Map of project area in southern Queensland and northern NSW

Map of project area in southern Queensland and northern NSW

The southern Thomson Orogen geology underlies the Channel Country in northwest New South Wales, and is one of the last major greenfield terranes in NSW. The Thomson Orogen has potential for arc- and ocean-crust-related gold and base metal deposits, while the area to the south of the orogen may have potential for Mississippi Valley-style zinc deposits. The prospective units are obscured by overlying Eromanga basin sediments, which present a significant impediment to exploration.

The Geological Survey of New South Wales (GSNSW) has made this terrane the focus of a series of projects since 2005. The primary objective is to lower mineral exploration risk by developing an effective means of exploring through the cover in the Thomson Orogen. This achievement can be measured by an increase in exploration investment in the area.

Previous surveys and interpretations completed by GSNSW since 2005 involved seismic, gravity, geochemical and airborne geophysical data. Recent GSNSW regional mapping campaigns in the Koonenberry-Tibooburra and Cobar-Bourke regions have contributed detailed information from outcrops around the margins of the project area.

The Geological Survey of New South Wales is participating in two major collaborative studies that will:

  • help define variations in the depth to basement and the nature of basement
  • advance understanding of the structural framework, geological history and tectonic elements of the southern Thomson Orogen in NSW.

The projects include acquisition of new geophysical data and targeted geochronological, structural and mineral systems studies. The pre-competitive data, interpretations and reports will benefit a range of users to assess mineral potential; support mineral exploration and reduce the risks; guide land use planning; and support groundwater management.

Stratigraphic drilling

The recent stratigraphic drilling program including borehole completion reports

The collaborative studies

  1. The Southern Thomson Orogen NCF Project was a 3-year project between GSNSW, Geoscience Australia and the Geological Survey of Queensland to acquire and interpret multi-disciplinary geophysical, geochemical and geological data. This project started in 2014 and includes geophysical acquisition programs (airborne electromagnetics, magnetotellurics, gravity), detailed analytical studies of stratigraphic units from core and surface samples, structural interpretation, and regolith and landscape studies.

    Results are being released periodically by Geoscience Australia and GSNSW:
  2. An ARC Linkage research program commenced in 2014 together with The University of Newcastle, Geological Survey of Queensland, The University of Queensland and Queensland University of Technology. Titled 'Southern Thomson Orogen: a missing link in the Tasmanides', it aims to test competing geodynamic models for the evolution of the Thomson Orogen. This 3-year program includes research projects at PhD, MSc and Hons levels, and is generating new data and concepts about Tasmanides geology. Coordinated geochronological, structural and geochemical studies at these universities are targeting key geological questions. Six Honours theses and one PhD about NSW geology have been completed (refer to the Southern Thomson ARC Linkage Project). Other projects, including further Masters studies, are in progress. Outcomes will have implications for the mineral prospectivity of the southern Thomson Orogen and the greater Tasmanides.

    The results of many these student projects will be included in the Australian Journal of Earth Sciences (AJES) Special Volume 65/7+8 to be released later in 2018.

Both collaborative studies will provide information about the style and timing of deformational events; the nature and hierarchy of faulting; and the extent, lithology and geochronology of rock units. Comparisons will then be made with the Lachlan Orogen to the south, and the Delamerian Orogen to the west, to better understand the tectonic history of this portion of the Tasmanides.

Contact

Chris Folkes, Project Leader