The Mesoproterozoic South Nicholson Basin sits between, and overlies, the Paleoproterozoic Mount Isa Province to the east and the southern McArthur Basin to the northwest. The McArthur Basin and Mount Isa Province are well studied and highly prospective for both mineral and energy resources. In contrast, rocks in the South Nicholson region (incorporating the Mount Isa Province, the Lawn Hill Platform and the South Nicholson Basin, and geographically straddling the Northern Territory and Queensland border) are mostly undercover, little studied and consequently relatively poorly understood. A comprehensive U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon and xenotime geochronology program was undertaken to better understand the stratigraphy of the South Nicholson region and its relationship to the adjacent, more overtly prospective Mount Isa Province and McArthur Basin. The age data indicate that South Nicholson Basin deposition commenced ca. 1483 Ma, with cessation at least by ca. 1266 Ma. The latter age, based on U-Pb xenotime, is interpreted as the timing of postdiagenetic regional fluid flow. The geochronology presented here provides the first direct age data confirming that the South Nicholson Group is broadly contemporaneous with the Roper Group of the McArthur Basin. Some rocks, mapped previously as Mesoproterozoic South Nicholson Group and comprising proximal, immature lithofacies, have detrital spectra consistent with that of the late Paleoproterozoic McNamara Group of the western Mount Isa Province; this will necessitate a revision of existing regional stratigraphic relationships. The stratigraphic revisions and correlations proposed here significantly expand the extent of highly prospective late Paleoproterozoic stratigraphy across the South Nicholson region, which, possibly, extends even further west beneath the Georgina and Carpentaria basins. Our data and conclusions allow improved regional stratigraphic correlations between Proterozoic basins, improved commodity prospectivity and targeted exploration strategies across northern Australia. <b>Citation:</b> Carson, C.J., Kositcin, N., Anderson, J.R., Cross, A. and Henson, P.A., 2020. New U–Pb geochronology for the South Nicholson region and implications for stratigraphic correlations.. 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.

NDI Carrara 1 is a deep stratigraphic drill hole (~1751m) 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 depocentre newly discovered in the South Nicholson region based on interpretation from seismic surveys (L210 in 2017 and L212 in 2019) recently acquired as part of the Exploring for the Future program. The drill hole intersected approximately 1100 m of Proterozoic sedimentary rocks uncomformably overlain by 630 m of Cambrian Georgina Basin carbonates. This report presents inorganic geochemical analyses undertaken by Geoscience Australia on selected rock samples, collected at roughly 4 m intervals.

Exploring for the Future (EFTF) is a four-year (2016-20) geoscience data and information acquisition program that aims to better understand on a regional scale the potential mineral, energy and groundwater resources concealed under cover in northern Australia and parts of South Australia. Hydrogeochemical surveys utilise groundwater as a passive sampling medium to reveal the chemistry of the underlying geology including hidden mineralisation. These surveys also potentially provide input into regional baseline groundwater datasets that can inform environmental monitoring and decision making. Geoscience Australia, as part of the Australian Government’s EFTF program, undertook an extensive groundwater sampling survey in collaboration with the Northern Territory Geological Survey and the Geological Survey of Queensland. During the 2017, 2018 and 2019 dry season, 224 groundwater samples (including field duplicate samples) were collected from 203 pastoral and water supply bores in the Tennant Creek-Mt Isa EFTF focus area of the Northern Territory and Queensland. An additional 38 groundwater samples collected during the 2013 dry season in the Lake Woods region from 35 bores are included in this release as they originate from within the focus area. The area was targeted to evaluate its mineral potential with respect to iron oxide copper-gold, sediment-hosted lead-zinc-silver and Cu-Co, and/or lithium-boron-potash mineral systems, among others. The 2017-2019 surveys were conducted across 21 weeks of fieldwork and sampled groundwater for a comprehensive suite of hydrogeochemical parameters, including isotopes, analysed over subsequent months. The present data release includes information and atlas maps of: 1) sampling sites; 2) physicochemical parameters (EC, pH, Eh, DO and T) of groundwater measured in the field; 3) field measurements of total alkalinity (HCO3-), dissolved sulfide (S2-), and ferrous iron (Fe2+); 4) major cation and anion results; 5) trace element concentrations; 6) isotopic results of water (δ18O and δ2H), DIC (δ13C), dissolved sulfate (δ34S and δ18O), dissolved strontium (87Sr/86Sr), and dissolved lead (204Pb, 206Pb, 207Pb, and 208Pb) isotopes; 7) dissolved hydrocarbon VFAs, BTEX, and methane concentrations, as well as methane isotopes (δ13C and δ2H); and 8) atlas of hydrogeochemical maps representing the spatial distribution of these parameters. Pending analyses include: CFCs and SF6; tritium; Cu isotopes; and noble gas concentrations (Ar, Kr, Xe, Ne, and 4He) and 3He/4He ratio. This data release (current as of July 2021) is the second in a series of staged releases and interpretations from the Northern Australia Hydrogeochemical Survey. It augments and revises the first data release, which it therefore supersedes. Relevant data, information and images are available through the GA website (https://pid.geoscience.gov.au/dataset/ga/133388) and GA’s EFTF portal (https://portal.ga.gov.au/).

