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    Intelligent geoscience information mining and knowledge discovery using big data analytics: A case study of the Shangfanggou Mo (Fe) mine in Henan Province
    WANG Luofeng, WANG Gongwen, XU Wenhui, XU Senmin, HE Yaqing, WANG Chunyi, YANG Tao, ZHOU Xiaojiang, HUANG Leilei, ZUO Ling, MOU Nini, CAO Yi, LIU Zhifei, CHANG Yulin
    Earth Science Frontiers    2023, 30 (4): 317-334.   DOI: 10.13745/j.esf.sf.2022.2.85
    Abstract599)   HTML15)    PDF(pc) (8487KB)(6139)       Save

    Industry 4.0 of the 21st century has given birth to smart mines. The multidisciplinary datasets of smart mines-such as geology, exploration, mining, geometallurgy, environment and survey/map datasets-constitute big data of mines, and they play an important role for the rapid advancements of geoscience in areas of geoscience digitization and application of information/Al technology in geoscience. Taking the Shangfanggou Mo (Fe) mine, a 5G+ smart mine, in Henan Province as an example, using big data of mines, this paper carried out geoscience information mining to highlight emerging engineering research with integrated multidisciplinary approach. Innovative results and geological knowledge discoveries from this study are summarized as follows: (1) According to theories on porphyry-associated skarns and mineralogical approach to minera resources prospecting, using borehole datasets and large-scale open-pit mapping and microscopic identification analysis, a 3D temporo-spatial model of the identified key minerals and predicted minerals in the study area was established, and a NE trending ore-bearing fault section and a penetration-type ore-bearing section were discovered. (2) Using UAV remote sensing and ground hyperspectral short-wave/long-wave infrared techniques, more than 20 types of key altered minerals in the study area were delineated, and a 3D multi-parameter mineral model was constructed. (3) Using geochemical techniques such as XRF and in-situ microscopy, a rock dataset with matching hyperspectral interpretation was established, and a dual-matrix mapping software for useful/harmful elements of rocks/ores in the study area was developed. In addition, mathematical modeling combining traditional geostatistics (gauss simulation, kriging interpolation) with machine learning (deep learning) was realized, and the composition of ore blends used between March-April 2021 was identified and the cause of the resulting low recovery rate was clarified. (4) Based on process mineralogy practice in the study area, multi-stage, multi-type mineral processing datasets (>1800 data on quarterly/monthly/daily processing of rock powder, mud powder, concentrate, tailings, etc.) were used to develop rock/mineral powder testing techniques and analysis methods, and the types of refractory ores and harmful minerals in the Shangfanggou Mo mine were identified. The multivariate, multi-type datasets of mines have the “5V” (volume, variety, velocity, veracity, value) characteristics of big data. The accurate management control of dynamic correlation measurement/analysis and rapid/efficient evaluation of big data of mines is conducive to intelligent mining decision-making and improvement of economic benefit (recovery rate). Among them, high-precision multi-parameter 3D modeling can be applied not only to deep mining of geological, structural, alteration and mineralization information models of rocks/ores as well as reserve/resources verification, but also to facilitating 4D control on real-time mining of fourth generation industrial 5G+ mines, such as 3D visualization of geological and mineral resources prediction/evaluation/storage expansion, virtual simulation of “year-quarter-month-day” dynamic ore blending and mining, and real-time digital twin for mine beneficiation. The research results provide a reference for in-depth geoscience research on mineral exploration and mineral resources assessment in smart mines.

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    Overview of magmatic differentiation and anatexis: Insights into pegmatite genesis
    ZHOU Qifeng, QIN Kezhang, ZHU Liqun, ZHAO Junxing
    Earth Science Frontiers    2023, 30 (5): 26-39.   DOI: 10.13745/j.esf.sf.2023.5.8
    Abstract878)   HTML96)    PDF(pc) (3044KB)(4788)       Save

    The origin of granitic pegmatites is significant for the understanding of their formation processes and rare-metal metallogenesis. Granitic pegmatites are mainly formed by fractional crystallization of granitic magmas or by anatexis. In discussing pegmatite genesis, pegmatite classification and its mineral assemblage characteristics can provide the preliminary evidence, whilst parental granite plutons provide the final proof of origin. Studies have shown that granite pluton and its pegmatite swarm are nearly coeval, with less than 10 km apart in location and continuing to differentiate, and they have a common material source. To determine the degree of fractional crystallization and to decipher the formation process of granite magmas major element/trace element/REE/stable isotope Rayleigh fractional crystallization models have been used. Current evidences for an anatexis origin include regional metamorphic-tectonic events; metamorphism features; close spatial and chemical compositional relationships and consistent isotopic compositional relationships between pegmatites and metamorphic rocks; formations of unique mineral assemblages and mineral inclusions in pegmatites; and similar chemical components between the parental granite magma and partial melt. The following research approaches have been used to discuss the partial-melting process and melt-extraction history and to clarify the pegmatite-forming process via anatexis: determining protolith by elemental comparison, isotope tracing, and trace-element simulation; clarifying major melting model using Rb/Sr-Ba diagram; and determining the melting condition and melt production based on mineral composition of protolith and element partitioning between mineral and silicate melt. Researchers have found that rare-metal pegmatites mainly formed from extreme fractional crystallization of highly evolved granitic magmas and, in rare cases, from low-degree partial melting of fertile metasediments. Besides, rare-metal pegmatite swarm could be formed from magmatic differentiation without a parental pluton, or from further differentiation of anatectic granite. Future researches need to gain a deeper understanding of the partial melting and fractional crystallization controls on granitic magmas, explore the physical and chemical processes during the formation of granitic magmas—especially melt escaping and migration mechanisms and their affects on rare-metal enrichment, and establish petrogenetic discrimination criteria for granitic pegmatites.

