Exploring for the future presentation- The structure and stratigraphy of the South Nicholson region – implications for resource prospectivity; Insight from the EFTF geochronology and deep reflection seismic programs

The structural evolution of the South Nicholson region is not well understood, hindering full appraisal of the resource potential across the region. Here, we outline new insights from a recent deep-reflection seismic survey, collected as part of the Australian Government’s Exploring for the Future initiative. The new seismic profiles, and new field observations and geochronology, indicate that the South Nicholson region was characterised by episodic development of a series of ENE-trending half grabens. These graben structures experienced two major episodes of extension, at ca. 1725 Ma and ca. 1640 Ma, broadly correlating with extensional events identified from the Lawn Hill Platform and the Mount Isa Province to the east. Southward stratal thickening of both Calvert and Isa Superbasin sequences (Paleoproterozoic Carrara Range and McNamara groups, respectively) into north-dipping bounding faults is consistent with syndepositional extension during half graben formation. Subsequent basin inversion, and reactivation of the half graben bounding faults as south-verging thrusts, appears to have been episodic. The observed geometry and offset are interpreted as the cumulative effect of multiple tectonic events, including the Isan Orogeny, with thrust movement on faults occurring until at least the Paleozoic Alice Springs Orogeny. <b>Citation:</b> Carson, C.J.. Henson, P.A., Doublier, M.P., Williams, B., Simmons, J., Hutton, L. and Close, D., 2020. Structural evolution of the South Nicholson region: insight from the 2017 L210 reflection seismic survey. 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.

The South Nicholson Basin sits between the Mount Isa Province to the east and 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, the South Nicholson region is mostly undercover, little studied and consequently relatively poorly understood. A comprehensive U–Pb SHRIMP zircon and xenotime geochronology program was undertaken to better understand the stratigraphy of the South Nicholson region and its relationship to the more overtly prospective adjacent Mount Isa Province and McArthur Basin. The age data indicate 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 currently interpreted as the timing of post-diagenetic regional fluid flow. The 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. Some rocks, mapped previously as Mesoproterozoic South Nicholson Group and comprised of proximal, immature lithofacies, have detrital spectra consistent with that of the late Paleoproterozoic McNamara Group of the western Mount Isa Province which necessitates a revision of existing regional stratigraphic relationships. The stratigraphic revisions and correlations proposed here significantly expands the extent of highly prospective late Paleoproterozoic stratigraphy across the South Nicholson region and possibly, further west beneath the Georgina Basin. The data and conclusions presented here allow for improved regional stratigraphic correlations between Proterozoic basins, improved commodity prospectivity and targeted exploration strategies across central northern Australia. Presented at the 2020 Annual Geoscience Exploration Seminar (AGES)

This web service provides access to satellite imagery products for the identification of potential groundwater dependent ecosystems (GDEs) in the South Nicholson - Georgina region.

The Buddycurrawa Volcanics (BV, Benmara Group) are a sequence of trachyte lavas and interleaved shallow-marine siliciclastic rocks, exposed in the Benmara region, northwestern Mount Drummond 1:250 000 map sheet, Northern Territory. Previous information, including resource potential, on the BV was limited, and stratigraphic correlation with other regional volcanic units was speculative. Our new geochronology data establish the extrusion age of the BV as late Paleoproterozoic, constrained by a maximum age of ca. 1662 Ma (SHRIMP U-Pb zircon) and a minimum age of ca 1631 Ma (in situ laser Rb-Sr on glauconite within vesicles). The BV are, therefore, temporally equivalent to numerous ash fall tuffs reported throughout regional highly prospective late Paleoproterozoic successions. The BV also host vertical siliceous pipes, representing ‘white smokers’—peripheral low-temperature equivalents of black smokers—suggestive of a regional shallow-marine hydrothermal circulatory system and potential for associated base metal mineral systems. The BV are pervasively potassically altered. Laser Rb-Sr dating on matrix secondary microcline returns ages ca. 1612–1323 Ma, reflecting timing of fluid flow responsible for at least some of the potassic alteration. These are broadly consistent with similar estimates of episodes of regional fluid flow and base metal mineralisation and/or remobilisation in the Mount Isa Province. <b>Citation:</b> Carson, C.J., Kositcin, N., Farkas, J., Champion, D.C., Whelan, J., Redaa, A., Gilbert. S., Henson, P.A., Maas, R., Williams, B. and Doublier, M.P., 2020. The late Paleoproterozoic Buddycurrawa Volcanics, South Nicholson region. 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.

<p>This Record presents the results of 26 new zircon U-Pb isotopic analyses, conducted on Geoscience Australia’s Sensitive High Resolution Ion Micro Probe (SHRIMP2e), under the Commonwealth Government’s Exploring for the Future (EFTF) program, a $100.5 million, four year, initiative to better understand the mineral, energy and groundwater potential across northern Australia. <p>These new data, determined on sedimentary and volcanic rocks, were collected from across the South Nicholson region, located in the north-eastern Northern Territory. The South Nicholson region is geographically located between two highly prospective geological provinces, the greater McArthur Basin in the Northern Territory and the Mount Isa Province in Queensland, regions noted for their hydrocarbon potential and world-class base-metal endowment. <p>The South Nicholson region has been sparsely investigated by modern geological investigations, and, as such, these new SHRIMP U-Pb data, in concert with other complementary EFTF geochronological, geochemical and geophysical datasets from the region (e.g. Anderson et al., 2019; Carr et al., 2019; Ley-Cooper and Brodie, 2019; Jarrett et al., 2019) will place important geological constraints on the geological evolution, the timing of deposition, sedimentary processes, basin architecture and evolution of the South Nicholson region and, arguably most significantly, provide new improved lithostratigraphic and chronostratigraphic correlations with the adjacent highly prospective Proterozoic Basins. <p>Such geological correlations are critical for reducing exploration risk, improve resource prospectivity and enabling targeted ‘greenfield’ resource exploration activities, a tangible key objective under the Exploring for the Future initiative.

