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  • turned off record due to the lack of metadata, author/custodian and the product itself is un-locatable

  • Potential field data were used to constrain or support the geological interpretations of the 2006 and 2007 North Queensland seismic data. Potential field forward modelling, potential field inversions and worms of potential field data all supported the interpretations of the seismic data.

  • Data and results from the 2003 Gawler Craton seismic survey were released at Gawler Craton: State of Play 2004 and Seismic Workshop, held in Adelaide last August. The survey consisted of two nearly orthogonal lines centred on the giant Olympic Dam Fe oxide Cu-Au deposit; 02GA-OD1, a north-south line 193 km long and 02GA-OD2, an east-west cross line 57 km long.

  • This report is a description of velocity data acquired during the summer of 2006/07 on Geoscience Australia's seismic marine reflection, refraction and potential field survey GA302 over the Capel and Faust Basins, Lord Howe Rise. The survey was the final phase of the Australian Government's Big New Oil initiative commenced in 2003 to support acreage release in frontier basins. Previous data over the region are sparsely located, and the present survey will provide explorers with high quality data acquired and processed to modern standards. The Lord Howe Rise is thought to be a continental fragment detached from Australia during the formation of the Tasman Sea. The Capel and Faust Basins are of interest as possible frontier petroleum provinces, and the present work is aimed at improving the confidence of sediment thickness estimation, a critical parameter in evaluating of prospectivity. The study reviews the seismic reflection data from survey GA302, the sonobuoy refraction data acquired, and the stacking velocities from the seismic reflection processing.

  • Iron oxide-copper-gold (IOCG) systems, and their related magnetite-apatite systems, are suggested to form in orogenic belts (e.g., Cloncurry, Andean magmatic arc, Urals) and extensional settings (e.g., St François Terrane, Missouri). Even so, the tectonic setting of arguably the most important of the IOCG class of the deposits, the giant world-class Olympic Dam deposit in South Australia, has been uncertain to date. It has previously been used as an example of the IOCG in an anorogenic intracontinental setting. The region has no outcrop as it is covered by Neoproterozoic sedimentary successions exceeding 5 km thick, in places. Given its economic significance and importance in defining the IOCG mineral deposit class, resolving the tectonic setting of Olympic Dam is crucially important. To address this, two orthogonal deep seismic reflection traverses, centred on the Olympic Dam deposit, were recorded to 18 s TWT. The nearly north-south line, 193 km long, oriented as near to regional dip-direction, defined by potential-field data, as land access would allow, sounded units of the Archaean-Proterozoic Gawler Craton and a possible allochthanous Proterozoic terrane. The shorter east-west cross-line (57 km) provides control on the three dimensional geometry of the major structures and gives information about some out-of-plane structures imaged by the north-south traverse. The seismic data show that the Olympic Dam deposit occurs in a fold- and thrust-belt, formed over a number of periods of orogeny, which was probably subject to compressional tectonics at the time of IOCG mineralisation. In the north of the study area, the upper crust, of the crystalline basement, shows south-dipping reflectors, interpreted as shear zones that cut through crust of sub-horizontal reflections. To the south, the upper crust and lower crust have reflectivity indicating thrusting to the south and, or, southwest, toward the interior of the Gawler Craton. However, the upper crustal deformation is decoupled from lower crustal deformation at a layer of sub-horizontal reflectors interpreted, by their reflection-amplitudes, to contain more mafic rocks than the regions above and below. This layer is up to 5 km thick and mostly un-deformed, except where it is duplexed. The duplexes appear to form the loci of strain partitioning in the upper crust. The lower crust of the centre of the study area contains fewer reflections, and appears anomalous but homogenised compared with the crust to the north and south. Imaging of the cover-successions shows a previously unknown Adelaidean rift, which has been partially inverted.

  • Most crustal-scale seismic reflection surveys use single profiles, and are an attempt to create two-dimensional images of three-dimensional structures. CMP data are stacked and migrated assuming that the seismic energy comes from within the plane of the section. However, three-dimensional topography on an interface results in out-of-plane reflected energy coming into the plane of the section, and energy from the plane of the section being lost from the plane of the section. Interfaces with low to moderate relief image as a zone of reflections in which the top of the zone reproduces the shape of the interface within the plane of the reflector fairly accurately, and energy lower in the zone of reflections is from out of the plane. However, if the relief on the interface is significant, reflections from shallower levels of the interface out of the plane of the section can arrive before those from deeper parts of the interface in the plane of the section. This makes interpreting both the position of the interface in the plane of the section and the amount of relief on the interface difficult. Three-dimensional topography on the interface out of the plane of the section generates more diffractions than does two dimensional topography. The amount and nature of diffracted energy in stacked data is a qualitative indicator of structure in and out of the plane of the section. For a synthetic three-dimensional interface with relief ranging over a number of wavelengths, reflection amplitudes up to twice the primary reflection strength were observed; destructive interference produced very weak reflections elsewhere. The absolute amplitude of the strongest reflections is therefore a poor indicator of impedance contrast for reflectors with significant three-dimensional topography.

  • This data set consists of processed seismic reflection data for line 01AGS-NY1 from the 2001 Northern Yilgarn seismic survey (L154), Western Australia. Line 01AGS-NY1 commenced in the Yilgarn Craton (Leonora) and extended to the east into the Officer Basin (east of Lake Yeo). The data were acquired by the Australian National Seismic Imaging Resource (ANSIR) using vibratory sources at a nominal 60 fold coverage. The seismic data are provided as SEG-Y files of stack and migrated data to 4 seconds and 18 seconds two-way time, at a sample interval of 4 milliseconds. CDP range is 1985 to 20860 with 20 metre CDP interval. SEG-Y header information, CDP coordinates as eastings and northings, and a pdf image of the migrated 18 second seismic section are also included. The line, migrated section images and further information on this data can be obtained from the <a href="http://www.pmdcrc.com.au" target="_blank">pmd*CRC</a> website.