Geoscience Australia (GA) has recently released regional airborne electromagnetic data (AEM) in two survey areas of the Pine Creek region. The Woolner Granite-Rum Jungle survey in the western part of the region was flown using TEMPESTTM and the Kombolgie survey in the eastern part was flown using VTEMTM. These data assist in mapping geological features deemed to be critical for fertile unconformity-related uranium and sandstone-hosted uranium systems. These mapped features in combination with other datasets are used to assess the prospectivity of uranium systems.

Predictive maps of the subsurface can be generated when geophysical datasets are modelled in 2D and 3D using available geological knowledge. Inversion is a process that identifies candidate models which explain an observed dataset. Gravity, magnetic, and electromagnetic datasets can now be inverted routinely to derive plausible density, magnetic susceptibility, or conductivity models of the subsurface. The biggest challenge for such modelling is that any geophysical dataset may result from an infinite number of mathematically-plausible models, however, only a very small number of those models are also geologically plausible. It is critical to include all available geological knowledge in the inversion process to ensure only geologically plausible physical property models are recovered. Once a set of reasonable physical property models are obtained, knowledge of the physical properties of the expected rocks and minerals can be used to classify the recovered physical models into predictive lithological and mineralogical models. These predicted 2D and 3D maps can be generated at any scale, for Government-funded precompetitive mapping or drilling targets delineation for explorers.

This professional opinion assesses the viability of utilising the priority aquifer target GWMAR1 to secure Broken Hill's water supply, both as an extractive only scheme and as a conjunctive use scheme employing Managed Aquifer Recharge as a key component. This work comes under the arrangements of the Broken Hill Managed Aquifer Recharge Project Phase 3a Memorandum of Understanding. The report addresses, with confidence levels, the following issues: Option 1: Groundwater Extraction Only. This includes an estimation of the water storage capacity and ambient groundwater salinity of the GWMAR1 priority target and the Jimargil sub-area. Different confidence levels are attached to these two estimates, reflecting the focus of work to date on the Jimargil sub-area. Broader groundwater quality issues will also be discussed. An assessment is also made of the issues with respect to direct groundwater extraction as the sole option for securing Broken Hill's water supply for a minimum of 3 years (approximately 30GL). Option 2 assesses the use of the GWMAR1 priority aquifer as part of a conjunctive water supply incorporating Managed Aquifer Recharge. This includes an assessment of the suitability of the priority MAR target at Jimargil based on the National MAR Risk Assessment Guidelines. The report also includes specification of the remaining information gaps and potential risks to a project to utilise the aquifer for (1) Groundwater extraction and (2) a conjunctive supply utilising Managed Aquifer Recharge. Broken Hill and Menindee. The report also includes a short summary of communities in Australia that currently rely on Managed Aquifer Recharge to supply their potable water, and management issues associated with this supply, and future considerations to a possible implementation phase of providing water security to Broken Hill and Menindee from a regional aquifer.

The Ord is one of the largest rivers in northern Australia and is located in the Kimberley region of Western Australia. In this study we show that the lower Ord landscape near Kununurra in Western Australia consists of a large scale ancient landscape, possibly pre-Cambrian, being exhumed from beneath flat-lying Cambrian to Carboniferous cover rocks. Additional post-Permian landscapes are being formed by this process. The Ord Valley alluvium is of late Pleistocene to Holocene in age and consts off upward fining gravels, sands and clays infilling an inset valley profile. The Ord River initially flowed to the sea via the keep River estuary, however a major avulsion, possibly due to sedimentatain topping a low point in the surrounding valley walls, occurred possibly as recently as 1,800 years ago. As a result to mouth of the Ord shifted some 100 km to the east, to Cambridge Gulf, its course through the former alluvial plain and along the new course across the coastal plain was incised, and a scabland formed across the low point of Tararar Bar. This association of very ancient (pre-Paleozoic) landscape elements and by thin, very young weathering profiles and young sedimentary accumulations in alluvial valleys is paradoxical in the broader Australian pattern where very ancient landscape elements are associated with ancient sedimentary infill and weathering profiles.

