3D constrained gravity inversions have been applied to gravity data in the Cooper Basin region of South Australia to delineate low density regions within the basement, beneath thick sequences of sedimentary cover. The low density regions, which are interpreted as granite bodies, may act as heat sources beneath thermally insulating sediments, thereby enhancing geothermal prospectivity. The Cooper Basin is the site of Australia's first geothermal project , where elevated crustal temperatures result from high-heat producing granites of the Big Lake Suite beneath the basin sediments. A 3D map of sediment stratigraphy was populated with densities and used to constrain the contribution of low density cover sediments to the observed gravity field. The resulting constrained density inversion model produced low density regions in the basement that coincide with local gravity lows. Further gravity inversions were generated and combined with gravity worm data to constrain the lateral and vertical extent of these discrete low density regions which we interpret as granite bodies. These Interpreted Granite Bodies (IGBs) coincide with granites intersected in wells. Analyses of a regional thermal model generated for a previous study, indicate that extra heat-production is required in the regions of the model that coincide with a number of the IGBs. Further thermal modelling was undertaken to determine the heat production differential between these high-heat producing IGBs and the surrounding basement. Two regions were identified where the high-heat producing IGBs are located beneath thick sequences of thermally insulating sediments. These regions, located to the east of the Big Lake Suite granodiorite and in the centre of the study area coinciding with the Barrolka gravity low, are considered to have high geothermal prospectivity.

As part of the Exploring for the Future program, whole-of-crust 3D gravity and magnetic inversion models have been produced for an area encompassing the North Australia Craton. These models were created to aid 3D geological mapping and identification of large-scale mineral systems such as those associated with iron oxide copper-gold deposits. The inversion models were derived using the University of British Columbia - Geophysical Inversion Facility MAG3D and GRAV3D programs. The inversions were constrained with geological reference models that had layers for Phanerozoic sediments, Proterozoic 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. To allow cross-referencing, both the density and magnetic susceptibility models were designed to occupy the same physical space with identical volumes and cell sizes. A horizontal cell size of 1 km was used with 61 vertical layers, whose thickness increased with depth. The area of interest is 2450 km by 1600 km and extends to a depth of 70 km below the geoid, resulting in a total volume with ~239 million cells. Ultimately, it was not possible to invert a model of this size. Instead, the volume was broken down into a grid of overlapping tiles with 8 rows and 10 columns. Each tile was independently inverted before being recombined into a single coherent output model. When the overall model was reconstructed using the core region of each tile, some low-level edge effects were observed, increasing in significance with depth. These effects were satisfactorily attenuated by applying cosine weighting from the centre of each tile out to the edge of the overlap region during reconstruction. The coincident density and magnetic susceptibility models show a relationship with known iron oxide copper-gold deposits and regions of >2.80 g/cm3 and >0.01 SI in the Tennant Creek and Cloncurry regions. It is suggested that these regions of high-density and high-magnetic susceptibility are related to the magnetite-forming hydrothermal alteration stages of an iron oxide copper-gold deposit. The success of the NAC modelling exercise has demonstrated that this method can be expanded to produce coincident gravity and magnetic inversion models for the entire Australian region. ------------------------------------------------------------------------------------------ DOWNLOADS ------------------------------------------------------------------------------------------ Input Data: The input gravity, magnetic and elevation data (.ers and .tif). Geological Reference Models: The geological reference model as surfaces and 3D volumes (.sg, .ts, and UBCGIF). Observed vs Predicted Data: The input gravity/magnetic data compared to the predicted data (.png). Recombined Models: The recombined (cosine weighted) density and magnetic susceptibility models (.sg, and UBCGIF). Magnetite Proxies: Proxies for magnetite alteration related to IOCG deposits (.ers). Video: Video describing the method and results (.mp4).

The physical properties of non-porous basement rocks are directly related to the mineralogy of those rocks. The MineralMapper3D software package originally developed by Nick Williams at the Predictive Mineral Discovery Cooperative Research Centre (pmd*CRC), Geoscience Australia, uses the physical properties of minerals to provide bounds on estimates of the abundance of specified minerals in non-porous basement rocks. This approach is applicable to both estimates of density and magnetic susceptibility derived from 3D inversions of gravity and magnetic data as well as physical measurements on specimens or down-hole derived physical properties. This users guide descibes the history, installation and operation of the software package.

Vertical stress is one of the three principal stresses and is an important parameter in geomechanical studies that are focussed on the prediction of pore pressure, fracture gradients, and wellbore stability. Variations of the vertical stress magnitude can be attributed to variations in lithology or diagenetic history, localised uplift, and overpressures caused by disequilibrium compaction. This study uses wellbore data from 102 open-file petroleum wells to characterise vertical stress within the onshore Canning Basin of north-western Australia. Vertical stress magnitudes are interpreted from density logs and checkshot data and at 1 km depth below the ground surface range from 20.5 MPa km-1 to 25.0 MPa km-1 with a mean value of 22.1 MPa km-1 (s.d. = 1.0 MPa km-1). Significant variation is evident within the calculated stress magnitudes, and when presented spatially, three regions of elevated vertical stress are identified: the Barbwire Terrace, the Devonian Reef Complexes of the northern Lennard Shelf, and the Mowla Terrace. Lithology, abnormal pore pressures, and tectonic uplift are investigated as potential mechanisms of the observed variation. Although abnormal pore pressures are identified, no direct correlation between overpressured areas and elevated vertical stress magnitudes is observed. The Canning Basin has an extensive history of uplift; however, there is little evidence for significant recent inversion. While uplift is likely to exert some influence over vertical stress magnitudes in the Canning Basin, the primary cause is interpreted to be lithological; areas of elevated vertical stress magnitude are also areas where thick intervals of carbonate sediments are present. Appeared in The APPEA Journal 59, pages 364-382, 17 June 2019

This OGC WMS web service (generated by Geoserver) serves data from the Geoscience Australia Rock Properties database. The database stores the results of measurements of physical properties of rock and regolith specimens, including such properties as mass density, magnetic susceptibility, magnetic remanence and electrical conductivity. The database also records analytical process information such as method and instrument details where possible.

This OGC WFS web service (generated by Geoserver) serves data from the Geoscience Australia Rock Properties database. The database stores the results of measurements of physical properties of rock and regolith specimens, including such properties as mass density, magnetic susceptibility, magnetic remanence and electrical conductivity. The database also records analytical process information such as method and instrument details where possible.

The Geoscience Australia Rock Properties database stores the results measurements of scalar and vector petrophysical properties of rock and regolith specimens. Many are sourced from Geoscience Australia's mapping and research programs, but some are are compiled from published literature, university studies, the resources industry and State/Territory geological surveys. Measured properties include mass density, magnetic susceptibility, magnetic remanence, gamma, electrical conductivity and sonic velocity. The database also records analytical process information such as methods and instrument details wherever possible.

NEXIS (National Exposure Information System) Residential Dwelling Density web service is a set of four raster layers representing the density of residential dwellings across Australia at different scales and resolutions.

NEXIS (National Exposure Information System) Residential Dwelling Density web service is a set of four raster layers representing the density of residential dwellings across Australia at different scales and resolutions.

NEXIS (National Exposure Information System) Residential Dwelling Density web service is a set of four raster layers representing the density of residential dwellings across Australia at different scales and resolutions.