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.

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.

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.

Provides an overview of the Project in the context of the Onshore Energy Security Program in advance of the presentations dealing with the acquisition, data, procedures and interpretation results of the survey.

This powerpoint was presented at a workshop in Alice Springs March 2011. The goal of the Pine Creek AEM survey is to characterise the electromagnetic response of Paleoproterozoic rocks, particularly graphitic units adjacent to Archean granite domes, and map these units in regions of extensive cover, such as the Woolner Granite, and Daly River Basin areas. The project will also attempt to map key sub-surface unconformities and structures which may have influenced mineralising fluids. Objectives To map unconformity and palaeochannel uranium host rocks To map the thickness of Kombolgie Subgroup rocks (depth to prospective interface) To map graphitic basement conductors To map the thickness of regolith cover.

Summary reporting of AEM Survey results and interpretations to AEM workshop attendees in Alice Springs March 24th 2011.

Conceptual MAR targets in the Broken Hill region were identified in previous investigations (Lewis et al., 2008; Lawrie et al., 2009a). In the BHMAR Phase 2 study, the project team is required to make recommendations on the presence and suitability of potential MAR sites with an 80% confidence level. While this will be attempted through a combination of AEM, borehole analysis and seismic reflection data acquisition, AEM is the prime dataset required to map the aquifer targets in 3D.