Low-frequency (0.18 Hz to 1.5 kHz) effective dielectric spectra have
been measured on a set of near-saturated samples of argillite. The
measured spectra of the real part of the complex apparent permittivity
did not show significant correlation with cation exchange capacity
(CEC) per unit mass of rock values. They satisfied a power law relationship
with the frequency, at least for samples with CEC values lower than
10 cmol/kg. The Maxwell-Wagner-Hanai-Bruggeman formulation used for
a two-phase mixture has been modified to account for mutual polarization
between the pockets of water located in the micropores and those
located in the macropores. The results of the modeling calculations
illustrate (1) the ability of this new formulation to reproduce the
power law relationships of the measured spectra of the real and imaginary
components of the complex permittivity and (2) the strong impact
of the pore electrical conductivity.