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This study adopts a new approach describing palaeohydrology and palaeoclimates based on the interpretation of stable oxygen isotopes (δ18 O p) recorded in fossil crocodilian teeth. They represent an archive of prime interest for tracking freshwater palaeoenvironmental change, applicable to many palaeontological localities in the world: crocodilian teeth are abundant in continental basins and have been widely distributed since their diversification during the Mesozoic; the enamel phosphate is resistant to diagenesis and retains its original isotopic composition over geological timescales; and their δ18 O p mainly relies on that of the crocodilian's home waterbody (δ18 O w), which in turn reflects waterbody types, regional climate, and evaporation conditions. This study presents the first application of this theoretical interpretative model to the Shungura Formation (Lower Omo Valley, Ethiopia), a key witness of the important environmental change in eastern Africa during the Plio-Pleistocene that impacted the evolution of regional faunas, including humans. In this complex and variable environmental context, the δ18 O p of coexisting crocodilians allows for the fingerprinting of the diversity of aquatic environments they had access to at a local scale. This study sheds light on two important results: the δ18 O p of crocodilian teeth (1) indicates stable aquatic environments in the northern Turkana Depression from 2.97 to ca. 2.57 Ma but a decline in local waterbodies diversity after 2.32 Ma, suggesting increasing aridity, and (2) shows, like previous geochemical studies on palaeosols and bivalves in the area, a significant increase in δ18 O w from 2.97 to ca. 1.14 Ma, likely due to the shifting air stream convergence zones between the West African and Indian Summer Monsoons and/or reduced rainfall over the Ethiopian Highlands. [ABSTRACT FROM AUTHOR]

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, <2 mm grain size) samples, collected near the outlet of 1119 large catchments covering 5.647 million km2 (~75% of Australia). 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. The new regolith Pb isotope dataset for Australia is publicly available (Desem et al., 2023; http://dx.doi.org/10.26186/5ea8f6fd3de64). [ABSTRACT FROM AUTHOR]

With a higher demand for lithium (Li), a better understanding of its concentration and spatial distribution is important to delineate potential anomalous areas. This study uses a digital soil mapping framework to combine data from recent geochemical surveys and environmental covariates that affect soil formation to predict and map aqua-regia-extractable Li content across the 7.6×106 km2 area of Australia. Catchment outlet sediment samples (i.e. soils formed on alluvial parent material) were collected by the National Geochemical Survey of Australia at 1315 sites, with both top (0–10 cm depth) and bottom (on average ∼60 –80 cm depth) catchment outlet sediments sampled. We developed 50 bootstrap models using a cubist regression tree algorithm for each depth. The spatial prediction models were validated on an independent Northern Australia Geochemical Survey dataset, showing a good prediction with a root mean square error of 3.32 mgkg-1 (which is 44.2 % of the interquartile range) for the top depth. The model for the bottom depth has yet to be validated. The variables of importance for the models indicated that the first three Landsat 30+ Barest Earth bands (red, green, blue) and gamma radiometric dose have a strong impact on the development of regression-based Li prediction. The bootstrapped models were then used to generate digital soil Li prediction maps for both depths, which could identify and delineate areas with anomalously high Li concentrations in the regolith. The predicted maps show high Li concentration around existing mines and other potentially anomalous Li areas that have yet to be verified. The same mapping principles can potentially be applied to other elements. The Li geochemical data for calibration and validation are available from de Caritat and Cooper (2011b; 10.11636/Record.2011.020) and Main et al. (2019; 10.11636/Record.2019.002), respectively. The covariate data used for this study were sourced from the Terrestrial Ecosystem Research Network (TERN) infrastructure, which is enabled by the Australian Government's National Collaborative Research Infrastructure Strategy (NCRIS; https://esoil.io/TERNLandscapes/Public/Products/TERN/Covariates/Mosaics/90m/ , last access: 6 December 2022; TERN, 2019). The final predictive map is available at 10.5281/zenodo.7895482 (Ng et al., 2023). [ABSTRACT FROM AUTHOR]

