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    Critical minerals in China: Current status, research focus and resource strategic analysis
    LI Wenchang, LI Jianwei, XIE Guiqing, ZHANG Xiangfei, LIU Hong
    2022, 29(1): 1-13. 
    DOI: 10.13745/j.esf.sf.2022.1.25

    Abstract ( 2372 )   HTML ( 145 )   PDF (2298KB) ( 1446 )  

    Critical minerals are essential to sustainable development and in high demand in modern society. They are, however, subject to high risks due to limited quantity, uneven geological/geographical distribution, geopolitics, trade policy, and other factors. Critical minerals refer mainly to rare earth elements, rare metals, valuable constituent element dispersed in a mineral commodity, and some precious metals (e.g., platinum-group elements). The critical metals have unique physical and chemical properties (e.g., extreme high temperature resistance, corrosion resistance, excellent optical and electromagnetic properties, etc.), making them vital for the high-technology industries, emerging economies, advanced defense systems, green technologies, new energy, artificial intelligence, etc. It is predicted that global demands for critical metals will grow rapidly in the next decades, and the conflict between supply and demand will become increasingly prominent. Future international competition for mineral resources will largely involve critical metals. China has been the main consumer of mineral resources in the last decade, and its demand for critical minerals will continue to grow for a long period. The continuing high demand and increasingly stronger competition highlight the urgent needs for innovative multidisciplinary research in metallogeny, exploration, and utilization of critical minerals. China hosts a large variety of critical minerals with diverse mineralization styles; they are distributed as clusters or belts and formed by complicated geochemical processes under favorable geological settings. To advance our understanding of the genesis of critical minerals, we suggest three key issues for future studies: (1) partition and transportation of critical metals in the processes of interaction between Earth’s spheres; (2) mechanisms for unusual enrichment of critical metals in magmatic, hydrothermal, and supergene systems, as well as controls on temporo-spatial distribution of related ore deposits; and (3) mode of occurrence and technologies towards efficient, green extraction of critical metals from various minerals and ores. Based on the analysis of current situation and future trend of supply-demand for critical minerals, suggestions on improving mineral exploration, economic utilization, management policy, and resource security strategy for critical minerals in China are proposed.

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    Rare earth mineralization in Bayan Obo super-large deposit: A review
    DENG Miao, WEI Chunwan, XU Cheng, SHI Aiguo, LI Zuoqi, FAN Chaoxi, KUANG Guangxi
    2022, 29(1): 14-28. 
    DOI: 10.13745/j.esf.sf.2021.8.9

    Abstract ( 821 )   HTML ( 56 )   PDF (12121KB) ( 727 )  

    Rare earth elements (Y, Sc, La-Lu), the “vitamins” of modern industry, are regarded as critical strategic resources in today’s society. The Bayan Obo REE-Nb-Fe deposit located in Inner Mongolia, China, is the world’s largest rare earth deposit. The diagenesis and mineralization processes of this deposit have attracted a great deal of attention from geologists around the world, and a considerable amount of research has been conducted. These researches were mainly focused on the whole-rock chronology and geochemistry of H8 ore-bearing dolomite rock, which, however, led to confusions over different metallogenic models as the deposit has rather complex ore texture and structure due to late stage deformation and metamorphism. In recent years, with the rapid technological development in modern geochemical analysis, high-precision in-situ isotopic analysis and in-situ U-Th-Pb dating can be performed directly on dolomite and rare earth minerals (such as monazite, apatite, bastnasite, etc.), which yielded valuable information on the age of the deposit as well as the source of ore-forming fluids. This paper summarizes the latest research results on the diagenesis and metallogenic model of the world class Bayan Obo REE-Nb-Fe deposit, and proposes that Mesoproterozoic (1.3 Ga) carbonatitic magmatism initiated REE mineralization and Early Paleozoic metasomatism subsequently caused REE reenrichment and reprecipitation which resulted in the accumulation of large amounts of REE minerals to form the Bayan Obo deposit.

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    Mineral surface reaction constraints on the formation of ion-adsorption rare earth element deposits
    LIANG Xiaoliang, TAN Wei, MA Lingya, ZHU Jianxi, HE Hongping
    2022, 29(1): 29-41. 
    DOI: 10.13745/j.esf.sf.2021.8.8

    Abstract ( 460 )   HTML ( 19 )   PDF (4063KB) ( 389 )  

    The ion-adsorption rare earth element (IAR) deposits in South China produce more than 90% of the world’s heavy rare earth elements (HREEs). They are a key strategic metal resource of China. Thus, a better understanding of the metallogenic mechanism and resource characteristics of IAR deposits can provide a theoretical basis for increasing REE reserves and better utilization of REE resources. The IAR deposits are mainly developed in the weathering crusts of REE-rich granite, epimetamorphic and volcanic rocks. The REE-bearing minerals in protolith are the main sources of REE cations in weathering crust, where mineral association greatly determines the concentration and fractionation characteristics of REEs. Under physical/chemical weathering and microbial action, the dissolution of rock-forming minerals, REE-bearing minerals and REE minerals results in the activation and re-enrichment of REEs. On one hand, weathering of protolith produces clay minerals and Fe-Mn (hydr)oxides with a large specific surface area and high surface charge density. On the other hand, these secondary minerals can adsorb REE cations via ion exchange, surface adsorption/complexation or formation of secondary REE minerals. The adsorption mechanism, enrichment-fractionation characteristics and occurrence state of REEs are affected by mineral types, pH and microbial activity. By using high-resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS) and synchrotron radiation X-ray absorption fine structure spectroscopy (XAFS), the atomic occurrence state of REEs can be determined. In the future, more attention should be paid to research areas including the association of REE-bearing minerals in protoliths and its evolutionary pathway and mechanism, the constraints of microbial weathering on the formation of IAR deposits, and the microscopic occurrence state of REEs.

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    Extraction, characterization and occurrence state of REE-bearing nanoparticles from granite-derived regolith
    YI Zebang, FU Wei, ZHAO Qin, XU Cheng, LU Jipu
    2022, 29(1): 42-53. 
    DOI: 10.13745/j.esf.sf.2021.8.2

    Abstract ( 270 )   HTML ( 16 )   PDF (6808KB) ( 312 )  

    Characterization of REE in nanoparticles extracted from regolith is important for revealing the genesis of regolith-hosted REE deposits in South China. In this study, we used both physical (MilliQ water, MQW) and chemical (Na4P2O7, TSPP) techniques to extract nanoparticles (1-100 nm) from the profile of REE-enriched granite-derived regolith in Pingnan, Guangxi. Hollow fiber flow field-flow fractionation and inductively coupled plasma mass spectrometer (HF5-ICP-MS) were used to separate and characterize the nanoparticles continuously from regolith and simultaneously obtain the particle size distribution. We show that the chemical dispersant can efficiently break up large-size nanoparticle aggregates and achieve much higher (102-103 times) extraction efficiency compared to the physical extraction method, with ~80.5% REE extracted from regolith. The particle size mostly ranged between 2-5 nm and 10-30 nm, and some between 30-80 nm. In 2-5 nm nanoparticles, the REE peak position was closely related to organic matter macromolecules, indicating the association of the two, via ionic interactions; whereas in 10-30 nm nanoparticles, the REE peak position was almost identical to Al element, indicating REE association with clay minerals, via adsorption or ion exchange. Furthermore, the size distributions of light (LREE) and heavy (HREE) REEs in nanoparticles differed. LREEs, represented by La, Ce, Pr and Nd, were mostly in 2-5 nm and 10-30 nm nanoparticles; whereas HREEs, represented by Tb and Lu, were also in 30-80 nm particles, indicating there are other HREE source besides clay mineral and organic matter from regolith. The findings of this study provide new insights into the occurrence states as well as enrichment/differentiation process of REEs in regolith-hosted REE deposits.

