發(fā)布時(shí)間：2018-05-04 23:23

  本文選題：碰撞時(shí)限 + 構(gòu)造縮短量��； 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：印度板塊與歐亞板塊碰撞是新生代以來地質(zhì)歷史上重要地質(zhì)事件之一。碰撞導(dǎo)致了喜馬拉雅造山帶和青藏高原的形成,碰撞及其之后的高原隆升強(qiáng)烈影響了青藏高原及其周邊塊體的構(gòu)造演化;同時(shí),碰撞還改變了青藏高原及周邊水系分布與流向,對(duì)亞洲甚至全球氣候都產(chǎn)生了巨大的影響。對(duì)印度與歐亞板塊碰撞過程研究的主要問題之一在于精確限定其碰撞的初始時(shí)間和產(chǎn)生的構(gòu)造縮短量。地學(xué)界廣泛接受的印度與歐亞板塊初始碰撞時(shí)間為~55Ma,碰撞后產(chǎn)生的構(gòu)造縮短量為~1000km;但是對(duì)這一問題也存在很大的爭(zhēng)議。印度與歐亞板塊碰撞為近南北向的陸陸碰撞,那么碰撞最直接的證據(jù)就是縫合帶兩側(cè)塊體的古緯度的重疊。實(shí)踐和研究證明古地磁學(xué)能定量地約束板塊的邊界及其演化歷史,精確限定板塊的古緯度,是制約板塊碰撞時(shí)限、碰撞地點(diǎn)和碰撞模式的最理想方法之一。本論文選擇拉薩地塊林周盆地晚白堊世紅層-火山巖序列,開展同位素年代學(xué)和構(gòu)造古地磁學(xué)研究,從構(gòu)造古地磁學(xué)的角度探討印度與歐亞板塊碰撞的時(shí)間和產(chǎn)生的構(gòu)造縮短量,主要得出以下結(jié)論:(1)古地磁采樣地層(上白堊統(tǒng)設(shè)興組地層)的時(shí)代為69.75Ma-73.75Ma。(2)通過對(duì)比林周盆地晚白堊世沉積巖和火山巖古地磁結(jié)果,認(rèn)為研究區(qū)區(qū)沉積巖記錄的古地磁場(chǎng)磁傾角并不存在顯著的磁傾角偏低現(xiàn)象。采樣剖面獲得的晚白堊世古地磁結(jié)果具有正極性和反極性兩種極性,其特征剩磁方向?yàn)?Dg=13.2°,Ig=31.6°,k=36.4,α95=5.3°,地層校正后Ds=0.5°,Is=20.2°,k=25.5,α95=6.4°;對(duì)應(yīng)的古地磁極位置為:70.5°N,269.6°E,A95=4.9°,古緯度為plat=10.4°N。(3)通過對(duì)比已有的古地磁數(shù)據(jù),我們認(rèn)為拉薩地塊在晚白堊至古近紀(jì)一直處于北緯11°N-15°N左右的低緯度位置,并未發(fā)生明顯的緯向運(yùn)動(dòng)。據(jù)此推算印度與歐亞板塊初始碰撞時(shí)間為47Ma-54Ma。(4)通過對(duì)比本次研究得出的拉薩地塊的古緯度實(shí)測(cè)值與拉薩地塊和喜馬拉雅地塊古緯度期望值,認(rèn)為約70Ma以來,拉薩塊體與穩(wěn)定歐亞大陸之間發(fā)生了1300±450km的構(gòu)造縮短。
[Abstract]:The collision between the Indian plate and the Eurasian plate is one of the important geological events in the Cenozoic geological history. The collision resulted in the formation of the Himalayan orogenic belt and the Qinghai-Tibet Plateau, and the collision and the subsequent uplift of the plateau strongly affected the tectonic evolution of the Qinghai-Tibet Plateau and its surrounding blocks, and at the same time, the collision also changed the distribution and flow direction of the Qinghai-Tibet Plateau and its surrounding water system. It has had a huge impact on Asia and even on the global climate. One of the main problems in the study of the collision process between India and Eurasia is to precisely define the initial time and tectonic shortening of the collision. It is widely accepted in geoscience that the initial collision time between India and Eurasia plate is 55 Ma, and the tectonic shortening caused by collision is 1000 km, but this problem is also controversial. The collision between India and Eurasia is a continental collision near the north and south. The most direct evidence of the collision is the overlap of paleolatitudes of the blocks on both sides of the suture belt. It is proved by practice and research that paleomagnetism can quantitatively constrain the boundary of plate and its evolution history, and precisely define the paleolatitude of plate. It is one of the most ideal methods to restrict the time limit of plate collision, collision location and collision model. In this paper, isotopic chronology and tectonic paleomagnetism are carried out in the late Cretaceous red beds and volcanic rock sequences in Linzhou Basin, Lhasa block. From the perspective of tectonic paleomagnetism, the time and tectonic shortening of the collision between India and Eurasia plate are discussed. The main conclusions are as follows: (1) paleomagnetic sampling stratigraphy (upper Cretaceous formation) is 69.75 Ma-73.75 Ma.-2) by contrasting paleomagnetic results of late Cretaceous sedimentary rocks and volcanic rocks in Linzhou Basin. It is considered that the paleomagnetic field magnetic dip angle recorded in sedimentary rocks of the study area does not have a significant phenomenon of low magnetic dip angle. The paleomagnetic results of the late Cretaceous obtained from the sampling section have two polarities, namely, positive polarity and antipolarity. The remanent magnetic direction of the paleomagnetic field is: 1 DG 13.2 擄IgA 36.4 擄, 偽 955.3 擄, Ds=0.5 擄Isa 20.2 擄KG 25.5, 偽 956.4 擄; the corresponding paleomagnetic pole position is: 70.5 擄Nu 269.6 擄EKA 954.9 擄, and paleolatitude is plat=10.4 擄N. 3. The paleomagnetic data are compared by comparing the available paleomagnetic data. We think that the Lhasa block has been in the low latitude of 11 擄N-15 擄N from late Cretaceous to Paleogene, and there is no obvious zonal movement. The initial collision time between India and Eurasia plate is estimated to be 47 Ma-54 Ma. 4) by comparing the paleolatitude of Lhasa block with the expected value of paleo latitude of Lhasa block and Himalayan block, it is considered that since 70Ma, The tectonic shortening of 1300 鹵450km occurred between Lhasa block and stable Eurasia.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P318.4;P531

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本文編號(hào)：1845146