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Multi-element geochemical mapping in Southern China

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Zhizhong Cheng at Institute of Geophysical and Geochemical Exploration
Zhizhong Cheng
Xuejing Xie
Xuejing Xie
Xuejing Xie
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Wensheng Yao at Institute of Geophysical and Geochemical Exploration, CAGS, China
Wensheng Yao
  • Institute of Geophysical and Geochemical Exploration, CAGS, China
Jizhou Feng
Jizhou Feng
Jizhou Feng
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Abstract and Figures

The 76-element Geochemical Mapping (76 GEM) Project was undertaken in southwestern China in 2000 and in southeastern China in 2008. In this project, 5244 composite samples of stream sediment at a density of one composite sample for each 1:50,000-scale map sheet were prepared from sample archives of the China Regional Geochemistry-National Reconnaissance (RGNR) Project, which have been available since 1978. The 76 elements were analyzed by using inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). In the present study, a new quality-control method known as the visualized standard map method was applied to the results of the 76 GEM project. Mean value and background value, which indicate the average concentration of the 76 elements in southern China, were derived from statistical data. Moreover, geochemical maps were compiled to demonstrate the distribution of the 76 elements in southern China.
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Multi-element geochemical mapping in Southern China
Data
June 2015
Zhizhong Cheng · Xuejing Xie · Wensheng Yao · Jizhou Feng · Jindong Fang
... The first survey was completed in the mid to late 1980s (the early stage). The early-stage samples were not significantly disturbed by large-scale industrialisation and represent the geochemical background of the initial phase of industrialisation in the basin [12]. The second survey was completed in 2008-2010 (the late-stage). ...
... The analysis quality control procedures included: (1) insertion of 5 % sampling duplicates; (2) insertion of laboratory replicates; and (3) insertion of Standard Reference Materials [78,79]. The analytical scheme and quality monitoring system for the early-stage samples are described in detail by Cheng et al. [12]. The accuracy and precision of all elements met the given requirements [12]. ...
... The analytical scheme and quality monitoring system for the early-stage samples are described in detail by Cheng et al. [12]. The accuracy and precision of all elements met the given requirements [12]. The geochemical analysis data of the early-stage samples can be found in Table S1. ...
Spatial-temporal variation, source apportionment and risk assessment of lead in surface river sediments over ~20 years of rapid industrialisation in the Pearl River Basin, China
Article
  • Nov 2023
  • J HAZARD MATER
Lead (Pb) is a highly toxic element and is not essential to the human body. Lead pollution caused by human activities and a high geological background is considered a global environmental issue. According to the China Geochemical Baseline (CGB) project, the Pearl River Basin had the highest Pb content in alluvial sediments of 30 first-level basins in China. For this reason, it is of great significance to determine the temporal and spatial variations in Pb and their influencing factors in the Pearl River Basin. In this study, 956 stream sediment samples collected in the 1980 s (early stage) and 129 river sediment samples collected from 2008 to 2010 (late stage) were used to study the background value and spatial-temporal variation characteristics of Pb in river sediments in the Pearl River Basin. The Pb source apportionment and an ecological risk assessment were also carried out. The background value of Pb (36.2 mg·kg–1) in the river sediments of the Pearl River Basin was significantly higher than that in China (22.1 mg·kg–1). The parent rocks determine the Pb background in sediments and the high Pb background areas mainly comprised carbonate rocks and acid volcanic rocks. Over 20 years of rapid industrialisation, the average Pb increased from 43.3 to 68.3 mg·kg–1 in the Pearl River Basin. The BCR analysis revealed that Pb mainly existed in the reducible phase (48 % on average) and residue phase (42 % on average). The enrichment factor and geo-accumulation index indicated that the late-stage sediments experienced more Pb pollution than the early-stage sediments. However, the risk assessment code (RAC) showed that there was a low ecological risk of Pb in the late-stage sediments. The factor analysis results for the two rounds of data were significantly different. The Pb content in early-stage sediments was closely related to Al2O3 and Zr, while Pb in the late-stage sediments was mainly related to Zn, As, Sb, Au and Hg, indicating that the increase in Pb in the later samples was mainly influenced by human activities. The Pb isotope composition of the late-stage sediments confirmed that low Pb content was mainly controlled by natural sources, while high Pb content was significantly affected by anthropogenic sources. Combining the results of spatial-temporal variation, chemical speciation and source apportionment indicated that the rapid rise of Pb in late-stage sediments in certain areas could be attributed to mining and smelting activities during the process of industrialisation over 20 years. The anthropogenic exogenous Pb could be immobilised by Fe-Mn (hydro)oxides when it entered the soil, so although there was a high background the ecological risk of Pb in river sediments was low. In the future, Pb pollution control and remediation needs to be strengthened in the Pearl River Basin to avoid the outbreak of potential ecological risks linked to Pb.
