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The 16th century AD St. Barbara's Church in Paternò, a town located at the SW foot of Mt. Etna volcano (Sicily, Italy), has since 2009 showed evident signs of structural instability and collapse. This is causing great concern among the local population and poses a growing hazard to the attendees to the masses. After precautionary closure of the church, we carried out geological, seismic, geophysical and geochemical surveys in order to shed light on the possible causes of the phenomenon. From the results of all surveys above, the presence of a hidden fault was hypothesized. The fault would prove to cross the west side of the church, parallel to its front portal, and continue both to the north and to the south of the edifice. It is part of a more complex system of faults that crosses the whole town of Paternò and is likely a result of the complex dynamics of Mt. Etna. This fault seems to also be a pathway for the upward flow of saline hydrothermal fluids, similar in composition to those emitted in nearby areas and whose corrosive action possibly contributed to the weakening of the rocks beneath the church. Temporal monitoring of several hydrological parameters (water temperature, water level and CO2 content) in some sites in and around the church allowed a better understanding both of the fault dynamics and of the extent of hydrothermal influence in the studied area. [ABSTRACT FROM AUTHOR]

Yingfeng Area is located within Shiquan Xunyang National-level Gold Deposit Exploration Area in Shaanxi Province, characterized by favorable metallogenic geological conditions and promising prospecting potential. A 1:25 000 soil geochemical survey was conducted, analyzing the variation coefficients, correlations, and cluster analysis of 10 elements. The results indicate that the distribution of Au is uneven, with a high degree of dispersion, identifying it as the primary ore-forming element. By studying Au anomalies and comprehensive anomalies in conjunction with metallogenic geological conditions and mineralization characteristics, 5 gold alteration zones were delineated. Verification through geochemical profiles, trench exploration, and drilling projects resulted in the delineation of 17 gold ore (mineralized) bodies, further confirming the area's promising prospecting potential. [ABSTRACT FROM AUTHOR]

Potential zones of gold mineralization in Mwanza, Malawi, were mapped by employing an integrated analysis of satellite imagery and aeromagnetic data. PRISMA hyperspectral imagery satellite was used to map hydrothermal alteration minerals by employing linear spectral unmixing (LSU), spectral angle mapper (SAM), and spectral information divergence (SID) mapping techniques. Aeromagnetic data was used to map the structures using the Centre for Exploration Target (CET grid and porphyry analysis) and depth estimation using spectral analysis. The evaluation of LSU, SID, and SAM effectiveness showed an overall accuracy (OA) of 86.288% and a Kappa coefficient (ҡ) of 0.825, an OA of 82.042% and ҡ of 0.770, and an OA of 80.675% and ҡ of 0.753, respectively. The mineral maps revealed that the alteration zones mainly consist of kaolinite, indicating the potassic and argillic alteration types. About six zones that showed potential for mineralization were identified from the integrated analysis. The structures in the area were found to trend NE-SW dominantly, and the depth range to basement complex rocks, which host potential mineralization veins, was found to be 90.33–1416.40 m. Limited chemical data of quartz veins shows an average of 0.2 ppm gold anomalies from the identified zones. The suspected gold-bearing quartz veins have been observed to be in association with the gneisses and migmatites that make up the basement complex rocks in the area. A comprehensive study encompassing geological and geochemical surveys and analyses is required to ascertain its complete gold potential. [ABSTRACT FROM AUTHOR]

The Parecis Basin, one of Brazil's most extensive intracratonic basins, holds significant potential for hydrocarbon exploration. Despite its vast size, Parecis has yet to be extensively explored, with only five wildcat wells drilled. So far, no commercial discoveries have been announced. Regional studies have suggested Paleozoic sedimentation, while recent analyses have revealed a Neoproterozoic infill. Its tectonic model is still a matter of debate, and to date, no detailed structural map for the whole basin has been published. The present work proposes a new detailed structural map of the Parecis Basin based on a four-step interpretation workflow integrating seismic and gravimetric data. The first step includes converting the public 2D seismic lines to the depth domain. The second step is estimating the residual Bouguer anomaly, where the computed residual anomalies should relate to the basin's tectonic features. The third step comprises the 2D forward modeling of the gravimetric anomalies using the 2D seismic interpretation as a constraint. The final step compiled all the interpreted features into our new structural map. This map reveals the top of the basement, forming a complex framework of horsts and grabens. Normal faults define the main structural style in the basin. Further, we could recognize thick, high-density bodies embedded in the crystalline basement. These bodies consist of Orosian–Calimian (1.8–1.6 Ga) mafic and ultramafic rocks, which may be a potential source for hydrogen exploration in the basin. Subsequent geophysical and geochemical surveys will assess the hydrogen potential in the area. [ABSTRACT FROM AUTHOR]

Geochemical mapping is the base of knowledge needed to determine the critical contents of potential toxic elements and the potentially hazardous regions on the planet. This work presents maps of baseline values of chemical elements in the soils of Sal Island (Cape Verde) and the assessment of their ecological and human health risks. According to the results, Ba, Co, Ni, and V baseline values are above the international guidelines for agricultural and residential proposed uses. Arsenic in the soil overlying the Ancient Eruptive Complex shows a high potential ecological risk factor. It is not clear if high As contents in soils have a geogenic or anthropogenic source. Hazard indexes (HI) were calculated for children and adults. For children, HI is higher than 1 for Co, Cr, and Mn, indicating potential non-carcinogenic risk. These elements are present in high content in soils covering Quaternary sediments, the Monte Grande-Pedra Lume Formation, and the Ancient Eruptive Complex, inducing belief in a geogenic source. For the other elements and for adults, there is no potential non-carcinogenic risk. Cancer risk (CR) was calculated for As, Cd, Cr, and Ni exposures for adults and children, and the results are mainly lower than the carcinogenic target risk value, indicating no cancer risk. Only in a few soil samples are CR results slightly higher than the carcinogenic target risk of 1 × 10−4 2 × 10−6 for adults exposed to Cr by inhalation. It is important to emphasize that these results of the health risk associated with exposure are likely to overestimate the bioavailable fractions of the elements in the soil once it is used as aqua regia instead of physiological fluids to digest the soil. However, since measured concentrations of potential toxic elements in soil reveal that they can be harmful to both the environment and human health, regional activities such as agriculture or water exploitation must be controlled by competent authorities. These conclusions highlight the insights and the applicability of soil geochemistry surveys for future policy progress, which are particularly relevant in developing countries like the Cape Verde archipelago. [ABSTRACT FROM AUTHOR]

Effective geochemical anomaly identification is crucial in mineral exploration. Recent trends have favored deep learning (DL) to decipher geochemical survey data. Yet purely data-driven DL algorithms often lack logical explanations and geological consistency, occasionally clashing with known geological insights and complicating model interpretation. A deep understanding of the geological processes forming the target mineral deposit is vital for accurate anomaly detection. Here, we introduce an adversarial autoencoder (AAE) network that integrates prior geological knowledge to identify geochemical anomalies linked to tungsten mineralization in southern Jiangxi Province, China. Considering the geochemical patterns linked to tungsten mineralization, Yanshanian granites and faults were strategically chosen as ore-controlling factors. The methodology employed multifractal singularity analysis to quantitatively measure the correlations between these ore-controlling factors and known tungsten deposits, aiming to establish an ore-forming regularity. This regularity serves as a priori distribution to control the encoder network's latent vector, refining the model's output. A comparison of detected geochemical anomalies under different constraints (AAE, Granite_AAE, Fault_AAE, and Fault_Granite_AAE) revealed that AAE models incorporating prior geological information consistently outperformed unconstrained models in terms of anomaly detection. Integrating geological expertise with DL, our study overcomes the challenges of models relying purely on data or theory, offering a promising approach to geochemical exploration. [ABSTRACT FROM AUTHOR]

