Constrained modelling of electromagnetic and potential field data to investigate the Walvis Ridge magmatism and its interaction with the Kaoko Mobile Belt, Namibia.

对电磁场和势场数据进行约束建模，以研究沃尔维斯海岭岩浆作用及其与纳米比亚 Kaoko 移动带的相互作用。

• 批准号: 243809540
• 负责人: Professor Dr. Oliver Ritter
• 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: Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/243809540?language=en
• 关键词: Constrained; modelling; electromagnetic; potential; field

Within the framework of an amphibian magnetotelluric experiment in 2011, the Walvis Ridge magmatism and its interaction with the Kaoko Mobile Belt in northern Namibia were investigated. For that purpose, magnetotelluric (MT) data were recorded at 167 land stations along a 140 km wide swath in northern Namibia and at 30 ocean bottom sites along a coast-parallel and a coast-perpendicular profile in the vicinity of the Walfis Ridge. Visual inspection as well as dimensionality analysis of the onshore MT data indicates complex three-dimensional (3D) subsurface structures across the Kaoko Belt. To construct a preliminary electrical conductivity section, we applied two-dimensional (2D) inversion to a sub-set of the data. The 2D inversion models show good correlation with surface geology and tectonic units. The Etendeka Flood Basalts appear as a deep reaching zones of high resistivity, while faulted and antiforms structures are highly conductive. Some of the features are unexpected, however, such as zones of high conductivity beneath the Congo Craton. The onset of the Congo Craton appears to be a well resolved feature in the gravity data while some of the high conductivity coincides spatially with magnetic anomalies. We therefore suggest using gravity and aeromagnetic data which are available from the Geological Survey of Namibia to obtain 2D and 3D potential field models. With this proposal, we intend to (i) model aeromagnetic and gravity data in the region of the MT swath using IGMAS+, (ii) constrain 2D and 3D MT models using the obtained potential field models, (iii) use seismic and seismological results obtained within the SPP SAMPLE (phase II) as additional constraints, (iv) elaborate empiricalrelations between electrical conductivity and magnetization (density) locally (based on fitting probability density functions) and (v) derive a consistent geological interpretation of the Kaoko Belt, its interaction with the Walvis Ridge and the transition to the Congo Craton on the basis of all availablegeophysical data.

在2011年两栖大地电磁试验的框架内，调查了纳米比亚北部的沃尔维斯山脊岩浆活动及其与Kaoko活动带的相互作用。为此目的，在纳米比亚北部一条140公里宽的狭长地带上的167个陆上观测站以及沃尔菲斯海脊附近沿海岸平行和海岸垂直剖面的30个海底站点记录了大地电磁数据。对陆上MT数据的目测检查和维度分析表明，考古带上存在复杂的三维(3D)地下结构。为了构建初步的电导率剖面，我们对数据的一个子集应用了二维(2D)反演。二维反演模型与地表地质和构造单元具有较好的相关性。Etendeka溢流玄武岩表现为高电阻率的深达带，而断层和逆形构造具有高导电性。然而，其中一些特征是意想不到的，例如刚果克拉通下方的高导电性区域。刚果克拉通的开始似乎是重力数据中一个很好分辨的特征，而一些高电导率与磁异常在空间上是一致的。因此，我们建议使用纳米比亚地质调查局提供的重力和航磁数据来获得2D和3D势场模型。根据这一建议，我们打算(I)使用IGMAS+对MT带状区域的航磁和重力数据进行模拟，(Ii)使用所获得的势场模型来约束2D和3D MT模型，(Iii)使用在SPP样本(第二阶段)内获得的地震和地震学结果作为附加约束，(Iv)在局部(基于拟合概率密度函数)阐述电导率和磁化(密度)之间的经验关系，以及(V)在所有可用地球物理数据的基础上对Kaoko带、其与Walvis Ridge的相互作用和向刚果克拉通的过渡得出一致的地质解释。