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... Three general options have been proposed for determining regionalscale multi-element geochemical anomalies (e.g., Geranian and Carranza, 2022 and references therein), namely: (a) single-element geochemical anomalies integration (Cheng et al., 2014); (b) principal components analysis (PCA) of multi-element signature of mineralization (Sun et al., 2009); clustering to distinguish multi-element signature of mineralization (Templ et al., 2008). Yousefi et al. (2019Yousefi et al. ( , 2021 presented a new approach to the mineral prospectivity mapping and discussed a way to obtain better and more precise target generation and proposed the "Exploration Information System" (EIS) for translating mineral system models to mappable spatial proxies. ...
Principal components analysis and K-means clustering of till geochemical data: Mapping and targeting of prospective areas for lithium exploration in Västernorrland Region, Sweden
Article
  • Mar 2024
  • ORE GEOL REV
This is open access paper and you can download from the following link. https://www.sciencedirect.com/science/article/pii/S0169136824001355?via%3Dihub
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... To this end, rock, soil, and stream/overbank/floodplain sediment samples are among the most common sample media (e.g., Rose et al., 1979). Many countries (or continent) have carried out geochemical mapping studies at global/continental scale (e.g., Caritat and Grunsky, 2013;Chipres et al., 2008;Chiprés et al., 2009;De Vos et al., 2006;Reimann et al., 2014;Salminen et al., 2005;Smith et al., 2012Smith et al., , 2014Wang and the CGB Sampling Team, 2015;Woodruff et al., 2015;Xie and Cheng, 2001), national/regional scale (e.g., Ayari et al., 2022;Cheng et al., 2014;Reimann and de Caritat, 1998;Salminen and Tarvainen, 1997;Salomão et al., 2021;Wang et al., 2022;Xie et al., 2012), and also local scale (e.g., see examples from Rose et al., 1979). With the continuation and completion of these geochemical mapping projects, much information can be mined to find new mineral resources, evaluate environmental effect and quantify future changes, and rebuild surface processes, particularly for those under-explored and/or underresearched regions. ...
National-scale Geochemical Survey: Distribution of chemical elements in stream sediment of South and Central Asia
Article
  • Mar 2024
  • J GEOCHEM EXPLOR
This work was carried out as the Pakistani, Uzbekistani, Tajikistani, and Kyrgyzstani contribution to the National-scale Geochemical Survey of South and Central Asia (NGSSCA) project, the objective of which was to document and study the amounts and distribution of chemical elements in stream sediment of South and Central Asia where such national-scale geochemical mapping is launched for the first time. In the framework of the NGSSCA project deployed in Pakistan, Uzbekistan, Tajikistan, and Kyrgyzstan, 9237 stream sediment samples (<2 mm grain-size fraction in alpine desert and mountainous area) were collected at an average density of 1 sample site/100 km2, on the basis of a common stream sediment sampling protocol. The resultant compositional data sets and cartographic products will vastly benefit future mineral exploration activity, surficial (and even solid Earth) geochemical processes studies (e.g., chemical weathering), and environmental evaluation. Eight elements of economic interests (e.g., Ag, Sb, W, Mo, Li, Be, Cu, and Co) are selected to demonstrate their distribution pattern in stream sediment and the main controlling factors. It's concluded that the anomalies for the selected elements in the NGSSCA project can thus be directly linked to different geogenic sources, e.g., underlying bedrock, soil type, mineralization or ore deposits, and large-scale fault systems. Based on the results and the integrated anomaly maps, some new target areas for the corresponding metallic mineralization are predicted, which will provide a basis for further mineral exploration.
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... Mean values and background values, which indicate the average concentration of the 76 elements in southern China, were derived from statistical data. Moreover, geochemical maps were compiled to illustrate the distribution of the 76 elements in southern China (Cheng et al., 2014;Yao, Xie, Zhao, & Bai, 2014). A geochemistry and mineralogy study of soils collected from the upper 5 cm, the A horizon, and C horizon at 4857 sites across the United States was recently completed (Smith, Cannon, Woodruff, Solano, & Ellefsen, 2014;Smith et al., 2013); the data are available online for download, as are gridded contour maps for many minerals and chemical elements (http://mrdata.usgs. ...
