Key Laboratory of Geochemical Exploration

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Key Laboratory of Geochemical Exploration

China

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Liu X.,Chinese Academy of Geological Sciences | Liu X.,Key Laboratory of Geochemical Exploration | Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration | And 2 more authors.
Journal of Geochemical Exploration | Year: 2015

Catchment/floodplain sediment geochemical datasets from three continental-scale geochemical projects in Australia (AU), China (CH) and Europe (EU) were studied by comparing sample media, sample preparation, elements determined, analytical methods, detection limits and proportions of reportable values, and certified reference materials used. Twenty six elements (Ba, Ce, Co, Cr, Cu, Mo, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Zr, Al2O3, CaO, K2O, MgO, MnO, Na2O, P2O5, SiO2, Fe2O3 (total), TiO2) were considered comparable among the 35 determined by all three projects, according to the criteria for global comparability of elements proposed in this paper. The median concentrations of all elements (except Co, Y, Zr, SiO2 and TiO2) in the three datasets increase in the following order: AU


Xueqiu W.,China University of Geosciences | Xueqiu W.,Key Laboratory of Geochemical Exploration | Bimin Z.,Chinese Academy of Geological Sciences | Bimin Z.,Key Laboratory of Geochemical Exploration | And 8 more authors.
Ore Geology Reviews | Year: 2015

In recent years mineral exploration has concentrated on concealed deposits in regolith-covered terrains. In China, the regolith-covered landscapes mainly include desert windblown sand basins, desert peneplains, semi-arid grassland, loess plateaus, forestry land, alluvial plains and laterite terrains. These diverse regolith-covered areas represent geochemical challenges for mineral exploration in China. This paper provides an overview of recent progress on mechanisms of metal dispersion from the buried ore deposits through the transported cover to the surface and penetrating geochemical methods to detect the anomalies. Case studies show that, in arid and semi-arid desert sand-covered terrains, sampling of fine-fraction (-120mesh, <0.125mm) clay-rich horizon soil is cost-effective for regional geochemical surveys for sandstone-type uranium, gold, and base metal deposits. Fine-fraction sampling, selective-leaching and overburden drilling geochemical methods can effectively indicate the 210 gold ore body at Jinwozi goldfield. In alluvium-covered terrains, fine-grained soil sampling (-200mesh, <0.074mm) combined with selective leaching geochemistry shows clear ring-shaped anomalies of Cu and Ni over the Zhouan concealed Cu-Ni deposit. In laterite-covered terrains, the anomalies determined by the fine-fraction soils and selective leaching of absorbed metals on coatings of Fe-Mn oxides coincide well with the concealed deposit over the Yueyang ore deposits at the Zijin Au-Cu-Ag field. Nanoparticles of hexagonal crystals mainly native copper, gold and alloys of Cu-Fe, Cu-Fe-Mn, Cu-Ti, and Cu-Au were observed in gases, soils and ores using a transmission electron microscope (TEM). The findings imply that nanoparticles of gold and copper may migrate through the transported cover to the surface. Uranium is converted to uranyl ions [UO2 2+] under oxidizing conditions when migrating from ore bodies to the surface. The uranyl ions are absorbed on clay minerals, because clay layers have a net negative charge, which needs to be balanced by interlayer cations. Nanoparticles of Au and Cu and ion complexes of U are more readily absorbed onto fine fractions of soils containing clays, colloids, oxides and organic matters. Thus, fine-grained soils enriched with clays, oxides and colloids are useful media for regional geochemical surveys in regolith-covered terrains and in sedimentary basins. Fine-fraction soil sampling combined with selective leaching geochemistry is effective for finding concealed ore bodies in detailed surveys. Penetrating geochemistry at surface sampling provides cost-effective mineral exploration methods for delineation of regional and local targets in transported cover terrains. © 2015 Elsevier B.V.


