本文選題：大地電磁測深 + 青藏高原西部�。� 參考：《中國地質(zhì)大學(北京)》2017年碩士論文

【摘要】：青藏高原作為歐亞大陸最醒目的地貌單元,是印度大陸與亞洲大陸碰撞的產(chǎn)物;由于印度洋中脊持續(xù)擴張使印度板塊巖石圈向北楔入到亞洲大陸之下,擠壓增厚形成了青藏高原,它具有復雜而獨特的巨厚地殼和巖石圈結(jié)構(gòu)。青藏高原西部地區(qū)是印度洋向北擴張擠壓的應(yīng)力集聚帶,是陸-陸碰撞造山帶的典型地區(qū)之一,它擁有更為復雜的地質(zhì)構(gòu)造與物質(zhì)組成,對此區(qū)域進行詳細的研究對于從整體上認識青藏高原的一系列地學問題起著關(guān)鍵的作用,因此,青藏高原西部地區(qū)近些年來已經(jīng)成為地學研究者關(guān)注的熱點區(qū)域。論文以“深部探測技術(shù)與實驗研究”專項(SinoProbe,2008-2012)子課題“大陸電磁學參數(shù)標準網(wǎng)實驗研究(SinoProbe-01)”在青藏高原西部地區(qū)沿80° E、81°E、82° E三條經(jīng)線采集得到的14個“標準點”,共計148個大地電磁測深點作為原始數(shù)據(jù)資料,對數(shù)據(jù)進行了處理、分析及反演;最終得到了研究區(qū)的二維及三維電性結(jié)構(gòu)模型。二維反演模型和三維反演切片對應(yīng)良好,說明得到的電性結(jié)構(gòu)模型可信度較高。電性結(jié)構(gòu)模型顯示,研究區(qū)上地殼以高阻為主,在縫合帶及斷裂帶處,有垂向延伸的低阻帶切割高阻層;中、下地殼內(nèi)有大規(guī)模高導層,雅魯藏布江縫合帶處高導層厚度小、埋深淺,拉薩-岡底斯地體內(nèi)高導層的厚度和底界面深度向北增大,在班公湖-怒江縫合帶附近下方高導層厚度最大,底界面已經(jīng)達到上地幔深度,羌塘地體高導層厚度整體較大;高導層之下為高阻層,但受剖面的有效深度限制,并不能判定該層的厚度。研究認為,印度板塊巖石圈向青藏高原下方俯沖產(chǎn)生的熱效應(yīng),使俯沖接觸面上的巖石發(fā)生了部分熔融,熔融的巖石電阻率降低;另外,熔融的巖石會析出水分,水分在壓力作用下會向上方運移;因此在部分熔融和含水流體的共同作用下導致了研究區(qū)內(nèi)喜馬拉雅地體和拉薩-岡底斯地體下方高導層的出現(xiàn)。羌塘地體內(nèi)的高導層的成因主要是因為幔源物質(zhì)上涌,導致殼內(nèi)巖石發(fā)生部分熔融,形成了高導層。研究認為,印度巖石圈已經(jīng)俯沖進入青藏高原之下,在青藏高原西部,其俯沖前緣沒有越過班公湖-怒江縫合帶,俯沖的印度巖石圈在班公湖-怒江縫合帶下方下插進入上地幔。
[Abstract]:The Qinghai-Xizang Plateau, as the most prominent geomorphological unit in Eurasia, is the result of the collision between the Indian continent and the Asian continent. Due to the continuous expansion of the mid-Indian Ocean ridge, the lithosphere of the Indian plate wedge north into the Asian continent. The compression thickening forms the Qinghai-Xizang Plateau, which has a complex and unique structure of the extremely thick crust and lithosphere. The western part of the Qinghai-Xizang Plateau is a typical region of the continental and continental collision orogenic belt, which is characterized by a more complicated geological structure and material composition. The detailed study of this region plays a key role in understanding a series of geoscience problems in the Tibetan Plateau as a whole. Therefore, the western region of the Tibetan Plateau has become a hot spot of geoscience researchers in recent years. In this paper, 14 "standard points" have been collected in the western part of the Qinghai-Xizang Plateau along three longitude lines of 80 擄E ~ (81 擄) and 82 擄E, based on "Sino Probe-01", a sub-project of "SinoProbe-2008-2012", a subproject of "Sino Probe-01", which is a special project of "deep exploration technology and experimental research" ("Sino Probe-01"). A total of 148 magnetotelluric sounding points were used as raw data to process, analyze and inverse the data. Finally, the two-dimensional and three-dimensional electrical structure models of the study area were obtained. Two dimensional inversion model and three dimensional inversion slice correspond well, which indicates that the obtained electrical structure model has high reliability. The electrical structural model shows that the upper crust of the study area is dominated by high resistivity, and there is a vertical extension of low resistivity zone in the suture zone and fault zone to cut the high resistivity layer, and in the middle and lower crust there is a large scale high conductivity layer, and the thickness of the high conductivity layer in the Yalu Zangbo suture zone is small. The depth of the buried layer is shallow, the thickness of the high conductivity layer and the depth of the bottom interface of the Lhasa-Gangdis area increase northward, and the thickness of the high conductivity layer near the Bangong Lake-Nujiang suture zone is the largest, and the bottom interface has reached the depth of the upper mantle. The thickness of the high conductivity layer in Qiangtang is relatively large, but the thickness of the high conductivity layer is limited by the effective depth of the section. It is believed that the thermal effect of the subduction of the Indian plate lithosphere beneath the Qinghai-Xizang Plateau has partially melted the rocks on the subduction contact surface and reduced the resistivity of the melted rocks. In addition, the molten rocks will precipitate water. Water will move upward under pressure, so the combination of partial melting and water-bearing fluids leads to the appearance of high conductivities beneath the Himalayan terrane and Lhasa Gangdis terrane in the study area. The formation of the high conductivity layer in Qiangtang is mainly due to the upwelling of mantle material, which leads to partial melting of the rocks in the crust and the formation of the high conductivity layer. The study shows that the Indian lithosphere has already subducted into the Tibetan Plateau, and in the western part of the Tibetan Plateau, the leading subduction front has not crossed the Bangonghu Lake-Nujiang suture zone. The subducted Indian lithosphere enters the upper mantle below the Bangong Lake-Nujiang suture zone.
【學位授予單位】：中國地質(zhì)大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P631.3;P313

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