Geochemical Survey Research Articles

Geochemical mapping by unmixing alluvial sediments: An example from northern Australia

Alluvial sediments have long been used in geochemical surveys as their compositions are assumed to be representative of areas upstream. Overbank and floodplain sediments, in particular, are increasingly used for regional to continental-scale geochemical mapping. However, during downstream transport, sediments from heterogeneous source regions are carried away from their source regions and mixed. Consequently, using alluvial sedimentary geochemical data to generate continuous geochemical maps remains challenging. In this study we demonstrate a technique that numerically unmixes alluvial sediments to make a geochemical map of their upstream catchments. The unmixing approach uses a model that predicts the concentration of elements in downstream sediments, given a map of the drainage network and element concentrations in the source region. To unmix sedimentary chemistry, we seek the upstream geochemical map that, when mixed downstream, best fits geochemical observations downstream. To prevent overfitting we penalise the roughness of the geochemical model. To demonstrate our approach we apply it to alluvial samples gathered as part of the Northern Australia Geochemical Survey. This survey gathered samples collected over a ∼500,000 km2 area in northern Australia. We first validate our approach for this sample distribution with synthetic tests, which indicate that we can resolve geochemical variability at scales greater than 0.5–1° in size. We proceed to invert real geochemical data from the total digestion of fine-grained fraction of alluvial sediments. The resulting geochemical maps for two elements of potential economic interest, Cu and Nd, are evaluated in detail. We find that in both cases, our predicted downstream concentrations match well against a held-out, previously ‘unseen’ subset of the data, as well as against data from an independent geochemical survey. By performing principal component analysis on maps generated for all 46 available elements we produce a synthesis map to identify the significant geochemical domains in this part of northern Australia. This map shows strong spatial similarities to the underlying lithological map of the area. Finally, we compare the results from our approach to geochemical maps produced by interpolating alluvial geochemical data using two standard methods: kriging and inverse distance weighting. We find that, unlike the method presented here, both these methods can generate maps that are dampened relative to expected magnitude, as well as being spatially distorted. We argue that the unmixing approach is the most appropriate method for generating geochemical maps from regional-scale alluvial surveys.

Distribution and attribute analysis of soil selenium in Hebei Province, China

From 2004 to 2018, c. 73% of the land area in Hebei Province was surveyed by a 1:250 000 land quality geochemical survey of the National Geochemistry Survey of Land Quality. Based on the topsoil (0–20 cm) datasets (50 724 analysis samples) and attribute analysis of the key area with a semivariance function model, geographic detector model and random forest model, the content and spatial distribution of soil selenium (Se) in Hebei Province and the influencing factors of the distribution of Se in the Shijiazhuang–Xingtai–Handan area were obtained. The soil Se content in Hebei Province is low, ranging from 0.02 to 3.23 mg kg –1 , with an average of 0.20 mg kg –1 . The spatial distribution of soil Se was heterogeneous, and the marginal Se (0.125–0.175 mg kg –1 ) area and the sufficient Se (0.175–0.40 mg kg –1 ) area were widely distributed, but the acreage of the Se-rich (0.40–3.0 mg kg –1 ) area was very limited, accounting for only 2.43% of the total survey area. However, the Shijiazhuang–Xingtai–Handan area was a significant Se enrichment area. The spatial distribution of Se in this area was restricted by natural and socioeconomic factors. Soil organic matter was the most influential factor and showed good coordination with Se. Coal burning superimposed on natural factors promotes the spatial differentiation of soil Se to a certain extent.

