This report was compiled and written to summarise the four-year Palaeovalley Groundwater Project which was led by Geoscience Australia from 2008 to 2012. This project was funded by the National Water Commission's Raising National Water Standards Program, and was supported through collaboration with jurisdictional governments in Western Australia, South Australia and the Northern Territory. The summary report was published under the National Water Commission's 'Waterlines' series. This document is supported by related publications such as the palaeovalley groundwater literature review, the WASANT Palaeovalley Map and associated datasets, and four stand-alone GA Records that outline the detailed work undertaken at several palaeovalley demonstration sites in WA, SA and the NT. Palaeovalley aquifers are relied upon in outback Australia by many groundwater users and help underpin the economic, social and environmental fabric of this vast region. ‘Water for Australia’s arid zone – Identifying and assessing Australia’s palaeovalley groundwater resources’ (the Palaeovalley Groundwater Project) investigated palaeovalleys across arid and semi-arid parts of Western Australia (WA), South Australia (SA) and the Northern Territory (NT). The project aimed to (a) generate new information about palaeovalley aquifers, (b) improve our understanding of palaeovalley groundwater resources, and (c) evaluate methods available to identify and assess these systems.

<div>A groundwater chemistry, regolith chemistry and metadata record for legacy geochemical studies over the southern Curnamona Province done by GA and partners as part of CRC LEME from 1999 to 2005, that was never fully released. This includes comprehensive groundwater chemistry from more than 250 bores in the Broken Hill region, containing physicochemical parameters, major and trace elements, and a suite of isotopes (34S, Pb, Sr, 18O, D). Recent work on this dataset (in 2021) has added hydrostratigraphic information for these groundwater samples. Also included is a regolith geochemistry dataset collected adjacent to some of the groundwater bores which tests the geochemical response of a range of different size fractions, depths and digests.</div>

<div>The push of mineral exploration under cover requires developing new geochemical exploration approaches. Detailed hydrogeochemistry addresses these needs and is valuable as a non-invasive mineral exploration technique that can identify lithological changes and dispersion signatures associated with mineralisation. Here we integrate whole-rock geochemistry and hydrogeochemistry to evaluate suitable geochemical tracers in groundwater for detecting phosphate and/or Pb-Zn style mineralisation in the Georgina Basin. The known Georgina Basin’s phosphate deposits are within the basin’s aquifers, providing groundwater near deposits greater exposure and opportunity for water-rock interactions with mineralised geology, resulting in trace element and isotope signatures of mineralisation at detectable levels. These tracers can then be applied elsewhere in the basin as a screening tool for detecting mineralisation. To achieve this, we collected rock geochemistry from the MinEx CRC East Tennant National Drilling Initiative Campaign (ME-ET) drillcore, and integrated it with nearby hydrogeochemistry (from the Northern Australia Hydrogeochemical Survey (NAHS)). </div><div><br></div><div>The NAHS was collected by Geoscience Australia as part of EFTF, which included 170 samples from Georgina Basin aquifers. This hydrogeochemistry dataset is high quality, due to robust sampling, QA/QC procedures and a comprehensive analysis suite, making it a useful tool for mineral exploration in the Georgina Basin. The ME-ET drilled 10 stratigraphic holes east of Tennant Creek, Northern Territory, in support of Geoscience Australia’s Exploring for the Future program (EFTF). Seventy six Georgina Basin rock samples were collected for whole rock geochemistry and a subset for Pb and Sr isotopes. Samples were selected to target: 1) background unmineralised lithostratigraphy, 2) intervals with groundwater intersections, and 3) transects through zones with anomalous concentrations of P, Pb, Zn and Cu, as identified by portable XRF analysis. </div><div><br></div><div>Initial exploratory data analysis of the hydrogeochemistry is conducted at various scales using principle component analysis and clustering approaches to identify the key attributes (major and trace elements, isotopes, hydrogeology etc.) that are associated with higher P content in the groundwater. These relationships are tested by comparing groundwater samples proximal (in depth and spatially) to high P compositions in the host rock, providing insight into the water-rock interactions taking place. Additionally, vertical whole rock geochemistry transects within the drill-holes are investigated to evaluate the trace element and/or isotopic features that are diagnostic of the enriched phosphate zones. We take the robust geochemical relationships identified from both approaches and apply them as tracers across the NAHS to flag areas of potential undiscovered mineralisation. As we will demonstrate, the NAHS can detect subtle or diluted mineralisation signatures, and underpins a revised understanding of phosphate mineral prospectivity in the Georgina Basin.</div> Abstract submitted and presented at 2023 Australian Earth Science Convention (AESC), Perth WA (https://2023.aegc.com.au/)

