Exploring for the Future, 2023 Northwest Northern Territory Seismic Survey (L214), Preliminary geological interpretation and drill core analytical program

Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources.  Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.

The Proterozoic Birrindudu Basin is an underexplored region that contains sparse geological data. Strata of similar age are highly prospective to the east, in the McArthur and South Nicholson basins and the Mount Isa region. To investigate this underexplored and data-poor region, the L214 Northwest Northern Territory Seismic Survey was acquired in August to September 2023 by GA and co-funded by the Northern Territory Government. Prior to this survey the region contained minimal seismic data. To complement the acquisition of the seismic survey, a sampling program of legacy stratigraphic and mineral exploration drill holes was also undertaken.

The new sampling program and seismic reflection data acquired over the Birrindudu Basin and its flanks, has identified many areas of exploration opportunity. This has almost tripled seismic coverage over the Birrindudu Basin, which has enabled new perspectives to be gained on its geology and relationship to surrounding regions. The new seismic has shown an increase in the extent of the Birrindudu Basin, revealing the presence of extensive concealed Birrindudu Basin sedimentary sequences and major, well preserved depocentres. In the central Birrindudu Basin and Tanami Region, shallow basement and deep-seated faults are encouraging for mineralisation, as these structures have the potential to focus mineralised fluids to the near surface. The clear presence of shallow Tanami Region rocks underlying the southern Birrindudu Basin sequences at the northern end of line 23GA-NT2 extends the mineral resource potential of the Tanami Region further north into the southern Birrindudu Basin. A new minimum age of 1822±7 Ma for the deposition of metasediments in drill hole LBD2 for rocks underlying the central Birrindudu Basin, extends the age-equivalent mineral-rich basement rocks of the Tanami Region north into the central Birrindudu Basin – extending the mineral resource potential into a new region.

The continuous stratigraphy imaged of the Birrindudu Basin by the new seismic is encouraging for energy prospectivity, as the system elements needed for an effective petroleum system, better defined by the new sampling program results, have been imaged to extend over a wider and deeper area. New organic petrological analysis and reflectance data indicate the sampled sections have reached thermal maturity suitable for hydrocarbon generation. Oil inclusion analyses provide evidence for oil generation and migration, and hence elements of a petroleum system are present in the central and northwestern Birrindudu Basin. With the expanded breadth of these rocks demonstrated on the seismic, this greatly increases the spatial extent of hydrocarbon prospectivity in Birrindudu Basin.