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    Current research progress and emerging trends in experimental study of mineralized carbonatite
    YANG Daoming, PAN Ronghao, WANG Meng, HOU Tong
    2022, 29(1): 54-64. 
    DOI: 10.13745/j.esf.sf.2021.8.3

    Abstract ( 353 )   HTML ( 18 )   PDF (4213KB) ( 393 )  

    Carbonatites and their surface weathering products constitute the main source of strategic metals, such as REE and Nb. Thus it is of great scientific significance to understand the extraordinary enrichment mechanism of strategic elements in carbonatites. Previous studies show that the mineralized carbonatites are closely associated with alkaline complex, indicating the parent magma is carbonated silicate magma which is dominated by carbonated nephelinite. Some experiments showed that both immiscibility and fractional crystallization could lead to carbonatite formation during the crustal evolution of parent magma. However, multicomponent experiments have clearly shown that liquid immiscibility always occurs prior to fractional crystallization of carbonate minerals, and thus immiscible separation of carbonatite from silicate melts plays an important role in the mineralization of strategic metals in carbonatites. However, in contrast to the fact that REE and Nb are naturally hosted in carbonatite, the immiscibility experiments showed that the strategic metals (REE and Nb) are preferentially partitioned into the silicate melt (alkaline silicate rocks). Although the partition coefficients of REE and Nb in carbonate-silicate melt is dependent on the water content, i.e., the degree of polymerization of the melt, the mechanism by which strategic metal elements (REE and Nb) are extremely enriched in carbonatites is enigmatic as the formation of mineralized carbonatites is mostly under anhydrous condition. Therefore, in order to elucidate the key controlling factors for the mineralization of critical metals in carbonatite, further studies should focus on whether other ligands, in addition to water, may influence the partition coefficient of critical metals between the immiscible carbonatitic and nephelinitic melts.

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    The Xiwukou Rb deposit in the Jiangnan uplift belt, Ningguo City, Anhui Province: Rb occurrence and ore-forming mechanisms
    CHEN Xuefeng, FAN Yu, ZHOU Taofa, YU Jianghua, QIAN Shilong, LU Zhongqiu, YANG Zhangyi, HONG Jianmin
    2022, 29(1): 65-80. 
    DOI: 10.13745/j.esf.sf.2021.8.4

    Abstract ( 242 )   HTML ( 8 )   PDF (10673KB) ( 387 )  

    The Xiwukou rubidium (Rb) deposit—a granite-related ore deposit—is the first discovered Rb deposit in the Jiangnan uplift belt, Ningguo City, Anhui Province. Two spatially distinct orebodies, type-Ⅰ and type-Ⅱ, developed in the Xiwukou deposit. The type-Ⅰ orebody is hosted in granite porphyry, and the type-Ⅱ is at the top of the granite porphyry. The mineral combinations are all phengite + quartz, but ore grade is higher in type-I (0.25%) than in type-Ⅱ (0.21%) orebody. Previous researches had focused on the mineralization characteristics, chronology, petrogenesis, and magmatic source, but the mineral occurrence status of Rb and the metallogenic mechanism in the Xiwukou deposit are still unclear. In this study, we used electron probe analysis and LA-ICP-MS to characterize the granite porphyry-hosted plagioclase, K-feldspar and biotite and phengite in the type-Ⅰ, Ⅱ orebodies. We found that the average Rb contents in plagioclase, K-feldspar and biotite, formed in the early stage, were 3.10 × 10-6, 872 × 10-6 and 1 328 × 10-6, respectively; while in phengite, formed in the late stage, the Rb contents were 2544 × 10-6 and 2686 × 10-6 in type-I and type-II orebodies, respectively. The stoichiometric calculation results show that Rb+ is incorporated into phengite through isomorphism replacing K+ and Na+. Combining the geological characteristics of the deposit with comparative analysis of regional igneous rocks, we propose the following ore-forming mechanism for the Xiwukou Rb deposit: The Rb background value and fluorine content in the ore-forming magmatic fluids was fairly high, and mineral crystallization led to further Rb enrichment in the residual magma. During the transition stage from magma to hydrothermal fluid, the high fluorine condition caused a structural change in silicate, from a framework to layered structure, which facilitated large-scale crystallization of Rb-rich phengnite to form Rb-rich orebody.

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    Solubility of rare metals as a constraint on mineralization of granitic pegmatite
    TANG Yong, QIN Shanxian, ZHAO Jingyu, LÜ Zhenghang, LIU Xiqiang, WANG Hong, CHEN Jianzheng, ZHANG Hui
    2022, 29(1): 81-92. 
    DOI: 10.13745/j.esf.sf.2021.8.7

    Abstract ( 266 )   HTML ( 7 )   PDF (5005KB) ( 403 )  

    Granitic pegmatite deposit is one of important types of rare metal deposits. In the granitic pegmatite, the rare metals Li, Be, Nb and Ta mainly occur in mineralogically distinct zones. Their solubilities in silicate melts have been studied systematically and shown to be mostly affected by temperature (T) and aluminum saturation index (ASI). Here we set out to establish quantitative relationships between T/ASI and the solubility of rare metal minerals (Nb and Ta) in silicate melts by multiple linear regression analysis of literature data. We found the following relationships:
    lgc(Li) (10-6)=-0.37×(1000/T)+4.56, R2=0.44
    lgc(BeO) (10-6)=-4.21×(1000/T)+6.86, R2=0.91
    lgKsp(Nb)=-(2.86±0.14)×ASI(Mn+Li)(4.95±0.31)×(1000/T)+(4.20+0.28), R2=0.86
    lgKsp(Ta)=-(2.46±0.11)×ASI(Mn+Li)(4.86±0.30)×(1000/T)+(4.00+0.30), R2=0.80
    Where c is percentage content; Ksp is solubility, in mg 2/kg2; ASI(Mn+Li) is the molar ratio Al2O3/(CaO+Na2O+K2O+Li2O+MnO), applicable between 0.6-1.2; and T is temperature of silicate melt in Kelvin, applicable between 1073-1373 K. These quantitative relationships can be used as a basis for quantifying the metallogenic model of granitic pegmatite. The sharply decrease of solubility with decreasing T and increasing ASI can be the main mechanism leading to the crystallization of rare metal minerals, because the same conditions are met during magma evolution, where magma emplacement, fractional crystallization and fluid-melt interaction cause increase of magma temperature and decrease of ASI.

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    Geological characteristics of and prospecting strategy for the Xianglin Be-Sn polymetallic ore deposit in the Cuonadong gneiss dome in southern Tibet
    XIA Xiangbiao, LI Guangming, ZHANG Linkui, ZHANG Zhi, CAO Huawen, LIANG Wei
    2022, 29(1): 93-106. 
    DOI: 10.13745/j.esf.sf.2021.8.30

    Abstract ( 279 )   HTML ( 18 )   PDF (15825KB) ( 241 )  

    The Cuonadong gneiss dome, a newly discovered dome in the North Himalaya Gneiss Domes (NHGD) belt, is composed of three parts: core, mantle, and outer layer. They are composed of Cambrian granitic gneiss, Early Paleozoic mica schist and skarn marble, and metamorphic sedimentary rocks, respectively, and leucogranites and scores of pegmatite veins intrude into the core of the Cuonadong gneiss dome at a later stage. The Xianglin Be-Sn polymetallic ore deposit is located in the northern Cuonadong gneiss dome. A number of north-south and east-north extensional faults are developed in the mining area. The Be-Sn polymetallic orebodies were newly discovered through systematic surface exploration engineering in the mantle layer around the core of the dome and fault fracture zones. The anatomy of a typical mining area in the northern Cuonadong dome shows four types of ore bodies: skarn, cassiterite-quartz vein, cassiterite-sulfide, and granite pegmatite. Skarn type ore bodies occur in skarn marble in the mantle; mineralized is dominated by Sn, Be and W; Sn ore grade is relatively low. Cassite-quartz vein type ore bodies are controlled by NE extensional fracture; mineralization is dominated by Sn, Be and W; ore grades are relatively high. Cassite-sulfide orebodies are controlled by the interlayer slip structure in marble; Sn ore grade is high but Be and W ore grades are low. Mineralization in pegmatite is mainly Be, accompanied by Rb. Verified at great borehole depth, we found the deep extension of all types of ore bodies except pegmatite is relatively stable. Based on the study of the relationship between magma and Be-Sn polymetallic mineralization, we reveal that there are two stages of mineralization in the Xianglin mining area, and the mineralization is closely related to the weakly oriented two-mica granite and muscovite granite. Based on orebody characterization we developed a ore prospecting strategy. The main targets in future ore exploration will be cassite-sulfide and cassite-quartz vein type ores as they are relatively rich in Be, Sn and W.