Geochemical survey data cube: A useful tool for lithological classification and geochemical anomaly identification

Geochemical survey data play a critical role in geological studies, mineral exploration, and environmental applications by providing information on geological events and processes such as mineralization and pollution. A typical geochemical survey dataset contains the analysis of multiple elements. For example, the National Geochemical Mapping Project of China comprises 39 major and trace element concentrations. Multiple geochemical maps can be generated by interpolating geochemical samples into raster maps to constitute a geochemical survey data cube in which elements are sorted by their atomic numbers. A geochemical spectrum can be created using these geochemical maps in which each pixel that records geochemical characteristics. In this study, a convolutional neural network (CNN) that considers the geochemical spectrum and spatial pattern of geological objects was employed to mine a geochemical survey data cube, aiming of geological mapping and geochemical anomalies identification associated with mineralization in the eastern part of Hubei Province of China. The results showed that (1) a geochemical survey data cube which built based on various geochemical exploration data provided vital information on mineralization process and the formation of geological features; and (2) a CNN had a strong ability to recognize high-level features in the geochemical survey data cube, and it showed excellent performance in mineral exploration and related geological studies.

Multi-element association and regional geochemistry of regolith in tashan jatau area, northwestern nigeria: implications for gold exploration

Soil geochemical surveys are widely used in the early stages of gold exploration, especially in areas with poor outcrops and thick overburden. Fifty-one (51) soil samples were collected in duplicate with the aim of analyzing them geochemically and determining the gold grade through panning and weighing methods. The geochemical results were subjected to multivariate statistical treatment through Factor analysis and Pearson correlation matrix. Four factors were generated from the PCA. These are Factor 1: Cu-Sr-Nb-Ba-La-W-Pb-Zr, suggesting sulfide mineralization that is related to granitic rock while Factor 2 has Au with a low to negative correlation with Mo and Nb suggesting a second phase of intrusion-related activity which must have emplaced gold in this area. Factor 3 is made up of W-Pb suggesting a second sulfide mineralization distinct from the first. While Factor 4 gives a single element factor, Hg. Single-elementt maps were constructed to show the element dispersion in the catchment. In general gold concentrations in this study is erratic and attain a high of 0.67ppm and 0.90g/t. The study delineates the northwestern part of the catchment to be the most prolific in terms of gold potential and shows that the granitic batholiths are the most primary gold-hosting lithology.

Geochemical characteristics of soil selenium and evaluation of selenium-rich land resources in Guiyang area

Selenium concentration in soil is of great importance for the production of selenium-rich crops. In this article, we studied the geochemical characteristics of soil selenium and evaluated selenium-rich land resources in the Guiyang city area using results from a Guizhou multi-purpose regional geochemical survey. The results indicate that 1) the selenium content in topsoil in the Guiyang area ranges from 0.11 to 4.12 mg kg−1, with an average value of 0.70 mg kg−1, which is 2.4 times and 3.5 times the national and world soil background values, respectively, while the selenium content in deep soil ranges from 0.11 to 4.10 mg kg−1, with an average value of 0.42 mg kg−1, which is 1.4 and 2.1 times the national and world soil background values, respectively; in the vertical profile, the selenium content in soil decreases with the increase in soil depth. 2) The main factors affecting the distribution of selenium in soil include soil parent material, soil physical and chemical properties, and other components, such as soil type and land use, among which the soil parent material (rock) plays a decisive role. The selenium in soil mainly comes from the soil parent rock, increasing accordingly with the increase of the selenium background value of the parent rock; the physical and chemical properties of the soil and other components impose certain influences on the selenium content. Selenium presents a significant linear positive correlation with sulfur and organic carbon, while it has a negative correlation with the pH value; there is no significant difference in the selenium content in different soil types, following the distribution order of paddy soil >yellow soil> skeletal soil> lime soil> purple soil; land use has a certain effect on selenium in soil, following the distribution order of garden land > construction land > grassland > farmland > rocky hills > forest land. 3) The area of selenium-enriched soil in the study region is 11,408 km2, with 91.76% of selenium-enriched soil and 8.24% of general soil or extremely little excess-selenium soil. Therefore, the vast majority of soil in Guiyang is selenium-enriched. The city has large and abundant selenium-enriched areas, which are domestically and internationally rare and provides particularly favorable resource conditions for developing selenium-enriched efficient mountain agriculture to expedite rural revitalization.

