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Mining of the Broken Hill Ag-Pb-Zn deposit has substantially modified what was originally a positive anomalous mass. When an airborne gravity gradiometer (AGG) survey was flown over the Broken Hill region in early 2003, the measured response reflected the modified mass distribution. To answer the questions ?What was the original response of the orebody?? and ?Would this response have been detected had the survey been flown prior to mining??, an estimate of the changes in response brought about by mining activities was made and added to the survey data to produce an image of the pre-mining gravity response. To estimate the change in response, a 3D model of the mined portion of the deposit was built. An estimate of the change in mass due to mining activities was made and this mass was distributed with uniform density throughout the model. The gravity and vertical gravity gradient response of the orebody model was then calculated, filtered to match the characteristics of the AGG data and added to the observed survey data. The `corrected? data show distinct gravity and gravity gradient highs over the northern and southern parts of the orebody which hosted the bulk of the reserves. Although the anomalous response is close to the noise levels of the survey data, we can conclude that the AGG survey would have detected an anomalous response from the Broken Hill orebody had the survey been flown prior to mining. However, there are other geological features in the survey area that produce similar anomalies, notably a number of amphibolite units.
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Poster for 2008 CO2CRC Symposium.
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The National Dynamic Land Cover Dataset (DLCD) classifies Australian land cover into 34 categories, which conform to 2007 International Standards Organisation (ISO) Land Cover Standard (19144-2). The DLCD has been developed by Geoscience Australia and the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES), aiming to provide nationally consistent land cover information to federal and state governments and general public. This paper describes the modeling procedure to generate the DLCD, including machine learning methodologies and time series analysis techniques involved in the process.
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This paper focuses on the thermal modelling conducted in the Cooper Basin and Tattapani hot spring regions in order to highlight the latest work being done by Geoscience Australia to improve our understanding of the temperature and fluid flow fields in areas away from direct measurements.
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Conference volume and CD are available through the Petroleum Exploration Society of Australia
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Presentation made to the Second Symposium on Resource Assessment Methodologies organised by the Potential Gas Committee and the US Geological Survey. Discussed methodology used at Geoscience Australia and presented some recent results from the Bonaparte and Browse basins.
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The southwest corner of Western Australia consists of Protozoic geology with the area undergoing no tectonic activity in the last 40Ma. It has not been glaciated in the last 20Ma and has had a cool dry climate for at least 200ka, thus providing an ideal environment to preserve fault scarps. High resolution DEM data has been used to identify over 50 new features that are thought to be scarps of surface rupturing earthquakes. Half of these scarps have been the subject of some field work with one new feature being fully verified. Using recently developed fault scaling relations the fault length and displacement are used to estimate the magnitude and, in many cases, identifying multiple events. This has been used to generate a neotectonic earthquake catalogue. Non-extended stable continental region (SCR) and extended continental crust (ECC) and have separate catalogues The SCR catalogue is considered to have a magnitude of completeness (Mc) of M6.5 with ~55 earthquakes of M6.5 or greater. The data has typical truncated GR recurrence characteristics, with a slope (b) of 0.9-1.0, between magnitude 6.5 and 6.9, and rapid decrease in recurrence above M6.9. SCR data has an asymptote of M7.2 suggesting a Mmax of M7.1-M7.3. The ECC data has a Mc of M7.2 and has 15 events of this magnitude or greater. The recurrence rapidly decreases above M7.4 with an asymptote of M7.6 suggesting a Mmax of M7.5-M7.7. The large number of SCR events gives us confidence in the proposed Mmax of M7.2.
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