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    Genesis of lithium brine deposits in the Jianghan Basin and progress in resource exploration: A review
    YU Xiaocan, LIU Chenglin, WANG Chunlian, XU Haiming, ZHAO Yanjun, HUANG Hua, LI Ruiqin
    2022, 29(1): 107-123. 
    DOI: 10.13745/j.esf.sf.2021.8.11

    Abstract ( 949 )   HTML ( 29 )   PDF (9461KB) ( 542 )  

    During the Paleogene, saline lakes developed in the Qianjiang and Jiangling Sags, Jianghan Basin, where thick evaporites later deposited to produce rich brine resources that contain industrial or general commercial grade Li, K, Rb, Cs, Br, and I elements. The Li-rich brines, belonging to deep underground lithium brine deposits, are a high-quality lithium resource, with low Mg/Li ratios. In this paper, the geotectonic feature, igneous rock and paleoclimatic background associated with the Jianghan Basin are summarized; the sedimentary facies of ancient salt lakes, the hydrochemistry, distribution and characteristics of lithium brine reservoirs, also the source and enrichment mechanism of lithium in brines, the formation model of lithium brine deposits, and progress in lithium brine exploration and mining technology are introduced; and the problems and solutions in the development and utilization of brines are discussed. The genesis of lithium brines in the Jianghan Basin is as follows: lithium, likely, comes mainly from the replenishment of Li-rich hydrothermal fluids produced by water-rock interaction at high temperature. In an arid climate, saline lake continues to evaporate and concentrate, leading to lithium enrichment in brines. At the end of salt lake evolution, the gradually buried intercrystalline Li-rich brines in saline minerals migrated to fractures, sandstone and basalt reservoirs for storage, where brine-reservoir rock interaction in geothermal environment further promotes lithium enrichment. Preliminary surveys of deep brines in the Jianghan Basin predicted large industrial scale LiCl resources in the basin with great resources potential. As lithium brine mining technology is maturing, researches on green technology development should be strengthened, and relevant exploration and development standards should be established.

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    Extreme enrichment and ore-forming mechanism of main mafic magma-related platinum group element deposits in western China
    ZHANG Mingjie, ZHANG Hongfu, LIANG Kaikang, ZHANG Xiaoqi, LI Si’ao, ZHANG Junwei, BAN Shuyue, WANG Ronghua, FAN Yuxin
    2022, 29(1): 124-142. 
    DOI: 10.13745/j.esf.sf.2021.8.14

    Abstract ( 316 )   HTML ( 14 )   PDF (4266KB) ( 300 )  

    Neoproterozoic mafic magmatism in western China produced a number of platinum group element (PGE) deposits in different geological time and tectonic geodynamic settings, including the Neoproterozoic Jinchuan Ni-Cu-PGE sulfide deposit located in southwestern margin of the North China Craton, and the Jinbaoshan PGE deposit, a member of the Permian Emeishan large igneous province (LIP) in southwestern China. PGEs as siderophiles are more enriched in the Earth’s core than in the mantle and crust. Therefore, they can be transported into the crust by mantle-derived magma as elemental nanoclusters, alloy or immiscible sulfide melt, and their concentration in the magma tends to increase with the depth and degree of partial melting in the mantle source. PGE-bearing sulfide and other minerals in the magma can be concentrated gradually in the magma chambers and associated conduits through a multi-stage process, and form economically valuable multi-type PGE deposits. The subcontinental lithospheric mantle (SCLM) beneath the North and South China Cratons has higher PGE contents than the primitive mantle. The concentration of PGEs in the SCLM of the North China Craton may also decrease from the Palaeozoic to Cenozoic, indicating some PGE extraction magmatisms. Neoproterozoic mafic magmatism in western China is a plausible mechanism of PGE mineralization, as inferred from PGE-rich mantle (plume) source, high PGE content in mantle-derived magma, long-lived magmatic activity as well as multi-stage PGE extreme enrichment by magma-sulfide interaction. A better understanding of the geodynamic settings and mineralization processes in PGE deposits is important for assessing PGE mineralization potential in the region and finding more PGE resources in China.

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    Structural control and metallogenic mechanism of the Daliangzi Ge-rich Pb-Zn deposit in Sichuan Province, China
    KONG Zhigang, ZHANG Binchen, WU Yue, ZHANG Changqing, LIU Yi, ZHANG Feng, LI Yanglin
    2022, 29(1): 143-159. 
    DOI: 10.13745/j.esf.sf.2021.5.1

    Abstract ( 239 )   HTML ( 20 )   PDF (17210KB) ( 255 )  

    The Daliangzi large Ge-rich Pb-Zn deposit is located in the Sichuan-Yunnan-Guizhou (Chuan-Dian-Qian) Pb-Zn metallogenic belt on the western margin of the Yangtze block. It contains 4.5 million tons of ores, 10%-12% of which are Pb-Zn ores. The pipe- and vein-like Pb-Zn ore bodies are hosted in well developed fault-controlled black breccia zones that cut through the ore-hosting dolostone of the Sinian Dengying Formation. The NWW-, NW- and NE-trending faults are well developed in the mining area, and their activity and tectonic dynamics are clearly defined through detailed analysis of the geometric and kinematic features of these faults. The NWW-striking thrust faults were formed by N-S compressive stress prior to mineralization. During the ore-forming process, due to the subduction of the Paleo-Tethys Ocean and the late Indosinian orogeny, the regional tectonic stress field was transformed into NW-SE compressive stress, and then the NWW-trending tensional and torsional faults, NW-trending tensional faults and NE-trending reverse faults were formed in the sutdy area. After mineralization, the regional tectonic stress field changed to near E-W direction, causing the formation of the NWW-, NW- and NE-trending faults that cut through and/or dislocated the ore bodies. The NWW-trending faults are the major ore-controlling faults, possibly acting as the migration pathway for the ore-bearing fluid. The NW-trending faults are the secondary main faults in the mining area, where hydrothermal fluid mixing and orebody emplacement took place. The distinct ore-controlling structure in the Daliangzi Ge-rich Pb-Zn deposit is the negative flower structure consists of the NWW- and NW-trending faults. The main metallogenic mechanism of this deposit is the mixing of two fluids-the mineral-rich deep fluid and the reduced fluid from the Cambrian organic-rich strata-under tensional stress from the NWW- and NW-trending faults. Areas with similar tectonic patterns, such as the southern and western mining area, are the next prospecting target.

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    Geochemical composition and paleoceanic environment of the Lower Cambrian black shale-hosted Qianjiaping vanadium deposit in the southern Qinling Region
    XU Lingang, FU Xuerui, YE Huishou, ZHENG Wei, CHEN Bo, FANG Zhenglong
    2022, 29(1): 160-175. 
    DOI: 10.13745/j.esf.sf.2021.8.13

    Abstract ( 323 )   HTML ( 11 )   PDF (12097KB) ( 434 )  

    The Qianjiaping vanadium (V) deposit is a typical Lower Cambrian black shale-hosted V deposit in the Southern Qinling Region. Vanadium mineralization in the Qianjiaping deposit mainly occurs in multilayered cherts with carbonaceous shale in the 1st member of the Shuigoukou Formation. To better understand the origin of vanadium and redox environment in Early Cambrian seawater in South Qinling, we report in this study the bulk geochemical compositions of the V-rich carbonaceous shale from the 1st member and the overlying muddy limestone from the 2nd member of the Shuigoukou Formation. The Y/Ho ratio is higher in the multilayered chert-mudstone samples than in the muddy limestone samples, indicating a dominant authigenic origin for V in the 1st member, whereas in the 2nd member V may be mostly derived from detrital components. Discrimination plots, Eu/Eu*-V, Y/P2O5-Zr/Cr and Fe/Ti-Al/(Al+Fe+Mn), suggest V mineralization is mainly by precipitation from ambient seawater, while hydrothermal fluids plays a minor role. All samples showed negative Ce anomaly, ranging from 0.26-0.96. Together considering the comparatively high Mo/Sc, V/Sc, V/Cr and low Th/U ratios in the 1st member, we infer a redox stratified ocean during the early Early Cambrian in the Southern Qinling Region, which became entirely oxygenated during the late Early Cambrian.

