Magnetotellurics is one of few techniques those can provide multiple-scale datasets to understand the larger mineral system. We have used long-period data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) as first-order reconnaissance survey to resolve large-scale lithospheric architectures for mapping areas of mineral potential in northern Australia. The 3D resistivity model reveals a broad conductivity anomaly extending from the Tennant Region to the Murphy Province, representing a potential fertile source region for mineral systems. We then undertook a higher-resolution infill magnetotellurics survey to refine the geometry of major structures, and to investigate if the deep structure is connected to the near surface by crustal-scale fluid pathways. The resistivity models reveal two prominent conductors in the resistive host whose combined responses result in the lithospheric-scale conductivity anomaly mapped in the AusLAMP model. The resistivity contrasts coincide with major structures preliminarily interpreted from seismic reflection and potential field data. Most importantly, the conductive structures extend from the lower crust to the near surface at where the major faults are located. This observation strongly suggests that these major faults are deep-penetrating structures that potentially acted as pathways for transporting metalliferous fluids to the upper crust where they could form mineral deposits. This result indicates high mineral prospectivity for iron oxide copper–gold deposits in the vicinity of these major faults. We then used high-frequency data to estimate cover thickness to assist with drill targeting for the stratigraphic drilling program which, in turn, will test the models and improve our understanding of basement geology, cover sequences and mineral potential. This study demonstrates that integration of geophysical data from multiscale surveys is an effective approach to scale reduction during mineral exploration in covered terranes. This Abstract was submitted/presented to the 2021 Australasian Exploration Geoscience Conference 13 - 17 September https://2021.aegc.com.au/.

With the increasing need to extend mineral exploration undercover, new approaches are required to better constrain concealed geology, thereby reducing exploration risk and search space. Hydrogeochemistry is an under-utilised tool that can identify subsurface geology and buried mineral system components, while also providing valuable insights into environmental baselines, energy systems and groundwater resources. With this aim, 238 water bores spanning seven geological provinces in the Northern Territory and Queensland were sampled and analysed for major cations and anions, trace elements, stable and radiogenic isotopes, organic species, and dissolved gases. Here, we demonstrate the utility of this dataset for identifying carbonate-rich aquifers and mineral system components therein. First, we use trends in major element ratios (Ca+Mg)/Cl– and SiO2/HCO–3, then strontium isotope ratios (87Sr/86Sr), to define subpopulations that reflect both spatial and compositional differences. We then apply mafic-to-felsic trace element ratios (V/Cs and Cu/Rb) to reveal elevated base metal concentrations near Lake Woods caused by water–rock interaction with dolerite intrusions. Correlated Sr concentrations between groundwater and surface sediments suggest that the geochemical evolution of these mediums in carbonate-dominated terrains is coupled. Our work develops an approach to guide mineral exploration undercover via the characterisation and differentiation of groundwaters from different aquifers, resulting in improved identification of geochemical anomalies. <b>Citation:</b> Schroder, I., de Caritat, P. and Wallace, L., 2020. The Northern Australia Hydrogeochemical Survey: aquifer lithologies, local backgrounds and undercover processes. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

This report presents key results from the Western Davenport study conducted as part of Exploring for the Future (EFTF), an Australian Government-funded geoscience data and information acquisition program. The Western Davenport (WD) investigation used existing geological and hydrogeological data and new AEM data to develop a 3D hydrostratigraphic model of the central part of the study area. This was augmented by existing and newly acquired hydrogeological and hydrochemistry data to improve the understanding of groundwater in the area. The collection and interpretation of these datasets have enabled a correlation between hydrostratigraphic units in the Wiso and Georgina basins in the WD area. The hydrochemistry data shows that the central zone of the WD is characterised by good-quality groundwater (<1000 mg/L total dissolved solids), with the newly drilled bores identifying areas of low-salinity groundwater. These initial hydrochemistry results suggest groundwater in the WD could support irrigated agriculture. The hydrochemistry data has identified three zones of potentially higher recharge. The groundwater stable isotope dataset suggests that there is minimal evaporation of water prior to recharge and that groundwater recharge only occurs following heavy rainfall events. This preliminary information suggests recharge to groundwater is dominated by episodic recharge from floodouts and creeks rather than direct infiltration across the WD area from large rainfall events. However, more data are needed to better define the role of floodouts in recharge to the groundwater system and to determine the contribution of creek beds versus floodouts to recharge. Given the aridity of the area and the variable nature of recharge events, managed aquifer recharge could increase the security of groundwater resources in the area. The regolith mapping presented can assist in better understanding the surface and near-surface environments, and their influence on hydrogeological processes. This provides a tool with which to begin identifying potential areas for enhancing natural recharge processes to supplement existing groundwater resources. This mapping was possible because of the increasing availability of higher resolution digital elevation, airborne radiometric and Landsat satellite remotely sensed data. The improved understanding of geology and hydrogeology, coupled with managed aquifer recharge mapping undertaken as part of the EFTF program, provides new information to support groundwater management in the WD area.

