Geophysical Prospecting, 2018, 66, 798–817 doi: 10.1111/1365-2478.12581 Complex resistivity of mineral rocks in the context of the generalised effective-medium theory of the induced polarisation effect Michael S. Zhdanov 1,2 , Vlad Burtman 1,2 , Masashi Endo 2∗ and Wei Lin 1 1 Consortium for Electromagnetic Modeling and Inversion (CEMI), The University of Utah, Salt Lake City, UT 84112 USA, and 2 TechnoImaging, Salt Lake City, UT 84107 USA Received October 2016, revision accepted September 2017 ABSTRACT This paper develops the generalised effective-medium theory of induced polarisation for rock models with elliptical grains and applies this theory to studying the complex resistivity of typical mineral rocks. We first demonstrate that the developed gener- alised effective-medium theory of induced polarisation model can correctly represent the induced polarisation phenomenon in multiphase artificial rock samples manufac- tured using pyrite and magnetite particles. We have also collected representative rock samples from the Cu–Au deposit in Mongolia and subjected them to mineralogical analysis using Quantitative Evaluation of Minerals by Scanning Electron Microscopy technology. The electrical properties of the same samples were determined using lab- oratory complex resistivity measurements. As a result, we have established relation- ships between the mineral composition of the rocks, determined using Quantitative Evaluation of Minerals by Scanning Electron Microscopy analysis, and the parame- ters of the generalised effective-medium theory of induced polarisation model defined from the laboratory measurements of the electrical properties of the rocks. These re- lationships open the possibility for remote estimation of types of mineralisation and for mineral discrimination using spectral induced polarization data. Key words: Complex resistivity, Induced polarisation, Mineral rocks, Generalised effective-medium theory. INTRODUCTION One of the major problems in mineral exploration is the inabil- ity to reliably distinguish between economic mineral deposits and uneconomic mineralisation. While the mining industry uses many geophysical methods to locate mineral deposits, until recently, there was no reliable technology for identifica- tion and characterisation of mineral resources. In this paper, we address this problem by studying the complex conduc- tivity of mineral rocks, which is manifested by the induced polarisation (IP) effect. Indeed, effective conductivity of rocks is not necessarily a constant and real number but may vary with frequency and be complex. There are several explana- tions for these properties of effective conductivity. Most often, ∗ E-mail: masashi@technoimaging.com they are explained by the physical–chemical polarisation ef- fects of mineralised particles of the rock material and/or by membrane effects in the pores of reservoirs (Marshall and Madden 1959; Wait 1959; Luo and Zang 1998; Vanhala and Peltoniemi 1992). The polarisability effect is usually associ- ated with the surface polarisation of the coatings of the grains. This surface polarisation can be related to an electrochemi- cal charge transfer between the grains and the host medium (Wong 1979; Wong and Strangway 1981; Klein, Biegler and Hornet 1984). Surface polarisation is manifested by accumu- lating electric charges at the surface of the grain. A double layer of charges is created, which results in a voltage drop across the grain boundary (Wait 1982). The physical–mathematical principles of the IP effect were originally formulated in the pioneering works of Wait (1959, 1982) and Sheinman (1969). However, the IP method 798 C  2017 European Association of Geoscientists & Engineers