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Australian sediment-hosted mineral systems are important sources of base metals and critical minerals that are vital to delivering Australia’s low-carbon economy. In Australia, sediment-hosted resources account for ~82% and ~86% of the total zinc (Zn) and lead (Pb) resources respectively. Given their significance to the Australian economy, four national-scale mineral potential models for sediment-hosted Zn-Pb mineral systems have been developed: clastic-dominated siliciclastic carbonate, clastic-dominated siliciclastic mafic, Mississippi Valley-type and Irish-type. In addition to the potential for Zn-Pb mineralisation, the uncertainty related to data availability has been examined. The mineral potential models were created using a mineral systems-based approach where mappable criteria have been used to assess the prospectivity of each system. Each model has been derived from a large volume of precompetitive geoscience data. The clastic-dominated siliciclastic carbonate mineral potential model predicts 92% of known deposits and occurrences within 15.5% of the area, the clastic-dominated siliciclastic mafic mineral potential model predicts 85% of deposits and occurrences within 27% of the area, and the Mississippi Valley-type mineral potential model predicts 66% of known deposits and occurrences within 31% of the area. Each model successfully predict the location of major sediment-hosted Zn-Pb deposits while highlighting new areas of elevated prospectivity in under-explored regions of Australia, reducing the exploration search space by up to 85% for sediment-hosted Zn-Pb mineral systems.

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)

Multi-element geochemical surveys of rocks, soils, stream/lake/floodplain sediments and regolith are typically carried out at continental, regional and local scales. The chemistry of these materials is defined by their primary mineral assemblages and their subsequent modification by comminution and weathering. Modern geochemical datasets represent a multi-dimensional geochemical space that can be studied using multivariate statistical methods from which patterns reflecting geochemical/geological processes are described (process discovery). These patterns form the basis from which probabilistic predictive maps are created (process validation). Processing geochemical survey data requires a systematic approach to effectively interpret the multi-dimensional data in a meaningful way. Problems that are typically associated with geochemical data include closure, missing values, censoring, merging, levelling different datasets and adequate spatial sample design. Recent developments in advanced multivariate analytics, geospatial analysis and mapping provide an effective framework to analyse and interpret geochemical datasets. Geochemical and geological processes can often be recognized through the use of data discovery procedures such as the application of principal component analysis. Classification and predictive procedures can be used to confirm lithological variability, alteration and mineralization. Geochemical survey data of lake/till sediments from Canada and of floodplain sediments from Australia show that predictive maps of bedrock and regolith processes can be generated. Upscaling a multivariate statistics-based prospectivity analysis for arc-related Cu–Au mineralization from a regional survey in the southern Thomson Orogen in Australia to the continental scale, reveals a number of regions with a similar (or stronger) multivariate response and hence potentially similar (or higher) mineral potential throughout Australia. Thematic collection: This article is part of the Exploration 17 collection available at: https://www.lyellcollection.org/cc/exploration-17

Bulk quantitative mineralogy of regolith is a useful indicator of lithological precursor (protolith), degree of weathering, and soil properties affecting various potential landuse decisions. To date, no national-scale maps of regolith mineralogy are available in Australia. Catchment outlet sediments collected over 80% of the continent as part of the National Geochemical Survey of Australia (NGSA) afford a unique opportunity to rapidly and cost-effectively determine regolith mineralogy using the archived sample material. This report releases mineralogical data and metadata obtained as part of a feasibility study in a selected pilot area for such a national regolith mineralogy database and atlas. The area chosen for this study is within the Darling-Curnamona-Delamerian (DCD) region of southeastern Australia. The DCD region was selected as a ‘deep-dive’ data acquisition and analysis by the Exploration for the Future (2020-2024) federal government initiative managed at Geoscience Australia. One hundred NGSA sites from the DCD region were prepared for X-Ray Diffraction (XRD) analysis, which consisted of qualitative mineral identification of the bulk samples (i.e., ‘major’ minerals), qualitative clay mineral identification of the

Geochemical Processes, Weathering and Groundwater Recharge in Catchments is a specialist book concerned with the natural processes taking place where water interacts with minerals and organic matter at the earth's surface, in soils or within aquifers. It focuses on the all important interface between the hydrological and geochemical cycles in terrestrial ecosystems, and is thus particularly relevant to understanding the environment. The book is intended primarily as a reference text for graduate students in Earth Sciences, Hydrology or Environmental Sciences, but will be a useful introduction to those studying Chemistry, Biology or Forestry Studies. Geochemical Processes, Weathering and Groundwater Recharge in Catchments presents an overview of the current status of knowledge of catchment studies, with an outline of the challenges of future research. .

