Perspectives of using the inductive component of transition process in traditional DC methods

Category: 16-4
Y.A. Davidenko, P.A. Popkov, A.V. Novopashina

UDC 550.837

  

Y.A. Davidenko(1,2), P.A. Popkov(3), A.V. Novopashina(1,2)

 

(1) National Research Irkutsk State Technical University, Irkutsk, Russia

(2) Institute of the Earth’s Crust, Siberian Branch of RAS, Irkutsk, Russia

(3) JSC “Anabar diamonds”, Yakutsk, Russia

 

Abstracts. The paper discusses electromagnetic sounding and induced polarization methods (EMIP method) developed for solving a wide range of problems in shallow-depth, ore and oil geophysical exploration.

The idea of EMIP methods has been formulated through re-processing of the data obtained by exploration using INFAZ IP method for measurement of the mean gradient to reveal blowholes on the Anabar shield. The use of program modules of the geoelectric hardware-software complex (GHSC) “Mars” provided an opportunity to make the fieldwork material more informative and identify transient impulses. As a result, a blowhole not shown on the apparent resistivity map has been contoured near the reference object. The drilling data has shown that the blowhole is overlain by high-resistivity terrigenous multi-year frozen lacustrine sediments preventing current penetration. Sensitivity to variation in the section of geoelectric parameters has been determined based on one-dimensional inversion of the areal data to a depth of 1200 m.

EMIP methods imply the maximum use of information on transient processes recorded using potential electrodes at the current passage through grounded dipole. High-resistivity layers are transparent for induced currents arising from impulse cutoff. Besides, passage of current evokes polarized medium, and current cut-off leads to the induced polarization (IP) effects related to chemical composition and physical properties of the rocks. Simultaneous use of information on the induction component and IP processes allows identifying low-contrast polarizable objects (rocks with disseminated sulfide mineralization) in high-resistivity rocks (granites, basalts, etc.). 

Keywords: robust regression analysis, induced polarization, electromagnetic sounding, mean gradient, transients, frequency dispersion of conductivity, robustness. 

 

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