Effective management of surface emissions from abandoned gob methane (AGM) is crucial for mitigating greenhouse gas emissions and ensuring public safety. An important geochemical characteristic of near-surface AGM migration is the potential presence of abnormal component concentrations in near-surface soil gas over abandoned coal gobs. To investigate this phenomenon, a surface geochemical survey was conducted based on four survey lines in the Dongyi and Dongsan abandoned gob groups in the Xinghua Coal Mine, Jixi Basin, in China. The gas chromatography technique was used to analyze the concentrations of methane, carbon dioxide, ethane, propane, and butane in the collected 43 soil gas samples. The results revealed a significant anomaly of soil gas concentrations, particularly methane and carbon dioxide anomalies, in the near-surface soil over abandoned gobs. The background concentration for methane was determined to be 7.49 ppm, with an anomalous threshold set at 10 ppm based on a statistical analysis and an iterative method. This threshold could be confirmed by examining the coupling and decoupling relationship between methane, carbon dioxide, and C2–3 as well. A spatial correlation between regions exhibiting anomalous methane and carbon dioxide concentrations and the positions of gob areas, abandoned surface wells, and faults was observed. Abandoned and sealed coalbed methane surface wells and faults near gas-rich gob areas have the potential to act as conduits for AGM leakage to the surface. Furthermore, concentrations of methane, carbon dioxide, and C2–3 in soil gas over abandoned coal gobs were significantly higher compared to areas unaffected by mining activities. This suggests that elevated concentrations of methane, carbon dioxide, and C2–3 in soil gas may originate from underground AGM. [ABSTRACT FROM AUTHOR]

Silver (Ag) isotopes can be useful geochemical and environmental tracers, but their applications are hindered by the challenges of Ag isotope analyses, especially for samples with extremely high matrix element and low Ag contents (<100 ng g−1). In this study, we developed a new protocol by using four-step chromatography for high-precision Ag isotope measurements for silicate samples. The δ109Ag values were measured using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) using dry plasma. The sensitivity was 100 V ppm−1, reducing the consumption of Ag to 5 ng. Moreover, instrumental mass bias was corrected using the Pd-doping and standard-sample bracketing methods. The robustness of this method was assessed by analyzing the NIST SRM978a doped with different matrix element ratios. The average δ109AgSRM978a value of synthetic solutions (0.00 ± 0.05‰; 2SD, n ≥ 4) is consistent with the recommended values (0). The external precision is 0.05‰ (2SD) based on the measurement of two in-house standards. We further analyzed seven USGS rocks, including basalt (BCR-2 and BIR-1), andesite (AGV-2), granite (GSP-2 and G-2), rhyolite (RGM-2), and ferromanganese crusts (NOD-P-1). Their δ109AgSRM978a values vary from −0.24 ± 0.05‰ to 0.20 ± 0.05‰, suggesting that Ag isotopes can be significantly fractionated in silicate rocks. This study provides a great opportunity for the future application of Ag isotopes in geochemical and environmental studies. [ABSTRACT FROM AUTHOR]

The relative contributions of asthenospheric mantle, lithospheric mantle, and continental crust in the genesis of the Siberian Traps Large Igneous Province (ST-LIP) remain poorly constrained. Most models invoke partial melting of asthenospheric mantle within a mantle plume with an inventory of recycled crustal material, with or without melting of subcontinental lithospheric mantle, and crustal contamination during ascend through the continental lithosphere. A greater understanding of this topic is of fundamental importance because the ST-LIP basalts are associated with the large Permian-Triassic extinction and the world's largest magmatic Ni-Cu-platinum group element sulfide resources (Ni-Cu-PGE), the Norilsk-Talnakh mining camp. The ∼250 ± 2 Ma Siberian Traps at Norilsk contain a classic sequence of basaltic rocks that provide a spatial and stratigraphic context for changing chemistry of the eruptive products. We present a detailed geochemical and Sr-Nd-Hf-Mo isotopic investigation of ST-LIP volcanic rocks and associated sedimentary rocks, including coal and anhydrite, from the Norilsk area. The 98Mo/95Mo isotope ratios (reported as δ98Mo ratio relative to NIST SRM 3134) vary significantly from −0.62 to 0.07 ‰ for the older basalt formations and −0.41 to 0.03 ‰ for the younger basalt formations. The range of δ98Mo and its correlation with the other geochemical tracers cannot be explained by post-magmatic alteration, magmatic differentiation, or sulfide fractionation as Mo behaves as a lithophile element under these magmatic conditions. We suggest that the δ98Mo range can be explained by interaction of the plume with subcontinental lithospheric mantle modified by subduction processes. This is particularly prominent in the earlier Ivakinsky to Gudchikhinsky formations where light δ98Mo values coupled with low Mo/Ce can be explained by contributions from a dehydrated eclogitic component, whereas more rare heavy δ98Mo values and high Mo/Ce likely require contributions from a fluid metasomatized mantle source. Later magmas of the Nadezhdinsky formation show clear evidence of crustal contamination in their combined Mo-Sr-Nd-Hf isotope and trace element systematics, while the later more voluminous Morongovsky type magmas are shallower, large degree melts with limited crustal interaction. Our data shows the usefulness of Mo isotopes in deciphering magma sources of large igneous provinces eruptions. [ABSTRACT FROM AUTHOR]

A notable decrease of groundwater Na/K ratios was observed several months before the 2018 Hokkaido Eastern Iburi earthquake (M6.7) at a site approximately 20 km west of the earthquake's epicenter. To investigate the cause of the decreased Na/K ratios, we analyzed groundwater samples (commercially bottled drinking water) to assess the contribution of deep-derived fluids using Li and Sr isotopic ratios, which are reliable indicators of deep fluid contributions. No pronounced changes in the 7Li/6Li and 87Sr/86Sr ratios were observed; thus, the pre-earthquake decrease of groundwater Na/K ratios did not result from the input of deep-derived fluids. The pre-earthquake decrease in the Na/K ratio observed in this study may instead be related to CO2 influx into the aquifer. The CO2 may have leaked from carbon dioxide capture and storage (CCS), because CCS was in operation near the epicenter of the 2018 Hokkaido Eastern Iburi earthquake. Decreases of the Na/K ratios and increases of the CO2 concentrations in groundwater have been reported before other large earthquakes; thus, CO2 influx into groundwater may be a common phenomenon preceding earthquakes. [ABSTRACT FROM AUTHOR]

Advances in multi‐collector inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS) have led to the widespread use of iron (Fe) isotopes to elucidate the (bio)geochemical history of a range of environments. To generate Fe isotope ratio measurements, standard‐sample bracketing (SSB) is commonly used to correct for instrumental mass bias inherent to MC‐ICP‐MS. However, SSB is only accurate when sample and isotope standard Fe concentrations match, in addition to the bulk solution matrix. When the Fe concentrations differ, Fe isotope ratio measurement results may be inaccurate, a phenomenon known as the "self‐induced matrix effect." This study systematically characterised the self‐induced matrix effect for dry plasma Fe isotope ratio measurements on three MC‐ICP‐MS instruments and three introduction systems. Our extensive dataset indicates that: (1) the degree of mass bias is consistent regardless of MC‐ICP‐MS front‐end design, (2) the degree of mass bias becomes less reproducible as the concentration difference between the sample and bracketing standard increases, and (3) this applies to both pure Fe solutions and solutions from geological materials. This study reinforces the requirement to match bracketing standard and sample concentrations within 10% and provides a correction method for that fall beyond the recommended concentration range to subsequently allow for proper concentration matching during SSB. [ABSTRACT FROM AUTHOR]

