Soil Geochemical Survey Research Articles

Ecological and Geochemical Assessment of the State of Soils in the City of Baikalsk According to the Content of Polycyclic Aromatic Hydrocarbons

The pollution of the topsoils of the city of Baikalsk (Irkutsk region) under the influence of industrial emissions and wastes of the Baikal Pulp and Paper Mill (BPPM) was studied. The content of 16 individual PAH structures in samples of urban and background soils taken during the soil geochemical survey in the summer of 2019 was analyzed. Relatively low levels of PAH content were found in the lignin sludge from the BPPM and СHP ash. The concentration of total PAHs in CHP ash reaches 46 mg/ kg with a predominance of low molecular weight compounds (the proportion of naphthalene and its homologues is 24% and 34% of the total PAHs, respectively), among high molecular weight PAHs, 5-nuclear benzo(b)fluoranthene dominates (16%). In lignin sludge, the amount of PAHs is 7.16 mg/kg with the predominance of benzo(b)fluoranthene (83%). In the soils of Baikalsk, the average total content of PAHs (38.4 mg/kg) is 5 times higher than the background content. In urban soils, 4–5-nuclear fluoranthene (61.1%) and benzo(b)fluoranthene (29.4%) prevail. This makes it possible to attribute soil pollution to the fluoranthene type. The soils of the motor transport (total PAH 105 mg/kg) and industrial (59.5 mg/ kg) zones are the most polluted, where the most contrasting PAH anomalies were formed. In descending order of the amount of PAHs, the land use zones of the city form a series: motor transport industrial residential one-storey railway transport residential multi-storey recreational zone. Several local anomalies in the amount of PAHs are distinguished, forming two large pollution halos in the western and eastern parts of the city. The leading factors in the accumulation of high molecular weight PAHs in soils are acid-alkaline conditions and soil organic matter, while the accumulation of low molecular weight polyarenes is mainly controlled by pH. The environmental hazard of pollution of Baikalsk soils with polyarenes is due to benzo(b)fluoranthene, its contribution is 83.5%.

Prediction of the fluoride contents of different crop species via the random forest algorithm.

Fluoride (F) is a trace element that is essential to the human body and occurs naturally in the environment. However, a deficiency or excess of F in the environment can potentially lead to human health issues. The pseudototal amount of F in soil often does not correlate directly with the F content in plants. Instead, the F content within plants tends to have a greater correlation with the bioavailable F in soils. In large-scale soil surveys, only the pseudototal elemental content of soils is typically measured, which may not be highly reliable for developing agricultural zoning plans. There are significant variations in the ability of different plants to accumulate F from soil. Additionally, due to variations in soil elemental absorption mechanisms among different plant species, when multiple crops are grown in an area, it is typically necessary to study the elemental absorption mechanisms of each crop. To address these issues, in this study, we examined the factors influencing F bioaccumulation coefficients in different crops based on 1:50,000 soil geochemical survey data. Using the random forest algorithm, four indicators-bioavailable P, bioavailable Zn, leachable Pb, and Sr-were selected from among 29 parameters to predict the F content within crops to replace bioavailable F in the soil. Compared with the multivariate linear regression (MLR) model, the random forest (RF) model provided more accurate and reliable predictions of the fluoride content in crops, with the RF model's prediction accuracy improving by approximately 95.23%. Additionally, while the partial least squares regression (PLSR) model also offered improved accuracy over MLR, the RF model still outperformed PLSR in terms of prediction accuracy and robustness. Additionally, it maximized the utilization of existing geochemical survey data, enabling cross-species studies for the first time and avoiding redundant evaluations of different types of agricultural products in the same region. In this investigation, we selected the Xining-Ledu region of Qinghai Province, China, as the study area and employed a random forest model to predict the crop F content in soils, providing a new methodological framework for crop production that effectively enhances agricultural quality and efficiency.

Integration of Large Multielement Geochemical, Aeromagnetic, and Gravity Data to Geologically Map a Largely Covered Area: A Case Study from the Central African Copperbelt in Northern Zambia

Abstract This study provides a method to map lithology, stratigraphy, and structures in areas with limited outcrop using mineral exploration data from multielement soil geochemical surveys, airborne and ground geophysical surveys, and drill hole data sourced from multiple exploration companies and campaigns. The 45- by 50-km study area is located in the southern portion of the Congolese Copperbelt, where the regional geology, structure, and overall basin architecture were not well understood, partly due to thick saprolite cover. The results demonstrate that the integration of such data sets allows the creation of a geologically coherent map, which can then be used to investigate basin architecture and identify basin-forming structures.

