Iron (Fe) oxide mineralogy in most Australian soils is poorly characterised, even though Fe oxides play an important role in soil function. Fe oxides reflect the conditions of pH, redox potential (Eh), moisture and temperature in the soil environment. The Fe oxide mineralogy exerts a strong control on soil colour. Visible-near infrared (vis-NIR) spectroscopy can be used to identify and measure the abundance of certain Fe oxides in soil as well as soil colour. The aims of this paper are to: (i) measure the hematite and goethite content of Australian soils from their vis-NIR spectra, (ii) compare these results to measurements of soil colour, and (iii) describe the spatial variability of hematite, goethite and soil colour, and map their distribution across Australia. The spectra of 4606 surface soil sample from across Australia were measured using a vis-NIR spectrometer with a wavelength range between 350-2500 nm. We determined the Fe oxide content from characteristic absorptions of hematite (near 880 nm) and goethite (near 920 nm) and derived a normalised iron oxide difference index (NIODI) to better discriminate between them. The NIODI was generalised across Australia with its spatial uncertainty using sequential indicator simulation. We also derived soil RGB colour from the spectra and mapped its distribution and uncertainty across the country using sequential Gaussian simulations. The simulated RGB colour values were made into a composite true colour image and were also converted to Munsell hue, value and chroma. These colour maps were compared to the map of the NIODI and both were used for interpretation of our results. The work presented here was evaluated using existing studies on the distribution of Fe oxides in Australian soils.

Regolith materials spatially and chemically associated with various types of ore deposits, such as iron oxides, manganese oxides and gold deposits for example, have the potential to be mapped and characterised using remote sensing techniques. With the release of new state-scale multispectral data such as the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) Geoscience map of Western Australia (Figure 1), these applications may be tested and evaluated, along with identifying ore deposit types and characteristics best suited to using remote sensing techniques. A world-first continental scale ASTER mosaic and pre-competitive geoscience products for Australia are planned for public release in August 2012. The ASTER products are designed to provide broad scale mineral group information for mineral explorers at the continental to prospect scale. The product will be particularly useful for obtaining information on remote or difficult to access areas of Australia. ASTER data consists of 14 bands from Visible and Near Infrared (VNIR) light, through Short Wave Infrared (SWIR) and Thermal Infrared (TIR) encompassing different reflectance and emission spectras from the top few microns of material on the Earth's surface (Figure 2).

In late 2006, the Australian Government announced its Energy Security Initiative, allowing Geoscience Australia to initiate, among others, a major program of onshore activities [1]. An ambitious National Geochemical Survey of Australia (NGSA) project was launched in January 2007 as part of this program because until then Australia lacked a complete geochemical data coverage. Such a dataset informs on the concentrations and distributions of chemical elements in the near-surface environment. Building on methods developed during precursor pilot projects [2], NGSA targets catchment outlet (overbank) sediments as a uniform sampling medium. A shallow and a deeper level are being collected in 1390 catchments covering 91% of the country. Sampling is carried out by State and Northern Territory geoscience agencies following protocols described in a detailed Field Manual [3] and practiced during in-field training; all equipment and consumables are provided centrally. Dry and moist Munsell colours, soil pH, digital photographs and GPS coordinates are recorded in the field. In the laboratory, these transported, fine-grained regolith materials are dried and a split is archived for future use. Electrical conductivity and pH of 1:5 (soil:water) slurries, laser particle size distribution and infrared spectroscopy are measured on the remaining split. This split is further sieved into two grain-size fractions (<2 mm and <75 mm) for analysis by x-ray fluorescence (XRF), inductively-coupled mass spectrometry (ICP-MS) after total digestion (multi-element) as well as after aqua regia digestion (multi-element, including low level gold), and by specialised methods for platinum group elements, fluorine and selenium. As at February 2009, 78% of the samples have been collected and most analyses have been completed for the first 25% of samples. The project will contribute fundamental knowledge to the energy and mineral resources exploration industry by its completion in June 2011. This pre-competitve knowledge, used in combination with other datasets, can reduce exploration cost/risk by helping target more detailed activities. Spin-offs into other applications are also expected.