Geoscience Australia (GA) is a leading promoter of airborne electromagnetic (AEM) surveying for regional mapping of cover thickness, under-cover basement geology and sedimentary basin architecture. Geoscience Australia flew three regional AEM surveys during the 2006-2011 Onshore Energy Security Program (OESP): Paterson (Western Australia, 2007-08); Pine Creek-Kombolgie (Northern Territory, 2009); and Frome (South Australia, 2010). Results from these surveys have produced a new understanding of the architecture of critical mineral system elements and mineral prospectivity (for a wide range of commodities) of these regions in the regolith, sedimentary basins and buried basement terrains. The OESP AEM survey data were processed using the National Computational Infrastructure (NCI) at the Australian National University to produce GIS-ready interpretation products and GOCADTM objects. The AEM data link scattered stratigraphic boreholes and seismic lines and allow the extrapolation of these 1D and 2D objects into 3D, often to explorable depths (~ 500 m). These data sets can then be combined with solid geology interpretations to allow researchers in government, industry and academia to build more reliable 3D models of basement geology, unconformities, the depth of weathering, structures, sedimentary facies changes and basin architecture across a wide area. The AEM data can also be used to describe the depth of weathering on unconformity surfaces that affects the geophysical signatures of underlying rocks. A number of 3D models developed at GA interpret the under-cover geology of cratons and mobile zones, the unconformity surfaces between these and the overlying sedimentary basins, and the architecture of those basins. These models are constructed primarily from AEM data using stratigraphic borehole control and show how AEM data can be used to map the cross-over area between surface geological mapping, stratigraphic drilling and seismic reflection mapping. These models can be used by minerals explorers to more confidently explore in areas of shallow to moderate sedimentary basin cover by providing more accurate cover thickness and depth to target information. The impacts of the three OESP AEM surveys are now beginning to be recognised. The success of the Paterson AEM Survey has led to the Geological Survey of Western Australia announcing a series of OESP-style regional AEM surveys for the future, the first of which (the Capricorn Orogen AEM Survey) completed acquisition in January 2014. Several new discoveries have been attributed to the OESP AEM data sets including deposits at Yeneena (copper) and Beadell (copper-lead-zinc) in the Paterson region, Thunderball (uranium) in the Pine Creek region and Farina (copper) in the Frome region. New tenements for uranium, copper and gold have also been announced on the results of these surveys. Regional AEM is now being applied in a joint State and Commonwealth Government initiative between GA, the Geological Survey of Queensland and the Geological Survey of New South Wales to assess the geology and prospectivity of the Southern Thomson Orogen around Hungerford and Eulo. These data will be used to map the depth of the unconformity between the Thomson Orogen rocks and overlying sedimentary basins, interpret the nature of covered basement rocks and provide more reliable cover thickness and depth to target information for explorers in this frontier area.

This publication is an outcome of a meeting entitled "Transient and Induced Variations in Aeromagnetics" that was held in Canberra on 18 September 1996 to discuss the effects of rapid fluctuations of the geomagnetic field on high-resolution aeromagnetic surveys and airborne detection systems. The meeting brought together people from the exploration and mining industry, Defence, Government Science, and Universities with common interests in the nature and applications of external magnetic fields and of the electromagnetic properties of the Earth's crust and oceans. Inevitably, much of the focus was on the use of base stations and tie lines for correcting for the influence of geomagnetic fluctuations in survey data. However, the discussion ranged widely from magnetospheric physics to the magnetic effects of ocean swells at aeromagnetic elevations.

A PowerPoint presentation showing regional interpretations of data from the Frome airborne electromagnetic survey, presented at a workshop on 30 November 2011 at the University of Adelaide, South Australia

Short article describing a new method of defining depth of investigation for airborne electromagnetic surveys

Funded by the Australian Government's Onshore Energy Security Program the Pine Creek airborne electromagnetic (AEM) survey was flown over the Pine Creek Orogen and parts of the McArthur, Victoria River and Daly Basins in the Northern Territory between August 2008 and 24th May 2009. The survey comprises three survey areas: Kombolgie, east of Kakadu National Park; Woolner Granite, near Darwin; and, Rum Jungle, west of Kakadu National Park. The Pine Creek survey was the second regional AEM survey flown in Australia. The survey cost of $3 745 000 included a 29 900 line km flown at various line spacings (555m, 1666m and 5000m) and covered approximately 74 000 km2. The Woolner Granite and Rum Jungle survey areas were flown by Fugro Airborne Surveys Pty. Ltd. (FAS), for Geoscience Australia (GA), using the TEMPESTTM time-domain AEM system. The Kombolgie survey area was flown by Geotech Airborne Pty. Ltd VTEMTM time-domain AEM system. The Pine Creek AEM survey was designed to deliver reliable, pre-competitive AEM data to promote exploration for uranium, copper-gold, base metals, tin and nickel in both brownfields and greenfields areas. The survey area hosts several uranium deposits, including the Ranger Uranium Mine, Rum Jungle and Nabarlek.

During 2008 and 2009, and under the Australian Government's Onshore Energy Security Initiative, Geoscience Australia acquired airborne electromagnetic (AEM) data over the Pine Creek Orogen of the Northern Territory. The survey area was split into three areas for acquisition. VTEM data was acquired in the Kombolgie area east of Kakadu National Park (this data set) between August and November 2008. TEMPEST data was acquired west of Kakadu National Park with the area split in two to facilitate the use of two aircraft: the Woolner Granite area in the north was acquired between October and December 2008; and the Rum Jungle area adjoining to the south, was acquired between October 2008 and May 2009. The main purpose of the surveys was to provide additional geophysical/geological context for unconformity style uranium mineral systems and thereby promote related exploration. The survey data will also provide information on depth to Proterozoic/Archean basement, which is of general interest to explorers, and will be used as an input into ground water studies in the region. This dataset includes the subscriber company data K1 K2 and K3.