本文選題：大地電磁測深 + 深部電性結(jié)構(gòu)��； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：青藏高原自形成以來,由南至北形成了喜馬拉雅地體,雅魯藏布江縫合帶,拉薩-岡底斯地體,班公—怒江縫合帶,羌塘地體等地質(zhì)單元及界線。印度板塊和亞歐板塊兩大板塊的碰撞對于縫合帶的形成和地體的演化有著重要的意義。本文依托項目“岡底斯大地電磁剖面調(diào)查與巖石圈電性結(jié)構(gòu)研究”,選擇主要研究區(qū)域為雅魯藏布江縫合帶以北、班公-怒江縫合以南的岡底斯地體。設(shè)計一條穿過雅魯藏布江縫合帶和班公-怒江縫合帶的大地電磁測深剖面,對采集的大地電磁數(shù)據(jù)采用先進的處理方法,分析數(shù)據(jù)點的二維偏離度,磁感應(yīng)矢量和相位張量分解等流程后,進行區(qū)域內(nèi)的二維反演和三維反演,獲得了岡底斯地體可靠的深部電性結(jié)構(gòu)模型。該模型表現(xiàn)出剖面整體具有的特征為:垂直分層,水平分塊。研究區(qū)電性結(jié)構(gòu)模型由淺到深可分為三個電性層:第一層以不連續(xù)的高阻體為主,平均埋深約20km-30km。第二層為在中下地殼由雅魯藏布江縫合帶開始存在規(guī)模較大的北傾高導(dǎo)層,由南至北厚度逐漸增大,班公-怒江縫合帶南側(cè)高導(dǎo)體有延伸至上地幔的趨勢。第三層下地殼至上地幔則主要為高阻體。根據(jù)電性結(jié)構(gòu)模型電性梯度帶和高導(dǎo)層的特征,結(jié)合地質(zhì)資料劃分了地質(zhì)單元。通過電性結(jié)構(gòu)模型的特征對喜馬拉雅地體、岡底斯地體和羌塘地體的深部結(jié)構(gòu)特征進行了分析與說明。將500線和剖面的三維反演結(jié)果進行拼合得出結(jié)論:班公-怒江縫合帶南側(cè)東西向的電性結(jié)構(gòu)相一致,說明在岡底斯地體,高阻體和高導(dǎo)層具有東西向的連通性。岡底斯上地殼出現(xiàn)的高阻層,可能是岡底斯大規(guī)模淺層火成巖的表現(xiàn),與前期大規(guī)模的巖漿運動有關(guān)。在班公-怒江縫合帶南側(cè)存在下沿深度較深的高阻體,推測可能是在發(fā)生巖漿活動后的冷卻作用形成大規(guī)模的巖體。高阻體下存在連續(xù)高導(dǎo)層,可能是水流體和熔融體的共同作用的結(jié)果。由于羌塘地體高導(dǎo)層減薄且電阻率值減小,對于動力學(xué)模型探討,推測印度-亞歐板塊相向“雙向俯沖”,俯沖前緣位置在班公怒江縫合帶以南。
[Abstract]:Since the Qinghai-Tibet Plateau was formed, the Himalayan terrane, Yalu Zangbo River suture zone, Lhasa Gangdis terrane, Bangong-Nujiang suture zone, Qiangtang terrane and so on have been formed from the south to the north. The collision between the Indian plate and the Eurasian plate plays an important role in the formation of suture zone and the evolution of terrane. Based on the project "investigation of magnetotelluric profile and electrical structure of lithosphere", this paper selects the Gangdis terrane north of the Yarlung Zangbo River suture belt and south of the Bangong-Nujiang River suture. A magnetotelluric sounding profile passing through the Yalu Zangbo suture zone and the Bangong- Nujiang suture zone is designed. The advanced processing method is used to analyze the two-dimensional deviation of the data points. After the flow of magnetic induction vector and phase Zhang Liang decomposition, 2D and 3D inversion in the region are carried out, and a reliable deep electrical structure model of Gangdis terrane is obtained. The characteristics of the model are vertical stratification and horizontal partitioning. The electrical structure model of the study area can be divided into three layers from shallow to deep. The first layer is composed of discontinuous high resistive bodies with an average buried depth of about 20km-30km. In the second layer, there is a large northerly high conductivity layer in the middle and lower crust from the Yalu Zangbo River suture belt, and the thickness from south to north increases gradually, and the high conductors in the southern side of the Bangong-Nujiang suture belt tend to extend to the upper mantle. The third lower crust and upper mantle are mainly high resistivity bodies. According to the characteristics of the electrical gradient zone and the high conductivity layer of the electrical structure model, the geological units are divided according to the geological data. The deep structural characteristics of Himalayan, Gangdis and Qiangtang terrains are analyzed and explained by the characteristics of electrical structural models. Combining the three dimensional inversion results of 500 lines and sections, it is concluded that the electric structure of the south and west direction of Bangong- Nujiang suture belt is consistent, which indicates that the high resistivity body and the high conductance layer have east-west connectivity in the Gangdis terrane. The high resistivity layer in the upper crust of Gangdis may be the manifestation of the large scale shallow igneous rocks in Gangdis, which is related to the large-scale magmatic movement in the early stage. In the south of Bangong- Nujiang suture belt, there are deep and high resistivity bodies along the lower side of the suture zone, which suggests that the cooling process after magmatic activity may form a large scale rock mass. The existence of a continuous high conductivity layer under high resistivity may be the result of the interaction between water fluid and molten body. Due to the thinning of the height conductance and the decrease of resistivity in Qiangtang, it is inferred that the India-Eurasian plate faces "bidirectional subduction" and the leading position of the subduction is south of the Bangong Nujiang suture zone.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P631.325

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