Induced polarization response of porous media with metallic particles — Part 7: Detection and quantification of buried slag heaps

Abstract

With the progress of metallurgical activities, more and more dumped slag heaps emerge as valuable deposits to feed the growing need for metal resources. Detecting, quantifying, and reextracting metals from these slags may complement the prospection of new ore deposits. However, the spatial delineation of the slag heap cannot easily be obtained from the resistivity distribution alone (determined either with galvanometric or with induction-based methods). Although the magnetic method can detect slag heaps, it fails to make an estimation of the quantity of metal present in the slag. Alternatively, the induced polarization (IP) method can be used to fulfill this goal. The complex conductivity responses of slag samples from a slag heap in France are obtained in the laboratory. These data are used to assess the grade of the slag, which is close to 8%. Then, a least-squares 3D IP inversion is used to get the subsurface chargeability distribution delimiting the slag heap in the ground. From the linear relationship determined between the chargeability and the volumetric metal content or the volumetric slag content, the metallic volume of the slag heaps can be directly determined. This approach is used at the site of Saint-Vincent sur L'Isle, Dordogne (France), where it allows characterizing the shape of a slag heap and quantifying the total cumulative metal content of the investigated area.

Three‐Dimensional Electrical Conductivity and Induced Polarization Tomography of a Rock Glacier

“…Journal of Geophysical Research: Solid Earth method on synthetic and true field data has already been performed in Soueid Ahmed, Revil, Jardani, et al (2018) and Soueid Ahmed, Revil, Byrdina, et al (2018) for the resistivity and chargeability problems and by Qi et al (2018).…”

Quantifying Induced Polarization of Conductive Inclusions in Porous Media and Implications for Geophysical Measurements

“…The "chargeability" m quantifies the relative change in conductivity between the low-and high-frequency limits, whereas τ is a characteristic relaxation time and c is the Cole-Cole exponent. This model has originated from dielectric spectroscopy and has been successfully developed to understand metal-dielectric systems [19][20][21] , although its application to model observed IP response 16,22,23 has been largely empirical. Membrane polarization 4,9,12 usually ties to IP effects observed in clay and shaley sand 3,9,24,25 , in glass materials such as silica sands with a Stern layer (also known as "charge polarization" 26,27 ), and ion-selective membranes in electrochemical cells (also known as "concentration polarization" 28 ).…”

“…These grains act as short circuits in the high-frequency limit and insulators in the low-frequency limit, therefore the chargeability depends primarily on the effective volume fraction of the conductive grains, and does not diminish at higher salinities. Unlike membrane polarization, the electrode polarization relaxation time has strong dependence on the conductivity of the pore fluid 22,30,32 . There are several mechanistic and semi-empirical models for electrode polarization 29,[31][32][33] with broad agreement on chargeability but very different explanations for the relaxation time.…”

Induced polarization of volcanic rocks. 3. Imaging clay cap properties in geothermal fields

“…A total of 1179 apparent resistivity and apparent chargeability data were obtained at Site 2. The data sets were inverted with the codes developed in Soueid Ahmed et al (2018), Ghorbani et al (2018) and Qi et al (2018) taking into account the topography. During the modeling, unstructured tetrahedrons were used to discretize the models for their good ability to emulate the topography.…”