With a higher demand for lithium (Li), a better understanding of its concentration and spatial distribution is important to delineate potential anomalous areas. This study uses a digital soil mapping framework to combine data from 15 recent geochemical surveys and environmental covariates to predict and map Li content across the 7.6 million km2 area of Australia. Soil samples were collected by the National Geochemical Survey of Australia at a total of 1315 sites, with both top (0-10 cm depth) and bottom (on average 60-80 cm depth) catchment outlet sediments sampled. We developed 50 bootstrap models using a Cubist regression tree algorithm for both depths. The spatial prediction models were validated on an independent Northern Australia Geochemical Survey dataset, showing a good prediction with a root mean square error of 20 3.82 mg kg-1 (which is 50.9 % of the inter-quartile range) for the top depth. The model for the bottom depth has yet to be validated. The variables of importance for the models indicated that the first three Landsat 30+ Barest Earth bands (blue, green, red) and gamma radiometric dose have a strong impact on Li prediction. The bootstrapped models were then used to generate digital soil Li prediction maps for both depths, which could select and delineate areas with anomalously high Li concentrations in the regolith. The map shows high Li concentration around existing mines and other potentially anomalous 25 Li areas. The same mapping principles can potentially be applied to other elements. The Li geochemical data for calibration and validation are available at: (De Caritat and Cooper, 2011a; http://dx.doi.org/10.11636/Record.2011.020) and (Main et al., 2019; http://dx.doi.org/10.11636/Record.2019.002) respectively. The covariates data used for this study was sourced from Terrestrial Ecosystem Research Network (TERN) infrastructure, which is enabled by the Australian Government's National Collaborative Research Infrastructure Strategy (NCRIS) 30 https://esoil.io/TERNLandscapes/Public/Products/TERN/Covariates/Mosaics/90m/(TERN, 2019). [ABSTRACT FROM AUTHOR]

Unpublished chemical and isotopic data taken in November 1992 from the three major Saharan aquifers, namely the Continental Intercalaire (CI), the Complexe Terminal (CT) and the phreatic aquifer (Phr), were integrated with original samples in order to chemically and isotopically characterize the largest Saharan aquifer system and investigate the processes through which groundwaters acquire their mineralization. Instead of classical Debye--Hückel extended law, a specific interaction theory (SIT) model, recently incorporated in PHREEQC 3.0, was used. Inverse modeling of hydrochemical data constrained by isotopic data was used here to quantitatively assess the influence of geochemical processes: at depth, the dissolution of salts from the geological formations during upward leakage without evaporation explains the transitions from CI to CT and to a first end member, a cluster of Phr (cluster I); near the surface, the dissolution of salts from sabkhas by rainwater explains another cluster of Phr (cluster II). In every case, secondary precipitation of calcite occurs during dissolution. All Phr waters result from the mixing of these two clusters together with calcite precipitation and ion exchange processes. These processes are quantitatively assessed by the PHREEQC model. Globally, gypsum dissolution and calcite precipitation were found to act as a carbon sink. [ABSTRACT FROM AUTHOR]

Industrial and agricultural activities can generate heavy metal pollution that can have a number of negative environmental and health impacts. This means that identifying areas with heavy metal pollution and the sources of these pollutants, especially in urban or developed areas with multiple possible sources of pollution, is an important first step in mitigating the effects of these contaminating but necessary economic activities. Here, we present the results of a heavy metal (Cu, Pb, Zn, Cd, As and Hg) soil geochemical survey and outline a new multifractal characteristic-based comparison method that allows deeper interrogation of soil geochemistry in urban or developed areas. This survey focuses on Hefei, the provincial capital of Anhui Province, China, an area that contains a number of individual towns within a large municipal area. This study focuses on the towns of Daxing and Yicheng both of which are incorporated within Hefei and are are economically focused on industry and agriculture, respectively. Here, we use a multifractal spectral technique to identify differences in the geochemistry of soils within the Daxing and Yicheng areas. The height difference between the two ends of the multifractal spectrum of the geochemical data (Δf(α)) for soils in the Daxing area decreases as follows: Pb > As > Cd > Cu > Zn > Hg, whereas Δf(α) values of the geochemical data for soils in the Yicheng town areas decreases as follows: Hg > Zn > As > Cd > Pb > Cu. These differences indicate that the soils in these areas have differing multifractal geochemical characteristics, suggesting that the differing economic activities in these areas generate distinctly different heavy metal pollutant loads (e.g. Hg dominated agricultural pollution vs. Pb dominated industrial pollution). In addition, all of the elements barring Hg have larger Δf(α) values in the Daxing area compared to the Yicheng area. These larger ranges indicate that the higher concentrations of heavy metals present in soils within the Daxing area (compared to the Yicheng area) are more likely to be related to industrial activities than agriculture. The industrial Daxing area contains significant Pb and As soil contamination, whereas Hg is the main heavy metal present in soils within the Yicheng area, indicating that differing clean-up procedures and approaches to remediating these polluted areas are needed, rather than a single approach to heavy metal pollution. The research presented here also highlights that the soils in these areas (and the source of these pollutants) need to be remedied in order to avoid further health and environmental impacts. [ABSTRACT FROM AUTHOR]

