ABSTRACT: Building on method developments achieved during a series of precursor pilot projects, the National Geochemical Survey of Australia (NGSA) project targets catchment outlet (overbank) sediments as a uniform sampling medium. These transported, fine-grained materials are collected (from a shallow and a deeper level) near the lowest point of 1390 catchments, which cover 91% of the country. Dry and moist Munsell® colour, soil pH and electrical conductivity and pH of 1:5 (soil:water) slurries are recorded and laser particle size analysis and infrared spectroscopy are performed. The dried samples are sieved into two grain-size fractions (<2 mm and <75 mm) that are analysed by x-ray fluorescence (XRF) and inductively-coupled mass spectrometry (ICP-MS) (multi-element, total analyses), by ICP-MS after aqua regia digestion (multi-element, including low level gold), and specialised methods for platinum group elements, fluorine and selenium. At the time of writing, 78% of the samples have been collected and most analyses are completed for the first 25% of samples. The project is due for completion in June 2011.

The 1:250 000 maps show the type and distribution of 51 regolith-landform units with unique dominant regolith-landform associations, and are a subset of the 205 mapping units on the six 1:100 000 maps. These units are distinct patterns of recurring landform elements with characteristic regolith associations. Geomorphic symbols indicate the location and type of geomorphic activity. The maps present a systematic analysis and interpretation of 1:89 000 scale 1973 RC9 aerial photography, 1:100 000 scale topographic maps (AUSLIG), and field mapping data. High resolution (250m line spacing) airborne gamma-ray spectrometry and magnetics (Geoterrex) were used where applicable

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.

The area northwest of Elura mine, northwest of Cobar, has diverse surficial materials reflecting a complex landscape history. This paper examines some of this history and its possible effects on surface geochemical sampling programs.

Recently, continental-scale geochemical surveys of Europe and Australia were completed. Thanks to having exchanged internal project standards prior to analysing the samples, we can demonstrate direct comparability between these datasets for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extracted elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH. By comparing these new datasets to one another, we can learn lessons about continental-scale controls on soil geochemistry and about critical requirements for global geochemical mapping. Although the median soil compositions of both continents are overall quite similar, the Australian median values are systematically lower, except for SiO2 and Zr. This reflects the generally longer and, locally more intense weathering in Australia (median Chemical Index of Alteration values are 72 and 60% for Australia and Europe, respectively). We found that element concentrations typically span 3 (and up to 5) orders of magnitude on each continent. The comparison of 2 continental geochemical surveys shows that the most critical requirement for global geochemical mapping is good analytical quality. Only where a comprehensive quality control program, including field and laboratory duplicates, internal project standards and Certified Reference Materials, is implemented and documented, are the results credible and comparable with other datasets.

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.

The floodplain of the lower Balonne River is in the upper reaches of the Murray Darling Basin. The region has been extensively developed for agriculture, in particular irrigated cotton, and is highly productive. Multidisciplinary investigations to inform land management generated extensive sets of remotely sensed data including Landsat TM, airborne gamma-ray radiometrics, aerial photography, ASTER imagery, and digital elevation models. These datasets provided the basis for regolith and geomorphic mapping. The wealth of data has allowed characterisation of the lower Balonne River system which is typical of many of the dryland rivers of southern Queensland. The geomorphic map of the lower Balonne floodplain has 8 major units based on landform and geomorphic processes. Bedrock consists of the slightly deformed and extensively weathered marine Cretaceous Griman Creek Formation. Coincident with erosion and weathering, Paleogene quartz gravels were deposited and are now extensively cemented and preserved as remnants forming zones of inverted relief. Much of the present landscape consists of a series of juxtaposed depositional units that have infilled an incised valley system. The different depositional units show the palaeo-Balonne River migrating to the west. This is interpreted to be a result of tectonic depression and tilting to the west, causing avulsion and anastomosing of the palaeo-channels. The modern Balonne River system consists of a number of easily recognised segments. In the north, the modern channel is incised as a single channel. To the south the channel opens out onto an anastomosing plain with branching and reconnecting small-scale channels. Source bordering dunes, currently inactive, have also formed along the western and eastern sides of the modern river and are prominent in large dunes in the south along the present Moonie River. Their absence in older landscape elements points to increasing aridity over time in the river system.

Legacy product - no abstract available

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 National Geochemical Survey of Australia (NGSA) aims to collect samples from 1529 sites located in 1390 catchments (10% of which are sampled in duplicate) covering over 90% of Australia. At each site, two depth ranges are sampled, giving 3058 samples to be processed. Each sample results in 13 individually packaged sub-samples, meaning that 39,754 separate containers will be prepared, labelled, delivered to the laboratories or archived during the sample preparation phase of the project. Any excess fraction in the processing streams is kept for potential future use. The detailed procedures for preparing the NGSA samples in the laboratory are described with an overview of Quality Assessment/Quality Control and Operational Health and Safety measures also provided. There are three main parts to the sample preparation protocol. The first part is the Bulk Sample stream. The sample is received from the field, weighed, dried (for a minimum of 48h at 40°C) and sieved through a 4.75 mm mesh to remove any foreign material. The sample is then homogenised and split into two halves. One half is sealed and set aside for archiving for future analyses/investigations. The other half is split into sub-samples or aliquots for: 1. laser particle size analysis (LPSA), pH 1:5 (soil:water) and electrical conductivity (EC) 1:5 (soil:water) analysis; and 2. X-ray diffraction (XRD) analysis. The remainder of the bulk material is sieved through a 2mm mesh, and split into two portions (~20% and ~80%), which are processed in the following two streams. The second part is the Coarse Fraction stream. In this stream, the ~20% split of <2 mm sample prepared above is further split to prepare two aliquots for: - platinum group element (PGEs) analysis; and - gold (Au) analysis after aqua regia (AR) leach. The third part is the Fine Fraction stream. In this stream, the ~80% split of <2 mm sample prepared above is sifted using small stainless steel riffle splitters. The sample <75 um fraction is split into 5 different aliquots (splits) for different analyses. These aliquots are ranked in order of decreasing priority.