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    2023, Volume 30 Issue 5
    25 September 2023
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    Geological features and formation mechanism of pegmatite-type rare-metal deposits in the Renli orefield, northern Hunan, China—an overview
    LI Jiankang, LI Peng, HUANG Zhibiao, ZHOU Fangchun, ZHANG Liping, HUANG Xiaoqiang
    2023, 30(5): 1-25. 
    DOI: 10.13745/j.esf.sf.2023.5.24

    Abstract ( 254 )   HTML ( 50 )   PDF (22668KB) ( 558 )  

    The Renli orefield in northern Hunan is a newly discovered pegmatite Li-Ta-Nb orefield in eastern China. It is located in the middle Jiangnan orogenic belt and consists mainly the Renli Nb-Ta-Be deposit, Yongxiang-Chuanziyuan Li-Be-Nb-Ta deposit and Huangbaishan Li-Be-Nb-Ta deposit. Pegmatite dikes in the northern orefield distribute along the southwestern margin of the Mufushan complex, forming distinct pegmatite zonation. Outwards from the complex, the pegmatite types are divided into microcline, microcline albite, albite and albite spodumene. Among the pegmatite dikes, Renli No.5 is the largest Nb-Ta ore body, which exhibits two-stage magmatic-hydrothermal mineralization characteristics; Yongxiang-Chuanziyuan No.206 is the largest spodumene dike in the area, where spodumene occurs mostly as pseudomorph due to strong late-stage metasomatism; and Huangbaishan No.603 is a newly discovered spodumene dike characterized by high-grade Li2O and weak metasomatism. Hydrothermal fluid played an important role in the rare-metal mineralization of Renli No.5, which is evidenced by the occurrence of quartz-hosted fluid inclusions. Fluid inclusion microthermometry reveals the Renli No.5 core formed at ~550 ℃ and ~350 MPa. According to existing data, the Renli orefield formed during the Yanshanian intracontinental orogeny (~130 Ma). The data show that during intracontinental orogeny granitic melts formed from basement rocks, i.e. the anatexis of the Neoproterozoic Lengjiaxi Group; then during multi-stage granitoid intrusion the late-stage two-mica granitic melts fractionated into pegmatite-forming melt; finally the hydrothermal metasomatism resulted in Nb and Ta enrichment and Li depletion in pegmatites. Thus, rare-metal mineralization in pegmatites in the Renli orefield can be characterized by metapelite anatexis during intracontinental orogeny, granitic magma differentiation, and two-stage magmatic-hydrothermal mineralization.

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    Overview of magmatic differentiation and anatexis: Insights into pegmatite genesis
    ZHOU Qifeng, QIN Kezhang, ZHU Liqun, ZHAO Junxing
    2023, 30(5): 26-39. 
    DOI: 10.13745/j.esf.sf.2023.5.8

    Abstract ( 382 )   HTML ( 67 )   PDF (3044KB) ( 829 )  

    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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    Mineralogical and chronological characteristics of the Huoyangou pegmatite Sn(Nb-Ta) deposit in Guanpo, eastern Qinling
    CHEN Lei, NIE Xiao, LIU Kai, PANG Xuyong, ZHANG Yingli
    2023, 30(5): 40-58. 
    DOI: 10.13745/j.esf.sf.2023.5.13

    Abstract ( 160 )   HTML ( 25 )   PDF (10203KB) ( 347 )  

    East Qinling is an important pegmatite mining area and Li-Be-Nb-Ta-U pegmatite belt in China. The mineralization of the Huoyangou Sn(Nb-Ta) deposit is unique to this region. This study investigates the mineralogy, zircon/cassiterite U-Pb geochronology, and Hf isotope of the Huoyangou pegmatite to clarify the rare-metal occurrence in and the formation epoch of the Sn(Nb-Ta) deposit. The genetic relationship between the ore-bearing pegmatites and Paleozoic granites in the region is then discussed to provide a basis for the mineralization of pegmatite-hosted rare metals in East Qinling. The Huoyangou pegmatite is composed of feldspars (mainly oligoclase, orthoclase), micas (mainly Fe-rich biotite, Muscovite), apatite (mainly fluorapatite), and tourmaline (mainly schorlite). The pegmatite is weakly differentiated compared to Li/Be pegmatites in the area, indicated by its weak zonal texture and the composition of micas and columbite-group minerals. The zircon U-Pb age ((424±2.5) Ma) and cassiterite U-Pb ages ((420.1±2.4) Ma and (420.6±3.2) Ma) for the pegmatite indicate its diagenetic and formation age is between 424-420 Ma, which is consistent with the formation age of rare-metal/uranium deposits in East Qinling. The zircon εHf(t) value (-5.8--4.16) and the two-stage model age (2341-2194 Ma) indicate the pegmatite is sourced from Proterozoic crust. This suggests that East Qinling pegmatites are similar to regional Late Silurian peraluminous magmas but different from the Paleozoic Huichizi pluton in terms of their source areas. Therefore, there may be no direct genetic relationship between East Qinling pegmatites and the Huichizi pluton. The Huoyangou Sn(Nb-Ta) deposit enriches the rare-metal mineralization types in East Qinling pegmatites and demonstrates great Sn resource potential in East Qinling.

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    Genesis of and uranium mineralization in leucogranite, Rossing, Namibia
    CHEN Xu, FAN Honghai, CHEN Donghuan, CHEN Jinyong, WANG Shengyun
    2023, 30(5): 59-73. 
    DOI: 10.13745/j.esf.sf.2023.5.10

    Abstract ( 164 )   HTML ( 14 )   PDF (5353KB) ( 245 )  

    The multiphase leucogranite of Rossing can be subdivided into six types, types A-F, but only types D and E form leucogranite uranium deposits. Trace element and Pb isotopic analyses show that the Rossing leucogranite has the characteristics of mixed crustal source, and the two-stage Nd model ages suggest the highly radioactive pre-Damara basement is the source area. The biotite electron probe data show that biotite in type D leucogranite has higher fluorine content compared to types A-C and F, and type D obviously has higher Nb/Ta contents. Types A-C and F leucogranite show a negative correlation between Ba content and Rb/Sr ratio, consistent with muscovite dehydration melting; whilst types D and E show a more complex relationship consistent with biotite dehydration melting. The Rossing area experiences four deformation stages (D1-D4), where the emplacement of types A-C leucogranites occurs no later than D3 while types D and E coincide with D4. The stress transformation during D4 changes the mode of anatexis in the ancient basement from muscovite to biotite melting, and the biotite melt provides fluoride ion, a uranium mineralizer. Therefore, the heterogeneous melting of the ancient basement is the cause of differential uranium enrichment in leucogranite of different phases. The Rossing leucogranite experiences strong crystallization differentiation, where the resulting crystalline minerals are mainly potassium feldspar, biotite, apatite, ilmenite and monazite. The fractional crystallization of biotite may cause uranium depletion, which is unfavorable to the mineralization of residual magma; whereas the fractional crystallization of K-feldspar, ilmenite and monazite is beneficial to the enrichment of uranium and formation of uraninite.

