A New Genetic Type of Gold Deposits-Meso-Epithermal Carbonate-Type Gold Deposits as Exemplified by the Baguamiao Suprlarge Gold Deposit

Gold deposits of the meso-epithermal carbonate type were first proposed based on the study of the Baguamiao gold deposit.This new type of gold deposits has many unique characteristics as follows:(1)Obviously strata-bound.The gold deposits are hosted in Middle Devonian turbidite formations;(2)Structrually controlled.Struc-ture is an important factor leading to metallogenesis of this type of gold deposits.The shape and distribution of orebodies are controlled by byittle-ductile shear zones;(3)Multi-stage wall-rock alteration.According to the characteristics of mineral assemblage,gold mineralization can be classified into three stages in association with various wall-rock al-terations.Wall-rock alterations closely genetically related to the gold mineralization are ankerization ,silicification,pyrrhotization and pyritization ;(4)Mineral compositions of the orebodies are mainly pyrrhotite,pyrite,marcasitolite,chalcopyrite,quartz,ankerite,and sericite.Gold mineralization is associated closely in space and time with iron sulfides;(5)Rare elements and REE in ores are low in contents relative to those of the crust.Au content varies from 1.91g/t to 11.15g/t ,averaging 5.5g/t;(6)Studies of sulfur,hydrogen,oxygen and carbon isotopes in main gangue minerals (quartz and ankerite)indicate that fluids and ore-forming materials came from deep-seated sources;(7)Three types of inclusions are recognized in terms of their composition and the vapor amounts of inclusions.The homogenization temperatures of inclusions range from 210℃to 310℃,averaging 230℃,showing that this type of gold deposits belongs to the meso-epithermal type;(8)Metallogenic age of this type of gold deposits is similar to that of the collision between the Yangtze Plate and the North China Plate,indicating that gold deposits of this type are genetically related to continental-margin plate activity.     

Gold Deposits in the Sanandaj–Sirjan Zone: Orogenic Gold Deposits or Intrusion‐Related Gold Systems?

Most of the known large gold deposits in Iran are located along the Sanandaj–Sirjan Zone, western Iran, which hosts a wide range of gold deposit types. Gold deposits in the belt, hosted in upper Paleozoic to upper Mesozoic volcano‐sedimentary sequences of lower greenschist to lower amphibolite metamorphic grade, appear to represent mainly orogenic and intrusion‐related gold deposit types. The largest resource occurs at Muteh, with smaller deposits/occurrences at Zartorosht, Qolqoleh, Kervian, Qabaqloujeh, Kharapeh, and Astaneh. Although a major part of the gold deposits in the Sanandaj–Sirjan Zone are related to metamorphic devolatilization, some deposits including Muteh and Astaneh are related to short‐lived disruptions in an extensional tectonic regime and are associated with magma generation and emplacement. The age of gold ore formation in the orogenic gold deposits is Late Cretaceous to Tertiary, reflecting peak‐metamorphism during regional Cretaceous–Paleocene convergence and compression. The Oligocene to Pliocene age of most intrusion‐related gold systems is consistent with the young structural setting of the gold ore bodies; these deposits are sequestered along normal faults, correlated with Middle to Late Tertiary extensional tectonic events. This relationship is comparable to the magmatic‐metallogenetic evolution of the Urumieh‐Dokhtar magmatic arc, where the number of different types of gold‐copper deposits and the magnitude of the larger ones followed development of a magmatic arc. The appropriate explanation may be related to two different stages of gold mineralization consisting of a first compressional phase during the Late Cretaceous to Early‐Middle Tertiary, which is related to orogenic gold mineralization in the Qolqoleh, Kervian, Qabaqloujeh, Kharapeh, and Zartorosht deposits, and the extensional phase during the Eocene to Pliocene that is recognized by young intrusion‐related gold mineralization in the Muteh and Astaneh deposits.     

Jiaodong Granitoids and Gold Mineralization

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Source Strata of Gold in Western Guangdong—Their Identification and Significance in Gold Mineralization

Strata of different geological periods extensively outcrop in western Guang-dong Province, but most gold deposits are restricted to the Middle-Late Proterozoic Yunkai Group and the Cambrian Bacun Group,showing obvious strata-boun character-istics .Gold abundance and trace element geochemistry of the Yunkai and Bacun Groups are compared with those of the Ordovician and Silurian strta.The Yunkai Group is considered to be the source strata for gold mineralization in the region.     