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A Novel Method for Regional Prospecting Based on Modern 3D Graphics
Article
Full-text available
  • Mar 2024
During comprehensive regional prospecting evaluation and delineation of a prospecting target area, various types of data, including geological, geophysical, geochemical, and remote sensing, are usually integrated and visualized in a unified spatial environment, making it convenient for researchers to identify mineralization. To maximize the precision of spatial boundaries, the maps traditionally used in prospecting are predominantly in vector formats. However, with the rapid development of modern real-time 3D graphics and computer cartography technology, raster maps can now provide richer detail representation compared to traditional vector maps while still meeting the precision requirements. In this paper, we present a new GPU-based 3D visualization method for spatial data, specifically, two types of bitmap-based maps called dynamic geochemical maps (DGMs) and interactive geological maps (IGMs). A novel software system implementing this method was developed and has been applied in the exploration of the Zhunuo ore district, Tibet, showing large advantages over traditional vector maps.
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Estimation of heavy metal soil contamination distribution, hazard probability, and population at risk by machine learning prediction modeling in Guangxi, China
Article
  • Apr 2023
Due to superposition of diverse pollution sources, soil heavy metal concentrations have been detected to exceed the recommended maximum permissible levels in many areas of Guangxi province, China. However, the heavy metal contamination distribution, hazard probability, and population at risk of heavy metals in the entire Guangxi province remain largely unclear. In this study, machine learning prediction models with different standard risk values determined according to land use types were used to identify high-risk areas and estimate populations at risk of Cr and Ni based on 658 topsoil samples from Guangxi province, China. Our results showed that soil Cr and Ni contamination derived from carbonate rocks was relatively serious in Guangxi province, and that their co-enrichment during soil formation was associated with Fe and Mn oxides and alkaline soil environment. Our established model exhibited excellent performance in predicting contamination distribution (R2 > 0.85) and hazard probability (AUC>0.85). Pollution of Cr and Ni exhibited a pattern of decreasing gradually from the central-west areas to the surrounding areas with the polluted area (Igeo>0) of Cr and Ni accounting for approximately 24.46% and 29.24% of total area in Guangxi province, respectively, but only 10.4% and 8.51% of total area was classified as Cr and Ni high-risk regions. We estimated approximately 1.44 and 1.47 million people were potentially exposed to the risk of Cr and Ni contamination, which were mainly concentrated in the Nanning, Laibin, and Guigang. These regions are main heavily-populated agricultural regions in Guangxi, and thus heavy metal contamination localization and risk control in these regions are urgent and essential from the perspective of food safety.
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Spatial prediction and influencing factors identification of potential toxic element contamination in soil of different karst landform regions using integration model
Article
  • Mar 2023
  • CHEMOSPHERE
The prediction of contamination distribution of potentially toxic elements (PTEs) in soils of Guangxi province, China and the identification of their controlling factors pose great challenges due to diverse bedrock types, intense leaching and weathering, and discontinuous terrain distributions. Herein, we integrated the random forest (RF) and empirical Bayesian kriging (EBK) to interpret and predict complex PTEs contamination distribution from three different karst landform regions (fenglin, fengcong, isolated peak plain) in Guangxi province. The modeling results are compared with the commonly used ordinary kriging and regression-kriging. In this study, our developed RF-EBK model combines the advantages of the RF and EBK model to promote the prediction accurately and efficiently. In this study, it was shown that the integration RF-EBK model exhibited desirable for Cd and As concentrations, with R2 of 0.89 and 0.83, respectively. The average RMSE and MAE of integration RF-EBK model decreased by 39% and 44%, respectively, relative to the regression-kriging with the second highest accuracy. Furthermore, the modeling results showed that approximately 41.96% and 18.96% of total area was classified as Cd and As polluted and above regions (Igeo >0) in Guangxi province, respectively. Higher Cd concentration was observed in the soil of fenglin and fengcong regions than that in isolated peak plain region due to the secondary enrichment and parent rock inheritance, while the As concentration exhibited no significant difference among the three regions. The modeling results indicated that the elevated Cd concentration might be associated with soil CaO concentration and alkaline soil environment, whereas As concentration tended to be increased with the elevating Fe2O3 concentrations in weakly acidic soil environment. This result confirmed the applicability and effectiveness of integration model in predicting complex spatial patterns of soil PTEs and identifying their controlling factors.