Geothermal fields emit remarkable amounts of mercury (Hg) to the environment. To address the source, fate and geochemical cycling of Hg in geothermal fields, we investigated Hg concentrations and isotopic compositions of hot spring water and fumarole gases from Rehai and Dagejia in SW‐China. Elevated Hg concentrations in fumarole gases (10.0–167 ng m−3) and hot spring water (3.44–84.5 ng L−1) were observed, suggesting that both geothermal fields are of environmental concern. The variation in Δ199Hg (−0.06 to 0.23‰) and Δ200Hg (−0.09 to 0.19‰) in hot spring water supports Hg likely originating from endogenous volcanic degassing and/or rainwater. Negative and nearly zero Δ199Hg in fumarole gases (−0.32 to 0.03‰) supports volcanic degassing and background atmosphere origin. The ranges of δ202Hg in fumarole gases (−0.74 to 0.59‰) and hot spring water (−1.29 to 0.52‰) could reflect limited fluids boiling in geothermal fields. This study, thus, fills an important knowledge gap regarding Hg global cycling. Plain Language Summary: A large amount of mercury (Hg) is emitted into the atmosphere through geothermal activities. A knowledge gap exists regarding the source, fate and geochemical cycling of Hg in geothermal fields. Here, we studied Hg concentrations and isotopic compositions in hot spring water and fumarole gases from two large geothermal fields in SW‐China. Our results support that the two fields received Hg from endogenous volcanic degassing and rainwater. Deep magma chambers acted as heat sources, triggering fluid circulation in geothermal areas and entraining Hg from rainwater into geothermal systems. Key Points: Rehai and Dagejia geothermal fields are likely of local environmental concern regarding Hg emissionMercury isotopic ratios evidence that geothermal fields could receive Hg from endogenous volcanic degassing and rainwaterGeothermal fluid boiling is not common in geothermal fields in SW‐China [ABSTRACT FROM AUTHOR]

Tonian (ca. 1000–720 Ma) marine environments are hypothesised to have experienced major redox changes coinciding with the evolution and diversification of multicellular eukaryotes. In particular, the earliest Tonian stratigraphic record features the colonisation of benthic habitats by multicellular macroscopic algae, which would have been powerful ecosystem engineers that contributed to the oxygenation of the oceans and the reorganisation of biogeochemical cycles. However, the paleoredox context of this expansion of macroalgal habitats in Tonian nearshore marine environments remains uncertain due to limited well‐preserved fossils and stratigraphy. As such, the interdependent relationship between early complex life and ocean redox state is unclear. An assemblage of macrofossils including the chlorophyte macroalga Archaeochaeta guncho was recently discovered in the lower Mackenzie Mountains Supergroup in Yukon (Canada), which archives marine sedimentation from ca. 950–775 Ma, permitting investigation into environmental evolution coincident with eukaryotic ecosystem evolution and expansion. Here we present multi‐proxy geochemical data from the lower Mackenzie Mountains Supergroup to constrain the paleoredox environment within which these large benthic macroalgae thrived. Two transects show evidence for basin‐wide anoxic (ferruginous) oceanic conditions (i.e., high FeHR/FeT, low Fepy/FeHR), with muted redox‐sensitive trace metal enrichments and possible seasonal variability. However, the weathering of sulfide minerals in the studied samples may obscure geochemical signatures of euxinic conditions. These results suggest that macroalgae colonized shallow environments in an ocean that remained dominantly anoxic with limited evidence for oxygenation until ca. 850 Ma. Collectively, these geochemical results provide novel insights into the environmental conditions surrounding the evolution and expansion of benthic macroalgae and the eventual dominance of oxygenated oceanic conditions required for the later emergence of animals. [ABSTRACT FROM AUTHOR]

Since 2013, 34 surveys of surface and ground waters within and outside the former Hg-mine of Abbadia San Salvatore (Italy), which is currently under remediation, were performed for determining Hg, As, Sb, and main and minor solutes. The water quality is rather poor since most waters show relatively high Hg concentrations (up to 695 µg/L). Differently, As and Sb only overcome the Italian law thresholds in a few sites. A high geochemical variability was observed for most groundwaters without any clear relationship between wet and dry periods. The main source of chalcophile elements is likely related to: (i) the interaction between meteoric waters and soils contaminated by the previous production of mercury; or (ii) the interaction between meteoric waters and the anthropic filling material of a former paleo-valley near the furnaces edifices. While the remediation is expected to be concluded in 2025, the aquifer contamination still remains a problem. Our investigation, including geochemical/hydrogeological modeling, is prodromal to future activities aimed at reducing the Hg content. Currently, the construction of a hydraulic barrier is apparently the most suitable solution to minimize the interaction processes between water–rock and man-made material, which are responsible for the 10-year concentration variability. [ABSTRACT FROM AUTHOR]

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Selenium (Se) is a micronutrient that has attracted significant attention, because the threshold for human health is low. During soil surveys in China, large areas of low-Se soil were found, and this condition may increase the probability of people suffering from Se deficiency. A multi-purpose regional geochemical survey conducted in the Lou Shao basin of Hunan Province found abundant Se-rich soils in Lianyuan City. However, as the primary grain-producing area in Hunan Province, the key factors affecting the spatial distribution of soil Se in the cultivated land of Lianyuan City remain to be elucidated. Therefore, based on the data of 5516 topsoil samples (0–20 cm) of cultivated land in Lianyuan City, we used geostatistics, correlation analysis, and a Geodetector to explore the effects of geological conditions (strata), soil types, soil properties, and topography on the distribution of Se in soil. The results showed that (1) in comparison to cultivated land in the Chinese mainland, Japan, Belgium, and Sweden, the cultivated land in Lianyuan City exhibits higher Se contents, with Se-sufficient and Se-rich areas accounting for 9.74% and 88.96% of the total area, respectively; (2) the distribution of high-Se soil was consistent with that in the Longtan Formation, Dalong Formation, and Daye Formation; (3) organic matter (OM) showed a positive correlation with Se, while both the elevation and slope were negatively correlated with Se; (4) stratum had the most significant effect on the spatial variation in soil Se, followed by OM. Lianyuan City is a typical Se-rich area, and the high level of Se in soil reduces the risk of local residents suffering with diseases caused by Se deficiency. The synergistic effect of stratum and OM is the key factor influencing Se enrichment in soils. Moreover, low-lying flat areas are more conducive to the accumulation of Se. This study will help farmers to identify suitable Se-rich cultivation areas in order to increase the Se content in crops, thereby providing a valuable basis for improvements in human health and the optimization of agricultural strategies. [ABSTRACT FROM AUTHOR]

Lithological mapping plays a vital role in acquiring a comprehensive understanding of subsurface rocks and geological structures. Traditional lithological mapping relies heavily on manual field surveys, with the accuracy of the mapping greatly constrained by the expertise of mappers, and thus this process is commonly slow and costly. In the present study, the graph convolutional network (GCN) method was proposed for efficient and automatic lithological mapping, using various geological survey data (e.g. geochemical and geophysical data). The GCN is not limited by the spatial distribution of sampling data, and hence it can be directly applied to the integrated resampling data that do not adhere to the regular spatial distribution patterns of Euclidean space. To evaluate the potential application of the GCN method in lithological classification and mapping, a case study was conducted in the Maqin region (China). Geochemical and geophysical data were utilized as the basis for lithological classification, as they can provide valuable information on geochemical compositions and physical properties of geological bodies, respectively. The study process was primarily divided into three parts. First, basic pre-processing was conducted on the geochemical data and the geophysical data, including centred log-ratio transformation and resampling. Subsequently, the resampled points were divided into training and testing sets in the proportion of 5.5:1. In the training set, 20% of the points are randomly selected as the validation set. Ultimately, using each resampled point as a node and the integrated geochemical and geophysical data as features, a GCN model and an undirected graph were constructed based on an adjacency distance of 1 km. The graph was employed by the constructed GCN model for lithological classification. The results reveal that the majority of lithological units can be accurately classified with an overall accuracy of 86%, indicating that the GCN model exhibits good applicability in lithological classification. [ABSTRACT FROM AUTHOR]

