Tectono-Metallogenic System in the Altay Orogenic Belt,China

The Altay orogenic belt of China is an important metallogenic belt of base metals, rare metals and gold. The main orogenic-metallogenic epoch is the Hercynian (Late Palaeozoic). Hercynian orogeny underwent two tectonic stages: the early volcano-passive continental margin extension (D1-D2) and late subduction-collision (D3-P). There correspondingly developed two different metallogenic systems. One is the stratabound massive sulphide and iron metallogenic system related to volcano-passive continental margin, and the other is the epigenetic gold and granite-associated rare metals system formed by collision. Very few mineralizations were formed during the subduction time.

Magmatic-Hydrothermal Superlarge Metallogenic Systems——A Case Study of the Nannihu Ore Field

Located in the Qinling （秦岭） molybdenum metallogenic belt on the southern margin of North China craton, the Nannihu （南泥湖） molybdenum （-tungsten） ore field, consisting of the Nannihu, Sandaozhuang （三道幢）, and Shangfang （上房） deposits, represents a superlarge skarn-porphyry molybdenum （-tungsten） accumulation. Outside the ore field, there are some hydrothermal lead-zinc-silver deposits found in recent years, for example, the Lengshuibeigou （冷水北沟）, Yindonggou （银涧沟）, Yangshuwa （杨树凹）, and Yinhegou （银河沟） deposits. Ore-forming fluid geochemistry indicates that these deposits belong to the same metallogenic system. The hydrothermal solutions were mainly derived from primary magmatic water in the early stage and from the mixture of the primary magmatic water and meteoric water in the later stage, with an obvious decreasing tendency in temperature, salinity and gas-liquid ratio of fluid inclusions. Sulfur and lead isotope data show that the ore-forming substances and related porphyries were mainly derived from the lower crust, and a hidden magmatic chamber is indicated by aeromagnetic anomaly and drill hole data indicate that the Nannihu granite body extends to being larger and larger with depth increasing. The large-scale mineralization was the consequence of lithospheric extension during the late stage of the tectonic regime when the main compressional stress changed from NS-trending to EW-trending.

Metallogenic Systems on the Paleocontinental Margin of the North China Craton

The North China Craton (NCC) is one of the largest blocks composing the continent. Different types of continental margins well developed around the NCC, along with lots of metallogenic systems of different metals and different times. Based on the study on the structural evolution of the NCC, the authors made a new division of tectonic units of the NCC. Through an analysis of the data of 1:25000 geochemical survey on stream sediments, regional geochemical features of main ore-forming elements including Au, Ag, Cu, Pb, Zn, W, Ni, Co and Mo of the NCC are discussed in the paper. Then different metallogenic systems and their forming processes and geodynamics are discussed in detail. At last, temporal and spatial distribution regularities are summarized and ten favorable ore-control factors on the paleocontinental margins are put forward, including (1) abundance of ore sources; (2) rendezvous of ore-forming fluids; (3) high thermo-dynamic anomaly; (4) remarkable Earth crust-mantle interaction; (5) cluster of macroscopic structures and their long activities; (6) diversity of ore-forming environments; (7) long geohistory; (8) multiforms of critical transitional ore-forming mechanisms; (9) multi-staged and superimposed ore-formation; and (10) suitable preservation condition.

Composite Metallogenic Systems in the Weihai Area of Shandong and Evolution of Continental Dynamic Regimes