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    Metallogenic patterns and ore deposit model of the tin polymetallic deposits in the southern segment of Great Xing’an Range
    ZHOU Zhenhua, MAO Jingwen
    2022, 29(1): 176-199. 
    DOI: 10.13745/j.esf.sf.2021.8.12

    Abstract ( 385 )   HTML ( 18 )   PDF (5110KB) ( 400 )  

    The tin polymetallic ore belt of southern Great Xing’an Range (SGXR) is the most important tin ore belt in northern China. Here, aiming to promote regional tin/silver prospecting, we systematically summarized the spatiotemporal distribution and metallogenic characteristics and proposed the deep dynamics and metallogenic models of the tin polymetallic deposits in SGXR. These deposits were formed in an extensional environment, with obvious spatial and temporal aggregation characteristics. They are located between the Erlian-Hegenshan, Huanggang-Ganzhu’ermiao and Xilamulun fault zones and formed mostly between 150-130 Ma, although multi-stage mineralization likely occurred in some large and medium-sized ore deposits. Even though tin mineralization is extensive, few highly differentiated ore-bearing granites are exposed so far, due probably to high background of ore-forming elements in the area, but also likely they are hidden in the depth. The tin polymetallic ore is mainly composed of tin, lead, zinc and silver, with few concurrent or accompanied tungsten mineralization. Multi-stage, multi-type mineralization is a result of multi-stage magma extrusion from a deep magma chamber, which produced ore-forming fluids with similar or different properties. Meanwhile, reactions between ore-forming fluids and surrounding rocks could also affect the fluid composition and evolution. Magma fluid exsolution, stratigraphic activation and extraction, mantle material, atmospheric precipitation, hot brine and metamorphic hydrothermal fluid all played a part in mineralization. Especially in the high temperature, low pressure environment, deep mafic magma degassing not only provided heat source for the mineralization, but also might provide an abundance of ore-forming element and volatile component. During the mineralization process, the main contributing factors for the super enrichments of metal elements were decreasing fluid temperature/pressure, mixing of fluids from different sources, immiscibility of supercritical fluids, multiple boiling of the fluids and water-rock interaction.

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    Antimony mineralization and prospecting orientation in the North Himalayan Metallogenic Belt, Tibet
    ZHENG Youye, WANG Da, YI Jianzhou, YU Zezhang, JIANG Zongyang, LI Xiaoxia, SHI Gongwen, XU Jian, LIANG Yuchun, DOU Xiaofang, REN Huan
    2022, 29(1): 200-230. 
    DOI: 10.13745/j.esf.sf.2021.8.5

    Abstract ( 391 )   HTML ( 18 )   PDF (25713KB) ( 315 )  

    The North Himalayan Metallogenic Belt (NHMB), a global geological hotspot, is an important component of the Tethys-Himalaya Metallogenic Domain. It consists a series of mineral deposits, mainly Sb, Sb-Au, polymetallic Sb, Au, Pb-Zn(Ag), W-Sn(Be), Hg and Cs ore deposits or occurrences. The Sb ore-forming ages are concentrated between 16-24 Ma, coinciding with the post-collisional orogeny metallogenic event N1 (25-9 Ma). Sb is sourced from subvolcanic magmatism which involves rich volatiles formed from decompression and fusion of hypomagma and is responsible for the development of exhalative sedimentation-reworked, magmatic hydrothermal and hot spring deposits. Thus, the mantle-sourced basic-intermediate dykes within orefield are an important control factor and prospecting indicator for Sb mineralization. Sb anomaly is detected along the edge of the Yangzhuoyongcuo rift basin overlapping partially with Au anomaly. Sb anomaly is mainly associated with epithermal deposits where Sb can mineralize separately or intergrow with Au; when Sb anomaly overlaps with Pb-Zn-Ag anomalies, Sb deposits are usually formed from later stage superposition-reformation and associated with Ga-Se-In mineralization. Sb and polymetallic Sb orebodies are nearly SN-trending in forming toruloid geochemical anomalous and mineralization assemblages. They are controlled by strike slip normal fault system and its secondary structures; moreover, in the eastern part of the ore belt, mineralization occurs from north to south in a pattern of Sb → Au-Sb → Au → Sb-Pb-Zn-Ag → W-Sn, indicating the mineralization center lies in the deep or southern part of the Zhaxikang deposit. By contrast, Au and Au-Sb orebodies are nearly EW-trending and controlled by detachment and its secondary structures. The basin-mountain transition region along Mesozoic rift basin in the North Himalayan passive continental margin, specially the intersection area of syndepositional fault zone and Cenozoic SN-trending graben structures, is the key region for ore prospecting, where a series of large and super-large deposits have been discovered, including the Zhaxikang polymetallic Sb deposit—the largest deposit of its kind within the Tethys-Himalayan Metallogenic Domain. To sum up, the NHMB will become one of the most important reserve bases for antimony resources exploration and development in China.

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    High purity quartz: Research progress and perspective review
    YANG Xiaoyong, SUN Chao, CAO Jingya, SHI Jianbin
    2022, 29(1): 231-244. 
    DOI: 10.13745/j.esf.sf.2021.8.1

    Abstract ( 1459 )   HTML ( 122 )   PDF (5057KB) ( 1101 )  

    Quartz is widely distributed on the Earth’s surface. It has a broad range of industrial uses and other application prospects. Natural quartz, however, are not entirely SiO2 but contain other elements more or less, such as P, Ti, Ge, Al, B, Be, Ca, Na, K, H, and Li, affected by the physico-chemical conditions/properties of crystallizing melt or fluid as well as post-crystallization alterations (such as metamorphism, structural deformation, and thermal disturbance). Diagenetic study of quartz based on its trace element compositions plays a part in petrological and metallogenic investigations of mineral deposits. The impurity elements in quartz are in forms of lattice impurities or nano- to macro-scale inclusions, and the impurity type, quantity, and form (specially inclusions) affects the quality and industrial use of quartz directly. Here, topics including the luminescent properties and technical performance of quartz, quality classification and rating standard for high purity quartz, source materials of high purity quartz are systematically reviewed. Also, the distribution of fluid inclusions and types of mineral inclusions in quartz from the Zhangjinzhuang quartz sand (Northern Jiangsu) and Guposhan granite (Guangxi) were determined in this study by optical microscopy observations and laser Raman analysis to provide a basis for subsequent research. High purity quartz of high quality and value is naturally formed (such as crystal) or processed from high quality quartz raw materials. It is an environment-friendly strategic resource used in high-tech industries, such as semiconductor, high-temperature lamp tubing, fiber optics, precision optics, microelectronics, and solar energy. Researches on the evaluation system, ideal source rock and formation mechanism for high purity quartz raw materials are beneficial for ensuring a sustainable supply of high purity quartz raw materials and increasing the added value of quartz products.