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    Geophysical approaches to the exploration of lithium pegmatites and a case study in Koktohay
    HE Lanfang, LI Liang, SHEN Ping, WANG Sihao, LI Zhiyuan, ZHOU Nannan, CHEN Rujun, QIN Kezhang
    Earth Science Frontiers    2023, 30 (5): 244-254.   DOI: 10.13745/j.esf.sf.2023.5.14
    Abstract1026)   HTML49)    PDF(pc) (5404KB)(2971)       Save

    Lithium is a critical metal widely used in Li-ion batteries for energy storage. The demand for lithium resource in a low-carbon economy is immense and rapidly growing, where a jump between 2015 to 2050 is predicted by Science. Currently more than half of lithium production comes from pegmatite lithium deposits. However, due to similar rock property between pegmatites and granite, lithium pegmatite prospecting by geophysical methods has proven difficult. Nevertheless, with the advancements in instrumentation and method developments, geophysical approaches have become increasingly widely used in lithium exploration. In this paper we briefly review the status of lithium resource as strategic raw material, and discuss and summarize the art of geophysical exploration for pegmatite lithium deposits, including rock physics, space remote sensing, gravity and magnetic prospecting, and geoelectrical exploration. A case study of the Koktokay rare-metal pegmatite by audio-frequency magnetotelluric (AMT) method is presented. Pegmatites and leucogranites are characterized by low magnetic susceptibility, low density, low polarizability and high velocity, and the electrical resistivity of pegmatites is affected by hydrophilic minerals and can vary by several orders of magnitude. As the host schist and gneiss in comparison have higher magnetic susceptibility and density, regional gravity and magnetic data are often used to delineate granite bodies. Recent reports show that micro-gravity in some cases can be used to identify pegmatite in host granite. With relatively high resolution and penetration depth, geoelectrical exploration plays an important role in the exploration of concealed pegmatite lithium deposits. In Koktokay, the rock formation and rock mass in the mining district are generally characterized by high resistivity by AMT method, but many low resistivity anomalies are detected. Based on the known ore deposits and geological survey results, the low-resistivity anomalies most likely reflect hidden pegmatites and indicate a good rare-metal resource prospect in the southern Koktokay mining district.

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    Helium: Accumulation model, resource exploration and evaluation, and integrative evaluation of the entire industrial chain
    TAO Shizhen, WU Yiping, TAO Xiaowan, WANG Xiaobo, WANG Qing, CHEN Sheng, GAO Jianrong, WU Xiaozhi, LIU-SHEN Aoyi, SONG Lianteng, CHEN Rong, LI Qian, YANG Yiqing, CHEN Yue, CHEN Xiuyan, CHEN Yanyan, QI Wen
    Earth Science Frontiers    2024, 31 (1): 351-367.   DOI: 10.13745/j.esf.sf.2024.1.71
    Abstract1377)   HTML16)    PDF(pc) (4043KB)(2931)       Save

    China's helium industrial chain needs scientific and technological support, but there lack a systematic theoretical understanding of helium geology, along with the lacks of targeted helium resource evaluation methods and parameter selection standard, comprehensive accurate detection of helium content, helium prospecting methods, cost index system, as well as methodology for integrative evaluation of the entire helium industrial chain. To address these knowledge/technology gaps we developed a helium accumulation model and three key technologies for helium resource and asset evaluation, using interdisciplinary research methodology and experimental techniques involving geology, geochemistry, gravity-aeromagnetic-electrical-seismic, and investment and economics. Through detailed investigation of typical helium-rich gas reservoirs, combined with analysis of “helium-natural gas-water” phase equilibria and phase-potential coupling in underground fluids, we revealed three helium occurrences—water-dissolved, gas-dissolved, free-particle; three migration mechanisms—mass-flow, seepage, diffusion; and four dispersion-enrichment controlling factors—proximity to source, adjacent faults, low-pressure zone, high-location. We developed a theoretical framework for the understanding of helium geology, recognizing high-quality source, efficient migration, suitable gas-carrier are the three key controlling factors of effective helium accumulation. To overcome a series of challenges in helium detection, such as variable detection techniques, low accuracy, large discrepancies with foreign data, and no targeted resource evaluation methods, we developed a comprehensive, accurate detection technique for helium content, with helium source and content at the core, and established 10 resource evaluation methods under four categories, solving the technical bottleneck in helium resource classification and evaluation. A normalized gravity/magnetic downward extension scheme was created to address challenges in helium source-rock distribution, lithofacies identification, source-fault characterization, and reservoir evaluation. An intelligent identification technique for multi-scale faults based on deep learning and a simulation method for acoustic properties of gas reservoir under different helium contents were developed, laying the foundation of predicting source-rock distribution, characterizing source-faults, logging interpretation, and evaluating helium-bearing gas reservoirs. By establishing a multi-process helium control model for helium-rich gas zones and target optimization methodology, the problem of target optimization for helium-rich gas zones is solved. Facing the reality of helium deficiency in China, with the goal of promoting cost-effective investment in helium extraction equipment, we developed a methodology for integrative evaluation of the entire helium industrial chain by adopting response surface methodology to build a nonlinear regression model between optimization target and various main process parameters, which preliminarily addressed the technical demand for cost-effective helium extraction from natural gas. Results from this research provide effective support for China's long-term, safe, and large-scale utilization of its natural helium asset.