Regional geochemical surveys generate large amounts of data that can be used for a number of purposes such as to guide mineral exploration. Modern surveys are typically designed to permit quantification of data uncertainty through data quality metrics by using quality assurance and quality control (QA/QC) methods. However, these metrics, such as data accuracy and precision, are obtained through the data generation phase. Consequently, it is unclear how residual uncertainty in geochemical data can be minimized (denoised). This is a limitation to propagating uncertainty through downstream activities, particularly through complex models, which can result from the usage of artificial intelligence-based methods. This study aims to develop a deep learning-based method to examine and quantify uncertainty contained in geochemical survey data. Specifically, we demonstrate that: (1) autoencoders can reduce or modulate geochemical data uncertainty; (2) a reduction in uncertainty is observable in the spatial domain as a decrease of the nugget; and (3) a clear data reconstruction regime of the autoencoder can be identified that is strongly associated with data denoising, as opposed to the removal of useful events in data, such as meaningful geochemical anomalies. Our method to post-hoc denoising of geochemical data using deep learning is simple, clear and consistent, with the amount of denoising guided by highly interpretable metrics and existing frameworks of scientific data quality. Consequently, variably denoised data, as well as the original data, could be fed into a single downstream workflow (e.g., mapping, general data analysis or mineral prospectivity mapping), and the differences in the outcome can be subsequently quantified to propagate data uncertainty. [ABSTRACT FROM AUTHOR]

Fifteen Geological Survey of Japan (GSJ) geochemical reference materials were analyzed to determine the contents of three halogens (Cl, Br, and I) by using instrumental neutron activation analysis (INAA) and/or radiochemical NAA (RNAA). Two reference materials (JCp-1 and JSO-1) were analyzed using both INAA and RNAA. Although there were discrepancies in Cl and Br for JCp-1 between the INAA and RNAA data, probably due to sample heterogeneity, the INAA and RNAA data for JSO-1 were consistent with each other, within less than 7%, indicating that our RNAA data are reliable. With the repeated analyses of JR-3, the external repeatability of the data obtained using RNAA was evaluated to be 18% for Cl, 11% for Br, and 19% for I. Our RNAA data are in agreement with literature values using NAA for the three halogens, as well as those using isotope dilution mass spectrometry and ion chromatography for Cl. Systematically lower values when using neutron irradiation noble gas mass spectrometry (NI-NGMS) and inductively coupled plasma mass spectrometry (ICP-MS) with pyrohydrolysis can be observed, implying that there are losses for noble gas nuclides produced through the beta-decay of the neutron capture halogen nuclides in NI-NGMS and the non-quantitative recovery of Br and I during procedures in ICP-MS, respectively. [ABSTRACT FROM AUTHOR]

Geothermal resources, as abundant renewable and clean natural resources on Earth, have been utilized for geothermal power generation in 29 countries. Guangdong Province, as one of the most developed, economically vibrant, and attractive investment regions in China, has experienced rapid economic growth. However, further development is constrained by resource limitations and severe ecological environmental pressures. The issue of energy consumption and economic growth imbalance needs to be urgently addressed. Geothermal energy, as a clean and stable form of energy, can reduce reliance on fossil fuels, decrease dependence on imported energy, and enhance national energy security. In this study, geological survey, geophysical survey, geochemical survey, remote sensing detection and drilling were carried out in the Shiba–Huangshadong area of Huizhou, and by analyzing the data on geothermal energy reserves in the study area, the available geothermal energy and its potentials in the study area were identified and its impact on the current energy consumption in Huizhou City was assessed, to validate the feasibility of the detailed application of the geothermal energy in the Greater Bay Area, which will enable the energy structure of Huizhou City optimize the energy structure. [ABSTRACT FROM AUTHOR]

The role of S during high-grade metamorphism is a topic that has not garnered much interest in the literature until recently. In this review, the role of S as an active component in high grade hypersaline fluids is reviewed per a series of regional studies involving orthopyroxene-bearing granulite-facies granitoids. These include the Shevaroy Block and Nilgiri Block, southern India; the Bamble Sector, southwest Norway; the Val Strona traverse of the Ivrea-Verbano Zone, northern Italy; and the Lewisian Complex, northwest Scotland. In each these terranes, S-bearing, high-grade, low H2O activity fluids are conjectured to have been present during granulite-facies metamorphism and to have contributed to the dehydration of the rock, the oxidation state of the rock, and trace element mobility, leaving behind pyrite and/or pyrrhotite as traces of its presence. The various mineral equilibria reactions between the various oxidation states of S in these fluids and the oxide and silicate minerals encountered by the fluid are explored and a coherent framework of interdependent chemical reactions are developed, which describe both oxidation of the rock and the formation of pyrite and pyrrhotite during both peak- and post-peak metamorphism. [ABSTRACT FROM AUTHOR]

Selenium constitutes an essential trace element for the human body. Moderate Se intake plays a pivotal role in preserving overall health. The absorption of Se by plants is primarily influenced by the available Se levels in soils, rather than by the soil total Se content, offering potential for exploring Se-rich crops in Se-deficient regions. In this study, we explore the factors influencing the Se bioaccumulation coefficient in corn based on a land quality geochemical survey at a 1:50,000 scale and establish predictive models for corn seed Se content using random forest and multiple linear regression approaches. The results indicate that the surface soil in the study area is deficient in Se (0.18–1.21 mg/kg), but 54% of the corn grain samples met the standards for Se-rich products (0.02–0.30 mg/kg). The factors influencing the Se biological enrichment coefficient in corn seeds are soil pH and CaO and MgO content, with impact levels of 0.54, 0.42, and 0.35, respectively. Compared to multiple linear regression models, the RF model provides more accurate and reliable predictions of corn Se content. The random forest model indicates that approximately 41% of the farmland within the study area is conducive to the cultivation of naturally Se-rich corn, which is a 26% increase in the planting area compared to recommendations based solely on soil Se content. In this research, we introduce an innovative methodological framework for organically cultivating naturally Se-rich corn within regions affected by Se deficiency. [ABSTRACT FROM AUTHOR]

In this study, we present summary statistics for multi-element soil geochemistry across Western Australia based on over 74 000 soil samples using the UltraFine+® method that extracts and analyses the clay (<2 μ m) fraction of a soil sample. This method is a critical advancement for the detection of mobile element signatures for soil geochemical mineral exploration surveys in cover. However, existing estimates of background metal abundances acquired with other methods and on different sample media do not readily provide context for these analyses, as recovery from the fine fraction differs to that of whole-sample analysis. We therefore present herein the geochemical results for 52 elements, including precious, base and critical metals, as well as commonly associated pathfinder elements for Western Australian samples analysed during several research projects by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). This dataset is separated by tectonic unit into the Eastern Goldfields Superterrane and the Youanmi Terrane in the Yilgarn Craton, the Pilbara Craton and Sylvania Inlier, the Gascoyne, Lamboo and Aileron Provinces, and the Bryah and Earaheedy Basins to provide exploration-relevant context in these areas. We discuss some of the general trends observed for 12 of these elements, as well as some considerations for the use of these data in comparison to other geochemical soil surveys and with regards to mineral exploration settings. The samples presented in this study are not evenly distributed across Western Australia and limited information is available to correlate whether lithology at depth is mineralized or barren. However, in the absence of other systematic datasets using the <2 μ m-size fraction, these data present a suitable first-pass resource of element abundance ranges in areas of mineral exploration interest using the UltraFine+® method in some of the mineral-endowed areas of Western Australia. Supplementary material: Supplementary data A, UltraFine+® Soil Sampling Guide; B, UltraFine+® analyses results for available samples in Western Australia; C, Summary statistics of UltraFine+® analyses by simplified tectonic units; Supplementary Figure 1, Comparison of elemental mean values and uncertainties for ultrafine reference materials QC 320 and QC 422; Supplementary Figure 2, Violin plots of Ni, Cd, Mg and Au by simplified tectonic unit; Supplementary Figure 3, Location of soil samples in the Eastern Goldfields Superterrane analysed via UltraFine+®, and those collected as part of the NGSA and GSWA regolith programme; Supplementary Figure 4, Comparison of W, Al, Mg and Ca results from UltraFine+®, NGSA and GSWA analyses in the Eastern Goldfields Superterrane are available at https://doi.org/10.6084/m9.figshare.c.6919933 [ABSTRACT FROM AUTHOR]