<div>The Curnamona Province and overlying basins (herein referred to as the Broken Hill region) contain many discrete groundwater systems. These include sedimentary aquifers of the Lake Eyre Basin, Eromanga Basin, Darling Basin and Arrowie Basin, as well as fractured rock aquifers of the Adelaide Superbasin and Curnamona Province. However, there is little known about the hydrogeology or hydrogeochemistry of these aquifers in the Broken Hill region. Given the semi-arid climate in this region, understanding these groundwater systems can better support sustainable use of the groundwater for agriculture, mining and potable water supplies.</div><div>&nbsp;</div><div>Aquifer attribution provides a fundamental starting point for any hydrogeological study. We will present recently released hydrogeochemical data for the Broken Hill region, and our subsequent process for assessing and attributing hydrostratigraphy to the samples. </div><div>The Broken Hill Groundwater Geochemistry dataset (BHGG) was recently released in its entirety (Caritat et al. 2022 http://dx.doi.org/10.11636/Record.2022.020). It contains a compilation of archival CRC LEME hydrochemistry data that was collected as part of several projects from 1999 to 2005. This high-quality dataset contains 275 groundwater samples and includes a comprehensive suite of majors, minors, trace elements and stable isotopes (δ34S, δ18O, δ2H, δ13C, 87Sr/86Sr, 208/207/206Pb/204Pb). </div><div> At the time of collection, some key bore metadata (e.g. bore depths, screen and aquifer information) were missing from the original data compilations and these metadata are crucial for any hydrogeological analysis and interpretation. Therefore, as part of the new BHGG data release we have developed a robust and consistent approach to add bore information and aquifer attribution, value-adding to the original BHGG chemical and isotopic data. This workflow utilises a combination of State databases, reports, field notes, drillhole compilations and geological maps, but still relied on local hydrological expertise to make decisions when encountering incomplete or conflicting information (which is reflected by a confidence rating on the attribution). </div><div> The resulting BHGG product has supported re-assessment of the key hydrogeological and geochemical knowledge gaps in each groundwater system. An overview of knowledge gaps and the new sampling program being undertaken will be included in the presentation. &nbsp;</div><div><br></div>This Abstract was submitted/presented to the 2022 Australasian Groundwater Conference 21-23 November (https://agc2022.com.au/)

A comprehensive compilation of rock, regolith and groundwater geochemistry across the Curnamona Province and overlying basins. This product is part of the Curnamona Geochemistry module of GA's Exploring for the Future program, which is seeking to understand geochemical baselines within the Curnamona Province to support mineral exploration under cover. Data is sourced from GA, CSIRO and state databases, and run through a quality control process to address common database issues (such as unit errors). The data has been separated by sample type and migrated into a standard data structure to make the data internally consistent. A central source for cleaned geochemical data in the same data format is a valuable resource for further research and exploration in the region.

<div><strong>Output Type: </strong>Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short Abstract: </strong>Groundwater geochemistry is an important and often under-appreciated medium to understand geology below surface and is a valuable tool as part of a regional mineral exploration program. This study presents an assessment of hydrogeochemical results from the Curnamona and Mundi region with respect to their insights into mineral prospectivity and characterisation of groundwater baselines. The work is a collaboration with the Mineral Exploration Cooperative Research Centre (MinEx CRC), the Geological Survey of New South Wales and the Geological Survey of South Australia as part of Geoscience Australia’s Exploring for the Future program. It combines new and legacy groundwater chemistry from 297 samples to identify multiple elevated multi-element anomalies (Ag, Pb, Cd) and signatures of sulfide mineralisation (d34S and sulfur excess), which are interpreted as potential features from subsurface Broken Hill Type mineralisation (Pb-Zn-Ag). Additional multi-element anomalies (Cu, Mo, Co, Au) may be attributable to Cu-Au, Cu-Mo and Au mineralisation. We then apply hierarchical cluster analysis to understand sample hydrostratigraphy and characterise robust hydrogeochemical baselines for the major aquifer systems in the region. This reveals that the majority of anomalies are restricted to groundwaters derived from basement fractured rock aquifer systems, with a couple anomalies observed in the Lake Eyre Basin cover, which helps narrow the search-space for future groundwater-based mineral exploration in this region (to prioritise these aquifers and anomalies). In addition, we demonstrate the capability of these local hydrogeochemical baselines to support more sensitive resolution of hydrogeochemical anomalies relating to mineralisation, as well as reveal hydrogeological processes such as mixing.</div><div><br></div><div><strong>Citation: </strong>Reid, N., Schroder, I., Thorne, R., Folkes, C., Hore, S., Eastlake, M., Petts, A., Evans, T., Fabris, A., Pinchand, T., Henne A., & Palombi, B.R., 2024. Hydrogeochemistry of the Curnamona and Mundi region. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts. Geoscience Australia, Canberra. https://doi.org/10.26186/149509</div>