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    Early Miocene leucogranitic magmatism in Cuonadong, southern Tibet: Constraints from whole-rock geochemical and mineralogical characteristics
    HUANG Chunmei, LI Guangming, FU Jiangang, LIANG Wei, ZHANG Zhi, WANG Yiyun
    2023, 30(5): 74-92. 
    DOI: 10.13745/j.esf.sf.2023.5.18

    Abstract ( 141 )   HTML ( 22 )   PDF (15651KB) ( 390 )  

    In order to better understand the petrogensis of Himalayan leucogranites and its role in the mineralization of rare metals, we performed whole-rock major and trace element, monazite age and trace element, and main mineral composition analyses of weakly oriented two-mica granite and garnet-bearing muscovite granite in the Cuonadong Be-W-Sn polymetallic deposit in eastern Himalayas. Results show the Cuonadong two-mica and muscovite granites are formed during the same magmatic event and dated respectively to (20.1±0.3) Ma and (20.7±0.2) Ma. Whole-rock geochemical analysis shows the granites are rich in Si/Al, and monazite and the muscovite granite both exhibit REE tetrad effect. According to mineral analysis, plagioclase in the muscovite granite is more sodic, and the muscovite granite has higher FeO, MnO and F contents and higher spessartine content compared to the two-mica granite. These characteristics suggest the muscovite granite is more evolved and likely formed from highly evolved interstitial melt/fluid within the magmatic crystal mush, while the two-mica granite likely formed from the residual melt. Early (~20 Ma) differentiation of leucogranites in the Cuonadong dome promoted the initial enrichment of ore-forming elements such as Be and Sn, which is the key to late mineralization.

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    Coupling relationship between the stability of Li/Be complexes and Li/Be differential enrichment in granitic pegmatites—an experimental study
    HONG Tao, ZHAI Mingguo, WANG Yuejun, LIU Xingcheng, XU Xingwang, GAO Jun, HU Mingxi, MA Jing
    2023, 30(5): 93-105. 
    DOI: 10.13745/j.esf.sf.2023.5.3

    Abstract ( 100 )   HTML ( 7 )   PDF (3303KB) ( 272 )  

    Pegmatite lithium (Li)-beryllium (Be) deposits are an important type of strategic Li-Be deposit. However, anatexis, on one hand, only produces a small amount of pegmatite-forming melts while Li/Be extraction efficiency for anatectic pegmatites is low; on the other hand, it is still controversial whether magmatic fractional crystallization results in high Li/Be enrichment in pegmatites and increased extraction efficiency. With the observation of fluid immiscibility in Li/Be-rich silica melt, it suggested that melt-fluid immiscibility may also lead to pegmatite formation. Current studies on the pegmatite Li-Be mineralization processes during the melt-fluid phase mainly focus on the whole-rock geochemical characteristics of granitic pegmatites, the in-situ geochemical changes of the rock-forming minerals (mica, quartz, feldspar, etc.) and ore minerals (beryl, etc.), and the mineralogical and geochemical characteristics of melt/fluid inclusions in petrogenic minerals, ore minerals, and accessory minerals (garnet, etc.). So far no obvious correlation has been found between the depositional age and the types of melt/fluid inclusions. To understand the mechanism of abnormal Li/Be enrichments in pegmatites it is key to study the distribution and stability of Li/Be complexes during the melt-fluid phase, however, the former study is scarce and the latter non-existent. In this study we investigated the effects of pH and calcium/aluminum additions on the stability of Li/Be complexes. We found that (1) the stability of Be complex was more affected by pH compared to Li complex; (2) under constant pH, the addition of aluminum promoted Be but hindered Li precipitations; and (3) the addition of calcium had less effect on Li than on Be precipitations. Future high-temperature, high-pressure experimental simulation studies should further enhance our understanding of the Li/Be enrichment processes and provide a geochemical basis for new Li/Be mineralization models based on the stability of Li/Be complexes.

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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
    2023, 30(5): 106-114. 
    DOI: 10.13745/j.esf.sf.2023.5.6

    Abstract ( 123 )   HTML ( 15 )   PDF (4067KB) ( 397 )  

    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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    Geochemical analysis of apatite and columbite-group minerals of beryl-columbite pegmatites in Ningshan, southern Qinling orogen, China
    NIE Xiao, CHEN Lei, GUO Xianqing, YU Tao, WANG Zongqi
    2023, 30(5): 115-133. 
    DOI: 10.13745/j.esf.sf.2023.5.11

    Abstract ( 107 )   HTML ( 10 )   PDF (14718KB) ( 293 )  

    The Ningshan pegmatite district is locate at the outer contact zone on the south side of the Ningshan granitoid batholith. It is one of the three major pegmatite districts in the Qinling orogenic belt with numerous Rb-Be-Nb-Ta pegmatite deposits. This study investigates the mineralogy of beryl-columbite pegmatites by scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) methods, and determines the U-Pb ages for columbite and uraninite. The apatite (Ap) and columbite-group minerals (CGM) of the Ningshan pegmatites can each be divided into two types according to their chemical composition and mineral structural characteristics. Type I apatite (Ap-I) has relatively low Mn (MnO, 0.02%-2.27%)/Cl (0%-0.06%) contents, while type II (Ap-II) has high Mn (MnO, 14.51%-19.12%)/Cl (0.12%-0.16%) contents. Type I columbite-group minerals (CGM-I) is classified as columbite-(Fe) and type II (CGM-II) as columbite-(Fe) to tantalite-(Fe) on the classification diagram. Combining mineral composition and metasomatism characteristics, we consider that type I minerals are formed by magmatic fractional crystallization, while type II are related closely to fluid activities. The U-Pb age for CGM-I ((206.3±1.5) Ma) represents the emplacement age of pegmatites; while in situ Nd isotopic analysis suggests that Ap-I (εNd, -4.3 to -2.5) is genetically associated with Late-Triassic quartz monzonite and monzonite granite in the Ningshan batholith. The above results suggest that the Ningshan beryl-columbite pegmatites experienced multi-stage fluid activities. The U-Pb age proximity between secondary uraninite ((199.2±1.5) Ma) and CGM-I implies that early-stage fluid activities are closely related to magma evolution-likely to the exsolution of residual pegmatite-forming fluids during the magmatic to hydrothermal transition. Whilst a mixing of late-stage fluids with host-rock derived external fluids is indicated by the local high residual-Mn content in CGM-II and the high Mn/Cl contents in Ap-II.

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    Mineralogical characteristics of columbite group minerals and its implications for magmatic-hydrothermal transition in the Gabo lithium deposit, Himalayan metallogenic belt
    FU Jiangang, LI Guangming, GUO Weikang, ZHANG Hai, ZHANG Linkui, DONG Suiliang, ZHOU Limin, LI Yingxu, JIAO Yanjie, SHI Hongzhao
    2023, 30(5): 134-150. 
    DOI: 10.13745/j.esf.sf.2023.5.16

    Abstract ( 91 )   HTML ( 14 )   PDF (28003KB) ( 341 )  

    The newly discovered Gabo lithium deposit in the northwestern Kulagangri Dome, eastern Himalayan metallogenic belt, contains spodumene pegmatite hosted in marbles of the dome's detachment system, where lithium, beryllium, niobium and tantalum are the dominant ore-forming elements. In this paper, columbite-group minerals (CGM) in spodumene pegmatite dikes are investigated through detailed mineralogical analysis, including electron scanning microscopy (ESM) with backscattered electron imaging (BSE) and energy dispersive spectroscopy (EDS) elemental analysis. The structure of CGM in spodumene pegmatite is highly complex, featuring normal zoning, reverse zoning and rhythmic-ring zoning structures and complex texture, which reveal a three-stage formation and evolutionary process of spodumene pegmatite in the Gabo lithium deposit. The first stage, corresponding to the late orthomagmatic stage, forms the Nb, Fe-enriched CGM crystal core from residual peraluminous granitic melt, without clear zoning structures. The second stage, corresponding to the early stage of magmatic-hydrothermal transition, develops the zoning structures characterized by periodic changes of Nb/Ta/Fe/Mn contents. And the third stage, corresponding to the late stage of magmatic-hydrothermal transition, forms the complex mineral texture via extensive metasomatism. These results show that the mineral structure of CGM can be used to reveal the formation and magmatic-hydrothermal evolution of spodumene pegmatite.