Liu X.,Chinese Academy of Geological Sciences | Liu X.,Key Laboratory of Geochemical Exploration | Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration | And 2 more authors.
Journal of Geochemical Exploration | Year: 2015

Catchment/floodplain sediment geochemical datasets from three continental-scale geochemical projects in Australia (AU), China (CH) and Europe (EU) were studied by comparing sample media, sample preparation, elements determined, analytical methods, detection limits and proportions of reportable values, and certified reference materials used. Twenty six elements (Ba, Ce, Co, Cr, Cu, Mo, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Zr, Al2O3, CaO, K2O, MgO, MnO, Na2O, P2O5, SiO2, Fe2O3 (total), TiO2) were considered comparable among the 35 determined by all three projects, according to the criteria for global comparability of elements proposed in this paper. The median concentrations of all elements (except Co, Y, Zr, SiO2 and TiO2) in the three datasets increase in the following order: AU2O, MgO and Zn are generally greater than 2 (and up to 7), which could be explained partly by protracted weathering in Australia, and partly by the smaller grain size fraction analysed of the CH dataset (<1mm) compared to AU and EU (<2mm). In conclusion, a unified sample medium should be collected and unified sample preparation techniques should be followed. Key elements related to mineral resources and the environment should be determined and international or exchanged internal standard materials inserted in new national or global geochemical mapping projects in order to generate globally comparable datasets for establishing global geochemical baselines. © 2013 Elsevier B.V.


Yao W.,Chinese Academy of Geological Sciences | Yao W.,Key Laboratory of Geochemical Exploration | Xie X.,Chinese Academy of Geological Sciences | Xie X.,Key Laboratory of Geochemical Exploration | And 3 more authors.
Journal of Geochemical Exploration | Year: 2014

Systematic mapping of nearly all elements in the periodic table to cover the entire earth's surface is still a dream for the applied geochemists in the world. Chinese geochemists have been active in the implementation of Global Geochemical Mapping Program. In the past thirty years, a series of systematic geochemical mapping programs have been conducted in China. These programs have greatly contributed to the development of the concept and methodology for the Global Geochemical Mapping Programs, such as the proper sampling medium selection, analytical scheme development, reference material development and also for the establishment of the quality control system. Based on the new sampling concept and encouraging results obtained from the representative experiments conducted in China, a new outline for the Global Geochemical Mapping Program is forwarded. © 2013 Elsevier B.V.


Lin X.,Institute of Geophysical and Geochemical Exploration | Lin X.,Key Laboratory of Geochemical Exploration | Zhang B.,Institute of Geophysical and Geochemical Exploration | Zhang B.,Key Laboratory of Geochemical Exploration | And 2 more authors.
Geochemistry: Exploration, Environment, Analysis | Year: 2014

Delineation of vertical distribution patterns of elements in overburden over a concealed deposit is essential for determining potential upward migration mechanism of elements and for predicting undiscovered mineral deposits. The aim of this study is to identify the vertical distribution features of elements in the regolith over the Jinwozi gold field, NW China by using factor analysis (FA) and concentration- volume (C-V) fractal modeling based on the data-set generated from 70 overburden drilling boreholes. Firstly, the zones of different gold enrichment states were obtained by the C-V fractal method. Secondly, FA was utilized to define the mineralization-related element association. Finally, the C-V method was applied to the relevant association defined by FA. The results showed that: (1) the C-V fractal method distinguished four enrichment states determined by Au thresholds of 1.6, 7.9 and 39.9 ng/g and by factor scores of −1.14, 0.33 and 1.45; (2) the first factor that describes 41.5% of the common variance has positive loadings in Au, As, Sb and Mo; (3) the zones of both high Au contents and factor scores generally showed horizontally northeasterly distribution along the ductile-shearing alteration belt and vertically top-bottom symmetric distribution in the regolith over the deposit; (4) the rest of the zones determined by the C-V fractal model properly delineated the zones of low and high backgrounds and moderate Au enrichment; and (5) the moderately-enriched zones of the raw Au data are better than those of the factor scores, and the rest of the zones have the similar distributions. These results indicate that: (1) the distribution of elements in the regolith was the product of nonlinear natural processes resulting in an enrichment pattern at the surface over the deposit; and (2) the integration of FA and C-V fractal model is effective for the delineation of 3D geochemical patterns. © 2014, Geochemistry: Exploration, Environment, Analysis, All rights Reserved.


Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration | Wang X.,International Center on Global scale Geochemistry | Liu X.,Chinese Academy of Geological Sciences | And 19 more authors.
Journal of Geochemical Exploration | Year: 2015

The China Geochemical Baselines (CGB) project provides nation-wide catchment sediment/alluvial soil geochemical baseline data for 76 elements including Hg from 3382 top (0-25cm) and 3380 deep sediment/alluvial soil samples (under a depth of 100cm) at 3382 sampling sites, corresponding to a sampling density of about 1 site per 3000km2. Mercury was determined by cold vapour generation atomic fluorescence spectrometry (AFS) under strict quality control using field duplicates, standard reference materials and analytical replicate samples. The 25th percentile is at 13 and 11μg/kg in top and deep sediment/alluvial soil samples, respectively; these concentrations are close to the crustal abundance in China. The median Hg value is at 26 and 18μg/kg in top and deep sediment/alluvial soil samples, respectively; the 75th percentile is 56μg/kg in top and 36μg/kg in deep sediment/alluvial soil samples. Mercury concentrations at the 50th (26μgHg/kg) and 75th (56μgHg/kg) percentiles exhibit systematic enrichment in the near-surface material. The Hg distribution maps show distinct increasing trends from northern to southern and from western to eastern China, which are primarily related to the distribution of parent rocks, including rocks associated with mineral resources of Hg, Sb, Au, As, Pb-Zn, and climate, resulting in different soil types, as well as to population density with accompanying industrial development. Anomalous Hg concentrations in top sediment/alluvial soil samples above the 85th percentile (87μg/kg) occur mainly in south and south-west and sparsely in north and east China; they most likely have a dual origin, natural and human-induced, with the latter having a greater contribution because of the intense industrial activities, and particularly mercury emissions from Hg, Sb, As, Au, Pb-Zn mining, coal combustion, and production of batteries, fluorescent lamps, thermometers and cement. The spatial distribution map of Hg ratios of top to deep sediment/alluvial soil samples displays higher values, suggesting that top samples are most likely polluted from human activities in the highly populated urban areas of eastern China. About 6.86% and 3.52% of top and deep sediment/alluvial soil samples, respectively, have Hg concentrations higher than the soil contamination limit of 150μg/kg set by the National Environmental Standards for Heavy Metals of the People's Republic of China. © 2015 Elsevier B.V.


Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration | Zhang B.,Chinese Academy of Geological Sciences | Zhang B.,Key Laboratory of Geochemical Exploration | And 4 more authors.
Earth Science Frontiers | Year: 2014

The authors describe frontiers of exploration geochemical research fields from nanoscale to global-scale patterns. Geochemical exploration initiated research on chemical compositions of hand specimens and local primary geochemical halos in the early stage, focused on regional geochemical distribution since 1970s, and on global-scale geochemistry since 1990s. Into 2000s, geochemists initiated a better understanding of micro- and nano-scale mechanisms governing the laws of these macro-scale (local, regional and global) geochemical patterns. This paper centers on the latest progresses in the 3 research fields: (1) nano-scale insight into migration mechanism of elements, particularly focused on findings of nanometer crystals of copper and gold; (2) regional-scale geochemical exploration for sandstone-type uranium deposits in basins; (3) global-scale geochemical baselines and their relations with geological background, mineral resources, climate changes, and human activities.


Liu X.,Chinese Academy of Geological Sciences | Liu X.,Key Laboratory of Geochemical Exploration | Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration
Earth Science Frontiers | Year: 2014

The spatial distributions and changes of elements in the earth have been studied by global-scale geochemical mapping, providing basic datasets and maps for the sustainable development of resources and environment. This paper briefly describes the history of global-scale geochemical mapping, and gives an evaluation and comparison for the sampling and analytical programs of the six global-scale mapping projects conducted in the past 20 years in China, Europe, North America and Australia. Among these mapping projects only European FORGES project collected multi-media samples (soils, stream sediments, floodplain sediments, humus, stream water); the China Geochemical Baselines project collected samples from different geomorphic landscapes (soils in agricultural plain land, floodplain/overbank sediments in mountainous terrains, catchment sediments in desert terrains); and the other four projects (Australia NGSA, USA NASGLP, Chinese EGMON, European GEMAS) using uni-media sampling program, collected soil or floodplain/catchment sediments. The analytical methodology in China reaches international leading level: 78 elements can be determined; their detection limits meet the requirements for global-scale geochemical mapping; and the analytical quality is controlled by standard reference materials.