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    Soil screening levels in the United States and implication for soil evaluation in China
    WANG Xiaoyu, QU Yajing, ZHAO Wenhao, MA Jin
    Earth Science Frontiers    2024, 31 (2): 64-76.   DOI: 10.13745/j.esf.sf.2023.11.50
    Abstract724)   HTML16)    PDF(pc) (1829KB)(2815)       Save

    Soil evaluation guidelines are essential for soil evaluation and soil environmental protection. The United States (USA) was one of the developed countries first paid attention to contaminated sites protection and soil pollution control, and it has since developed fairly comprehensive guidelines such as the Soil Screening Guidance (SSG) for soil evaluation, whilst China is still in its infancy in this regard. In this paper we review research results on soil screening levels (SSLs) in the USA, focusing on the laws and regulations and technical specifications for soil protection and remediation, and discuss the methodology of SSL formulation based on five health hazard types: direct ingestion, dermal absorption, ingestion of contaminated groundwater, inhalation of outdoor volatiles/particulates and vapor intrusion. On this basis, we propose that researches on soil evaluation in China should be conducted based on soil environmental conditions in China, with emphasis on establishing regional and national soil parameter databases, standardizing national soil evaluation guidelines and carrying out combined research on soil and groundwater evaluation criteria, so as to provide a reference for formulating soil evaluation criteria in China.

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    Overview of magmatic-hydrothermal evolution of and rare element super enrichment in NYF pegmatites
    RAO Can, WANGWU Mengyu, WANG Qi, ZHANG Zhiqi, WU Runqiu
    Earth Science Frontiers    2023, 30 (5): 106-114.   DOI: 10.13745/j.esf.sf.2023.5.6
    Abstract423)   HTML20)    PDF(pc) (4067KB)(2765)       Save

    NYF pegmatites as an important strategic mineral resource have not been widely studied. Compared to LCT pegmatites, NYF pegmatites have poor internal structural zonation and regional zonation but contain large amounts of Nb, Y, F and other rare minerals. The geochemical characteristics of columbite-/mica-group minerals and tourmaline can accurately reveal the magmatic-hydrothermal evolutionary process and reflect the degree of internal differentiation of NYF pegmatites; whereas volatile components such as F, B, P and H2O not only affect the degree of internal differentiation of the pegmatites but also play a crucial role in the super enrichment of rare elements. The enrichment, migration and crystallization of rare elements take place through all stages of magmatic-hydrothermal evolution; and the mineralization of rare metals (Nb, Be, Rb, Zr, Th, U) and rare earths (Y, Ce, Sc, etc.) may occur in the highly evolved pegmatites. In future, alkaline rocks/granites should be key exploration targets for NYF pegmatites; and researches on NYF pegmatites should be strengthened to guide ore prospecting.

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    Aeolian deposits in the Yarlung Zangbo River basin, southern Tibetan Plateau: Spatial distribution, depositional model and environmental impact
    XIA Dunsheng, YANG Junhuai, WANG Shuyuan, LIU Xin, CHEN Zixuan, ZHAO Lai, NIU Xiaoyi, JIN Ming, GAO Fuyuan, LING Zhiyong, WANG Fei, LI Zaijun, WANG Xin, JIA Jia, YANG Shengli
    Earth Science Frontiers    2023, 30 (4): 229-244.   DOI: 10.13745/j.esf.sf.2022.9.7
    Abstract540)   HTML19)    PDF(pc) (8436KB)(2537)       Save

    Situated in the suture zone formed by the India-Euroasia collision, the Yarlung Zangbo River (YZR) basin in the southern Tibetan Plateau is a hotspot for Earth systems research, where Middle-Pleistocene aeolian deposits not only provide an important window into the history of climate change and atmospheric circulation in the Tibetan Plateau, but also help us to gain a deeper understanding of the link between tectonics, climate and landscapes in general. However, a systematic understanding of the distribution, depositional model, and environmental effects of aeolian sediments in this region is still lacking. Here, we construct a new atlas and a depositional model of aeolian sediments in the YZR basin based on extensive field investigation as well as laboratory analyses of typical sediment samples collected across the region, combined with existing research results. In general, aeolian sand and loess are distributed in patches and usually occur together. A close provenance relation between loess and nearby loose sediments such as sand dunes and river sands indicates that aeolian sediments cycle locally, hence they record spatial changes of regional climate; in contrast, the valley sediments not only receive dust from distant sources but also contribute dust materials to the world via upper-level westerly winds. Middle-Pleistocene aeolian dust activity in the YZR basin was controlled combinedly by tectonic movement and global climate change; whereas aeolian dust activity during the Holocene was relatively complex under the river valley environment, and regional climate change was generally influenced by the synergistic effect of the mid-latitude Westerlies and the Indian summer monsoon.

