One-dimensional and three-dimensional inversions in evaluating the ore bodies’ polarization parameters in the Altai Mountains

The purpose of the work is to study natural-mode polymetallic ore occurrences in the Altai Mountains using microinstallations (small-step measuring devices) for a qualitative evaluation of the ore bodies’ geoelectric characteristics. To evaluate the ore bodies’ geoelectric characteristics, the investigated medium was excited by a sequence of multidirectional current pulses in a generator dipole, and the electromagnetic field was registered by the receiving line by the technique of electromagnetic sounding and induced polarization. For the purposes of the medium modeling, an inversion of the non-stationary electromagnetic fields was applied within one-dimensional and tree-dimensional models with the account of the induced polarization effect. The zones with anomalous characteristics that were obtained with the one-dimensional inversion, correlate with the high silver- and copper-content zones defined by the means of the detailed geochemical sampling of the ditch. The three-dimensional modeling process used the following border conditions: the geometry of the ore bodies was set by the geological section, and their properties, by the one-dimensional inversion data. The polarization parameter anomalies obtained after several iterations have shown a spatial coincidence with the ore bodies position on the geological section. The relaxation time anomaly that is beyond the electrical survey profile corresponds to the known ore seam that had not been set in the initial approximation, which suggests a high sensitivity of the electromagnetic sounding and induced polarization technique to the polarization characteristics of the ore bodies. The study of the sulfide-mineralization ore bodies with the microinstallations provides information on the ore bodies’ polarization characteristics, spatial position, angle of incidence, and size. The suggested approach can be used in the geological-geophysical interpretation of the areal electromagnetic sounding data to define promising ore occurrences and optimize the prospect drilling and mining.

electromagnetic sounding, induced polarization, sulfide mineralization, one-dimensional inversion, three-dimensional inversion

1. Davydenko YuA, Davydenko AYu, Pesterev IYu, Yakovlev SV, Davydenko MA, Komyagin AV, Shimyanskii DM. Measurement and processing method for grounded-line transient processes under the pulse excitation of the field by an electric dipole for constructing geoelectric sections, and a device for the method implementation using the hardware-andsoftware electric prospecting complex (HSEPC "MARS"). Patent RF, no. 2574861; 2016. (In Russ.)

2. Marshall DJ, Madden ThR. Induced polarization, a study of its causes. Geophysics. 1959;26:790–816.

3. Gurin GV, Tarasov AV, Il'in YuT, Titov KV. Ore volumetric content from induced polarization data. Vestnik Sankt-Peterburgskogo universiteta. Geologiya i geografiya = Saint-Petersburg University Bulletin. Geology and Geography. 2014;3:4–19. (In Russ.)

4. Bleil DF. Induced polarization, a method of geophysical prospecting. Geophysics. 1953;18:636–661.

5. Postel'nikov AF. On the nature of induced polarization in sedimentary rocks. Geologiya i razvedka = Geology and Exploration. 1959;2:126–136. (In Russ.)

6. Postel'nikov AF. On the nature and mechanism of induced polarization formation on the electron- conductive rock samples. Trudy Tsentral'nogo nauchno-issledovatel'skogo gornorazvedovatel'nogo instituta = Proceedings of the Central Research Mining Prospecting Institute. 1964;59:153–164. (In Russ.)

7. Bhattacharyya B, Morrison H. Some theoretical aspects of electrode polarization in rocks. Geophysical Prospecting. 1963;11(2);62–72.

8. Semenov AS. Electrical survey by the selfpotential method. Leningrad: Nedra; 1980. 446 p. (In Russ.)

9. Sumner JS. Principles of induced polarization for geophysical exploration. Amsterdam: Elsevier; 1976. 277 p.

10. Titov K, Gurin G, Tarasov A, Akulina K. Spectral induced polarization: frequency domain versus time domain. 3rd International Workshop on Induced Polarization, 6–9 April. Oléron Island, France; 2014. p.78–79.

11. Flis MF, Newman GA, Hohmann GW. Induced-polarization effects in time-domain electromagnetic measurements. Geophysics. 1989;54(4):514–523.