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]

The energy demand increased dramatically owing to the evolution of industrial and domestic requirements and the associated decrease in oil and gas resources. This study aims to evaluate El-Maghara coal (with about 52 MT reserve) as a potential hydrocarbon source. The collect samples were subjected to petrographic, chemical analyses and Rock–Eval pyrolysis to investigate the detailed characteristics of this coal. Chemically, this coal is high volatile bituminous coal with high H and S content. The high H/C ratio indicates the high extraction yield of coal. The main maceral group in the studied samples is vitrinite (62.8%) followed by liptinite (31.3%) and inertinite (5.8%). The content of liptinite indicates the capability of this coal for petroleum production. Based on Rock–Eval Pyrolysis results and TOC content, the coal has excellent petroleum potential. The hydrogen index (HI) and H/C atomic ratio indicate the II kerogen type (oil prone) of this coal. This coal has Tmax and vitrinite reflectance values around 415.8 °C and 0.37%, respectively, indicating the immature stage of kerogen. The high reactive maceral content (94.2%), oil-yield (65.5%) and conversion from coal to oil (95.4%), indicated that this coal has a hydrocarbon generation potential for oil. [ABSTRACT FROM AUTHOR]

The sedimentary successions of the Permian-Triassic rifting related to the Alpine Tethys in the easternmost Lower Alpujarride units (Internal Betic Zone, south Spain) host shallow-intrusive basic bodies of Mesozoic age. These gabbroic bodies experienced low-grade Alpine metamorphic overprint, singularly recorded in three outcrops nearby Alicante city in southeast Spain: Callosa and Orihuela Ranges and Nueva Tabarca Island. Overall, the metabasic bodies still preserve magmatic ophitic/subophitic texture and relicts of magmatic augite and ferropargasite-ferroedenite-edenite and kaersutite. In contrast, metamorphic minerals include magnesioriebeckite, actinolite, albite, stilpnomelane, phengite, and chlorite. Major and trace element geochemical data suggest crystallization of the igneous protoliths from subalkaline (tholeiitic) to alkaline within-plate (continental) basaltic magmas slightly enriched in incompatible elements. These magmas with E-MORB geochemical affinity very likely intruded at shallow crustal levels in an extensional-synrift-geodynamic setting related to the breakoff of Pangea in the region. Pressure-Temperature (P-T) conditions estimated by average P-T method and pseudosection calculations suggest metamorphic peak at ca. 6 kbar at 340°C consistent with burial metamorphism down to ca. 18 km depth with intermediate thermal gradients of ca. 18°C/km. These conditions are different to the typical subduction-related blueschist facies conditions of the Lower Alpujarride units and suggest, instead, a collisional (Barrovian) event. This can be explained by a late-stage accretion of the studied units after the main subduction-related event, pointing to the dispersion of the corresponding Lower Alpujarride sections along the margin in different palaeogeographic positions before deformation and movement to their actual structural position. The metamorphic correlation of the studied units with the accreted passive margin of South Iberia (Subbetic zone) is also discussed. [ABSTRACT FROM AUTHOR]

Soil geochemical study was carried out in Ogudu-Ogbagba area of Osun State, Southwestern Nigeria to evaluate a prospect for gold mineralization. Ninety (90) soil samples from B-horizon were collected from the study area. The samples were air dried and sieved with a 177-μm sieve, while approximately 1.0 g each of the sieved samples was digested using hot aqua regia (3HCl + 1HNO3). The resulting solutions were analysed for Ag, Au, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn, using Flame Atomic Absorption Spectrometer (AAS) at the Department of Geology, Obafemi Awolowo University Ile-Ife. The geochemical data were subjected to both qualitative and quantitative analyses using univariate and multivariate statistical methods. The data were also used to plot location point symbol and contour geochemical maps of these metals with Arc GIS software, Oasis Montaj and Suffer 11 softwares. The results revealed that the ten (10) metals determined in the soils have anomalous concentration values, out of which only Au, Cd, Fe and Ni are considered to be significant because of their associations. These metals are suggested to be derived from primary sources. The study concluded that gold mineralization exists in the study area with occurrence of minor sulphides. The spatial distribution of the elements as shown in the geochemical maps indicate the most promising areas for both primary and alluvial gold prospecting in the area with Cd and Ni as pathfinder elements are Ogudu area and the north-western part of Ajebandele. [ABSTRACT FROM AUTHOR]

In this paper, the samples were treated with sodium carbonate and zinc oxide semi-melting method, and 732 cation exchange resin was used to separate a large number of cations from the solution after extraction with ethanol-boiling water, and the iodine in the sample solution was determined by Inductively coupled plasma mass spectrometry (ICP-MS) with pre-added internal standard method. By tuning the parameters of apparatus and optimizing the semi-melting procedure, the melting effect of the sample was improved. The measuring medium and internal standard element were optimized to eliminate the memory effect, and the stability of the results was improved. A robust and comprehensive ICP-MS method for iodine determination was established. Method validation was using Chinese national level standard substances for soil and stream sediment, with a relative error (RE) of 0.13–1.03% and a relative standard deviation (RSD) (n = 12) of 1.83–2.80%. The limit of detection (LOD) of the method was 0.039 μg/g, and the limit of quantification (LOQ) of the method was 0.13 μg/g. This study meets the requirements of sample analysis for geochemical survey and can be applied to the analysis and testing of large quantities of soil and sediment samples in geochemical survey. [ABSTRACT FROM AUTHOR]

Geological explorations have revealed plentiful Neogene formation waters in anticlines in the central Qaidam Basin (QB). However, the hydrochemistry and origin of these waters are obscure. In this study, the hydrochemistry and D‐O‐S‐Sr isotopes of these formation waters were determined to study their origin and evolution. The formation waters are enriched in Na‐Ca‐Cl, and depleted in Mg‐K‐SO4‐HCO3 ions with elevated Li‐B‐Br‐Sr elements. The D‐O isotopes prove that the formation waters originated from weak‐evaporated meteoric waters, and experienced water‐rock interactions. Ion comparisons and Caexcess–Nadeficit diagrams suggest that solute sources of these waters include evaporite dissolution, water‐rock interaction, and minor residual lake brines. Bacterial sulfate reduction and water‐rock interactions are supported by the high S‐Sr isotopes. The enriched Li‐B‐Br‐Sr concentrations of these waters are in accord with the high geochemical background values of the QB. Regarding the genesis of the formation waters, it can be concluded that meteoric waters from the southern Kunlun Mountains were discharged into the basin, weakly evaporated, and then infiltrated into the Neogene strata through faults leaching the soluble ions and mixing with residual lake brines, and all experienced water–rock interactions and a sulphate reduction process. [ABSTRACT FROM AUTHOR]

