<div>Strontium isotopes (87Sr/86Sr) are useful to trace processes in the Earth sciences as well as in forensic, archaeological, palaeontological, and ecological sciences. As very few large-scale Sr isoscapes exist in Australia, we have identified an opportunity to determine 87Sr/86Sr ratios on archived fluvial sediment samples from the low-density National Geochemical Survey of Australia (www.ga.gov.au/ngsa; last access: 15 December 2022). The present study targeted the northern parts of Western Australia, the Northern Territory and Queensland, north of 21.5 °S. The samples were taken mostly from a depth of ~60-80 cm in floodplain deposits at or near the outlet of large catchments (drainage basins). A coarse (< 2 mm) grain-size fraction was air-dried, sieved, milled then digested (hydrofluoric acid + nitric acid followed by aqua regia) to release <em>total</em> Sr. The Sr was then separated by chromatography and the 87Sr/86Sr ratio determined by multicollector-inductively coupled plasma mass spectrometry. Results demonstrate a wide range of Sr isotopic values (0.7048 to 1.0330) over the survey area, reflecting a large diversity of source rock lithologies, geological processes and bedrock ages. Spatial distribution of 87Sr/86Sr shows coherent (multi-point anomalies and smooth gradients), large-scale (> 100 km) patterns that appear to be broadly consistent with surface geology, regolith/soil type, and/or nearby outcropping bedrock. For instance, the extensive black clay soils of the Barkly Tableland define a > 500 km-long northwest-southeast-trending unradiogenic anomaly (87Sr/86Sr < 0.7182). Where sedimentary carbonate or mafic/ultramafic igneous rocks dominate, low to moderate 87Sr/86Sr values are generally recorded (medians of 0.7387 and 0.7422, respectively). In proximity to the outcropping Proterozoic metamorphic basement of the Tennant, McArthur, Murphy and Mount Isa geological regions, conversely, radiogenic 87Sr/86Sr values (> 0.7655) are observed. A potential correlation between mineralisation and elevated 87Sr/86Sr values in these regions needs to be investigated in greater detail. Our results to-date indicate that incorporating soil/regolith Sr isotopes in regional, exploratory geoscience investigations can help identify basement rock types under (shallow) cover, constrain surface processes (e.g. weathering, dispersion), and, potentially, recognise components of mineral systems. Furthermore, the resulting Sr isoscape and future models derived therefrom can also be utilised in forensic, archaeological, paleontological and ecological studies that aim to investigate, e.g., past and modern animal (including humans) dietary habits and migrations. The new spatial Sr isotope dataset for the northern Australia region is publicly available (de Caritat et al., 2022a; https://dx.doi.org/10.26186/147473; last access: 15 December 2022).</div> <b>Citation:</b> de Caritat, P., Dosseto, A., and Dux, F.: A strontium isoscape of northern Australia, <i>Earth Syst. Sci. Data</i>, 15, 1655–1673, https://doi.org/10.5194/essd-15-1655-2023, <b>2023</b>.

<div>The soil gas database table contains publicly available results from Geoscience Australia's organic geochemistry (ORGCHEM) schema and supporting oracle databases for gas analyses undertaken by Geoscience Australia's laboratory on soil samples taken from shallow (down to 1 m below the surface) percussion holes. Data includes the percussion hole field site location, sample depth, analytical methods and other relevant metadata, as well as the molecular and isotopic compositions of the soil gas with air included in the reported results. Acquisition of the molecular compounds are by gas chromatography (GC) and the isotopic ratios by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The concentrations of argon (Ar), carbon dioxide (CO₂), nitrogen (N₂) and oxygen (O₂) are given in mole percent (mol%). The concentrations of carbon monoxide (CO), helium (He), hydrogen (H₂) and methane (C₁, CH₄) are given in parts per million (ppm). Compound concentrations that are below detection limit (BDL) are reported as the value -99999. The stable carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N) isotopic ratios are presented in parts per mil (‰) and in delta notation as δ¹³C and δ¹⁵N, respectively.</div><div><br></div><div>Determining the individual sources and migration pathways of the components of natural gases found in the near surface are useful in basin analysis with derived information being used to support exploration for energy resources (petroleum and hydrogen) and helium in Australian provinces. These data are collated from Geoscience Australia records with the results being delivered in the Soil Gas web services on the Geoscience Australia Data Discovery portal at https://portal.ga.gov.au which will be periodically updated.</div>

