73 2. Surface geophysical methods example shown in Figure 2.14, the distance between 2 injection electrodes is 50 m, the distance between 2 receiving nodes is 100 m, the overall length of the profile is 4500 m. After electrical resistivity inversion, the resistivity section has a depth investigation of several hundred meters. Electrical resistivity tomography (ERT) and Induced polarization (IP) surveys can provide resistivity, porosity, reaction temperature and cation exchange capacity (CEC) tomograms from surface measurements (Piolat et al., 2024). ERT/IP survey results for the Amashyuza geothermal prospect (Rwanda) are shown in Figure 2.15 (after Piolat et al., 2024). Electrical geophysical methods are of great value in this context, as they provide vital information on fluid flow networks, alteration intensity, hydrothermal temperatures, and geological identifications. Figure 2.13 Example of 2D electrical tomography, obtained on the rock glacier of Verbier in Switzerland. (a) line of electrodes (distance between two adjacent electrodes is 10 m) and theoretical location (indicated by dots) of apparent resistivity measurement depending on the array configuration, (b) view of the rock glacier of Verbier, c: resistivity section. After D. Chapellier (2001b, Document IGL). (c) (b) (a)
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