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    Research progress on zircon from pegmatites and insights into rare-metal mineralization—a review
    SUN Wenbo, LI Huan
    Earth Science Frontiers    2023, 30 (5): 171-184.   DOI: 10.13745/j.esf.sf.2023.5.2
    Abstract467)   HTML34)    PDF(pc) (4644KB)(2125)       Save

    With increasing global demand for rare metals rare-metal pegmatites have attracted much attention due to their widespread distribution and great metallogenic potentials. Zircon as an important accessory mineral in pegmatites is important for the understanding of pegmatite genesis regarding the ore-forming source material, fluid properties/evolution, and rare-metal enrichment mechanism. This paper summarizes the latest research progress on pegmatite-hosted zircons and insights into rare-metal mineralization in pegmatites. Recent studies show that pegmatite-hosted zircons have multiple origins and often undergo hydrothermal transformation, which result in complex zircon age spectrum, where rare-metal mineralization is related to older zircons. Geochemical anomalies of trace elements in zircons can indicate complex rare-metal mineralization in pegmatites, constrain magmatic evolution process and reveal ore-forming fluid properties. The REE tetrad effect is a special mode of rare-earth distribution in magmatic rocks. Such distribution mode also exist for pegmatite-hosted zircons revealing complex melt-fluid evolution. Hf-O isotopic composition of pegmatite-hosted zircons is highly variable where Hf isotopes are a good tracer for pegmatite source areas and oxygen for fluids. Pegmatite-hosted zircon is rich in fluid and mineral inclusions, thus future key research should focus on using fluid inclusion temperature measurement and composition analysis to delineate the magmatic evolution stages, using high-U zircons to track the source of U-rich fluids, and using zircon Li/Zr isotopes to reveal the ore-forming processes.

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    Developing structural control models for hydrothermal metallogenic systems: Theoretical and methodological principles and applications
    YANG Liqiang, YANG Wei, ZHANG Liang, GAO Xue, SHEN Shilong, WANG Sirui, XU Hantao, JIA Xiaochen, DENG Jun
    Earth Science Frontiers    2024, 31 (1): 239-266.   DOI: 10.13745/j.esf.sf.2024.1.40
    Abstract1883)   HTML51)    PDF(pc) (5137KB)(1905)       Save

    A defining feature of a hydrothermal metallogenic system (HMS) is strong structural control on ore mineralization. A systematic analysis of the geometry, kinematics, thermodynamics, and rheology of multiscale ore control structures is crucial for understanding the genesis of HMSs and for ore prospecting. The main challenges include: transitioning from static to multiscale spatiotemporal analysis of the 4D dynamical system involving ore-control structural frameworks, permeability structures, ore-forming fluid pathways, and mineralization deformation networks; identifying key influencing factors of fluid pathways that control ore deposition; and unraveling the mechanism of structure-fluid coupling control of ore formation and localization. This study presents the theoretical and methodological principles and application for developing structural control models for HMSs in the following aspects. (1) The theoretical core. It states that fluid, not structure, is at the core of a structural control model. Fluid flow and ore formation within a hydrothermal system are influenced by the fault zone architecture and permeability structure, where permeability, in linking fluid flow and fluid pressure variation, is key to understanding ore control structures. (2) Stress and pressure dynamics. It considers that differential stress and fluid pressure difference result in diverse combinations of ore control structures, while differences in regional stress field and host rock strength result in variations in mineralization type. (3) Growth of fluid pathways. It considers that fluid pathways initiate from isolated microfractures within the upstream host rocks of overpressured fluid reservoirs which evolve along the direction of the steepest pressure gradient to form new extended fractures through growth and interconnection. These extended fractures eventually interconnect to form fluid pathways. As ore deposition takes place during brief periods of high fluid flux when repeated fault sliding induces rapid changes in fluid pressure, flow velocity, and stress, rapid pressure release—caused by a disruption of dynamic equilibrium in the fluid system due to fluid pathways growth—is a key factor driving metal precipitation. (4) Integrated research. Methodology involves integrating macro and microscopic examination of ore control structures, integrating geological history and stress analysis, combining local and regional analyses, adopting shallow and deep perspectives, and employing a multidisciplinary, multiscale approach to study various ore-controlling factors. (5) Geological mapping. Methodology involves using structure-alteration-mineralization network mapping to characterize alteration-mineralization rock blocks in terms of geometric parameters for ore control structures (such as type, shape, size, occurrence, spacing), and performing quantitative analyses (such as topological analysis of hydrothermal vein-fracture systems, 3D geometric analysis of ore bodies) to determine ore-control structural frameworks and permeability structures and reveal the connectivity of mineralization deformation networks and their ore-forming potential. (6) Numerical modeling. Methodology involves developing geological models, selecting appropriate thermodynamic parameters and dynamic boundary conditions, and utilizing methods such as HCh and COMSOL to perform quantitative simulation of spatiotemporal variations in fluid flow, heat-mass transfer, stress deformation, and chemical reactions during ore formation. This is an effective approach to unveil the mechanism of ore formation controlled by structure-fluid coupling and ore localization pattern, predict ore-forming centers, and identify mineral exploration targets. Based on the above principles, this paper proposes a research methodology for model building, focusing on deriving metallogenic models and ore deposition patterns based on structure-fluid coupling control. Briefly, hydrothermal veins-fracture systems and structure-alteration-mineralization networks are selected as primary research subjects. Research methods include geometric description, kinematic assessment, rheological/dynamic analyses, and thermodynamic synthesis, seeking to delineate ore-control structural frameworks, identify mineralization centers, trace the developments of ore-forming fluid pathways and various mineralization styles, and reveal the spatiotemporal evolution patterns of permeability structures. Additionally, the causal relationship between tectonic reactivation and ore localization is explored. Finally, a metallogenic model based on structure-fluid coupling is constructed to support strategic mineral exploration. This research methodology was applied for mineral prediction in the Jiaojia gold field, Jiaodong Peninsula; its validity and effectiveness were tested and approved.

