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    2020, Volume 27 Issue 2
    25 March 2020     Previous Issue    Next Issue
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    On the method of thinking in studying mineral deposits
    ZHAI Yusheng
    2020, 27(2): 1-12. 
    DOI: 10.13745/j.esf.sf.2020.3.6
    Abstract ( 394 )   HTML ( 13 )   PDF (1006KB) ( 915 )  

    Mineral deposit study is a branch of geoscience, which is complicated due to its three basic properties, i.e. geological, economic and environmental aspects. Based on the research of mineral deposits for many years in both practical experiences and academic thinking, the author has proposed eight viewpoints on the thinking method in the study of mineral deposits. These include: (1) practical thinking, investigating the occurrences of mineral deposits which is essential since genuine knowledge comes from practice; (2) systematic thinking, using metallogenic system to involve all basis; (3) historical thinking, knowing the whole process of formation, changing and preservation of mineral deposits; (4) economic thinking, considering mineral resources, economic construction and social development; (5) environmental thinking, developing the green mining and improving the ecological environment; (6) global thinking, combining the Earth system, metallogenic system, and exploration system; (7) strategy thinking, treating the mineral resource as the national strategy; and (8) dialectical thinking, using this as a fundamental philosophical thinking in mineral deposit research. In summary, utilizing the above thinking methods will help to improve the mineral deposit studies and make important contributions to ore exploration.

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    Geodynamic background of metallogenesis of large-superlarge ore deposits
    MO Xuanxue
    2020, 27(2): 13-19. 
    DOI: 10.13745/j.esf.sf.2020.3.7
    Abstract ( 281 )   HTML ( 8 )   PDF (1770KB) ( 959 )  

    Large and superlarge ore deposits are the results of supernormal accumulation of ore forming elements and their exploration is key for meeting the demands of mineral resources for national economy and society development. A combination of geodynamic background and metallogenic process studies with quantitative exploration and evaluation is an efficient approach. The geodynamic background study includes the following aspects: tectonic settings, crust-mantle structure and deep process, metallogenic petrological systems and regional thermo-fluid condition. For evaluating the preferential distribution and potential of mineral resources and predicting promising prospecting areas, it is specially important to reveal the deep Earth’s material and structure and geodynamic process of mass-energy transportation.

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    Further discussion on porphyry Cu-Mo-Au deposit formation in Chinese mainland
    HOU Zengqian, YANG Zhiming, WANG Rui, ZHENG Yuanchuan
    2020, 27(2): 20-44. 
    DOI: 10.13745/j.esf.sf.2020.3.8
    Abstract ( 681 )   HTML ( 25 )   PDF (8991KB) ( 1319 )  

    By reviewing the latest research progress of porphyry copper deposits (PCDs) and combining with the new data, this paper focuses on discussing the geodynamic background of non-arc PCDs in Chinese mainland, the origin of ore-forming magma, the evolution of magmatic-hydrothermal system, the sources of ore-forming metals (Cu, Au, Mo) and H2O, and their enrichment process. Except for a few PCDs formed in island arcs in China, most PCDs were formed during the stages of tectonic transformation and crustal extension in a collisional orogenic setting, and the stages of lithosphere extension and collapse, in the edge and interior of a re-activated craton. These non-arc porphyries are mostly isolated or nearly even-spaced stocks or bosses, and are characterized by high K contents and adakitic compositions. The ore-forming magmas are mainly originated from the newly formed thickened mafic crust or delaminated ancient lower crust, and a few originated from subduction fluid/melt metasomatized lithospheric mantle. Intercontinental collision and subduction led to large-scale crustal thickening, and the triggers for crustal melting include slab tearing, slab break-off, lithosphere delamination, and asthenospheric mantle upwelling. Similar to the island arc porphyries, the non-arc porphyries are also rich in water (> 4 wt% H2O) and f(O2) (ΔFMQ ≥+2). We think H2O does not come from the subducting slab, but mainly from the decomposition of amphibole in the newly formed lower crust or injection of H2O-rich ultrapotassic melt. Cu (Au) mainly comes from the decomposition of Cu-bearing sulfides in the newly formed lower mafic crust, or from the metal-rich lithospheric mantle reacted with delaminated lower crust. In contrast, Mo mainly comes from the continental crust in high Mo abundance. Regardless of island arc or non-arc settings, ore-forming magmas are generally enriched with metals (Cu, Au, Mo). Formation of PCDs does not require the incipient magma abnormally rich in metals, but requires sulfides not being saturated and separated from magma before exsolution of magmatic fluid. Although shallowly emplaced porphyry (1-6 km) can dissolve ore-forming fluids, large-scale PCDs usually require ore-forming fluids to dissolve from the deep part (emplacement depth ≥6 km) and have continuous mafic melt input. Shallowly emplaced porphyry can separate and condense immiscible low-salinity vapor phase and high-salinity liquid phase, while the deep-seated magma chamber directly dissolves high-temperature and low-salinity metal-rich supercritical fluid. Both high-salinity liquid phase and low-density supercritical vapor-phase fluid can transport metals and form PCDs with large-scale hydrothermal alteration.

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    Preliminary study on the Triassic continental mineralization system in China
    WANG Denghong, CHEN Yuchuan, JIANG Biao, HUANG Fan, WANG Yan, LI Huaqin, HOU Kejun
    2020, 27(2): 45-59. 
    DOI: 10.13745/j.esf.sf.2020.3.11
    Abstract ( 438 )   HTML ( 9 )   PDF (15968KB) ( 805 )  

    The Triassic mineralization system in China is composed of mineralization and all of the metallogenic series (sub-series) which formed in the continental environment (including the continental margin) during the Triassic (250-205 Ma) period. It is established that such metallogenic series such as those formed at Altai, Beishan, northern and southern margins of North China block, Liaoning-Jilin, Ordos, southwest Sanjiang area, Qiangtang, Upper Yangtze, Hunan-Hubei-Jiangxi border region, and Yunkai-Leiqiong, roughly constructed the Triassic mineralization system in China. Compare to Yanshanian, Indosinian mineralization is weaker. Sanjiang-Songpan Ganzi area in southwestern China has excellent protential of large-scale prospecting of deposits, even though the movement was strong in Indosinian. Recent isotope chronology studies have shown that, some deposits that were previously thought to have formed in the Hercynian (such as Dakalasu, Xiaokalasu pegmatitic rare metal deposits in Altai) or Yanshanian period (such as Xiaotongjiapuzi Au deposit and Gaojiapuzi Ag deposit in Liaoji rift zone) formed during the Indosinian period or experienced the mineralization process of the Indosinian cycle. During the whole evolution of Triassic, the two blocks of North China and South China were combined, and the combination zone and paleo-tectonics of the southern and northern edges of North China were re-activated and became the central metallogenic belt of the endogenous minerals. The continental basins such as the Ordos in North China and the small intermountain basins in South China have created conditions for the formation of coal, oil, gas, paste, and other sedimentary minerals. The evolution of the Tethys tectonic region in the southwest has undergone significant tectonic changes from the ocean to the land, especially the Indosinian movement, which has played an essential role in the formation of the continental pattern since the Mesozoic period of China. It has also laid a foundation for the formation of the basin-mountain pattern and the enrichment of its mineral resources in the Sichuan Basin. Therefore, the Triassic mineralization system can provide not only comprehensive basis for tectonic-rebuilding but also provides a theoretical basis for metallogenic prediction.