Hydrothermal Gold Deposits in Pingle Depression: a Case Study at Gaocheng Quartz Vein-hosted Gold Deposit

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Gold Deposits in Precambrian Banded Iron-Formations——A Case Study of the Dongfengshan Gold Deposit

This paper deals with a preliminary study of 13 localities of Precambrian iron-formations in the Jiamusi median massif and determination of the gold eontent of 391 samples. It has been ascertained that the gold deposits are strictly controlled by the iron-formations and exhibit obvious stratabound features. On that basis, the paper principally discusses gold migration and enrichment. Abundant Mn and Co are contained in primary sediments of the Dongfengshan-type gold deposits, which strongly supports and supplements the idea that the gold deposits of the same kind in the world are of metamorphosed volcanoexhalative-sedimentary origin.     

Analysis of Gold Mineralization in Tectonic-Magmatic Environment: A Case Study of Ertix Gold Metallogenic Zone

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Geological Characteristics and Occurrence of Gold in the Xiling Gold Deposit,Jiaodong Peninsula北大核心CSCD

西岭金矿床是胶东金矿集区内近来新发现的超大型破碎蚀变岩型金矿床(475吨@4.56 g/t),位于著名的三山岛金矿床的东侧。本文在详实的野外地质观察的基础上,系统介绍了西岭金矿床的基础地质特征,并运用光学显微镜和扫描电镜观察,结合电子探针分析,系统研究了西岭金矿床金的赋存状态。西岭金矿床大量金矿物(银金矿和自然金)主要赋存在Ⅱ阶段石英-黄铁矿和Ⅲ阶段灰石英-多金属硫化物脉中。西岭金矿床金矿物主要有晶隙金、裂隙金和包体金三种赋存状态,以晶隙金为主。金的主要载体矿物为黄铁矿,次为石英、黄铜矿和方铅矿等。金矿物粒度大小包括粗粒金、中粒金、细粒金和微粒金,以细粒-微粒为主。金矿物形态有粒状、叶片状、线状、钩状、枝杈状和哑铃状等,以粒状为主。金矿物成分以Au和Ag为主,含微量的Cu、Cr、Fe、Ni、Te、S等元素。金成色为685~831,以银金矿为主,含少量自然金。综合地质和地球化学特征,西岭金矿床为蚀变岩型金矿床,是由早白垩世中温岩浆热液充填-交代形成。     

Gold Occurrence and Ore Genesis,Yata Micro—Disseminated Gold Deposit,Guizhou,Southwest China

The mode of occurrence of gold in the Yata micro-disseminated gold deposit is ap-proached through chemical phase studies coupled with ore-dressing monitoring and micro-beam analysis.The results showed that gold occurred for the most part as ultra-microscopic particles adsorbed on the surfaces or fracture planes of pyrite and other sulphides.The proportions of gold of different occurrences were estimated solutions containing nanometer-sized gold particles were prepared following the hydrolysis-reduction procedure and the adsorption of nanometer-sized gold on ordinary sulphides and rocks was experimentally determined.It is evident that sulphides are good adsorbents of gold and this is consistent with geological observations.     

Beiya Gold Deposit,Heqing County,Yunnan——One of China's Ten Biggest Gold Deposits

<正>The Beiya gold polymetallic ore district covers an area of 22.06 km2 and is located 47.5 km away in the direction 172°from Heqing county seat of northwestern Yunnan.Its geographical coordinates are 100°11′15″–100°13′00″E and6°07′30″–26°10′30″N.Since its discovery in 1999 until November 31st 2013,it has had accumulative proven(111b+122b+331+332+333)gold metal amounts of 258.475t at an average grade of 2.61 g/t.This deposit contains 88.98million tons of paragenetic and associated iron ores,with TFe grade varying from 9%to 36%;metal amounts are:gold     

Geology, Geochemistry and Genesis of the Hongshijing Gold Deposit in Ruoqiang,Xinjiang

1IntroductionTheHongshijinggolddepositislocatedinthenorthofLuobupouLakeofRuoqiang ,about 30 0kmsouthwestofHamiCity ,Xinjiang .ItwasdiscoveredbytheSixthGeologicalTeamofXinjiangduringgeo chemicalexploration .TheHongshijinggolddeposit,whichoccursinthegold bearingformationcomposedofMiddleandLateCarboniferousvolcanicandpyroclasticrocks ,isabrittle ductileshearzonetypegolddepositcontrolledbyariftbelt.TheHongshijinggolddepositislocatedinthesouthwestoftheHongshi jing -Maotoushanmineralizationb…     