Based on 9 sheets of 1：50,000-scale regional geological survey and guided by the theory of metallogenic systems and integrated analyses of the structural and metallogenic features, this paper hereby puts forward the composite metallogenic systems of the Weihai area, Shandong Province, aiming at solving the problems on the origins and ore-controlling structures of the numerous deposits in the area. Its scientific significance is reflected in the following three aspects： （1） The basic features of the composite metallogenic systems can be recognized, which consist of two types： the Proterozoic metamorphic-hydrothermal metallogenic system and the Mesozoic magmatic-hydrothermal metallogenic system （i.e. the Indosinian-early Yanshanian contact metasomatic metallogenic series and the mid-late Yanshanian magmatic-hydrothermal metallogenic series）. The two series display arcuate and NW-right lateral arrangements and a N-S parallel zonal distribution respectively, with the corresponding mineral assemblages being Au＋Ag＋Pb＋Zn, etc.; and Cu＋Mo＋Fe, Au＋Ag＋Cu＋Pb- Zn＋Mo＋Co-Ni＋sulfides＋silicides＋K-feldspar, etc. （2） The composite metallogenic systems may be used to interpret the complicated genetic relations of the deposits. Through analyses of the relations between the three main metallogenic intervals and their corresponding source rock series （the Jingshan and Rongcheng groups; the Wendong super-unit and the early-middle Yanshanian Weideshan super-unit; and the mid-late Yanshanian Weideshan and Laoshan super-units） as well as a case study of the Fanjiabu gold deposit, we have distinguished the consanguinity between the contact metasomatic （skarn-type） metallogenic series and the magmatic-hydrothermal metallogenic series as well as the noncognate superposition between the two and the metamorphic-hydrothermal metallogenic system. （3） The composite metallogenic systems are easily related to the evolution of continental dynamic regimes. The formation of the metamorphic-hydrothermal metallogenic system has undergone transformations of three different types of tectono-dynamic regimes from extension→compression→ shearing; that of the contact metasomatic （skarn-type） metallogenic system from compression→extension→compression; and that of the magmatic-hydrothermal metallogenic system from extension →subductive compression of the Pacific Plate. The evolutions of the three types are all attributed to the opening-closing or divergence-convergence of the paleocontinent, and all their mineralization corresponds to the interval of transformation from the end of convergence to early integration of the Weihai paleocontinent. All these will benefit our deeper study of the dynamics of continental metallogenic processes.

Characteristics of the Composite Metallogenic System along the Jilin Paleocontinental Margin and the Evolution of Continental Dynamic Regimes

In view of the existing problems about the metallogenic epoch and origin of the complex along the Jilin paleocontinental margin, we propose the composite metallogenic system of the Jilin old land, based on the theory of metallogeny and from the continental dynamics and comprehensive analysis on the metallogenic characteristics. Its scientific theory is demonstrated by the following aspects: (1) Screening and analysis of the multi-stage super-imposition and sequences. The composite ore-forming system consists mainly of three types: the divergent-type epicontinental metallogenic system on the southern margin, the convergent-type epicontinental metallogenic system on the northern margin and the strike-slip-type epicontinental metallogenic system on the northeastern margin. Their major metallogenic epochs are Archean-Proterozoic, Variscan and Yanshanian respectively. (2) Comprehensive analysis of the genetic relations of the complicated deposits. The above-mentioned three types all indicate a consanguinity among granites, vein rocks and gold deposits, correspondence with geochemical elements, and unicity showing the same activities of mantle derived fluids and multi-source origin of ore-forming substances. (3) As to the mechanisms for mineral concentration, in addition to the sources, we also focus on the co-actions of permeability, vibration, gas-liquid state alternation and abrupt changes of flow velocity during the movement of ore-forming liquids, as well as the extraction and communication of multi-sequence circulating liquids. (4) It is helpful for establishing the relationship between metallogeny and the evolution of continental dynamic regimes, i.e., the ore-controlling correlations between the ore-forming elements-metallogenic series-metallogenic systems-composite metallogenic system and ore-controlling structural features (stratabound, primary and branching types)-regional faulting or secondary continental extension and collision-transformation of different continental dynamic types (divergent, convergent and strike-slip)-the evolution process of the whole old land for the Jilin old land margin. All these are helpful for further researches on the continental metallogenic dynamics.

