From 1 - 10 / 591
  • The Surface Hydrology Points (Regional) dataset provides a set of related features classes to be used as the basis of the production of consistent hydrological information. This dataset contains a geometric representation of major hydrographic point elements - both natural and artificial. This dataset is the best available data supplied by Jurisdictions and aggregated by Geoscience Australia it is intended for defining hydrological features.

  • Understanding the distribution of temperature is generally the first step in a geothermal exploration process. With the exception of a few areas of hot springs, there are no surface manifestations of temperature anomalism in Australia. The Australian continent has no active magmatism, the heat flow regime is conductive, and thick layers of insulating sediments are necessary to obtain elevated temperature suitable for electricity generation or process heat. The coverage of direct temperature measurements and surface heat flow determinations is described in Gerner and Holgate (2010). The majority of these measurements were made by petroleum and groundwater drilling, and is characterised by sparsity and poor distribution. An alternative approach is needed to provide indications of temperature at depth in uncharacterised areas, so that the whole of Australia can be evaluated for geothermal prospectivity.

  • The Allen Osborne Associates Dorne Margolin type T chokering antenna has been used extensively in the International Global Navigation Satellite System Service (IGS) tracking network for over 20 years. This antenna type, using the IGS naming convention, ''AOAD/M\_T'', was predominately installed at the original IGS sites in the late 80's, early 90's, to track signals from the Global Positioning System satellite constellation, and is still in use at operational sites today. The antenna is also used as the standard reference for relative to absolute antenna calibration conversions, which hold an important role in the history of IGS antenna calibration values. It is suspected that there may be a previously unknown subgroup of antennas that maintain a different set of phase center values which, if true, will change antenna calibration values in the IGS ANTEX file and possibly bias the International Terrestrial Reference Frame as is it currently defined.

  • The period between 480 Ma and 410 Ma in the Lachlan Orogen of southeastern Australia is the most important metallogenically in eastern Australia, having contributed over half of the mineral wealth in the Tasman Element (or Orogen). The period of intense mineralisation is interpreted to be related to the development of the Lachlan Orocline at the very end of the Ordovician and into the Silurian. Formation of this orocline was triggered by the oblique accretion of the VanDieland crustal fragment, which includes the present day Melbourne Zone in Victoria and western Tasmania. Prior to this event, eastern Australia was characterised by a west-dipping convergent margin with associated small- to moderate-sized volcanic-hosted massive sulphide (VHMS: Girilambone, Mount Windsor and Balcooma) and calc-alkaline porphyry Cu-Au deposits (Copper Hill, Marsden) with ages of 480 Ma to 450 Ma. Orocline development was initiated by the accretion of the VanDieland at ~445 Ma, which was accompanied orogenic gold mineralisation in Victoria (Bendigo, Ballarat, etc). Importantly, because of the geometry of interaction, gold mineralisation did not extend into present-day New South Wales. As accretion of this block continued, the Tasman continental margin began to wrap around VanDieland to form the Lachlan Orocline. At this time, extension associated with orocline formation to the north initiated low degree partial melting and post-collisional alkaline magmatism. Alkaline porphyry Cu-Au deposits in the Macquarie volcanic province (Cadia and Northparkes) formed during this extension at ~435 Ma. Continued extension and the re-establishment of west-dipping subduction in the Silurian saw a second phase of VHMS mineralisation at 425-415 Ma, and granite-related Sn and Mo mineralisation at 430-410 Ma. The concept of the Lachlan Orocline can be used to identify new areas of mineral potential and the extension of known areas undercover.

  • Medhavy Thankappan1, Matthew Garthwaite1, Peter Meadows2, Nuno Miranda3, Adrian Schubert4 and David Small4 1Geoscience Australia, Canberra, Australia 2BAE Systems Applied Intelligence, Essex, United Kingdom 3European Space Agency, Frascati, Italy 4 Remote Sensing Laboratories, Department of Geography, University of Zurich, Switzerland Geoscience Australia has permanently deployed 40 trihedral corner reflectors in the Surat Basin, Queensland, Australia, covering an area of approximately 20,000 km2. The array of corner reflectors was constructed as part of the AuScope Australian Geophysical Observing System (AGOS) initiative to monitor crustal deformation using Interferometric Synthetic Aperture Radar (InSAR) techniques. The array includes 34 corner reflectors of 1.5m, 3 reflectors of 2.0m and 3 reflectors of 2.5m inner leg dimensions. Through the design process and the precision manufacturing techniques employed, the corner reflectors are also highly suitable for calibration and validation of Synthetic Aperture Radar (SAR) data acquired by satellites. Nine of the 1.5m corner reflectors in the AGOS array had their Radar Cross Section (RCS) individually characterised at the Defence Science and Technology Organisation's outdoor ground reflection range, prior to permanent deployment in the Surat Basin. The RCS measurements for the corner reflectors were carried out at X and C-band frequencies for both horizontal and vertical transmit-receive polarisations, and at a range of elevation and azimuth alignments. The results from the characterisation of the corner reflectors show that the measured RCS values were 2 decibels less than theoretical values at C-band and 5 decibels at X-band. The field performance of the AGOS corner reflectors has been studied using SAR data from the TerraSAR-X, RADARSAT-2, Sentinel-1A and ALOS-2 satellites. This paper presents the results of the corner reflector field performance at X, C and Lband SAR frequencies which the satellites cover. As part of the Copernicus Sentinel-1A satellite commissioning and routine phases, the European Space Agency's Mission Performance Centre has also undertaken exercises using data from the Sentinel-1A satellite to assess the field performance of the AGOS corner reflectors. Radiometric calibration results from that evaluation are presented here with recent geometric calibration and validation results for Sentinel-1A products from the Terrain Observation with Progressive Scans (TOPS) mode. The current configuration for most corner reflectors in the AGOS array is set to serve calibration requirements for a broad range of SAR missions on ascending orbital passes, and therefore may not be optimal for any single mission in particular. However, the design allows for mission-specific corner reflector alignment if needed, as in the case of the 2.5m and 2.0m reflectors which have specifically been aligned to support calibration of the L-band SAR instrument on ALOS-2. The permanently deployed AGOS corner reflector infrastructure presents an opportunity for independent calibration and comparison of SAR instruments on current and future satellite missions, and is considered an important Australian contribution to the global satellite calibration and validation effort.