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    Petrogenesis of Paleoproterozoic granites in the Dondo area, northern Angola block: Geological response to the assembly of Columbia Supercontinent
    LIU Wei, ZHANG Hongrui, LUO Dike, JIA Pengfei, JIN Lijie, ZHOU Yonggang, LIANG Yunhan, WANG Zisheng, LI Chunjia
    Earth Science Frontiers    2024, 31 (4): 237-257.   DOI: 10.13745/j.esf.sf.2024.2.15
    Abstract1076)   HTML12)    PDF(pc) (7995KB)(1850)       Save

    The Paleoproterozoic Eburnean orogenic granites are widely exposed in the western part of Angola, offering an ideal setting to study the magmatism and tectonic evolution of the Angola Block. This paper presents systematic studies of petrology, petrogeochemistry, and zircon U-Pb geochronology on the exposed granites in the Dondo area, northern Angola Block. The results indicate that the emplacement ages of porphyritic biotite monzonite granite and biotite monzonite granite in the Dondo area are 1983.3±7.7 Ma and 1956.6±7.5 Ma, respectively, both products of middle Paleoproterozoic magmatic activity. The whole-rock samples are characterized by high SiO2, ALK, 10000Ga/Al, FeOT/(FeOT+MgO), and Zr+Y+Nb+Ce, and low MgO, TiO2, CaO, and P2O5. Trace elements are enriched in Rb, K, Th, U, Zr, and Hf, and depleted in Sr, Nb, Ta, P, and Ti. All samples are enriched in LREE and depleted in HREE, with no significant negative Eu anomaly. The crystallization temperature, calculated using zircon saturation thermometry, ranges from 757 to 889 ℃. Based on these geochemical characteristics, the granites in the Dondo area are classified as A2-type granite. Mineralogical and geochemical features suggest that the porphyritic biotite monzonite granite and biotite monzonite granite were generated by the mixing of crust-derived melts and mantle-derived mafic magma. The similar formation ages within analytical error, identical mineral assemblages, and consistent variations in major and trace elemental compositions indicate that their parental magma originated from a common magma chamber, with lithological differences resulting from melt extraction processes. It is proposed that the magma producing the potassium feldspar porphyry resided in the deep crust for an extended period, leading to stable crystallization of potassium feldspar, increased viscosity and density, and a frozen state of the magma. Subsequent thermal disturbance and volatile enrichment from mantle-derived magma injection rapidly reactivated the frozen magma chamber, resulting in crystal-melt separation. The extracted melt formed biotite monzonite granite, while magma mixed with pre-existing crystals formed porphyritic biotite monzonite granite. Combining regional and global tectonic evolution, it is suggested that the granites from the Dondo area formed in a post-collision tectonic environment between the São Francisco Craton and the Congo Craton. The Paleoproterozoic magmatic events in the Angola Block are likely responses to the Columbia Supercontinent assembly.

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    Toxicity thresholds (ECx) for Cr in soils and prediction models
    SUN Xiaoyi, WANG Meng, QIN Luyao, YU Lei, WANG Jing, CHEN Shibao
    Earth Science Frontiers    2024, 31 (2): 121-129.   DOI: 10.13745/j.esf.sf.2023.11.55
    Abstract633)   HTML4)    PDF(pc) (2958KB)(1747)       Save

    The lack of toxicology data is the main factor hindering the ecological risk assessment of Cr contamination in soils and the revision of soil environmental quality standards in China. In this study, we conduct toxicology tests on seven soil types (with different soil properties) in China, using earthworm biomass, cabbage biomass, and microbial matrix induced respiration (SIR) as measurement endpoints. We determined the effective concentration (ECx) values under different soil types based on the Log-logistic dose-effect relationship and low-dose stimulus effect function model. On this basis we developed predictive models for estimating toxicity thresholds of Cr under different soil properties. Chromium toxicity in earthworms, Chinese cabbage, and soil microorganisms under different soil types showed significant inhibitory effect with increased soil Cr concentrations, and the dose-response (D-R) relationship was clearly sigmoid in shape. Under different soil types, the EC10 values for soil microorganisms (SIR), earthworms, and Chinese cabbage ranged between 22.1-53.7, 65.0-137.2, and 82.1-220.2 mg/kg, respectively, and the EC50 values between 50.3-103.7, 103.9-369.0, and 159.9-441.9 mg/kg, respectively. The Cr toxicity thresholds for the tested species, from high to low, followed the order of Chinese cabbage>earthworms>soil microorganisms, with soil microorganisms being the most sensitive to Cr toxicity. Under low Cr concentrations (<112 mg/kg), the tested species showed significant hormesis effects, among which earthworms had a maximum hormesis between 102%-108% under different soil types, and Chinese cabbage between 105%-112%, while soil microorganisms showed relatively small effect at 104%. Chromium toxicity thresholds under different soil types can be well predicted based on soil pH and clay/CEC contents. The research results provide a scientific basis for the ecological risk assessment of Cr in soils and for the formulation and revision of environmental quality standards for Cr in soils.