<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>

The Exploring for the Future program is an initiative by the Australian Government dedicated to boosting investment in resource exploration in Australia. As part of the Exploring for the Future program, this study aims to improve our understanding of the petroleum resource potential of northern Australia. The physical properties of organic matter in sedimentary rocks changes composition in an irreversible and often sequential manner after burial, diagenesis, catagenesis and metagenesis with increasing thermal maturity. Characterising these changes and identifying the thermal maturity of sedimentary rocks is essential for calculating thermal models needed in a petroleum systems analysis. This study presents organic petrology on 15 Proterozoic aged shales from the Velkerri and Barney Creek formations in the McArthur Basin and the Mullera Formation, Riversleigh Siltstone, Lawn Hill and Termite Range formations in the South Nicholson region. Qualitative maceral analysis of the 15 samples are described in addition to bitumen reflectance measurements. These samples were analysed at the Montanuniversität Leoben, Austria in June 2020. The results of this study can be used to improve our understanding of the thermal maturity and hydrocarbon prospectivity of Proterozoic aged sedimentary basins in northern Australia.

<p>In this study, a total of 53 surface outcrop samples were analysed for both inorganic and organic whole-rock geochemistry as part of Exploring for the Future (EFTF) program, a government initiative undertaken by the Australian Government to boost investment in resource exploration and development in northern Australia. The samples were collected during two EFTF funded field seasons conducted in May 2017 (18 samples, GA job number 33004) and May 2018 (35 samples, GA job number 33228). <p>This data release contains the results of elemental analyses including X-Ray Fluorescence (XRF), Inductively Coupled Plasma- Mass Spectrometry (ICP-MS), iron titration (FeO), Loss-On-Ignition (LOI) and Rock-Eval pyrolysis on 53 outcrop samples collected across two seasons of fieldwork in the South Nicholson region. This data release are provided to facilitate establishment of important baseline assessments and whole rock characterisation of regional sedimentary rocks for insight into the resource prospectivity of northern Australian basins. These data was generated at the Geochemistry Laboratories at Geoscience Australia as part of the Exploring for the Future program

Exploring for the Future (EFTF) is an Australian Government program led by Geoscience Australia, in partnership with state and Northern Territory governments. The first phase of the EFTF program (2016-2020) aimed to drive industry investment in resource exploration in frontier regions of northern Australia by providing new precompetitive data and information about their energy, mineral and groundwater resource potential (Carr et al 2018). The South Nicholson Basin and immediate surrounding region is situated between Paleo-Mesoproterozoic Mount Isa Province and McArthur Basin. Both the Mount Isa Province and McArthur Basin are well studied. By contrast, the adjacent South Nicholson region is less studied, and contains rocks that are mostly undercover, for which the basin evolution and resource potential is not well understood. To address this gap, the L210 South Nicholson Deep Crustal Seismic Survey was collected in 2017 in the region between the southern McArthur Basin to the Mount Isa western succession, crossing the South Nicholson Basin and Murphy Province, providing a fundamental data link across these regions (L210 South Nicholson Deep Crustal Seismic Reflection Survey). The primary aim of the survey was to investigate areas with a low measured gravity response in the region to determine whether they represent thick basin sequences, as is the case for the nearby prospective Beetaloo Sub-basin. The interpretation of this survey led to the discovery of a new basin, the Carrara Sub-basin, coinciding with a gravity low in the south-eastern South Nicholson Basin Region. This data set contains an exported set of XYZ points from interpreted horizons (Carr et al 2019) on the South Nicholson Seismic Survey (L210) in both two way time (TWT ms on PreSTM_17ga lines) and depth (m) re-interpreted on depth indexed PreSDM_17GA lines. The coordinate reference system for this dataset is WGS 1984 Australian Centre for Remote Sensing Lambert. Seismic reference datum is 350 m. The seismic reference datum are described in the EBCDIC headers of the SEGY files for each of the survey lines. Carr, L.K., Southby, C., Henson, P., Costello, R., Anderson, J.R., Jarrett, A.J M., Carson, C.J., Gorton, J., Hutton, L.J., Troup, A., Williams, B., Khider, K., Bailey, A. & Fomin, T. 2019. Exploring for the Future: South Nicholson Basin geological summary and seismic interpretation. Record 2019/21, Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2019.021 Carr, L.K., Southby, C., Henson, P., Anderson, J.R., Costelloe, R., Jarrett, A.J.M., Carson, C.J., MacFarlane, S.K., Gorton, J., Hutton, L., Troup, A, Williams, B., Khider, K., Bailey, A.H.E., Fomin, T. 2020. South Nicholson Basin seismic interpretation. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/132029 L210 South Nicholson Deep Crustal Seismic Reflection Survey, NT and QLD, 2017. Geoscience Australia, Canberra. https://pid.geoscience.gov.au/dataset/ga/116881.