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National Geochemical Survey of Australia: The Geochemical Atlas of Australia
Data
Full-text available
  • Jun 2011
From 2007 to 2009, the National Geochemical Survey of Australia (NGSA) project collected sediment samples from 1315 sites located in 1186 catchments (~10 % of which were sampled in duplicate) from across Australia. The total area covered by the survey is 6.174 million km2, or ~81% of Australia. The resulting average sampling density is 1 site per ~5200 km2. Catchment outlet sediments, in most cases similar to overbank sediments, were chosen as the sampling medium, with a near-surface sample (Top Outlet Sediment, TOS, from 0-10 cm below the surface) and a bottom sample (Bottom Outlet Sediment, BOS, between on average 60-80 cm below the surface) being collected. The sample sites were selected to be near outlets or spill points of large catchments, so that overbank sediments there could reasonably be assumed to represent well-mixed, fine-grained composite samples of all major rock and soil types present in the catchment. A number of parameters were recorded in the field, including GPS coordinates, and dry and moist Munsell® colour and field pH of the soil. The sampling sites were described and photographed, with all field data captured digitally for easy subsequent upload into databases. In the laboratory, the samples were air-dried, homogenised and split into an archive sample for future investigations and an analytical sample for immediate analysis. The latter was further split into a bulk subsample, a dry sieved <2 mm grain size fraction subsample and a dry sieved <75 μm grain size fraction subsample. The bulk subsample was analysed for electrical conductivity of 1:5 (soil:water) slurries (EC1:5), pH of 1:5 (soil:water) slurries (pH1:5) and grain size analysis using a laser particle size analyser. During 2009 to 2010, the coarse (<2 mm) and fine (<75 μm) fractions were analysed using a variety of analytical methods to determine (1) Total element content, (2) Aqua Regia soluble element content, and (3) Mobile Metal Ion (MMI™) element content (only done on the TOS coarse subsamples). Thus, with two depths sampled, two grain size fractions separated, and three analytical methods applied, up to nine element determinations were obtained per sampling site. This data is collated in spreadsheets and graphically represented as a series of maps; the latter available in this report and both available digitally from the project website (www.ga.gov.au/ngsa). The present report is a compilation of 529 geochemical maps that result from the National Geochemical Survey of Australia. These constitute the first continental-scale series of geochemical maps based on internally consistent, state-of-the-art data pertaining to the same sampling medium collected, prepared and analysed in a uniform and well documented manner and over a short time period (four years). Interpretations of the data and maps will be published separately. The geochemical maps can be used for better understanding the accumulation, mobility and significance of chemical elements in the near-surface environment of Australia. It is expected that they will provide a new, additional pre-competitive dataset for the energy and mineral resource exploration industry, which should help prioritise areas for further exploration investment and thus reduce risk. Further, it is also likely that some of the geochemical maps will find use in other disciplines related to natural resource management and environmental monitoring.
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Regional geochemical exploration in China: From 1999 to 2009
Article
  • Apr 2012
Regional geochemical exploration in China changed greatly from 1999 to 2009. Regional geochemical exploration methods and techniques as well as mineral resources potential assessment have been deliberately studied and remarkable progress has been achieved under the guidance of geochemical theory. The principle of regional geochemical exploration methods and techniques developed aims at demonstrating the primary state of geochemical distribution in the highest degree. Selection of sampling media suitable for landscape and surficial geochemical condition is the key problem for regional geochemical survey. Samples collected should reflect the information of geology and mineralization, and hence weathered material of rocks is usually selected as sampling media. Efforts have also been made to collect the same material over the whole country. The established methods for mineral resources potential assessment and quantitative mineralization prognosis based on the theory of geochemical zoning have promoted the exploration geochemistry from pure methods to a theoretical level for steering mineral prospecting. The main achievements are as follows: systematic methods and techniques of national regional geochemical exploration have been established; analytical process and its quality are strictly controlled; Several geochemical atlases have been published based on accurate geochemical data, which can exacdy reveal geological setting and anomalous characteristics; regional geochemical data and its information have been studied profoundly and applied widely; the methodology system and working procedure from regional, reconnaissance to detailed exploration have been established for resource survey, assessment and prognosis. Regional geochemical exploration has been supporting mineral survey in China for a long period, acting as a forerunner of all geological work. It is certain that regional geochemical data will play an important role in new discovery, new understanding and new viewpoints of basic geology, mineralization regularity, and great geological events with the compilation of new geochemical maps covering various regions and the whole country. All this will have great influence on exploration geochemistry and geological work in China.
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Canada's National Geochemical Reconnaissance programme
Article
  • Jan 1991
National Geochemical Reconnaissance (NGR) stream- and lake-sediment and water surveys have been carried out by the Geological Survey of Canada since the early 1970s. These surveys provide a systematic coast-to-coast geochemical database. Areal coverage to 1990 amounted to approximately 2 100 000km2, representing 180 000 sites. Although the data have applications in resource evaluation, environmental studies, etc, their prime utilization is in aiding and stimulating mineral exploration. Excess sediment material that is not required for the initial analytical determinations has been stored for future use. Reanalysis of these samples by instrumental neutron activation analysis (INAA) provides usable data for a large number of elements (up to 20 new elements). -from Authors
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