Development of the induced polarization theory with application to exploration of strategic raw materials

• Applicant: Professor Dr. Andreas Weller
• Subject Area: Geophysics
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 425975038

• Final Report Year: 2024

Final Report Abstract

Induced polarization (IP) is a geophysical method that investigates the electrical properties of geo-materials that can be described by the frequency dependence of both electrical conduction and polarization. The IP method has been successfully applied in the exploration of mineral resources for many decades. New applications arise in hydrogeology, geotechnics and archaeometry. A good quantitative interpretation of laboratory and field data requires reliable models that describe the conduction and polarization phenomena based on acknowledged physical and chemical laws. The measured IP spectra include a superposition of several polarization mechanisms (e.g., polarization of the electrical double layer, membrane polarization, Maxwell-Wagner polarization, electromagnetic coupling effects). The relevance of the different phenomena depends on the type of material and the used frequency range. The investigations performed in the project aim at an improved understanding of the measured IP effects of material with metallic particles or without metallic particles. The investigation of ore and slag samples have revealed a variety of effects that are related with temporal changes of the mineral surfaces. Systematic investigations on synthetic samples with metallic spheres or mixtures with metallic particles enable a separation of different effects. The comparison with the results of existing models or numerical experiments provides insight how particle size, volume content, conductivity and other parameters of the embedding material affect the measured IP signal. Some experimental result contradict existing models. We found that beside the volume content the particle size is another parameter that affects the chargeability. The polarization of clay mixtures and mudstones have been investigated in additional experimental studies. We found that the positive correlation between clay content and polarization does not hold for material with a high clay content. The spectral information of the material can be extracted by measurements in the frequency domain (FD) or time domain (TD). The Debye decomposition (DD) approach has proved to be an appropriate tool to compare or transform the spectral content acquired in the different domains. The DD approach can be successfully applied to quantify changes of the chargeability derived from TD logging data.

Publications

• Desaturation effects of pyrite–sand mixtures on induced polarization signals. Geophysical Journal International, 228(1), 275-290.
  Martin, Tina; Weller, Andreas & Behling, Laura
  
• Spectral induced polarization: frequency domain versus time domain laboratory data. Geophysical Journal International, 225(3), 1982-2000.
  Martin, Tina; Titov, Konstantin; Tarasov, Andrey & Weller, Andreas
  
• Ambiguity in induced polarization time constants and the advantage of the Pelton model. Geophysics, 87(6), E393-E399.
  Weller, Andreas & Slater, Lee
  
• Characterization of surface conductivity of clays. Contribution to the 6th International IP Workshop at Annecy, France.
  Emelianov, V., Zhang, Z., Titov, K., Halisch, M. & Weller, A.
  
• The Influence of Magnetic Minerals on Induced Polarization Measurements in Sedimentary Rocks. Geophysical Research Letters, 49(19).
  Peshtani, Klaudio; Weller, Andreas; Saneiyan, Sina & Slater, Lee
  
• Superposition of induced polarization signals measured on pyrite–sand mixtures. Geophysical Journal International, 234(1), 699-711.
  Martin, Tina & Weller, Andreas
  
• Modeling of spectral induced polarization on cm-sized metallic spheres in sand-water mixtures. Contribution to the 7th International IP Workshop at Lund, Sweden.
  Kreith, D., Breede, K., Zhang, Z., Weller, A. & Bücker, M.
  
• Permeability and Induced Polarization of Mudstones. Water Resources Research, 60(8). Portico.
  Peshtani, Klaudio; Weller, Andreas & Slater, Lee
  
• Surface conductivity of clays. Geophysical Journal International, 238(2), 1013-1026.
  Emelianov, Viacheslav; Zhang, Zeyu; Weller, Andreas; Halisch, Matthias & Titov, Konstantin
  
• Understanding the Fate of H2S Injected in Basalts by Means of Time‐Domain Induced Polarization Geophysical Logging. Journal of Geophysical Research: Solid Earth, 129(6).
  Lévy, L.; Ciraula, D. A.; Legros, B.; Martin, T. & Weller, A.
  
• Modeling of spectral induced-polarization measurements on cm-sized metallic spheres in sand-water-mixtures. Copernicus GmbH.
  Kreith, Dennis; Breede, Katrin; Zhang, Zeyu; Weller, Andreas & Bücker, Matthias