Research on Superimposed Metallogenic System

As located in the junction of three tectonic plates (the Eurasian plate, the Indian plate and the west Pacific plate), the China continent shows complex regional metallogenic features due to tectonic evolution of “micro-plates, polycycle tectonic movements”. Well developed superimposed metallogenic systems have constituted one of the regional metallogenic features in China. Through the study on superimposed metallogenic system of the middle and lower reaches of the Yangtze River and of the Yuebei basin (northern Guangdong Province), the authors put forward some basic combination pattern of sedimentary-magmatic superimposed metallogenic system and summarize its forming conditions (controlling factors).

Preliminary Study on the Metallogenic System of Mafic Large Igneous Provinces(MLIPs)

Large igneous provinces（LIPs）generally refer to the different types of the igneous rocks,which intrude in a short time,ranging in area from 50000 to 100000 km;（Sheth,2007;Bryan et al.,2008）.While the mafic large

METALLOGENIC SYSTEM OF DACHANG TIN- POLYMETALLIC ORE FIELD

The Dachang tin polymetallic ore field in northern Guangxi, China, lies in a mid late Paleozoic rift that borders up the southern boundary of the Jiangnan Xuefeng Massif. As a giant ore deposit, it deposited in middle of the Nandang Hechi metallogenic zone. The ore hosting strata are of the Devonion, which shows the evident characteristics of polymetallic elements, i.e., Sn, Zn, Pb, Sb, As, Cu, Ag, In, Ge, Cd, et al., and over 1 000 000 t tin reserves.

Cassiterite U-Pb dating of the Yelonggou pegmatite-type lithium deposit in western Sichuan and its metallogenic age constraints

1.Objective Pegmatite hosts important resource of rare metals,e.g.,lithium(Li)and beryllium(Be).In recent years,increasingly more studies were dedicated to characterize and unravel the formation of pegmatite-type deposits,for which accurate dating of pegmatite formation and mineralization is essential.The Songpan-Ganzi orogenic belt is a major rare metal metallogenic belt in China,hosting many important pegmatite-type Li deposits,including the Lijiagou,Dangba,Jiajika,Yelonggou,Cuola,and Declalongba.Radiometric age data(mica Ar-Ar and zircon/cassiterite U-Pb)from these Li deposits are sparse,ranging from 210 to 152 Ma.However,obtaining reliable zircon U-Pb dates can be a challenge due to the strong decidualization in pegmatites.As a result,the formation and mineralization ages of these rare metal pegmatites remain controversial,which hampers the development of pegmatite-type metallogenic model for the Songpan-Ganzi orogenic belt.

Tectonic Setting and Metallogenic System of North China Block Margins

The paleocontinental margins have frequent and intensive tectonic movement and various ore forming processes. According to their tectono dynamic characteristics, the paleocontinental margins can be classified into three types: the divergent, the convergent and the transformational. Each type has its specific geological geochemical processes and metallogenic system. The paper discusses the tectonic evolution and ore forming features of the North China block margins, puts forward conceptions such as complexity, variety and multi stage development of metallogenic evolution in the paleocontinental margins, and expounds five factors controlling the formation of large superlarge ore deposits in the paleocontinental margins: (1) channelway, (2) rendezvous of fluids, (3) abundance of ore source, (4) thermo dynamic anomaly, (5) long duration of structural activities.

Yanshanian Magma-Tectonic-Metallogenic Belt in East China of Circum-Pacific Domain(Ⅱ): Lithosphere-Asthenosphere System and Metallogenic Environment

This paper shows that the catastrophe of lithosphere asthenosphere system (LAS) is developed for the Yanshanian metallogenic belt in the East China. Two types of Yanshanian disturbed LAS and metallogenesis in the East China are recognized: great lithosphere thinning and thickening in the compressional orogenic environment, and the related Andes type and Hercyn type metallogenesis, respectively. Great amount of the juvenile and hot mantle materials and the reactivated hot lower crustal materials replaced, heated and injected into the cold lithosphere and crust are believed to be a fundamental source and a basic deep environment for the Yanshanian metallogenic explosion. Reactivated and active discontinuities on the lithosphere scale are considered to be the main ore storing space of the metallogenic zone. Large magma tectonic metallogenic system is necessary for the formation of large cluster area of ore deposit. The eastern China is believed to have large potential for prospecting of ore deposits in terms of the metallogenic environment.