Provenance signatures and compositional transitions based on major element chemical composition of the stream sediment from the Psunj Mt., Croatia

Stream sediment is widely used as a medium in geochemical surveys. This study examined major element chemical composition of stream sediment produced by weathering in lithologically diverse terrain. Such sediment represents mixed sediment, therefore, the aim was to interpret its provenance and model the transitions within its major element composition. The particular interest was to link major element composition, mineral composition and the sediment source rocks. In order to interpret the sediment origin principal component analysis was employed and representative samples with highest and lowest scores were analysed for mineral composition. Scores also suggested four lithology-based groups of stream sediment samples. Transitions between groups were described with linear models for compositional data. Despite the ambiguity, links between major element composition, mineral composition and provenance were established. Besides sorting out sources of mixed sediment and minerals which control the transitions, this study contributes to general understanding of the Psunj Mt. geology, while the results can be used in geochemical surveys in areas of a similar geological setting.

Multivariate Cross-Validation and Measures of Accuracy and Precision

Cross-validation and performance measures are standard components in the evaluation of a geostatistical model. These are well established in the univariate case, but measures for multivariate geostatistical modeling have not received as much attention. In the case of a single target variable, the univariate approaches remain valid, but in the fully multivariate case where a vector of variables needs to be estimated, the evaluation needs to be based on all estimates simultaneously. An extension of cross-validation and associated performance measures to the fully multivariate case is presented and discussed for the case of regionalized compositions. The method is demonstrated by validating geostatistical models for two case studies: a sample drawn from a geochemical survey data set estimated with cokriging, and an application of direct sampling multiple-point simulation.

Classification and Provenance on Geochemical Lithogenes: A Case Study on Rock–Soil–Sediment System in Wanquan Area of Zhangjiakou, North China

Geochemical lithogenes have been successfully applied as an innovative concept in the field of composition classification and source traceability of geological materials recently. This paper introduces the background of the development of geochemical genes and the construction and application of LG01 and LG03 lithogenes. Based on LG01 and LG03, the LG_CR classification and provenance are applied and verified on a weathering profile, ten gully sedimentary profiles and regional stream sediments in the Wanquan area of Zhangjiakou city, Hebei province, China. The geochemical lithology of the weathering profile shows a gradual variation from basic-like in the bottom rock to acidic-like at the upper soils compositionally with heterogeneity. The classification results on 10 sedimentary gully profiles (each with five samples) indicate that soils at the bottom of the gully system are dominated with 11 types of LG_CR materials, while the top materials are made up of 21 types, reflecting the mixing of the upstream soils. The results of stream sediments from a regional geochemical survey with a scale of 1:200,000 in this area illustrate that the classification results of LG_CR on stream sediments are basically consistent with the petrological results derived from regional geological mapping. Therefore, LG_CR can be used not only as an effective tool for classification and traceability of geological materials but also has great potential in lithological mapping in petrological-overburdened areas.

Construction, Test and Application of a Tungsten Metallogene Named MGW11: Case Studies in China

Geochemical gene is a new promising concept proposed recently in the discrimination and traceability of geological materials and is also a useful tool to recognize geochemical anomalies in mineral exploration. Based on the lithogenes of LG01 and LG03, geological materials can be classified into nine types of LG_CR compositionally. With respect to geological materials with 11 types of LG_CR, in order to eliminate the lithological influence and to further narrow the prospecting target area, a tungsten metallogene named MGW11 is proposed for geochemical tungsten exploration after the tungsten metallogene MGW. Six weathering profiles of 11 types of LG_CR developed on granitic intrusions in different areas in China are selected to test the stable properties such as heredity and inheritance of MGW11 and MGW. The results indicate that MGW11 and MGW metallogenes illustrate stable properties during rock weathering regardless of weathering degrees, although gene variations of MGW11 and MGW are also observed during extreme weathering. Based on the regional geochemistry survey data in the Lianyang area in south China, where stream sediments are mostly 11 types of LG_CR compositionally, geochemical maps of mineralization similarities of MGW11 and MGW are contoured, and the anomaly areas are determined on the mineralization similarity value of ≥40%. Comparing the tungsten deposits and anomaly areas determined on MGW11 and MGW metallogenes spatially, a total of six polymetallic W deposits recognized in the study area are all located in the anomaly areas. Therefore, mineralization similarities of MGW11 and MGW can be viewed as useful integrated indices on geochemical tungsten exploration. In areas with 11 types of LG_CR compositionally, anomaly areas determined on the MGW11 are smaller than those on the MGW, which indicates that MGW11 is more efficient than MGW in targeting W deposits during tungsten prospecting because of the elimination of the lithological influence.

