Reworking Intensity—A Key Factor Leading to the Formation of Superlarge Gold Deposits in Greenstone Belts and Metamorphosed Microclastic Rocks in China

The greenstone belt and metamorphosed microclastic rock-type superlarge gold deposits in China are hosted in metamorphic rocks and later intrusive bodies.Sedimentation.regional metamorphism and mineralization contributed a lot to the formation of the deposits,so did remelting magmatic process to some deposits,but the deposits were finally formed by reworking processes.The key factor leading to the formation of superlarge gold deposits is the reworking intensity,which for superlarge gold deposits is reflected by the large-scale reworked source rocks and even ore materials of various sources,strongly oxidized ore-forming fluids with a long and repeated active history and stable geothermal heat current.The factor which decides the reworking intensity is the network consisting of structures of different classes.     

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.     

Geology and Geochemistry of K-feldspar Veins in Lamprophyre at the Zhenyuan Gold Deposit, Yunnan, Southwest China: Implications for Gold Mineralization

Lamprophyres typically appear in hydrothermal gold deposits. The relationship between lamprophyres and gold deposits is investigated widely. Some researchers suggest that the emplacement of lamprophyres triggers gold mineralization, whereas others hypothesize that the formation of lamprophyres increases the fertility of mantle sources and ore-forming fluids. K-feldspar veins, with ages between those of lamprophyres and gold deposits, appear in lamprophyres in Zhenyuan. Therefore, K-feldspar veins are ideal for investigating the relationship between lamprophyres and gold deposits. Phlogopite in K-feldspar veins has lower Mg#, Ni, and Cr contents and higher TiO2, Li, Ba, Sr, Sc, Zr, Nb, and Cs contents than phlogopite in lamprophyres. The in-situ Sr isotopic values of apatites (0.7063–0.7066) in K-feldspar veins are within the range for apatites (0.7064–0.7078) from lamprophyres. High large-ion lithophile element concentrations and low Nb and Ta concentrations in phlogopite from lamprophyres, in addition to high (87Sr/86Sr)i values of apatite (0.7064–0.7078), indicate that the magma parental to these phlogopite and apatite crystals is derived from an enriched mantle. K-feldspar veins are genetically correlated with lamprophyres, whereas sulfide mineral assemblage and trace element compositions of pyrite in K-feldspar veins suggest that K-feldspar veins in lamprophyres are not directly related to gold mineralization of the Zhenyuan deposit.     

Ore—Fluid Systems of Fine Disseminated Gold Deposits Along the Southeastern Margin of the Yangtze Plate

Fine disseminated gold deposits occurring along the southeastern margin of the Yangtze Plate belong to the epithermal type resulting from different systems of ore-forming fluids.According to their sources, the ore-forming fluids can be divided into four systems: a)meteoric water system; b)oil-brine system; c)basin-brine system;and d)magmatic-formation water system.The four hydrothermal systems are responsible for four types of gold deposits, respectively.The meteoric water system produces hot spring gold deposits. The basin-brines,which are derived from fissure water, structural water and absorbed water sealed up in strata, are responsible for the absin-brine-type deposits.The oil-brine system, having the same source as the bain-brines ,is characterized by the involvement of organic matter and is responsible for the oil-brine-type deposits. Inclusion fluid data show that there are obvious differences in chemical composition and carbon, oxygen,hydrogen and sulfur isotopes for these hydrothermal systems.Different metallogenic provinces, in which one of the four systems is dominant, can be recognized in the region.     

Laumontitization as an Exploration Indicator of Epithermal Gold Deposits： A Case Study of the Axi and Other Epithermal Systems in West Tianshan, China

In the light of field investigation, microscopic study, X-ray phase analysis and mineral infrared spectral analysis, it is considered that laumontitization is of extensive occurrence in the Axi gold orefield. The development of laumontitization and its relationship to mineralization show that the laumontitization appeared mainly at the top of and in the periphery of orebodies, and occurred at the edge of the epithermal system or at the late stage of epithermal system evolution. Therefore, laumontitization can be used as an exploration indicator of epithermal gold deposits. The fluids responsible for laumontitization in the Axi gold orefield are similar to those producing hot spring-type gold deposits or those from modem geothermal fields. Epithermal mineralization of the Axi gold deposit was dated at Carboniferous, indicating that the West Tianshan of China is a region favorable to epithermal-type gold mineralization and preservation. Hence the West Tianshan of China is a target area for exploring epithermal gold deposits.     

