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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
    Abstract302)   HTML12)    PDF(pc) (8487KB)(1835)       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
    Abstract357)   HTML60)    PDF(pc) (3044KB)(737)       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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    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
    Earth Science Frontiers    2023, 30 (5): 1-25.   DOI: 10.13745/j.esf.sf.2023.5.24
    Abstract212)   HTML49)    PDF(pc) (22668KB)(548)       Save

    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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    Tectonic evolution and Cenozoic deformation history of the Qilian orogen
    WU Chen, CHEN Xuanhua, DING Lin
    Earth Science Frontiers    2023, 30 (3): 262-281.   DOI: 10.13745/j.esf.sf.2022.12.20
    Abstract603)   HTML41)    PDF(pc) (14534KB)(535)       Save

    The Qilian orogen—formed along the northern margin of the eastern Tethys as results of pre-Cenozoic multi-phase subduction, continental collision and punctuated orogeny involving the North China craton and the Qaidam paleocontinent—develops widespread ophiolitic mélange belts and (ultra-) high pressure metamorphic and arc igneous rocks. The present Qilian Mountains, a key tectonic zone undergoing plateau uplift/expansion along the northern margin of the Tibetan Plateau, with complex intracontinental deformation and deep structures, records the histories of tectonic deformation and basin-mountain evolution during different stages of plateau growth in the Cenozoic. This paper, on the basis of comprehensive analysis of regional geological data, discusses the nature of Proterozoic metamorphic basement, paleo-oceanic evolution during the Neoproterozoic-Paleozoic, and Mesozoic-Cenozoic structural deformation, and explores the tectonic evolution of the Qilian orogen and the intracontinental deformation history of the Qilian Mountains. The Early-Neoproterozoic and Early-Paleozoic arcs represent respectively subduction-collision events took place in the Paleo-Qilian and (South/North) Qilian oceans. Basement structure beneath the North China craton suggests that the Qilian ocean is not the ocean separating the Gondwana and Laurasia continents, but rather a relatively small embayed sea along the southern margin of the Laurasia continent. The northeastern margin of the Tibetan Plateau experienced two-stage tectonic deformation and basin-mountain evolution in the Cenozoic, while transition from Early-Cenozoic thrust activity to joint action of strike-slip/thrust faults occurred in the Miocene, where, with rapid uplift of the Eastern Kunlun Range, a large Paleogene basin split into two basins—the current Qaidam Basin and the Hoh Xil Basin. Since the Middle-Late Miocene the tectonic framework along the margin has been mainly controlled by the development and clockwise rotation/lateral growth of two large near-parallel transpressional tectonic systems, of Eastern Kunlun and Haiyuan. The growth process and development mechanism of the large-scale strike-slip fault system in the Qilian orogen is a central issue of research on intracontinental deformation and requires in-depth quantitative examination.

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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
    Abstract391)   HTML38)    PDF(pc) (5404KB)(467)       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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    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
    Abstract424)   HTML30)    PDF(pc) (4298KB)(463)       Save

    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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    Carbon dioxide storage in China: Current status, main challenges, and future outlooks
    DENG Yirong, WANG Yonghong, ZHAO Yanjie, GU Peike, XIAO Jin, ZHOU Jian, LI Zhaohui, YU Zhiqiang, PENG Ping’an
    Earth Science Frontiers    2023, 30 (4): 429-439.   DOI: 10.13745/j.esf.sf.2023.2.70
    Abstract546)   HTML32)    PDF(pc) (3840KB)(404)       Save

    Excessive fossil fuel consumption and land misuse lead to continuous increasing emissions of carbon dioxide and other greenhouse gases, causing a series of environmental problems such as global warming. To effectively control carbon emissions underground carbon storage is developed and it plays an important role in China’s efforts to achieve carbon neutrality while ensuring its energy supplies. Here, we systematically summarize the technical principles and characteristics of typical terrestrial (such as CO2-EOR and CO2-ECBM) and marine carbon sequestration techniques (such as natural gas hydrate sequestration and marine sediment sequestration), and present an overview of China’s carbon emission profile and storage potential, characteristics of domestic carbon-storage pilot projects at different capacities (10000 s to million tons), gaps between China and foreign countries, and main challenges in carbon sequestration. In view of China’s carbon-storage status and goal of carbon peaking/carbon neutrality, we suggest to improve policy support, storage evaluation standards, and relevant laws and regulations, explore suitable storage sites and high-potential areas, strengthen scientific research and access to advanced technology, increase CCS/CCUS infrastructure investments and construction scales, and develop model pilot projects and industrial clusters. As Guangdong Province possesses industrial (trillion ton) carbon-storage potential ahead of carbon peaking, its coastal areas with the greatest carbon storage potential should take the lead in the industrial application of underground carbon-storage technology as well as in the developments of industrial carbon-storage clusters and trillion-ton carbon-storage industry towards achieving China’s carbon neutral target.