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    A spacial section on The India-Eurasia Collision and Its Long-Range Effect
    Active faulting along the western boundary of the Amur plate (territory of Mongolia)
    Vladimir A. SANKOV, Anna V. PARFEEVETS, Andrey I. MIROSHNITCHENKO, Aleksey V. SANKOV, Amgalan BAYASGALAN, Sodnomsambuu DEMBEREL
    2022, 29(1): 245-265. 
    DOI: 10.13745/j.esf.sf.2021.12.16

    Abstract ( 560 )   HTML ( 17 )   PDF (10891KB) ( 149 )  

    The spatial position of the western boundary of the Amur plate within the territory of Mongolia is still not clear; active fault tectonics and the stress state of the Earth’s crust along it have been poorly studied. Within three regions along this border—the Hangay-Khentiy tectonic saddle, the Burgut block (Orhon-Tola interfluve) and the Selenga block, which includes the Selenga depression and the Buren-Nuruu uplift, studies of active faults were carried out using space imagery interpretation, relief analysis, geological structural data and reconstruction of tectonic paleostresses from tectonic fracturing and displacement along with fractures data. It is shown that active faults inherit ancient structural heterogeneities of the Paleozoic and Mesozoic ages. The faults do not form a single zone along the plate boundary, but form clusters. Their kinematics depend on the strike: sublatitudinal faults are left-lateral strike-slip faults with an obligatory reverse component; NW-strike faults are reverse faults or thrusts, most often with a right-lateral strike-slip component; submeridional faults are right-lateral strike-slip faults; and NE-strike faults are normal faults. The activation of fault structures localized in the Selenga depression and in the eastern part of the Hangay began in the Pliocene. Revers and strike-slip faults are not conformal to the Pliocene, and often to the Pleistocene relief, which indicates a younger, Late Pleistocene, age of their activation. Reconstructions of the stress-strain state of the last stage of deformation in zones of active faults, using tectonic fracturing and displacements along fractures, indicate the predominance of compression and strike-slip conditions with the N-NE and NE direction of the axis of maximum compression. Only within the Selenga depression is the prevalence of stress tensors of extension and strike-slip types with the NW strike of the axis of minimum compression noted. To the south, a local area with a predominance of the extension regime is located within the Eastern Hangay (Orhon graben). It is concluded that the activation of faults in the central part of Mongolia at the Pleistocene-Holocene stage, as well as modern seismicity, are mainly controlled by additional horizontal compression in the NE direction associated with the process of convergence of Hindustan and Eurasia. An additional factor that allows the implementation of strike-slip deformations in the crust of the study area and explains the divergent movements in the Baikal Rift, as well as the SE movement of the Amur plate, is the impact on the base of the lithosphere of the asthenospheric flow in the SE direction. The boundary between the Amur plate and the Mongolian block in the tectonic structure is expressed fragmentarily and represents the marginal part of the deformation zone covering the whole of Western Mongolia.

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    Structural characteristics of the Nima Basin in the Bangong-Nujiang tectonic belt, central Tibet
    ZHONG Linglin, ZHONG Kanghui, QIN Qin, YAN Zhao, YANG Xiong, HE Zhiyuan, ZHANG Hongjie, PENG Jie, Johan De GRAVE, Stijn DEWAELE, ZHOU Huiwen, HE Xingjie, HAN Wenwen, GONG Xiaobo, YANG Hairui, DONG Suiliang, CHANG Yupeng, LI Kaizhi, DOU Jie, LI Lin, HE Mingfeng, LIU Yilong
    2022, 29(1): 266-284. 
    DOI: 10.13745/j.esf.sf.2021.11.45

    Abstract ( 340 )   HTML ( 26 )   PDF (23781KB) ( 225 )  

    The Neo-Tethyan subduction and subsequent India-Eurasia collision resulted in significant contractional deformation of the continental lithosphere and the uplifting of the Tibetan Plateau. Revealing the formation mechanism and process of giant fracture zone in Tibet is crucial for understanding the propagation of the deformation toward the hinterland of the Eurasian continent. Several continental basins of Cretaceous-Cenozoic age developed along the Bangong-Nujiang suture zone, providing a splendid record of the tectonic-sedimentary evolution of the central Tibet. So far, competing geodynamic models are proposed to explain the structural characteristics and the formation of these basins, including strike-slip faulting, extensional rifting and foreland flexural depression. The key to testing these models includes (1) fully documenting the structural characteristics of the basin basement and sedimentary infills and (2) clarifying the structural evolution of the Nima Basin in a regional tectonic context. With these goals in mind, we conducted large-scale geological mapping and structural analyses on the Nima Basin in the Bangong-Nujiang suture. Together with previous research findings, we discussed the tectonic settings, structural characteristics and structural evolution of the Nima Basin and reached the following conclusions: (1) The basement of the Nima Basin mainly consists of metamorphic rocks and marine sedimentary sequences within the Bangong-Nujiang suture zone formed through “soft” collision, and is fractured, with several E-W striking northerly/southerly dipping reverse faults. (2) The Nima Basin is infilled with upper Cretaceous-Neogene multi-cycle fluvial and lacustrine deposits; the terrigenous sedimentary infills later deformed into asymmetric folds with E-W trending axial planes and locally involved in the reactivated basement faults, while multi-phase contractional deformation propagated from the southern edge toward the basin center. (3) The surface structural pattern of the Nima Basin features “two depressions between three uplifts”, where the terrigenous sediments are mostly sourced from the northern imbricate thrust system and the southern fan-shaped extrusion structure, and, along with clasts derived from the central thrust nappes, accumulate in the two depressions—a northern one at the footwall of the imbricate thrusts and a southern one sandwiched between two reverse faults with opposing polarities. (4) The demise of the Bangong-Nujiang Ocean resulted in regional N-S crustal shortening and syncontractional development of the Nima basin in the suture zone, after which the Neo-Tethyan subduction and subsequent India-Asia continental collision triggered repeated reactivation of the basement faults within the Nima region, which invoked both multi-cycle deposition of molasse sequences and propagative deformation. In short, the Nima Basin is a contractional depression basin superimposed over a “soft-collision” type suture zone.

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    Tectonostratigraphic properties and evolution of the Yeba volcanic arc in South Gangdese, Tibet
    TANG Yu, WANG Genhou, FENG Yipeng, CI Dan, LI Dian, FAN Zhengzhe, GAO Xi, WEI Yufei, HU Jixin, ZHANG Peilie
    2022, 29(1): 285-302. 
    DOI: 10.13745/j.esf.sf.2021.7.33

    Abstract ( 289 )   HTML ( 12 )   PDF (23749KB) ( 422 )  

    In the South Gangdese magmatic belt a set of exposed Early-Middle Jurassic volcanic-sedimentary formations underwent multi-stage structural deformation, which resulted in intense foliation displacing the volcanic-sedimentary sequence and forming the typical tectonic-rock strata. According to the stratigraphic division scheme for orogenic belt, the Early-Middle Jurassic volcanic arc is defined as Yeba rock group, which is further divided into the Bangdui, Yeba and Jiama rock formations based on its internal lithologic assemblages and structural deformation modes. The three-stage deformation is characterized as below. In D1 stage, the brittle-ductile shear deformation is pure shear dominant general shear deformation, and beddings (S0) are mostly replaced by penetrative foliations (S1) (S1∥S0). The deformation is characterized as pure westward shearing, from the top, with a steep stretching lineation to 85-100° according to kinematic observations. EBSD results showed the deformation temperature is no more than 380 ℃, and quartz particles are clearly fine-grained, formed by sub-particle rotational recrystallization.40Ar-39Ar dating results suggests the D1 tectonic deformation happened around 79 Ma, therefore it could represent an extrusion structure formed by the low angle (flatten) Neo-Tethys ocean plate subduction in the back-arc compression background. In D2 stage, longitudinal folding of S1 led to the axial-plane cleavage (S2) that dips to N or S, with an inclination of 40-70°, and hinges toward W or NWW. Combining with the regional geological evolutionary history, we believe the Southern Gangdse back-arc basin was extruded upward under continuous N-S compressional stress during the Late Cretaceous (79-68 Ma), which resulted in upper crustal shortening and thickening, then led to folding. In D3 stage, deformation is mainly kink-bands and near E-W normal faults. The maximum principal compressive stress is in the vertical direction, while the minimum (extension direction) is in near N-S direction. Combining with the regional tectonic evolutionary history, we suggest that the near N-S extensional event during the late Oligocene-early Miocene (23.74-21.1 Ma) may represent the uplift of the Gangdese batholith caused by the delamination of the Indian lithosphere and/or Tibetan plateau lithosphere (the main dynamic mechanism) and the Gangdese counter thrust activity.