Metallogenic systems related to Mesozoic and Cenozoic granitoids in South China

Large scale mineralizations of nonferrous, precious, and rare metals took place in South China in Mesozoic and Cenozoic Eras, which were mostly closely related with granitic magmatisms of different sources and features. Four metallogenic systems related to Mesozoic and Cenozoic granitoids are put forward in this paper. They are: (i) the porphyry-epithermal copper-gold system related to calc-alkaline volcanic-intrusive magmatism, (ii) rare metal (mainly W, Sn, Ta, Nb, etc) metallogenic system related with continental crust re-melting type granitoids, (iii) copper and polymetallic metallogenic system related with intra-plate high potassium calc-alkaline and shoshonitic magmatism, and (iv) Au-Cu and REE metallogenic system related to A-type granites. The main characteristics of these systems are briefly discussed. These Mesozoic and Cenozoic granitoids of different sources were the products of different periods of lithosphere evolution in that area under different tectonic-dynamic environments. Fundamentally speaking, however, the granitoids and related metallogeneses are the results of mantle-crust interactions under a tensile tectonic environment in South China.

Geological Fluid Mapping in the Tongling Area:Implications for the Paleozoic Submarine Hydrothermal System in the Middle-Lower Yangtze Metallogenic Belt,East China

The Tongling area is one of the 7 ore-cluster areas in the Middle-Lower Yangtze metallogenic belt, East China, and has tectonically undergone a long-term geologic history from the late Paleozoic continental rifting, through the Middle Triassic continent-continent collision to the Jurassic-Cretaceous intracontinental tectono-magmatic activation. The Carboniferous sedimentary-exhalative processes in the area produced widespread massive sulfides with ages of 303-321 Ma, which partly formed massive pyrite-Cu deposits, but mostly provided significant sulfur and metals to the skarn Cu mineralization associated with the Yanshanian felsic intrusions.To understand the Carboniferous submarine hydrothermal system, an area of about 1046 km^2 was chosen to carry out the geological fluid mapping. Associated with massive sulfide formation, footwall sequences 948 m to 1146 m thick, composed of the Lower Silurian-Upper Devonian sandstone, siltstone and thin-layered shale, were widely altered. This hydrothermal alteration is interpreted to reflect largescale hydrothermal fluid flow associated with the late Paleozoic crustal rifting and subsidence. Three hydrothermal alteration types, i.e., deep-level semiconformable siliclfication （S1）, fracture-controlled quartz-sericite-pyrite alteration （S2-3）, and upper-level sub-discordant quartz-sericite-chlorite alteration （D3）, were developed to form distinct zones in the mapped area. About 50-m thick semiconformable silicification zones are located at -1-km depth below massive sulfides and developed between an impermeable shale caprock （S1） and the underlying Ordovician unaltered limestone. Comparisons with modern geothermal systems suggest that the alteration zones record a sub-seafioor aquifer with the most productive hydrothermal fluid flow. Fracture-controlled quartz-sericite-pyrite alteration formed transgressive zones, which downward crosscut the semiconformable alteration zones, and upwards grade into sub-discordant alteration zones that enveloped no economic stringer- stockwork zones beneath massive sulfides. This transgressive zone likely marks an upfiow path of high- flux fluids from the hydrothermal aquifer. Lateral zonation of the sub-discordant alteration zones and their relationship to overlying massive sulfide lenses suggest lateral flows and diffusive discharging of the hydrothermal fluids in a permeable sandstone sequence. Three large-sized, 14 middle-small massive sulfide deposits, and 40 massive sulfide sites have been mapped in detail. They show regional strata- bound characters and two major styles, i.e., the layered sheet plus strata-bound stringer-style and the mound-style. Associated exhalite and chemical sedimentary rock suites include （1） anhydrite-barite, （2） jasper-chert, （3） Mg-rich mudstone-pyrite shale, （4） barite lens, （5） siderite-Fe-bearing dolomite, and （6） Mn-rich shale-mudstone, which usually comprise three sulfide-exhalite cyclic units in the area.The spatial distribution of these alteration zones （minerals） and associated massive sulfdes and exhalites, and regional variation in δ^34S of hydrothermal pyrite and in δ^18O-δ^34C of hanging wall carbonates, suggest three WNW-extending domains of fluid flow, controlled by the basement faults and syn-depositional faults. Each fluid domain appears to have at least two upflow zones, with estimated even spacing of about 5-8 km in the mapped area. The repeated appearance of sulfide-sulfate or sulfide-carbonate rhythmic units in the area suggests episodically venting of fluids through the upfiow conduits by breaking the overlying seals of the hydrothermal aquifer.