Element—Assemblage Zoning Features of Gold Deposis in the Cambrian Silicalite Formation,Western Qinling

The gold deposits,occurring in the south subzone of western Qinling,are the only typical and important strata-bound gold deposits,which are associated with submarine exhalative sedimentation.The gold deposits include the La‘erma ore deposit,the Qiongmo ore deposit and the Yaxiang ore occurrence.They are hosted i the Cambrian silicalite formation composed of black chert and slate.The presence of typical chert offers important evidence to evaluate the possible submarine exhalative system and its role in the formation of the gold deposits,which are closely associated with peroclation and diffusion in the horizontal,vertical and axial directions,Element-assemblage zonation is clearly seen due to differences in element concentrations in different directions,Such a zonation makes gold.selenium,uranium,copper,stibium,molybdenum,mercury,etc,precipitate in the form of simple or composite orebodies.The establishent of the element-assemblage zonation is highly helpful for evaluating directly the metallogenesis of gold deposits.     

Yangshan Gold Deposit:The Largest Carlin and Carlin-like Type Gold Deposit in China

Gold Headquarter of the CAPF has discovered the Yangshan super large-scale gold deposit in Gansu Province, which is a great breakthrough of gold exploration and prospecting in Western Qinling Mountains of China. The gold resources of this deposit achieved 308 tons with increasing potentials. Preliminary geological investigations indicate that the Yangshan gold deposit is located in the intra-continental collision orogenic belt; and the deposit was formed during the continent-continent collision orogenic processes. The geological characteristics of the deposit are similar to that of the typical Carlin-type gold deposits, while differences still exist. The ore-forming background is notably different from the Carlin gold deposit province in the United States; and the ore-forming fluids are similar with that of the orogenic-type gold deposit. Accordingly, the Yangshan gold deposit is a transitional type between the Carlin-type and the orogenic type gold deposits. At present, the Yangshan gold deposit is the largest Carlin and Carlin-like type gold deposit that is ever discovered in China. Researches on metallogeny, metallogenic model and ore-enrichment regularities of the Yangshan gold deposit are crucial to meet the pressing needs of the current geological investigation and ore exploration of the deposit.     

Geological-Geochemical Characteristics of Carlin-and Carlin-Like-Type Gold Deposits in south Qinling Mountains

In this paper an intergrated geological and geochemical comparison is made of Carlintype and Carlin-like-type gold depostis in the region of South Qinling with their associated hydrothermal sedimentary lead-zinc pdposits,the Carlin-type deposits in the Yunnan-Guizhou-Guangxi gold triangle,China,the Carlin gold deposits,Carlin,western United States,and the Muruntau-type gold deposits in Uzbekistan.The comparative study indicates that the formation of these deposits has an intimate coupling relation with the mechanism of the tectonic movement of modern plates.Therefore,these deposits belong to those that were formed in the orogenic stage. They have the following similar characteristics:they are all sediment-hosted.occur in a tectonic environment of extensional rifting nature and show the characteristics of syngenetically modified mineralization.On the other hand,they alsso have noticeable differences:they are different in respect to their tectonic settings.association and structure of orogenic belts and complexity and strength of the modified mineralization.The regional tectonic evolution and extensive mineralization in orogenic belts are different expressions of the same continental dynamic process.     

Geology and Geochemistry of Reworking Gold Deposits in Intrusive Rocks of China—Ⅱ Gold Deposits and Their Genesis

Gold deposits in intrusive masses include the veinlet dissemination,quartz vein and veinlet dissemination vein types,They are distributed in fracture zones along the endocontact zone of a batholith or in the centre and edge of a stock.The metallogenic epochs are Yenshanian,Hercynian,Archean,Proterozoic and Himalayan,The gold deposits are characterized by a big difference in time span between gold mineralization and the formation of host masses Ore-forming materials were derived from the masses and auriferous strata and ore-forming fluids came from meteoric and formation waters.When circulating water was heated by ascending heat flow,gold would be extracted,concentrated and transported from auriferous rocks and then precipitated in the masses during the late tectonic movement,Finally gold deposits were formed in the intrusive masses.     

