Advancement of the Induced Polarization Method for Metallic Mineral Estimation and Differentiation

• Applicant: Dr. Saeideh Ahmadi, Ph.D.
• Subject Area: Geophysics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 584339879

Recent advances in induced polarization (IP) have improved our understanding of metallic mineral estimation and differentiation. Chargeability correlates with mineral volume up to ~22%, but beyond that, the relationship becomes ambiguous, indicating a research gap. Recent studies challenge the effective-medium theory, showing that higher mineral content reduces chargeability, suggesting it alone may not reliably indicate mineral volume. Current mechanistic IP models often oversimplify grain geometry, neglect mineral interactions at high concentrations, inadequately represent the semiconductor properties of metallic minerals, and oversimplify or ignore metal-electrolyte interface electrochemical reactions. While electrochemical models provide a more physically accurate description of interfacial processes, they involve poorly constrained parameters, limiting their practicality. Empirical models like Cole–Cole or Debye decomposition fit experimental data well but lack a physical basis, complicating data interpretation. To address these limitations, this project develops a finite element-based numerical framework solving the Poisson–Nernst–Planck equations. Building on an established model for metallic particle polarization, it will integrate recent insights on charge carrier mobility and semiconductor inner surface polarization. The model will simulate the IP response of individual semiconducting mineral grains, explicitly representing surface capacitances at the mineral–electrolyte interface (internal, Stern and diffuse layers). Key parameters—mineral volume, interfacial potential, and mineral conductivity—will be varied to investigate their effects on chargeability and relaxation time. Changes in interfacial potential will assess electrochemical reactions and conductivity simulations will cover various minerals. Particle interactions will also be included to reduce geometric simplifications. Complementary laboratory experiments will validate and refine the model. Twenty synthetic sand–mineral mixtures with various semiconductor types (galena, chalcopyrite, bornite, chalcocite, pyrite) and concentrations (15–50vol%) will be prepared and characterized using mineralogical analysis, CT scanning, and nitrogen adsorption. After brine saturation, complex conductivity will be measured over 10mHz–45kHz, and impedance spectra fitted with the Cole–Cole model or Debye decomposition to extract chargeability and relaxation parameters. Their dependence on mineral content and type will be compared with numerical predictions. This integrated numerical–experimental approach aims to enhance understanding of electrode polarization mechanisms in metal-rich ore deposits and the physicochemical factors influencing IP behavior. The resulting model will advance the physical understanding and predictive capabilities of IP methods in mineral exploration and deposit characterization, laying the groundwork for next-generation interpretation tools in geophysical prospecting.

• DFG Programme: Position