Papers by Patrice de Caritat
Strontium isotopes ( 87 Sr/ 86 Sr) are useful in the Earth sciences as well as in forensic, archa... more Strontium isotopes ( 87 Sr/ 86 Sr) are useful 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 87 Sr/ 86 Sr ratios on archive 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 airdried, sieved, milled then digested (hydrofluoric acid + nitric acid followed by aqua regia) to release total Sr. The Sr was then separated by chromatography and the 87 Sr/ 86 Sr ratio determined by multicollector-inductively coupled plasma mass spectrometry. Preliminary 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 87 Sr/ 86 Sr 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 ( 87 Sr/ 86 Sr < 0.7182). Where carbonate or mafic igneous rocks dominate, a low to moderate Sr isotope signature is observed. In proximity to the outcropping Proterozoic metamorphic basement of the Tennant, McArthur, Murphy and Mount Isa geological regions, conversely, radiogenic 87 Sr/ 86 Sr values (> 0.7655) are observed. A potential correlation between mineralisation and elevated 87 Sr/ 86 Sr 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.
The values and distribution patterns of the strontium (Sr) isotope ratio 87 Sr/ 86 Sr in Earth su... more The values and distribution patterns of the strontium (Sr) isotope ratio 87 Sr/ 86 Sr in Earth surface materials are of use in the geological, environmental, and social sciences. Ultimately, the 87 Sr/ 86 Sr ratios of soils and everything that lives in and on them are inherited from the rocks that are the parent materials of the soil's components. In Australia, there are few large-scale surveys of 87 Sr/ 86 Sr available, and here we report on a new, low-density dataset using 112 catchment outlet (floodplain) sediment samples covering 529 000 km 2 of inland southeastern Australia (South Australia, New South Wales, Victoria). The coarse (<2 mm) fraction of bottom sediment samples (depth ∼ 0.6-0.8 m) from the National Geochemical Survey of Australia were milled and fully digested before Sr separation by chromatography and 87 Sr/ 86 Sr determination by multicollector-inductively coupled plasma mass spectrometry. The results show a wide range of 87 Sr/ 86 Sr values from a minimum of 0.7089 to a maximum of 0.7511 (range 0.0422). The median 87 Sr/ 86 Sr (± median absolute deviation) is 0.7199 (± 0.0071), and the mean (± standard deviation) is 0.7220 (± 0.0106). The spatial patterns of the Sr isoscape observed are described and attributed to various geological sources and processes. Of note are the elevated (radiogenic) values (≥∼ 0.7270; top quartile) contributed by (1) the Palaeozoic sedimentary country rock and (mostly felsic) igneous intrusions of the Lachlan geological region to the east of the study area; (2) the Palaeoproterozoic metamorphic rocks of the central Broken Hill region; both these sources contribute radiogenic material mainly by fluvial processes; and (3) the Proterozoic to Palaeozoic rocks of the Kanmantoo, Adelaide, Gawler, and Painter geological regions to the west of the area; these sources contribute radiogenic material mainly by aeolian processes. Regions of low 87 Sr/ 86 Sr (≤∼ 0.7130; bottom quartile) belong mainly to (1) a few central Murray Basin catchments; (2) some Darling Basin catchments in the northeast; and (3) a few Eromanga geological regioninfluenced catchments in the northwest of the study area; these sources contribute unradiogenic material mainly by fluvial processes. The new spatial Sr isotope dataset for the DCD (Darling-Curnamona-Delamerian) region is publicly available
Goldschmidt2021 abstracts, 2021
We describe the information content of soil visible-near infrared (vis-NIR) reflectance spectra a... more 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 sample from across the country were compressed using 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. Visible-NIR reflectance spectra provide an integrative measure to rapidly and efficiently measure the constituents of the soil. It can replace the use of traditional soil properties to describe the soil and make geomorphological interpretations of its spatial distribution and therefore it can be used to classify soil objectively.
European Journal of Soil Science, 2011
We describe the information content of soil visible–near infrared (vis–NIR) reflectance spectra a... more 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...
Geochemistry: Exploration, Environment, Analysis
The National Geochemical Survey of Australia (NGSA) is Australia's first national-scale geoch... more The National Geochemical Survey of Australia (NGSA) is Australia's first national-scale geochemical survey. It was delivered to the public on 30 June 2011, after almost five years of stakeholder engagement, strategic planning, sample collection, preparation and analysis, quality assurance/quality control, and preliminary data analytics. The project was comprehensively documented in seven initial open-file reports and six data and map sets, followed over the next decade by more than 70 well-cited scientific publications. This review compiles the body of work and knowledge that emanated from the project to-date as an indication of the impact the NGSA had over the decade 2011–21. The geochemical fabric of Australia as never seen before has been revealed by the NGSA. This has spurred further research and stimulated the mineral exploration industry. This paper also critically looks at operational decisions taken at project time (2007–11) that were good and perhaps – with the benefit ...
What defines a geochemical map? Implications for environmental assessment.
Broken Hill Groundwater and Regolith Geochemistry (1999-2005): Datasets, Metadata and Geochemical Atlases
Information Sources
Springer eBooks, 1998
Using groundwater to vector towards mineralisation under cover: The Curnamona Province
RESULTS The results indicate that groundwater composition is affected by a number of processes: e... more RESULTS The results indicate that groundwater composition is affected by a number of processes: evaporation; evapo-transpiration; mixing; ion exchange; precipitation/dissolution; adsorption/desorption; and, oxidation/reduction. The impact of each of these major processes is teased out using 'conservative' tracers (Cl, Br), isotopes and geochemical modelling. Figure 1: Location of the Curnamona Province.
Geochemistry: Exploration, Environment, Analysis, 2019
Multi-element geochemical surveys of rocks, soils, stream/lake/floodplain sediments and regolith ... more 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.
Hydrogeochemistry and transport of weathering/oxidation products of buried mineralisation
Hydrogeochemistry applied to mineral exploration under cover in the Curnamona Province
Geochimica et Cosmochimica Acta, 2006
Chemical elements in the environment: factsheets for the geochemist and environmental scientist
... Date de parution : 03-1998 Langue : ANGLAIS Env. 396p. 20x27.5 Hardback Épuisé. Commentaire d... more ... Date de parution : 03-1998 Langue : ANGLAIS Env. 396p. 20x27.5 Hardback Épuisé. Commentaire de Chemical elements in the environment factsheets for the... : ... How low a detection limit do I need to attain if I want to analyse for an element in soils, sediments, water or plants? ...
Geochimica et Cosmochimica Acta, 2006
Comparison of the Mineralogical and Chemical Composition of 2 Shales from the Western Canada Sedimentary Basin and the United States Gulf Coast
Clays and Clay Minerals, 1997
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Papers by Patrice de Caritat