‘Environmental isotopes’ are those isotopes that are widespread in nature and are part of the hydrological and/or geological cycle. This chapter describes the use of oxygen, hydrogen, carbon, nitrogen and sulphur isotopes. The selection is based on the fact that these isotopes are the ones most frequently studied in catchments, and very applicable for the study of catchments where the storage time of water is relatively short. Northern catchments such as in Scandinavia often are characterised by rather rugged topography, and well-defined catchment boundaries. River discharges have strong seasonal variations with snow melt as the main flood event. Rather thin unconsolidated glacial sediments, mostly tills, cover the lithified bedrock. In isotopic hydrograph separation the streamwater is normally separated into flows of new water (event water) and old water. Old water is water that was already in the catchment before the runoff event.

We collected 38 groundwater and two surface-water samples in the semi-arid Lake Woods region of the Northern Territory to better understand the hydrogeochemistry of this system, which straddles the...

The multi-element aqua regia National Geochemical Survey of Australia (NGSA) database is used to demonstrate an improved method for quantifying the degree of geochemical similarity (DOGS2) between soil samples. The improvements introduced here address issues relating to compositional data (closure, relative scale). After removing the elements with excessive censored (below detection) values, the rank-based Spearman correlation coefficient (rs) between samples is calculated for the remaining 51 elements. Each element is given equal weight through the rank-based correlation. The rs values for pairs of samples of known similar origin (e.g. granitoid-derived) are significantly positive, whereas they are significantly negative for pairs of samples of known dissimilar origin (e.g. granitoid- v. greenstone-derived). Maps of rs for all samples in the database against various reference samples are used to obtain correlation maps for lithological derivations. Likewise, the distribution of soils having a geochemical fingerprint similar to established mineralized provinces can be mapped, providing a simple, first order mineral prospectivity tool. Sensitivity of results to the removal of up to a dozen elements from the correlation indicates the method to be extremely robust. The new method is compliant with contemporary compositional data analysis principles and is applicable to various digestion methods.

During the last 10–20 years, Geological Surveys around the world have undertaken a major effort towards delivering fully harmonised and tightly quality controlled low-density multi-element soil geochemical maps and datasets of vast regions including up to whole continents. Concentrations of between 45 and 60 elements commonly have been determined in a variety of different regolith types (e.g., sediment, soil). The multi-element datasets are published as complete geochemical atlases and made available to the general public. Several other geochemical datasets covering smaller areas, but generally at a higher spatial density, are also available. These datasets may, however, not be found by superficial internet-based searches because the elements are not mentioned individually either in the title or in the keyword lists of the original references. This publication attempts to increase the visibility and discoverability of these fundamental background datasets covering large areas up to whole continents.

The results of a pilot study into the application of an unsupervised clustering approach to the analysis of catchment-based National Geochemical Survey of Australia (NGSA) geochemical data combined with geophysical and geological data across northern Australia are documented. NGSA Mobile Metal Ion® (MMI) element concentrations and first and second order statistical summaries across catchments of geophysical data and geological data are integrated and analysed using Self-Organizing Maps (SOM). Input features that contribute significantly to the separation of catchment clusters are objectively identified and assessed. A case study of the application of SOM for assessing the spatial relationships between Au mines and mineral occurrences in catchment clusters is presented. Catchments with high mean Au code-vector concentrations are found downstream of areas known to host Au mineralization. This knowledge is used to identify upstream catchments exhibiting geophysical and geological features that indicate likely Au mineralization. The approach documented here suggests that catchment-based geochemical data and summaries of geophysical and geological data can be combined to highlight areas that potentially host previously unrecognised Au mineralization.