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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
    Abstract225)   HTML12)    PDF(pc) (8436KB)(398)       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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    Carbon sequestration, transport, transfer, and degassing: Insights into the deep carbon cycle
    CHEN Xueqian, ZHANG Lifei
    Earth Science Frontiers    2023, 30 (3): 313-339.   DOI: 10.13745/j.esf.sf.2022.12.51
    Abstract442)   HTML30)    PDF(pc) (7116KB)(392)       Save

    Carbon plays a fundamental role in subduction zones in melting enhancement, magma genesis and evolution, and petrological/thermodynamic processes in the deep Earth. The occurrence state of carbon in the deep Earth is controlled by temperature, depth (pressure), oxygen fugacity, and fluid property. When carbon of various occurrence states is transported to the deep Earth via subducting slab and then returns to the atmosphere through degassing, the so-called ‘deep carbon cycle’ is realized. Carbonation/decarbonation reactions are the main mechanisms affecting carbon transfer between the solid Earth, the atmosphere, and the oceans. Carbonation processes include silicate weathering, hydrothermal alteration, trench outer-rise serpentinization, organic carbon burial, and reverse weathering; while carbon transport is achieved by subduction of depositional and metasomatic sediments. Surface carbon, when transported to the Earth’s interior, may be retained within the subducting slab, transferred into the upper mantle wedge, or recycled into the deep Earth depending on the depth and redox state under specific tectonic settings; that carbon is then returned to the atmosphere via decarbonation mechanism through volcanic degassing, diffuse degassing in the forearc, dissolution, metamorphism, and melting to maintain a carbon balance at subduction zones. This systematic review summarizes the carbon occurrence states, carbon movements and change of carbon-bearing phases during carbon sequestration, transport, transfer, and degassing relevant to deep carbon cycling and the related carbon fluxes, analyzes the reasons for the inconsistencies in carbon-flux estimates, and discusses future research directions. Since the industrial revolution anthropogenic CO2 emission has contributed greatly to global warming, exerting extra pressure on Earth as a self-regulating system. In the context of transition to a low-carbon economy, China adheres to energy conservation, carbon emission reduction, and forest growth, and aims to peak CO2 emissions by 2030 and achieve carbon neutrality by 2060 to address the world climate crisis.

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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
    Earth Science Frontiers    2023, 30 (5): 74-92.   DOI: 10.13745/j.esf.sf.2023.5.18
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    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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    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
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    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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    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
    Earth Science Frontiers    2023, 30 (5): 227-243.   DOI: 10.13745/j.esf.sf.2023.5.5
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    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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    Identification of lithium-beryllium granitic pegmatites based on deep learning
    JIANG Guo, ZHOU Kefa, WANG Jinlin, BAI Yong, SUN Guoqing, WANG Wei
    Earth Science Frontiers    2023, 30 (5): 185-196.   DOI: 10.13745/j.esf.sf.2023.5.20
    Abstract187)   HTML16)    PDF(pc) (5555KB)(334)       Save

    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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    Genesis of the Baikal Rift and the Fenwei Graben and the remote effects of the Indo-Eurasian collision
    LIANG Guanghe
    Earth Science Frontiers    2023, 30 (3): 282-293.   DOI: 10.13745/j.esf.sf.2023.1.30
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    The Baikal Rift and the Fenwei Graben are two famous rift systems located in the eastern Eurasian plate, with similar topographic features and geomorphic characteristics. Their tectonic evolution histories are also similar. Many studies have shown that their formation is closely related to the Indo-Eurasian collision, however, the mechanism for this long-range effect is not clear. In this paper, basing on the evolution of extensional tectonics caused by mantle upwelling in the continental margin during the continental drift and continental margin splitting, combined with the Cenozoic tectonic evolution of Eurasia, we studied the evolution of microcontinental fragments and extensional tectonics under the long-range effect. The results show that the origin of the two rift systems is closely related to the Cenozoic large-scale fragmentation and drift of microcontinents in the eastern margin of the Eurasian. Briefly, the Qinghai-Tibet Plateau uplift results in large-scale mantle upwelling and continental breakup in the Cenozoic, where the breakup and drift of the proto-Japan/proto-Kamchatka blocks form a differential sinistral strike-slip environment, and lead to the formation of the two rift systems in two seismic zones on the southeast side of the Siberian and Ordos Basins. These two seismic zones, which have similar genetic mechanisms to the Türkiye earthquake in February 2023, are formed by strike slip faults, and their genetic mechanisms can be reasonably explained by the new continent drift model.