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    Research progress on the mechanism for the formation of Nb-Ta deposits by fractionation and enrichment and method development for columbite-tantalite analysis—a review
    YANG Shuang, WANG Rui
    2023, 30(5): 151-170. 
    DOI: 10.13745/j.esf.sf.2023.5.15

    Abstract ( 186 )   HTML ( 16 )   PDF (5691KB) ( 307 )  

    Rare metals niobium and tantalum are irreplaceable in many fields of human society due to their high melting point, high density, high-temperature resistance, superconductivity and other excellent properties. They are also strategic resources the world has attached great importance to in the last 20 years and beyond. It is very important to understand Nb-Ta fractionation and enrichment in different magmatic systems and the metallogenesis of different types of Nb-Ta deposits for Nb-Ta ore prospecting. Considered by previous studies the main factors affecting Nb-Ta fractionation and enrichment are the alkalinity of host magmas, water content in melts, melt temperature, fractional crystallization of main Nb-Ta-bearing minerals (columbite-tantalite, biotite, phengite, etc.) and crystallization-melting of the main minerals during partial melting. In addition, the high concentration of fluxing elements (F, Li, Be, P, H2O) also plays an important role in Nb-Ta fractionation and enrichment. Previous studies have found Nb-Ta mineralization could be characterized by magmatic crystallization differentiation, in some cases, but was often associated spatially with strong albitization or lepidolization. Therefore, metallogenic models solely based on magmatic crystallization differentiation or hydrothermal metasomatism could not fully explain the complex mineralization of Nb and Ta. Other questions need to be further addressed include: What is the proportion of crystallization-differentiation to hydrothermal-metasomatism in the process of Nb-Ta fractionation and enrichment? And which stage is more enriched in Nb and Ta? Besides, as columbite-tantalite (coltan) is widely used in LA-ICP-MS U-Pb dating due to its high U and low common Pb contents, with Coltan139 commonly used as a reference standard, laser resolution needs to be further improved to achieve in-situ dating of complex chemical zoning in coltan. The Lu-Hf isotope analysis of coltan is less carried out. In future, coltan Lu-Hf isotope analysis should be developed to trace the Nb-Ta source and clarify the mechanism of Nb-Ta fractionation and enrichment.

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    Research progress on zircon from pegmatites and insights into rare-metal mineralization—a review
    SUN Wenbo, LI Huan
    2023, 30(5): 171-184. 
    DOI: 10.13745/j.esf.sf.2023.5.2

    Abstract ( 153 )   HTML ( 20 )   PDF (4644KB) ( 346 )  

    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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    Identification of lithium-beryllium granitic pegmatites based on deep learning
    JIANG Guo, ZHOU Kefa, WANG Jinlin, BAI Yong, SUN Guoqing, WANG Wei
    2023, 30(5): 185-196. 
    DOI: 10.13745/j.esf.sf.2023.5.20

    Abstract ( 196 )   HTML ( 16 )   PDF (5555KB) ( 358 )  

    Although remote sensing technology is widely used in large-scale exploration of metallic mineral resources, its application in direct rare-metal identification is limited, especially in the identification of hard rock Li/Be-bearing minerals. The problem is mainly due to low spectral resolution, low spatial resolution due to high physical similarity between ore body and wallrock, and small spectral difference between Li/Be-bearing minerals. To address this issue we investigate mineral identification methods based on deep learning models. Samples of Li-Be pegmatites and wallrock are collected from several pegmatite deposits and relevant spectral data are obtained. Spectral enhancement techniques are used to highlight the characteristic spectral features, and the characteristic absorption band similarity model and deep neural network models are compared for mineral identification accuracy. Results show that (1) the extracted characteristic absorption bands using a combination of envelope removal and mixed Gaussian model are better defined and reveal more geological insight. (2) Appropriate spectral enhancement can improve the accuracy of spectral models. In the case studied, the overall accuracy of the spectral model increases by 0.05 based on the logarithmic-first-order derivative spectrum over the original spectrum. (3) In terms of overall model accuracy, deep convolutional neural networks (0.78) perform better than shallow neural networks (0.55 for backpropagation; 0.73 for Extreme Learning Machines). Overall, the combination of hyperspectral imaging and deep convolutional neural network model can quickly and effectively identify pegmatite-hosted minerals, which offer a scientific basis for the direct identification of Li/Be-bearing minerals by satellite remote sensing.

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    Global temporospatial distribution patterns of Nb/Ta-bearing minerals based on big data analytics
    SONG Yan, DONG Shaochun, HU Huan, WANG Rucheng
    2023, 30(5): 197-204. 
    DOI: 10.13745/j.esf.sf.2023.5.12

    Abstract ( 104 )   HTML ( 11 )   PDF (4073KB) ( 238 )  

    Niobium and tantalum are critical rare metals for the emerging industries including electronics, aviation, healthcare, mechanical engineering, and nuclear. With increasing demand for Nb-Ta deposits it is imperative to study their ore-forming mechanism and Nb/Ta enrichment patterns. According to previous studies on the mineral diversity and temporospatial distribution of U, Hg, Be, B, Li-bearing minerals, big data-based mineral evolution research can provide new insights into rare-metal enrichment and ore-forming mechanisms as well as new directions for ore prediction. In this paper, global Nb/Ta-bearing mineral big data involving 1488 minerals and 179 mineral species are obtained from the Global Comprehensive Mineral Database (RRUFF), and historical changes in mineral species and quantity and geospatial distribution of Nb/Ta-bearing minerals are analyzed. During Earth’s evolution mineral species and quantity of Nb-Ta-bearing minerals have increased continuously, and the growth appears to be multi-stage. Prominent growth peaks coincide with the convergence of the Kenorland and Pangea supercontinents and breakup of the Pangea supercontinent, indicating there is an inner relationship between Nb-Ta enrichment and the supercontinent cycle-such inner relationship needs to be further explored.

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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
    2023, 30(5): 205-215. 
    DOI: 10.13745/j.esf.sf.2023.5.19

    Abstract ( 122 )   HTML ( 8 )   PDF (9674KB) ( 204 )  

    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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    Mapping Himalayan leucogranites by machine learning using multi-source data
    WANG Ziye, ZUO Renguang
    2023, 30(5): 216-226. 
    DOI: 10.13745/j.esf.sf.2023.5.22

    Abstract ( 174 )   HTML ( 21 )   PDF (10050KB) ( 250 )  

    Rare-metal elements are irreplaceable in the advanced materials, new energy and information technology industries, making them key strategic mineral resources in global competition. The N-E trending Himalayan leucogranite belt, over 1000 km long, with proven rare-metal resource potential, is expected to become an important rare-metal metallogenic belt in China. The identification of Himalayan leucogranites has mainly relied on geological field mapping; however, the mapping results have high uncertainty due to poor natural conditions, difficult working conditions and lack of detailed geological research—which has hindered rare-metal prospecting in this area. This paper investigates how to delineate the spatial distribution of Himalayan leucogranites by machine learning using geochemical, geophysical and remote sensing data. Results show that (1) regional geochemical, geophysical and remote sensing data provide significant information for leucogranite mapping in a variety of ways. (2) Multi-source data fusion captures the complementarity advantage of using various types of datasets and provides additional diagnostic information for leucogranite mapping. (3) Deep learning algorithms can effectively mine multi-source geoscience data and significantly improve the identification accuracy of leucogranites than traditional machine learning.