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    Prospects for submarine hydrogen exploration and extraction technologies
    JIANG Zhaoxia, LI Sanzhong, SUO Yanhui, WU Lixin
    Earth Science Frontiers    2024, 31 (4): 183-190.   DOI: 10.13745/j.esf.sf.2024.6.10
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    In the current context of the dual-carbon policy, the national demand for clean energy, such as hydrogen, is growing significantly. Serpentinization of peridotite is one of the most widespread water-rock interactions on the seafloor, and hydrogen gas, a primary product of this process, serves as a crucial pathway for the formation of marine hydrogen energy. Therefore, the deep oceanic crust holds highly promising hydrogen energy reserves, representing a vital breakthrough for alleviating current dual-carbon pressures and driving the development of new productive capacities. However, global technologies for detecting and extracting marine hydrogen energy are still in their infancy, presenting a significant opportunity for future seafloor energy exploration and growth. This paper systematically reviews the formation principles and distribution characteristics of marine hydrogen energy, outlining potential detection technologies and extraction methods. We propose that comprehensive geophysical exploration methods, such as multibeam bathymetry, magnetic surveys, gravity measurements, and multi-component seismic exploration, hold promise for detecting potential hydrogen reservoirs on the seafloor. Additionally, methods like hydraulic fracturing and microwave heating could be utilized for extracting hydrogen from these reservoirs. However, due to the limited understanding of marine hydrogen energy and the unique challenges associated with hydrogen storage and transport, there is a pressing need to develop specialized detection and extraction technologies tailored to marine hydrogen energy. Advance layout in this direction will provide the necessary technical support for the exploitation and utilization of marine hydrogen energy and spur revolutionary breakthroughs in various technological fields.

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    Online monitoring of CO2 using IoT for assessment of leakage risks associated with geological sequestration
    MA Jianhua, LIU Jinfeng, ZHOU Yongzhang, ZHENG Yijun, LU Kefei, LIN Xingyu, WANG Hanyu, ZHANG Can
    Earth Science Frontiers    2024, 31 (4): 139-146.   DOI: 10.13745/j.esf.sf.2024.5.15
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    Geological sequestration can be used to reduce CO2 emission without much effect on economic growth. It has become an indispensable technical approach to achieving dual-carbon goals. However, geological sequestration carries significant environmental risks from CO2 leakage at storage sites. To ensure the safety and efficacy of carbon sequestration it is critical that potential leaks can be identified through continuous monitoring. In this regard, the Internet of Things (IoT) is ideal due to its large-scale, continuous monitoring, and intelligent analysis capabilities, yet this technology has not been widely implemented. This paper outlines the basis for sensor selection and sensor node deployment, proposes the design idea for underlying sensor technology, and establishes an IoT CO2 monitoring system for storage sites. Specifically, infrared CO2 sensor is selected as the primary sensor and laser CO2 sensor as the secondary sensor, along with FT-IR patrol monitoring; a combination of real-time optimization of mobile deployment, random deployment, and fixed deployment is used in sensor node deployment; a mix of cluster topology and mesh topology is used in high-risk areas, and star topology and tree topology are used in edge areas connected to the main area. As technology advances, sensor mass production and sensor miniaturization will lead to more efficient and scalable sensor networks, and IoT monitoring technology will play a crucial role in continuous monitoring of carbon storage sites.

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    Lithium isotope geochemistry—a review
    CHEN Yu, XU Fei, CHENG Hongfei, CHEN Xianzhe, WEN Hanjie
    Earth Science Frontiers    2023, 30 (5): 469-490.   DOI: 10.13745/j.esf.sf.2023.2.51
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    Lithium (Li) as a non-traditional stable isotope is a strategic and critical metal for the development of emerging industries. This review summarizes the geochemical properties of Li as well as its isotope distribution characteristics, analytical techniques, and fractionation mechanisms, and provides a comprehensive discussion on the latest research application of Li isotopes in plate subduction, crust-mantle material evolution, metallogenic mechanism, surface weathering, carbon cycle, and human activities. The relative mass difference between the two stable isotopes, 6Li and 7Li, can reach 17%. Significant Li isotopic fractionation occurs due to changes in environmental conditions (both physical and chemical) during tectonic evolution, and δ7Li can vary up to 60‰ between different reservoirs. Lithium stable isotopes have great potential for ore prospecting and geochemical tracing. Lithium as a lithophile element with strong fluid activity is widely distributed in the crust, where 7Li is more likely to enter the aqueous phase as tetravalent cations during fluid migration, which results in higher δ7Li in natural reservoirs. Lithium isotopic fractionation is significant at low temperature by forming secondary clay minerals, and it is less likely to occur at high temperature, where Li diffusivity and partition coefficient in minerals are the controlling factors. The rapid development of Li isotope detection techniques such as MC-ICP-MS and in-situ microanalysis greatly improves the accuracy of Li isotopic analysis (up to 0.2‰) and promotes use of Li isotopes in geoscience research. One example is in the study of dehydration and metasomatism during plate subduction. The preferential partitioning of 7Li in the aqueous phase affects Li isotopic composition of mantle wedge fluid and island arc lavas, where the absence of Li isotopic fractionation in the deep, high temperature environment causes low δ7Li values in the deep fluids, similar as in the subduction plate; whilst Li isotopic variations in mantle-derived xenoliths reflect different degrees of metasomatism. Li isotopes are also effectively used to study the genesis of ore deposits and ore prospecting. Lithium in salt brine are mainly sourced from weathering of Li-rich parent rocks and transported by bottom-up hydrothermal fluids, and the dissolution of sediments further promotes Li enrichment. The low δ7Li granopegmatite type lithium deposits mainly formed during late-stage magmatic differentiation. Rivers, rainwater, aerosols, and clay formation jointly affect Li isotopic fractionation via epigenetic effects. This review provides a reference for the geochemical application of Li stable isotopes. Lithium isotopic analysis can be more broadly applied in geological studies as the accuracy of isotopic measurements is further improved and the mechanism of Li isotopic fractionation under complex conditions is further clarified.

