀長(zhǎng)花崗巖,安山玢巖,花崗斑巖,以及白堊系中的火山巖樣品的鋯石U-Pb定年結(jié)果顯示它們都具有早白堊世年齡。它們應(yīng)該與拉薩地塊北部普遍發(fā)育的早白堊世巖漿活動(dòng)具有相同的成因背景。申扎地區(qū)沿著獅泉河-納木錯(cuò)混雜巖帶,發(fā)育有很多自南向北逆沖為主的斷層,它們將南部的古生代地層以及蛇綠巖逆沖到北部的白堊系之上。通過(guò)野外構(gòu)造關(guān)系,年代學(xué)研究,沉積盆地物源分析,結(jié)合相鄰區(qū)域的40Ar-39Ar熱年代學(xué)研究的報(bào)道,本研究認(rèn)為它們的活動(dòng)最早開(kāi)始于早白堊世早期,并持續(xù)作用到晚白堊世。這一斷層系統(tǒng)北部的早白堊世砂巖的碎屑鋯石年齡分布指示它們的物源主要為斷層系統(tǒng)南部的古生代地層再旋回物質(zhì),以及拉薩地塊北部的巖漿活動(dòng)物質(zhì)。這一沉積過(guò)程可能受到申扎地區(qū)斷層系統(tǒng)的控制。本研究提出申扎地區(qū)的格仁錯(cuò)-納木錯(cuò)逆沖斷層系統(tǒng)是沿著獅泉河-納木錯(cuò)混雜巖帶代表的先存的構(gòu)造薄弱帶發(fā)育,它形成于北部拉薩-羌塘碰撞和南部可能存在的新特提斯洋向北平板俯沖的大地構(gòu)造背景中。
[Abstract]:In this study, the study of Xainza area in the northern part of Lhasa block, through field investigation, petrographic observation, Gazzi-Dickinson particle statistics and zircon geochronology, a new understanding of some geological problems from Late Palaeozoic to Mesozoic in the study area. The age distribution of detrital zircons in the sandstone of the early Cretaceous Angjie formation and petrographic study It is revealed that the Lhasa massif in the Permian period should be in the northern margin of the Gondwana, India, to accept the material deposits in the Tethys domain. The sedimentary range of the Triassic in the northern part of the Lhasa massif is very small. The age distribution of the detrital zircons in the late three fold group of the study area is similar to the zircon age distribution of the Paleozoic strata in the northern part of the Lhasa massif. According to the statistical results of the phase, it is believed that its source is mainly a re cyclic substance in the Paleozoic strata, and there are few substances in the northern Qiangtang block and the southern part of the Lhasa massif in the Permian Triassic period of the pine multi orogenic belt and magmatism. The suture zone within the Lhasa massif is a series of remnants of the post arc or interarc oceanic basin. The average age of 27 samples of a gabbro sample in the permanent ophiolite group was 153 + 2.3 Ma, indicating that the Xainza basin was not closed during the late Jurassic period. The late Jurassic and Cretaceous period of the Xainza region was deposited in the Naga group. The deposition process is above the perpetual ophiolite, and the deposition process has a sign of the influence of fault activity. In the early Cretaceous period, there were many magmatic activities in the study area. The U-Pb dating results of the zircon from the samples collected in the region and in the volcanic rocks in the Cretaceous show that they all have early Cretaceous age. They should be in the early Cretaceous age. The early Cretaceous magmatic activity, which is widely developed in the northern part of the Lhasa massif, has the same genetic background. The Xainza area along the Shiquan River Nam Co melange belt developed many faults mainly from the south to the north. They thrust the Paleozoic strata in the South and the ophiolites back to the northern Cretaceous system. The study, the source analysis of sedimentary basins, and the report on the 40Ar-39Ar thermal chronology of adjacent regions, this study believed that their activities first began in the early Cretaceous and continued to be in the late Cretaceous. The age distribution of the detrital zircon of the early Cretaceous sandstone in the northern part of the fault system indicates that their source is mainly a fault. The Paleozoic stratigraphic re gyratory substance in the southern part of the system and the magmatic activity in the northern part of the Lhasa massif may be controlled by the fault system in the Xainza region. This study suggests that the Xainza area's green fault Nam Co thrust fault system is the first deposited weak tectonic belt represented by the Shiquan River Nam Co melange belt. It was formed in the tectonic setting of the collision between the northern Lhasa Qiangtang and the north facing subduction of the new Tethyan ocean in the south.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P534;P548

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