Multi-element geochemical analyses on ultrafine soils in Western Australia – towards establishing abundance ranges in mineral exploration settings

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

Geochemical soil survey for gold in Ogudu-Ogbagba Area, Osun State, southwestern Nigeria

Geochemical soil survey for gold in Ogudu-Ogbagba Area, Osun State, southwestern Nigeria

Integrated Multi-Elemental Soil Geochemical Survey as a Tool in Geological Mapping in the Tropics: A Case Study of Songbe Area of Osun State, West Africa

Integrated Multi-Elemental Soil Geochemical Survey as a Tool in Geological Mapping in the Tropics: A Case Study of Songbe Area of Osun State, West Africa

Geochemical distribution in residual soils of Iberian Pyrite Belt (Spain)

The Iberian Pyrite Belt (IPB) is a volcanic- and shale-hosted massive sulfides world-class province of the Upper Paleozoic age that includes some supergiant ore deposits with a unique mining operations history. An extensive soil (multi-element) geochemical survey in the IPB has been performed to create a geochemical database to increase the knowledge of the studied area. Both univariate and multivariate treatments have been done to manage a large amount of new data. The studied area shows higher background concentrations of several elements (e.b. Cu, Pb, Zn, Cd, Sn, In, Bi, As, or Sb) than in other terrains in Spain due to the IPB volcano-sedimentary ore deposits and their associated mining wastes. Mapping chemical elements help understand their behavior, controls and associations in natural environments. According to this, the mono-elemental contour maps show single-element distributions with geological control (e.g., Na), ore deposit control (e.g., Cu) or a mixture of both. On the other hand, multivariate analysis has been applied to reduce the large geochemical database maintaining the same information. We have chosen Factorial Analysis (FA) and obtained six factors that explain approximately 70% of the variability. Four of these factors (F1, F2, F4 and F5) show an intense geological control that improves the geological information of the IPB, while the other two (F3 and F5) show an ore deposit control. These factors allow distinguishing between different types of deposits in the IPB and help discover new possible exploration targets for future studies.

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

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

TRENDS OF SOIL CONTAMINATION WITH HEAVY METALS AND OIL PRODUCTS IN THE CITIES OF BELARUS

The results of the analysis of the current state and dynamics of concentrations of heavy metals and oil products in the soils of Belarusian cities for the period from 1990–1995 to 2016–2021 are presented. It is based on the soil monitoring data in the cities of Belarus within the framework of the National Environmental Monitoring System in the Republic of Belarus and the results of a detailed soil-geochemical survey of the city of Minsk, carried out by the authors in 1990. The dynamics of the content of chemicals in the soils of cities was assessed by comparing the average
 concentrations for individual cities over the period under review and with comparison of the concentrations of chemicals in soil samples taken at the same sampling sites in the city of Minsk over a nearly 30-year period. It has been established that for most cities there is a tendency to accumulate zinc and oil products in the soil cover. There is a decrease in the content of lead in the soil in 46 % of cities and an increase in its concentration in 19 % of cities are observed. Similar to lead dynamic is typical for copper content in urban soils. It is shown that the annual average increase in the content of zinc in the soils of Minsk is 0.57 mg/kg per year, while the annual average decrease in the content of lead is 0.22 mg/kg per year.

Effective delineation of rare metal-bearing granites from remote sensing data using machine learning methods: A case study from the Umm Naggat Area, Central Eastern Desert, Egypt