Understanding the character of Australia's extensive regolith cover is crucial to the continuing success of mineral exploration. We hypothesise that the regolith contains geochemical fingerprints of processes related to the development and preservation of mineral systems at a range of scales. We test this hypothesis by analysing the composition of surface sediments within greenfield regional-scale (southern Thomson Orogen) and continental-scale (Australia) study areas. In the southern Thomson Orogen area, the first principal component (PC1) derived in our study [Ca, Sr, Cu, Mg, Au and Mo at one end; rare earth elements (REEs) and Th at the other] is very similar to the empirical vector used by a local company (enrichment in Sr, Ca and Au concomitant with depletion in REEs) to successfully site exploration drill holes for Cu–Au mineralisation. Mapping of the spatial distribution of PC1 in the region reveals several areas of elevated values and possible mineralisation potential. One of the strongest targets in the PC1 map is located between Brewarrina and Bourke in northern New South Wales. Here, exploration drilling has intersected porphyry Cu–Au mineralisation with up to 1 wt% Cu, 0.1 g/t Au, and 717 ppm Zn. The analysis of a comparable geochemical dataset at the continental scale yields a compositionally similar PC1 (Ca, Sr, Mg, Cu, Au and Mo at one end; REEs and Th at the other) to that of the regional study. Mapping PC1 at the continental scale shows patterns that (1) are spatially compatible with the regional study and (2) reveal several geological regions of elevated values, possibly suggesting an enhanced potential for porphyry Cu–Au mineralisation. These include well-endowed mineral provinces such as the Curnamona and Capricorn regions, but also some greenfield regions such as the Albany-Fraser/western Eucla, western Murray and Eromanga geological regions. We conclude that the geochemical composition of Australia's regolith may hold critical information pertaining to mineralisation within/beneath it.

This study reviews the available information for over 1200 Australian salt lakes including in areas that have little or unreliable data. Publicly available groundwater hydrogeochemical datasets for the Australian arid zone are particularly sparse, inconsistent and of variable quality. Many datasets in the vicinity of salt lakes only report salinity or total dissolved solids, with no data for constituent cations and anions, and no appreciation of the hydrological and geomorphic evolution of the lakes. To overcome these limitations and to provide a broad-scale context, we developed mineral systems models to assess the potential of Australian salt lakes for potash, lithium and boron deposits. These models show that an important control on the potential of salt lake systems to form economic deposits of potash, lithium or boron is hydrogeological connectivity between leachable source rocks and the lakes. The assessment of the mineral potential was carried out in two stages. The first stage selection wa...

The 42 element, 1190 sample Mobile Metal Ion subset of the National Geochemical Survey of Australia database was used to develop and illustrate the concept of Degree of Geochemical Similarity of soil samples. Element concentrations were unified to parts per million units and log(10)-transformed. The degree of similarity of pairs of samples of known provenance in the Yilgarn Craton was obtained using least-squares linear regression analysis and demonstrated that the method successfully assessed the degree of similarity of soils related to granitoid and greenstone lithologies. Exploratory Data Analysis symbol maps of all remaining samples in the database against various reference samples were used to obtain correlation maps not only for granitoid- and greenstone-related soil types but also to distinguish between, for example, samples derived from marine vs regolith carbonate. Likewise, the distribution of soil samples having a geochemical fingerprint similar to mineralised provinces (e.g. Mount Isa)...

We investigate the characteristics of regolith through the application of statistical learning to diverse layers of terrestrial, continental-scale remote sensing data. This combination allows us to explore the multiple influences of bedrock, climate, biota, landscape and time on regolith development and properties: an interdisciplinary geoscience modeling problem. From a wide variety of available data for Australia, we select remotely sensed geophysical, geomorphological and mineralogical inputs with good spatial coverage. We use Self-Organizing Maps (SOM), a topologically constrained unsupervised statistical learning algorithm, to characterize the geophysical and mineralogical signatures of regolith and bedrock. Regolith materials cover more than 80% of the Australian continent, range in age from Precambrian to Quaternary and vary in thickness from less than a meter to more than a kilometer. The diversity of regolith cover type and character across Australia provides an opportunity to demonstrate knowledge discovery from remote sensing data. The outputs of our SOM analysis are combined with ground observations from locations showing naturally occurring anomalous concentrations of nickel, tin and uranium. We identify a minimum number of natural clusters indicating subtle but significant differences in regolith and bedrock mineralization characteristics. Our results show that SOM identifies spatially contiguous regions representing unique regolith and bedrock materials. In the Yilgarn Craton we observe key differences in landscape character, density of the crust, and relative abundance of radioactive elements and alumino-silicate and ferric oxide minerals. These properties discriminate between nickel-prospective residual deeply weathered regolith formed on mafic and/or ultramafic bedrock and uranium-prospective Cainozoic paleochannels containing felsic bedrock source materials. National-scale data are publicly available for many continental regions, as in the Australian example, and our approach has general applicability. We demonstrate that remote sensing data may be used to understand the regolith, revealing the interplay between environmental history and bedrock character at regional scales, and differences between residual and transported regolith, provenance of source materials and their relative ages.

