Airborne Electromagnetic
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As part of its Energy Security Initiative, the Australian Government allocated Geoscience Australia $59 million in August 2006, to undertake a five-year Onshore Energy Security Program. This is designed to deliver precompetitive geoscience data and scientifically-based assessments to reduce the rick in exploration for onshore energy resources, including petroleum, uranium, thorium and geothermal energy. The work is being conducted in collaboration with the State and territory geological surveys and is scheduled for completion in June 2011.
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The National Geochemical Survey of Australia project represents an essential component of the Australian Government's Onshore Energy Security Initiative. The national geochemical survey involves the use of field-tested methods for collection and analysis of transported regolith samples representative of catchments covering most of Australia. The project is a collaboration between Geoscience Australia and State and Northern Territory geoscience agencies, which will provide an internally consistent geochemical dataset useful for calibration and ground-truthing of airborne radiometrics surveys. The survey also will help to fill gaps in current airborne radiometrics and geochemical coverages of Australia, provide multi-element characterisation and ranking of radiometric anomalies and aid in first-order investigation of the nature of geothermal hot-spots. As a result it will support and add value to numerous other Onshore Energy Security Initiative projects and have wider applications in mineral exploration and in environmental assessment and management. This report details the methodology underpinning the determination of the theoretical sampling points using terrain and hydrological analysis; and the protocols for sample collection. It will be used for knowledge transfer during training sessions for the State and Northern Territory field parties who also will receive field equipment and consumables which will ensure there is consistent sampling throughout the project. A digital data entry template has been designed to enable efficient and consistent in-field data capture, which also will streamline data entry into Geoscience Australia's corporate databases.
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The record is a presentation given by Adrian Fisher to staff of the Aditya-Birla Nifty copper mine and to staff at the Geological Survey of Western Australia, August 2007. It describes the planning behind the Paterson AEM survey, to be acquired in 2007-2008.
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The Natural Fields EM Forum was held in Brisbane, Queensland, Australia, on February 26, 2012, in conjunction with the ASEG 22nd International Geophysical Conference & Exhibition 2012. The forum was organised to review the current state of development of natural field EM methods (NFEM), being those methods that utilise the ambient electromagnetic field rather than deploying an additional active source as an element of a survey. NFEM methods are used to acquire data from which various parameters can be obtained to help interpret the electrical characteristics of the subsurface.
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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.
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More recently the O'Farrell government has called for expressions of interest to explore for uranium across NSW. Fugro Airborne Services Pty Ltd also called for expressions of interest in flying a large TEMPEST AEM survey in NSW covering the NSW Curnamona Province and portions of the Murray-Darling Basin and Lake Eyre Basin, abutting the SA border, to complement the Frome AEM Survey. The following is a brief summary of some of the main points discussed and presented during 3 presentations at the NSWGS on 19 September 2012, and in follow-up discussions on 20 September 2012. Approximately 40 people attended the three presentations. A discussion after the talks centred around using AEM in NSW for regional mapping including for uranium, porphyry copper-gold systems and massive sulphide systems. PowerPoint presentations were left with NSWGS. Three abstracts describing these presentations are included at the end of this document.
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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.
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Summary reporting of AEM Survey results and interpretations to AEM workshop attendees in Alice Springs March 24th 2011.
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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.
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The continuing world demand for potash (potassium salts) is driving a new exploration boom in the Australian minerals industry for this valuable resource, listed by Geoscience Australia (GA) as a strategic commodity (Mernagh 2013). The Food and Agriculture Organization of the United Nations (FAO) predicts a rising demand for fertilizers, with potash demand increasing at 3.7% per annum (FAO 2012), and Rabobank predicts that demand will exceed supply by up to 100% by 2020 (Rabobank 2012). This demand is driving the application of airborne electromagnetics (AEM) to map salinity as a proxy for potential potash resources in salt lakes. This short paper describes a few of the applications and is written in response to an industry request to GA for information on how AEM might be used to explore for potash.