Water-rock interactions and chemical compositional variations during ductile deformation of the NW-striking shear zone in the Jiapigou gold belt,China

Two kinds of mylonite series rocks, felsic and mafic, have been recognized in the NW-striking shear zone of the Jiapigou gold belt. During ductile deformation, a large amount of fluid interacted intensively with the mylonite series rocks: plagioclases were sericitized and theAn values declined rapidly, finally all of them were transformed to albites; dark minerals were gradually replaced by chlorites (mostly ripidolite). Meanwhile, large-scale and extensive carbonation also took place, and the carbonatization minerals varied from calcite to dolomite and ankerite with the development of deformation. The δ¹³C values of the carbonates are −3.0‰ – −5.6‰ suggesting a deep source of carbon. The ductile deformation is nearly an iso-volume one (f _v≈1). With the enhancement of shear deformation, SiO₂ in the two mylonite series rocks was depleted, while volatile components suchs as CO₂ and H₂O, and some ore-forming elements such as Au and S were obviously enriched. But it is noted that the enrichment of Au in both the mylonite series rocks did not reach the paygrade of gold. The released SiO₂ from water-rock interactions occurred in the form of colloids and absorbed gold in the fluid. When brittle structures were formed locally in the ductile shear zone, the ore-forming fluids migrated to the structures along microfractures, and preciptated auriferous quartz because of reduction of pressure and temperature. Fluid inclusion study shows that the temperature and pressure of the ore-forming fluids are 245–292°C and 95.4–131.7 MPa respectively; the salinity is 12.88–16.33wt% NaCl; the fluid-phase is rich in Ca²⁺, K⁺, Na⁺, Mg²⁺, F⁻ and Cl⁻, while the gaseous phases are rich in CO₂ and CH₄. The δD and δ¹⁸O, values of the ore-forming fluid are −84.48‰ – −91.73‰ and −0.247‰ – +2.715‰ respectively, suggesting that the fluid is composed predominantly of meteoric water. This project is financially supported by the National Natural Science Foundation of China (No. 9488010).     

热液金矿成矿作用地球化学研究综述

文章总结了热液金矿成矿地球化学研究进展,其中包括含金热液来源、控制岩浆热液中金浓度的因素、金在热液中的富集和沉淀机制以及热液金矿成矿地球化学环境.含金岩浆演化早期,磁铁矿、磁黄铁矿和钛铁尖晶石结晶分异会影响岩浆演化形成热液型金矿的能力.与金成矿有关的地热流体中w(Au)为1×10-9～80×10-6,岩浆热液中w(Au...     

Geochemical Styudy of Gold and Arsenic Mineralization of the Carlin-Type Gold Deposits,Qinling Region,China

Element geochemistry of gold arsenic and mineralogical features of their sulfides in the Carlin-type gold depostis of the Qinling region are discussed in this paper.The initial contents of ore-forming elements such as glod and arsenic are high the ore-bearing rock series in the Qinling region.Furthermore,both the metals are concentrated mainly in the diagenetic pyrite.Study on the mineralogy of arsenic-bearing sulfide minerals in the ores demonstrated that there is a poistive correlation between gold and arsenic in the sulfide minerals.Available evidence suggests that gold in the As-bearing sulfide minerals in likely to be presented as a charge species(Au ),and it is most possible for it to replace the exxcess arsenic at the site of iron and war probably deposited together with arsenic as solid in the sulfide minerals. Pyrite is composed of(Aux^3 ,Fe1-2^2 )([AsS]x^3-[S2]1-x^2-),and arenopyrite of (Aux^3 ,Fe1-x^3 )([AsS]x^3-[AsS2]1-x^3-).The occurrence of glod in the As-sulfied minerals from the Carlin-type gold depostis in the Qinling region has been confirmed by electron probe and transmission electron microscopic studies.The results show that gold was probably depostied together with arsenicas coupled solid solutions in sulfide minerals in the early stage of mineralization.Metallogenic chemical reactions concerning gold deposition in the Carlin-type As-rich gold deposits would involve oxidation of glod and concurrent reduction of arsenic.Later,the deposited gold as solid was remobilized and redistributed as exsolutions,as a result of increasing hydrothermal alteration and crystallization,and decreasing resistance to refractoriness of the host minerals.Gold occurs as sub-microscopic grains(ranging from 0.04tp 0.16μm in diameter)of native gold along micro factures in and crystalline grains of the sulfiedes.     