Liu B.,Chinese Academy of Geological Sciences | Liu B.,Key Laboratory of Geochemical Exploration | Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration
Earth Science Frontiers | Year: 2016

The Baishan porphyry Mo deposit is located in the Sanchakou-Baishan porphyry copper-molybednum belt, which is hosted in the eastern part of Kangguer-Huangshan ductile shear zone in eastern Tianshan, NW China. In this paper, SIMS U-Pb dating and in situ Hf isotope of zircons from the deep granite porphyry in Baishan deposit were systematically determined, so that we can constrain the petrogenesis and formation age of the granite porphyry emplaced in Baishan, and can reveal the geodynamical setting of the rock-forming process of Baishan porphyry Mo deposit. Zircon SIMS U-Pb dating indicates that the magmatic activities in Baishan occurred at 229.7±3.2 Ma. Combined with the molybdenite Re-Os isochron age (225-229 Ma) reported by previous researchers, it is concluded that mineralization of the Baishan porphyry Mo deposit occurred in Triassic which is the same period as that of the rock formation. In situ Hf isotopic analyses of zircons that had previously been dated by SIMS yielded positive εHf(t) values ranging from +8.3 to +12 and the crustal model age ranging from 556 Ma to 758 Ma. Combined with the regional geological evolutionary history and isotopic data in this paper, we propose that the deep granite porphyry in Baishan deposit was formed in an intracontinental extension setting in the Late Triassic and the magma might be originated by partial melting of a juvenile lower crust. © 2016, Editorial Office of Earth Science Frontiers. All right reserved.


Lin X.,Chinese Academy of Geological Sciences | Lin X.,Key Laboratory of Geochemical Exploration | Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration | And 4 more authors.
Journal of Geochemical Exploration | Year: 2014

The study of deep-penetrating geochemistry of arid desert terrains in the Jinwozi gold field, north-western China has generated a data set of multi-element geochemistry, characterised by high complexity and variability leading to difficulties in integration and interpretation. Three multivariate statistical methods, i.e., factor analysis (FA), hierarchical cluster analysis (HCA) and discriminant analysis (DA) were applied to a subgroup of the data set in order to define the element associations, to identify the anomalies and to classify the regolith samples. The geochemical patterns of arid desert terrains were thus interpreted with the aid of statistical techniques. The subgroup consists of Au, Ag, As, Hg, Cu, Mo, Sb and Zn concentrations of regolith samples collected from two traverse lines and five overburden boreholes. Two factors with eigenvalues greater than 1 extracted by FA account for approximately 81% of the total variance. Specifically, factor 1 explains 52% of the total variance and is highly loaded by a combination of Au-As-Hg-Ag. This combination could represent the major mineralisation and three anomalous sites have been determined. Two of which are located over the known deposit. Factor 2 explains 29% of the total variance and has positive loadings on Cu and Zn denoting the minor mineralisation and diagenesis. High positive scores of both factors could be considered as an indication of the mineralisation. Silver, As, Cu and Zn are the most effective indirect indicator elements in the Jinwozi. The HCA was then applied to the classification of samples taken from the five boreholes at the three anomalous sites. Three geochemically distinct clusters, named A1, A2 and A3, resulted from the HCA. Samples from cluster A1 with high concentrations of Au, Ag, As, Hg, Cu and Zn are highly-mineralised. In addition, samples from cluster A2 and A3 can be generally treated as non-mineralised. The DA confirmed the results obtained from the HCA. The spatial distribution of the clusters shows vertical symmetric distribution of highly-mineralised samples over the deposit. This confirms the effectiveness of the FA in delineation of the anomalies in the Jinwozi. The integration of the FA, HCA and DA proved to be an effective tool in the field of deep-penetrating geochemistry. © 2013 Elsevier B.V.

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