Depth to Basement 3D Model in the South-Nicholson Basin, Northern Australia

Abstract:

To help the management and exploration at depth of increasing demand for mineral, energy and water resources, integration of new data acquired in frontier areas in a common 3D sub-surface geological model is critical. The Exploring for the Future Program has facilitated the acquisition of major datasets in northern Australia, where rocks are mostly undercover and the basin evolution and resource potential is not well understood.

Here we present a case study in the South-Nicholson Basin, located in a vast, poorly exposed area between two highly prospective Paleo- to Mesoproterozoic provinces, the Mt Isa Province and the McArthur Basin. Both regions host major base metal mineral deposits, and contain units prospective for hydrocarbons. In this study we integrate new large-scale data, which include ~1 900 km of deep seismic reflection data and 60 000 line kilometers of AusAEM1 airborne electromagnetic survey, with legacy information and new tools, to help build a semi-continental geological framework, as input to national coverage databases and inform decision-making for mining and petroleum exploration.

This study provides a 3D chronostratigraphic cover model down to the Paleoproterozoic basement. We mapped the depth to the base of geological eras, as well as deeper pre-Neoproterozoic Superbasin sequence boundaries to refine the cover model. The depth estimates are based on the interpretation, compilation and integration of boreholes, solid geology, reflection seismic, airborne electromagnetic data and depth to magnetic source estimates. These depth estimates are consistently stored in national databases. These integrated datasets inform on the basin evolution in relation to the basement architecture and provided key outcomes: 1) expanded the size of the basin, significantly increasing the extent of regional petroleum systems in the region, 2) revealed a large concealed sedimentary sub-basin interpreted to include rocks that host the world class Mount Isa Cu-Pb-Zn deposits, 3) linked the stratigraphy with correlation of prospective stratigraphic units across the region, 4) identified major crustal boundaries and structures showing evidence for crustal-scale fluid flow and localised groundwater springs.