The typical Sr content of ancient dolomites is on the order of a few hundred ppm, whereas Holocene dolomites precipitating under hypersaline conditions are often more enriched in Sr with values exceeding 2000 ppm. If modern hypersaline analogues are to be useful for interpreting ancient carbonate sequences, this quantitative difference in the Sr composition of ancient vs. modern dolomite needs to be studied using a process-based approach in specific modern environments to characterize the factors leading to Sr incorporation in the dolomite precipitate and, where relevant, the subsequent removal of Sr ions during early diagenesis. With this objective, we have conducted a geochemical survey of sediment cores containing calcium magnesium carbonates precipitated in two hypersaline coastal lagoons (Lagoa Vermelha and Brejo do Espinho) located in the Região dos Lagos east of Rio de Janeiro, Brazil, together with the associated pore fluids and regional waters. We observed that sediments containing a mixture of high Mg-calcite and poorly ordered Ca-dolomite record some of the highest concentrations of Sr with an average value of ~1600 ppm, whereas the Sr content of samples comprising 100% ordered dolomite averages ~650 ppm. In contrast, our geochemical analyses of pore fluids and regional waters indicate that they are not enriched in Sr with maximum values reaching only 20 ppm. Because these lagoons are rare examples of modern dolomite precipitation in a hypersaline environment, they have been studied intensively during the past 30 years, revealing the importance of microbial processes in the precipitation of the carbonate sediments. Thus, we propose to attribute the elevated Sr concentrations in the carbonate sediments to be associated with the biotic influence on carbonate precipitation in the lagoons. In contrast, the Sr decrease in the 100% dolomite samples is attributed to changes occurring with very early diagenesis. However, as stated by Lynton S. Land (1980) in his classic paper on the isotopic and trace element geochemistry of dolomite, "If we are to invoke 'the present is the key to the past', the key must be used honestly. Problems of time and scale cannot be ignored." With this caution in mind, we evaluate the significance of geochemical results stemming from a modern analogue and their potential application to studies of ancient dolomites.Land, Lynton S. (1980). SEPM Spec. Pulb. No. 28, 87-110. [ABSTRACT FROM AUTHOR]

It is still hotly debated about the origin of the Cenozoic potassic volcanic rocks from NE China. One of the key questions concerned by scholars is to identify the source lithology of these rocks with EMI affinities: a peridotite-dominated source or a pyroxenite-dominated source? A detailed petrological and geochemical survey has been carried out to discover the nature of Wohushan potassic volcanic rocks in the Wudalianchi area. These volcanic rocks are mainly composed of tephriphonolite, phonotephrite, and basaltic trachyandesite. The geochemical analyses show that the Wohushan volcanic rocks are characterized by enrichement of LREE and some LILE e.g. Ba, K, Pb, Sr, and depletion of HREE and some HFSE e.g. Th, U, Nb, Ta, Ti without pronounced Eu and Sr troughs. They also exhibit enriched Sr–Nd–Hf isotopic compositions 87Sr/86Sr=0.7052~0.7053, εNd=-5.4~-5.1,176Hf/177Hf =0.28254~0.28257, εHf=-8.1~-7.1 and extremely unradiogenic Pb isotopic compositions 208Pb/204Pb = 36.798~36.891, 207Pb/204Pb = 15.433~15.438, 206Pb/204Pb = 16.835~16.892. According to the petrographic, mineralogical and geochemical characteristics of the Wohushan volcanic rocks, we speculate that these rocks may be associated with low-degree partial melting of a phlogopite-bearing garnet pyroxenite source in the lithosphere, where EMI components are stored. The enriched components with EMI affinities were probably originated from MTZ Mantle transition zone where carbonate-bearing sediments were isolated for a long time ~1.5 Gyr or ~2.2 Gyr. The carbonate-bearing melts derived from these sediments mentioned above ascend to the asthenosphere-lithosphere boundary, thereby forming pyroxene-dominated veins in the lithosphere. These veins have a lower solidus than peridotite, they therefore are easy to trigger partial melting during fault activities or reginal thermal anomalies. This work gives insight into the petrogeneis of the Cenozoic potassic volcanism in NE China. [ABSTRACT FROM AUTHOR]

Between September 2017 and September 2018, a seismic network consisting of 23 broadband and 22 short period station was deployed to monitor the currently exploited Los Humeros (Mexico) geothermal field. This experiment, in addition to several geophysical, geological, and geochemical surveys, has been conducted in the framework of the European H2020 project GEMex for a better understanding of the structures and behavior of the geothermal reservoir under current exploitation, and for investigating future development areas. The Los Humeros geothermal field is located in the eastern part of the Trans Mexican Volcanic Belt (TMVB) forming the northern boundary of the Serdán-Oriental basin. It is one of the largest geothermal fields in Mexico with around 40 wells operated by the Federal Electric Comission (CFE, by its Spanish acronym).In this work, we first filtered the continuous seismic records to detect local micro-seismic events occurring in the geothermal field, mostly associated to the exploitation activities. Processing includes a STA-LTA detection routine, followed by manual picking. As a result, a seismic catalog consisting of about 500 local earthquakes that are mainly clustered around injection wells is obtained. Focal depths range between 1 and 3.5 km and correspond to the known reservoir interval. We located the earthquakes using a non-linear localization technique, as a priori information for deriving a 1D velocity model. We then computed a 3D velocity model by joint inversion of each earthquake's location and velocity lateral anomalies using the derived 1D model. P- and S-wave velocities (Vp and Vs, respectively), as well as the Vp/Vs ratio models can aid in locating variations in geothermal reservoirs due to fluid composition, rock porosity and temperature. [ABSTRACT FROM AUTHOR]