This service delivers airborne electromagnetics (AEM) derived conductivity grids for depth intervals representing the top 22 layers from AEM modelling in the West Musgrave region (https://dx.doi.org/10.26186/147969). The grids were generated from the AEM conductivity models released as part of the Western Resource Corridor AusAEM survey (https://dx.doi.org/10.26186/147688), the Earaheedy and Desert Strip AusAEM survey (https://pid.geoscience.gov.au/dataset/ga/145265) and several industry surveys (https://dx.doi.org/10.26186/146278) from the West Musgraves region. The AEM conductivity models resolve important subsurface features for assessing the groundwater system including lithological boundaries, palaeovalleys and hydrostatigraphy.

The Layered Geology of Australia web map service is a seamless national coverage of Australia’s surface and subsurface geology. Geology concealed under younger cover units are mapped by effectively removing the overlying stratigraphy (Liu et al., 2015). This dataset is a layered product and comprises five chronostratigraphic time slices: Cenozoic, Mesozoic, Paleozoic, Neoproterozoic, and Pre-Neoproterozoic. As an example, the Mesozoic time slice (or layer) shows Mesozoic age geology that would be present if all Cenozoic units were removed. The Pre-Neoproterozoic time slice shows what would be visible if all Neoproterozoic, Paleozoic, Mesozoic, and Cenozoic units were removed. The Cenozoic time slice layer for the national dataset was extracted from Raymond et al., 2012. Surface Geology of Australia, 1:1 000 000 scale, 2012 edition. Geoscience Australia, Canberra.

To improve understanding of basins and basement structures, and of the energy, mineral and groundwater resource potential of northern Australia, deep crustal seismic surveys were conducted, totalling 2787 line-km, between June 2017 and November 2019 as a part of Exploring for the Future program. Reflection seismic profiles provide the highest fidelity imaging of crustal-scale subsurface architecture and therefore have become the industry standard for energy exploration, and their use in mineral and groundwater applications is growing. Here, we document the acquisition of composite deep reflection seismic profiles (20 sec, ~60 km depth). The focus is on imaging new terranes, and resolving frontier basin and crustal architecture. Seismic data were acquired stretching from the Beetaloo Sub-basin to the Mt Isa western succession in the Northern Territory and Queensland, as well as in the Kidson Sub-basin in Western Australia. Raw data for these surveys are available on request from clientservices@ga.gov.au, and processed data are publicly available from the Geoscience Australia website at https://www.ga.gov.au/about/projects/resources/seismic. <b>Citation:</b> Fomin, T., Holzschuh, J., Costelloe, R.D., and Henson, P., 2020. Deep northern Australian 2D seismic reflections surveys. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

This report presents the results of scanning electron microscopy (SEM) and mercury porosimetry analyses on 1 whole core sample from the GSWA Waukarlycarly 1 stratigraphic well drilled in the Canning Basin. The well was drilled as part of a co-funded collaboration between Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA) aimed at gathering new subsurface data on the potential mineral, energy and groundwater resources in the southern Canning Basin. The collaboration resulted in the acquisition of the Kidson Deep Crustal Seismic Reflection Survey in 2018; and the drilling of deep stratigraphic well GSWA Waukarlycarly 1, located along the Kidson Sub-basin seismic line within the Waukarlycarly Embayment in 2019 (Figure 1). GSWA Waukarlycarly 1 reached a total depth of 2680.53 m at the end of November 2019 and was continuously cored through the entire Canning Basin stratigraphy. Coring was complemented by the acquisition of a standard suite of wireline logs and a vertical seismic profile. The work presented in this report constitutes part of the post well data acquisition. The purpose of the SEM analysis was to determine mineralogy and textural relationships between grains, verify the presence of organic material at the micro-scale, document i) the presence of diagenetic alterations to the detrital mineral assemblage and ii) eventual distribution of visible pores. Additionally, mercury injection capillary pressure porosimetry (MICP) was used to assess interconnected porosityand pore size distribution.

This web service provides access to groundwater raster products for the Upper Burdekin region, including: inferred relative groundwater recharge potential derived from weightings assigned to qualitative estimates of relative permeability based on mapped soil type and surface geology; Normalised Difference Vegetation Index (NDVI) used to map vegetation with potential access to groundwater in the basalt provinces, and; base surfaces of basalt inferred from sparse available data.