Pensacola Dam, operated by the Grand River Dam Authority (GRDA), is a multiple-arch buttress dam constructed in 1940. The dam has little or no existing geophysical reports on the integrity of the dam foundation rock and even less knowledge at depth. Visual inspection indicated evidence of seepage at some arches of the dam. As a pilot study, we conducted a suite of geophysical surveys inside two arches (Arch-16 and Arch-17) and a part of the downstream berm to characterize the dam foundation rock, delineate seepage zones, and identify the most appropriate geophysical methods for temporal monitoring of the dam's conditions. The geophysical methods included electrical resistivity tomography (ERT), self-potential (SP), multichannel analysis of surface waves (MASW), compressional (P)-wave refraction, and shear (S)-wave reflection. Water samples were collected for geochemical analysis to investigate the source of the seepage flow inside Arch-16. The geophysical results characterized the dam foundation rock into an unsaturated limestone and chert overlying a water-saturated limestone and chert. The ERT profiles indicated that groundwater is rising inside the arches and significantly dropping under the downstream berm, which can be due to the uplift pressure beneath the dam base. Zones of high seepage potential were detected near the buttress walls of the two surveyed arches, which may be related to previous blasting, excavation of the dam foundation, concrete placement, or improper grouting. The geochemical analysis of water samples taken from the artesian wells inside Arch-16 and the Grand Lake revealed different chemical compositions, suggesting that the source of water could be a mixture of groundwater and lake water or lake water interacting with rock and reaching the surface through fractures; however, more sampling and further analysis are required to ascertain the source of the seeps. This study showed that the ERT, SP, and S-wave reflection methods have effectively characterized the dam foundation rock and seepage zones beneath the arches. The study provided a better understanding of the conditions of the dam foundation rock, evaluated the utilized geophysical methods, and determined the optimum geophysical methods that can be used for the characterization and monitoring of the subsurface conditions along the entire length of the dam. In this study, we have demonstrated that the integration of effective geophysical surveys and geochemical analysis yielded optimum results in solving a complex dam safety problem. This strategy promotes the best practice for dam safety investigation. [ABSTRACT FROM AUTHOR]

Water pathways and water contamination in mixed land‐use catchments are complex to understand. Runoff‐generating sources can be numerous and water pathways modified by anthropogenic elements. Monitoring surveys considering geochemical and microbial parameters, are often carried out on such catchment, but are often simple in terms of studied parameters. Nonetheless, they can be helpful to identify the specific signatures of the main runoff‐generating sources and estimate their contribution to total runoff at the outlet of mixed land‐use catchments. Based on a monthly biogeochemical monitoring program conducted between 2017 and 2019 in the Ratier catchment (19.8 km2) near Lyon (France), a step‐by‐step approach was developed to: (1) identify the main runoff‐generating sources using a perceptual model of the Ratier catchment, (2) identify the respective biogeochemical signatures of each source using this biogeochemical dataset and hydro‐meteorological indicators and (3) estimate their contribution to the stream total runoff using an End‐Member Mixing Analysis method. We identified three main runoff‐generating sources outside of rainy periods: a colluvium aquifer, a fractured gneiss aquifer and a saprolite layer. The monitored geochemical datasets were found divided into three groups matching these sources. Contributions of these sources were estimated based on representative tracer concentrations. Microbial parameters showed a homogeneous agricultural and anthropogenic contamination among the catchment surface water, but also deeper into the fractured gneiss groundwater. This approach showed the potential of using simple monitoring datasets to identify runoff‐generating sources and estimate their contribution to total runoff. [ABSTRACT FROM AUTHOR]

Periodically visiting soil monitoring sites, i.e., sampling and analysis, is recognized as one of the most important ways to monitor soil quality. However, reconciling the monitoring costs with monitoring precision of the soil monitoring network (SMN) is a key technical problem to be solved. A statistically sound method, which depends on the spatial variation in monitoring indicators, was adopted to determine the number of monitoring sites and the monitoring interval as well as their ability to detect a particular change under an economically feasible scenario. The spatial variation in soil monitoring indicators was inquired from the "Multi-Purpose Regional Geochemical Survey in Zhejiang Province (MRGSZ)" project. Based on the data for soil pH and concentration of potentially toxic elements, the number of monitoring sites and the monitoring intervals that might be used for soil monitoring were determined with the administrative region as the monitoring unit. The results showed that there was great spatial variation in the MRGSZ region, which resulted in discrepancies in the minimum detectable changes (MDCs), monitoring site numbers, and temporal monitoring intervals for revisiting. Our research proposes a number of monitoring sites (nr) that could reconcile the monitoring costs, practicability and monitoring precision; thus, it was recommended for the design of SMNs. Under nr, the MDC values of each monitoring indicator were acceptable for all administrative regions, and the temporal monitoring intervals were practical with variations of 6.7–14.8 years. [ABSTRACT FROM AUTHOR]

Geochemical surveys contain an implicit data lifecycle or pipeline that consists of data generation (e.g., sampling and analysis), data management (e.g., quality assurance and control, curation, provisioning and stewardship) and data usage (e.g., mapping, modeling and hypothesis testing). The current integration of predictive analytics (e.g., artificial intelligence, machine learning, data modeling) into the geochemical survey data pipeline occurs almost entirely within the data usage stage. In this study, we predict elemental concentrations at the data generation stage and explore how predictive analytics can be integrated more thoroughly across the data lifecycle. Inferential data generation is used to modernize lake sediment geochemical data from northern Manitoba (Canada), with results and interpretations focused on elements that are included in the Canadian Critical Minerals list. The results are mapped, interpreted and used for downstream analysis through geochemical anomaly detection to locate further exploration targets. Our integration is novel because predictive modeling is integrated into the data generation and usage stages to increase the efficacy of geochemical surveys. The results further demonstrate how legacy geochemical data are a significant data asset that can be predictively modernized and used to support time-sensitive mineral exploration of critical minerals that were unanalyzed in original survey designs. In addition, this type of integration immediately creates the possibility of a new exploration framework, which we call predictive geochemical exploration. In effect, it eschews sequential, grid-based and fixed resolution sampling toward data-driven, multi-scale and more agile approaches. A key outcome is a natural categorization scheme of uncertainty associated with further survey or exploration targets, whether they are covered by existing training data in a spatial or multivariate sense or solely within the coverage of inferred secondary data. The uncertainty categorization creates an effective implementation pathway for future multi-scale exploration by focusing data generation activities to de-risk survey practices. [ABSTRACT FROM AUTHOR]

Shallow crystalline groundwater in the semi-arid hinterland of Ceará is brackish or saline with mixed chloride or sodium chloride facies. Very few hydrochemical data are available for the area and the drivers behind this salinity are not clearly identified. In this study, extensive field data collection was performed to provide new information about the hydrogeological functioning and the salinization processes, through the implementation of piezometric, hydrogeochemical, isotopic ( 18O, ²H) and multitracer dating (14C, ³H, CFC, SF6) monitoring. Piezometric and isotopic data evidence fast flow circulation processes and a high contribution of evaporated surface water to aquifer recharge. Multitracer dating shows the groundwater is essentially composed of seasonal vertical infiltration flows that mix with older waters stored in the aquifer. Chemical analyses suggest the groundwater, originally low mineralized, has become progressively saltier due to leaching of salts that were evapoconcentrated in either surface waters or the unsaturated zone during drier periods. [ABSTRACT FROM AUTHOR]

The manifestations of some hot springs in Siogung-Ogung, North Sumatra, Indonesia have increased speculation of likely geothermal sources. Therefore, integrated geochemical and geophysical methods were employed to identify the geothermal prospect of the area. Two-dimensional electrical resistivity and geomagnetic methods were used for the geophysical survey. The geochemical survey used three concentration measurements: geothermometer silica (SiO2), geothermometer Na-K, and geothermometer Na-K-Ca. A Wenner Schlumberger array with a 5-meter electrode spacing was used to acquire the 2-D resistivity data, which was processed using Res2Dinv software. The geomagnetic method was performed with a proton precession magnetometer, and the data were processed using Surfer to produce the magnetic residual map. The 2-D electrical resistivity results show that the area has low resistivity values (1-700 Ωm). The resistivity values from 1 to 100 Ωm could be due to the presence of hot waters in alluvium, and the resistivity values > 400 indicate andesite rock, which can function as a hot water conductor from the source. The magnetic residual map shows geomagnetic values from 150 nT to 360 nT, which infer the potentiality of geothermal within the study area. The geochemical results show that the reservoir temperature is 572 °C. Based on the integrated results, the study area has promising geothermal potential. [ABSTRACT FROM AUTHOR]

