Fast approximate inversion of TEM data

Abstract

Converting TEM data to an ideal system response removes interpretational problems associated with the characteristics and imperfections of practical waveforms. It also allows the inductive and resistive limits, defined from frequency domain theory to be trivially calculated for input into fast, approximate inversion programs. Rapid, stable conversion can be achieved by decomposition to a set of exponential basis functions preconvolved with the system waveform. The process is applied to 3-D model moving loop SIROTEM data for a dipping conductive plate beneath a conductive overburden. The extracted inductive and resistive limit profiles are inverted to dipping filament loops The inversions return basic geometrical parameters comparable with those of the original plate model. Finally, fixed loop SIROTEM data over the Eloise Cu-Au deposit are transformed and inverted. The models returned are consistent with the known geology of the deposit.