Albitized granite (ABG) is considered as one of the most significant hosts of rare metals (RMs). Consequently, adequate recognition of ABG through proper lithological discrimination highly increases the targeting of rare metal resources. In order to delineate outcrops of ABG from satellite data, our study integrates eight image enhancement techniques, including optimum index factor, false color composites, band rationing, relative band depth, independent component analysis, principal component analysis, decorrelation stretch, minimum noise fraction transform, and spectral indices ratios, for the interpretation of ASTER and Sentinel-2 (S2) datasets. This integrated approach allows the effective discrimination of AGB outcrops in the Umm Naggat area, Central Eastern Desert, Egypt. The interpretation maps derived from these integrated image processing techniques were systematically verified in the field and formed the base for the feature selection process (i.e., training and testing data delineation) of different lithologies supported by the support vector machine algorithm (SVM). In order to produce a high‐quality lithological interpretation map, SVM was applied to Sentinel-2, ASTER, and combined ASTER-S2 datasets. The fused ASTER-S2 classification properly delineates ABG, as verified by our field investigations and confirmed by previous geological maps. Furthermore, comprehensive structural analysis (lineaments extraction and their density map) and hydrothermal alteration detection were performed to check the spatial association between the distribution of ABG, higher density zones, and highly altered areas, that in turn, could shed light on new potentially mineralized zones and proposed exploration targets. Our study reveals new ABG occurrences mainly situated in the southern and southwestern parts of the study area, and it confirms the location of known mineralized zones in the northern part of the Umm Naggat region. The distribution of ABG and its spatial correlation with alteration and high structural density zones suggest that rare‐metal mineralization is mostly structurally controlled (NW, NNW, NNE, and N-S), demonstrating the higher possibility of metasomatic enrichment of rare-metals within the study area. Our study provides an updated geological map of the study area based on the SVM‐supported interpretation of ASTER-S2 data. Importantly, the results reveal a high exploration potential for rare‐metal mineralization at Umm Naggat and defining new anomalies for follow‐up work by geochemical soil surveys.

Application and Significance of Geological, Geochemical, and Geophysical Methods in the Nanpo Gold Field in Laos

As the main part of the Indosinian metallogenic province in the eastern part of the Tethys metallogenic domain, Southeast Asia has experienced multiple stages of tectonic magnetic activities accompanied by the formation of rich mineral resources. However, due to the undeveloped economy, low degree of geological work, dense vegetation cover, and lack of obvious prospecting marks, traditional geological prospecting work in the area is not optimal. Consequently, the combination of high-precision geophysics and geochemistry has become an important method of looking for ore bodies deep underground in this area. The Nanpo gold deposit is a hydrothermal gold deposit that occurs in the Indosinian felsic volcanic rock body, and its mineralization is closely related to felsic magmatism. This study carried out comprehensive geophysical and geochemical exploration methods of soil geochemical survey, induced polarization (IP) survey, and audio-frequency magnetotelluric (AMT) survey. Based on the characteristics of geophysical and geochemical anomalies, geological inference, and interpretation, the integrated geophysical and geochemical prospecting criteria of the ore area have been determined: The large-scale and overlapping Au-Ag-Cu anomaly area in the host felsic magmatic rocks (mainly diorite, monzodiorite and granodiorite) is a favorable metallogenic area. Two anomalies, P1–H1 and P3–H6, with the best metallogenetic conditions and the deepest extensions of the known ore bodies, were further selected as engineering verification targets. After the study of the drill core, gold (mineralized) bodies consistent with the anomalies were found, indicating that the combined method is suitable for the exploration of mineral resources in this area, and the prospecting effect is good. At the same time, the metallogenic prediction shows that the deep part of the mining area still has great metallogenic prospects and prospecting potential. The characteristics of geophysical and geochemical anomalies and prospecting experience in the study area can provide references for the prospecting of hydrothermal gold deposits in the Luang Prabang–Loei structural belt.

Modelling and Mapping Total and Bioaccessible Arsenic and Lead in Stoke-on-Trent and Their Relationships with Industry

This study was based on a geochemical soil survey of Stoke-on-Trent in the UK of 747 surface soil samples analysed for 53 elements. A subset of 50 of these soil samples were analysed for their bioaccessible As and Pb content using the Unified Barge Method. Random Forest modelling, using the total element data as predictor variables, was used to predict bioaccessible As and Pb for all 747 samples. Random Forest modelling, using inverse distance weighed predictors and bedrock and superficial geology, was also used to map both total and bioaccessible As and Pb on a 400 × 400 spatial prediction grid with a 50 m resolution. The predicted bioaccessible As ranged from ca. 1 to 8 mg/kg and the total As ca. 8 to 45 mg/kg. The bioaccessible Pb and the total Pb both covered the range ca. 16–1200 mg/kg, with the highest values for both forms of Pb showing similar spatial distributions. Predictor variable importance and information on past industry suggest that the source of both of these elements is driven by anthropogenic causes.