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    Odor measurement methods and prediction models: A review
    ZHU Fujie, QU Longze, LI Ping, WEI Wenxia, LI Peizhong, WANG Lifu, LI Benhang, WANG Jiao, REN Gengbo, WU Zhineng, MA Xiaodong
    Earth Science Frontiers    2024, 31 (2): 13-19.   DOI: 10.13745/j.esf.sf.2023.9.10
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    With the increasing awareness of environmental issues, odor pollution has been recognized as a typical environmental hazard. Odor pollution in China comes from a variety of sources and the cost of odor measurements is high. Currently a hot topic in odor pollution control is to develop odor prediction models based on easily measurable parameters to decrease the difficulty of odor measurement and control. This paper introduces the basic concept of odor pollution and summarizes and compares different odor classification standards and measurement methods. Research progress on odor prediction models is reviewed, including multiple linear regression commonly used to establish quantitative relationship between odor concentration/intensity and pollutant concentrations. There are obvious differences in the results obtained from different studies and models, and accurate odor threshold values are key to optimizing the models. Furthermore, as an environmental issue, atmospheric dispersion and emission rate of odor pollutants are discussed. Different atmospheric diffusion models have been used to predict odor diffusion in the atmosphere, however, different models require different basic data and knowledges, therefore it is important to choose an appropriate model based on the actual application scenario. Emission rate, as an important input parameter in atmospheric dispersion models, can also be measured using different methods and devices, but differences between the results are to be expected, and cross-validation is needed. This review provides scientific guidance for the identification and control of odor pollution.

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    Overview: A glimpse of the latest advances in artificial intelligence and big data geoscience research
    ZHOU Yongzhang, XIAO Fan
    Earth Science Frontiers    2024, 31 (4): 1-6.   DOI: 10.13745/j.esf.sf.2024.6.99
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    This special issue titled “Artificial Intelligence and Big Data Geoscience” consists of 17 papers covering topics such as knowledge graphs, deep learning-based image recognition, machine-readable expression of unstructured geological information, big graph data and community detection, association rule algorithms, 3D geological simulation and mineral prospecting, and the Internet of Things and online monitoring systems. A progressive multi-granularity training deep learning method is proposed for mineral image identification; the model achieves 86.5% accuracy on a commonly used dataset comprising 36 mineral types, increasing the accuracy of mineral identification. Knowledge related to porphyry copper ore in the Qinzhou-Hangzhou mineralization belt, South China, is collected using both primary and literature data sources, and Natural Language Processing (NLP) techniques are used to semantically correlate and reason over the knowledge graph, enabling automated knowledge extraction and reasoning. The association rule algorithm is used to analyze the correlation between trace elements and gold mineralization in major Carlin-type gold deposits in the “Golden Triangle” region of Yunnan-Guizhou-Guangxi provinces, China, and combined with the migration and enrichment law of elements to analyze the genetic mechanism of deposits. By builing a quantitative prospecting indicator method based on association rule algorithm, this study provides new ideas for establishing quantitative prospecting indicators for other types of deposits. In study of machine-readable expression of unstructured geological information and intelligent prediction of mineralization associated anomaly areas in Pangxidong District, western Guangdong, China, unstructured geological information such as stratigraphy, lithology and faults is processed by machine-readable conversion, and two machine learning algorithms—namely, One-Class Support Vector Machine and Auto-Encoder network—are applied to mine the geochemical test data of the stream sediment as well as the comprehensive geological information such as faults and stratigraphy, to extract the features of the mineralizing anomalies, and ultimately realize the intelligent circling of mineralizing anomalous areas. In study of networked monitoring of urban soil pollutants and visualized system based on microservice architecture, a system capable of real-time online monitoring, processing, and analyzing urban soil pollution data to enhance the timeliness of predictions and warnings is developed, where the integrated monitoring and data visualization system is based on the microservices framework Spring Cloud Alibaba. The above mentioned studies provide highly valuable application scenarios and research cases, reflecting to some extent the latest research advances in the field of artificial intelligence and big data geoscience in China, and are worthy of peer attention.

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    Characterization of gold distribution in sediments and prediction of gold prospectivity in Laos
    WANG Wei, WANG Xueqiu, ZHANG Bimin, LIU Dongsheng, LIU Hanliang, Sounthone LAOLO, Phomsylalai SOUKSAN, CHI Qinghua, ZHOU Jian, HAN Zhixuan
    Earth Science Frontiers    2025, 32 (1): 78-90.   DOI: 10.13745/j.esf.sf.2024.10.28
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    Under the Belt and Road initiative China and Laos have carried out national-scale 1∶1000000 geochemical mapping in Laos. This study marked the first national-scale geochemical study of gold, a dominant mineral species, in Laos, where the geochemical background and spatial distribution characteristics of gold in Laos were preliminarily investigated, and the geochemical anomaly and prospective areas of gold in Laos were delineated. A total of 2079 geochemical samples were collected and analyzed for gold element, using foam adsorption-graphite furnace atomic absorption spectrometry (FAS-GAAS), a high-precision analytical technique, and strict quality control measures. Gold contents in Laos aquatic sediments ranged between 0.10-913.70 ng/g, with mean and median (background) values of 2.44 and 1.00 ng/g, respectively. Gold occurred across the country with scattered distribution, mainly along extended large fractures affected by tectonic activities and magmatism. Using 85% quantile (1.99 ng/g) as the anomaly detecton limit, 17 gold anomaly areas were identified, with eight reaching a geochemical province scale (>1000 km2); seven prospective gold mineralization zones were classified according to anomaly identification, taking into consideration the spatial distribution of gold, geologic background, regional tectonics and mineral distribution. The results provide basic information for gold exploration in Laos and fill the gap of geochemical mapping for gold exploration in Laos.

