Interpretation of thick conductive zones using time-domain EM parasections

Conductivity-depth images of moving-loop time-domain EM data assist in distinguishing between near-surface and deep conductors. Use of differential conductivity provides improved resolution of conductors relative to the spiked conductivity of Smith et al. (1994). The conductance parameter is complementary to differential conductivity, in providing superior detection of conductors at depth under a conductive overburden. Field and model data from Frazers Plateau shows how differential conductivity-depth images assist in distinguishing between a wide surficial conductor and a deep basement conductor. Field and model data from the Ernest Henry mineral deposit show that the conductance parameter is superior in identifying the location of a weak, deep horizontal basement conductor (the primary mineralisation with conductance order 25 S) when it is under the conductive overburden characteristic of that environment (7 S). © 2000, CSIRO. All rights reserved.