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    The exhumation mechanism of eclogites in continental orogenic belts: Metamorphic petrology and geophysical constraints
    ZHANG Dingding, ZHANG Heng
    2022, 29(1): 303-315. 
    DOI: 10.13745/j.esf.sf.2021.12.37

    Abstract ( 431 )   HTML ( 39 )   PDF (6415KB) ( 337 )  

    The deep subduction of the continental lithosphere is a frontier hotspot in the field of earth science, and the exhumation mechanism of eclogite is a key scientific issue in plate tectonics and continental dynamics. The p-T paths of eclogites from the world-famous continental orogenic belts show differential exhumation characteristics. To explore the exhumation mechanism in this study, metamorphic petrology and geophysical investigations were conducted on eclogites from three typical continental orogenic belts-Mesozoic-Cenozoic Alps, Mesozoic Sulu-Dabie, and Cenozoic Himalayas. The geophysical investigation found that, in the Alpine orogenic belt, subduction of the European plate resulted in large variations in lithospheric thickness beneath the Adria area. At the same time, the exhumation histories of eclogites are not the same in the Doria Maria and Pohorje areas of the Alpine orogenic belt versus in the greater Pohorje area, which, then, is probably due to the differential oblique extrusion of thrusting nappes from different periods after the break-off of the Adriatic ocean lithosphere. In the Sulu-Dabie orogenic belt, rapid exhumation of eclogites is likely be caused by the delamination or break-off of the lithosphere after the collision of the South and North China blocks. In the Himalayan orogenic belt, there are differences in the exhumation histories of eclogites in the middle Himalayas, and so are the differences in the p-T path and exhumation rate of eclogites from Naran versus from the Upper Kaghan Valley in the Western Himalayan Syntaxis. The differential exhumation, according to both metamorphic petrology and geophysical studies, is likely related to the tectonic extrusion and the break-off of the Indian continental lithosphere during the collision of the Indian and European plates. The Himalayan Orogen is a young and ongoing orogeny, thus it is more suitable for comprehensive metamorphic petrology and geophysical studies compared to the ancient Sulu-Dabie Orogen. Therefore, the exhumation mechanism of (ultra)-high-pressure eclogites in the Western Himalayan Syntaxis, i.e., tectonic compression and the break-off of subducting plate, can be applied to global orogenic belts.

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    Decipher the driving force in continental drift from new insights about the South Atlantic breakup process
    LIANG Guanghe, YANG Weiran
    2022, 29(1): 316-327. 
    DOI: 10.13745/j.esf.sf.2021.12.27

    Abstract ( 364 )   HTML ( 25 )   PDF (8127KB) ( 200 )  

    It has been widely recognized that the separation of the African and South American continents is caused by the South Atlantic breakup. The South Atlantic region is highly relevant to the development of the continental drift hypothesis. The driving force behind continental drift, however, has been in debate ever since the hypothesis was proposed. Therefore, quantitative analysis of the forces driving plate movement in the process of Atlantic breakup is particularly important. Here, we analyzed two deep seismic reflection survey profiles located on either side of the South Atlantic, in passive continental margin basins, and estimated the Moho dip angle of the African continent on the basis of tectonic geological interpretation. We then calculated the magnitude of crustal gravitational slip shear force along the Moho to explain the dynamic mechanism of African continent movement in the process of Atlantic breakup. We demonstrated that the African continental crust can produce a strong gravitational slip force on the inclined interface formed by mantle upwelling, and the shear force is greater in the south than in the middle part of the crust. According to our analysis, the continental crust can drift continuously by continuous hot mantle upwelling and gravitational slide. This model can reasonably explain the genetic mechanism for the many linear continental fragments in the Atlantic Ocean, and it can also provide an internal reason for why the South Atlantic today is wider in the south than it is in the middle. Based on this model we reconstructed the tectonic evolutionary history of the South Atlantic breakup process. This research established a new dynamic model of plate motion and provided more accurate constraint on understanding the driving force behind plate movement.

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    Decipher the driving force in continental drift from new insights about the South Atlantic breakup process
    LIANG Guanghe, YANG Weiran
    2022, 29(1): 328-341. 
    DOI: 10.13745/j.esf.sf.2021.12.27-en

    Abstract ( 526 )   HTML ( 23 )   PDF (3312KB) ( 224 )  

    It has been widely recognized that the separation of the African and South American continents is caused by the South Atlantic breakup. The South Atlantic region is highly relevant to the development of the continental drift hypothesis. The driving force behind continental drift, however, has been in debate ever since the hypothesis was proposed. Therefore, quantitative analysis of the forces driving plate movement in the process of Atlantic breakup is particularly important. Here, we analyzed two deep seismic reflection survey profiles located on either side of the South Atlantic, in passive continental margin basins, and estimated the Moho dip angle of the African continent on the basis of tectonic geological interpretation. We then calculated the magnitude of crustal gravitational slip shear force along the Moho to explain the dynamic mechanism of African continent movement in the process of Atlantic breakup. We demonstrated that the African continental crust can produce a strong gravitational slip force on the inclined interface formed by mantle upwelling, and the shear force is greater in the south than in the middle part of the crust. According to our analysis, the continental crust can drift continuously by continuous hot mantle upwelling and gravitational slide. This model can reasonably explain the genetic mechanism for the many linear continental fragments in the Atlantic Ocean, and it can also provide an internal reason for why the South Atlantic today is wider in the south than it is in the middle. Based on this model we reconstructed the tectonic evolutionary history of the South Atlantic breakup process. This research established a new dynamic model of plate motion and provided more accurate constraint for understanding the driving force behind plate movement.

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    Deep magmatic process of the Fushan complex in the southern section of Taihang Mountain, Hebei Province and its tectonic significance
    CUI Xiaoliang, SU Shangguo, ZHANG Yanan, CHEN Xuegen, SI Xiaobo, HUO Xiaoyan
    2022, 29(1): 342-363. 
    DOI: 10.13745/j.esf.sf.2021.1.63

    Abstract ( 206 )   HTML ( 7 )   PDF (16821KB) ( 149 )  

    The complex deep crust-mantle interaction in the magmatic process, and the deep magma chamber system during the Mesozoic lithospheric thinning of the North China Craton, is poorly understood, and the shallow response of the deep magma process is also controversial. In this study the Fushan complex in the Han-Xing area in central North China Craton is studied. A detailed petrographical, mineralogical, geochemical and geochronological analysis was carried out to investigate the multiple magma chamber system, the deep magmatic process and its shallow response. Zircon U-Pb dating results show that the age of the fine-grained monzonite from the early Fushan complex suite is 129 Ma, and the age of the porphyritic monzonite from the late porphyry complex suite is 122 Ma. Petrographic observation and back scatter electron (BSE) images indicate both amphiboles and plagioclases in the Fushan complex have a complex annulus structure. Through the analysis of the crystal growth process and discussion on the origin of crystal zoning, we show that the crystal growth environment and process are rather complex. The high Mg, K and Sr contents in the Fushan complex and the origin of crystal zoning in hornblende and plagioclase provided proof that the deep magma underwent strong magmatic mixing and multiple magma chamber process controlled by the activity of magmatic fluids. The depth of the early intrusive suite of the Fushan complex is 7 km, and the emplacement depth of the late suite is 1.5 km, which shows that the crust was uplifted by 5.5 km at 7 Ma. Most of the intrusive rocks in the Fushan complex have high Sr, low Y and positive δEu, indicating they might be formed from partial melting of the thickened continental crust. These observations support the existence of an eastern plateau of China in the Late Mesozoic.

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    Research progress on Cr isotopes in high temperature magmatic processes: A review
    SHI Kai, XU Lijuan, SU Yuwen, LIU Chunyang, MA Haibo, LIU Sheng’ao
    2022, 29(1): 364-376. 
    DOI: 10.13745/j.esf.sf.2021.7.19

    Abstract ( 249 )   HTML ( 21 )   PDF (3494KB) ( 150 )  

    Chromium (Cr) is a redox active transition metal, a moderately compatible, slightly ferriphilic element in magmatic processes. Cr occurs in three valence states in the silicate Earth: bivalent Cr(II), trivalent Cr(III) and hexavalent Cr(VI). It can be found in various minerals and rocks with different origins, thus Cr isotopes can provide valuable information on the genesis, redox condition and mineralization history of these Earth materials. To date, Cr isotopes have been widely used in various research fields, including modern environment, paleoenvironment, planetary evolution, and high-temperature geological processes. Understanding of Cr isotope geochemistry in magmatic processes, such as stable Cr isotope inventory of reservoirs and high temperature Cr isotope fractionation mechanism, provides basis for other studies. Especially with the development of mass spectrometry, interests in the behavior and mechanism of high temperature Cr isotope fractionation have increased in recent years. In this paper, we review the latest research progress on Cr isotope compositions of different reservoirs and Cr isotopes in high temperature magmatic processes.