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    An integrated investigation of ore-forming fluid evolution in porphyry and epithermal deposits and their implication on exploration
    NI Pei, CHI Zhe, PAN Junyi
    2020, 27(2): 60-78. 
    DOI: 10.13745/j.esf.sf.2020.3.12
    Abstract ( 562 )   HTML ( 20 )   PDF (14519KB) ( 1037 )  

    Porphyry and epithermal deposits are the world’s most economically important resources for copper, molybdenum, gold, and silver. These two types of deposits are globally related in space and time. Hydrothermal fluid evolution is a critical process contributing to the mineralization in porphyry and epithermal deposits. The investigation for the properties and evolution of ore-forming fluids of porphyry and epithermal deposits is essential for exploring the process of metal precipitation, and it is also helpful in revealing the inherent genetic relationship between them. In this paper, we summarized the typical fluid inclusion characteristics, the standard fluid evolution process and metal precipitation mechanism in porphyry and epithermal metallogenic domains. The summary was based on literature review and case studies of the Fujiawu porphry type Cu-Mo (-Au) deposit, Tongcun Mo deposit, and the Qiucun and Ancun epithermal Au deposits. Furthermore, this paper also discusses the vapor transportation model of metal and fluids from the porphyry to the epithermal environment, and finally illustrates the application of large-scale fluid mapping as an exploration method using the Zijinshan Cu-Au deposit in Fujian as an example.

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    Classification and mineralization of the Au-(Ag)-Te-Se deposits
    LIU Jiajun, ZHAI Degao, WANG Dazhao, GAO Shen, YIN Chao, LIU Zhenjiang, WANG Jianping, WANG Yinhong, ZHANG Fangfang
    2020, 27(2): 79-98. 
    DOI: 10.13745/j.esf.sf.2020.3.13
    Abstract ( 415 )   HTML ( 22 )   PDF (8483KB) ( 876 )  

    The genetic types of Au-(Ag)-Te-Se metallogenic systems can be classified according to the characteristics of occurrence and degrees of tellurium and selenium enrichment in gold deposits as (1) epithermal Au-Ag deposits, (2) orogenic gold deposits, (3) Carlin and Carlin-like gold deposits, (4) alkaline and subalkaline intrusion-related gold deposits, (5) Cu-Au porphyry deposits, (6) Cu-Au skarn deposits, and (7) gold-polymetallic volcanogenic massive sulphide (VMS) deposits. Tellurium and selenium preferentially partition in the mantle while intrusive and volcanic rocks are important sources of Te and Se in the Au-(Ag)-Te-Se metallogenic system. Moreover, black rock series are important sources of Se, whilst temperature, pH and oxygen fugacity are important controllers of Te-Se transport and enrichment. The ore-forming mechanisms of the Au-(Ag)-Te-Se metallogenic systems are closely related to magmatic degassing, fluid-melt separation, water-rock interactions, fluid boiling and mixing, and organic processes. Among them, magmatic degassing, fluid-melt separation, fluid boiling and mixing are important mechanisms in the formation of telluride-rich gold deposits, while water-rock interactions, fluid mixing and organic processes are important mechanisms in the formation of selenide-rich gold deposits. During ore formation, some metastable or unstable minerals precipitated in early stages usually experience solid solution separation, and minerals in contact with unsaturated fluids often trigger coupled dissolution-reprecipitation reactions; both processes result in the formation of various mineral assemblages and ore textures.

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    Meditations on the future development of ore deposit science in China
    CHEN Huayong
    2020, 27(2): 99-105. 
    DOI: 10.13745/j.esf.sf.2020.3.10
    Abstract ( 565 )   HTML ( 8 )   PDF (553KB) ( 857 )  

    In the 21st century, and especially over the last ten years, societal and technological developments have imposed serious challenges and new demands upon the study of economic geology. These mainly include the frontiers of economic geology, national strategic arrangements, and important social demands. Challenges to the development of economic geology are dominated by a lack of innovation with respect to ore deposit models, limited interdisciplinary integration, and weaknesses in applied basic research. National strategic arrangements mainly consist of the ‘one belt, one road’, maritime power policy, and critical metals, while important social demands primarily include deep exploration, intelligent and efficient exploration, and green (eco-friendly) exploration. To meet these challenges and demands, as well as to contribute to the construction of a great, modern, socialist country, and greatly rejuvenate China within the next 30 years, we propose that the study of economic geology in China should be concentrated on the following: (1) multi-dimensional and comprehensive studies of metallogenic models; (2) applied basic research on useful indicators for exploration; (3) enrichment mechanisms of critical metals; (4) ‘one belt, one road’ and marine mineral resources; (5) theories and methods of integrative research for deep exploration; and (6) inte-lligent and efficient exploration systems.

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    Further discussion on the Sanjiang Tethyan composite metallogenic system
    DENG Jun, WANG Qingfei, CHEN Fuchuan, LI Gongjian, YANG Liqiang, WANG Changming, ZHANG Jing, SUN Xiang, SHU Qihai, HE Wenyan, GAO Xue, GAO Liang, LIU Xuefei, ZHENG Yuanchuan, QIU Kunfeng, XUE Shengchao, XU Jiahao
    2020, 27(2): 106-136. 
    DOI: 10.13745/j.esf.sf.2020.3.9
    Abstract ( 471 )   HTML ( 22 )   PDF (29440KB) ( 918 )  

    Composite orogeny and composite metallogenesis are salient features of the regional tectonic evolution and metallogeny in China, respectively. The complex sources of ore-forming materials, variable mechanisms of tectonic driving, divers genetic types of mineralization and the multi-stage of remobilization and overprint, have been the research interest in the scope of regional metallogenic theory. The Sanjiang Tethyan orogenic belt in Southwest China is a typical miniature of composite orogeny in China. It has a complex spatial-temporal composite orogenic framework, undergoing the evolution of the Proto-, Paleo-, Meso- and Neo-Tethyan accretionary orogeny in Paleozoic and Mesozoic and the collisional orogeny between Indian and Eurasian plates in Cenozoic. In order to systematically explain the composite metallogenesis under the background of composite orogeny and guide the regional exploration scientifically, in this paper, based on the theory of metallogenic system, we divide Proto-, Paleo-, Meso- and Neo-Tethyan metallogenic system related to accretionary orogeny, and squeezing folds, removal extension, squeezing slip, stretching rotation metallogenic system related to collisional orogeny, recognize that composite metallogeny is significant, and identify four types of typical composite metallogenic systems in five metallogenic belts, including accretionary-collisional orogenic VMS Pb-Zn-Cu+magmatic-hydrothermal Mo-Cu along the Changning-Menglian suture zone, accretionary+collisional magmatic-hydrothermal Cu-Mo-Sn-W in the Yidun arc and Tengchong-Baoshan block, collisional orogenic MVT Pb-Zn+magmatic-hydrothermal Cu-Pb-Zn-Ag in the Lanping basin and collisional orogenic alkali-rich-porphyry (Au-Cu-Mo)+orogenic Au type along the western margin of the Yangtze block. We also analyze the components each composite metallogenic system in detail, and propose the theory of composite metallogenic system, which means that geological systems formed by superimposition or interaction of multiple metallogenic events with different times or genetic types driven by the spatial-temporal transitions of varying tectonic regimes during superimposed orogeny.It was revealed the tectonic regime transition occurring upon the previous arc or rift belt is the main mechanism for the formation of composite metallogenic system.