Metallogenic Effect of Transition of Tectonic Dynamic System

Tectonic dynamic system transition, one of the main factors in metallogenesis, controls metallogenic fluid movement and ore body location in orefields and on an ore deposit scale (mainly in the continental tectonic setting), and even the formation and distribution of large-scale deposit clusters. Tectonic dynamic system transition can be classified as the spacious difference of the tectonic dynamic system in various geological units and the temporal alteration of different tectonic dynamic systems. The former results in outburst of mineralization, while the latter leads to the metallogenic diversity. Both of them are the main contents of metallogenic effect of tectonic dynamic system transition, that is, the alteration of dynamic system, the occurrence of mineralization, and the difference of regional tectonic dynamic system and metallogenic diversity. Generally speaking, the coupling of spatial difference of tectonic dynamic system and its successive alternation controlled the tempo-spatial evolution regularity of mineralization on a larger scale. In addition, the analysis of mineralization factors and processes of typical ore deposits proved that the changes of tectonic stress field, the direct appearance of tectonic dynamic system transition, may lead to the accident of mineralization physical-chemical field and the corresponding accidental interfaces were always located at ore bodies.

Gravity and Magnetic Evidence for the Geological Setting of Major Mineral Systems of the Main Metallogenic Belts in South China: A Qualitative Analysis

South China is characterized by large-area multistage magmatism.It boasts a huge number of polymetallic deposits such as W-Sn,Cu-Au,rare earth deposits,thus serving as a"giant granary"of metal mineral resources in China(Lüet al.,2021).

Genesis, metallogenic model, and prospecting prediction of the Nibao gold deposit in the Guizhou Province, China