12. Kulikov AV, Shemyakin EA. Electrical survey by the phase method of induced polarization. Moscow: Nedra; 1978. 157 p. (In Russ.)

13. Cole KS, Cole RH. Dispersion and absorption in dielectrics. Alternating current characteristics. Journal of Chemical Physics. 1941;9(4):341–351.

14. Pelton WH, Ward SH, Hallof PG, Sill WR, Nelson PH. Mineral discrimination and removal of inductive coupling with multifrequency IP. Geophysics. 1978;43:588–609.

15. Persova MG, Soloveichik YuG, Vagin DV, Domnikov PA. Comparison of different numerical modeling approaches for three dimensional induced polarization. Proceedings of the Russian Higher School Academy of Sciences. 2011;2:123–139. (In Russ.)

16. Tarasov A, Titov K. Relaxation time distribution from time domain induced polarization measurements. Geophysical Journal International. 2007;170:31–43.

17. Fiandaca G, Auken E, Gazoty A, Christiansen AV. Time-domain induced polarization: full-decay forward modeling and 1D laterally constrained inversion of Cole-Cole parameters. Geophysics. 2012;77:213–225. https://doi.org/10.1190/geo2011-0217.1.

18. Fiandaca G. Line Meldgaard Madsen and Pradip Kumar Maurya. Re-parameterisations of the Cole-Cole model for improved spectral inversion of induced polarization data. Near Surface Geophysics. 2018;16:385–399. https://doi.org/10.3997/1873-0604.2017065.

19. Kormil'tsev VV, Mezentsev AN. Electrical survey in polarizing media. Sverdlovsk: Ural Branch of the Academy of Sciences of the USSR; 1989. 128 p. (In Russ.).

20. Davydenko YuA, Aikasheva NA, Bashkeev AS, Faustova AYu, Bogdanovich DV. The results of the pulse electrical survey application in prospecting for ore mineral deposits in the mountainous Altai. Inzhenernaya i rudnaya geofizika 2018: sbornik statei 14 nauchno-prakticheskoi konferentsii i vystavki = Engineering and mining geophysics in 2018: collected works of the 14th Science-to-practice Conference and Exhibition, 23–27 April 2018, Almaty. 8 p. Available from: http://www.earthdoc.org/publication/publicationdetails/?publication=91717 [Accessed 3nd September 2019].

21. Persova MG, Soloveichik YG, Trigubovich GM. Computer modeling of geoelectromagnetic fields in three-dimensional media by the finite element method. Izvestiya. Physics of the Solid Earth. 2011;47(2):79–89.

22. Persova MG, Soloveichik YG, Tokareva MG, Trigubovich GM. Methods and algorithms for reconstructing three-dimensional distributions of electric conductivity and polarization in the medium by finite-element 3D modeling using the data of electromagnetic sounding. Izvestiya. Physics of the Solid Earth. 2013;49(3):329–343.

23. Belova AYu, Gurevich DV, Bogdanovich DV, Aikasheva NA, Bashkeev AS, Bukhalov SV, et al. Exploration for concealed copper-molybdenum ore deposits in Northern Kazakhstan using the techniques of electromagnetic sounding and induced polarization. Inzhenernaya i rudnaya geofizika 2019: sbornik statei 15 nauchno-prakticheskoi konferentsii i vystavki = Engineering and Mining Geophysics 2019: collected works of the 15th Researchto-practice Conference and Exhibition, 22–26 April 2019, Gelendzhik. 11 p. Available from: http://earthdoc.eage.org/publication/publicationdetails/?publication=96758 [Accessed 3nd September 2019].

24. Kulikov VA, Yakovlev AG. The use of induced polarization time/frequency characteristics for carbonized and sulfide rock anomalies determination. Russian Geophysics. 2008;6:55–59. (In Russ.)

25. Kulikov VA, Zorin NI, Manzheeva IT, Yakovlev AG. Using of differential phase parameter (DPP) for IP anomalies separation. Russian Geophysics. 2013;6:23–31.