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    Control of the Precambrian basement on the formation of the Mesozoic large-scale low-temperature mineralization in the Yangtze Craton
    HU Ruizhong, CHEN Wei, BI Xianwu, FU Shanling, YIN Runsheng, XIAO Jiafei
    2020, 27(2): 137-150. 
    DOI: 10.13745/j.esf.sf.2020.3.15
    Abstract ( 274 )   HTML ( 7 )   PDF (10175KB) ( 571 )  

    Large-scale low-temperature mineralization occurs throughout the Yangtze Craton and central-western USA, with the former containing more types of low-temperature deposit. In addition to the MVT Pb-Zn and Carlin-type Au-(As)-(Sb)-(Hg)-(Tl) deposits common to the central-western USA, the Yangtze Craton also contains numerous vein-type Sb, Hg, and As deposits, making it ideal for exploring low-temperature mineralization formation models. Numerous studies have been conducted on the Mesozoic large-scale low-temperature mineralization in the Yangtze Craton, and the deposit geology, ore components, ore-forming fluids, timing, and geodynamic setting of mineralization are generally well understood. This study revealed that different deposit types (e.g., Pb-Zn, Au-Hg-Sb-As, and Au-Sb) in the Yangtze Craton are not spatially associated but distributed in specific domains with distinct Precambrian basement rocks. There are some indications that the basement rocks are variably enriched with various metals. The metals are remobilized and transported by deep-circulating fluids responsible for late large-scale low-temperature mineralization. The specific distributions of different deposit types are likely mainly controlled by the spatial heterogeneity of ore-forming elements in the basement rocks of the Yangtze Craton. However, this interpretation requires further confirmation, as tracing the metal sources of low-temperature mineralization is highly complex.

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    The Cenozoic tectono-magmatism-mineralization effect of the intracontinental tectonic transformation system in the western margin of Yangtze Block
    LI Wenchang, JIANG Xiaojun
    2020, 27(2): 151-164. 
    DOI: 10.13745/j.esf.sf.2020.3.16
    Abstract ( 257 )   HTML ( 8 )   PDF (14159KB) ( 657 )  

    The Tethys tectonic domain, which extends from east to west across Eurasia, contains one of the most important precious/base metallogenic belts. The belt turns toward the southeast after reaching the Yangtze Block and series of large to giant Cu-Au deposits have recently been discovered at this hinge zone. It has previously been determined that the large-scale Jinshajiang-Honghe strike-slip fault along the western Yangtze margin cut through the lithosphere, inducing magmatic intrusions and forming an alkali-rich porphyry belt. In this study, several alkali-rich intrusions (including Laojunshan in Jianchuan, Beiya in Heqing, Laojiezi-Gangou in Yao’an, Yuzhila in Dayao, and Zhiju in Yongren) were analysed for tectonic stress. The results show that in addition to the distribution of alkali-rich porphyries along both sides of the Jinshajiang-Honghe Fault, there are also many dykes along the E-W-trending structures within the interior of the Yangtze Block. These intrusions have magmatic and mineralization ages ranging from 36.87-30.70 Ma, coeval with the formation of the porphyry belt. It was found that the magmatic ages become younger and alkalinity increases from west to east, defining an eastward magmatic migration. Field observations and statistical analyses of these nearly E-W-trending dykes and joints revealed that the structures controlling magmatism have undergone E-W compression and N-S extension, which is compatible with the large NW-trending strike-slip structures observed. Based on these lines of evidence, the formation of a series of alkali-rich intrusions within the Yangtze Block is likely related to the large-scale NW-trending strike-slip structures. The alkali-rich intrusions and related Cu-Au porphyry mineralization are distributed in the N-S- and E-W-trending secondary structures from west to east, and magmatism and mineralization were coupled with intracontinental structural transformations.

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    A review on the Mesozoic crust-mantle interaction and metallogeny of various skarn deposits in the Jiangxi-Anhui segment along the Yangtze River
    DU Yangsong, CAO Yi, QIN Xinlong, PANG Zhenshan, DU Yilun, WANG Gongwen
    2020, 27(2): 165-181. 
    DOI: 10.13745/j.esf.sf.2020.3.17
    Abstract ( 219 )   HTML ( 6 )   PDF (4745KB) ( 393 )  

    A large number of Mesozoic intrusions, their enclaves and related skarn ore deposits are distributed along the Yangtze River.We present thirty years of our study on Mesozoic intrusions with xenoliths and associated skarn deposits in the Jiangxi-Anhui segment along the Yangtze River. Specifically, this paper focuses on the analysis of the Mesozoic crust-mantle interaction and metallogeny of various skarn deposits in the area in order to lay some foundation for the development of crust-mantle metallogeny. Isotopic chronological and petro-geochemical data of the basic intrusive rocks and mafic xenoliths confirm the occurrence of underplating of the post-collisional mantal-derived magma (145-135 Ma) rich in Cu and Au, and the post-orogenic mantal-derived magma (130-120 Ma) rich in Fe and Au. In addition, the existence of similar activities of magma from the mantle with crust in the Mesozoic can be confirmed from the data. The activities of magma from the mantle with crust mainly include crystalline fractionation, assimilation and contamination, magma mixing, and magma liquation. Geological investigation and microscopic observation of skarn deposits show that the two episodes of intrusions of various mantle-derived magmas with crust into Late Paleozoic to Early Mesozoic wallrock strata led to mineralization of various skarns responsible for the formation of various skarn deposits, including contact replacement, stratabound, magma, and compound and superimposed skarn deposits. These deposits are characterized by distinct types of mineral assemblage and texture as well as the structure of hydrothermal replacement, sedimentation-hydrothermal replacement, magma crystallization-hydrothermal replacement, and sedimentation-magma crystallization-hydrothermal replacement, respectively. The existence of the xenoliths of Proterozoic metamorphic rocks, rich in ore-forming materials such as Cu and Zn in the post-collisional acidic to intermediate-acidic intrusions, supports contamination of the Proterozoic metamorphic basement in the shallow-level magma chamber by the post-collisional underplating basaltic magma rich in Cu and Au or its evolved magma. The contamination resulted in Cu further enrichment to form acidic to intermediate-acidic magmas with increased Cu. The occurrence of the cumulates containing a lot of Cu-Fe sulfides (chalcopyrite and pyrrhotite) and oxide inclusions in the post-collisional intermediate-basic to basic intrusions, is consistent with intensive crystalline fractionation of the post-collisional underplating basaltic magma rich in Cu and Au and its evolved magma in the deep-level and shallow-level magma chambers, respectively. The crystalline fractionation caused depletion in Cu and Fe to form intermediate-basic to basic magmas with even higher Au enrichment. Text Some skarn enclaves occur in the post-collisional acidic to intermediate-acidic intrusions, and few enclaves of the transition of gabbro to skarn exist in the skarn. This fact indicates the contamination of the Late Paleozoic carbonate strata with Cu and Fe source bed by the post-collisional underplating basaltic magma rich in Cu and Au in the intrusive location, leading to Cu further enrichment to form a skarn magma with increased Cu. The acidic to intermediate-acidic magmas with increased Cu, the intermediate-basic to basic magmas with increased Au, and the skarn magma with increased Cu are the most important controlling factors for the formations of contact replacement and stratabound skarn Cu, contact replacement skarn Au, and magmatic skarn Cu ore deposits during the post-collisional period, respectively. The occurrences of the deep-level and shallow-level cumulates containing a lot of Cu-Fe sulfides (chalcopyrite and pyrrhotite) and oxide inclusions in the post-orogenic intermediate-basic to basic intrusions provide evidence for intensive crystalline fractionation of the post-orogenic underplating basaltic magma rich in Fe and Au in the deep-level magma chamber. The crystalline fractionation combined with magma mixing caused depletion in Cu and Fe to form intermediate to basic magmas with higher Au enrichment. Contaminations of the Late Paleozoic carbonate strata with Cu and Fe source bed, the Early Mesozoic Fe source bed, and the Early Mesozoic Fe and Si source bed by the post-orogenic underplating basaltic magma rich in Fe and Au in the intrusive location led to Fe, Fe, and Fe and Si further enrichments to form skarn, basic, and intermediate to basic magmas more enriched in Fe, respectively. The intermediate-basic to basic magmas with increased Au enrichment as well as the skarn, basic, and intemediate-basic to basic magmas with increased Fe enrichment are predominantly responsible for the formation of contact replacement skarn Au, magmatic skarn Fe, ore magma Fe, and contact replacement skarn Fe ore deposits during the post-orogenic period, respectively.