<div>This study was commissioned by Geoscience Australia (GA) as part of the Exploring for the Future program to produce a report on the organic petrology for rock samples from drill holes of the Birrindudu Basin, Northern Territory, Australia. A suite of 130 drill core samples from 6 drill holes was analysed using standard organic petrological methods to identify the types of organic matter present, assess their relative abundances and determine the levels of thermal maturity attained by the sedimentary organic matter using the reflectance of organoclasts present. </div>

<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>

<div>The fluid inclusion stratigraphy database table contains publicly available results from Geoscience Australia's organic geochemistry (ORGCHEM) schema and supporting oracle databases for Fluid Inclusion Stratigraphy (FIS) analyses performed by FIT, a Schlumberger Company (and predecessors), on fluid inclusions in rock samples taken from boreholes. Data includes the borehole location, sample depth, stratigraphy, analytical methods and other relevant metadata, as well as the mass spectrometry results presented as atomic mass units (amu) from 2 to 180 in parts per million (ppm) electron volts.</div><div> Fluid inclusions (FI) are microscopic samples of fluids trapped within minerals in the rock matrix and cementation phases. Hence, these FIS data record the bulk volatile chemistry of the fluid inclusions (i.e., water, gas, and/or oil) present in the rock sample and determine the relative abundance of the trapped compounds (e.g., in amu order, hydrogen, helium, methane, ethane, carbon dioxide, higher molecular weight aliphatic and aromatic hydrocarbons, and heterocyclic compounds containing nitrogen, oxygen or sulfur). The FI composition can be used to identify the presence of organic- (i.e., biogenic or thermogenic) and inorganic-sourced gases. These data provide information about fluid preservation, migration pathways and are used to evaluate the potential for hydrocarbon (i.e. dry gas, wet gas, oil) and non-hydrocarbon (e.g., hydrogen, helium) resources in a basin. These data are collated from Geoscience Australia records, destructive analysis reports (DARs) and well completion reports (WCRs), with the results being delivered in the Fluid Inclusion Stratigraphy (FIS) web services on the Geoscience Australia Data Discovery Portal at https://portal.ga.gov.au which will be periodically updated.</div>

<div>We present the first national-scale lead (Pb) isotope maps of Australia based on surface regolith for five isotope ratios, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁶Pb, and ²⁰⁸Pb/²⁰⁶Pb, determined by single collector Sector Field-Inductively Coupled Plasma-Mass Spectrometry after an Ammonium Acetate leach followed by Aqua Regia digestion. The dataset is underpinned principally by the National Geochemical Survey of Australia (NGSA) archived floodplain sediment samples. We analysed 1219 ‘top coarse’ (0-10 cm depth, &lt;2 mm grain size) samples, collected near the outlet of 1098 large catchments covering 5.647 million km2 (~75% of Australia). This paper focusses on the Aqua Regia dataset. The samples consist of mixtures of the dominant soils and rocks weathering in their respective catchments (and possibly those upstream) and are therefore assumed to form a reasonable representation of the average isotopic signature of those catchments. This assumption was tested in one of the NGSA catchments, within which 12 similar ‘top coarse’ samples were also taken; results show that the Pb isotope ratios of the NGSA catchment outlet sediment sample are close to the average of the 12 sub-catchment, upstream samples. National minimum, median and maximum values reported for ²⁰⁶Pb/²⁰⁴Pb were 15.558, 18.844, 30.635; for ²⁰⁷Pb/²⁰⁴Pb 14.358, 15.687, 18.012; for ²⁰⁸Pb/²⁰⁴Pb 33.558, 38.989, 48.873; for ²⁰⁷Pb/²⁰⁶Pb 0.5880, 0.8318, 0.9847; and for ²⁰⁸Pb/²⁰⁶Pb 1.4149, 2.0665, 2.3002, respectively. The new dataset was compared with published bedrock and ore Pb isotope data, and was found to dependably represent crustal elements of various ages from Archean to Phanerozoic. This suggests that floodplain sediment samples are a suitable proxy for basement and basin geology at this scale, despite various degrees of transport, mixing, and weathering experienced in the regolith environment, locally over protracted periods of time. An example of atmospheric Pb contamination around Port Pirie, South Australia, where a Pb smelter has operated since the 1890s, is shown to illustrate potential environmental applications of this new dataset. Other applications may include elucidating detail of Australian crustal evolution and mineralisation-related investigations.&nbsp;</div> <b>Citation:</b> Desem, C. U., de Caritat, P., Woodhead, J., Maas, R., and Carr, G.: A regolith lead isoscape of Australia, <o>Earth Syst. Sci. Data</i>, 16, 1383–1393, https://doi.org/10.5194/essd-16-1383-2024, 2024.