Geochemical investigations carried out on thermal waters over the Erzin-Hatay area allowed the collection of a suite of 9 samples from natural springs and one well characterized by outlet temperatures in the range from 19.6 to 31.5 °C. All of the springs have slightly acidic pH (in the range of 6) but one sample was marked by a pH value >11 as a consequence of serpentinization processes. The water chemistry denotes water/rock interactions with either magmatic or carbonatic rocks in a water reservoir equilibrated at temperatures estimated to be in the range of 58-162 °C. The stable isotope composition of the collected waters, in terms of dD and d18O, denotes a recharge from local meteoric waters. The dissolved gases denote the contribution of no atmospheric components. CO2 is the dominant dissolved component for most of the sample, while methane is the major component for the thermal water involved in serpentinization. Besides the main components CO2 and CH4, the dissolved gases show significant concentrations of He, H2, and CO. The isotopic composition of helium shows ³He/4He ratios well above that of Air Saturated Waters (ASW = 1.39 x 10-6) clearly indicating a significant contribution of 3He of mantle origin. Taking into account the location of some sampling sites nearby the Düziçiİskenderun Active Fault Zone and the associated mantle helium contribution, we propose that fluids/faults relationships have to be considered as responsible for the feeding of deep-originated fluids to the shallow groundwater. As mantle-derived fluids are also carriers of thermal energy, the collected results strongly suggest improving the knowledge of the study area, where hydrological and geochemical considerations coupled with the tectonic setting of the area should focus on the geothermal potential of the circulating waters. [ABSTRACT FROM AUTHOR]

Interactive depositional systems of marine carbonates and gypsum salt rocks are closely related to natural gas reservoirs. Despite continuous progress in the exploration of new areas of marine carbonate genesis within the Ordos Basin, the source and mechanism of "sub-salt" natural gas genesis remains controversial. In this study, we investigated natural gas genesis through geochemical analysis of Lower Paleozoic natural gas samples from the mid-eastern Ordos Basin, obtaining natural gas composition data and carbon/hydrogen isotope compositions. We found evident differences between the geochemical characteristics of "sub-salt" and "post-salt" natural gas; the methane carbon isotope signature of "sub-salt" natural gas was lighter overall than that of "post-salt" natural gas, while the ethane carbon isotope composition of the former was more widely distributed and partially lighter than that of the latter. Combining these data with the regional geological background and existing geochemical data, it is evident that Ordovician "post-salt" natural gas comprises a composite of Upper Paleozoic coal-type gas and Lower Paleozoic oil-type gas, with the oil-type gas accounting for the largest proportion. In contrast, the "sub-salt" natural gas was formed and preserved within the Ordovician marine carbonates or sourced from deeper and more ancient hydrocarbon source rocks. Geochemical anomalies, including light methane carbon isotopes and ethane carbon isotopes with coal-type gas characteristics, are closely related to the prevalence of thermochemical sulfate reduction during hydrocarbon formation and reservoir formation of natural gas in "sub-salt" strata. [ABSTRACT FROM AUTHOR]

Uncertainty associated with the identification of geochemical anomalies linked to mineralization has been a major concern in processing geochemical survey data. In this study, a Monte Carlo-based workflow, consisting of simulation-based local singularity analysis (LSA) and distance-based generalized sensitivity analysis (DGSA), was presented to identify geochemical anomalies associated with mineralization under uncertainty and simultaneously perform sensitivity analysis of model parameters. A case study of processing 1:200,000 stream sediment geochemical samples collected from the southwestern Fujian Province of China further illustrates and validates the procedure. The obtained results suggest that (i) the procedure is useful and flexible for identifying geochemical anomalies associated with mineralization under uncertainty and studying the sensitivities of model parameters, because different types of uncertain parameters and responses can be incorporated into the procedure, (ii) the window parameters are critical for applying LSA to identify geochemical anomalies related to mineralization, and spatial uncertainty associated with the gridding procedure is also important and can not be ignored, and (iii) the averaged singularity intensity map of the study area can serve as a valid indicator of Cu mineralization, while the uncertainty map of local singularity exponents can provide crucial information for decision-making in later stages of mineral exploration. [ABSTRACT FROM AUTHOR]

Since the 1970s, till geochemical and indicator mineral methods for mineral exploration, provenance studies and environmental research in glaciated terrain have been developed, tested and refined. This review summarizes these methods, focusing on field and laboratory methods for till geochemical, indicator mineral and boulder surveys. This review of protocols is intended as a guide for the mineral exploration industry and publicly funded agencies. It summarizes till as a sample medium, and describes the formation of glacial dispersal trains, along with methods for till sample collection, sample processing, matrix geochemistry, indicator mineral analyses, quality assurance/quality control procedures and data reporting and interpretation. The methods described here can be used to conduct reconnaissance- to deposit-scale till sampling surveys to assess mineral resource potential and establish environmental baselines. Supplementary material: Appendix A – Photographs of till types described in text; Appendix B – Logistical and geological factors to consider in till sample survey design; Appendix C – Photographs of glaciate terrain types described in text; and Appendix D – Till sample processing and analysis flow charts are available at https://doi.org/10.6084/m9.figshare.c.6786087 Thematic collection: This article is part of the Reviews in Exploration Geochemistry collection available at: https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry [ABSTRACT FROM AUTHOR]

Stream sediment surveys support early-stage reconnaissance mineral exploration and regional assessment programmes, enhanced by recent improvements in analytical method detection limits, continuously improving mineral chemistry, and new approaches to the interpretation of geochemical data. Sediment surveys may be used to predict catchment basin lithology, mineralization type based on pathfinder geochemistry, and geological features based on indicator mineral chemistry. Sediment surveys that target a finer-fraction sediment sample led to the discovery of the La Colosa gold deposit, Colombia. The Batu Hijau porphyry Cu–Au deposit in Indonesia was discovered based on an anomalous clay-sized fraction sample 12 km downstream. In an arid region with poorly developed drainages and minor topographic relief, the Ag-base-metal Navidad District in Argentina was discovered with clay-fraction sediment geochemistry. Heavy mineral concentrate (HMC) sediment surveys that include mineral chemistry determinations have led to global diamond discoveries. HMC surveys contributed to discovery of the Ring of Fire Ni–Cu–PGE and chromite district, Ontario, Canada. Discoveries and geochemical mapping can assist advancement of the application of stream sediment geochemistry in those global areas for which lithologies and deposits are exposed. Stream sediment surveys continue to be one of the most cost-effective geochemical methods for covering large areas for mineral exploration. Thematic collection: This article is part of the Reviews in Exploration Geochemistry collection available at: https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry [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]