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    The origin of ore-forming materials of the Yanshanian porphyry Mo-hydrothermal Pb-Zn(Ag) metallogenic system in eastern China
    XIE Yuling, CUI Kai, XIA Jiaming, WANG Ying, QU Yunwei, YU Chao, SHAN Xiaoyu
    2020, 27(2): 182-196. 
    DOI: 10.13745/j.esf.sf.2020.3.14
    Abstract ( 209 )   HTML ( 4 )   PDF (9892KB) ( 518 )  

    China is currently the biggest producer of Mo, Pb, and Zn, and it holds the biggest Mo resource and the second biggest Pb and Zn resources in the world. The Yanshanian porphyry Mo deposits and hydrothermal Pb-Zn (Ag) deposits in eastern China are the most important sources of Mo, Pb, and Zn in China, and many geological and geochemical studies have been conducted thereon. It is proposed that the hydrothermal Pb-Zn (Ag) deposits comprise parts of the porphyry Mo metallogenic system. However, there is still a controversary regarding the origin of the parent magma and the ore-forming materials for this metallogenic system. The porphyry Mo deposits have been considered to be related to a typical crust source magma, but further geological and geochemical studies imply that a mantle derived magma was involved in the ore-forming process. Carbonatite, a typical mantle magmatic rock, allows researchers to study the chemical composition of the mantle. Carbonatite derived from the partial melting of the enriched mantle that undergoes melt or fluid metasomatism from a subducted oceanic plate, has the highest Mo content among all kinds of magmatic rocks and also contains large amounts of Pb, Zn, Ag, S, CO2, and H2O. The Sr and Nd isotopic data and trace element results of the causative magmatic rock related to the porphyry Mo deposits in eastern China showed an ocean island basalt affinity, and the coeval mafic rock and carbonatite appeared to originate from the enriched mantle. Thus, this study proposes that the magma related to the Yanshanian Mo-Pb-Zn (Ag) system in eastern China is derived from the partial melting of the enriched mantle, and the ore material and ore-forming fluids may also come from the mantle.

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    An overview of recent advances in porphyrite iron (iron oxide-apatite, IOA) deposits in the Middle-Lower Yangtze River Valley Metallogenic Belt and its implication for ore genesis
    ZHAO Xinfu, ZENG Liping, LIAO Wang, LI Wanting, HU Hao, LI Jianwei
    2020, 27(2): 197-217. 
    DOI: 10.13745/j.esf.sf.2020.3.20
    Abstract ( 540 )   HTML ( 10 )   PDF (10227KB) ( 690 )  

    “Porphyrite iron deposits” within the Ningwu and Luzong volcanic basins in the Middle-Lower Yangtze River Valley Metallogenic Belt are hosted in the early Cretaceous(~130 Ma) volcanic-intrusive rocks. They are characterized by mineral assemblages of magnetite-apatite-actinolite(diopside)and have geological characteristics similar to other iron oxide-apatite(IOA) or Kiruna-type deposits worldwide. Since the concept of porphyrite iron deposit was proposed in the 1970s, there are several hypotheses for ore genesis, that include immiscible iron-oxide melts of magmatic origin, magmatic-hydrothermal replacement, and a combination of magmatic and hydrothermal processes. This study presents an overview of recent advances in porphyrite iron deposits in China, including geochronologies of iron mineralization and the associated ore-related intrusions, sources of ore-forming materials, nature of early-stage ore-forming fluids, and possible genetic relationship between porphyrite iron deposits and skarn iron deposits as well as the newly discovered gold-copper mineralization at the periphery. Finally, we also make a comparison of those with global IOA deposits and comment on the potential problems of current genetic models. Recently, a large high-precision geochronological dataset has revealed that the IOA deposit in the Ningwu and Luzong basins intensively formed at ~130 Ma. It has been suggested that iron is dominantly derived from the subvolcanic intrusions, and the early stage ore fluids are characterized by high-temperature (550-780 ℃), ultra-high salinity (~90 wt% NaCleq). Such fluids are consistent with field evidence of the earliest, deposit-scale sodic alteration. On the other hand, S-Sr isotopes and in-situ analyses of the fluid inclusions indicate that external evaporite-derived fluids were involved in the iron mineralization processes, although it has not been known precisely, the role of evaporite during the mineralization. It should be also highlighted that the paragenetic sequence of hydrothermal alteration in the IOA deposit is similar to that of iron skarn deposits, implying a cryptic genetic link between the two types. We believe that the presence of different alteration phases possibly resulted from the interaction between similar ore-forming fluids and different country rocks at different conditions. During the past decade, IOA deposits have been attracted much more global attention and quite a few papers had been published in high ranked international journals. Except for traditional hypotheses involving Fe-oxide melts and magmatic-hydrothermal replacement, other models combined with magmatic and magmatic-hydrothermal processes have also been proposed. These new models include a magmatic magnetite-bubble suspension model and the model of ascent, degassing, and emplacement of hydrous immiscible Fe-Ca-P melts. Nevertheless, the current debate regarding the genesis of the IOA deposit still focuses on the transitional processes between magmatic and hydrothermal stage, and how iron and phosphorous separated from the magma or the intrusion, transported and concentrated. The proposed models, including iron oxide, melts (Fe-O or P-Ca-Fe-O), magmatic magnetite microlites (Fe3O4), Fe-rich hydrothermal fluids, or other enigmatic processes, remain open to be testified through further research.