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    Granitic aplite-pegmatite lithium deposits in western Sichuan: Ore-bearing property evaluation and geological indicators
    FU Xiaofang, HUANG Tao, HAO Xuefeng, WANG Denghong, LIANG Bin, YANG Rong, PAN Meng, Fan Junbo
    2023, 30(5): 227-243. 
    DOI: 10.13745/j.esf.sf.2023.5.5

    Abstract ( 183 )   HTML ( 18 )   PDF (19252KB) ( 386 )  

    Lithium, known as a clean energy metal and “white oil” of the 21st century, is one of the most important critical metals in China, yet finding large lithium deposits is one of the most challenging problems in geosciences. The high-grade aplite-pegmatite lithium deposits in western Sichuan have superior ore-forming conditions, but they are widely buried under Quaternary sediments. To evaluate the ore-bearing properties and identify the geological indicators of hidden lithium veins, we analyzed the internal relationship between the regional metallogenic setting and geophysical and geochemical anomalies. Combined with the regional ore prospecting, target area prediction/delineation, and ore-deposit positioning results, we developed a comprehensive evaluation method for granitic pegmatite lithium deposits, that is “model guiding-remote sensing image interpretation-geological mapping-geophysical prospecting-geochemical characterization-drilling verification” workflow. Briefly, metallogenic model analysis and geological mapping were carried out to identify geological indicators of target areas, and high-precision gravity detection and audio-frequency electromagnetic geodetic sounding (ATM) were used for hidden vein detection. To pinpoint the vein body, a combination of different depth estimation methods, such as ATM, IP scanning, IP sounding, and high-density resistivity imaging, were used. Large-scale soil geochemical measurements were used to characterize the ore-bearing property of vein bodies. Finally, the belt-shaped, geophysical high-resistance anomalous veins were evaluated according to the spatial relationship between geophysical and geochemical anomalies to identify lithium-bearing veins, that provided a basis for drilling engineering designs. This workflow has been applied to guide the deep prospecting and exploration of giant lithium deposit in Murong, Yajiang County, and in the evaluation of large to medium-size lithium deposits in Zhawulong, Shiqu County and Renyicuo, Yajiang County, and good results have been achieved. This study provided an example of strategic prospecting and exploration of lithium resource in the region.

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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
    2023, 30(5): 244-254. 
    DOI: 10.13745/j.esf.sf.2023.5.14

    Abstract ( 418 )   HTML ( 39 )   PDF (5404KB) ( 514 )  

    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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    Prospecting methods and deep geological setting of the Gabo pegmatite lithium deposit in the Himalayan metallogenic belt
    JIAO Yanjie, HUANG Xuri, LI Guangming, FU Jiangang, LIANG Shengxian, GUO Jing
    2023, 30(5): 255-264. 
    DOI: 10.13745/j.esf.sf.2023.5.23

    Abstract ( 117 )   HTML ( 8 )   PDF (9086KB) ( 335 )  

    Lithium, as an important strategic rare-metal resource, has been highly valued and plays an important role in aerospace, atomic energy and other fields. The Gabo lithium deposit is located in Luozha County, Tibet, adjacent to the Lalong dome in the north and the Kulagangri dome in the south. It is a newly discovered pegmatite lithium deposit in the Himalayan metallogenic belt. In the mining district, many gently-dipping spodumene-bearing pegmatite veins are developed along the detachment zone, in marble-intercalated schist strata of the detachment system, showing a close spatial relationship between lithium mineralization and the detachment zone and marble. In this paper, prospecting methods including high-density electric resistivity survey, radioactive survey and audio-frequency magnetotelluric sounding are investigated. The Gabo lithium pegmatite is characterized by high resistivity, low polarization and low gravity anomaly, without obvious radioactive anomaly. The spatial relationships between the Gabo pegmatite, the lower detachment fault, and granites in dome cores are determined by audio magnetotelluric and high-density resistivity surveys. Satellite gravity and magnetotelluric data show that the Gaibo lithium deposit is located near a north-south fault or rift valley, and its formation may be related to deep conductive layers and large-scale magma differentiation and crystallization. Its spatial structure and deep geological characteristics suggest that Gaibo is one of the potential areas for rare-metal mineralization in the Himalayas.

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    Detectability of pegmatite lithium deposits by controlled-source electromagnetic methods
    WEI Xinhao, ZHOU Nannan, ZHANG Shun
    2023, 30(5): 265-274. 
    DOI: 10.13745/j.esf.sf.2023.5.21

    Abstract ( 107 )   HTML ( 2 )   PDF (3426KB) ( 226 )  

    Lithium-bearing minerals are used as raw materials for rechargeable lithium batteries on electric cars, cell phone, etc., while pegmatite lithium deposits account for about a quarter of the world’s lithium resources. However, the effectiveness of electromagnetic exploration methods for high-resistivity pegmatite Li-Be deposits has not been systematically studied. Pegmatite dikes generally have high resistivity—it is close to 10000 ohms for ore-bearing pegmatites, and higher for common pegmatites. Whilst the resistivity of the host rock is generally up to several thousand ohms. Thus how to effectively identify high-resistivity ore-bearing pegmatites under resistive background has become an urgent technical problem. Here, we use transverse magnetic field to solve the detection problem for high-resistivity targets, and the effectiveness of the newly developed detection method is evaluated over the traditional single-line controlled-source method. We systematically compare different components of electromagnetic response from different configurations in terms of response characteristics and resolution, and calculate the root mean square misfit. We find the horizontal electric field component from double-line source shows higher resolution for high-resistivity targets over the traditional single-line source.

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    Metallogenic epoch, magmatic evolution and metallogenic significance of the Gabo lithium pegmatite deposit, Himalayan metallogenic belt, Tibet
    GUO Weikang, LI Guangming, FU Jiangang, ZHANG Hai, ZHANG Linkui, WU Jianyang, DONG Suiliang, YANG Yulin
    2023, 30(5): 275-297. 
    DOI: 10.13745/j.esf.sf.2023.5.9

    Abstract ( 165 )   HTML ( 10 )   PDF (17230KB) ( 300 )  

    In recent years rare-metal metallogeny of the Himalayan leucogranite belt has attracted much attention, and the discovery of the Cuonadong and Qiongjiagang rare-metal deposits sets a prelude to the rare-metal exploration and research in the Himalayas. According to previous researches the Himalayan metallogenic belt is expected to become a new world-class Li-Be-W-Sn metallogenic belt. One example is the Gabo lithium pegmatite deposit in northeastern Kulagangri Dome. This study focuses on the metallogenic characteristics, formation age and magmatic evolution of the Gabo pegmatite deposit. Rare-metal (Li, Be, Rb, Nb, Ta) minerals of the Gabo pregmatites include spodumene, elbaite, lepidolite, petalite, columbite-tantalite and beryl. The pegmatites have simple zonal structures. Spodumene mainly occurs as fine albite-spodumene or massive microline-spodumene zones, where the former is the main component of ore body. Monazite U-Pb dating results show that the Gabo pegmatites were formed in the Early Miocene (23-21 Ma) coinciding with the period of peak activity of the southern Tibet detachment system (STDS), which indicate a close genetic relationship between pegmatite formation and STDS activities. According to their petrology, mineralogy and geochemistry, the Gabo pegmatites are highly differentiated and evolved, where plagioclase, zircon, mica and other minerals were formed during fractional crystallization of pegmatite-forming melts. According to chemical compositional analysis muscovite is the main mica type in the Gabo pegmatites, whilst the occurrence of lepidolite is indicative of high-level pegmatite differentiation as the increase of magmatic differentiation led to decrease of Fe-Mn contents and increase of Li content in mica. The Gabo lithium pegmatite deposit is an important achievement in rare-metal prospecting based on metallogenic models of the Himalayan leucogranite, which in turn greatly improves the metallogenic models.

