In most circumstances the conventional radioelement ratio method is sufficient for the enhancement of the differences between radioelement concentrations across map areas. However, there are areas where the range of radioelement concentration values are such that the ratio image is dominated by one or other of the radioelements. In this paper we demonstrate that, in some areas, the use of these ratios can be enhanced through suitable normalisation of the radioelement data prior to the calculation of ratios.

The aim of the NPE10 exercise is the continuation of the multi - technology approach started with NPE09. For NPE10, a simulated release of radionuclides was the trigger for the scenario in which an REB-listed seismo-acoustic event with ML between 3.0 and 4.8 was the source. Assumptions made were: A single seismo-acoustic signal-generating underground detonation event with continuous leak of noble gas, radionuclide detections only from simulated release. Using atmospheric transport modelling the IDC identified 48 candidate seismo-acoustic events from data fusion of the seismo-acoustic REBs with radionuclide detections. We were able to reduce the number of candidate seismo-acoustic point sources from 48 to 2 by firstly rejecting events that did not appear consistently in the data fusion bulletins; secondly, reducing the time-window under consideration through analysis of xenon isotope ratios; and thirdly, by clustering the remaining earthquakes and aftershocks and applying forward tracking to these (clustered) candidate events, using the Hy-split and ARGOS modelling tools. The two candidate events that were not screened by RN analysis were Wyoming REB events 6797924 (23-Oct) and 6797555 (24-Oct). Event 6797555 was identified as an earthquake on the basis of depth (identification of candidate depth phases at five teleseismic stations); regional Pn/Lg and mb:Ms - all indicating an earthquake source. Event 6797924, however, was not screened and from our analysis would constitute a candidate event for an On-Site Inspection under the Treaty.

Geoscience Australia is a proscribed agency of the Australian Government, and has been acquiring precompetitive geophysics over the Australian continent and making it available to industry and researchers for over fifty years. Geophysical methods are especially important for effective exploration in Australia because the ancient landscape has been deeply weathered and fresh rocks are concealed beneath a thick layer of weathered material, referred to as regolith. The Onshore Energy Security Program is Geoscience Australia's latest precompetitive program and is designed to reduce risk in exploration for Australia's onshore hydrocarbon, uranium, thorium, and geothermal energy resources. The program will acquire and deliver pre-competitive geophysical and geochemical data as well as geological interpretations and other value-added products for the exploration industry.

The Radiometric Map of Australia dataset comprises grids of potassium, uranium, and thorium element concentrations, and derivatives of these grids, that were derived by seamlessly merging over 550 airborne gamma-ray spectrometric surveys in the national radioelement database

Spectral data from airborne and ground surveys enable mapping of the mineralogy and chemistry of soils in a semi-arid terrain of Northwest Queensland. The study site is a region of low relief, 20 km southeast of Duchess near Mount Isa. The airborne hyperspectral survey identified more than twenty surface components including vegetation, ferric oxide, ferrous iron, MgOH, and white mica. Field samples were analysed by spectrometer and X-ray diffraction to test surface units defined from the airborne data. The derived surface materials map is relevant to soil mapping and mineral exploration, and also provides insights into regolith development, sediment sources, and transport pathways, all key elements of landscape evolution.