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    The main metallogenic systems and metallogenic lineages around the Middle and Upper Yangtze Block
    YAO Shuzhen, GONG Yongjun, HU Xinlu, ZHOU Zonggui, SHEN Chuanbo, PI Daohui, XIONG Suofei, TAN Mantang
    2020, 27(2): 218-231. 
    DOI: 10.13745/j.esf.sf.2020.3.19
    Abstract ( 244 )   HTML ( 3 )   PDF (10644KB) ( 611 )  

    The giant metallogenic belt around the Middle and Upper Yangtze Block is a product of multicycle and multistage regional tectonic evolution. The major metallogenic systems include the sedimentary-hydrothermal sedimentary metallogenic systems, epigenetic basin fluid metallogenic system, and magmatic hydrothermal metallogenic system. The Nanhua Mn, Sinian Pb-Zn, Sinian-Cambrian Ag-V-polymetallic, and Permian Mn sedimentary-hydrothermal sedimentary metallogenic systems were mainly formed at the margin of the paleocontinent during the tectonic transition from compression to extension. The development of large and super-large deposits were constrained by the tectonic network system at the continental margin. The favorable environment for mineralization is the aulacogen controlled by extensional faults. The continuous supply of ore-forming fluids from the syngenetic fault system was the key factor for ore genesis. Indosinian to early Yanshanian epigenetic basin fluid Pb-Zn metallogenic system is the dominant metallogenic system in this region. It developed in the combination zone of the basin and orogenic belt. The development of large and ultra-large deposits was mainly controlled by the combination of faults, strata, and lithology. The Yanshanian magmatic hydrothermal Pb-Zn-polymetallic metallogenic system was controlled by the intrusive contact structures, while Pb-Zn orebodies mainly developed in the outer zone. The Yanshanian magmatic hydrothermal Au-polymetallic metallogenic system also developed in the combination zone of the basin and orogenic belt. The large and ultra-large deposits were controlled by the combination of faults, folds, and concealed granites. Finally, the preliminary metallogenic lineages of major metal deposits around the Middle and Upper Yangtze Block were constructed.

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    The geophysical exploration of Mesozoic iron-copper mineral system in the Middle and Lower Reaches of the Yangtze River Metallogenic Belt: a synthesis
    LÜ Qingtian, MENG Guixiang, YAN Jiayong, ZHANG Kun, GONG Xuejing, GAO Fengxia
    2020, 27(2): 232-253. 
    DOI: 10.13745/j.esf.sf.2020.3.18
    Abstract ( 284 )   HTML ( 8 )   PDF (52214KB) ( 599 )  

    Mineral systems driven by deep Earth processes are self-organized critical systems involving the transfer and accumulation of mass and energy. During the formation and evolution of such a system, “fingerprints” are left at different scales across the lithosphere, which can be detected or observed through geophysical, geochemical, and remote sensing methods. In this study, we first analysed multi-scale geophysical and geochemical data over the last decade from the Middle and Lower Yangtze River Metallogenic Belt. Based on the theoretical framework of a deep-seated mineral system, we then attempted to identify the geophysical and geochemical “fingerprints” for the source, channel, and site of a typical intracontinental mineral system. Finally, we attempt to establish a structural model of the mineral system. We concluded that the Late Mesozoic large-scale Fe-Cu polymetallic mineralization in the Middle and Lower Yangtze River Metallogenic Belt may be considered a holistic mineral system, consisting of three subsystems: (1)a skarn-porphyry subsystem related to high-K calc-alkaline magmatic rocks,(2) a terrestrial volcanic iron (sulphur) subsystem related to shoshonite formation, and (3) a Cu-Au (uranium) subsystem related to alkaline rocks. The source area of the mineral system was derived from the melting and underplating of an enriched mantle and subsequent multi-level mixing with lower crustal materials at the crust/mantle boundary. The type of metal formed depended upon the mixing ratio of the mantle-derived magma and crust materials. Moreover, the “crocodile” structure developed in the Middle and Lower Yangtze River Metallogenic Belt is the main channel of the Fe-Cu mineral system. The site of ore precipitation (“termination” of the mineral system)was predominantly controlled by near-surface folds, faults, interlayer detachment faults, and their resultant fracture network. Regional magnetic, radioactive, and geochemical data are the signatures (or “fingerprints”) of a mineral system; by analysing these multi-scale signatures, we can deepen our understanding of the spatial structures of mineral systems and effectively predict deep targets.

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    The orogenic Au mineralization system and regional tectonic evolution in the Kalamaili area, East Junggar, Xinjiang
    GU Xuexiang, ZHANG Yongmei, GE Zhanlin, CHEN Weizhi, XU Jingchi, HUANG Gang, TAO Wei
    2020, 27(2): 254-275. 
    DOI: 10.13745/j.esf.sf.2020.3.21
    Abstract ( 243 )   HTML ( 6 )   PDF (33814KB) ( 632 )  

    Au deposits, including the Jinshuiquan, Shuangquan, Nanmingshui, and East Sujiquan Au deposits in the Kalamaili area of eastern Junggar, Xinjiang, constitute a mineralization system related to the late Paleozoic collisional orogeny. The deposits are sandwiched between the regional Kalamaili and Qingshui-Sujiquan faults. Au mineralization is controlled by the subsidiary brittle-ductile faults in slightly metamorphosed, late Paleozoic volcanic sedimentary rocks, and typically occurs as medium-to-steep dipping auriferous quartz veins and surrounding altered rocks. Fluid inclusions, H-O-S-Pb isotopes, and hydrothermal zircon U-Pb dating indicate that the ore-forming fluids are characterized by medium-to-high temperature (mostly 240-330 ℃), low salinity (<6 wt% NaCleq), and CO2-rich metamorphic water. The ore-forming material was sourced from host volcanic sedimentary rocks. Fluid immiscibility (phase separation) and fluid-rock interaction (wall-rock sulfidation) are the principal mechanisms of Au deposition. The timing of mineralization was approximately 314 Ma, and mineralization depths ranged from 7 to 15 km. From the Late Carboniferous to Early Permian, the transition of the tectonic system from compression to strike-slip or strike-slip extension in the study area resulted in the migration of deep metamorphic auriferous CO2-H2O-NaCl±CH4 fluids to shallower depths along NW- to EW-trending strike-slip faults. Au precipitation in the subsidiary faults of the brittle-ductile transition zone or brittle deformation zone led to the formation of auriferous quartz veins and related altered rock ores.

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    Discussion on the formation of magmatic Cu-Ni-Co sulfide deposits in margin of Tarim Block
    LI Wenyuan, WANG Yalei, QIAN Bing, LIU Yuegao, HAN Yixiao
    2020, 27(2): 276-293. 
    DOI: 10.13745/j.esf.sf.2020.3.22
    Abstract ( 367 )   HTML ( 8 )   PDF (4634KB) ( 472 )  