Southwestern Guizhou province is one of China’s most important distribution areas of Carlin-type gold deposits. The Nibao deposit is a typical gold deposit in southwestern Guizhou. To elucidate the genesis of the Nibao gold deposit, establish a metallogenic model, and guide prospecting prediction, we systematically collected previously reported geological, geochemical, and dating data and discussed the genesis of the Nibao gold deposit,based on which we proposed the metallogenic model.Earlier works show that the Nibao anticline, F1 fault, and its hanging wall dragged anticline(Erlongqiangbao anticline) were formed before or simultaneously with gold mineralization, while F2, F3, and F4 faults postdate gold mineralization. Regional geophysical data showed extensive low resistivity anomaly areas near the SBT(the product of tectonic slippage and hydrothermal alteration)between the P2/P3 and the strata of the Longtan Formation in the SSE direction of Nibao anticline in the lower plate of F1 and hanging wall dragged anticline(Erlongqiangbao anticline), and the anomaly areas are distributed within the influence range of anticlines. Simultaneously, soil and structural geochemistry show that F1, Nibao anticline,Erlongqiangbao anticline, and their transition areas all show good metallogenic elements(Au, As, and S) assemblage anomalies, with good metallogenic space and prospecting possibilities. There are five main hypotheses about the source of ore-forming fluids and Au in the Nibao gold deposit:(1) related to the Emeishan mantle plume activity;(2) source from the Emeishan basalt;(3) metamorphic fluid mineralization;(4) basin fluid mineralization;(5) related to deep concealed magmatic rocks;of these, the mainstream understanding is the fifth speculation. It is acknowledged that the ore-forming fluids are hydrothermal fluids with medium–low temperature, high pressure, medium–low salinity, low density, low oxygen fugacity, weak acidity, weak reduction, and rich in CO_(2)and CH_(4). The fluid pressure is 2–96.54 MPa, corresponding to depths of 0.23–3.64 km. The dating results show that the metallogenic age is ~141 Ma, the extensional tectonic environment related to the westward subduction of the Pacific Plate. Based on the above explanation, the genetic model related to deep concealed magmatic rocks of the Nibao gold deposit is established, and favorable prospecting areas are outlined;this is of great significance for regional mineral exploration and studying the genesis of gold deposits.

MECHANISM OF THE BASIN-MOUNTAIN METALLOGENIC SYSTEM IN HIMALAYAN PERIOD IN SANJIANG CONCENTRATION AREA,SOUTHWEST CHINA

Sanjiang (Jinshajiang River,Lancangjiang River and Nujiang River) concentration area in southwest China is within the Tethys\|Himalayan tectonic domain,and it is the main area where develops Himalayan movement and relative ore deposits,such as Yulong super large Cu\|Mo deposit,Jinding super large Pb\|Zn deposit,etc ,in West China.So it is a best place to study Himalayan movement and metallogeny.1 Metallogenic geological background Sanjiang concentration area has passed complex Tethys tectonic development before Cainozoic era,and it begins Himalayan inland basin\|mountain tectonic development at the end of Yanshan movement.It commonly accepts autochthonous platform type deposits since Mesozoic era,and the basin\|mountain tectonic pattern has already appeared.Old metamorphic terrains and paleo\|Tethys orogenic belts become “mountains”,as well as microplateforms sink to become “basins”.Comparing to Mesozoic basins,Eogene basins are many smaller garben\|type extension basins or strike\|slip extension basins on the background of big large basins.

The first discovery of Xinlong epithermal gold deposit in southern margin of the Bangonghu-Nujiang metallogenic belt: A new expansion of gold prospecting in Northern Tibet

The Xinlong gold deposit is located in Niyma County,Naqu area of Tibet and was discovered by the Institute of Mineral Resources,Chinese Academy of Geological Sciences through the 1∶50000 mineral geological survey.The ore bodies occur in the Zenong Group volcanic rocks in the middle section of the central Lhasa subterrane and are structurally controlled by the NNW-striking faults.Four ore bodies have been found,exhibiting cloddy,dense-sparse,disseminated,and breccia structures.The ore minerals are mainly tetrahedrite group minerals,and other ore minerals include pyrite,chalcopyrite,nevskite,bornite,anglesite,native gold,and silver-gold bearing selenide,etc.The types of alteration are dominated by silicification,as well as middle-and high-graded argillization.The alteration mineral assemblages contain quzrtz,pyrophyllite,and kaolinite.The Zaliela Formation volcanic rocks of Zenong Group are silicified by later hydrothermal fluid with vuggy quartz in some fractured zones.The middle-and high-graded argillization are characterized by pyrophyllitization and kaolinization.The Xinlong gold deposit shows great metallogenetic potentiality and has been revealed by 1∶10000 geological mapping,IP sounding,and trial trenching in the mining area.Combined with the regional metallogenic geological setting,we suppose that a potential epithermal gold belt probably exists in the middle of the Lhasa terrane.The discovery of the Xinlong gold deposit opens a new chapter for the gold prospecting in Northern Tibet.

