This was the first study of its kind, by the Commonwealth team. The study included demonstrations of the dithizone tests for traces of some heavy metals in the field environment, of operational and sampling procedures, and geochemical reconnaissance. Several reconnaissance traverses were sampled and examined. Extractable forms of copper and, in a very presumptive manner, extractable forms of lead and zinc were sought in the test materials. In addition, tests for copper, lead and zinc were made in some ignited and fused specimens. The testing procedure and results are described in this report.

The Walloon Coal Measures (WCM) in the Clarence-Moreton and the Surat basins in Qld and northern NSW contain up to approximately 600 m of mudstone, siltstone, sandstone and coal. Wide-spread exploration for coal seam gas (CSG) within both basins has led to concerns that the depressurisation associated with the resource development may impact on water resources in adjacent aquifers. In order to predict potential impacts, a detailed understanding of sedimentary basins hydrodynamics that integrates geology, hydrochemistry and environmental tracers is important. In this study, we show how different hydrochemical parameters and isotopic tracers (i.e. major ion chemistry, dissolved gas concentrations, 13C-DIC, 18O, 87Sr/86Sr, 3H, 14C, 2H and 13C of CH4) can help to improve the knowledge on groundwater recharge and flow patterns within the coal-bearing strata and their connectivity with over- or underlying formations. Dissolved methane concentrations in groundwaters of the WCM in the Clarence-Moreton Basin range from below the reporting limit (10 µg/L) to approximately 50 mg/L, and samples collected from nested bore sites show that there is also a high degree of vertical variability. Other parameters such as groundwater age measurements collected along distinct flow paths are also highly variable. In contrast, 87Sr/86Sr isotope ratios of WCM groundwaters are very uniform and distinct from groundwaters contained in other sedimentary bedrock units, suggesting that 87Sr/86Sr ratios may be a suitable tracer to study hydraulic connectivity of the Walloon Coal Measures with over- or underlying aquifers, although more studies on the systematic are required. Overall, the complexity of recharge processes, aquifer connectivity and within-formation variability confirms that a single tracer that cannot provide all information necessary to understand aquifer connectivity in these sedimentary basins, but that a multi-tracer approach is required.

Geochemical tracers have been used for many years to improve the understanding of reservoir dynamics in geothermal systems. Tracers can be classified as either conservative or reactive, and can be used in liquid-phase, vapour-phase or two-phase reservoirs at temperatures of 300C or more. They are commonly used to map flow pathways between injection and production wells in a geothermal field, to monitor the effects of reinjection and identify wells that might experience premature thermal breakthrough if left unmanaged. Tracer tests also provide information about reservoir fluid residence time, fluid recharge location or direction, swept pore volumes, inter-well connectivity, temperatures, fracture surface area, flow-storage capacity relationships and volumetric fluid sweep efficiencies. In addition, tracer data can be used with numerical transport codes to help validate 2D or 3D reservoir models. Thus, tracer tests can provide powerful insight into geothermal reservoir characteristics, and they can be performed at many stages of project development, from small-scale demonstration projects (e.g. an injection-production well doublet) through to large-scale commercial fields (e.g. Wairakei, New Zealand). New 'smart' tracers have the potential to be used with a single well to evaluate changes in fracture surface area following reservoir stimulation, and thus have applications to both conventional and unconventional (engineered) geothermal projects.

This resource contains surface sediment data for Bynoe Harbour collected by Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and Department of Land Resource Management (Northern Territory Government) during the period from 2-29 May 2016 on the RV Solander (survey SOL6432/GA4452). This project was made possible through offset funds provided by INPEX-led Ichthys LNG Project to Northern Territory Government Department of Land Resource Management, and co-investment from Geoscience Australia and Australian Institute of Marine Science. The intent of this four year (2014-2018) program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps that underpin marine resource management decisions. The specific objectives of the survey were to: 1. Obtain high resolution geophysical (bathymetry) data for outer Darwin Harbour, including Shoal Bay; 2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for outer Darwin Harbour, including Shoal Bay; and 3. Collect tidal data for the survey area. Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; physical samples of seabed sediments, underwater photography and video of grab sample locations and oceanographic information including tidal data and sound velocity profiles. This dataset comprises total sediment metabolism, carbonate and element concentrations and C and N isotopes measurements made on seabed sediments. A detailed account of the survey is provided in Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas W.A., Picard, K., Radke, L.C., Tran, M., Williams, D. and Whiteway, T., 2016. Bynoe Harbour Marine Survey 2017: GA4452/SOL6432 – Post-survey report. Record 2017/04. Geoscience Australia, Canberra. Thanks to the crew of the RV Solander for help with sample collection, Matt Carey, Craig Wintle and Andrew Hislop from the Observatories and Science Support at Geoscience Australia for technical support and Jodie Smith for reviewing the data. This dataset is published with the permission of the CEO, Geoscience Australia.

This report presents the location and sources of sediment samples and observational data in the Vestfold Hills (between 68° 23' and 68° 40' S, 77° 50' and 78° 35' E) to provide physical and chemical properties, sedimentary processes, and glacial and marine history of the terrestrial environment. This compilation of samples and observations incorporates data collected from the 1970s to present from published and unpublished sources. Sample locations and types are presented here to make them more readily available for further analysis and interpretation. Samples and observations are presented as point locations and include sample type, analyses, and references to the original data source.