    Due to the controversy over the diagenesis and mineralization of the newly discovered Xiarihamu super-large magmatic copper-nickel-cobalt sulfide deposit, it started a new round of discussion on the metallogeny of the magmatic copper-nickel-cobalt sulfide deposit. The copper-nickel-cobalt sulfide deposits in the orogenic belt in China have a distinctive distribution feature. In the 1980s, with the discovery of a series of magmatic copper-nickel-cobalt sulfide deposits in the mafic-ultramafic rocks in eastern Tianshan, it was proposed that these mafic-ultramafic rocks are ophiolites. Then, a mainstream viewpoint was formed that the copper-nickel-cobalt deposits in eastern Tianshan were formed in the continental crust rifting trough environment after the subduction of the oceanic crust and the closure of the continental collision. The discovery of the Early Permian Tarim Large Igneous Province in the 21st century suggested that the magmatic copper-nickel-cobalt sulfide deposits in eastern Tianshan and the Beishan in Xinjiang are related to the formation of the Tarim mantle plume. However, based on the geochemistry of mafic-ultramafic whole-rock with typical island arc characteristics, some researchers maintained that some magmatic copper-nickel-cobalt deposit could be associated with subduction-reduction plates. We believe that the trace elements of whole-rocks that show island arc information are a geochemical shielding effect caused by the subduction and crustal contamination. The composition of the chrome spinel and the oxygen fugacity environment indicated that these deposits were formed in an extension environment, rather than the island arc. The three-period magmatic copper-nickel-cobalt sulfide deposits around the Tarim block represent the three most critical nickel-forming events in China, which reflect the vital convergent events between the Tarim block and the supercontinent. First, the Neoproterozoic giant Jinchuan Cu-Ni-Co-PGE deposit represents the Rodinia supercontinent break-up event, which led to the formation of the Paleo-Asian Ocean among the Tarim Block, Yangtze Block, and Western Australian Block. Second, the large Xiarihamu nickel-cobalt deposit in the Early Paleozoic was the product of the break-up event in the southern Gondwana land, leading to the formation of the Paleo-Tethys in the Paleozoic. Third, the Early Permian Poyi copper-nickel deposit should be a plutonic facies composed of mantle plumes and large igneous rocks grown in the Pangea supercontinent. This article systematically summarizes and compares the metallogenic characteristics of the three deposits. Although Poyi has the highest MgO content of parent magma among the three deposits, it shows a lower degree of crustal contamination, especially crustal sulfur contamination, compared with Xiarihamu and Jinchuan. This is probably the main reason why the Poyi intrusion has the lowest Cu-Ni mineralization among the three deposits. Furthermore, the Poyi intrusion has some contamination of calcium, which can hinder sulfide saturation.

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    Deformed zone hosted gold deposits in the China-Kazakhstan-Kyrgyzstan-Uzbekistan Tian Shan: metallogenic environment, controlling parameters, and prospecting criteria
    XUE Chunji, ZHAO Xiaobo, ZHAO Weice, ZHAO Yun, ZHANG Guozhen, Bakhtiar NURTAEV, Nikolay PAK, MO Xuanxue
    2020, 27(2): 294-319. 
    DOI: 10.13745/j.esf.sf.2020.3.23
    Abstract ( 323 )   HTML ( 8 )   PDF (10933KB) ( 505 )  

    Tian Shan is the world's second largest gold ore cluster and hosts an array of world-class and large/superlarge gold deposits. It constitutes a giant cross-border gold metallogenic belt that extends westward from Central Xingjiang, China to Uzbekistan, via southeastern Kazakhstan and Kyrgyzstan. What metallogenic settings have been responsible for the large-scale gold mineralization of the Tian Shan giant gold belt? What are the key factors controlling gold mineralization? What are the criteria for gold prospecting in Tian Shan giant gold belt? All of these are crucial geological and prospecting problems that have become the focus of the academics and mining industry. Based on an extensive and thorough literature review, along with comprehensive field investigations on the geology and gold deposits of Tian Shan orogen, this paper suggests that the large-scale gold mineralization of Tian Shan had formed during a terrane assembling deformation subsequent to the final closure of the paleo-Asian Ocean in the Late Carboniferous-Early Permian. On the other hand, minor gold mineralization had formed during intracontinental strike-slip deformation in the Middle-Late Permian. The large brittle/ductile-brittle deformation zones, situated near the tectonic sutures of the northern and southern margins of the Middle Tian Shan, are the key factors controlling the large-scale gold mineralization of Tian Shan. Multistage overprinting mineralization is a significant feature of the Tian Shan deformed zone-hosted gold deposits. The crustal initial enrichment, structural deformation activation, and magmatic-hydrothermal overprinting are the main factors controlling the Tian Shan deformed zone-hosted gold deposits. Fine-grained carbonaceous clastic rocks, ductile-brittle deformed zones, and late Hercynian granitic intrusions are the key prospecting criteria for the deformed zone-hosted gold deposits in the China-Kazakhstan-Kyrgyzstan-Uzbekistan Tian Shan gold ore belt.

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    Fractal analysis of breccias in the super-large Jinding Pb-Zn deposit and its geological implication
    ZHUANG Tianming, SONG Yucai, HOU Zengqian, ZHANG Chong
    2020, 27(2): 320-331. 
    DOI: 10.13745/j.esf.sf.2020.3.24
    Abstract ( 197 )   HTML ( 4 )   PDF (17129KB) ( 355 )  

    Previous studies have determined that a variety of complex breccias in the Jinding Zn-Pb deposit are genetically related to the salt diapirism. In this paper, breccia fractal analysis is used to determine two fractal dimensions of these breccias: Dr (the morphology of clasts) and Ds (particle size distribution), in order to understand their formation process. Dr indicates the morphological complexity and migration distance of the breccias or the degree of modification of the chemical process. Ds indicates the degree of brecciation and amount of energy that forms the breccias. Small Dr and Ds values imply that some of the breccias in Jinding were formed by diapirs of evaporite and gypsum-sand and near-in-situ brecciation of the host limestone. Bedded limestone-clast-bearing sandstone that is spatially transitional with these breccias have smaller Dr and larger Ds values, suggesting that limestone clasts in the sandstone were transported by evaporite rather than water into detrial sediments in a depositional system on the surface. Other breccias were formed by evaporite-sand-mud diapirs in a process where the breccia clasts were transported a certain distance, but the distance is limited and the clasts were not transported to the surface to enter a depositional system. Some of the breccias mentioned above also experienced post-brecciation fluid alteration and dissolution, resulting in a large Dr value. This study shows that evaporite diapir-related Zn-Pb deposits may contain breccias formed by a variety of diapir processes.

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    Zircon U-Pb geochronology and Hf isotopic compositions of igneous rocks from the Shuikoushan Pb-Zn deposit, Hunan Province, and their geological significance
    LI Yongsheng, ZHEN Shimin, YU Xiaofei, GONG Fanying, DU Zezhong
    2020, 27(2): 332-352. 
    DOI: 10.13745/j.esf.sf.2020.3.25
    Abstract ( 312 )   HTML ( 2 )   PDF (9247KB) ( 301 )  

    The Shuikoushan Pb-Zn polymetallic ore-field is an important nonferrous and precious metal-producing area in Nanling, China. Many intermediate-acidic igneous rocks occur in this area, and studying their geological and geochemical characteristics is critical for clarifying their diagenetic magmatic-metallogenic evolution and guiding ore exploration. The Laoyachao No. 4 and Yagongtang No. 3 grano-diorites have similar major and trace elemental compositions and have metaluminous and high-K calc-alkaline characteristics of shoshonitic series. The rocks display generally flat, right-dipping rare earth element patterns with enriched light rare earth elements, relatively flat high rare earth element patterns, and slightly negative Eu anomalies. Zircon laser ablation inductively coupled plasma mass spectrometry U-Pb dating showed that the Laoyachao granodiorite formed at 162.9±0.7 Ma, and the Yagongtang granodiorite intruded at 156.3±0.6 Ma. This suggests that igneous rocks in the Shuikoushan ore field mainly formed during the early Yanshanian and underwent multiple emplacement stages. In situ Hf isotope analyses revealed εHf(t) values ranging from -11.2 to -8.24 and two-stage Hf model ages (TDM2) of 1920-1734 Ma for the Laoyachao granodiorite as well as εHf(t) values of -13.51 to -6.23 and TDM2 ages of 2063-1601 Ma for the Yagongtang granodiorite. This showed that more mantle material was added to the Yagongtang magma. Based on geochemical compositions and previous studies of the Xianrenyan monzonite in the study area, we argue that the Laoyachao and Yagongtang granodiorites were mainly derived from the partial melting of basaltic rocks in the Mesoproterozoic lower crust. From 165 to 155 Ma, the Shuikoushan ore field was in an extensional-thinning setting, and the εHf(t) values of igneous rocks increased rapidly, indicating enhanced underplating of mantle magmas. Mineralization ages of the Shuikoushan Pb-Zn deposits were coeval with the formation of the Yagongtang and Xianrenyan plutons, indicating genetic relationships. Co-contribution of crustal and mantle ore-forming metals was critical to the formation of numerous Cu-Pb-Zn-Au deposits in the Shuikoushan area ore field.

