An assessment of CSAMT data for location of mineralised targets under glacial cover (Western Tasmania) and basalt cover (Victorian goldfields)

Abstract

New algorithms for all-frequency apparent resistivity, static corrections and Bostick transforms of CSAMT data allow real-time production of parasections of resistivity vs depth from profiles of CSAMT data. This allows rapid visualisation of 2D and 3D CSAMT model data and comparison with field data. Interactive fitting of parasections of model and field data provides an alternative to formal inversion. The process is used to model the effect of glacial erosion features in CSAMT data from Western Tasmania and assess the sensitivity of the CSAMT method to the detection of targets such as steeply-dipping graphitic and mineralised alteration zones. The approach has advantages of flagging data affected by cultural (power transmission line) noise, provides clear discrimination between effects of surficial conductive variations such as filled glacial erosion features, and discriminates between genuine dipping conductors, vertical conductors, and artefacts from near-surface effects which may generate ``apparent' vertical conductive anomalies. A similar approach using CSAMT data from basalt-covered terrain in the Victorian goldfields, combined with 3D EM modelling, was successful in identifying a prospective sulfidic conductor in the Ordovician basement, beneath variably-conductive basalt cover.