In this paper, we provide a characterisation of the ionosphere from April 2018 to September 2022 for 48 investigated months. We used the data of the China Seismo Electromagnetic Satellite (CSES-01), which is a sun-synchronous satellite with five days of revisit time and fixed local time of about 2 a.m. and 2 p.m. The unique orbit of CSES-01 permitted us to produce a monthly background of the ionosphere for night- and daytime with median values acquired during geomagnetic quiet time in equatorial and mid-latitude regions (i.e., between 50° S and 50° N of geographical latitude). We compared the obtained CSES-01 monthly median values with the solar activity in terms of sunspot numbers, and we found a high correlation of 0.89 for nighttime and 0.85 for daytime between the mean sunspot number and the maximum of the characterised CSES-01 Ne map values. In addition, we extracted all the anomalous positive increases in CSES-01 electron density and compared them with the Worldwide M5.5+ shallow earthquakes. We tested two different definitions of anomaly based on median and interquartile range or (mild) outliers. We tried two relationships between anomalies inside Dobrovolsky's area before the earthquake and the magnitude of the same seismic events: one which considers distance in space and time and a second which only uses the anticipation time of the anomaly before the earthquake. Using both anomaly definitions, we searched the best coefficients for these two laws for mid-latitude and equational regions. We found that the best coefficients are independent of the anomaly definition, but better accuracy (greater than 80%) is obtained for the outlier definition. Finally, using receiving operating characteristic (ROC) curves, we show that CSES-01 increases seem statistically correlated to the incoming seismic activity. [ABSTRACT FROM AUTHOR]

Geochemical mapping based on machine learning algorithms has been proven to significantly improve the efficiency of geological mapping related to mineral exploration. This process is generally implemented by interpolating discrete geochemical data into spatially continuous fields and comparing chemical composition and spatial distribution to a reference. However, the use of geochemical survey data for geological mapping is challenging because of discontinuous geochemical sampling and inferior model performance owing to the restriction of insufficient training samples and spatial feature representations. Geochemical data interpolation is subject to uncertainty that also deserves be quantified. This study addresses the above challenges by using a direct sampling (DS) multiple-point statistical technique in conjunction with a convolutional neural network (CNN) algorithm. Specifically, the DS technique is designed to produce spatially continuous and sufficient samples by reconstructing unsampled locations from sparse geochemical survey data; and CNN facilitates automatic lithological feature learning and classification based on multilevel convolutional operations that considers the spatial information within neighboring samples. The proposed framework is illustrated in a case study mapping lithological units in Daqiao district, western China, and compared with the deterministic interpolation approach visually and quantitatively. Most lithological units were correctly identified with an overall accuracy of 94%, providing feasible and practical insight into geological mapping using stream sediment geochemical survey data. [ABSTRACT FROM AUTHOR]

A geological study of the Kipala region, in the "Cuvette Centrale" of the Democratic Republic of Congo, has identified two groups of shales: the dark greasy facies, interbedded with the brownish-gray facies. Their high Total Organic Carbon (TOC) content (11 % TOC on average for the dark greasy shales, compared with 8 % for the second group) classifies them as very good hydrocarbon source rocks, according to the criteria of Epistalie et al. Field and laboratory data suggest that the rocks studied were deposited in a lagoon connected to the sea by an intermittently closing channel. [ABSTRACT FROM AUTHOR]

The regional geochemical mapping was carried out in the Indo-Gangetic alluvial plain of the Western and Central India which was previously classified as Varanasi alluvium, a polycyclic sequence of large alluvial fans transported by perennial Himalayan Rivers. The results based on the geochemical dispersion pattern of major and minor oxides as well as trace elements conclude that there are four major factors determining the dispersion patterns of the variables which are: (1) the underlying lithology with a strike of NE-SW, (2) transport of sediments along the general slope of the study area towards south and south-west as reflected in the Digital Elevation Model, (3) formation of Reh and (4) anthropogenic influence. The present study focusing on the effect of the underlying geology on the geochemical signature of the study area infers that the geochemical distribution pattern of certain variables clearly follows the trend of the Delhi fold belt. It can be interpreted that the subsurface lithology belonging to Delhi Supergroup is present at a depth of 500m which is considerably shallower, imprinting its geochemical signature on the sediments. The presence of minor outcrops of quartzite belonging to the Delhi Supergroup with the NE-SW strike is also documented in the study area. Based on this study we propose to reclassify the Varanasi Alluvium sediments as equivalent to Banda Alluvium. The study also demonstrates the utility of geochemical mapping as a tool to map the subsurface geology of an alluvial terrain. The results of this study are also corroborated by the regional scale gravity survey. [ABSTRACT FROM AUTHOR]

The Reshui area, located to the northeast of the Qinghai–Tibet Plateau, exhibits complex geological conditions, well-developed structures, and strong hydrothermal activities. The distribution of hot springs within this area is mainly controlled by faults. In this paper, five hot springs from the area were taken as the research object. We comprehensively studied the geochemical characteristics and genetic mechanism of the geothermal water by conducting a field investigation, hydrogeochemistry and environmental isotopic analysis (87Sr/86Sr, δ2H, δ18O, 3H). The surface temperature of the geothermal water ranges from 84 to 91 °C. The geothermal water in the area exhibits a pH value ranging between 8.26 and 8.45, with a total dissolved solids' (TDS) concentration falling between 2924 and 3140 mg/L, indicating a weakly alkaline saline nature. It falls into the hydrochemical type CI-Na and contains a relatively high content of trace components such as Li, Sr, B, Br, etc., which are of certain developmental value. Ion ratio analysis and strontium isotope characteristics show that the dissolution of evaporite minerals and carbonate minerals serves as a hot spring for the main source of solutes. Hydrogen and oxygen stable isotope characteristics findings indicate that the geothermal water is primarily recharged via atmospheric precipitation. Moreover, the tritium isotopic data suggest that the geothermal water is a mixture of both recent water and ancient water. Moreover, the recharge elevation is estimated to be between 6151 and 6255 m. and the recharge area is located in the Kunlun Mountains around the study area. The mixing ratio of cold water, calculated using the silicon enthalpy equation, is approximately 65% to 70%. Based on the heat storage temperature calculated using the silicon enthalpy equation and the corrected quartz geothermal temperature scale, we infer that the heat storage temperature of geothermal water in the area ranges from 234.4 to 247.8 °C, with a circulation depth between 7385 and 7816 m. The research results are highly valuable in improving the research level concerning the genesis of high-temperature geothermal water in Reshui areas and provide essential theoretical support for the rational development and protection of geothermal resources in the area. [ABSTRACT FROM AUTHOR]

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A novel method of estimating the silica (SiO2) and loss-on-ignition (LOI) concentrations for the North American Soil Geochemical Landscapes (NASGL) project datasets is proposed. Combining the precision of the geochemical determinations with the completeness of the mineralogical NASGL data, we suggest a 'reverse normative' or inversion approach to first calculate the minimum SiO2, water (H2O) and carbon dioxide (CO2) concentrations in weight percent (wt%) in these samples. These can be used in a first step to compute minimum and maximum estimates for SiO2. In a recursive step, a 'consensus' SiO2 is then established as the average between the two aforementioned SiO2 estimates, trimmed as necessary to yield a total composition (major oxides converted from reported Al, Ca, Fe, K, Mg, Mn, Na, P, S and Ti elemental concentrations + 'consensus' SiO2 + reported trace element concentrations converted to wt% + 'normative' H2O + 'normative' CO2) of no more than 100 wt%. Any remaining compositional gap between 100 wt% and this sum is considered 'other' LOI and likely includes H2O and CO2 from the reported 'amorphous' phase (of unknown geochemical or mineralogical composition) as well as other volatile components present in soil. We validate the technique against a separate dataset from Australia where geochemical (including all major oxides) and mineralogical data exist on the same samples. The correlation between predicted and observed SiO2 is linear, strong (R2 = 0.91) and homoscedastic. We also compare the estimated NASGL SiO2 concentrations with a sparser, publicly available continental-scale survey over the conterminous USA, the 'Shacklette and Boerngen' dataset. This comparison shows the new data to be a reasonable representation of SiO2 values measured on the ground over the conterminous USA. We recommend the approach of combining geochemical and mineralogical information to estimate missing SiO2 and LOI by the recursive inversion approach in datasets elsewhere, with the caveat to always validate results. [ABSTRACT FROM AUTHOR]