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    Characteristics of the metallogenic system of the Shapinggou super-large porphyry molybdenum deposit in the Dabie orogenic belt, Anhui Province
    REN Zhi, ZHOU Taofa, YUAN Feng, ZHANG Huaidong
    2020, 27(2): 353-372. 
    DOI: 10.13745/j.esf.sf.2020.3.26
    Abstract ( 267 )   HTML ( 6 )   PDF (17943KB) ( 350 )  

    The ore-forming geodynamics, geochemical background, diagenesis, and mineralization mechanism of the porphyry molybdenum deposit in the East Qinling-Dabie molybdenum metallogenic belt have attracted the attention of researchers, but some mineralization problems still need to be addressed. In particular, the composition, formation, and evolution of the ore-forming system of the super-large molybdenum deposits need to be systematically summarized. Based on the theory on metallogenic systems of academician Zhai Yusheng, this paper selects the representative Shapinggou porphyry molybdenum deposit as the research object, and summarizes its geological characteristics on the basis of previous research results and the author’s preliminary work. The composition of the ore-forming system is analyzed and the distinguishing features of the system are identified through comparative research. The Shapinggou molybdenum deposit formed in the intracontinental extensional environment and is the product of the large-scale magmatic-mineralization events of the Mesozoic in Eastern China. Its ore-bearing porphyry originated from the ancient lower crust+Dabie complex+lithospheric mantle.Molybdenum mainly originated from the ancient lower crust+Dabie complex. Magma evolution and hydrothermal activity lasted approximately 24 Ma, forming a spherical giant porphyry molybdenum ore-forming system with a diameter of approximately 3 km.Ore-forming fluids have experienced early high temperature, medium salinity, higher oxygen fugacity, low alkalinity, low pH, low density, medium-term high temperature-medium temperature, low salinity-high salinity coexistence, low density-high density coexistence, low oxygen fugacity, rich CO2, evolution to late low temperature, low salinity, poor CO2, higher oxygen fugacity, higher alkalinity, higher pH, and higher density, including Cl.The precipitation of Mo due to phase separation caused by temperature, oxygen fugacity, and fluid boiling resulted in the formation of a large amount of molybdenum metal. Compared with the main porphyry molybdenum ore-forming systems in China and abroad, the metallogenic system of the Shapinggou molybdenum deposit has distinctive mineralization characteristics such as a single ore body, giant system, congenital rich, long gestation, multiple sources, high evolution, multiple periods, super-enrichment, etc. Applying the theory on metallogenic systems, we will continue to study the metallogenic and ore-forming processes of this super-large, high-grade porphyry molybdenum deposit to determine the genesis of the porphyry molybdenum deposits as well as search for similar deposits, both of which are of great significance.

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    The characteristics of trace elements and S, Pb, He and Ar isotopes in the Liyuan gold deposit in Shanxi Province, and their significance
    ZHEN Shimin, PANG Zhenshan, ZHU Xiaoqiang, XUE Jianling, FANG Yongcai, JIA Hongxiang, SHI Guangyao, WANG Dazhao, ZHA Zhongjian, SONG Xiaohang
    2020, 27(2): 373-390. 
    DOI: 10.13745/j.esf.sf.2020.3.27
    Abstract ( 273 )   HTML ( 4 )   PDF (9023KB) ( 276 )  

    The Liyuan gold deposit is an exploration breakthrough at the inner North China Craton in recent years. It has many types of mineralization with high research values. The Liyuan gold deposit occurs in the archaean Fuping group gneiss and mixed rocked granite, controlled by the NNE fault in the area, and mainly consists of explosive breccia-type orebody and quartz vein-type orebody. Ore minerals are mainly pyrite, galena and sphalerite, while gangue minerals are mainly quartz, sericite and K-feldspar, and alteration is mainly silicification, K-feldspar, sericitization and chloritization.The δ34S values of pyrite, chalcopyrite and sphalerite are 0.9‰-4.3‰, with an average of 3.0‰, which indicates that the source of sulfur mainly comes from the magma fluids.The δ34S values of galena are -12.8‰-1.4‰, with an average of -4.2‰. The increase in pH value may be the cause of the high negative δ34S value of galena. The variation range of Pb isotopes of metal sulfides is relatively small, and206Pb/204Pb values are 16.697-16.890,207Pb/204Pb values are 15.239-15.267,208Pb/204Pb values are 42.186-45.334, all of which fall near the evolution line of the lower crust. These variations indicate that the ore-forming fluid may have drenched the rich lower crust materials during the migration process. The3He/4He of pyrite is 0.27-1.04 Ra,40Ar/36Ar is 1194.61-5488.80, and38Ar/36Ar is 0.204-0.218, which indicates that the ore-forming fluid is mainly from the crust and partly from the mantle fluid, with the characteristics of magma fluid mixed with the crust and mantle. The characteristics of trace elements indicate that pyrite has the characteristics of magmatic-hydrothermal pyrite, and some materials of diabase vein and quartz porphyry may have been involved in the mineralization process. In conclusion, the Liyuan gold deposit is considered to be the magmatic-hydrothermal gold deposit related to the shallow magmatic intrusion. And the difference in REE and S-Pb-He-Ar isotopes, between the two types, is mainly due to the different precipitation mechanisms and mineral crystallization processes of the explosive breccia-type and quartz vein-type orebodies. In the deep part of the Liyuan gold deposit, it is possible to search for the veinlet-disseminated orebodies, and its mineralization is another specific manifestation of Yanshanian tectono-magmatic activity in the central Taihang Mountains.

