Northern Australia Geochemical Survey

Map showing the distribution of copper in the Northern Australia Geochemical Survey (NAGS) samples over the Tennant Creek — Mt Isa study area. This is from the results of the MMI™ extraction (the sediment 0-2 mm fraction).

The Northern Australia Geochemical Survey (NAGS) project is a low-impact, low-density geochemical survey, designed to determine the regional distribution of chemical elements within soils. Such knowledge provides a basis for informed decision making about regional land use, agriculture, mineral and energy resource potential. NAGS aims to advance methods and approaches originally developed by the National Geochemical Survey of Australia (NGSA; Caritat and Cooper, 2011) to systematically characterise the chemical nature of Australian soils and the processes that control their composition. This includes interpretation of the results of low-density geochemical surveys as a potential technique to locate "blind" mineral deposits buried under younger rocks. The resulting dataset also provide an excellent environment baseline dataset, which can be used to assess the impact of any future development in the area.

The NAGS project is targeting transported soil samples, collected on the floodplains of large water catchments.

The project focused on the Tennant Creek—Mt Isa region in the Northern Territory and Queensland, with one sample representing approximately 500 km2. The sample collection followed a cut-down version of the NGSA routine (only the top 0-10 cm depth of the soil profile is sampled).

To extract the maximum amount of geochemical information, the samples have been analysed for more than 60 elements using state-of-the-art analytical techniques.

Progress

Aerial view of the Barkly Tablelands, an area of the Northern Australia Geochemical Survey.

In 2017 soil samples from 780 sites were acquired in the Tennant Creek—Mt Isa region in the Northern Territory and Queensland. To access sampling sites in the harsh remote areas, two helicopters were used to transport field crews to these locations. The samples were processed for chemical analyses in a purposefully set up laboratory at the Centre for Appropriate Technology facility in Alice Springs.

Analysis of the samples have been completed at Geoscience Australia and external laboratories using a variety of techniques.

Outputs

Locations of the Northern Australia Geochemical Survey sites in the Tennant Creek—Mount Isa region in Northern Territory and Queensland.

  • Publicly available datasets of quality-controlled data and associated metadata. Two data releases from the project are now available: data release I and data release II. These datasets include:
    • Information on the sampling sites (catchments and sample locations);
    • Analytical data obtained from the samples by Geoscience Australia and external laboratories:
      • Bulk sample properties (Munsell colour, pH and EC);
      • Results of XRF analyses and ICP-MS analyses for the coarse (< 2 mm) and fine (<75 mm) fraction of the samples;
      • Results of ICP-MS analyses of the MMI™ extractions (0-2 mm);
      • Results of ICP-MS analyses of the Aqua Regia digestion of coarse and fine fraction samples;
      • Results of Fire Assay analyses for platinum group elements of coarse and fine fraction samples
  • Digital map images for (1) individual chemical elements that passed quality control and assurance requirements and for (2) principal components for the element datasets compiled in this study. The complete datasets can be downloaded from Geoscience Australia Data and Publications database: data release I and data release II.
  • In-depth interpretation of the current data will be reported in forthcoming publications.
  • Reports and digital maps summarising the project results; presentation of results to stakeholders at workshops and conferences.
  • Recommendations on using low-density (1 site per >500 km2) soil geochemistry in Australia as a tool to aid mineral exploration in areas covered by rocks younger than mineralisation.

Collaborations

The project is being undertaken in collaboration with the Geological Surveys of the Northern Territory and Queensland. Further collaboration with industry, academia and other government and research organisations will enhance the type of data collected and the quality and breadth of analysis and data interpretation.

Sample processing for the first stage of the project has been completed in collaboration with the Alice Springs Aboriginal and Torres Strait Islander not-for-profit company, the Centre for Appropriate Technology (CAT). Partnering with CAT has given Geoscience Australia the opportunity to access a local workforce, providing employment and training for Indigenous workers.