Understanding geophysical imprints of suture zones: Development of 2D constraint inversion for electrical anisotropy

了解缝合带的地球物理印记：电各向异性二维约束反演的发展

• 批准号: 44028036
• 负责人: Privatdozentin Dr. Ute Weckmann
• 金额: --
• 依托单位: Sektion 2.2: Geophysikalische Abbildung des Untergrunds
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/44028036?language=en
• 关键词: Understanding; geophysical; imprints; suture; zones

Between 2004 - 2006 several high resolution magnetotelluric (MT) experiments along a 650 km long continental scale transect imaged various structural details in the upper and lower crust of South African mobile belts and associated suture zones. With isotropic 2D inversion the main regional features can be explained: (i) the transition of the unexpectedly conductive Namaqua-Natal Mobile Belt (NNMB) into the highly resistive Kaapvaal Craton, which is located 70 km farther southwest than expected, (ii) a sub-vertical zone of high electrical conductivity in the NNMB basement, likely an image of a large crustal scale shear zone, (iii) an extensive shallow sub-horizontal high conductivity layer which correlates with a prominent black shale horizon in the Karoo Basin, (iv) a previously unknown conductive synformal structure in the NNMB basement in 10 - 25 km depth , and (v) the conductive deep basins of the Cape Fold Belt (CFB), which (vi) are sandwiched between the resistive, intensely folded mountain ranges. Some confined areas along the profile exhibit three-dimensional (3D) effects in the MT impedance tensor, likely caused by electrical anisotropy. Modelling and quantifying electrical anisotropy in suture zones has been one of the major goals of my previous application and was part of a PhD project. Unfortunately, the PhD student got severely ill and the position could only be filled again in October 2008. The new PhD student is currently working towards anisotropic inversion. With this proposal we intend to (i) model the effects of electrical anisotropy in the MT data which are currently not explained, (ii) quantify the electrical anisotropy to derive structural details of the associated fault systems and (iii) derive a more complete image of the complicated evolution of Gondwana’s accretion processes preserved in the lithosphere, by putting together the regional information and structural details of anisotropic zones.

2004 - 2006年期间，几个高分辨率大地电磁（MT）实验沿着650公里长的大陆尺度断面成像的各种结构细节在上，下地壳的南非移动的带和相关的缝合带。利用各向同性2D反演，可以解释主要的区域特征：㈠纳马夸-纳塔尔移动的带（NNMB）出人意料地具有导电性，它向高电阻的Kaapvaal岩带过渡，Kaapvaal岩带位于比预期的西南方向远70公里处，㈡ NNMB基底中的一个近垂直的高导电性带，可能是一个大地壳规模剪切带的图像，（iii）与卡鲁盆地突出的黑色页岩层相关的广泛的浅的近水平高导电性层，（iv）NNMB基底中10 - 25 km深度的先前未知的导电性同形结构，以及（v）开普褶皱带（CFB）的导电性深盆地，其（vi）夹在电阻性的、强烈折叠的山脉之间。沿剖面沿着的一些受限区域在MT阻抗张量中表现出三维（3D）效应，这可能是由电各向异性引起的。模拟和量化缝合带中的电各向异性一直是我之前申请的主要目标之一，也是博士项目的一部分。不幸的是，博士生得了重病，该职位只能在2008年10月再次填补。这位新的博士生目前正在研究各向异性反演。有了这个建议，我们打算（一）模拟的MT数据，目前没有解释的电各向异性的影响，（二）量化的电各向异性，以获得相关的断层系统的结构细节和（iii）获得一个更完整的图像冈瓦纳大陆的增生过程中保存在岩石圈的复杂演变，把区域信息和各向异性带的结构细节。

项目成果

Magnetotelluric image linked to surface geology across the Cape Fold Belt, South Africa

与南非开普褶皱带地表地质相关的大地电磁图像

• DOI: 10.1111/j.1365-3121.2011.01054.x
• 发表时间: 2012
• 期刊: Terra Nova
• 影响因子: 2.4
• 作者: Weckmann;Ritter;Tietze;de Wit
• 通讯作者: de Wit

Simple models for the Beattie Magnetic Anomaly in South Africa

• DOI: 10.1016/j.tecto.2008.11.027
• 发表时间: 2009-11
• 期刊: Tectonophysics
• 影响因子: 2.9
• 作者: Y. Quesnel;U. Weckmann;O. Ritter;J. Stankiewicz;V. Lesur;M. Mandea;B. Langlais;B. Langlais;C. Sotin;A. Galdeano