Mid-to-Deep-crustal Electromagnetic Investigation of the Tepic–Zacoalco Rift (DEMITZ) – Exploring Magmatic Systems and Electrical Anisotropy in Western Mexico

特皮卡萨夸尔科裂谷 (DEMITZ) 的中深地壳电磁调查 – 探索墨西哥西部的岩浆系统和电各向异性

• 批准号: 444936561
• 负责人: Professor Dr. Andreas Junge
• 金额: --
• 依托单位: Dublin Institute for Advanced Studies (DIAS)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/444936561?language=en
• 关键词: Mid; Deep; crustal; Electromagnetic; Investigation

The proposal suggests a large scale magnetotelluric (MT) investigation of the conductivity distribution within magmatic systems in the context of tectonic processes, exemplarily for the Tepic-Zacoalco Rift in Western Mexico. Deep crustal and upper mantle conductivity anomalies allow conclusions about the linkage between magma chambers resp. a common source at greater depth. Furthermore, we expect that the analysis of the spatial distribution of possible anisotropic conductivity will hint at magma related fracture systems and their interaction with the graben structure. Within the upper mantle, anisotropy may characterize geodynamic processes related to subduction nearby.The proposal, based on a recent dissertation by Philip Hering within the working group of the proponent, verified two conductivity anomalies within the Ceboruco Volcano and an anisotropic layer at 10 km depth. The volcano is located, among other volcanoes, within the Tepic-Zacoalco Rift. Thus 48 MT broadband systems and 12 long period sites shall be installed within a 150km x 100km large area around the volcano. The data will be processed by the Frankfurt software package FFMT developed within the dissertation. It uses an Eigenvalue criterion for calculating robust MT transfer functions (TF), such as impedance tensors, CARTs (complex apparent resistivity tensor) and tipper vectors, for the frequency range 0.0001-1000 Hz from simultaneously recording MT systems. The dissertation shows that for the long period range the spatially consistent pattern of the phase tensor ellipses may represent anisotropic properties of the conductivity. The pattern was reproduced by a preliminary study for MT data from the San Pedro volcano nearby. As CARTs and tippers are not influenced by static-shift phenomena, the distance between sites is adapted to the target depth, allowing regional coverage by the number of sites mentioned above.Modeling comprises two steps: At first, the transfer functions are inverted using ModEM, a widely used inversion code for the computation of isotropic 3D conductivity anomalies. Secondly, the model resp. the data fit is improved stepwise by the implementation of anisotropic bodies and the calculation of the TFs by Comsol Multiphysics® FE software. In particular, we will investigate the influence of large scale heterogeneities and/or anisotropy of the electrical conductivity on the observed phase differences.Finally, the conductivity model will be interpreted within the petrophysical resp. the tectonic-geodynamic context, considering the findings of other geoscientific investigations. The project will contribute substantially to the overall description of magmatic processes triggered by subduction and subsequent tectonic and geodynamic processes.

该建议建议在构造过程背景下，以墨西哥西部的Tepic-Zacoalco裂谷为例，对岩浆系统内的电导率分布进行大规模大地电磁调查。深部地壳和上地幔电导率异常可以得出岩浆房之间联系的结论。一个更深层的共同来源。此外，我们期望对各向异性电导率的空间分布分析将提示与岩浆有关的断裂系统及其与地堑结构的相互作用。在上地幔内部，各向异性可能是与附近俯冲有关的地球动力学过程的特征。该提案基于提案者工作组Philip Hering最近的一篇论文，验证了Ceboruco火山内部的两个电导率异常和10公里深度的各向异性层。与其他火山一样，这座火山位于泰皮克-扎科阿尔科裂谷内。因此，48兆兆兆位宽带系统和12个长期站点将安装在火山周围150公里× 100公里的大面积区域内。数据将由论文中开发的法兰克福软件包FFMT处理。它使用一个特征值准则来计算鲁棒MT传递函数（TF），如阻抗张量、cart（复视电阻率张量）和自旋矢量，用于同时记录MT系统的频率范围0.0001- 1000hz。研究表明，在长周期范围内，相位张量椭圆的空间一致性可以代表电导率的各向异性。对附近圣佩德罗火山的MT数据进行的初步研究再现了这一模式。由于cart和自卸车不受静态移位现象的影响，站点之间的距离适应目标深度，允许通过上述站点的数量覆盖区域。建模包括两个步骤：首先，使用广泛用于计算各向同性三维电导率异常的反演代码ModEM对传递函数进行反演。其次，模型响应。通过各向异性体的实现和Comsol Multiphysics®有限元软件的TFs计算，逐步提高了数据的拟合性。特别是，我们将研究电导率的大尺度非均质性和/或各向异性对观察到的相位差的影响。最后，将在岩石物理方面解释电导率模型。构造-地球动力学背景，考虑到其他地球科学调查的结果。该项目将大大有助于全面描述由俯冲和随后的构造和地球动力学过程引发的岩浆过程。