The use of airborne hyperspectral imagery for mapping soil surface mineralogy is examined for the semi-arid Tick Hill test site (20 km2) near Mount Isa in north-western Queensland. Mineral maps at 4.5 m pixel resolution include the abundances and physicochemistries (chemical composition and crystal disorder) of kaolin, illite-muscovite, and Al smectite (both montmorillonite and beidellite), as well as iron oxide, hydrated silica (opal), and soil/rock water (bound and unbound). Validation of these hyperspectral mineral maps involved field sampling (34 sites) and laboratory analyses (spectral reflectance and X-ray diffraction). The field spectral data were processed for their mineral information content the same way as the airborne HyMap data processing. The results showed significant spatial and statistical correlation. The mineral maps provide more detailed surface compositional information compared with the published soil and geology maps and other geoscience data (airborne radiometrics and digital elevation model). However, there is no apparent correlation between the published soil types (i.e. Ferrosols, Vertosols, and Tenosols) and the hyperspectral mineral maps (e.g. iron oxide-rich areas are not mapped as Ferrosols and smectite-rich areas are not mapped as Vertosols). This lack of correlation is interpreted to be related to the current lack of spatially comprehensive mineralogy for existing regional soil mapping. If correct, then this new, quantitative mineral mapping data has the potential to improve not just soil mapping but also soil and water catchment monitoring and modeling at local to regional scales. The challenges to achieving this outcome include gaining access to continental-scale hyperspectral data and models that link the surface mineralogy to subsurface soil characteristics/processes.

The Radiometric Map of Australia shows the distribution of potassium (% K), uranium (ppm eU) and thorium (ppm eTh) over Australia. A suite of image enhancement and data integration techniques can be used to enhance the value of these data for both mineral exploration and environmental mapping. Gradient-enhanced ternary and pseudo-colour image enhancements are now routinely used for the presentation and interpretation of gridded radioelement data. Where digital elevation data are available, these colour representations can be draped over the elevation data to form 3D perspective views, or hill-shaded derivatives of the DEM can be embedded into the ternary imagery as an intensity component. These are useful because the radioelement response can then be interpreted within the context of the relative position of anomalous features in the landscape. However, subtle variations in the concentrations of K, U, and Th are best interpreted using the ratios of the radioelements. The U/Th and U2/Th ratios are important indicators of uranium mineralization. The Th/K ratio is widely used for the detection of several styles of mineralization associated with K alteration. For the interpretation of map data, classification and clustering methods can be used to assist pattern recognition and are useful for the rapid assessment of large multivariate datasets. Automatic edge detection procedures can be used to speed up the annotation of unit boundaries. Residual modelling techniques can be used to highlight potential anomalies in the data.

The Onshore Energy Security Program (OESP) announced by the Australian Government in 2006 is a major initiative to encourage exploration for energy resources in Australia. Geoscience Australia will receive funding of $59 million over five years for data acquisition and scientific programs focussed on petroleum, uranium, thorium, and geothermal energy systems. National scale surveys such as the Australia Wide Geophysical Survey (AWAGS) will provide uniform, objective data for assessing the energy potential of terrains across the continent. Geological provinces considered prospective for energy commodities are being targeted by regional projects based around the acquisition of seismic\MT and other data. A mineral-systems approach is being used to assess the uranium and geothermal prospectivity of the Mt Isa and Georgetown regions of north Queensland, and interpret the results of an extensive seismic\MT acquisition program. Interpretation of these data is providing new insights into these provinces which have been under-explored for energy.

<p>In February 2009, Geoscience Australia released a new national radiometric map and dataset. This improved radiometric map, shows the distribution of potassium (K), uranium (U) and thorium (Th) at the Earth's surface as measured using the airborne gamma-ray spectrometric method. The gridded data that underpin the map cover over 80 % of the Australian continent at 100m spatial resolution. These data were calibrated to be consistent with an Australian radioelement datum based on an Australia wide airborne geophysical survey (AWAGS2) completed in 2008, which was conducted under the Australian Government funded Onshore Energy Security Initiative. AWAGS provides the baseline for stitching and levelling of all publicly available airborne radiometric (and magnetic) surveys across Australia, which are of a range of ages and qualities, and for future airborne surveys. The new grids of K, eTh and eU can be used to reliably compare the radiometric signatures observed over different parts of Australia, enabling the assessment of key mineralogical and geochemical properties of bedrock and regolith materials from different geological provinces and regions across the continent. These data support a range of different applications including exploration, geological mapping, geomorphological studies and environmental mapping. </p> <p>Presented at AusIMM Uranium Conference, Darwin, 10 June 2009.</p>