Speciation of gold in hydrosulphide-rich ore-forming fluids: Insights from first-principles molecular dynamics simulations

To shed light on gold speciation in sulfur-containing ore-forming fluids, we perform first principles molecular dynamics (FPMD) simulations to investigate gold-hydrosulphide complexing under representative geological conditions. With this advanced technique, the electronic structures of solutes and solvents are calculated with density functional theory and the thermal motions are sampled with molecular dynamics. The molecular structures, solvated structures and stabilities of possible complexes are characterized in detail and the following insights have been gained. (1) The previously hypothesized species Au(HS)(H₂S)₃ and Au(HS) are found unstable under ore-forming conditions. Au(HS)(H₂S)₃ would dissociate to LAu(HS) (L = H₂S or H₂O) and free H₂S molecules spontaneously. Au(HS) is highly reactive and tends to capture a second ligand to form a double-coordinated complex. (2) In the thin vapor-like phases of low pressures, the stable complexes include Au(HS)(H₂O), Au(HS)(H₂S) and Au(HS)₂⁻ and their relative stability is Au(HS)₂⁻ > Au(HS)(H₂S) > Au(HS)(H₂O). In dense aqueous phases of high pressures, Au(HS)(H₂S) would spontaneously deprotonate to Au(HS)₂⁻ and thus Au(HS)(H₂O) and Au(HS)₂⁻ are the stable forms. All of these complexes can retain to the upper-limit of ore-forming temperatures. (3) The gold ions in the complexes do not favor coordinating more molecules and therefore the solvations happen mainly through H-bonding interactions between the ligands and environmental waters. H-bonds are found in vapor, liquid, and dense supercritical phases, whereas in the thin supercritical phase the hydration is very weak. These results provide quantitative and microscopic basis for understanding the speciation of gold in hydrothermal fluids.     

湖南西部钨锑金矿床成矿规律及找矿应用

湖南西部钨锑金矿床赋存于雪峰弧形构造带之前寒武系浅变质岩系中,受到韧-脆性剪切构造控制,具有明显的地层层位效应。区域变质和动力变形过程中,大规模深层次的韧性剪切变形促使矿源层中的Au活化迁移,连同SiO2,K等活性组分和岩石中的H2O一起形成含金动力变质热液,当其进入伸展型脆韧性剪切带及其剥离构造带、张扭性断裂带时,形成充填交代型含金石英脉型和破碎带蚀变岩型金矿。研究表明,矿床具有特定的元素共生组合,矿脉(体)沿倾向延伸大且普遍具有侧伏成矿现象,沿控矿构造方向侵入的长英质脉岩带与成矿有一定的联系;载金的硫(砷)化物以富集轻硫同位素为特点,氧化-还原反应是金成矿的主要化学机制等特征性成矿标志。矿床广泛发育中低温热液蚀变,黄铁矿、毒砂矿物和As元素是找金的标型矿物和指示元素。矿床成因主要属于受韧-脆性脆剪切带控制的变质热液型金矿。     

Geochemistry of gold deposits in West Hunan and East Guangxi,China

Six kinds of element association in the gold deposits in the studied region are distinguished: (1) tungsten-antimony-gold; (2) tungsten-gold; (3) antimonygold; (4) lead-zinc-silver-gold; (5) uranium-silver-gold; and (6) simple gold. The present paper deals with the distribution, source, mineralization, migration and accumulation of gold. The results show that all ore-controlling strata or source beds related to the gold deposits have high background levels of gold; the gold and other ore-forming elements associated are obviously derived from the country rocks. The mineralization of gold is related chiefly to regional metamorphism or alkali-metasomatism. In response to metamorphism of ore-controlling strata, gold was removed into solutions, and then transported and deposited in some parts of the ore-controlling strata. The main form of gold carried in the solutions was Na[Au(HS)₂]. Native gold or electrum were precipitated from the ore solutions and concentrated into ore deposits with the decrease ofT, pH andfo ₂.     