Major oxides provide valuable information about the composition, origin, and properties of rocks and regolith. Analysing major oxides contributes significantly to understanding the nature of geological materials and processes (i.e. physical and chemical weathering) – with potential applications in resource exploration, engineering, environmental assessments, agriculture, and other fields. Traditionally most measurements of oxide concentrations are obtained by laboratory assay, often using X-ray fluorescence, on rock or regolith samples. To expand beyond the point measurements of the geochemical data, we have used a machine learning approach to produce seamless national scale grids for each of the major oxides. This approach builds predictive models by learning relationships between the site measurements of an oxide concentration (sourced from Geoscience Australia’s OZCHEM database and selected sites from state survey databases) and a comprehensive library of covariates (features). These covariates include: terrain derivatives; climate surfaces; geological maps; gamma-ray radiometric, magnetic, and gravity grids; and satellite imagery. This approach is used to derive national predictions for 10 major oxide concentrations at the resolution of the covariates (nominally 80 m). The models include the oxides of silicon (SiO2), aluminium (Al2O3), iron (Fe2O3tot), calcium (CaO), magnesium (MgO), manganese (MnO), potassium (K2O), sodium (Na2O), titanium (TiO2), and phosphorus (P2O5). The grids of oxide concentrations provided include the median of multiple models run as the prediction, and lower and upper (5th and 95th) percentiles as measures of the prediction’s uncertainty. Higher uncertainties correlate with greater spreads of model values. Differences in the features used in the model compared with the full feature space covering the entire continent are captured in the ‘covariate shift’ map. High values in the shift model can indicate higher potential uncertainty or unreliability of the model prediction. Users therefore need to be mindful, when interpreting this dataset, of the uncertainties shown by the 5th-95th percentiles, and high values in the covariate shift map. Details of the modelling approach, model uncertainties and datasets are describe in an attached word document “Model approach uncertainties”. This work is part of Geoscience Australia’s Exploring for the Future program that 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. These data are published with the permission of the CEO, Geoscience Australia.

