Australia-wide 3D Density and Magnetic Susceptibility Models: Method and Model Release

Two coincident, crustal-scale models, one of magnetic susceptibility and one of density, have been produced for a volume covering the Australian continent and extending down to 55.5 km depth. These models were produced using the UBC GIF MAG3D and GRAV3D inversion programs, respectively. The inversions were constrained with geological reference models with layers for sediments, undifferentiated crust and the mantle. The reference model for the magnetic inversion incorporated a Curie depth surface below which magnetic susceptibility was set to zero. Due to the size of the inversion problem to be solved, the volume was divided into 235 overlapping inversions, which were inverted separately and then recombined. The method of recombining the inversions relies on a cosine function to determine the weight of each property and then takes a weighted average. This method successfully attenuated the edge effects that would otherwise occur between models and allows them to be viewed as one seamless model that covers the whole of Australia. Regions of coincident high-density (&gt;2.83 g/cm³) and high-magnetic susceptibility (&gt;0.0125 SI) within the top 10 km of the undifferentiated crust (termed magnetite proxies) are suggested to be related to ultramafic rocks and the magnetite-forming hydrothermal alteration stages of potentially fertile IOCG systems (see download link: Magnetite region grids) . <b>Download Link & Description</b> <b>•</b> GA Record (.pdf) - The report describing the method and model results. PDF document. <b>•</b> Intermediate grids (.ers) - The Australia-wide intermediate grids of elevation, gravity, and total magnetic intensity. ERMapper (.ers) format. <b>•</b> Magnetite region grids (.ers, .tif) - The Australia-wide magnetite proxy regions projected onto a 2D surface. ERMapper (.ers) and GeoTiff (.tif) format. <b>•</b> Subset_[1-17] (.sg, .den, .sus) - The Australia-wide 3D density and magnetic susceptibility models in SGrid (.sg) and UBC-GIF (.den, .sus) formats. Also includes the geological reference model surfaces (.ts). <b>•</b> Individual inversion files - GRAV3D and MAG3D input and output files for the 235 individual UBC-GIF inversions (before being recombined using cosine weighting). <b>Individual inversion input/output files for A1-V2 are available on request from [e-mail] - Quote eCat# 149226</b> Due to their size, the Australia-wide models have been divided into subsets (labelled 1-17) for download. Please refer to the image below for the extent of the subsets.