Thermodynamic study of the association and separation of copper and gold in the Shizishan ore field, Tongling, Anhui Province, China

The Shizishan ore field is the largest gold–copper ore field in the Tongling ore district of Anhui Province, China. Copper and gold deposits in the district are present as one-commodity deposits or as deposits with both commodities. Copper and gold mineralization are either cogenetic or are temporally and spatially distinct. We present the results of systematic geochemical analysis of fluid inclusions from typical Au–Cu deposits in the Shizishan ore field; these data are used to determine the solubility of Cu and Au in the ore-forming fluids and to ascertain the mechanisms and factors that controlled variations in the association and separation of copper and gold mineralization. Our results indicate that copper in the ore-forming fluids was transported as CuCl₂⁻ and CuCl⁰ complexes and that the solubility of copper was controlled by variations in Cl⁻ concentration. In addition, the precipitation of copper was controlled by changes in temperature, pH, fO₂, and fO₂. In comparison, gold in the ore-forming fluids was transported as Au(HS)₂⁻ and Au₂S(HS)₂²⁻ complexes, and the solubility of gold was controlled by variations in total sulfur concentration; the precipitation of gold was controlled by temperature, pH, fO₂, and fO₂. These differences between the two elements meant that copper and gold in the ore-forming fluids responded in different ways to changes in physicochemical conditions. Copper precipitated under relatively acidic conditions at high temperatures, while gold precipitated under weakly alkaline conditions at relatively low temperatures; this dissociation resulted in the temporal and spatial separation and zonation of copper and gold mineralization in the Shizishan ore field.     

Mineralogy and geochemistry of gold-bearing arsenian pyrite from the Shuiyindong Carlin-type gold deposit, Guizhou, China: implications for gold depositional processes

Arsenian pyrite in the Shuiyindong Carlin-type gold deposit in Guizhou, China, is the major host for gold with 300 to 4,000 ppm Au and 0.65 to 14.1 wt.% As. Electron miroprobe data show a negative correlation of As and S in arsenian pyrite, which is consistent with the substitution of As for S in the pyrite structure. The relatively homogeneous distribution of gold in arsenian pyrite and a positive correlation of As and Au, with Au/As ratios below the solubility limit of gold in arsenian pyrite, suggest that invisible gold is likely present as Au¹⁺ in a structurally bound Au complex in arsenian pyrite. Geochemical modeling using the laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of fluid inclusions for the major ore forming stage shows that the dominant Au species were Au(HS)₂⁻ (77%) and AuHS_(aq)⁰ (23%). Gold-hydroxyl and Gold-chloride complexes were negligible. The ore fluid was undersaturated with respect to native Au, with a saturation index of −3.8. The predominant As species was H₃AsO₃⁰ _(aq). Pyrite in the Shuiyindong deposit shows chemical zonation with rims richer in As and Au than cores, reflecting the chemical evolution of the ore-bearing fluids. The early ore fluids had relatively high activities of As and Au, to deposit unzoned and zoned arsenian pyrite that host most gold in the deposit. The ore fluids then became depleted in Au and As and formed As-poor pyrite overgrowth rims on gold-bearing arsenian pyrite. Arsenopyrite overgrowth aggregates on arsenian pyrite indicate a late fluid with relatively high activity of As. The lack of evidence of boiling and the low iron content of fluid inclusions in quartz, suggest that iron in arsenian pyrite was most likely derived from dissolution of ferroan minerals in the host rocks, with sulfidation of the dissolved iron by H₂S-rich ore fluids being the most important mechanism of gold deposition in the Shuiyindong Carlin-type deposit.     

Geochemical studies of the formation of gold deposits in the Shaoxing-Longquan Uplift Zone,Zhejiang Province

This paper systematically deals with the geochemical features of major gold deposits in the Shaoxing-Longquan Uplift Zone, Zhejiang Province, including the content and association of ore-forming elements and trace elements, stable isotopic characteristics, the existing forms of gold, and the composition of ore fluids. The authors consider that the ore-bearing formations in this zone are a good supply of necessary elements and ore fluids for the gold deposits in this area. It is also considered that some Au⁺-Cl⁻ and Au⁺-HS⁻ or Au⁺-CO₂ coordinated ions are the main transport forms of gold in ore fluids and the metallogenesis of gold involves two stages: formation of pyrite and mineralization of Cu, Pb and Zn. In this paper is also presented a comprehensive geochemical model for the formation of gold deposits in this uplift zone.