Next generation 3D geological and geophysical modelling, West Tasmania

Abstract

Airborne magnetic and ground gravity data have been inverted to recover 3D distributions of magnetic susceptibility and density over an area (40 km x 35 km) in western Tasmania. Building on previous modelling and structural interpretation, the overall modelling strategy focused initially on the most magnetic units (Cambrian ultramafics), which are regionally associated with major tectonic features. Interpretation of their geometry via iterative 3D magnetic inversion and geometry adjustment thus outlines a structural framework capable of satisfying geologic and magnetic and gravity observations. Significant slabs of ultramafic material are demonstrated to underlie a considerable portion of the area, agreeing with previous 2D forward model investigations. This framework is effectively filled in with other major geological elements, including extensive low-density Devonian granites and magnetic Cambrian granites, such that geologic, magnetic and gravity constraints are all grossly satisfied. Magnetic and gravity residuals present at the conclusion of the modelling process are thus interpreted to indicate features such as alteration systems that are geologically as well as geophysically anomalous, and hence of exploration interest.