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    Pegmatites of Shangfu deposits, Lianyunshan, northeastern Hunan: Geochemical characteristics, fluid inclusions, and genetic constraints
    HUANG Xiaoqiang, LIU Qingqi, LI Peng, LIU Xiang, ZENG Le, ZHANG Liping, SHI Weike, HUANG Zhibiao, FAN Pengfei, WAN Haihui, LIN Yue, WANG Xuanmin, CAI Chang
    2023, 30(5): 298-313. 
    DOI: 10.13745/j.esf.sf.2023.5.7

    Abstract ( 131 )   HTML ( 7 )   PDF (11424KB) ( 175 )  

    The recent discovery of the Nb/Ta-rich, No.3 pegmatite vein in Shangfu area, Lianyunshan intrusion, northeastern Hunan, shows a good prospect for rare-metal deposits in this area. In this paper, the geochemistry of the Shangfu pegmatite and fluid inclusions in host minerals are studied, and the genesis of the pegmatite deposit is discussed to enrich the understanding of rare-metal mineralization in the region. The Shangfu pegmatite is characterized by high silicon (w(SiO2), 65.05%-79.15%), high aluminum (w(Al2O3), 11.38%-19.64%) and low Ca, Mg, Fe contents, and is relatively rich in alkali (w(Na2O+K2O), 5.62%-9.87%), (medium potassium) calc alkaline and peraluminous. The pegmatite is distinctively enriched in Nb, Ta, Zr, Hf and U, and relatively depleted in Ba and Sr; ∑REE ranges between (11.74-29.40)×10-6, with enriched LREE and depleted HREE, consistent with a crustal origin. The fluid inclusion type is gas-liquid two-phase brine solution; the homogenization temperature of the fluid inclusions is between 159-443 ℃; the salinity of brine solution is 3.06%-6.74%; and the average trapping pressure of the fluid inclusions is 190 MPa. The ore-forming fluid is characterized by medium-high temperature and low salinity; and C, H, O isotopic analysis shows that the ore-forming fluid is related to deep magmatic activity and may be mixed with a small amount of formation water. The rare-metal mineralization is controlled by magmatic differentiation and evolution. The mica monzonitic granite and pegmatite in the area have the same material source which provides the source material and ore-forming fluid responsible for Nb/Ta mineralization.

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    Deep structure and dynamics of the eastern segment of the Qilian orogenic belt in the northeastern margin of the Tibetan Plateau
    CHENG Yongzhi, GAO Rui, LU Zhanwu, LI Wenhui, WANG Guangwen, CHEN Si, WU Guowei, CAI Yuguo
    2023, 30(5): 314-333. 
    DOI: 10.13745/j.esf.sf.2023.6.35

    Abstract ( 141 )   HTML ( 14 )   PDF (15510KB) ( 294 )  

    The eastern segment of the Qilian orogenic belt is located in the northeastern margin of the Qinghai-Tibet Plateau. It comprises the Linxia and Longzhong blocks. The regional tectonic framework is complex due to the influence of multiple tectonic events, including the closure of the Qilian Ocean, the convergence of the North China block and Qilian terrane, and the collision of the Indian and Eurasian plates. To investigate the geological evolution of the region and the location of suture between the blocks, we analyzed seismic data collected from 33 portable ChinArray II broadband stations over a 3-year period (2013-2016) and obtained crustal structure, Poisson’s ratio, and Moho morphology at seismic stations by teleseismic P-wave receiver function, H-κ stacking, and Common Conversion Point (CCP) stacking methods. Our results show that the Maxianshan fault is an important boundary fault dividing the Linxia and Longzhong blocks. The fault zone, shown as a continuous west-dipping negative seismic phase in the CCP section, cuts through the Earth’s crust and is the suture line between the Linxia and Longzhong blocks. The Linxia block has obvious layered crust, with Japanese island arc characteristics, while low-velocity anomalies in the middle/lower crust likely indicate saline fluids. The Longzhong block has layered upper crust and slightly layered middle/lower crust, with weak low-velocity and ocean island basaltic crust characteristics, and may originate from the Mariana island arc. The insignificant Conrad interface and lateral variation of Moho depth in the southwestern margin of the Ordos block is consistent with stable craton characteristics. Meanwhile, beneath the Liupanshan tectonic belt, the upward thrust of the middle/upper crust towards the southwestern margin of the Ordos block provide the deep structural evidence for the Cenozoic uplift of the Liupanshan structural belt.

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    Late Cenozoic deformation characteristics and mechanism of the Beishan-Alxa region
    ZHANG Jin, ZHANG Beihang, ZHAO Heng, YUN Long, QU Junfeng, WANG Zhenyi, YANG Yaqi, ZHAO Shuo
    2023, 30(5): 334-357. 
    DOI: 10.13745/j.esf.sf.2023.8.16

    Abstract ( 117 )   HTML ( 7 )   PDF (39683KB) ( 251 )  

    The Beishan-Alxa region is located in the middle segment of the Central Asian Orogenic Belt. This region, controlled by the Indian-Eurasian collision in the Late Cenozoic, has undergone intracontinental deformation to varying degrees. It is a stress transfer area between the Qinghai-Tibetan Plateau and the Mongolian Plateau, and a key area to study the remote effects of the Indian-Eurasian collision. Differing from the Late Cenozoic deformation in the Tianshan/Altai regions in the western segment of the Central Asian Orogenic Belt, the Beishan-Alxa region developed a set of near EW-trending left-lateral strike-slip faults, and between them a series of NE-trending normal faults were developed which control faulted depression (pull-apart) basins. The much larger near EW-trending faults, with a long strike extension, become the main structure of Late Cenozoic deformation in this region. On the whole, the deformation is in the step area between the NEE-trending South Mongolian-Tianshan left-lateral strike-slip fault on the north side, and the NEE-trending Altyn Tagh fault on the south side. In this left-lateral left-step area, the deformation is manifested as nearly E-W secondary strike slip faults (P shear), derived from the boundary strike-slip faults and the NE extensional basins (such as the Ejina basin, Jiujing basin). Under sinistral transtensional setting this area develops a sinistral shear structure distinct from the dextral shear structure of the Mongolian Gobi Altai; while its flat landform, developed under regional extension within the step area, makes it the main catchment basin area in the Beishan-Alxa region. The GPS velocity field and anisotropy data of the upper mantle-lower crust indicate the Tarim Craton plays an important role in the northward expansion of the Qinghai-Tibetan Plateau. At the Tarim Craton the upper mantle-lower crust of the Qinghai-Tibetan Plateau turns northeastward along the southeastern edge of the craton while the Tarim continues to exert stress northeastward, leading to the rise of the Tianshan mountain range and northward compression of the Junggar Basin to cause NNW-trending dextral shear deformation in the Altay Mountains. On the other hand, the northward movement of the upper mantle-lower crust causes Late Cenozoic sinistral shear deformation in the Beishan-Alxa region and southern Mongolia. Deformation in the Beishan-Alxa region is widespread, which is different from Cenozoic deformation in the Tarim-Tianshan-Junggar region where deformation is concentrated in the Tianshan and Altay Mountains.

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    Crustal structure beneath a seismic linear array in the Western Junggar, northwestern China by RF-RTM imaging
    JIANG Xiaohuan, HUANG Rong, ZHU Lupei, LU Zhanwu, LUO Yinhe, ZHANG Rongtang, XU Hao
    2023, 30(5): 358-368. 
    DOI: 10.13745/j.esf.sf.2023.7.16

    Abstract ( 82 )   HTML ( 4 )   PDF (7474KB) ( 90 )  

    Data used in this paper were obtained from a 100-km long linear seismic array, Western Junggar area, by continuous recording from July 08 to August 02, 2017. We first calculate teleseismic P-wave receiver functions and then apply reverse time migration of teleseismic receiver function (RF-RTM) method to image the Moho variations beneath the linear array. The results show obvious differences in the crustal structure beneath the Zaire Mount and the Junggar Basin. The Moho discontinuity beneath the Zaire Mount flattens to a depth of ~42 km; while the crustal structure beneath the Junggar Basin appears quite complex. The basement of the Junggar Basin extends to a depth of 3 km, and the Moho discontinuity gradually deepens along the trend of the linear array from northwest (NW) to southeast (SE), finally reaching to a depth of 50 km. We also observe especially an obvious velocity anomaly interface at a depth of about 35 km, and infer that it might be generated by a Paleozoic fossil oceanic subducting slab. Our study may shed light on the formation and evolution of continental lithosphere in the Western Junggar area.

