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Paterson AEM Survey EM Vision 3D Inversion Data and Release Notes: Kintyre areaNote: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2. Dataset citationANZLIC unique identifier: ANZCW0703016595 Title: Paterson AEM Survey EM Vision 3D Inversion Data and Release Notes: Kintyre area CustodianCustodian: Geoscience Australia Jurisdiction: Australia DescriptionAbstract: Phase-2 conductivity estimates were generated using the 1D Geoscience Australia layered earth inversion algorithm (GA-LEI) have been released to the public domain (Hutchinson et al 2010). The GA-LEI has been shown to provide useful mapping of subsurface conductivity features in the Paterson for example paleovalleys, unconformities and faults. GA-LEI interpretations have been supported by independent borehole conductivity logs, and lithological drill-hole information. A Geoscience Record Geological and energy implications of the Paterson Province airborne electromagnetic (AEM) survey, Western Australia, summarises the AEM data, processing, inversions, interpretation and implications for exploration for uranium and other commodities using the 1D GA-LEI. There is an inherent assumption in the GA-LEI algorithm that the earth can be represented by a set of 1D layers, which extend to infinite distance in the horizontal plane. This layered earth assumption has some limitations, and has been demonstrated to create artefacts when applied to heterogeneous 3D geological features (eg: Ellis, 1998). 3D inversion methods ideally, overcome some of the limitations of 1D inversion methods, reducing artefacts of a 1D earth. A subset of the regional Paterson AEM dataset was provided to TechnoImaging to create a 3D inversion using EMVision? software with the intention of comparing the GA-Lei 1D inversion with the 3D TechnoImaging inversion. The data subset was a combination of GA owned data and Cameco owned data, and the cost of inversion by TechnoImaging was shared by both parties. At the time of flying the Paterson AEM survey, 3D inversions required much greater computational resources than 1D methods. 3D inversions require the solution of as many large systems of equations. In addition, a large (although sparse) sensitivity matrix is computed, which increases memory requirements, and the process must be repeated for multiple iterations (Ellis 2002; Wilson et al. 2006; Raiche et al 2007). This computational expense had generally limited the practical application of 3D inversions to AEM datasets, and restricted its use a general mapping tool. The EMVision? inversion generated by TechnoImaging presents a method of running a 3D inversion, with a runtime comparable to 1D inversion methods. The EMVision? algorithm uses a moving footprint to limit the number of data points needed as input to the inversion at any one location. A background conductivity model is chosen to represent the far-field response of the earth, and the data points within the AEM footprint are treated as anomalies with respect to the background. A detailed description of the EMVision? inversion can be found in Cox et al. (2010). In 2010, it was determined a comparison of the GA-LEI with, at the time, the new 3D inversion methodology would be useful. A selection of the Paterson AEM survey (Costelloe, 2010) around the Kintyre deposit was chosen as a test case for this 3D inversion. The data selection consisted of 17 lines of 15 km in length (total 255 line km), with 200 m line spacing as shown in Figure 1. Under the terms of the agreement between Cameco and Geoscience Australia here was a moratorium on the data release until 2012. ANZLIC search words:
Spatial domain:
Geographic extent name: SF51-10 RUDALL - SF51-10 - 1:250 000 Map Series - Australia Geographic extent polygon: 120.6 -20.1, 122.6 -20.1, 122.6 -22.4, 120.6 -22.4, 120.6 -20.1, Note: The format for each Geographic extent name is: Name - Identifier - Category - Jurisdiction (as appropriate) See GEN Register
Data currencyBeginning date: 2007-09-14 Ending date: 2012-11-11 Dataset statusProgress: Complete Maintenance and update frequency: Not Known Access
Access constraints: Creative Commons Attribution 3.0 Australia Licence Free Data DownloadData qualityLineage: The AEM survey data were acquired by the airborne geophysical survey contractors Fugro Airborne Surveys. The inversion data were processed and produced by the authors, and details are provided in the attached report. The data was inverted, delivered to the public domain as a part of the OESP. An interpretation report was created. This 3D inversion was generated from the contractor supplied data. Positional accuracy: Positioning was via post-processed differential GPS methods. Horizontal positional accuracy of the data is approximately 1 metre (standard deviation). Attribute accuracy: The data have been acquired and processed to a standard of best practice as of the year 2008. More sophisticated processing algorithms may be applied to these data should they become available. Logical Consistency: Not applicable. Completeness: The dataset includes data and products released by Geoscience Australia for the Paterson AEM survey. Contact information
Metadata informationMetadata date: 2013-03-08 Additional metadataMetadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703016595.html Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703016595.xml . Authors:Costelloe, M.T. Fitzpatrick, A. Roach, I.C. Hutchinson, D.K. |
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