2015
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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.
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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.
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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.
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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.
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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
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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.
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Deep seismic reflection profiling confirms that the Paleo- to Mesoproterozoic Mount Isa mineral province comprises three vertically stacked and partially inverted sedimentary basins preserving a record of intracontinental rifting followed by passive margin formation. Passive margin formation commenced around 1670 Ma and concluded at 1655 Ma before being followed by plate convergence, crustal shortening and basin-wide inversion at 1640 Ma in both the 1730-1640 Ma Calvert and 1790-1740 Ma Leichhardt superbasins. Rifting was re-established no later than 1635 Ma with formation of the 1635-1575 Ma Isa Superbasin and continued up to ca. 1615 Ma when extensional faulting ceased and a further episode of basin inversion commenced. The 1575 Ma Century Pb-Zn ore-body is hosted by syn-inversion sediments deposited during the initial stages of the Isan Orogeny with basin inversion accommodated on east- or northeast-dipping reactivated intrabasinal extensional faults and footwall shortcut thrusts. These structures extend to considerable depths and served as fluid conduits during basin inversion, tapping thick syn-rift sequences of immature siliciclastic sediments floored by bimodal volcanic sequences from which the bulk of metals and mineralizing fluids are thought to have been sourced. Basin inversion and fluid expulsion at this stage were entirely submarine consistent with a syn-sedimentary to early diagenetic origin for Pb-Zn mineralisation at, or close to, the seafloor. Farther east, a change from platform carbonates to deeper water continental slope deposits (Kuridala and Soldiers Cap groups) marks the position of the original shelf break along which the north-south-striking Selwyn-Mount Dore structural corridor developed. This corridor served as a locus for strain partitioning, fluid flow and iron oxide-copper-gold mineralization during and subsequent to the onset of basin inversion and peak metamorphism in the Isan Orogeny at 1585 Ma. An episode of post-orogenic strike-slip faulting and hydrothermal alteration associated with the subvertical Cloncurry Fault Zone overprints west- to southwest-dipping shear zones that extend beneath the Cannington Pb-Zn deposit and are antithetic to inverted extensional faults farther west in the same sub-basin. Successive episodes of basin inversion and mineralization were driven by changes in the external stress field and related plate tectonic environment as evidenced by a corresponding match to bends in the polar wander path for northern Australia. An analogous passive margin setting has been described for Pb-Zn mineralization in the Paleozoic Selwyn Basin of western Canada.
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Abstract for 2015 Conference of the Specialist Group of Tectonics and Structural Geology. Presentation of 3D Models in the Grampians-Stavely Zone, western Victoria. 3D geological models have been produced for two major geological units in the Grampians-Stavely Structural Zone in western Victoria. The Grampians-Stavely Zone is located on the eastern limit of the Cambrian-aged Delamerian Orogen in Victoria (VandenBerg et al., 2000; Crawford et al., 2003; Miller et al., 2005) and several belts of Cambrian igneous rocks with arc affinities have been recognised within this zone (Crawford and Keays, 1978; Buckland, 1987; VandenBerg et al., 2000; Crawford et al., 2003); including the exposed Mount Stavely Volcanic Complex (Buckland, 1987). The Mount Stavely Volcanic Complex, together with other belts of Cambrian igneous rocks, have been interpreted as fault slices of a now mostly buried magmatic arc system referred to as the Stavely Arc (Schofield et al., 2015; Cayley et al., in prep.). In order to address the outstanding geological questions and challenges to exploration in the Grampians-Stavely Zone, Geoscience Australia and the Geological Survey of Victoria established the collaborative Stavely Project in 2013. The Stavely Project forms part of the broader UNCOVER initiative (Australian Academy of Science, 2012) and aims to provide the fundamental framework for discovery in the Grampians-Stavely Zone. This is done using a mineral systems-based approach (Wyborn et al., 1994) through the provision of pre-competitive geoscientific data. This approach involves characterising the subsurface geology, recognising favourable geological environments for the formation of major mineral systems, identifying important elements that demonstrate mineral systems potential, and understanding the depth and nature of cover across the region. This study will focus on understanding the depth and nature of specific cover units across the region.
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The mineral exploration industry is used to very high sample densities (100s to 1000s of samples/km2) for geochemical exploration in order to define drill targets. Lately, geoscience organisations in many countries have been geochemically mapping increasingly larger areas at progressively lower sampling densities (1 site/100 km2 to 1 site/18,000 km2). A single ore body is too small a target and can not be expected to be discovered at such low sample densities; indeed several deposits could be hidden within a 100 km x 100 km grid cell. However, mineral systems, which include all geological ingredients and processes necessary for the generation of mineral deposits, form much larger targets that could be identified even at such low sampling densities. Examples from some European low density geochemical surveys where patterns emerged that may have implications for mineral exploration are shown and discussed. It is concluded that low density geochemical mapping holds great promise in the early stages of mineral exploration programmes in guiding subsequent effort into the right regions. Interpretation of these maps, however, may need a different approach than that used in classical, high density mapping exercises, where only 'high values' of certain metals are the traditional target.
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The `Isotopic Domain Boundaries of Australia data set is based on an interpretation of the recently released Neodymium depleted mantle model age map of Australia (GA Record 2013/44). The isotopic map of Australia was produced by gridding two-stage depleted mantle model ages calculated from Sm-Nd isotopic data for just over 1490 samples of felsic igneous rocks throughout Australia. The resultant isotopic map serves as a proxy for bulk crustal ages and accordingly allows the recognition of possible geological domains with differing geological histories. One of the major aims of the Neodymium depleted mantle model age map, therefore, was to use the isotopic map (and associated data) to aid in the recognition and definition of crustal blocks (geological terranes) at the continental and regional scale. Such boundaries are recognisable by regional changes in isotopic signature but are hindered by the variable and often low density of isotopic data points. Accordingly two major procedures have been adopted to locate the regional distribution of such boundaries across the continent. In areas of higher data density (and high confidence), such as the Yilgarn Craton of Western Australia, isotopic data alone was used to delineate crustal domains. In areas of moderate data density (and corresponding moderate confidence) (smoothed) boundaries of known geological provinces were used as a proxy for the isotopic boundary. For both high and moderate data densities identified crustal boundaries were extended (with corresponding less confidence) into regions of lower data density. In areas of low data density (and low confidence) boundaries were either based on other geological and/or geophysical data sets or were not attempted. The latter was particularly the case for regions covered by thick sedimentary successions. Two levels of confidence have been documented, namely the level of confidence in the location of the isotopic domain boundary, and the level of confidence that the boundary is real. The `Isotopic Domain Boundaries of Australia map shows the locations of inferred boundaries of isotopic domains, which are assumed to represent the crustal blocks that comprise the Australia continent. The map therefore provides constraints on the three dimensional architecture of Australia, and allows a better understanding of how the Australian continent was constructed from the Mesoarchean through to the Phanerozoic. It is best viewed as a dynamic dataset, which will need to be refined and updated as new information, such as new isotopic data, becomes available.