The use of electrical conductivity and magnetic susceptibility tensors in rock fabric studies

Abstract

Laboratory electrical conductivity (s) anisotropy measurements were made on water saturated Palaeozoic black shales, mineralized schists, and banded and massive sulphides from the Mt Lyell region Tasmania. Macro- and micro-fabric and magnetic anisotropy studies were also carried out. Directional 1 kHz conductivity values were obtained in 9 directions for each of 10 samples. Reduction of these measurements produced the electrical conductivity tensor principal values and directions which were correlated with the fabric and magnetic data. The study suggests that: (i) a water saturated layered rock may be characterised by large s1:s2:s3: anisotropy; (ii) the conductivity tensor representation may reflect petrofabric; and (iii) anisotropy may cause the current density to deflect significantly from the electric field direction.