The National Geochemical Survey of Australia (NGSA) was carried out to bridge a vast knowledge gap about the concentration and distribution of chemical elements at the Earth’s surface in Australia and consequent poor understanding of processes controlling their distribution here. The aim of the project was to contribute to improving exploration for energy and mineral resources through the pre-competitive delivery of a new spatial layer of compositional data and information. Surface (0–10 cm depth) and shallow ( c . 60–80 cm) samples of catchment outlet sediments were collected from 1315 sites located near the outlet of 1186 catchments ( c . 10% of which were sampled in duplicate) from across Australia. The total area covered by the survey was 6.174 million km 2 , or c . 81% of Australia, at an average sampling density of 1 site per c . 5200 km 2 . A number of field parameters (e.g. soil colour, pH), bulk parameters (e.g. electrical conductivity, particle size distribution) and geochemical parameters (i.e. multi-element composition of dry sieved These data were collated into a spreadsheet and graphically represented as a series of 529 geochemical maps (http://www.ga.gov.au/ngsa). These constitute the first continental-scale series of geochemical maps for Australia based on internally consistent, state-of-the-art data pertaining to the same sampling medium collected, prepared and analysed in a uniform and thoroughly documented manner and over a short time period. They are being used to better understand the accumulation, mobility and significance of chemical elements in the near-surface environment. Applications to date and ongoing and future directions are discussed. Supplementary material: Appendices 1-4 of summary statistics are available at http://www.geolsoc.org.uk/SUP18853

Chlorine and bromine play crucial roles in atmospheric element cycles and are important environmental tracers in catchment investigations, so understanding their distribution at the Earth's near-surface is imperative for deciphering their behaviour. This study presents the first continental-scale analysis of Cl- and Br- concentrations of wet deposition, based on six and half years of weekly samples collected across North America. A recently developed imputation algorithm was applied to estimate the high proportion of censored Br- values, as well as the other eight analytes, based on the multivariate relationships of nine analytes. The results are consistent with previous studies that have found that the concentrations of these two ions in wet deposition, and the Cl-/Br- ratios of wet deposition decrease with distance inland. Close to the coast, Cl-/Br- ratios of wet deposition are similar to the ratio found in seawater (~288 by mass), rapidly decrease to approximately a third of the seawater ratio at ~200km inland, and then decrease at a much lesser rate to reach mass-ratios of 20 to 10 at ~1500km inland, following a logarithmic regression. The Niagara Falls and the Great Salt Lake are identified as localised sources of atmospheric solutes based on elevated Cl-/Br- ratios of wet deposition at proximal sites. Our observations provide further confidence in the findings presented in previous studies that have shown that Cl-/Br- ratios systematically decrease with increasing distance from the coast, despite the potential confounding impact of other processes, such as weather patterns, chemical behaviour and anthropogenic activity. Our results provide improved estimates of Cl-/Br- ratios of wet deposition source water in the absence of site-specific data.

Catchment outlet sediments (0-10 cm depth, sieved to

We describe the information content of soil visible–near infrared (vis–NIR) reflectance spectra and map their spatial distribution across Australia. The spectra of 4030 surface soil samples from across the country were measured with a vis–NIR spectrometer in the range 350 to 2500 nm. The spectra were compressed by a principal component analysis (PCA) and the resulting scores were mapped by ordinary point kriging. The largely dominant and common feature in the maps was the difference between the more expansive, older and more weathered landscapes in the centre and west of Australia and the generally younger, more complex landscapes in the east. A surface soil class map derived from the clustering of the principal components was similar to an existing soil classification map. We show that vis–NIR reflectance spectra (i) provide a rapid and efficient integrative measure of the composition of the soil, (ii) can replace the use of traditional soil properties to describe the soil and make pedological interpretations of its spatial distribution and (iii) can be used to classify soil objectively.