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    Constraining the crustal structure of the southern segment of the north-south gravity lineament by the receiver function H-κ-c method
    MU Qing, HUANG Rong, YAN Jiayong, LU Zhanwu, LUO Yinhe, ZHANG Yongqian, JIANG Xiaohuan, WEN Hongbin, WEI Penglong, ZHOU Wanli
    2023, 30(5): 369-383. 
    DOI: 10.13745/j.esf.sf.2023.7.31

    Abstract ( 100 )   HTML ( 11 )   PDF (19199KB) ( 82 )  

    The north-south-oriented Daxing’an-Taihangshan-Wulingshan Gravity Lineament, which is across the whole Mainland China is considered the most important intra-continental gravity gradient belt in East China. Data used in this study were from 43 permanent and 10 portable broadband seismic stations near the Wulingshan Gravity Lineament. A total of 12739 teleseismic P-wave receiver functions (pRFs) were calculated, and pRFs from 7 and 46 stations were then stacked using respectively the H-κ and H-κ-c methods. Combining previous studies, we obtained the lateral variation of the crustal thickness, average crustal vP/vS ratio and crustal anisotropy beneath the study region. The crustal thickness varied greatly, between 30-52 km, where the thickest crust was found under the Daba Mountain area and the thinnest to the east of the Xuefeng Mountain. Our results also showed the maximum gradient of the Moho interface traced from the Qinling-Dabashan Mountain in the north along the junction area between the Jianghan Basin and the Wuling uplift, and extended southward to the north of the Jiangnan orogenic belt. The high vP/vS ratio (>1.81) are generally distributed in the area west of the Wulingshan Gravity Lineament, while to the east the vP/vS ratio are lower than (<1.75) and so did the Jiangnan orogenic belt. Similar differences in crustal anisotropy were found between the two sides of the Wulingshan Gravity Lineament, where the fast polarization directions (FPDs) on the east side is nearly E-W while on the west side nearly NE-SW. Finally, we inferred a common occurrence of lower crustal delamination near the Wulingshan Gravity Lineament and areas to the east.

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    Geodynamic processes and mechanisms of the formation of hot dry rock in the Gonghe Basin
    ZHANG Baojian, LEI Yude, ZHAO Zhen, TANG Xianchun, LUO Yinfei, WANG Guiling, GAO Jun, ZHANG Dailei
    2023, 30(5): 384-401. 
    DOI: 10.13745/j.esf.sf.2023.2.63

    Abstract ( 129 )   HTML ( 13 )   PDF (13767KB) ( 175 )  

    Hot dry rock of the Gonghe Basin is the first hot dry rock drilled in China, but its formation mechanism is still unclear. Based on previous data, combined with our thermophysical property testing and geochemical, geophysical investigation results, this paper discusses the genesis and geodynamic evolution of hot dry rock in the Gonghe Basin: (1) A series of tectonic activities, such as late collisions between the Indian and Eurasian plates and related post-collisional events lead to deep dynamic processes in the northern Qinghai-Tibetan Plateau, including tectonic uplift, asthenosphere upwelling and thermal intrusion. Under the combined effects of gravitational energy amassed by tectonic uplift and resulting gravity buoyancy, lateral extrusion stress in the northeastern margin of the Qinghai-Tibetan Plateau, mantle drag force, and thermal intrusion of the asthenosphere, crustal and mantle fluids flow from southwest to northeast along weak lithospheric layers (zones) in the Tibetan Plateau and Gonghe Basin. (2) Weak lithospheric layers (zones), such as plate (block) suture zones, plastic rheological ductile shear zones or high conductivity, low velocity bodies, and deep, large strike-slip fault zones and fault intersections, are channels for mantle melt migration to the Earth’s crust. (3) Geological heterogeneity of the Earth’s deep structure leads to nonuniform accumulation of heat produced at depth in the shallow crust. Heat flow is disturbed by groundwater activity and sedimentation/denudation in the shallow lithosphere, lithospheric deformation in the deep lithosphere, and magma convection in the aesthenosphere, while deep-heat flows laterally toward high-thermal conductivity granites, resulting in uneven heat distribution from deep to shallow in the lithosphere. This paper makes a breakthrough from the previous understanding of the genesis of hot dry rock in the Gonghe Basin based on a single factor and a few heat-control factors, and expounds a comprehensive genetic mechanism of hot dry rock, from heat source, heat migration driving force and channel, to reservoir and cap (layer).

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    The “extensive quantization” problem in geoscience research
    LU Laijun, CAO Mengxue, TAN Yulei
    2023, 30(5): 402-406. 
    DOI: 10.13745/j.esf.sf.2023.2.43

    Abstract ( 150 )   HTML ( 9 )   PDF (1533KB) ( 137 )  

    Quantum is the smallest unit of energy and quantum mechanics is used to describe the properties, behaviors and dynamics of quantum states. Under the basic concept of natural science that macroscopic phenomena are governed by microscopic physics, quantum geoscience research concerns with, among others, a certain correspondence between macroscopic and microscopic quantities. As we all know, one of the problems in systems geology lies in the mutual coupling relationship between the geospheres and its underlying dynamic mechanisms. Macro-level dynamic mechanism as such should be a natural extension of certain microscopic mechanism(s). Presently it is an urgent task in theoretical research to describe geological phenomena according to quantum mechanics. This paper proposes an “extensive quantum-quantum” combined approach to describe, from the perspective of quantum mechanics, the asymptotic relationship between the macroscopic and microscopic geological attributes using a set of quantitative equation models. This method can be applied to address the problem of quantization in geoscience research to build a theoretical foundation for the establishment of quantum geoscience and at the same time provides a scientific basis for quantum computing for geoscience.

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    Crustal thickness and Poisson’s ratio beneath the continental margin of southeastern China and the tectonic implications
    LI Qiang, WU Jianping
    2023, 30(5): 408-419. 
    DOI: 10.13745/j.esf.sf.2022.9.8

    Abstract ( 122 )   HTML ( 10 )   PDF (6368KB) ( 138 )  

    The continental margin of southeastern China has undergone complex tectonic evolution since the Mesozoic, especially during the Late Mesozoic under intense magmatic activities. Here, we determine the crustal thickness and the average Poisson’s ratio for crust to better understand crust-mantle interaction and related geodynamic processes in this region. Teleseismic waveform data were collected from 90 permanent seismic stations deployed in Fujian, including 2 deployed by researchers from Taiwan, China. The crustal thickness and the average Poisson’s ratio of crustal rocks were calculated by H-κ stacking method using teleseismic P-wave radial receiver functions. Combining the calculation results with previous observation results by portable stations, high-resolution distribution maps of crustal thicknesses and Poisson’s ratios were obtained, which show the continental crust is generally thin, with crustal thickness ranging from 28.0 to 34.1 km (averaging 31.0 km), and Poisson’s ratio ranging from 0.22 to 0.29; the Moho interface in the study area is gently undulating, with overall thinning from inland to the coast, and Moho offsets beneath some faults were observed. The coastal area along the continental margin is situated on thin continental crust, not the transition zone between continental and oceanic crusts. The Fu’an-Nanjing fault zone is a vitally important fault zone in the region. The crustal thickness and Poisson’s ratio for crust have a positive correlation in the coastal Fujian-Zhejiang volcanic-intrusive rock belt to the east of the fault zone and a negative correlation in the inland Cathaysia block to the west of the fault zone. Compared to inland, Poisson’s ratio for crust in the coastal area is generally higher, which may be related to Late Mesozoic magmatic underplating and the development of low-velocity thin layers within the crust in the coastal area.