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    Assimilation-fractional crystallization (AFC) of pegmatitic magma and its implications for uranium mineralization: A case study of the Husab uranium deposit, Namibia
    HUANG Ranxiao, WANG Guosheng, YUAN Guoli, QIU Kunfeng, Hounkpe Jechonias BIDOSSESSI
    2022, 29(1): 377-402. 
    DOI: 10.13745/j.esf.sf.2020.10.31

    Abstract ( 316 )   HTML ( 13 )   PDF (11879KB) ( 169 )  

    The Husab uranium deposit in the southern Central Zone of the Damara Orogenic Belt, Namibia, is a typical pegmatite-hosted ore deposit with uraninite as the main industrial uranium mineral. The mechanisms of uranium enrichment and precipitation in different ores are not clear. In order to reveal the relationship between pegmatitic magma evolution and uranium mineralization, we carried out whole-rock and mineral geochemical studies on pegmatite ores with different mineral compositions. Field and microscopic investigations showed the mineralized pegmatites can be divided into ‘simple’ and ‘complex’ types. The ‘simple’ pegmatite has normal granitic pegmatite texture, with a uniform distribution of uraninites among rock-forming minerals and low to medium level mineralization. The ‘complex’ pegmatite is characterized by heterogeneous texture with extremely high level mineralization and spatial association of uraninite with biotite agglomerates. Geochemical analysis showed that, in ‘simple’ pegmatite, uranium enrichment is mainly achieved through fractional crystallization of pegmatitic magma; while in ‘complex’ pegmatite, magmatic evolution is clearly controlled by assimilation and contamination, and uranium mineralization is the result of assimilation-fractional crystallization (AFC) of pegmatitic magma. The mixing of external mafic components (FeO, MgO, TiO2, MnO), specifically, led to change in the mineral crystallization sequence in ‘complex’ pegmatite melt, where “delayed” crystallization of feldspar minerals provided biotite with more favorable crystallization space/condition and led to massive biotite aggregation. Abundant biotite precipitation induced hydrolysis of UFm4-m complex in residual magama, which resulted in the precipitation of crystalline uraninites in and around biotite agglomerates. Thus, by studying the two types of uraniferous pegmatites one can better understand the magmatic evolutionary process and uranium mineralization mechanism, so as to enrich our knowledge about the pegmatite-type uranium deposit and provide a scientific basis for its future exploration and development.

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    Transient creep during crustal brittle-plastic transition and deformation mechanism of postseismic relaxation
    ZHOU Yongsheng, DAI Wenhao
    2022, 29(1): 403-412. 
    DOI: 10.13745/j.esf.sf.2020.9.41

    Abstract ( 221 )   HTML ( 5 )   PDF (6552KB) ( 88 )  

    The layer of major seismic events in continental crust at the depth of the quartz brittle-plastic transition zone is called seismogenic zone. The crustal deformation of this zone, controlled by temperature and affected by strain rate and stress, plays an important role during seismic cycle. The major deformation mechanism is steady state creep during interseismic deformation, then changing to rupture at coseismic loading and transient creep at postseismic relaxation. However, most of the studies in the past were focused on intersceismic creep-related ductile deformation in natural fault and steady state creep tests under high temperature. There have been very limited studies on transient creep-related postseismic relaxation based on geological survey of brittle-plastic fault transition and experiments under high temperature and pressure. Especially, there is an absence of constitutive equations related to transient creep at postseismic relaxation. Fault slip research and GPS observation-based simulation of crustal deformation during postseismic depend on the transient creep test data and rheological model. In this study, we report our research progress on transient creep in brittle-ductile fault zone and under high temperature/pressure, analyze the deformation mechanism and models and discuss issues in quantitative calculation of fault strength for transient creep in brittle-ductile transition zone.

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    Classification of tectonic deformation lithofacies based on deep geophysical information
    ZHANG Baolin, LÜ Guxian, YU Jianguo, LIANG Guanghe, LI Zhiyuan, XU Xingwang, HU Baoqun, WANG Hongcai, BI Minfeng, JIAO Jiangang, WANG Cuizhi
    2022, 29(1): 413-426. 
    DOI: 10.13745/j.esf.sf.2020.9.42

    Abstract ( 199 )   HTML ( 4 )   PDF (7990KB) ( 198 )  

    The establishment and application of “tectonic deformation lithofacies” mapping highlight the direction for deep and peripheral prospecting in old mining areas. In practice, this approach has achieved remarkable results and needs to be promoted and further studied. The understanding of the deep structure of tectonic deformation lithofacies zone depends on the interpretation of geophysical information. Similar to the properties of the geophysical field, the tectonic deformation lithofacies zone is also an existing geological body. The purpose of geophysical exploration is to explore and reveal the features of the burial depth, contour and internal structure of the tectonic deformation facies belt, so as to provide a basis for determining its formation time and evolutionary process. Due to the complex spatiotemporal correlation between geological and geophysical scales, it is difficult to improve the resolution and effectiveness of geophysical method if only the difference in physical parameters of fresh rock specimens is used as a discriminant marker. Therefore, it is necessary to combine tectonic deformation lithofacies into comprehensive interpretation, which can improve the multidisciplinary fusion of interpretation and deduction results. In searching the ultimate exploration targets, the structural ore-controlling factor is needed for setting up a three-level classification standard for tectonic deformation facies belt to extract the corresponding geophysical information. The first-level is the tectonic unit and tectonic stress field of the target object as well as the corresponding regional geophysical field characteristics, such as the extensional tectonic domain with alternative uplift and concave structures. The second-level refers to the ore-controlling structural system of the target object and the corresponding geophysical field characteristics of the ore field, such as the magmatic core complex uplift and detachment structural system. The third-level is the favorable metallogenic tectonic location of the target object and the geophysical characteristics corresponding to the key section, such as the contact zone between intrusive rock and surrounding rock or the ore-bearing fault zone. In this paper, the geophysical assemblage information characteristics and workflow of the three-level tectonic deformation lithofacies belt are introduced for selected typical metal deposit types prevalent in the world, providing an example for the effective application of geophysical exploration methods in deep prospecting prediction.

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    Calculation of metallogenic depth in the Jiaodong gold deposits: Tectonic correction method and metallogenic prediction
    LÜ Chengxun, ZHANG Da, XU Yaqing, GUO Tao, WANG Zongyong, HUO Qinglong, YUAN Yuelei
    2022, 29(1): 427-438. 
    DOI: 10.13745/j.esf.sf.2020.9.40

    Abstract ( 241 )   HTML ( 6 )   PDF (3816KB) ( 218 )  

    Metallogenic depth calculation is of great significance to ore deposit theory research and deep ore prospecting. The classical “pressure/specific gravity” calculation method, however, dose not consider the influence of tectonic stress on the mineralization process. Using this classical method, previous researchers had proposed the Jiaodong altered rock type gold deposit was Proterozoic metallogenic deposit with a depth of 6000-8000 m, and the quartz vein type gold deposit was Mesozoic metallogenic deposit located below 3000 m. However, guided by a five-story vertical zoning model established according to the calculation, the actual deep prospecting exploration was not successful. In recent years a new calculation method has been developed gradually, it uses tectonic correction in metallogenic depth calculation by canceling out additional tectonic stress before calculating metallogenic depth. In this paper, we introduce this new method, point out its application conditions and discuss its prediction significance. The application protocol entails (1) determining the metallogenic pattern; (2) conducting field survey on the tectonic deformation lithofacies; (3) measuring the rock/mineral strain, restoring the metallogenic-tectonic stress field, calculating the additional hydrostatic pressure due to tectonic stress; and (4) calculating the metallogenic depth. Using this method, the metallogenic depths of several typical gold deposits in Jiaodong were calculated and the results are: (1) Xiadian, 1979.51-3014.72 m; (2) Jiaojia, 1632.4-2331.6 m; (3) Dayingezhuang, 2775.4-4164.5 m; (4) Xincheng, 1781.29-2750.0 m; and (5) Linglong, 720.55-3454.97 m. Accordingly, the Jiaodong gold deposits are considered belonging to the epithermal shear zone type deposit with a metallogenic depth of 1000-4500 m. Therefore, it is inferred that the main orebody of the typical gold deposits in Jiaodong remains buried in the deep. Combined with the geological, geophysical and geochemical exploration information, we predicted a “second deep enrichment metallogenic zone” of gold deposit in Jiaodong, and this prediction has been confirmed by deep ore exploration effect.