Genesis of the Nuri Cu-W-Mo Deposit,Tibet,China:Constraints from in situ Trace Elements and Sr Isotopic Analysis of Scheelite

The Nuri deposit is the only Cu-W-Mo polymetallic deposit with large-scale WO3 resources in the eastern section of the Gangdese metallogenic belt,Tibet,China.However,the genetic type of this deposit has been controversial since its discovery.Based on a study of the geological characteristics of the deposit,this study presents mineralization stages,focusing on the oxide stage and the quartz-sulfide stage where scheelite is mainly formed,referred to as Sch-A and Sch-B,respectively.Through LA-ICP-MS trace element and Sr isotope analyses,the origin,evolutionary process of the oreforming fluid and genesis of the ore deposit are investigated.Scanning Electron Microscope-Cathodoluminescence(SEMCL)observations reveal that Sch-A consists of three generations,with dark gray homogenous Sch-A1 being replaced by relatively lighter and homogeneous Sch-A2 and Sch-A3,with Sch-A2 displaying a gray CL image color with vague and uneven growth bands and Sch-A3 has a light gray CL image color with hardly any growth band.In contrast,Sch-B exhibits a‘core-rim’structure,with the core part(Sch-B1)being dark gray and displaying a uniform growth band,while the rim part(Sch-B2)is light gray and homogeneous.The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore-forming fluid in the Nuri deposit originated from granodiorite porphyry and,later on,some country rock material was mixed in,due to strong water-rock interaction.Combining the O-H isotope data further indicates that the ore-forming fluid in the Nuri deposit originated from magmatic-hydrothermal sources,with contributions from metamorphic water caused by water-rock interaction during the mineralization process,as well as later meteoric water.The intense water-rock interaction likely played a crucial role in the precipitation of scheelite,leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz-sulfide stage,while also causing a gradual decrease in oxygen fugacity(fO2)and a slow rise in pH value.Additionally,the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic-hydrothermal scheelite.Therefore,considering the geological features of the deposit,the geochemical characteristics of scheelite and the O-H isotope data published previously,it can be concluded that the genesis of the Nuri deposit belongs to porphyry-skarn deposit.

Geology and mineralization of the Dongping supergiant alkalic-hosted Au-Te deposit(>100 t Au)in Northern Hebei Province,China:A review

The Dongping deposit is the largest alkalic-hosted gold deposit in China containing>100 t of Au.This paper presents a new understanding for Dongping ore system,based on the previous studies.The mineralization originally occurred at 400-380 Ma,simultaneous with emplacement of the Shuiquangou alkaline complex,and was overprinted by the hydrothermal activity in the Yanshanian.Isotope compositions of ores indicate metals of the deposit are mainly provided by the Shuiquangou complex.Ore-forming fluids are characterized by increasing oxygen fugacity and decreasing sulfur fugacity,while tellurium fugacity increased in the Stage II-2 and decreased in Stage II-3.These systematic changes are closely related to the processes of mineral precipitation and fluid evolution.Sulfide precipitation from Stage Ⅰ to Stage Ⅱ was triggered by fluid boiling,which leads to the precipitation of Pb-Bi-Te,due to decrement of sulfur fugacity.Condensation of gas phase containing high concentration of H_2Te leads to precipitation of Te-Au-Ag minerals and native tellurium.Based on these hypotheses,this paper present a polyphase metallogenic model as follow.During the Devonian,fluids were released from alkaline magmas,which carried ore-forming materials form the surrounding rocks and precipitate the early ores.During the Jurassic-Cretaceous,fluorine-rich fluids exsolved from highly factionated Shangshuiquan granite,which extracted and concentrated Au from the Shuiquangou complex and the Sanggan Group metamorphic rocks,and finally formed the Dongping gold deposit.