Exploring for the Future (EFTF) is an Australian Government initiative that gathers new data and information about potential mineral, energy and groundwater resources. Commencing in 2016 with a focus on northern Australia, an EFTF extension to 2024 was recently announced, with expanded coverage across mainland Australia and Tasmania. The EFTF energy component aims to improve our understanding of the petroleum potential of frontier onshore Australian basins and has acquired significant pre-competitive datasets, including the recently drilled Barnicarndy 1 deep stratigraphic well in Western Australia’s Canning Basin (in partnership with the Geological Survey of Western Australia), and NDI Carrara 1 deep stratigraphic well in the South Nicholson region of the Northern Territory (in partnership with the MinEX CRC). These are the first stratigraphic wells drilled in a petroleum basin by Geoscience Australia since the formation in 2001 from its predecessor agencies. Both wells were sited along two-dimensional, deep crustal seismic surveys acquired by Geoscience Australia as part of EFTF, and provide stratigraphic control for the imaged geology. The sedimentary fill intersected by the Barnicarndy 1 and NDI Carrara 1 wells were cored and logged with a broad suite of wireline tools, providing substantial new data in two frontier basins. These data provide insights into regional stratigraphy and local lithology. Geochronology, petrographic, organic and inorganic geochemistry, petrophysical rock properties, petroleum systems elements, palaeontological, and fluid inclusion studies have been undertaken upon which inferences on regional prospectivity can made in these data-poor regions. Moving into the next phase of EFTF, these wells provide a template for new pre-competitive data acquisition by Geoscience Australia, expanding our knowledge of frontier regions making them attractive for new investment and exploration.

The South Nicholson region, which includes the Paleoproterozoic Isa Superbasin, the Mesoproterozoic South Nicholson Group and overlying younger sediments, is sparsely explored and has recently come into increased focus as a result of the Australian Government’s Exploring for the Future program. Previous exploration has identified potential shale gas plays within the River and Lawn supersequences of the Isa Superbasin in northwest Queensland’s northern Lawn Hill Platform region. Understanding mineralogy is important for characterising shale reservoirs, as mechanical properties such as shale brittleness are influenced by mineral composition. Mineralogy can, therefore, be utilised as a proxy for mechanical properties that are crucial to minimising risks associated with exploring for and developing shale reservoirs. This study utilises three different methods for calculating brittleness; XRD mineralogy, XRF major element geochemistry, and geomechanical properties. Results indicate highly variable mineralogy within the analysed samples, demonstrating heterogeneity in shale brittleness throughout the studied supersequences. Brittleness calculated from XRD analysis ranges from ductile to brittle with zones of brittle shales present in all supersequences. Increasing quartz and decreasing clay content is the dominant control on shale brittleness in the studied samples. Correlation between XRF major element geochemistry and XRD mineralogy is demonstrated to be moderate to poor, with brittleness derived from XRF major element geochemistry observed to be significantly higher than brittleness derived from XRD mineralogy. Conversely, brittleness derived from geomechanical properties agrees closely with XRD mineralogy derived brittleness. Hence, XRF major element geochemistry data are not recommended in the South Nicholson region to calculate brittleness. Analysis of brittleness indices from this study, in combination with total organic carbon content drawn from regional geochemical analysis in the South Nicholson region, identifies potential shale gas target intervals in the River, Term, and Lawn supersequences. Data presented on correlated well sections highlights intervals of exploration interest within these supersequences, being those depths where high organic content, brittle rocks are identified. The rocks that meet this criteria are primarily constrained to the already known potential shale gas plays of the River and Lawn supersequences. Recent data from Geoscience Australia implies that these potential shale gas plays are likely to extend from the northern Lawn Hill Platform, where they have been primarily identified to date, underneath the South Nicholson Basin and into the Carrara Sub-basin, significantly increasing their lateral extent. <b>Citation:</b> A. H. E. Bailey, A. J. M. Jarrett, L. Wang, B. L. Reno, E. Tenthorey, C. Carson & P. Henson (2022) Shale brittleness within the Paleoproterozoic Isa Superbasin succession in the South Nicholson region, Northern Australia, <i>Australian Journal of Earth Sciences, </i>DOI: 10.1080/08120099.2022.2095029

Zircon and xenotime U–Pb SHRIMP geochronology was conducted on samples from the South Nicholson Basin, and western Mount Isa Orogen. These samples were collected from outcrop and core from the Northern Territory and Queensland. The age data indicate the South Nicholson Basin was deposited after ca 1483 Ma but deposition most likely had ceased by ca 1266 Ma; the latter age likely represents post-diagenetic fluid flow in the area, based on U–Pb xenotime data. Geochronology presented here provides the first direct age data confirming the South Nicholson Group is broadly contemporaneous with the Roper Group of the McArthur Basin, which has identified facies with high hydrocarbon prospectivity. In addition, geochronology on the Paleoproterozoic McNamara Group provides new age constraints that have implications for the regional stratigraphy. The data obtained in this geochronological study allow for a comprehensive revision of the existing stratigraphic framework, new correlations and enhances commodity prospectivity in central northern Australia.