Characteristics of B, Zn and Se in stream sediments of Tanzania and their agricultural applications: Based on 1:1000000 geochemical survey

Tanzania is located in eastern Africa with a predominantly agricultural ecomomy, the potential for developing and utilizing cultivated land are promising, but scientific guidance is required. B, Zn and Se are essential micronutrients for plants and human body with crucial biological functions, in particular, Se is significant for human health and considered as “the king of anti-cancer”. As these elements required by human or plants are mainly absorbed from soil directly or indirectly, therefore, it is important to understand the contents and distributions of them in the soil of cultivated land for guiding agricultural production. In this work, low-density geochemical survey at the scale of 1:1000000 was carried out in Tanzania, and the results show that the concentrations of B, Zn and Se in stream sediments are low and their distributions are heterogeneous. According to the distributions of geological units, the existing cultivated land resources can be divided into five regions in Tanzania. Compared with the national background values, the concentrations of B, Zn and Se are insufficient overall but enriched locally in these regions. In general, element concentrations in stream sediments and soil have a positive correlation because of their similar sources, which is essential in agriculture application. Based on the information provided by low-density geochemical data and maps, the Se-sufficient and Se-rich regions were delineated in Tanzania, where can be used to develop Se-rich industries. Finally, this paper believes that geochemical survey is a powerful tool for cultivated land evaluation, agriculture management and land development.©2023 China Geology Editorial Office.

Geological Mapping via Convolutional Neural Network Based on Remote Sensing and Geochemical Survey Data in Vegetation Coverage Areas

Geological mapping in vegetation coverage areas is a challenging task. In this study, convolutional neural networks (CNNs) were employed for geological mapping in a vegetation coverage area based on remote sensing images and geochemical survey data. The Gram-Schmidt fusion technology was first applied to fuse Sentinel-2A and ASTER remote sensing images to enhance the spatial resolution and enrich spectral information of remote sensing data. The fused remote sensing images were then organically integrated with geochemical survey data according to the correlations between the geochemical element contents and spectral reflectance of the objects. A case study of mapping six lithologic units in Jilinbaolige, Inner Mongolia, China was implemented using a CNN model based on the fused data. The classification map obtained an overall accuracy of 83.0%, which exhibited a better performance in contrast to random forest (RF) model. The results showed that CNNs can take full advantage of the spatial features of fused data and solve the problems of the ‘salt and pepper phenomenon’ against the shallow machine learning algorithms, and the fusion of remote sensing and geochemical data can provide rich diagnostic information for geological mapping.

Experiences from 30 years of low-density geochemical mapping at the subcontinental to continental scale in Europe

Experiences from 30 years of geochemical mapping at the (sub)continental scale in Europe using a wide range of different sample media are reviewed and discussed with a focus on the most recent GEMAS (GEochemical Mapping of Agricultural Soils) project. Comparing results from the different surveys it is possible to come to conclusions as to how geochemical surveys at the continental scale could best be designed. High analytical quality and lowest possible detection limits are key requirements. In Europe good outcomes were achieved with the <2 mm fraction of soil samples and aqua regia extraction. Focus should be on high quality of sampling and analyses and more determined parameters rather than on more samples. The sample density of 1 site/2500 km 2 provides a good overview of the processes governing geochemistry at the continental scale. Results should be extensively published by the project team to allow the dataset to be known and utilized by the wider scientific community. Thematic collection: This article is part of the Continental-scale geochemical mapping collection available at: https://www.lyellcollection.org/topic/collections/continental-scale-geochemical-mapping

