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  • The Australian Geological Survey Organisation (AGSO) flew an airborne geophysical survey of 69 086 line km covering the entire Cootamundra 1:250 000 map Sheet area in the Lachlan Fold Belt of New South Wales. The survey formed part of the National Geoscience Mapping Accord and was jointly funded by AGSO, Department of Primary Industries and Energy and the Geological Survey, New South Wales Department of Mineral Resources. The survey was flown along east-west flight lines, 250 metres apart at an altitude of 80 metres above ground level. AGSO flew the survey over two periods; from November to December 1997 and from February to March 1998. The total magnetic intensity, gamma-ray spectrometric and digital elevation model data collected during the survey, have been processed and are available for purchase. These data are sold as digital point located data, grids and hardcopy maps, by the Australian Geological Survey Organisation. Colour and greyscale pixel image maps are also available.

  • The Australian Geological Survey Organisation (AGSO) flew an airborne geophysical survey of 55,233 line kilometres over the Thackaringa and Redan 1:100 000 map Sheet areas on the Menindee 1:250 000 map Sheet area from 8 June to 5 August 1995. The survey was flown as part of the Broken Hill Exploration Initiative, a National Geoscience Mapping Accord project implemented by AGSO, the New South Wales Department of Mineral Resources and the Department of Minerals and Energy South Australia. The survey was flown along east-west flight lines spaced mainly 100 m apart (200 m in some areas) at a nominal altitude of 60 m above ground level. The total magnetic intensity, gamma-ray spectrometric and digital elevation model data which were collected during the survey, have been processed and are available for purchase, in both digital (point located data and gridded) and map form, from the Australian Geological Survey Organisation.

  • Absract for Indonesian Geophysics Conference (HAGI)

  • 22-1/F54-3/18 Contour interval = 2

  • Geoscience Australia (GA) has recently completed two regional-scale Airborne Electromagnetic (AEM) surveys: one in the Paterson Region, WA; and the other in the Pine Creek region, NT. These surveys provide AEM data at line spacings of 200 m to 6 km covering an area greater than 110 000 km2. The surveys were designed to promote more detailed investigations by the mineral exploration industry. An inherent risk in using AEM surveys is that the depth of penetration of the primary electromagnetic field is highly variable. Although forward modelling is undertaken before the AEM campaign, the depth to which we can reliably invert the AEM signal to generate conductivity models is not known until after the survey is flown. In order to estimate the penetration depth of the AEM surveys, we calculate the depth of investigation (DOI) based on the GA layered-earth inversion algorithm, which is influenced by both conductivity measurements and reference model assumptions. We define the DOI as the maximum depth at which the inversion is influenced more by the conductivity data than the reference model. We present the DOI as a 2D grid across both the Paterson and Pine Creek AEM surveys. Labelled the 'AEM go-map', the DOI grid helps to promote AEM exploration by decreasing risk when industry undertakes follow-up surveys within these regions.

  • The Olympic Cu-Au Province, of the eastern Gawler Craton, lies beneath the sedimentary sequences of the Stuart Shelf. Rocks of the basement are Late Archean metamorphics, and the Proterozoic Donington Suite, Hutchison Group, Wallaroo Group, Hiltaba Suite granitoids and mafic intrusives, and the Gawler Range Volcanics. Except for parts of the Gawler Range Volcanics, none of the basement crops out and is covered by sequences exceeding 3 km thickness, in places. Interpretation of units and structures was via gravity and airborne magnetic data. Some geological calibration was done by checking exploration drill logs or by examining the core. When core was examined, petrophysical properties were measured and used to constrain the interpretation. This map has been produced as a GeoPDF, which is an extension to the standard PDF file format viewed using Adobe Acrobat Reader. Layers can be turned off and on to customise the view of the data, similar to using Geographic Information System tools. In addition, GeoPDF maps are georeferenced to be compatible with other coordinated geographic data. Coordinate locations and distances can be retrieved automatically. A plug-in to view GeoPDF using Adobe Acrobat Reader is available as a free download ( http://terragotech.com/solutions/map2pdf_reader.php ).

  • The Moonta Subdomain forms the southern part of the Olympic Cu-Au province on the eastern margin of the Gawler Craton, and underlies most of the Yorke Peninsula and Spencer Gulf. The domain basement comprises metasediments and metavolcanics of the Palaeoproterozoic Wallaroo Group (~1760-1740 Ma) which were deformed and metamorphosed to upper greenschist-amphibolite facies during the Kimban Orogeny (~1720 Ma). These rocks were further deformed and intruded by granitoids and minor mafic intrusions of the Hiltaba Suite between about 1600 Ma and 1575 Ma. The Moonta Subdomain basement is highly prospective for iron oxide-Cu-Au mineralisation associated with the Hiltaba magmatic event. However outcrop of these basement rocks is limited almost entirely to narrow coastal exposures. The majority of the prospective basement is concealed by up to 100 metres of Neoproterozoic to Quaternary sediments, and geological mapping of the basement is largely limited to interpretation of geophysics (airborne magnetics, gravity, AEM) and drilling. This map has been produced as a GeoPDF, which is an extension to the standard PDF file format viewed using Adobe Acrobat Reader. Layers can be turned off and on to customise the view of the data, similar to using Geographic Information System tools. In addition, GeoPDF maps are georeferenced to be compatible with other coordinated geographic data. Coordinate locations and distances can be retrieved automatically. A plug-in to view GeoPDF using Adobe Acrobat Reader is available as a free download ( http://terragotech.com/solutions/map2pdf_reader.php ).

  • Geoscience Australia is custodian of ship-track magnetic and gravity data from close to 700 marine surveys conducted between 1960 and 2009. These data were last combined and levelled in the late 1990s. New levelling has been motivated by specific requirements within projects being conducted as part of the Australian Government's Energy Security Program (2006-2011). These projects rely on marine potential-field datasets to help constrain sediment thickness and basement architecture in remote offshore basins. Recently-levelled datasets cover: 1) the Capel and Faust basins, deepwater basins about 800 km off the east coast, and 2) the southwest margin of the Australian continent. The levelling involved the following steps: consistent computation of gravity anomalies; splitting lines into straight-line segments to facilitate cross-over computations; low-pass line filtering where necessary; editing to remove problematic ship-tracks; and levelling to minimise cross-over misties. Using methods developed by Intrepid Geophysics for the late-1990s Australia-wide work, magnetic data were levelled by minimising misclosures around loops and then gridded and merged with aeromagnetic data in onshore and near-shore areas. Gravity data were levelled using a polynomial technique and satellite-altimeter-derived gravity data as a reference surface. The resulting levelled datasets provide information at a higher-resolution than is available from satellite-derived gravity measurements or from global compilations of magnetic data. Despite this, the levelled datasets are limited to areas of specific scientific or exploration interest, which highlights the need for levelled datasets that cover the whole of Australia's marine jurisdiction.

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    The radiometric, or gamma-ray spectrometric method, measures the natural variations in the gamma-rays detected near the Earth's surface as the result of the natural radioactive decay of potassium (K), uranium (U) and thorium (Th). The data collected are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This Mt Anderson - McClarty Hills, WA, 2009 (North Canning 3) (P1212), radiometric line data, AWAGS levelled were acquired in 2009 by the WA Government, and consisted of 99192 line-kilometres of data at 400m line spacing and 60m terrain clearance. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data. This survey data is essentially levelled to AWAGS.