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    Recover the Liyue Basin position in the southern margin of the South China Sea before seafloor spreading
    CHEN Wenlin, ZHENG Qiugen, HUANG Yiming, ZHANG Yi, LIN Changsong
    2023, 30(5): 420-429. 
    DOI: 10.13745/j.esf.sf.2023.2.75

    Abstract ( 58 )   HTML ( 7 )   PDF (12114KB) ( 108 )  

    Based on the conceptions that magnetic stripping is symmetrical about a mid-ocean ridge axis and that magnetic stripes from the same period are isochronic, using the existing magnetic anomaly data of the South China Sea, and assuming the positions of the South China Block and the northern margin of the South China Sea are relatively fixed and the southern margin of the South China Sea began to drift southward since 32 Ma, this paper restores the seafloor spreading history of the South China Sea and recovers the relative position of the Liyue Basin in various periods. The Liyue Basin was located next to the southeast rim of the Pearl River Mouth Basin before seafloor spreading. This finding is further supported by the comparison results of basement properties, development and sedimentary characteristics of Mesozoic strata, as well as Cenozoic tectonic activities and subsidence and sedimentary characteristics between the Liyue Basin and the northern margin basin of the South China Sea. This study provides an essential reference for the structural evolution, sedimentary filling characteristics, sediment source analysis, and petroleum geological conditions of the Liyue Basin.

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    Continental drift process revealed by high precision seismic survey in the central basin of the South China Sea
    LIANG Guanghe
    2023, 30(5): 430-449. 
    DOI: 10.13745/j.esf.sf.2022.6.10-en

    Abstract ( 50 )   HTML ( 13 )   PDF (18914KB) ( 115 )  

    The formation and evolution of the South China Sea has been widely studied. More than five genetic models have been proposed. The current popular model is seafloor spreading, but it is difficult to reasonably explain the mid-ocean ridge jumping in South China Sea and the continental fragments found in the central basin of the South China Sea. First, based on two high precision seismic exploration sections in the central basin of the South China Sea, a new tectonic geological interpretation of the two seismic exploration sections was given on the basis of in-depth analysis of the layered structure of the oceanic crust. Then, through the formation process of extensional tectonics, the model of continental drift driven by mantle upwelling and continental crust gravity slip was developed. Finally, the formation and evolution process of the South China Sea was deeply studied. The results show that the formation of the South China Sea is a “tectonic extrusion + active drift” model. Tectonic extrusion is a large-scale passive extrusion of the microcontinents in the southeast margin of Eurasia plate caused by the India-Eurasia collision, while active drift is the active drift of the microcontinents after extrusion. The residual seismic reflection in the central basin of the South China Sea is a phenomenon of seafloor spreading caused by active drift of microcontinents. Furthermore, the geotectonic evolution of the microcontinents surrounding South China Sea was restored. The proposed new model can reasonably explain the phenomenon of mid-ocean ridge jumping in the South China Sea and the genetic mechanism of continental debris. The proposed new continent drift model provides a new dynamic model for plate movement.

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    Secondary minerals in basalts of the Evevpenta gold occurrence (North Kamchatka, Russia) as indicators of ore forming processes
    Anastasiya SERGEEVA, Pavel ZHEGUNOV, Elena SKILSKAIA, Mariya NAZAROVA, Elena KARTASHEVA, Anna KUZMINA, Svetlana MOSKALEVA, Olesya ZOBENKO, Sharapat KUDAEVA, Ekaterina PLUTAKHINA, Kseniya SHISHKANOVA
    2023, 30(5): 450-468. 
    DOI: 10.13745/j.esf.sf.2023.7.1

    Abstract ( 162 )   HTML ( 17 )   PDF (9391KB) ( 70 )  

    The mineralogy seen in propylitic alteration of basalt host rocks in the Evevpenta gold occurrence in North Kamchatka is based on a vein system consisting of quartz, adularia-quartz, quartz-carbonate veins, and, hydrothermal breccias hosted in dacite. Vein minerals are native gold, tellurides, sulfides, selenides, and Au-Ag chlorides. The propylitic alteration occurs at a distance from the epithermal veins; however, it contains characteristic mineral assemblages useful for the reconstruction of an ore-formation environment. Four distinct hydrothermal alteration assemblages are recognized within the propylitic zone: 1. fluorapatite-fluorine-aluminous titanite, 2. quartz-calcite-clinochlore, 3. quartz-calcite-stilbite-montmorillonite, and 4. calcite-mordenite. The earliest mineral assemblage was formed from an acid F-enriched hydrothermal fluid. The concentration of fluoride in fluid was 0.2-1.2 g/L, and temperature of about 550 ℃. The long-term interaction between the acid hydrothermal fluid and olivine basalt host rocks resulted in increasing pH to near neutral that caused a chloritization process. The chloritization stage hydrothermal fluid was enriched in Fe and Mg with temperatures of about 175-210 ℃, chlorite I, and 120-140 ℃, chlorite II. The final stage of alteration consists of zeolite group minerals, which were precipitated from the hydrothermal fluid of pH ~9 and temperature >135 ℃. The high pH of the hydrothermal fluid might be explained by the presence of bicarbonates and carbonates and removal of the iron salt from the solution. Based on the alteration mineral assemblages of the propylitic zone, the physical and chemical conditions of the Evevpenta vein system are discussed. The transport of ore elements took place due to the formation of precious metal Cl- and OH- complexes at the stage of hydrothermal system formation with circulation of alkaline sodium chloride solutions. Chalcogens were also transferred by high pH solutions.

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    Lithium isotope geochemistry—a review
    CHEN Yu, XU Fei, CHENG Hongfei, CHEN Xianzhe, WEN Hanjie
    2023, 30(5): 469-490. 
    DOI: 10.13745/j.esf.sf.2023.2.51

    Abstract ( 466 )   HTML ( 34 )   PDF (4298KB) ( 543 )  

    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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    Paleoenvironmental characteristics in the late stage of biosphere recovery in the southern margin of the North China Plate after PTME—evidence from the Middle Triassic Ermaying Formation
    XING Zhifeng, ZHANG Xiangyun, LI Wanying, QI Yong’an, ZHENG Wei, WU Panpan, ZHANG Lijun
    2023, 30(5): 491-509. 
    DOI: 10.13745/j.esf.sf.2023.3.5

    Abstract ( 77 )   HTML ( 2 )   PDF (19367KB) ( 53 )  

    The Triassic is an important period of ecological recovery after the Permian-Triassic Mass Extinction (PTME) and also an important tectonic transition period. As ecosystem recovery was near completion in the Middle Triassic while biosphere recovery was in the late stage, the environmental and paleontological condition of this period was greatly important to a full ecological recovery. Based on detailed geologic profile study and sample testing conducted in the Middle Triassic Ermaying Formation in Baiping, Dengfeng, western Henan, the Middle Triassic sedimentary environment and paleoenvironmental changes were analyzed by sedimentology and geochemical methods. The results show that (1) The lower member of the Ermaying Formation (layers 2-18) developed four sedimentary cycles under meandering river environment, where mainly composed of yellow-green fine-grained feldspar sandstone and purplered mudstone with unequal thickness interbeds. The middle member (layers 19-25) is dominated by thick yellow-green feldspathic quartz sandstone in the bottom and frequently interbedded mudstone and sandstone in the upper, which is the shore-shallow lake deposition. From the lower to the middle member, Ermaying Formation experienced alternating depositions of coarse-grained and fine-grained sediment, and gradually changed from fluvial facies to shore-shallow lake facies. (2) The low Mg/Ca and Sr/Cu ratios (1.8-5.2, averaging 3.5) of samples indicate the Ermaying Formation was deposited under warm and humid climate conditions. The Sr/Ba (0.15-0.42, averaging 0.29) and ∑LREE/∑HREE ratios, Ce anomaly index and elemental ratios of redox sensitive elements (U, V, Cr, Ni, Co) in the Ermaying Formation indicate its sedimentary environment type is continental freshwater under oxidation conditions. In summary, the Ermaying Formation has typical fluvial-lacustrine sedimentary facies, and, compared with the underlying Heshanggou Formation, its paleoclimate obviously changed from arid and hot to warm and humid, which plays an important role in the ecosystem recovery.