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    Shale oil reservoir of the Palaeogene Shahejie Formation in the Dongpu Sag: Petrology and pore microstructural characteristics
    PENG Jun, SUN Ningliang, LU Kun, XU Yunlong, CHEN Faliang
    Earth Science Frontiers    2023, 30 (4): 128-141.   DOI: 10.13745/j.esf.sf.2022.10.15
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    Shale petrology and pore microstructures are key performance evaluation indicators for shale oil and gas reservoirs. In this study, the petrological and oil compositional characteristics of shale oil reservoir and reservoir lithofacies types, pore/fracture types and pore-throat distribution in the Shahejie Formation in the Dongpu Sag are investigated by core observation, thin section analysis, scanning electron microscopy, mercury injection-liquid nitrogen adsorption and microCT-guided 3D reconstruction methods. Results show that the shale oil reservoir contains mainly clay and carbonate minerals and some felsic minerals. The main lithofacies includes laminated limestone/clay stone/calcareous fine-grained mixed rocks/argillaceous fine-grained mixed rocks, and massive clay stone/dolomite. The reservoir pore space is mainly provided by a combination of intergranular/intragranular dissolution/clay mineral intergranular/organic pores. The microfractures can be divides into diagenetic and tectonic fractures, and the laminated limestone/calcareous fine-grained mixed rocks developed various high porosity pore spaces. Lithofacies and bedding structure are important factors influencing pore development and pore quality. Laminated rocks, except clay stone, possess large pore space and show good pore connectivity, relatively developed microfractures and high oil content and mobility, and laminated limestone is the most favorable lithofacies. These rocks are key shale oil exploration targets in the Dongpu Sag.

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    Spatiotemporal dynamics and control factors of vegetation cover in the Fuyang River Basin based on geographical detector model
    CHEN Kang, DING Yongkang, ZHANG Xiaochen
    Earth Science Frontiers    2023, 30 (5): 526-540.   DOI: 10.13745/j.esf.sf.2023.2.79
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    The Fuyang River—flows through Handan, Xingtai and Hengshui areas of Hebei Province as a tributary of the Ziya River, confluencing with the Hutuo River at Cangzhou—plays an important role in the eco-environment and economic development of the Fuyang River Basin. Based on the 2000-2020 monthly MOD13A1 (500 m) dataset, the spatiotemporal dynamics of regional vegetation cover was analyzed by unary linear regression and Hurst index methods, and Pearson correlation analysis between the normalized difference vegetation index (NDVI) and temperature/precipitation was performed. In combination with geographical analysis by geographical detector method, natural factors such as precipitation, temperature, vegetation type, soil type and elevation, and human factors such as land use type, population density and GDP were evaluated through statistical analysis for their impact on regional vegetation cover. Furthermore, control-factor detection, two-factor interaction detection and risk area detection were carried out. Ultimately, the impact of each control factor on NDVI and the optimal value of each control factor for vegetation growth are calculated, which provided a reference and basis for ecological protection and sustainable development in the region. The results showed that (1) the regional vegetation cover had an overall increasing trend between 2000-2020, and the NDVI, Slope index and Hurst index annual means were 0.76, 0.0005 and 0.48, respectively. According to spatial superposition analysis, the regional vegetation-cover changes were mainly attributed to man-made improvements. (2) There was a positive correlation between NDVI and precipitation annual means, while NDVI interannual trends were more closely related to precipitation than temperature. (3) The control factors were ranked according to their influence on NDVI as precipitation > population density > GDP > land use type > soil type > temperature > elevation > vegetation type. The first three factors, with q values greater than 0.2, were considered the main control factors of regional vegetation cover. (4) The impact of a two-factor combination was significantly higher than that of a single factor, showing a two-factor enhancement effect; the precipitation-population density combination, with a q value of 0.59, had the highest impact, while combinations of precipitation and other factors had dominant effects. (5) Based on risk area detection, areas with precipitation of 464.73-500.03 mm, temperature of 15.14-15.23 ℃, altitude of 3-133 m, population density of 551.36-2059.96 people·km-2, GDP of 1756.77-7507.15 yuan·km-2, and an eco-environment with cultivated vegetation, nursery soil and cultivated land, were most favorable for vegetation growth.

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    Spectral reflectance study of the Jing’erquan pegmatite lithium deposit, Xinjiang
    WANG Shanshan, ZHOU Kefa, BAI Yong, LU Xuechen, JIANG Guo
    Earth Science Frontiers    2023, 30 (5): 205-215.   DOI: 10.13745/j.esf.sf.2023.5.19
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    The widely distributed pegmatite lithium deposits are the main source of lithium for industrial applications in China. The Jing’erquan lithium deposit, Xinjiang, is the largest pegmatite lithium deposit in the eastern Tianshan orogenic belt of Central Asia with great rare-metal resource potential. In this study, spectral reflectance extending from 400 to 2500 nm are obtained for rock and mineral specimens from the Jing’erquan lithium deposit, using ASD portable field spectrometer. The spectral reflectance characteristics of granite, mineral-bearing pegmatites, simple pegmatites, muscovite, spodumene, lematolite, etc., are analyzed. The study show that the 1913 nm spectral band can be used as a key band to identify lithium-bearing pegmatites. Based on the spectral characteristics of rocks and minerals, lithium deposits are compared between Jing’erquan, eastern Tianshan, and western Altun and Dahongliutan, western Kunlun, Xinjiang, and Jiajika, Sichuan, which show that the characteristic absorption wavelengths for lithium-bearing pegmatites in the four deposits differ by 1-4 nm. This study provides a theoretical basis for remote sensing mapping and geological prospecting of pegmatite lithium deposits in general.

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