Application of ground magnetic and soil geochemical surveys for mapping potential kimberlite bodies in the southern margin of the Archaean Kaapvaal Craton, South Africa

In this study, the southern margin of the Archean Kaapvaal Craton in South Africa is selected to investigate the occurrences of potential kimberlite bodies. Ground magnetic survey was conducted to identify potential targets for further exploration. Euler 3D deconvolution and Keating correlation coefficients are the processing techniques that were applied to the ground magnetic data to identify geological features that correspond to kimberlite models. These techniques revealed several potential targets that resemble geologic models of kimberlite bodies. Seven of these targets (Targets A, B, C, D, E, F and G), spatially cluster along or at the intersections of linear structures, which is consistent with one of the primary geological conditions that control the emplacement of kimberlite bodies. A follow-up soil sampling and analysis was conducted to assess the geochemistry of soils at the seven targets. The major element geochemistry of soil samples suggest that Target B possesses residual soils that originated from kimberlite intrusion, while the remaining six samples show geochemical characteristics of soils derived from crustal rocks. The composition of compatible (Ni, Cr, V, Co, Cu and Zn) and incompatible (Nb, Zr, Sr, Ce, and Ba) trace elements of Target B shows similarity with the known Group 1 Kimberlites locally and globally, thus confirming that Target B most probably belongs to Group 1 Kimberlite petrological clan. This, however, does not preclude the possibility of modification of kimberlite chemistry by crustal assimilation during ascent and post-emplacement processes such as weathering as demonstrated by elevated concentrations of SiO2, Al2O3 and Rb and low content of MgO. In light of this, Target B may be interpreted as a potentially contaminated and weathered Group 1 Kimberlite pipe which intruded the Karoo Supergroup at the intersection of linear structures. This finding is consistent with the presence of large number of known diamondiferous kimberlites in this region, which post-date the formation of the Karoo Supergroup.

Geopedology-climate interactions govern the spatial distribution of selenium in soils: A case study in northeastern Brazil

Selenium (Se) is an essential trace element in humans with critical roles in immune functioning and antioxidant systems. Plant foods growing on soils with sufficient Se levels are the primary dietary sources of selenium. Therefore, knowing the factors that drive the concentration of Se in soils is essential to map Se deficiencies and toxicities and implement biofortification programs to enhance foodstuffs' mineral composition. Here, we assessed how geopedology-climate interactions govern the background concentration and spatial distribution of Se in soils from two northeastern Brazil states. A soil geochemical survey covering roughly 110,000 km2 collected 198 composite samples in sites with minimal anthropogenic influence and wide variation concerning soil types, geological and climatological settings. The samples had their Se concentrations determined by hydride generation atomic absorption spectroscopy (HGAAS) after microwave acid digestion. The results indicate that climate (precipitation) and bedrock are the main broad-scale factors on regional soil Se distribution, while soil contents of clay and organic matter influence Se values locally. Geographically weighted regression (GWR) showed that these factors change over space and exist in a spatial non-stationarity relationship with selenium. Se-deficient soils are most likely to occur in semi-arid settings overlying crystalline rocks, in which pedogenesis and climate drive low contents of clay and soil organic carbon, and Se air-borne inputs are low. The risk of inadequate Se intake by humans and animals in the region is high. This study can aid public policies addressing Se malnutrition in the study region and similar geopedological and climate settings worldwide.

Detection of Geochemical Element Assemblage Anomalies Using a Local Correlation Approach

As direct prospecting data, geochemical data play an important role in modelling prospect potential. Geochemical element assemblage anomalies are usually reflected by the correlation between elements. Correlation coefficients are computed from the values of two elements, which reflect only the correlation at a global level. Thus, the spatial details of the correlation structure are ignored. In fact, an element combination anomaly often exists in geological backgrounds, such as on a fault zone or within a lithological unit. This anomaly may cause some combination of anomalies that are submerged inside the overall area and thus cannot be effectively extracted. To address this problem, we propose a local correlation coefficient based on spatial neighbourhoods to reflect the global distribution of elements. In this method, the sampling area is first divided into a set of uniform grid cells. A moving window with a size of 3×3 is defined with an integer of 3 to represent the sampling unit. The local correlation in each unit is expressed by the Pearson correlation coefficient. The whole area is scanned by the moving window, which produces a correlation coefficient matrix, and the result is portrayed with a thermal diagram. The local correlation approach was tested on two selected geochemical soil survey sites in Xiao Mountain, Henan Province. The results show that the areas of high correlation are mainly distributed in the fault zone or the known mineral spots. Therefore, the local correlation method is effective in extracting geochemical element combination anomalies.