Regional seismic reflection data in hard rock areas contains more shallow information than might first be supposed. Here I use a subset of the 2005 Tanami Seismic Survey data to show that near surface features can be defined, including paleochannels, Palaeozoic basins and structures within the Proterozoic basement. Successful imaging depends on correct determination of refraction statics, including identification of refractor branches, and use of a floating or intermediate datum during seismic reflection processing. Recognition of steep stacking velocity gradients associated with surface referenced processing aids velocity analysis and can further delineate areas of thicker regolith in palaeochannels. The first arrival refraction analysis can also be applied in more detail to estimating thickness of regolith and depth to economic basement in areas of sedimentary cover.

The National Geochemical Survey of Australia (NGSA) project has collected catchment outlet sediment samples from 1315 sites located in 1186 catchments (~10% of which were sampled in duplicate) covering over 80% of Australia, in a collaborative venture between Geoscience Australia and the geoscience agencies of all States and the Northern Territory. At each site, composited samples were collected from two depth intervals: (1) the Top Outlet Sediment from 0-10 cm depth, and (2) the Bottom Outlet Sediment from 60-80 cm depth on average. In the laboratory, the samples were dried, homogenised and separated into two grain-size fractions: (1) a 'coarse' fraction (0-2 mm), and (2) a 'fine' fraction (0-75 um). All together, thus, 5260 samples were prepared for analysis. Bulk splits were also separated for the determination of bulk properties. Samples were analysed for up to 68 chemical elements after Total, Aqua Regia and Mobile Metal Ion digestion methods. Several quality control measures were taken throughout the project and the data quality was assessed in a separate report. This report used the acquired geochemical data to investigate the preliminary implications of this new national dataset on exploration for energy and mineral resources in Australia. This was mostly done by overlaying the NGSA data on coverages of known deposits and occurrences for selected commodities: uranium (U), thorium (Th), gold (Au), copper (Cu), lead (Pb), zinc (Zn) and Rare Earth Elements (REEs). For U, an attempt was made to distinguish between calcrete-related and intrusion-related deposit types, and a local case study in the Pine Creek area is also presented. For Zn, preliminary results from an investigation into discrete field modelling using concentration-area (CA) fractal plots are also presented. Coincidence of known mineral deposits and occurrences with elevated geochemical element concentrations in the same catchment are highlighted. Several catchments have elevated geochemical element concentrations in catchments with no known mineral deposits or occurrences, which provide potential targets for exploration. This technique constitutes a useful and rapid tool for area selection where further, more detailed exploration effort could be expended to test these geochemical anomalies.

Mapping and analysis of landscapes in Australia can now benefit from a continental mineral map coverage, helping to identify and characterise materials at the surface, with the recent release (August 2012) of the Satellite ASTER Geoscience Maps of Australia (http://c3dmm.csiro.au/Australia_ASTER/stage_1_geoscienceproductnotes.html). The new maps can provide mineralogical information on weathering, soils and regolith boundaries and compositions. The ASTER mosaic, made up of some ~3,500 60x60 km individual ASTER scenes, were produced by a multi-agency collaboration of Australian government partners. They represent the first of their kind: a continent-scale, public, web-accessible and GIS-compatible ASTER geoscience product suite. Led by CSIRO, Geoscience Australia along with several state government agencies, (including GSWA, GSQ, DMITRE and NTGS), have released 17 geoscientific products across the whole of Australia, with application to landscape analysis, environmental studies, mineral mapping and exploration, as well as soil-mapping and the agricultural sectors. Outcomes have included the formation of a platform for establishing national standards, geoscience product nomenclature, processing methods, accuracy assessments and traceable documentation. The ASTER bands are being used together with other complementary datasets (e.g. terrain indices, gamma-ray radiometrics) to build statistical predictive models on surface regolith geochemistry. This study is a preliminary investigation and assessment of how to use the new products for geomorphic applications, particularly landscape analysis and characterisation.