The Mineral Potential Mapper (MPM) project represents a significant step forward in identifying new mineral provinces in Australia. The project demonstrated that the apparent under-representation of giant Ni Cu-PGE sulfide resources in Australia was a consequence of concealment of mineral deposits by sediments, basins and regolith (cover) which has hindered exploration success, rather than a lack of geological endowment. The project focused on the identification of prospective regions considered worthy of more detailed work (by exploration companies). The availability of new digital datasets at continental scale enabled the work which predicted a high potential for Ni-Cu-PGE sulfide deposits in a wide range of geological regions across Australia. The project delivered the following outputs: – a technical report providing the first continental-scale assessment of Ni-Cu-PGE mineral potential of Australia applying knowledge-driven geographic information system (GIS)-based prospectivity analysis methods – a series of Geodatabase digital maps (included in the report) – primary digital data and programming script used in the GIS analysis – a workshop delivered in Perth to industry on the 12 June 2016 – a world first National mineral potential map for Ni Cu-PGE sulfide deposits. The MPM materials have generated considerable industry interest. Chalice Mining Limited (Chalice) (formerly Chalice Gold Mines Limited) notes the MPM “… provided valuable input into Chalice’s regional targeting, particularly when applied to frontier areas” (and that) “… recent success at Julimar validates the work by Geoscience Australia (GA) and shows the impact that pre-competitive data can have when applied to greenfields exploration.” Chalice’s Julimar discovery is the world’s largest deposit of its type discovered in 20 years and one of four Tier one deposits discovered in the world in the last five years. It has spurred a significant uptake in tenements by explorers across a green field region and further significant finds are likely. The project has also generated considerable international government interest, sparking the Critical Minerals Mapping Initiative. The United States of America and Canada are both applying similar innovative mineral systems-based assessment methodologies to undertake precompetitive prospectivity mapping at a national scale. Given the impact of the MPM project will only be fully appreciated with the realisation of new mines, ACIL Allen has considered two hypothetical mine development scenarios: development of the Gonneville deposit based on Chalice’s (Australian Securities Exchange) ASX report of 8 July 2022, and a second case with an expansion of the Gonneville deposit (to 500Mt), coupled with a more spectacular discovery (double the size of the Gonneville deposit). Both success case scenarios were modelled using a conservative set of assumptions drawn from Chalice’s ASX reporting, prevailing market figures and industry norms. Based on those assumptions, ACIL Allen estimates that the development scenarios could generate an overall benefit to the Australian economy of between $3.48 billion and $4.57 billion and between $1.21 billion and $1.56 billion in net benefits to the Commonwealth in terms of taxation. GA’s investment in the project ($3.0 million) enabled the creation of these benefits. Indeed, every dollar invested in this project by the Commonwealth through GA could generate between $1,176 and $1,546 in additional benefits to the economy. The estimated benefit-cost ratio (BCR) for the Commonwealth Government is between 409 and 526 for the ‘success cases’. This is a substantial step up from the initial assessment conduct 12 months ago prior to the availability of resource figures for the Gonneville deposit (with a small and a large mine delivering an overall benefit of between $441 million and $869 million, with a BCR between 65 and 127).

Communities and ecosystems along the Darling River face critical water shortages and water quality issues including high salinity and algal blooms due to a reliance on declining surface water flows, which are impacted by extraction and drought, exacerbated by increases in temperature driven by climate change. The Darling River, characterised by highly variable flows, is the primary water source for the region and our understanding of the spatial extent and character of lower salinity groundwater within the surrounding Darling Alluvium, which could provide an alternative water source, is limited. Scientific understanding of the highly variable groundwater-surface water system dynamics of the Darling River is also an integral part of the evidence base required to manage the water resources of the wider Murray-Darling Basin, which has experienced critical water shortages for domestic and agricultural consumptive use and serious ecological decline due to reduced flows. Other relevant groundwater systems in the study area include aquifers of the underlying Eromanga and Surat Basins in the north, aquifers of the Murray Basin in the south, and fractured rock aquifers of the Darling Basin in the south-central area. Understanding of connectivity between these systems and the groundwater systems within the Darling Alluvium, and surface water of the Darling River, is also limited. Here we present the findings of a desktop analysis combining previous research with new analysis on water level, hydrochemistry, and Airborne Electromagnetic depth sections. This integration suggests that basement geometry and hydrostratigraphy within the Darling Alluvium are key structural controls on surface-groundwater connectivity, and the occurrence of a saline groundwater system within the lower part of the alluvium which impacts the quality of surface water and shallow alluvial groundwater resources. Further data acquisition and integrated analysis are planned to test these relationships as part of the Upper Darling Floodplain project. <b>Citation:</b> Buckerfield S., McPherson A., Tan K. P., Kilgour P. & Buchanan S., 2022. From Upper Darling Floodplain groundwater resource assessment. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, https://dx.doi.org/10.26186/146847