<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>

<div>The noble gas database table contains publicly available results from Geoscience Australia's organic geochemistry (ORGCHEM) schema and supporting oracle databases for molecular and noble gas isotopic analyses on natural gases sampled from boreholes and fluid inclusion gases from rocks sampled in boreholes and field sites. Data includes the borehole or field site location, sample depths, shows and tests, stratigraphy, analytical methods, other relevant metadata, and the molecular and noble gas isotopic compositions for the natural gas samples. The molecular data are presented in mole percent (mol%) and cubic centimetres (at Standard Pressure and Temperature) per cubic centimetre (ccSTP/cc). The noble gas isotopic values that can be measured are; Helium (He, ³He, ⁴He), Neon (Ne, ²⁰Ne, ²¹Ne, ²²Ne), Argon (Ar, ³⁶Ar, ³⁸Ar, ⁴⁰Ar), Krypton (Kr, ⁷⁸Kr, ⁸⁰Kr, ^82<Kr, ⁸³Kr, ⁸⁴Kr, ⁸⁶Kr) and Xenon (Xe, ¹²⁴Xe, ¹²⁶Xe, ¹²⁸Xe, ¹²⁹Xe, ¹³⁰Xe, ¹³¹Xe, ¹³²Xe, ¹³⁴Xe, ¹³⁶Xe) which are presented in cubic micrometres per cubic centimetre (mcc/cc), cubic nanometres per cubic centimetre (ncc/cc) and cubic picometres per cubic centimetre (pcc/cc). Acquisition of the molecular compounds are by gas chromatography (GC) and the isotopic ratios by mass spectrometry (MS). Compound concentrations that are below the detection limit (BDL) are reported as the value -99999.</div><div><br></div><div>These data provide source information about individual compounds in natural gases and can elucidate fluid migration pathways, irrespective of microbial activity, chemical reactions and changes in oxygen fugacity, which are useful in basin analysis with derived information being used to support Australian exploration for energy resources and helium. These data are collated from Geoscience Australia records and well completion reports. The noble gas data for natural gases and fluid inclusion gases are delivered in the Noble Gas Isotopes web services on the Geoscience Australia Data Discovery Portal at https://portal.ga.gov.au which will be periodically updated.</div><div><br></div><div><br></div>

<div>Strontium isotopes (87Sr/86Sr) are useful in the earth sciences (e.g. recognising geological provinces, studying geological processes) as well in archaeological (e.g. informing on past human migrations), palaeontological/ecological (e.g. investigating extinct and extant taxa’s dietary range and migrations) and forensic (e.g. validating the origin of drinks and foodstuffs) sciences. Recently, Geoscience Australia and the University of Wollongong have teamed up to determine 87Sr/86Sr ratios in fluvial sediments selected mostly from the low-density National Geochemical Survey of Australia (www.ga.gov.au/ngsa), with a few additional Northern Australia Geochemical Survey infill samples. The present study targeted the northern parts of Western Australia, the Northern Territory and Queensland in Australia, north of 21.5 °S. The samples were taken mostly from a depth of ~60-80 cm depth in floodplain deposits at or near the outlet of large catchments (drainage basins). A coarse grain-size fraction (&lt;2 mm) was air-dried, sieved, milled then digested (hydrofluoric acid + nitric acid followed by aqua regia) to release total strontium. Preliminary results demonstrate a wide range of strontium isotopic values (0.7048 &lt; 87Sr/86Sr &lt; 1.0330) over the survey area, reflecting a large diversity of source rock lithologies, geological processes and bedrock ages. Spatial distribution of 87Sr/86Sr shows coherent (multi-point anomalies and smooth gradients), large-scale (&gt;100 km) patterns that appears to be consistent, in many places, with surface geology, regolith/soil type and/or nearby outcropping bedrock. For instance, the extensive black clay soils of the Barkly Tableland define a &gt;500 km-long northwest-southeast-trending low anomaly (87Sr/86Sr &lt; 0.7182). Where carbonate or mafic igneous rocks dominate, a low to moderate strontium isotope signature is observed. In proximity to the outcropping Proterozoic metamorphic provinces of the Tennant, McArthur, Murphy and Mount Isa geological regions, conversely, high 87Sr/86Sr values (&gt; 0.7655) are observed. A potential link between mineralisation and elevated 87Sr/86Sr values in these regions needs to be investigated in greater detail. Our results to-date indicate that incorporating soil/regolith strontium isotopes in regional, exploratory geoscience investigations can help identify basement rock types under (shallow) cover, constrain surface processes (e.g. weathering, dispersion), and, potentially, recognise components of mineral systems. Furthermore, the resulting strontium isoscape and model derived therefrom can also be utilised in archaeological, paleontological and ecological studies that aim to investigate past and modern animal (including humans) dietary habits and migrations. &nbsp;The new spatial dataset is publicly available through the Geoscience Australia portal https://portal.ga.gov.au/.</div>