Time domain spectral induced polarization of disseminated electronic conductors: Laboratory data analysis through the Debye decomposition approach |
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| Institution: | 1. St Petersburg State University, Department of Geophysics, Faculty of Geology, 7/9 Universitetskaya Naberezhnaya, 199034 St. Petersburg, Russia;2. “BGK” Ltd., 1 Petrovskaya Kosa Street, 197110 St. Petersburg, Russia;3. “VIRG-Rudgeofizika” JSC, 1 Petrovskaya Kosa Street, 197110 St. Petersburg, Russia;1. Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris, France;2. UMI 209 “UMMISCO”, Institut de Recherche pour le Développement, France;3. Colorado School of Mines, Dept of Geophysics, Golden, CO, USA;4. ISTerre, CNRS, UMR CNRS 5275, Université de Savoie, 73376 cedex, Le Bourget du Lac, France;5. UMR-CNRS 7619 « METIS », Paris, France;1. Université Grenoble Alpes, CNRS, IRD, IFSTTAR, ISTerre, Grenoble, France;2. Université Savoie Mont Blanc, ISTerre, Chambéry, France;3. School of Safety Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, China;4. School of Civil Engineering, Shandong University, 17922 Jingshi Rd, Jinan, Shandong 250061, China;1. Engineeering Geology, Lund University, Box 118, Lund SE-22100, Sweden;2. Geotomo Software, 115 Cangkat Minden Jalan 6, Gelugor, Penang 11700, Malaysia;1. Department of Energy, Systems, Territory and Construction Engineering, University of Pisa, Via C.F. Gabba, 22, 56122 Pisa, PI, Italy;2. Department of Civil and Environmental Engineering, University of Florence, Via di Santa Marta, 3, 50139 Firenze, FI, Italy;1. Engineering Geology, Lund University, P.O. Box 118, SE-22100 Lund, Sweden;2. Department of Geoscience, Aarhus University, C.F.Møllers Allé 4, Building 1120, 8000 Aarhus C, Denmark;1. Leibniz Institute for Applied Geophysics, Hannover, Germany;2. Federal Institute for Geosciences and Resources, Berlin, Germany |
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| Abstract: | We measured Spectral Induced Polarization responses of 22 models of disseminated ore with a time domain (TD) technique. The models were mixtures of calibrated sand (0.2–0.3 mm) with calibrated ore grains (average radii: 0.045, 0.055, 0.13, 0.20, 0.38 and 0.55 mm). The grains represent a mixture of pyrrhotite (30%), pyrite (30%), magnetite (30%) and chalcopyrite (10%) coming from a natural ore. In the models, the grain concentration (by volume) varied between 0.6 and 30%.We obtained IP decays with a conventional field TD measuring technique and a lab low-current transmitter in the time range from 0.3 ms to 64 s. The IP decays measured with various current wavelength forms were inverted to relaxation time distributions (RTD) on the basis of the Debye decomposition approach.RTD parameters were found to be closely related to the ore volumetric content and the ore grain size. The total chargeability is independent of the grain size, but is determined by the grain volume fraction. In contrast, the mean IP relaxation time is related to the grain size. These facts make RTD attractive to use in ore prospecting and studying reactive permeable barriers.Moreover, for low salinity pore water used in this study, the relaxation times of disseminated ores are three to four decades smaller than that of the insulating grains of the same size typical of common soils and sediments. This allows recover the relaxation times on the basis of relatively fast IP measurements with short time pulses (in TD) or high frequency values in the frequency domain; however attention should be paid to inductive and capacitive couplings. |
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