  • Updated USB drive containing GA-reports, maps, and flythroughs (2008-2015) in digital format to be handed out as promotional material at AMSA 2015 conference.

  • This USB has been produced for promotional purposes and will be handed out (free) at domestic and international conferences. The USB contains a selection of reports, flyers, maps and data. Products are grouped into 4 categories: Reports and Brochures, Mineral Deposits, Surface Geology and Geophysical Data, and Data Visualisation Tool.

  • This USB has been produced for promotional purposes and will be handed out (free) at domestic and international conferences. The USB contains a selection of reports, flyers, maps and data. Products are grouped into 4 categories: Reports and Brochures, Mineral Deposits, Surface Geology and Geophysical Data, and Data Visualisation Tool.

  • Mines and wines Conference 2015 booth display. Panels include: - National geophysical datasets - Current geophysical acquisition 2015 - Tasmanide evolution Late Neoproterozoic to Cretaceous time-space plot -Southern Thomson Project AEM interpretations - Southern Thomson Project new data acquisition and surface geochemistry results - Stavely Project description - Stavely project data products: stratigrpahic drilling and depth to basement predictions

  • Up to 90% of Australia's uranium resources occur in deposits of Paleo-Mesoproterozoic (~1.9-1.5 Ga) age, including hematite granitic breccias at Olympic Dam in South Australia and unconformity-related deposits in the Northern Territory. Published fluid inclusion data for unconformity-related uranium deposits suggest that uranium was transported by low- to moderate temperature (<250°C), Na-Ca-Mg brines of seawater evaporation origin. Secular changes in geochemical behaviour of uranium through Earth history are well known. The most prominent changes are attributed to stepped oxygenation of the Earth's atmosphere. This process resulted in oxidation of U(IV) to U(VI) forming highly soluble aqueous uranyl complexes. The oxygenation is thought to have occurred as two stepwise increases in atmospheric oxygen at the beginning and end of the Proterozoic, at ~2.3 and ~0.6 Ga. High aqueous mobility of uranium after the second oxygenation event is globally recorded by elevated concentrations of uranium in organic-rich shales. Large-scale processes of crustal enrichment of uranium in the Proterozoic rocks pre-dating the second oxygenation events can be explained by a number of endogenic factors, including high paleogeothermal gradients and large volumes of uranium-enriched granitic rocks emplaced at shallow crustal levels. Other decisive factors leading to the formation of the giant uranium deposits may be of exogenic origin. One would be a unique combination of moderately elevated levels of atmospheric oxygen and high levels of atmospheric CO2, with the latter exceeding present day levels at least by ~1.5 orders of magnitude. Under these conditions, for a wide range of surficial waters and groundwaters, uranium aqueous speciation would be dominated by carbonate uranyl complexes (e.g., UO2CO3), with uranyl concentrations proportional to CO2 pressures. Another exogenic factor is Paleoclimatic conditions favourable to the formation of evaporative basins suggested as sources of uraniferous fluids. In the present study, we examine these two exogenic factors quantitatively, modelling solubility of uranium in natural waters and progressively evaporated seawater at boundary conditions characteristic of Paleo-Mesoproterozoic atmosphere (log fCO2 > 2, log fO2 ~ 1.4). The modelling indicates that Paleo-Mesoproterozoic environment could be especially favourable for mobilisation of uranium in weathering profiles due to elevated content of atmospheric CO2. Evaporation of seawater is indeed a chemically feasible process that might have determined the initial (Na-Mg) composition of brines associated with uranium mineral systems. The range of the Na-Ca-Mg brine compositions reported in the literature can be explained by 'sampling of spatially separate parts of the same brine factory characterized by different degrees of seawater evaporation and the extent of the subsequent brine interaction with Ca-rich basin and basement lithologies via Na-Ca and Mg-Ca exchange reactions.