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    Fluid inclusion and C-O-S-Pb isotopic studies of the Azhahada Cu-Bi deposit in Inner Mongolia, China
    WANG Yinhong, LIU Jiajun, ZHANG Mei, ZHANG Fangfang, WANG Kang, XIAN Xuechen, GUO Lingjun
    2020, 27(2): 391-404. 
    DOI: 10.13745/j.esf.sf.2020.3.28
    Abstract ( 205 )   HTML ( 0 )   PDF (13573KB) ( 273 )  

    The Azhahada quartz vein type copper-bismuth deposit is located in the middle segment of the Erlian-East Ujimqin polymetallic belt. Based on the fieldwork and microscope observations, as well as the mineral assemblages and crosscutting relationships of different veins, the hydrothermal mineralization of copper and bismuth at Azhahada has been divided into three stages from early to late: the quartz-pyrite-chalcopyrite early-stage I, the quartz-pyrite-chalcopyrite-chalcocite-bismuthinite-native bismuth-fluorite main-ore stage II, and the quartz-calcite late-stage III. The copper and bismuth mineralization is mainly hosted in the stage II quartz veins. The fluid inclusions at Azhahada are mainly composed of vapor-liquid two-phase inclusions. Microthermometric measurement results demonstrate that the vapor-rich inclusions in quartz of stage I are homogenized at temperatures of 224-427 ℃, with salinities of 16.0%-22.4% NaCleq, whereas the liquid-rich inclusions are homogenized at 229-410 ℃, with salinities of 9.2%-22.2% NaCleq. In main ore stage II, the vapor-rich and liquid-rich inclusions yield homogenization temperatures of 245-343 ℃, and 180-361 ℃, corresponding to salinities of 17.8%-20.5% NaCleq, and 10.5%-21.3% NaCleq, respectively. The liquid-rich inclusions in the quartz-calcite stage are homogenized at 132-262 ℃, with salinities of 3.4%-19.4% NaCleq. The ore-forming fluids are characterized by moderate temperature and moderate salinity. Laser Raman analyses of some individual representative inclusions suggest that their gaseous and liquid compositions are mainly H2O, with trace amount of CH4; thus, the fluids are dominated by the NaCl-H2O±CH4 system. The δ13CV-PDB values of calcite are in the range of -6.7‰ to -1.4‰, with δ18OV-SMOW values from -2.4‰ to+11.5‰. Combined with the δ18O-δ13C plots, it is suggested that the ore-forming fluids were mainly derived from magmatic water, with the addition of meteoric water in the late stage. The δ34SV-CDT values of pyrite are between 1.3‰ and 9.5‰, suggesting that the sulfur was dominantly derived from a magma source, and the enrichment of δ34S likely resulted from the involvement of country rocks. Lead isotopic compositions indicate that the pyrite has208Pb/204Pb ratios of 38.081-38.229,207Pb/204Pb of 15.561-15.602, and206Pb/204Pb of 18.270-18.383, respectively. All of these observations combined with the stable and radiogenic isotope results reveal that the ore-forming materials were mainly sourced from the magmatic reservoir with some strata components, and temperature decreasing and the local water-rock reactions might be the critical mechanism of ore precipitation.

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    Study on molybdenite Re-Os and zircon U-Pb ages of the Dongping tellurium-gold deposit in Hebei Province
    WANG Dazhao, LIU Jiajun, ZHAI Degao, ZHEN Shimin, WANG Jiang
    2020, 27(2): 405-419. 
    DOI: 10.13745/j.esf.sf.2020.3.29
    Abstract ( 214 )   HTML ( 5 )   PDF (8554KB) ( 299 )  

    The Dongping tellurium-gold (Te-Au) deposit is the largest alkaline pluton-related Te-Au deposit in China. Although many studies have been conducted on the deposit, its geochronology and genesis remain controversial. In this paper, we report on molybdenite Re-Os and zircon U-Pb ages to determine the timing and genesis of the Dongping Te-Au deposit. Two types of molybdenite have been identified. The disseminated molybdenite often co-exists with sulfides in syenite. Two disseminated molybdenite samples yield model ages of 401.1±2.1 and 402.8±2.1 Ma. The vein-type molybdenite contains native gold grains and occurs as aggregations or veinlets in quartz-sulfide veins. Two aggregated samples show model ages of 380.3±2.0 and 376.9±2.9 Ma. Magmatic zircons collected from quartz veins yield a crystallization age of 394±1.7 Ma, while the hydrothermal zircons are dated as 382±4.7 Ma. We argue that a Devonian mineralization stage existed in the Dongping Te-Au deposit, which was related to the magmatic-hydrothermal activity of the Shuiquangou alkaline complex. The deposit underwent metasomatism, activation, and enrichment processes driven by late Jurassic to early Cretaceous hydrothermal events, which eventually produced this large Te-Au deposit. Tellurium in Dongping deposit was mainly derived from partial melting of upper mantle and oceanic materials. Fluid exsolution and degasification of the Shuiquangou alkaline magma generated high oxygen fugacity medium- to meta-alkalic hydrothermal fluids and vapors, which are helpful for tellurium migration and enrichment.

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    Confirmation and metallogenesis of the Neoproterozoic rift in the western section of the northern margin of the North China Craton
    PENG Runmin, WANG Jianping
    2020, 27(2): 420-441. 
    DOI: 10.13745/j.esf.sf.2020.3.30
    Abstract ( 251 )   HTML ( 4 )   PDF (31606KB) ( 641 )  

    The Langshan-Zha'ertaishan metallogenic belt, consisting of the Tanyaokou, Huogeqi, Dongshengmiao and Jiashengpan large-superlarge Zn-Pb-Cu-Fe sulphide deposits hosted in the Proterozoic Zha'ertaishan Group, is an important hydrothermal mineralization belt of the Proterozoic passive continental margin in an extensional structural regime in the western section of the northern margin of the North China Craton. Most areas of the mineralization belt distribute in the Langshan Mountain district. Three of the four typical deposits, the Huogeqi, Dongshengmiao and Tanyaokou deposits, occur in this region. It becomes an important scientific issue whether all the Mesoproterozoic Zha'ertaishan Group in the Langshan Mountain's core area and the three deposits hosted in the Zha'ertanshan Group be re-classified as the Neoproterozoic, after the 2010 discovery of acidic volcanic rocks with zircon ages of 816-805 Ma in the southwestern Langshan Mountain. Evidence includes (1) the minimum detrital zircon age of 1155 Ma for the meta-sedimentary rocks of the Precambrian strata with calcite marble from southern Langshan Mountain, (2) the detrital zircon age peaks at 1862-1762 (youngest age 1732 Ma) and 2448 Ma for the Liuhongwan Formation of the Zha'ertaishan Group with dolomate marble in the Tanyaokou district, (3) the occurrence of Neoproterozoic (887.4±9.1 Ma) meta-mafic volcanic rocks in the host formation of the Langshan Group in the north side of the Langshan Mountain, and (4) the “interbedding” of siliceous bands containing barite and microcrystal feldspar with pyrites, sometimes sphalerites and pyrrhotite and galena, with δ34S values of these four sulfide minerals varying between 17.60‰ and 21.97‰ and showing the characteristics of hydrothermal exhalation. Based on the evidence, we suggest the following: (1) the Zha'ertaishan Group hosting dolomite marble in the Tanyaokou district, and the Precambrian strata (formerly called the Zha'ertaishan Group) hosting acidic volcanic rocks and calcite marbles in southwest Langshan, were deposited in two different rift basins; (2) the Mesoproterozoic rifts and hydrothermal metallogenic systems in the south side of the Langshan Mountain developed the Tanyaokou and Dongshengmiao deposits in the Mesoproterozoic Zha'ertaishan Group; and (3) the Neoproterozoic rift and hydrothermal metallogenic system in the north side of the Langshan Mountain developed the Huogeqi orefield in the Neoproterozoic Langshan Group. The Huogeqi deposit hosted in the Neoproterozoic Langshan Group obviously appears to be a transitional type of mineral deposits between the SEDEX and VMS types with a bias towards SEDEX type.

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