Geological Characteristics and Regional Prospecting Model of Wulanchongji Gold Orebody, Alxa Youqi, Inner Mongolia, China

Five gold deposits (mineralization) were found in the study area by means of geological mapping, soil geochemical survey and trough exploration engineering. The ore-bearing lithology is mainly metamorphic feldspar sandstone of the Upper Carboniferous Benbatu Formation, and the gold (mineralization) body is controlled by both structural factors and stratigraphic factors of the Upper Carboniferous Benbatu Formation. The genetic type is preliminary concluded to be volcanic hydrothermal type, and the metallogenic age is late Variscan. In this paper, by studying the geological characteristics and metallogenic geological conditions of the gold orebody in the area, a regional prospecting model has been established, which is of great significance to better guide the prospecting work of similar gold deposits in the area and the region.

Geological Characteristics and Prospecting Criteria of Senji Molybdenum Ore Body in Urad Houqi, Inner Mongolia, China

Geological Characteristics and Prospecting Indicators of Senji Molybdenum Ore Body in Urad Houqi, Inner Mongolia Based on geological mapping, soil geochemical survey, surface trough exploration and deep drilling verification and control, the Senji Molybdenum deposit was discovered. Geological characteristics of the molybdenum ore body are described. The host lithology of molybdenum ore body is mainly in the cataclastic carbonated black plagioclase gneiss of the second rock member of the Paleoproterozoic Baoyintu Group, followed by Early Carboniferous monzogranite. The genetic type of the deposit is preliminarily deduced to be a hydrothermal filling vein-type molybdenum deposit. The significance of this paper is to summarize the prospecting marks of the molybdenum ore body in this area, so as to further guide the exploration work in this area, and at the same time provide a useful reference for the exploration work of similar deposits in other areas.

EFFECTS OF LAND-USE CHANGES ON SOIL CHEMICAL PARAMETERS IN KAKAMEGA-NANDI FOREST COMPLEX

<p> </p><p><strong> </strong></p><p> </p><p><strong>Background. </strong>Carbon lost in form of carbon dioxide contributes to climate change corresponding to altered soil chemical properties and plant growth. Land-uses that minimize carbon loses are highly encouraged. Unfortunately, in the Kakamega-Nandi Forest Complex, the Kenyan government continues to promote shamba systems (now Plantation Establishment for Livelihood Improvement Scheme) where the forest adjacent communities are allocated bush land plots to provide land for small-scale agriculture, cash crop farming and planting of tree seedlings for a specified period of time inside the forest. <strong>Objective. </strong>This study analyzed six land-uses and their effect on the dynamics of soil chemical parameters using landsat images and recent soil geochemical surveys. <strong>Methodology. </strong>Land cover and vegetation changes were determined using a series of multispectral Landsat images. A total of seven sets of image datasets were downloaded from the Glovis web portal (<a href="http://glovis.usgs.gov/">http://glovis.usgs.gov/</a>) for the years 1985 to 2015 with the cloud cover ranging from 1 to 10% taken in the dry season. The land-use/cover classification scheme adopted was based on expertise knowledge and literature of land-use/cover activities. <strong>Results. </strong>The results show that (i) small-small agriculture has increased while bush-land has decreased between 1985 and 2015; (ii) smallholder farming of maize, pasture and sugarcane depleted soil organic carbon whereas perennial tree plantations (regenerated forests) increased soil carbon stocks; (iii) nitrogen decreased in all tested land-uses except in maize plantations; (iv) phosphorus remained unchanged in all land-uses, potassium significantly decreased in tea plantations while sugarcane and regenerated forests land-uses had decreased soil calcium stocks. <strong>Implications. </strong>The study provides evidence for the review of the shamba system. <strong>Conclusion. </strong>The study has shown that land-use changes through the application of the shamba system alter the dynamics of soil chemical parameters key among them are soil organic carbon, nitrogen and calcium. Cultivation of annual crops decreases soil carbon stocks which may lead to an influx of carbon dioxide in the atmosphere and increased vulnerability to climate change.</p>