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    Control of coal metamorphism by tectonic physicochemical conditions
    CAO Daiyong, LIU Zhifei, WANG Anmin, WANG Lu, DING Zhengyun, LI Yang
    2022, 29(1): 439-448. 
    DOI: 10.13745/j.esf.sf.2020.12.11

    Abstract ( 185 )   HTML ( 9 )   PDF (4028KB) ( 96 )  

    Coal is an organic rock very sensitive to geological factors such as temperature and pressure, and the physicochemical conditions associated with various tectonic thermal events are the fundamental driving force promoting the evolution of coal. In this paper, the current research status of coal metamorphism is reviewed; the control factors and evolutionary process and mechanism of coal in the stage from high rank coal to graphite are emphatically discussed. Coal metamorphism includes coalification stage and graphitization stage, which together constitute a continuous organic matter evolution process. The general trend of evolution is chemical constituents progressively simplifying and structure ordering, finally the graphite with three-dimensional ordered structure is evolved. Temperature and pressure (shear stress) are two major factors controlling coal metamorphism, their functions and evolution mechanism are different in different evolution stages. In the low and middle rank evolution stage, temperature is the main controlling factor of coal chemical structure evolution, which provides activation energy for chemical bond fracture, while stress polycondensation and stress degradation have catalytic effect on chemical structure evolution. The main mechanism from the high rank coal to graphite is that the basic structural units (BSUs) are interconnected and the short-range ordering range is increased,structural stress plays a key role in the evolution of the physical structure of macromolecules, it will promote the physical structure evolution of macromolecules by the orientation arrangement of BSUs and the distance decrease of carbon layer. It will enrich and deepen the understanding of the complete evolution sequence of the physical and chemical structure of coal by strengthening the research on the stage from high rank coal to graphite, the high-temperature and high-pressure simulation experiment of the coal-based graphite forming mechanism provides a feasible technical means for the study of the physical and chemical conditions of coal metamorphism.

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    Application of elemental capture spectroscopy in deep tight reservoir evaluation: A case study of well SK-2
    HAN Shuangbiao, TANG Zhiyuan, BAI Songtao, WAN Lei, RUI Yurun, GAO Yuan, HUANG Yongjian, WANG Chengshan
    2022, 29(1): 449-458. 
    DOI: 10.13745/j.esf.sf.2021.1.60

    Abstract ( 216 )   HTML ( 7 )   PDF (7576KB) ( 226 )  

    There are multiple gas logging anomalies in the Shahezi Formation, Songliao Basin, indicating its tight gas potential. However, deep tight reservoirs in the area have strong heterogeneity, thin thickness, interlayer development and various types. Based on the analysis of conventional well log of well SK-2, we used elemental capture spectroscopy (ECS) well logging to finely retrieve the mineral component content for accurate lithology identification, and subsequently identified five types of reservoirs by crossplot analysis. Combined with petrophysical experimental data, we further obtained the reservoir evaluation parameters such as variable skeleton porosity, brittleness index, and organic carbon content, which allowed us to categorize the reservoirs into three groups based on the well logging data and comprehensive evaluation indexes. In the Shahezi Formation (3730-4500 m), the porosity values range between 5%-9%, and the brittleness indexes range between 45%-60%. TOC of adjacent source rock is generally high, with relatively large accumulative thickness, and depth intervals at 3798-3831, 3950-3990 and 4150-4200 m show favorable tight gas potential for exploration and development. We demonstrated in this paper that, ECS well logging can accurately evaluate tight gas reservoirs so as to provide a reference basis for fracturing optimization in tight reservoirs.

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    Middle and far infrared spectroscopic analysis of calcite, dolomite and magnesite
    ZHU Ying, LI Yanzhang, LU Anhuai, DING Hongrui, LI Yan, WANG Changqiu
    2022, 29(1): 459-469. 
    DOI: 10.13745/j.esf.sf.2021.1.58

    Abstract ( 856 )   HTML ( 38 )   PDF (3308KB) ( 282 )  

    We used Raman and infrared (IR) spectroscopy in this study to investigate the spectral characteristics and infrared emission performance of calcite, dolomite and magnesite. We found substituting Mg for Ca would influence symmetric stretch (ν1), out-of-plane bend (ν2), asymmetric stretch (ν3) and in-plane bend (ν4) of CO32-and cause blue shift in all characteristic vibration bands in Raman, mid-IR absorption, far-IR absorption and IR emission spectra. According to blackbody radiation theory and radiation energy spectra of samples in the range of 400 to 2000 cm-1at 80 ℃, we found the emissivities of calcite, dolomite and magnesite were 0.951, 0.938, 0.895, respectively. The positions of vibration bands in the infrared absorption/emission spectra of the three minerals are significantly affected by the fundamental frequency of CO32-. All minerals produce a broad low absorption band in the 1300-1650 cm-1 range, which is related to asymmetric stretching of CO32-. Moreover, there is a negative correlation between the C-O absorption range (202, 236, 272 cm-1) and emissivity. Therefore, when the strongest chemical bond vibration gives rise to narrow absorption band in the emission spectrum, relatively high radiation energy and emissivity are indicated. Besides, the mineral crystal structure can also affect emissivity. Larger ionic radius or unit cell volume and longer bond length can reduce absorption energy thus enhance radiation emission in the radiation process. In conclusion, the atomic mass of cations in carbonate minerals can affect Raman and infrared vibrational frequency, and emissivity may be associated with C-O low-absorption band range, crystal structure and strongest absorption band controlling lowest emissivity. This study presents the necessary spectral information and thermal emissivity data for the characterization of carbonate minerals, which provides a reference for the spectroscopic characterization of similar minerals as well as establishes a basis for the characterization of carbonate minerals from the crust of the Earth and for exoplanet exploration by remote sensing.

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    Antibacterial clay minerals: Research advances and outlook
    GUO Dongyi, XIA Qingyin, DONG Hailiang, WANG Xi, ZENG Qiang, ZHAO Yu
    2022, 29(1): 470-485. 
    DOI: 10.13745/j.esf.sf.2021.7.20

    Abstract ( 392 )   HTML ( 11 )   PDF (3830KB) ( 240 )  

    Clay minerals have been widely utilized for industrial materials manufacturing and environmental remediation of heavy metals and organic contaminants, largely due to their layered structures and outstanding physio-chemical properties. In the medical field, antibiotic overuse has led to increased antimicrobial resistance, causing global concerns over antibiotic effectiveness. Thus it has become imperative to develop new bactericidal materials. The biomedical application of clay for treating wound abscesses, dyspepsia and joint inflammation has long been known, yet in-depth analysis of its antibacterial mechanisms has only been possible with the advancement of modern analytical methods. In the last decade, clays collected worldwide are shown to have broad-spectrum bactericidal activity, and such activity is closely associated with metal toxicity, structural Fe(II), surface charge and reactive oxygen species (ROS, generated by oxygen exposure) in clays. Besides, clay materials can be used as effective drug carrier for preparing antibacterial nanocomposite to enhance the physical property and activity of bactericidal agents. This article summarizes the recent studies on antibacterial activities and bactericidal processes and mechanisms of naturally reduced iron-containing clays, discusses the shared characteristics among clays with distinct antibacterial capabilities, and briefly describes the bactericidal activities of nanocomposites based on clays as carriers, aiming to address the current challenges and future development of antibacterial clays.

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