本文選題：大地電磁　切入點：電各向異性　出處：《中國地質(zhì)大學》2016年博士論文　論文類型：學位論文

【摘要】：近年來隨著地球物理觀測技術(shù)和理論方法的發(fā)展,越來越多的研究表明地球介質(zhì)具有明顯的電各向異性特征。大地電磁法可以對整個巖石圈的電阻率進行成像,因而成為理解巖石圈的結(jié)構(gòu)、組成以及演化的主要手段之一為了研究西準噶爾巖石圈的電性結(jié)構(gòu),完成了穿越北東-南西向的達爾布特斷裂的三條大地電磁測深剖面。相位張量和感應矢量分析表明此區(qū)域地電結(jié)構(gòu)是3D且可能存在各向異性。對阻抗張量和傾子矢量數(shù)據(jù)集分別進行3D各向同性反演,得到了兩個極為不同的模型,說明沒有一個簡單的電各向同性模型可以同時解釋所有的大地電磁響應函數(shù)。根據(jù)1D各向異性以及2D、3D各向同性的反演結(jié)果,建立了一個各向異性的3D電阻率模型,其中包含位于達爾布特與克一烏斷裂之間、深度范圍為5-40公里的方位電各向異性地殼層(最小電阻率方向為東西向)以及一個方位電各向異性的巖石圈地幔(最小電阻率方向為北東20°)。這一各向異性電阻率模型明顯改善了反演中相位張量和感應矢量的擬合程度。推斷方位電各向異性地殼層為玄武質(zhì)海洋地殼在晚古生代對洋內(nèi)達爾布特島弧下俯沖的殘余物,板塊俯沖過程中發(fā)生脫水作用而產(chǎn)生大量的水,從而在板片和地幔楔內(nèi)產(chǎn)生大量的蛇紋巖化巖石。該殼內(nèi)電各向異性層的最小電阻率方向(近東西向)與海溝走向(-北東40°)的差異性可能是由于斜俯沖造成的。同時注意到,地殼各向異性層最小電阻率方向和海溝方向相對于巖石圈地幔最小電阻率方向(北東20°)分別有順時針70°和200的偏離,表明該區(qū)地殼的運動與其下伏的上地幔是解耦的。
[Abstract]:In recent years, with the development of geophysical observation techniques and theoretical methods, more and more studies show that the earth media has obvious characteristics of electrical anisotropy. Magnetotelluric method can image the resistivity of the whole lithosphere. Therefore, it has become one of the main means of understanding the structure, composition and evolution of the lithosphere in order to study the electrical structure of the lithosphere in West Junggar. Three magnetotelluric sounding profiles have been completed across the Dabut fault in the NE-S direction. Phase Zhang Liang and induction vector analysis show that the geoelectric structure in this area is 3D and may have anisotropy. The vector data sets are respectively used for 3D isotropic inversion. Two very different models are obtained, which show that no simple electroisotropic model can interpret all magnetotelluric response functions at the same time. An anisotropic 3D resistivity model is developed, which is located between the Darbout and Keyawu faults. An azimuthal anisotropic crustal layer with a depth of 5-40 km (the minimum resistivity direction is east-west) and a azimuthal anisotropic lithospheric mantle (the minimum resistivity direction is 20 擄N E). This anisotropic resistivity is obtained. The model obviously improves the fitting degree of phase Zhang Liang and induction vector in inversion. It is inferred that the azimuth anisotropic crust is the residuals of Black Tortoise oceanic crust subducting under the arc of Darbout Island in the late Paleozoic. A lot of water is produced by dehydration during plate subduction. As a result, a large number of serpentinized rocks are produced in the plate and mantle wedge. The difference between the minimum resistivity direction (near east-west) of the anisotropic layer in the crust and the trench strike (40 擄NNE) may be caused by oblique subduction. The minimum resistivity direction and trench direction of the anisotropic layer of the crust deviate from the minimum resistivity direction of lithospheric mantle (20 擄N E) by 70 擄clockwise and 200 擄respectively, indicating that the crustal movement in this area is decoupled from the underlying upper mantle.
【學位授予單位】：中國地質(zhì)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：P631.3

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