The National Geochemical Survey of Australia: review and impact

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 of hindsight – not so good, with the intention of providing experiential advice for any future large-scale geochemical survey of Australia or elsewhere. We conclude that the NGSA was a low-cost, high-benefit project that delivered scientific excellence, promoted stakeholder engagement, demonstrated national leadership, and contributed to enhanced national resource wealth. Thematic collection: This article is part of the Continental-scale geochemical mapping collection available at: https://www.lyellcollection.org/topic/collections/continental-scale-geochemical-mapping

Prospecting terrain for surface geochemical exploration of oil and gas in West Siberia

ABSTRACT The relevance of this research is necessitated by the need to advance geochemical prospecting methods for raw hydrocarbon deposits. The study aimed to design new migration models by the interpretation of surface geochemical survey data. In particular, the relationship behavior needs to be identified between the hydrocarbon migration intensity and the presence of oil-bearing reservoirs within the section. To reveal quantitative relationships between the oil show and the oil-bearing capacity of the section, a substantial body of geochemical data across different fields in West Siberia was processed herein. Field-type and in-office operations were being performed by the snow survey procedure. The СН4–С6Н14 saturated hydrocarbons were employed as the major measured parameter. No direct quantitative connection was found between the intensity of surface hydrocarbon anomalies and the section productivity. Nonetheless, the two basic factors were found to affect the structure of the surface geochemical field: first, oil-bearing reservoirs present in the section and, second, fluid-resistant properties of the above-productive strata. Despite a direct quantitative relationship between the oil-bearing capacity of the section and the intensity of surface hydrocarbon anomalies being absent, the large sample made it possible to determine quantitative measures of the surface geochemical field that credibly characterize territories whose sections hold oil-bearing horizons.

STUDI SPEKTROSKOPI FTIR UNTUK KARAKTERISASI KIMIA FISIK FLUIDA MATA AIR PANAS DI DESA TEMPANG KABUPATEN MINAHASA

The increasing population of the world's population results in the need for energy to continue to increase, therefore the Indonesian government develops energy outside of fossil fuels, one of which is geothermal. Geothermal is one of the alternative energy source that is relatively new and renewable and can be renewed because production waste in the form of water is re-injected and produces a recycle process that allows sustainability. Geological surveys, geochemical surveys, and geophysical surveys are characterizations that need to be carried out in describing geothermal potential. The purpose of this study was to determine the type of fluid and molecular functional groups of hot springs in Tempang Village, Minahasa Regency. With the geochemical method using a spectrophotometer and FTIR (Fourier Transform Infra Red) spectroscopy, it is known that the type of fluid in the hot springs in Tempang Village is Bicarbonate (HCO3) type with a content of 69 mg/L and the molecular functional group is O-H and C=O.

Active degassing of crustal CO2 in areas of tectonic collision: A case study from the Pollino and Calabria sectors (Southern Italy)

Carbon dioxide (CO2) is released from the Earth’s interior into the atmosphere through both volcanic and non-volcanic sources in a variety of tectonic settings. A quantitative understanding of CO2 outgassing fluxes in different geological settings is thus critical for decoding the link between the global carbon budget and different natural processes (e.g., volcanic eruption and earthquake nucleation) and the effects on the climate evolution over geological time. It has recently been proposed that CO2 degassing from non-volcanic areas is a major component of the natural CO2 emission budget, but available data are still sparse and incomplete. Here, we report the results of a geochemical survey aimed at quantifying CO2 emissions through cold and thermal springs of the tectonically active Pollino Massif and Calabrian arc (Southern Italy). The chemical ad isotopic (He and C) composition of fifty-five dissolved gas samples allows to identify two different domains: 1) a shallow system dominated by gas components of atmospheric signature (helium, hereafter He) and biogenic origin (C), and 2) a deeper system in which crustal/deep fluids (CO2 and He) are dominant. The measured He isotope ratios range from 0.03 to 1.1 Ra (where Ra is the He isotopic ratio in the atmosphere) revealing a variable atmospheric contamination. Furthermore, the He isotopic data indicate the presence of traces of mantle He contributions (2%–3%) in the thermal groundwater. The prevailing low R/Ra values reflect the addition of crustal radiogenic 4He during groundwater circulation. Using helium and carbon isotope data, we explore the possible sources of fluids and the secondary processes (dissolution/precipitation) that act to modify the chemistry of pristine volatiles. For the thermal springs, we estimate a deep C output of 2.3 x 107 to 6.1 x 108 mol year−1. These values correspond to deep CO2 fluxes per square km comparable with those estimated in several active and inactive volcanic areas and in continental regions affected by metamorphic CO2 degassing (e.g., the southern margin of the Tibetan Plateau).