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    Chemical weathering and its associated CO2 consumption on the Tibetan Plateau: A case of the Lhasa River Basin
    XIE Yincai, YU Shi, MIAO Xiongyi, LI Jun, HE Shiyi, SUN Ping’an
    2023, 30(5): 510-525. 
    DOI: 10.13745/j.esf.sf.2023.2.66

    Abstract ( 134 )   HTML ( 8 )   PDF (3084KB) ( 128 )  

    In order to study chemical weathering and its effects on CO2 consumption and climate change on the Tibetan Plateau, hydrochemical data were collected bi-monthly, over a hydrological year between November 2019 to October 2020, at selected hydrological monitoring stations across the Lhasa River Basin. Combined with δ13CDIC and $\partial^{34}\mathrm{S}_{\mathrm{SO}_4}$ data, the hydrochemistry of the river basin and its major influencing factors were investigated. Mass-balance and forward-model approaches were applied to calculate the end-member contribution, chemical weathering rate, and atmospheric CO2 consumption flux in the river basin. The main ionic species in river water were Ca2+ and $\mathrm{NO}_3^{-}$, and the hydrochemical type was HCO3-Ca. The cation contribution percentages from atmospheric input, human activities, silicate weathering, and carbonate weathering were 6%, 4%, 21% and 70%, respectively. Chemical weathering is largely caused by sulfuric acid corrosion, where coal strata and sulfide deposits each contributed 50% sulfides, as evidenced by the chemical composition of river water, and δ13C (-8.78‰--1.35‰) of dissolved inorganic carbon and $\partial^{34}\mathrm{S}_{\mathrm{SO}_4}$ (-2.26‰--1.10‰) of sulfate in river water; and the sulfuric acid involvement in carbonate weathering was significantly stronger in dry season than in rainy season. By estimation, the annualized weathering rate and CO2 consumption flux were 5.20 t·km-2·a-1 and 118 × 103 mol·km-2·a-1 respectively for silicate, and 22.5 t·km-2·a-1 and 202 × 103 mol·km-2·a-1 respectively for carbonate, excluding the impact of sulfuric acid. With sulfuric acid involvement, the annualized weathering rate for carbonate increased by 31% to 29.4 t·km-2·a-1, and CO2 consumption flux for carbonate and silicate combined reduced by 35% to 207 × 103 mol·km-2·a-1. This work revealed that sulfuric acid-mediated weathering can change the regional carbon cycle and should be taken into consideration in carbon cycling modeling.

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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
    2023, 30(5): 526-540. 
    DOI: 10.13745/j.esf.sf.2023.2.79

    Abstract ( 139 )   HTML ( 12 )   PDF (7482KB) ( 118 )  

    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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    Effects of different remediation treatments on heavy metals and microorganisms in mining wasteland
    WEI Hongbin, LUO Ming, ZHANG Shiwen, ZHOU Pengfei
    2023, 30(5): 541-552. 
    DOI: 10.13745/j.esf.sf.2023.6.3

    Abstract ( 219 )   HTML ( 7 )   PDF (3787KB) ( 113 )  

    In order to optimize the application of plant-assisted bioremedation to mining wasteland, the Dabaoshan mining wasteland in Shaoguan, Guangdong Province was investigated through in situ remediation field experiment to assess the effects of different treatment plans—consisting of companion planting (trees, shrubs, grass crops) and soil conditioner application—on heavy metals (HMs) and microorganisms in mining wasteland. The bioconcentration factor (BCF), biotransfer factor (BTF) and HM retention rate were calculated and compared for the dominant plants to assess their HM remediation capacity. Based on the results of high-throughput soil DNA sequencing, the relationship between soil microbiome richness and diversity and environmental factors was discussed. Five dominant plants were identified under different treatment plans and showed varying remediation capacities. In the dominant plants, the overall BCF and BTF of heavy metals followed the order of Cd > Cu > Zn > Pb, and HM retention rates were Pb > Zn > Cu > Cd. Heavy metal contents in roots, stems and leaves of different plants varied greatly. Among the five dominant plants, Cd concentrated most in the stems and leaves of Pinus elliottii and Lagerstroemia indica, and HMs accumulated in roots of Plantago asiatica and Ligustrun lucidum Ait.; while Boehmeria nivea was resistant to HMs via avoidance. All treatment plans significantly reduced Cd/Pb soil contents by more than 50%. The addition of soil conditioners and use of companion planting significantly increased soil microbiome richness and diversity, where plan D showed the largest reduction of Cd bioavailability and plan C the highest microbiome diversity. Proteus and Actinomycetes were the dominant flora in all soil samples. Furthermore, companion planting of high tolerance plants significantly reduced Cd/Pb bioavailability, altered soil microbiota profile, and helped to increase the abundance of HM resistance flora and establish a healthy soil microbiota, thereby achieving effective bioremediation of mining wasteland. Companion planting of high tolerance trees, shrubs and grasses with variable plant combinations is the best phytoremediation strategy for mining wasteland.

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    Estimating bedload transport at the eastern entrance to the Qiongzhou Strait by numerical simulation
    TONG Changliang, ZHU Yu, WU Xiangbai, MO Yingming, WANG Xuemu
    2023, 30(5): 553-566. 
    DOI: 10.13745/j.esf.sf.2023.2.73

    Abstract ( 84 )   HTML ( 5 )   PDF (11778KB) ( 81 )  

    The widespread tidal ridges at the eastern entrance to the Qiongzhou Strait are mainly controlled by east-west tidal currents of four types, i.e., eastward/westward flood or ebb. According to the numerical simulation, the speed of tidal currents is relatively fast in the central waterway, the north shore and shoals, where the average vertical speed can reach 0.7-1.0 m/s, whilst elsewhere it is about 0.3-0.5 m/s. In general, the eastward current speed is faster than the westward counterpart, but the opposite is true at the north shore due to the western Guangdong coastal current. This characteristic is especially obvious during spring tides where the current speed is generally 1.5-2.0-fold faster compared to during neap tides. The study area is dominated by sandy and gravel deposits distributed mainly in the central waterway, shoals and the north shore, where the average particle size of sediment is 2.67Φ areawide, with poor sorting overall. The critical starting rate of bedload transport ranges between 0.12-0.79 m/s—above 0.6 m/s in the central channel to shoals in the southwest, and generally 0.35-0.45 m/s in sandbanks. However, in muddy areas of the eastern shelf, the starting rate is generally less than 0.22 m/s. Using the Bagnold transport model, the north shore has the highest transport rate, followed by the central waterway and shoals. Within a tidal cycle, sediment is transported westward along the north shore but mostly eastward elsewhere, and the net transport volume between spring and neap tides can differ by an order of magnitude. According to the cross-section calculation, the net amount of bed materials transported through the eastern entrance to the Qiongzhou Strait is on the order of 108 kg per month.

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