We describe the information content of soil visible-near infrared (vis-NIR) reflectance spectra and map their spatial distribution across Australia. The spectra of 4030 surface soil sample from across the country were measured using a vis-NIR spectrometer with a wavelength range between 350-2500 nm. The spectra were treated using a principal component analysis (PCA) and the resulting scores were mapped by ordinary point kriging. The largely dominant and common feature in the maps was the difference between the more expansive, older and more weathered landscapes in the centre and west of Australia and the generally younger, more complex landscapes in the east. A surface soil class map derived from the clustering of the principal components was similar to an existing soil classification map. We show that vis-NIR reflectance spectra: (i) provide an integrative measure to rapidly and efficiently measure the constituents of the soil, (ii) can replace the use of traditional soil properties to describe the soil and make geomorphological interpretations of its spatial distribution and (iii) can be used to classify soil objectively.

The National Geochemical Survey of Australia (NGSA) has collected samples from 1315 sites located in 1187 catchments (~10% of which were sampled in duplicate) covering over 80% of Australia. At each site, two depth ranges were sampled and two grain size fractions were separated, giving 5260 samples to be analysed. Samples were analysed for: 1 - Total content of multiple elements in Geoscience Australia's laboratories using x-ray fluorescence (XRF) and inductively coupled plasma-mass spectrometry (ICP-MS)</li> 2 - total content of fluoride (F) in commercial laboratories using ion specific electrode (ISE) 3 - total content of platinum group elements (PGEs) in commercial laboratories using fire assay and ICP-MS 4 - aqua regia soluble content of selenium (Se) in a commercial laboratory using ICP-MS 5 - aqua regia soluble content of multiple elements, including low-level gold (Au), in a commercial laboratory using ICP-MS 6 - ligand-based extractable content of multiple elements in a commercial laboratory using ICP-MS. The detailed procedures for analysing the NGSA samples in various laboratories are described.

Poster for the Australian Earth Sciences Convention 2010.

The National Geochemical Survey of Australia (NGSA) was initiated in late 2006, and details of progress were published, among others, in Caritat et al. (2009). The ultra-low density geochemical survey was facilitated by, and based on, overbank sediment sampling at strategic locations in 1186 catchments. Included in the analysis methods was a partial extraction method by the Mobile Metal Ion (MMI) technique (Mann, 2010) of sediment sampled at the depth of 0-10 cm, air-dried and sieved to <2 mm. The MMI method is based on solubilisation of adsorbed ions and potentially can provide a measure of bio-availability, as ions in natural soil pore waters are subject to solubility by solutions stronger in complexing ability than pure water, but not subject to soil phase dissolution as achieved by strong acid or total digestion methods. Of the ten elements considered essential for plant growth (Ca, Cu, Fe, K, Mg, Mn, N, P, S and Zn), only two (N and S) were not included in the 53 elements analysed after MMI extraction of the overbank samples. Comparison of a number of MMI concentrations for each element with the corresponding total analysis for the same soil samples provides an estimate of the recovery % by MMI in a similar manner to that used by Albanese (2008) to evaluate ammonium acetate-EDTA as a measure of bio-availability. Individual maps for the eight nutrients based on MMI analysis provide some very interesting and potentially useful information. For example, highest 'bio-available' Fe concentrations are not related to the Fe-rich soils and rocks of the Pilbara, but to high rainfall areas close to the coast, where processes akin to lateritisation are still taking place. The movement of Fe as Fe2+ and its subsequent oxidation to Fe3+ is not only important to agriculture, but on the east coast of Australia it has a number of environmental consequences in river systems. The distribution pattern for Mn .../...