The Northern Australia Hydrogeochemistry Survey

Map showing the distribution of copper in groundwater and soils over the Tennant Creek and the McArthur Basin region survey area.

The Northern Australia Hydrogeochemical Survey (NAHS) is the culmination of a multi-year, regional groundwater sampling program between Tennant Creek and Mt Isa in the Northern Territory (Figure 1). It uses groundwater chemistry at a regional scale (sampling density ~1 bore/15-25 km2) from existing pastoral water bores to provide insights into the region’s mineral, groundwater and energy resources.

From a mineral resource perspective, this work was conducted to identify the most suitable chemical indicators that apply to various mineral systems. Initially targeting areas of shallow cover near known mineral deposits as well as in barren areas, the project then extended into regions of deeper cover to develop and test these diagnostic tools. The NAHS also sampled above the Beetaloo Basin and South Nicholson Basin which are prospective for energy resources. In these regions the NAHS can be used as an environmental baseline of water composition prior to the onset of new industries.

Scientist out in the field taking hydrogeochemistry measurements in the Northern Territory.

In addition to standard measurements including bulk parameters (e.g., temperature, pH, electrical conductivity), major anions, major cations and trace elements, selected groundwater samples were analysed for a comprehensive suite of isotopes (e.g. Oxygen, Hydrogen, Carbon, Sulfur, Chlorine, Strontium, Lead, Helium), organic compounds, hydrocarbons and dissolved gases. Extremely high-quality data is required to make meaning interpretations from small variations in metal composition in the water, thus specific attention has been given to robust sampling, reproducible analyses and avoiding contamination.

The NAHS is a world-first for the detail collected at each bore and the breadth of the region sampled. Ongoing work will utilise these data to investigate chemical indicators which can be applied as an exploration tool in Australia, with the capability of identifying and targeting parts of mineral systems under cover. The hydrogeochemical data provides baseline data for improved understanding of regional aquifers, hydrogeologic processes and broad scale groundwater quality for diverse stakeholders.

Progress

During tranche 1, the NAHS team collected 118 groundwater samples from 106 bores across the Tennant Creek and McArthur River regions using sampling techniques suitable for up to 117 analytes per site. This hydrochemistry data, preliminary interpretation and atlas maps are now publicly available. Tranche 2 has collected an additional 106 samples from 97 bores in the Beetaloo, East Tennant Creek and South Nicholson regions. Tranche 2 samples are in the process of being analysed and quality controlled prior to public release in June 2020.

Outputs

  • The first tranche of quality controlled hydrogeochemical data in the Tennant Creek, Lake Woods and McArthur River regions has been released publicly and are available to download here.
  • An updated comprehensive dataset and map products will be released publicly in June 2020. This will include hydrogeochemistry collected as part of tranche 2 in the Beetaloo, East Tennant Creek and South Nicholson regions as well as improvements to the already released data of tranche 1.
  • An extended abstract outlining the application of hydrogeochemistry to identify the subsurface aquifer geology will be coming out in June 2020.

Collaborations

We have collaborated with the Northern Territory Geological Survey (NTGS),NT Department of Environment and Natural Resources (Water resources) and the Geological Survey of Queensland (GSQ); further collaboration with external industry, academia and other government and research organisations (e.g., CSIRO) greatly enhances the type of data collected and the quality and breadth of analysis and data interpretation.

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