<div>This report brings together data and information relevant to understanding the regional geology, hydrogeology, and groundwater systems of the South Nicholson – Georgina (SNG) region in the Northern Territory and Queensland. This integrated, basin-scale hydrogeological assessment is part of Geoscience Australia’s National Groundwater Systems project in the Exploring for the Future program. While the northern Georgina Basin has been at the centre of recent investigations as part of studies into the underlying Beetaloo Sub-basin, no regional groundwater assessments have focused on central and southern parts of the Georgina Basin since the 1970s. Similarly, there has been no regional-scale hydrogeological investigation of the deeper South Nicholson Basin, although the paucity of groundwater data limited detailed assessment of the hydrogeology of this basin. This comprehensive desktop study has integrated numerous geoscience and hydrogeological datasets to develop a new whole-of-basin conceptualisation of groundwater flow systems and recharge and discharge processes within the regional unconfined aquifers of the Georgina Basin.</div><div><br></div><div>Key outputs arising from this study include: (1) the development of a hydrostratigraphic framework for the region, incorporating improved aquifer attribution for over 5,000 bores; and (2) publicly available basin-scale groundwater GIS data layers and maps, including a regional watertable map for the whole Georgina Basin. This regional assessment provides new insights into the hydrogeological characteristics and groundwater flow dynamics within the Georgina Basin, which can aid in the sustainable management of groundwater for current and future users reliant on this critical water resource.</div><div><br></div><div><br></div>

Small-angle neutron scattering (SANS) measurements were performed on 32 rock samples from the southern Georgina Basin, central Australia to assess nanopore anisotropy. Anisotropy can only be determined from oriented core material, hence the samples were cut perpendicular to bedding in cores selected from three wells that intersect the base of the hydrocarbon-bearing, organic-rich middle Cambrian Arthur Creek Formation; the latter is the source rock for both unconventional and conventional plays in the basin. The evolution of anisotropy of two-dimensional SANS intensity profiles with depth (for pore diameters ranging from 10 nm to 100 nm) was quantified and correlated with SANS intensity and total organic carbon (TOC) content. Our results confirm hydrocarbon generation at the base of the Arthur Creek Formation. The nanopore anisotropy in the basal Arthur Creek Formation at the well locations CKAD0001 (oil generation window) and MacIntyre 1 (late oil generation window) varies roughly according to normal compaction. When the Arthur Creek Formation is in the gas window, as sampled at Baldwin 1, there is a strong (negative) correlation between the average vertical-to-horizontal pore shape anisotropy and SANS intensity. The results indicate that unconventional gas production from organic-rich regions of over mature shale may be adversely affected by abnormal pore compaction.

<div><strong>Output type: </strong>Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short abstract: </strong>Australian sediment-hosted mineral systems play a crucial role in providing base metals and critical minerals essential for the global low-carbon economy. The Georgina Basin has the key components for forming and preserving a sediment-hosted Zn-Pb mineral system, but historically has been considered ‘cover’ to deeper, more prospective Proterozoic basement rocks. Thus, the basin has remained relatively under-explored, with many questions yet to be resolved on its sediment-hosted Zn-Pb mineral system and prospectivity for Zn-Pb. Utilising new whole-rock and isotope geochemistry of the Georgina Basin from recently drilled holes in the Northern Territory, we demonstrate the sensitivity of local redox boundaries to detect regional mineralisation. Two geochemically enriched zones have been identified and interpreted as redox interfaces which have trapped and concentrated metals from the surrounding basin, a ‘supergene zone’ and a ‘water intercept zone’. The ‘supergene zone’ is a paleo water table horizon, while the ‘water intercept zone’ is an active redox front at the uppermost part of the Cambrian Limestone Aquifer. The enrichment of these redox zones is consistent across multiple drill holes, reaching up to 395 ppm Pb and 1550 ppm Zn. Additionally, the Pb isotopes of high-Pb and sulfidic intervals have a highly radiogenic character (206Pb/204Pb ~22.0–23.0) that is diagnostic of Georgina Basin’s Mississippi Valley-type Zn-Pb mineralisation. Taken together, these results suggest there may be buried mineralisation in this part of the Georgina Basin, as well as highlight the potential of these redox interfaces as a regional reconnaissance target for exploration.</div><div><br></div><div><strong>Citation: </strong>Schroder I.F., Huston D. & de Caritat P., 2024. The geochemistry of redox interfaces for insights into Zn-Pb prospectivity in the Georgina Basin. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, https://doi.org/10.26186/149116 </div>

Following the publication of Geoscience Australia record 2014/09: Petroleum geology inventory of Australia's offshore frontier basins by Totterdell et. al, (2014), the onshore petroleum section embarked upon a similar project for onshore Australian basins. The purpose of this project is to provide a thorough basis for whole of basin information to advise the Australia Government and other stakeholders, such as the petroleum industry, regarding the exploration status and prospectivity of onshore Australian basins. Eight onshore Australian basins have been selected for this volume and these include: the McArthur, South Nicholson, Georgina, Amadeus, Warburton, Wiso, Galilee and Cooper basins. This record provides a comprehensive whole of basin inventory of the geology, petroleum systems, exploration status and data coverage for these eight onshore Australian basins. It draws on precompetitive work programs by Geoscience Australia as well as publicly available exploration results and geoscience literature. Furthermore, the record provides an assessment of issues and unanswered questions and recommends future work directions to meet these unknowns.

