Authors / CoAuthors
Roach, I.C.
Abstract
The geology of the southern Thomson Orogen is poorly understood due to extensive cover of Mesozoic and Cenozoic sedimentary basins and regolith. Small outcrops of the southern Thomson Orogen are exposed along the Eulo Ridge (south Qld) and in the southwest near Tibooburra (NSW). Cover is of varying thickness and overlies a pre-Cretaceous-age palaeotopography with much greater relief than the present-day landscape. Proximal to these regions the thickness of cover is estimated to be < 200 m, which is within current economic exploration and mining depths. The southern Thomson Orogen is true 'greenfields' country. Although the mineral potential of the region is largely unknown, the north-eastern Thomson Orogen is well mineralised (e.g., Thalanga and Charters Towers), as is the Koonenberry region to the southwest (e.g., Tibooburra and Milparinka) and the Lachlan Orogen to the south (e.g., Cadia and Cobar). In order to encourage exploration investment in the southern Thomson Orogen, Geoscience Australia (GA), the Geological Survey of Queensland (GSQ) and the Geological Survey of New South Wales (GSNSW) have commenced a three-year collaborative project (the Southern Thomson Orogen Project - STOP) to synthesise existing and collect new pre-competitive geoscience data. The first stage of the project has synthesised existing geology and geophysics (magnetic, gravity and seismic data) to produce a new, seamless solid geological map of the Paleozoic basement across the state border. This is supported by the collection of new isotopic age dating samples from industry drill holes in the region to assess magmatic, metamorphic and mineralisation ages. These new samples will also be used to assess the potential mineral systems present in the southern Thomson Orogen, the prospectivity of the region and to conduct a gap analysis. Secondly, new surface geochemical samples have been collected over the Eulo Ridge to complement other low sampling density samples collected by the Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME) and as part of the National Geochemical Survey of Australia (NGSA). Early results from these samples highlight the use of surface samples and weak acid digestion to map the distal dispersion footprints of large mineralisation systems and bedrock terrains. The third stage of the project is to collect new geophysical data across the region to assess the depth of cover over the Eulo Ridge and to map lithospheric architecture. This involves collecting new airborne electromagnetic (AEM), gravity and magnetotelluric (MT) data. To date, 4267 line kilometres of new AEM data have been collected in the area. Over the Eulo Ridge, 3352 line kilometres was collected as a regional survey with east-west flight lines of 5000 m line spacing. This survey was designed to map the basement-cover interface across the Eulo Ridge, map basement geological units and potentially locate conductive targets in the basement. Two AEM traverses were also collected: from Gongolgon (NSW) to Thargomindah (Qld); and from Louth (NSW) to Eulo (Qld), of 915 total line kilometres. These two traverses are complemented by the acquisition of ~3550 new gravity stations at 333 m station spacing and ~200 new broadband MT stations at 5 km station spacing (in progress November - December 2014). The combined AEM, gravity and MT datasets will be used to model the lithospheric architecture of the southern Thomson Orogen and to reassess the Thomson Orogen-Lachlan Orogen boundary. A program of detailed audio frequency MT (AMT) acquisition is also underway to map geological structures across the Eulo Ridge in Queensland. The combined results will be synthesised and integrated into a precompetitive geoscience data package to encourage exploration investment. Interim products and datasets will be released throughout the project, with the final results delivered to industry in 2016.
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nonGeographicDataset
eCat Id
82479
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61 Mary Street None
Brisbane
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4000
Australia
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
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- External PublicationAbstract
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2014-01-01T00:00:00
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