The South Nicholson region of northwest Queensland and the Northern Territory is the focus of a regional hydrocarbon prospectivity assessment being undertaken by the Exploring for the Future (EFTF) program, an Australian Government initiative dedicated to increasing investment in resource exploration in northern Australia. This data release provides data from new digital photography, X-ray Computerised Tomography (XCT) scanning, unconfined compressive strength (UCS) testing and laboratory ultrasonic testing for 14 samples from stratigraphic and exploration wells drilled into the South Nicholson Basin and Lawn Hill Platform in the South Nicholson region described in Jarrett et al (2020). These samples were analysed at CSIRO Geomechanics and Geophysics Laboratory in Perth during May and June 2020.

Proterozoic rocks of the South Nicholson region are juxtaposed between the Mount Isa Province and the McArthur Basin. Whereas the latter two provinces are well-studied and prospective for energy and mineral resources, the geological evolution and resource potential of the South Nicholson region is not well understood. Geoscience Australia, under the Exploring for the Future (EFTF) initiative, in collaboration with State and Territory Geological Surveys, conducted a range of regional geoscience investigations to better understand the resource potential across the South Nicholson region to encourage greenfield resource exploration. Here we discuss preliminary findings on an unreported massive manganese oxide (MnO) occurrence in the Carrara Range in the South Nicholson region, north-eastern Northern Territory. The occurrence is hosted by a north-dipping quartz sandstone unit of the ca. 1640 Ma) sandstones of the Plain Creek Formation (McNamara Group), in the hanging wall of the south-verging, east-west trending Wild Cow Fault zone. The Plain Creek Formation conformably overlies the Shady Bore Quartzite, and conformably underlies shales and carbonaceous siltstones of the Lawn Hill Formation. The Plain Creek Formation is stratigraphically equivalent to the Riversleigh Siltstone in the Lawn Hill Platform. The massive MnO body is comprised of pyrolusite (MnO2) and cryptomelane (KMn8O16), surrounded by a halo of partially MnO altered host sandstone, crosscut by numerous 1‒5mm wide ‘feeder’ veinlets. These zoned veinlets consist of quartz, pyrolusite and cryptomelane with wall quartz projecting into the veinlets with Mn minerals infilling the centre of the veins. The MnO body is ~20 m wide across strike. The lateral and depth extent of the occurrence is unknown, but satellite imagery indicates that MnO mineralisation is visible, along strike, for at least several hundred metres. These observations suggest that the Carrara Range MnO occurrence is likely an epigenetic replacement stratiform body. Geochemistry on the MnO body return 49.8 wt% MnO with appreciable (ca. 450 ppm) Zn; the host sandstone return 10.8 wt% MnO and ca. 25 ppm Zn. Reconnaissance fluid inclusion analysis on quartz-MnO veinlets reveals both brine+vapour aqueous inclusions and hydrocarbon+vapour inclusions. Co-existing aqueous and hydrocarbon were not observed. Homogenisation temperatures are 90‒180°C for aqueous inclusions and 60‒140°C for hydrocarbon inclusions. Fluid salinities are 10‒23 wt% (NaCl equivalent), which may suggest interaction with evaporites. Decrepitation of the fluid inclusions yielded CO2 with no accompanying hydrocarbon gases, suggesting an oxidising fluid. The 𝛿13C CO2 of -22 ‰ is consistent with an organic source, possibly from oil oxidation. The mineralising fluids were high salinity, low temperature (ca. 120°C) fluids, typical of fluids for Mississippi-Valley and/or Mount Isa style base-metal deposits. The host Plain Creek Formation is stratigraphically equivalent to units that host world-class regional Pb-Zn deposits such as Century, McArthur River (HYC) and Lady Loretta and others of north-western Queensland and north-eastern Northern Territory. This correlation, together with the knowledge that many Pb-Zn deposits across the region are associated with manganese enrichment, increases the potential of a base metal resource in the South Nicholson region. Discovery of the Carrara Range Mn occurrence may stimulate regional base metal exploration. Abstract presented at the 2021 Australian Earth Sciences Convention (AESC)

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.

<div>This study was commissioned by Geoscience Australia (GA) to produce a report on seal capacity of select samples from the deep stratigraphic hole NDI Carrara 1, located in the Proterozoic Carrara Sub-basin in the Northern Territory. Plugs were taken from depths of interest and analysed via mercury injection capillary pressure testing. Results were provided as two reports, Part A and Part B and demonstrate that the analysed samples are capable of sealing very large columns of both methane and carbon dioxide.</div>