Study of dilution processes of sulfidic aquifer hosted by the Fiume-Vento karstic complex, Frasassi (Central Italy)

Sulfuric acid caves are widespread worldwide. In Central Italy, the Fiume-Vento karstic complex represents the most important active hypogenic cave system hosting several interconnected lakes where groundwater moves towards sulfidic springs emerging along the Sentino Stream. Stratification and dilution phenomena between freshwater and sulfidic water occur in many underground lakes, even if they remain still open if these processes are driven by stream-aquifer interaction or dripping water. The speleological knowledge coupled with geochemical surveys can help study groundwater circulation in the karst system’s inner and outer portions. The geochemical analyses on water samples taken along the Sentino Stream, inside the caves (dripping and lakes water) and in sulfidic springs allow establishing the origin of the dilution water in the dripping water. However, stream-aquifer interactions cannot be excluded during flood events. Using the tracer masse balance method (chloride and sodium ions), the discharge of the sulfidic springs ranges between 65 and 11 L/s. The results presented in this study may help understand groundwater circulation and dilution phenomena in other karst systems characterised by sulfuric acid speleogenesis type.

Geological Mapping Using Direct Sampling and a Convolutional Neural Network Based on Geochemical Survey Data

Geological Mapping Using Direct Sampling and a Convolutional Neural Network Based on Geochemical Survey Data

Electrical resistivity structure of Danau Ranau geothermal prospect area based on integrated 3-D Inversion of impedance tensor and tipper vector

Subsurface electrical resistivity distribution needs to be revealed to explore the geothermal potential in The Danau Ranau prospect area, as the components in geothermal systems could be easily characterized by their resistivity contrasts. The magnetotelluric method is a geophysical method commonly used to perform this task. This paper performs a three-dimensional inversion based on the complete component of magnetotelluric transfer functions, including impedance tensor and tipper vector. Prior dimensionality analysis using phase tensor revealed that the MT data contains a high dimensionality distortion and shows significant horizontal geoelectrical variations. The analysis suggests using the MT full components in the inversion process to effectively recover all the geoelectrical features in such a geologically complex area. The three-dimensional inversion was then carried out after taking control of the model mesh dimension and the regularization parameter. The 3-D resistivity model showed an overburden layer with varying resistivity in the shallow depth. In the subsequent layer, a conductive anomaly representing impermeable cap rock is distributed from the center to the northern and western parts of the study area, bordered by faults and manifestations. The reservoir zone is located under the center of Mount Seminung at an approximate depth of 1500 m. The heat source is expected to be the residual eruption magma of the volcano, which sits far under the reservoir zone and is unreachable by the MT signal. All the findings agree with the existing geological and geochemical survey data and can explain the hydrothermal activities in the Danau Ranau geothermal prospect area.

A strontium isoscape of inland southeastern Australia

Abstract. The values and distribution patterns of the strontium (Sr) isotope ratio 87Sr/86Sr in Earth surface materials are of use in the geological, environmental, and social sciences. Ultimately, the 87Sr/86Sr 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 87Sr/86Sr available, and here we report on a new, low-density dataset using 112 catchment outlet (floodplain) sediment samples covering 529 000 km2 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 87Sr/86Sr determination by multicollector-inductively coupled plasma mass spectrometry. The results show a wide range of 87Sr/86Sr values from a minimum of 0.7089 to a maximum of 0.7511 (range 0.0422). The median 87Sr/86Sr (± 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 87Sr/86Sr (≤∼ 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 region-influenced 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 (de Caritat et al., 2022; https://dx.doi.org/10.26186/146397)​​​​​​​.