The stabilities of uranyl-carbonate and uranyl-hydroxide aqueous complexes were experimentally determined at temperatures ranging from 25 to 125 °C using in situ UV–vis and Raman spectroscopic techniques. Combined with earlier determinations of the stability of chloride, sulfate, and hydroxide complexes at temperatures up to 250 °C, these data permit to create a consolidated dataset suitable for modeling of U(VI) mobilization in natural systems. The parameters of the Modified Ryzhenko-Bryzgalin and the Helgeson-Kirkham-Flowers (HKF) Equations of State (EoS) were derived based on this dataset and used for thermodynamic modeling different scenarios of U(VI) mobilization. These models suggest that at conditions relevant to natural systems, carbonate-mediated transport of U(VI) is likely suppressed by the high stability of solid UO2(OH)2 and Na2U2O7. In contrast, sulfate-mediated mobilization mechanisms are highly efficient at acidic and near-neutral pH conditions and can lead to effective hydrothermal mobilization of U(VI). <b>Citation:</b> A. Migdisov, E. Bastrakov, C. Alcorn, M. Reece, H. Boukhalfa, F.A. Capporuscio, C. Jove-Colon, A spectroscopic study of the stability of uranyl-carbonate complexes at 25–150 °C and re-visiting the data available for uranyl-chloride, uranyl-sulfate, and uranyl-hydroxide species, <i>Geochimica et Cosmochimica Acta</i>, 2024, ISSN 0016-7037, https://doi.org/10.1016/j.gca.2024.04.023.

<div>A powerpoint presentation given by Ivan Schroder at Uncover Curnamona 2022. The presentation covers the activities and upcoming products of the Curnamona Geochemistry module (within the Darling Curnamona Delamerian Project of the Exploring for the Future Program)</div>

With the increasing need to extend mineral exploration under cover, new approaches are required to better understand concealed geology, and to narrow the mineral prospectivity search-space. Hydrogeochemistry is a non-invasive exploration technique based on the premise that groundwater interacting with a deposit or supergene alteration can cause anomalous elemental and isotopic signatures down-gradient. Water chemistry can reflect mineralisation directly, but can also reveal other key components of a mineral system, including fluid-flow pathways (e.g. fault/fracture zones), evidence for mineral system traps (e.g. evaporites, shales), or metal sources (e.g. mafic rocks). The Northern Australia Hydrogeochemical Survey (NAHS) was a multiyear regional groundwater sampling program that aimed to understand the regional mineral potential within the Tennant Creek to Mt Isa area (Schroder et al. 2020). This presentation will explore the application of NAHS for investigating mineral potential of a region and present a workflow for establishing spatial or lithological baselines to evaluate hydrogeochemical anomalies. The Georgina Basin is well known for its phosphate potential, with several >1Mt deposits discovered in recent years such as Amaroo and Wonarah; however, the basin has been largely unmapped in terms of phosphate distribution under cover. This work focuses on a subset of 160 NAHS samples collected within two predominant aquifers of the Cambrian Georgina Basin (and time equivalents in the Wiso Basin). This focus restricts us to samples which experience a similar climate, recharge conditions, and aquifer compositions, reducing the hydrogeochemical variation that can mask intra-aquifer anomalies. Elevated dissolved phosphate, PO43- (normalised to HCO3- or Cl-), is observed in the groundwater on the eastern margin of the Georgina Basin. This region is known for Cambrian phosphorite deposits, with sampled bores proximal to a number of near-surface Georgina Basin phosphate deposits. We tested trace element (i.e. U, V and REEs) concentrations as a tool for discriminating phosphate dissolution, however at this regional scale of sampling, possible anomalies were only seen in few bores, thus it is difficult to conclude if this is a consistent relationship robust enough for exploration. More promising may be the use of REE ratios as another indicator of proximity to a phosphate deposit. Emsbo et al. (2015) note that REE compositions of phosphates are relatively consistent globally within a geological period. REE spidergrams of the high PO43- waters are similar to the average REE spidergram of Cambrian phosphates, which contrasts to the REE spidergram of low PO43- groundwaters. Cerium and Europium deviations make this relationship less diagnostic, thus we explore a series of REE ratios (i.e. Er/Dy, Er/Gd, Sm/Nd) for characterising PO43- relationships in groundwater, and use this to suggest other regions of the Georgina Basin with potential for subsurface phosphate deposits. References: Emsbo, P., McLaughlin, P.I., Breit, et al., 2015. Rare earth elements in sedimentary phosphate deposits: solution to the global REE crisis? Gondwana Research, 27(2), 776-785. Schroder, I.F., Caritat, P. de, Wallace, L., et al., 2020. Northern Australia Hydrogeochemical Survey: Final Data Release and Hydrogeochemical Atlas for EFTF. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2020.015 Abstract presented at the 2021 Australian Earth Sciences Convention (AESC)

<div>As part of Geoscience Australia’s Exploring for the Future program, the Curnamona Geochemistry project is producing a comprehensive compilation of geochemical data from the Broken Hill region, encompassing rock, regolith and groundwater. As part of these efforts, geochemical data has been compiled, cleaned and standardised to enable more seamless interpretation and exploration of geochemical anomalies. This project improves the quality, accessibility and volume of geochemical data across the Curnamona region and supports our ongoing efforts to define regional geochemical baselines.</div> This presentation was given to the 2022 Geological Survey of South Australia (GSSA) Discovery Day 1 December (https://www.energymining.sa.gov.au/home/events-and-initiatives/discovery-day)