Laterites developed above ultramafic protoliths are indispensable ore deposits for the supply of Ni on a global scale. In addition, Ni laterites can also host other valuable metals such as platinum-group elements (PGE), rare earth elements (REE), Sc and Co that are currently all defined as critical for western industries because of high supply risks (EC 2018). Whereas Co is occasionally mined as a co-product during Ni production from laterites, other critical elements are usually not recovered. In most cases this can be explained by in general low grades ranging from below a few hundred ppb (PGE) to a few hundred ppm (REE and Sc). On the other hand, there also exist Ni laterites with more significant potential for PGE, REE and Sc co-production, but little is still known about their deportment and (changing) mineralogy throughout the lateritic profile. However, such knowledge is considered essential for successful exploration and subsequent ore processing strategies. In the case of PGE for example, recent laboratory and field studies have demonstrated that e.g. Pt is mobile and bioavailable under certain surface conditions leading to bio-neoformation of Pt nanoclusters in the presence of microorganisms (e.g. Reith et al. 2016). Our research group investigates Ni laterites for their potential as future unconventional critical elements ore deposits since almost a decade. During this survey, innovative hydroseparation technique for heavy-mineral concentration has been applied that led to the discovery of target minerals that helped to better understand the complex geochemistry and mineralogy of Ni laterites. This contribution aims to provide a summary of geochemical and mineralogical data collected from different Ni laterite profiles from the Caribbean with focus on the deportment of PGE, REE, Sc and Co in a lateritic environment. EC (2018) Report on critical raw materials and the circular economy. https://publications.europa.eu/en/publication-detail/-/publication/d1be1b43-e18f-11e8-b690-01aa75ed71a1/language-en/format-PDF/source-80004733. Accessed on the 07/01/2019. Reith, F., Zammit, C.M., Shar, S.S., Etschmann, B., Bottrill, R., Southam, G., Ta, C., Kilburn, M., Oberthür, T.; Ball, A.S., Brugger, J. (2016) Biological role in the transformation of platinum-group-mineral grains. Nat Geosci, 9, 294–298. [ABSTRACT FROM AUTHOR]

The situation of cadmium pollution in China is generally not optimistic. Soil cadmium pollution has caused the quality of agricultural products such as rice and vegetables to decline and the quantity to decrease. It also seriously threatens the physical and mental health of local residents and affects the sustainable development of agriculture. As an important economic belt in China, the Pearl river delta accumulates a large number of environmental problems while the economy develop rapidly, among which heavy metal pollution attractes much attention because of its wide area and long duration. The upper reaches of xijiang river and beijiang river carry a large amount of cadmium elements, which are absorbed by the fine particles in sediments during the river transport process and transferred by the river dynamic transport, forming a distribution pattern of large amount of cadmium enrichment. The change of groundwater chemical environment will lead to the remigration and enrichment of cadmium, which is mainly realized by the transformation of cadmium occurrence form. The typical area with high background value of cadmium in shunde and jiangmen of the Pearl River delta is selected as the research object. Through field study, sample collection and test analysis, the basic physical and chemical properties of groundwater and soil in the unsaturated zone-saturated zone are obtained ;Multivariate statistical analysis (MSA) and factor analysis (FA-MLR) are used to determine the coupling relationship between cadmium concentration accumulation differences and morphological changes in soil and groundwater and geochemical environmental factors ;Through the laboratory soil column simulation experiment, the influence mechanism of groundwater physical and chemical conditions on the accumulation and migration of heavy metal cadmium is quantitatively analyzed ;Based on Hydrus-1D, a secondary enrichment migration and transformation model for typical areas with high background values of cadmium is established. Can not only solve the scientific questions like coupling relations between spatial distribution difference of cadmium and the morphological changes and the main environmental factors, as well as grasp the regularity of cadmium migration and enrichment in solid and liquid phase in soil and water system, and to provide scientific help for cutting off cadmium migration pathway, controlling its pollution influence range and endangering human health through food chain. [ABSTRACT FROM AUTHOR]