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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
    Earth Science Frontiers    2023, 30 (5): 134-150.   DOI: 10.13745/j.esf.sf.2023.5.16
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    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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    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
    Earth Science Frontiers    2023, 30 (5): 40-58.   DOI: 10.13745/j.esf.sf.2023.5.13
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    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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    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
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    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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    Formation and modification of deep-burial carbonate rocks and orderly distribution of multi-type reservoirs in the Tarim Basin
    FAN Tailiang, GAO Zhiqian, WU Jun
    Earth Science Frontiers    2023, 30 (4): 1-18.   DOI: 10.13745/j.esf.sf.2023.6.5
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    The deep-burial carbonate rocks in China are characterized by great burial depth, old numerical age, and complex geological evolution process. The formation and distribution of carbonate reservoirs, constrained by many factors, are one of the key scientific issues in marine oil and gas exploration. This paper summarizes the results of the team’s long-term research and reveals the main development conditions and orderly distribution of multi-type carbonate reservoirs relevant to the formation and modification of deep-burial carbonate rocks in the Tarim Basin. (1) The platform pattern, stratigraphic development and evolution, and late-stage burial and modification of the basin are all the tectono-sedimentary responses of the basin margin tectonic events. The early Paleozoic basin experienced the evolution process of geomorphic extensional differentiation and formation of small rift groups, geomorphic compression differentiation and interlayer unconformity development, paleo-uplift and large-scale unconformity, multi-stage unconformity superposition and buried modification of paleo-uplift. (2) Complex sedimentary differentiation and evolution (in terms of type and scale) during carbonate platform sedimentation can be divided into embryonic stage, construction stage, heyday stage and decomposition-extinction stage. The corresponding platform margins have undergone the construction process of gentle slope, progradation rimmed, aggradation rimmed and retrogradation steep slope. They control the distribution of sedimentary facies zones favorable for large-scale reservoir development, such as platform margin reef shoals, intraplatform shoals and early dolomitization tidal flats. (3) Multi-level unconformity and fault-fluid modification are important mechanisms for the formation of high-quality reservoirs, where multi-stage regional tectonic activities and periodic sea-level changes control the development of unconformities at different levels, while sequence boundaries dominated by sea-level fall leads to periodic outcropping of carbonate rocks to form interlayer karst and synsedimentary karst of different scales; meanwhile large-scale unconformities formed by regional tectonic movements control the large-scale carbonate outcropping and development of large-scale epigenetic karst reservoirs, as faults and fractures of different scales are not only the reservoir development zones but also the main zones of fluid activity and modification. (4) The size of unconformity and the intensity of fault activity in the Tabei-Shunbei area change gradually from north to south controlling the orderly change of reservoir type and distribution, which result in the sequential developments of, from north to south, buried hill dolomite reservoirs in the Yakla fault convex, paleo-weathered crust karst reservoirs in the main area of Tahe area, stratabound karst reservoirs in the slope area of Tahe, fault karst reservoirs in the covering area of Tahe area, and fault-controlled karst reservoirs in the Shunbei area, reflecting the gradual weakening of unconformity control on reservoirs and strengthening of fault control on reservoirs from denudation area to covering area.

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    A new granitization theory: Discussion on the four-stage granitization theory
    ZHANG Qi, ZHAI Mingguo, WEI Chunjing, ZHOU Ligang, HUANG Guangyu, CHEN Wanfeng, JIAO Shoutao, TANG Jun, LIU Rui, YUAN Jie, WANG Zhen, WANG Yue, YUAN Fanglin
    Earth Science Frontiers    2023, 30 (6): 406-435.   DOI: 10.13745/j.esf.sf.2023.6.11
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    The origin of granite is both an ancient and a frontier scientific problem. One hundred years ago debate on the origin of granite ended with the prevailing view that granite is igneous rather than metamorphic in origin. However, over the past century researchers have shown that the igneous theory is not perfect and the mechanism of basalt crystallization differentiation into granite had been severely challenged. Today it is considered an indisputable fact that granite originated from partial melting of the lower crust, which indicates the source of granite is metamorphic rock. There are many theories on the formation of granites. After many years of testing, the four-stage (melting, melt segregation and ascent, and magma emplacement) theory of granite formation is considered more plausible. Based on detailed study of this theory, this paper proposes a new four-stage theory which divides the granite formation process into two main parts: melt generation and formation (melting and melt aggregation), a heating process, and melt ascent and magma emplacement, a cooling process. The core of this theory is the conjecture of a “lower crustal magma chamber”, which refers to the giant space formed by melt aggregation. This conjecture, first, solves the space problem of a magma chamber in the lower crust. As in situ partial melting of the lower crust only changes the material composition of its products (melt plus remnant), with no space issue involved, the total volume of the lower crust is basically unchanged. And, as there is continuous mantle heating, a lower crustal magma chamber can grow gradually and become very large. Second, we consider the driving force behind magma uplift is not the buoyancy of magma itself. Rather, as the lower crustal magma chamber overflows along the fault zone, the formation pressure from tens of kilometers of strata beneath the magma chamber may transform into great force, driving the magma upward. Therefore, theoretically, granite can rise very quickly, almost instantaneously on the geologic time scale. Third, this conjecture reasonably explains the ancient problem of granite emplacement. It is precisely because the lower crustal magma chamber moves out and ascents, the space it occupied is immediately compacted and filled by the overlying strata, and the subsequence collapse of the underlying strata directly affects the fragile upper crust. A void is then created in the weak part of the upper crustal structure to provide space for the rising magma to complete its emplacement process. Apparently, a space displacement is realized in the disappearing of a magma chamber in the lower crust and magma emplacement in the upper crust. It seems that the concept of a “lower crustal magma chamber” can better resolve many traditional controversies regarding granite formation. The conjecture needs to be verified. Finally, to further study the above issues we suggest using two interdisciplinary approaches-metamorphic-igeous petrology and physical geology.