Geological, geophysical, and geochemical characteristics of the Ban Kiouchep Cu–Pb–Ag deposit and its exploration significance in Northern Laos

The Simao–Indochina Basin is located between the Loei–Luang Prabang–Dien Bien Phu fold belt and the Jinghong–Nan-Uttaradit suture zone, composed of Mesozoic and Cenozoic red beds. It overlies the marine clastic rocks and volcanic sedimentary rocks of a Paleozoic back-arc foreland sequence. The Late Triassic Indosinian orogeny and subsequent superimposition and intracontinental shearing and structural superimposition may have facilitated the formation of various deposits in this basin, including hydrothermal, skarn, and porphyry types of mineralization. The Ban Kiouchep Cu–Pb–Ag deposit is a medium–low-temperature hydrothermal deposit that is largely controlled by faults and is hosted in carbonate rocks and volcanic (-sedimentary) rocks. The formation of this deposit includes a series of geological and metallogenic processes (i) neritic–littoral facies (volcanic-) sedimentation in a Late Paleozoic to Late Triassic back-arc foreland setting, (ii) Indosinian orogenic transformation, (iii) Mesozoic–Cenozoic tectonic-hydrothermal overprinting, and (iv) epigenetic oxidized leaching. The ore minerals are primarily malachite, azurite, and galena, followed by sphalerite, chalcocite, and chalcopyrite, with associated silver minerals. Using induced polarization (IP) geophysical surveys and soil geochemical surveys, large-scale and highly overlapping coincident anomalies and a mineralized zone at a scale of 100–110-m size (ore body I) was discovered in the area. Two anomalies, P1-C1 and P5-C4, with the best metallogenic conditions and the deepest extensions of the known ore bodies, were further selected as engineering verification targets. The two following verifying drill holes revealed Pb–Zn–Ag mineralization in the fault zone; however, no mineralized ore bodies consistent with the anomalies were found. The high background value of the Fe–Cu–Pb–Zn (Ag) elements, strong fracturing, and hydrothermal alteration, as well as later oxidized leaching with lateritization, resulted in in-situ dispersion and local secondary enrichment of the metallogenic elements. These may be the primary causes of the overlapping anomaly distribution along the strata and faults therein. Lateritic Ag mineralization has been also found in the area. The geological, geophysical, and geochemical characteristics and the prospecting are of great importance for further research and prospecting for other related deposits, for example, the VHMS, SEDEX, hydrothermal Cu polymetallic deposits and porphyry, skarn, epithermal, sediment-hosted/orogenic Au deposits, with lateritic Ag (Au) deposits in the Simao–Indochina Basin of Northern Laos.

Selenium-enriched soil mapping using airborne SASI images

Selenium (Se)isanimportanttraceelementthat is essential tohumanbeings. In the past, the Se concentration has mostly been obtained by field sampling and analysed under laboratory conditions. Unfortunately, this process is expensive, and the number of available samples is usually relatively small.A soil geochemical survey was conducted in conjunction with an airborne survey via hyperspectral remote sensing in the Chuangye Farm area, China. Twenty-five elements/oxides including Se were analysed in the samples, and the results showed that Se has a highly negative correlation with K. Using hyperspectral Shortwave Infrared Airborne Spectrographic Imager (SASI) data, the abundances of clay minerals were obtained through the sequential maximum angle convex cone (SMACC) classification operation. According to the abundances of clay minerals, the reflectance of clay minerals was obtained using the spectral retrieval method. Due to the correlation among K, Se, clay minerals and their spectral characteristics, a stepwise regression model was established using the results from the geochemical survey data and retrieved hyperspectral SASI data; then, the K and Se concentrations were predicted. The results of this study show that predicting the Se content in soil by using SASI images through the spectral retrieval of clay minerals in soil in conjunction with actual geochemical analysis results boasts a higher prediction accuracy than the use of the raw SASI images, and this prediction approach has been proven to be feasible.