f Application of spectral induced polarization measurements in unconsolidated rocks

The characterisation of geological barriers and storage rocks or soils as well as the interaction with the stored materials and contaminants are frequent tasks in environmental and engineering geophysics. Due to the slight or not existing effects of contamination on geophysical parameters it is often difficult to use this techniques in such purposes. Therefore we investigate the influence of contamination at the SIP (spectral induced polarisation) properties. The SIP measurement yields the frequency dependent amplitude and phase of complex resistivity. In contrary to DC resistivity the SIP depends on the interface between matrix and fluids and the pore space geometry. A change of these parameters by contamination causes a SIP effect. The effects of an organic contaminant on the phase and amplitude spectra of the resistivity were studied using artificially contaminated samples. Unfortunately the relationship between rock parameters and SIP properties is up to now only partially understood. The Cole Cole model which is widely used in mineral exploration is not suitable for unconsolidated rocks. Mainly from laboratory measurements were derived several empirical models. For instance the used linear phase model (Radic, 1998). The new CR measuring instrument "SIP-Fuchs", developed at the Technical University of Berlin, Germany, enable us to determine the frequency dependence of the complex resistivity under field conditions. The SIP instrument measures the complex resistivities at successive frequencies from 100 mHz to 12 kHz.