Regolith carbonate or secondary carbonate is a key component of the regolith, particularly in many Mediterranean, arid and semi-arid regions of Australia. National maps of regolith carbonate distribution have been compiled from regional soil, regolith and geological mapping with varying degrees of confidence and consistency. Here we apply a decision tree approach based on a piecewise linear regression model to estimate and map the near-surface regolith carbonate concentration at the continental scale. The model is based on relationships established from the 1311 field sites of the National Geochemical Survey of Australia (NGSA) and 49 national environmental covariate datasets. Regolith carbonate concentration (weight %) was averaged from the <2 mm grain size-fractions of samples taken from two depth ranges (0-10 cm and ~60-80 cm) at each NGSA site. The final model is based on the average of 20 runs generated by randomly selecting 90% training and 10% validation splits of the input data. Results present an average coefficient of determination (R2) of 0.56 on the validation dataset. The covariates used in the prediction are consistent with our understanding of the controls on the sources (inputs), preservation and distribution of regolith carbonate within the Australian landscape. The model produces a continuous, quantitative prediction of regolith carbonate abundance in surficial regolith at a resolution of 90 m with associated estimates of model uncertainty. The model-derived map is broadly consistent with our current knowledge of the distribution of carbonate-rich soil and regolith in Australia. This methodology allows the rapid generation of an internally consistent and continuous layer of geoinformation that may be applicable to other carbonate-rich landscapes globally. The methodology used in this study has the potential to be used in predicting other geochemical constituents of the regolith.

This service provides access to inorganic geochemistry data obtained from chemical analyses of rock and regolith samples collected during mapping and sampling programs in Australia. This service will provide a spatial distribution of the sample attributes as well as provide a spatial distribution of the analytical composition of the samples with respect to major elements, minor elements and rare earth elements. This service includes original inorganic geochemistry data levelled to reference datasets.

Mafic igneous rocks are thought to be an important source of metals for the ca. 1640–1595 Ma sediment-hosted base metal deposits in the Paleo- to Mesoproterozoic Mount Isa – McArthur Basin system of northern Australia. Such rocks are widespread—the voluminous rift-related mafic magmatism at ca. 1790–1775 Ma and ca. 1730–1710 Ma—and show local evidence for intense hydrothermal alteration and metal leaching. To better constrain the nature, degree, and regional and temporal extent of alteration and metal leaching in these rocks, we have undertaken regional sampling of mafic igneous units from available drillcore, for geochemistry, stable isotopes and petrological examination. Sampling focused on magmatism of both ages in the southeastern MacArthur Basin, complementing the extensive pre-existing data for the Mount Isa region. Alteration in the mafic igneous rocks of the southeastern McArthur Basin ranges from mildly to strongly chloritic in the older units to strongly potassic (K-feldspar–chlorite–hematite) in the younger units. The latter alteration is ubiquitous, well developed and characterised by strong K2O enrichment and extreme depletion in CaO and Na2O. Geochemical data show that this intense and pervasive potassic alteration extends to similar-aged mafic rocks in the western Mount Isa region. Metal leaching is present in both alteration types, with strong Cu and Pb depletion in the most chlorite-altered rocks, and Zn and Cu depletion in the potassic alteration. Our oxygen isotope data for these mafic rocks (of both ages) in the southeastern McArthur Basin show a limited range of values (δ18O of 6–10‰) that are negatively correlated with K2O content. Our values are significantly lighter than published data for similar igneous rocks to the west, and indicate either a temperature zonation (ca. 250 °C in the east versus ca. 100 °C in the west; preferred) and/or different fluids. Results from our geochemical forward modelling indicate the requirement for exogenous K2O to produce the observed potassic alteration. The most likely source of this K was saline brines, consistent with the interpreted lacustrine and/or evaporitic environments for much of the McArthur Basin. Timing of alteration is uncertain, and the alteration may have included diagenetic low-temperature local K-rich brines and younger higher-temperature deep basinal brines. The temporal and geographically restricted nature of the potassic alteration, however, suggests restriction of K-rich, bittern evaporitic brine production in the younger and inboard parts of the Mount Isa – McArthur Basin system. Our results provide insights that directly relate to the genesis and exploration of basin-hosted Zn-Pb and Cu-Co mineral systems. They confirm that mafic igneous rocks in the region have lost significant amounts of both Zn and Cu, many times more than required for known deposits. The study also shows that metal leaching was accompanied by magnetite-destructive alteration. Hence, identifying zones of metal leaching may be possible using inversions of geophysical data, which may assist in targeting exploration. <b>Citation:</b> Champion, D.C., Huston, D.L., Bastrakov, E., Siegel, C., Thorne, J., Gibson, G.M. and Hauser, J., 2020. Alteration of mafic igneous rocks of the southern McArthur Basin: comparison with the Mount Isa region and implications for basin-hosted base metal deposits. 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 Congararra 1 borehole was drilled approximately 70 km NNW of Bourke, NSW. The borehole was designed to test aeromagnetic anomalies in the basement rocks, test the electrical conductivity properties of cover and basement rocks to validate airborne electromagnetic (AEM) data, and to test pre-drilling geophysical cover thickness estimates.

This web service delivers datasets produced by the Critical Minerals Mapping Initiative (CMMI), a collaboration between Geoscience Australia (GA), the Geological Survey of Canada (GSC) and the United States Geological Survey (USGS). Data in this service includes geochemical analyses of over 7000 samples collected from or near mineral deposits from 60 countries, and mineral prospectivity models for clastic-dominated (Zn, Pb) and Mississippi Valley-type (Zn-Pb) deposits across Canada, the United States, and Australia.