Pb is one of the most widespread and metal pollutants in soil. It is generally concentrated in surface layers with only a minor portion of the total metal found in soil solution. Phytoextraction has been proposed as an inexpensive, sustainable, in situ plant-based technology that makes use of natural hyperaccumulators as well as high biomass producing crops to help rehabilitate soils contaminated with heavy metals without destructive effects on soil properties. The success of phytoextraction is determined by the amount of biomass, concentration of heavy metals in plant, and bioavailable fraction of heavy metals in the rooting medium. In general, metal hyperaccumulators are low biomass, slow growing plant species that are highly metal specific. For some metals such as Pb, there are no hyperaccumulator plant species known to date. Although high biomass-yielding non-hyperaccumulator plants lack an inherent ability to accumulate unusual concentrations of Pb, soil application of chelating agents such as EDTA has been proposed to enhance the metal concentration in above-ground harvestable plant parts through enhancing the metal solubility and translocation from roots to shoots. Leaching of metals due to enhanced mobility during EDTA-assisted phytoextraction has been demonstrated as one of the potential hazards associated with this technology. Due to environmental persistence of EDTA in combination with its strong chelating abilities, the scientific community is moving away from the use of EDTA in phytoextraction and is turning to less aggressive alternative strategies such as the use of organic acids or more degradable APCAs (aminopolycarboxylic acids). We have therefore arrived at a point in phytoremediation research history in which we need to distance ourselves from EDTA as a proposed soil amendment within the context of phytoextraction. However, valuable lessons are to be learned from over a decade of EDTA-assisted phytoremediation research when considering the implementation of more degradable alternatives in assisted phytoextraction practices.

This study discusses element excesses and deficiencies in the regolith of the Riverina region, which may impact on plant, animal and human health. Top (0–10 cm depth) and bottom ( c . 60–90 cm depth) overbank sediment samples were collected near the outlets of 142 catchments and the composition of the

New geochemical data from two continental-scale soil surveys in Europe and Australia are compared. Internal project standards were exchanged to assess comparability of analytical results. The total concentration of 26 oxides/elements (Al2O3, As, Ba, CaO, Ce, Co, Cr, Fe2O3, Ga, K2O, MgO, MnO, Na2O, Nb, Ni, P2O5, Pb, Rb, SiO2, Sr, Th, TiO2, V, Y, Zn, and Zr), Loss On Ignition (LOI) and pH are demonstrated to be comparable. Additionally, directly comparable data for 14 elements in an aqua regia extraction (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo, and Pb) are provided for both continents. Median soil compositions are close, though generally Australian soils are depleted in all elements with the exception of SiO2 and Zr. This is interpreted to reflect the generally longer and, in places, more intense weathering in Australia. Calculation of the Chemical Index of Alteration (CIA) gives a median value of 72% for Australia compared to 60% for Europe. Element concentrations vary over 3 (and up to 5) orders of magnitude. Several elements (total As and Ni; aqua regia As, Co, Bi, Li, Pb) have a lower element concentration by a factor of 2–3 in the soils of northern Europe compared to southern Europe. The break in concentration coincides with the maximum extent of the last glaciation. The younger soils of northern Europe are more similar to the Australian soils than the older soils from southern Europe. In Australia, the central region with especially high SiO2 concentrations is commonly depleted in many elements. The new data define the natural background variation for two continents on both hemispheres based on real data. Judging from the experience of these two continental surveys, it can be concluded that analytical quality is the key requirement for the success of global geochemical mapping, Geological Survey of Norway, Noruega, Geoscience Australia, Australia

As part of a collaborative ecogeochemical mapping project in the European Arctic, the terrestrial mosses Hylocomium splendens (Hs) and Pleurozium schreberi (Pl) have been used to document atmospheric chemistry. The regional importance of the variability of interspecies and field duplicate samples on the element distribution in the central Barents region has been calculated. Of the 36 elements studied, 17 have significantly different concentrations in the two species. Except for K, in which all Pl samples are significantly enriched compared to Hs samples, all elements showed at least one pair that displayed the opposite behaviour to the overall trend. For the regional data set of the central Barents region, the interspecies results for (B), Bi, Cd, Co, Fe, Mn, (Na), Ni, P, Pb, S, Si, Sr, Th, U, V and Zn are directly comparable without calibration, due to lack of significant interspecies differences or a higher field duplicate uncertainty. The regional distribution of Ag, Ba, Hg, K and Sb must be interpreted cautiously in background areas, since these elements lack interspecies correlation and show significant differences between the species. Furthermore, calibration may be advisable for Al, As, Co, Cr, Cu, Fe, Mo, Tl and V for which the interspecies ratio (Pl:Hs) varies from 0.56 to 0.91, and Ca, Cd, Mg, Pb and Rb for which the ratio varies from 1.10 to 1.38. However, as a result of our study we recommend that the original data be used without undertaking calibration, but interspecies ratios need to be quantified in all multispecies datasets. Calibrated maps of the latter elements gave no striking changes in the patterns, and a new uncertainty is introduced by calibrating the original data sets. Striking differences between interspecies ratios from six comparable studies are found, especially for As, Ni, Pb and V, which underline the fact that interspecies variations depend greatly on deposition levels and living conditions for the moss.