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    The paleotectonic and paleogeography reconstructions of the Tarim Basin in the Neoproterozoic and prediction of favorable deep source rock areas
    HE Bizhu, JIAO Cunli, LIU Ruohan, CAO Zicheng, CAI Zhihui, LAN Mingjie, YUN Xiaorui, ZHU Ding, JIANG Zhongzheng, YANG Yujie, LI Zhenyu
    Earth Science Frontiers    2023, 30 (4): 19-42.   DOI: 10.13745/j.esf.sf.2022.10.18
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    The tectono-sedimentary development of the Neoproterozoic of the Tarim Basin is important for understanding the basin initiation process and for the regional ultra-deep/deep oil and gas exploration. Due to the deep burial and data scarcity, it is extremely difficult to research the deep buried areas of the basin, and data interpretation can be ambiguous. This study, based on comprehensive analyses of drilling data and newly reprocessed seismic reflection data collected across the basin, reveals that the Tarim Basin experienced at least three tectonic cycles during the Neoproterozoic and developed three super stratigraphic sequences and 7-9 stratigraphic sequences. The distribution of sedimentary facies of the Neoproterozoic in the basin and its margin vary greatly, constrained obviously by Neoproterozoic rift depressions. The basin developed shelf facies, glacier facies, basin facies, carbonate platform facies, tidal-flat facies, fan-delta facies, littoral and shallow sea facies, alluvial-fluvial facies, and igneous rock facies. Results on the structural architecture and spatial distribution of unconformities during the Cryogenian-Early Cambrian reveal that the tectono-sedimentary frameworks of the basin margin and deep buried area are formed in an extensional environment. The main unconformity types include angular unconformity with low-angle and monocline structures, progressive syntectonic angular unconformity, fault-controlled unconformity, and paraconformity, and they are observed in every rift depressions and at different locations. The paleotectonic and paleogeography of the basin before the deposition of the Ediacaran and the Cambrian are reconstructed based on sequence stratigraphy, Neoproterozoic fault activity, unconformity architecture, seismic stratigraphy, and wave impedance inversion property data, which show that the distribution of various sedimentary facies zones is related to the developments of rift depressions and subsidence centers and the differences of structural deformations. In response to the subduction-related outgrowth and the breakup of Rodinia, and the assembly of Gondwana, the Tarim Basin experienced three evolutionary cycles in the Neoproterozoic: initiation of deep rift depressions (900-760 Ma), development of deep rift depressions (~750-630 Ma), and rapid extensions and declining of rift depressions (630-520 Ma). Correspondingly, the Tarim block underwent subduction-related back-arc extension, continental rift, and passive continental margin transformations during the Neoproterozoic. The Ediacaran to Cambrian transition is an important period where the Tarim block transformed from continental-rift/rift-depression basins into a unified cratonic basin. This is evidenced by the unconformity between the Cambrian and the Ediacaran or pre-Ediacaran across the basin and covered by the Lower Cambrian further. Here, a new method is developed to reconstruct paleotectonic and paleogeographic history of deep buried basins based on structural and multi-attribute analyses. Besides, the favorable development areas of Lower Cambrian-Upper Cryogenian source rocks are predicted according to structural and sedimentary facies constrains, which has great significance for the evaluation of deep oil and gas resource potential in the basin.

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