The Exploring for the Future Program facilitated the acquisition of major geoscience datasets in northern Australia, where rocks are mostly under cover and the basin evolution, mineral, energy and groundwater resource potential are, in places, poorly constrained. In an effort to support sustainable, regional economic development and build stronger communities in these frontier areas, integration of new and legacy data within a consistent platform could enhance the recognition of cross-disciplinary synergies in sub-surface resource investigations. Here we present a case study in the South-Nicholson Basin, located in a poorly exposed area between the prospective Mt Isa Province and the McArthur Basin. Both regions host major base metal deposits, contain units prospective for energy resources, and hold significant groundwater resources in the overlying Georgina Basin. In this study, we interpret a subset of new regional-scale data, which include ~1 900 km of deep seismic reflection data and 60 000 line kilometres of AusAEM1 airborne electromagnetic survey, supplemented with legacy information. This interpretation refines a semi-continental geological framework, as input to national coverage databases and informs decision-making for exploration and groundwater resource management. This study provides a 3D chronostratigraphic cover model down to the Paleoproterozoic basement. We mapped the depth to the base of intervals corresponding to geological eras, as well as deeper pre-Neoproterozoic superbasin boundaries to refine the cover model. The depth estimates, based on the compilation, interpretation and integration of geological and geophysical datasets, inform the basement architecture controls on evolution of the basin, with several key outcomes: 1) expanded mapped size of the South Nicholson Basin, potentially, increasing prospectivity for hydrocarbons and basin-hosted mineralisation, 2) improved stratigraphic unit correlations across the region, 3) identification of major crustal structures, some of which are associated with mineralisation and springs, and 4) improved basin architecture definition, supporting future investigation of groundwater resources.

NDI Carrara 1 is a deep stratigraphic drill hole completed in 2020 as part of the MinEx CRC National Drilling Initiative (NDI) in collaboration with Geoscience Australia and the Northern Territory Geological Survey. It is the first test of the Carrara Sub-basin, a newly discovered Proterozoic depocentre in the South Nicholson region, based on interpretation from new seismic surveys (L210 in 2017 and L212 in 2019) acquired as part of the Exploring for the Future program. The drill hole intersected approximately 1120 m of Proterozoic sedimentary rocks unconformably overlain by 630 m of Cambrian Georgina Basin carbonates. Continuous cores recovered from 283 m to a total depth of 1751 m. Geoscience Australia conducted an extensive post-drilling analytical program that generated over 30 datasets which the interested reader can find under the EFTF webpage (under the "Data and publications" drop down menu) at https://www.eftf.ga.gov.au/south-nicholson-national-drilling-initiative This record links to the Exploring for the Future 'borehole completion report' for NDI Carrara 1 and access to all on-site downhole geophysical datasets.

This record presents nine new Sensitive High Resolution Ion Micro Probe (SHRIMP) U–Pb zircon results obtained under the auspices of the Exploring for the Future (EFTF) Programme, a four year, federally funded initiative to better understand the mineral, energy and groundwater potential of northern Australia. The results presented here are derived from eight sedimentary samples and one probable tuffaceous sample together belonging to the Mount Isa Province, South Nicholson Basin and Georgina Basin.

Stratigraphic drill hole NDI Carrara 1 was drilled as a collaboration between Geoscience Australia (GA), the Northern Territory Geological Survey (NTGS) and the Mineral Exploration Cooperative Research Centre (MinEx CRC). It reached a total depth of 1751 m in late 2020 and is the first drill hole to intersect the undifferentiated Proterozoic rocks of the Carrara Sub-Basin. It intersected approximately 630 m of Cambrian Georgina Basin sedimentary rocks overlying the ~1100 m of Proterozoic carbonates, black shales and other siliciclastics of the Carrara Sub-Basin succession. The formational assignments of the Georgina Basin succession are preliminary and were assigned in the field. The units intersected comprise the Border Waterhole Formation (~531m to ~630m), which is overlain by the Currant Bush Limestone (~249m to ~531m), which in turn is overlain by the Camooweal Dolostone (0m to ~249m). Of these, only the lower 80% of the Currant Bush Limestone and the entire Border Waterhole Formation were cored. This report presents biostratigraphic results from macrofossil examination of NDI Carrara 1 core samples within the Georgina Basin section.

<div>This report contains new whole-rock and isotope (Pb and Sr) geochemical data, associated sample metadata, an assessment of the data’s quality assurance, for 76 samples collected from the Georgina Basin of the East Tennant National Drilling Initiative (NDI) in 2021. The data can be downloaded via the Geoscience Australia EFTF portal (https://portal.ga.gov.au/persona/eftf) or in the files attached with this record (http://pid.geoscience.gov.au/dataset/ga/148954).</div><div><br></div><div>This new geochemistry data release builds on the success of the East Tennant NDI, addressing the data-gap in earlier geochemical sampling of these holes, by providing whole-rock geochemistry (and Pb+Sr isotopes) for the Georgina Basin cover sequence. Improved geochemical characterisation of Georgina Basin geology is valuable from both a hydrogeological and mineral systems perspective. The Georgina Basin extends across much of the Northern Territory and into western Queensland, comprised of Cryogenian to Devonian sediment packages.</div><div><br></div><div>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. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div>

<div>This study investigates the feasibility of mapping potential groundwater dependent vegetation (GDV) at a regional scale using remote sensing data. Specifically, the Digital Earth Australia (DEA) Tasseled Cap Percentiles products, integrated with the coefficient of greenness and/or wetness, are applied in three case study regions in Australia to identify and characterise potential terrestrial and aquatic groundwater dependent ecosystems (GDE). The identified high potential GDE are consistent with existing GDE mapping, providing confidence in the methodology developed. The approach provides a consistent and rapid first-pass approach for identifying and assessing GDEs, especially in remote areas of Australia lacking detailed GDE and vegetation information.</div>