Isotope Geochemistry of Gold Ore Deposits in the Gezhen Shear Zone, Qiongxi, Hainan Island

Gold deposits hosted in the Gezhen shear zone at Qingxi, Hainan Island occur in the Preeambrian metamorphic rock series and are regionally developed in the N-E direction along the tectonic zone. From northeast to southwest are distributed the Tuwaishan-Baoban gold mining district, the Erjia gold mining district and the Bumo gold mining district, making up the most industrially important gold metallogenesis zone on the Hainan Island. Isotope geochemical studies of the typical gold deposits in this metallogenesis zone indicate that their ore-forming materials stemmed largely from the Baoban Group migmatite series, though the involvement of some plutonic materials could not be ruled out. The ore fluids are the mixture of migrnatitized hydrothermal solutions and meteoric waters in addition to the involvement of local magmatic hydrothermal solutions. The superimposition of plutonie materials and magmatic hydrothermal solutions is controlled by the deformation environment of the shear zone and later magrnatic activities. Obvious variations are noticed in isotopic composition in the region studied, probably related to tectonic deformation, metamorphism and other evolutionary characteristics. This study is of great significance in understanding the relationship between the shear zone and gold metallogenesis,the rules of gold metallogenesis and gold ore prognosis.     

煎茶岭与金川超大型镍矿中的伴生金及其比较分析

在对比研究煎茶岭大型镍矿与金川超大型镍矿的矿床地质球化学特征基础上,对两个矿床中的伴生金与镍及超基性岩的成矿关系进行了分析比较,两区不同的构造环境控制了超基性岩的不同分布。两矿床中的Ｎｉ、Ａｕ均来自超基性岩,且Ｎｉ矿床中金均为伴生矿,金川伴生金的丰度与镍成正比,而煎茶岭Ｎｉ矿中僮生金的丰度与镍成反比,其原因可能与各自不同的成矿环境及岩浆活动有关,尽管两镍矿中金的成矿机理基本相似。     

贵州水银洞超大型卡林型金矿同位素地球化学特征

贵州水银洞金矿是黔西南地区一个重要的超大型卡林型金矿,也是国内外少见的一个"高品位、大吨位"卡林型金矿。为了探讨矿床的物质来源问题,在前人研究资料的基础上,对矿床各个中段不同矿体的硫化物、碳酸盐矿物进行了系统采样,进行了S、C、O同位素的测试分析。同时对前人所作的放射性同位素Pb研究成果进行了整理分析。研究表明,水银洞金矿的成矿物质来源具有多源性。结合区域成矿地质背景,认为区域上卡林型金矿的物质来源具有壳幔结合的特点。     

滇-黔-桂微细浸染型金矿床时空分布与成矿流体来源研究

滇-黔-桂微细浸染型金成矿带处于滇-黔-桂裂谷中。金矿床分布与深大断裂存在依附性。金矿带基本展布于深大断裂限定的三角区内,金矿床则分布于深大断裂旁侧或其交叉部位。由幔源岩浆岩(超基性岩及玄武岩)和幔源矿物沿深大断裂分布可推断,深大断裂延伸较深,可达上地幔,属超壳深大断裂。金矿床分布不受地层层位的限制,金矿化具有多层位成矿性。铅、硫、碳、氢、氧同位素地球化学综合对比研究表明,成矿热液中的矿质、矿化剂和水具深源与浅源的混合特征。热液成矿期矿石中石英及萤石的电子自旋共振(ESR)定年结果为68.40±32.41Ma,表明本区金矿床的成矿可能发生在燕山晚期-喜山早期。     

论深源流体参与黔西南金矿床成矿的可能性

通过研究黔西南金矿床时空分布及地球化学特征，讨论了深源流体参与金矿床成矿的可能性。金矿床在时空上受莫面隆起，深大断裂，幔源岩浆岩体的控制，且与航磁异常，重力异常，环形构造等存在对应关系。     

西秦岭地区金矿类型及其成矿作用

西秦岭地区是中国最重要的金矿矿集区之一,除产出少数夕卡岩型金矿床外,几乎所有的其他金矿床都可归并为造山型、卡林型和类卡林型3种类型。研究表明,西秦岭地区中生代花岗岩主要形成于中晚三叠世,而金矿成矿主要集中在晚三叠世,它们都是华北板块与华南板块碰撞导致的秦岭造山作用的产物。西秦岭地区造山型金矿床主要赋存在泥盆系和石炭系一套复杂的构造变形和区域变质的绿片岩相岩中,主要受北西西向脆韧性剪切带控制,成矿元素组合主要为Au-Ag。矿石中含有大量显微自然金、银金矿,明金可见。成矿流体主要为变质流体。由造山作用引起的强烈构造运动为成矿流体提供了运移通道,为矿质沉淀提供了有利的场所。虽然一些造山型金矿床与中酸性岩体相邻,但矿化与岩浆活动不具直接的成因关系。西秦岭地区卡林型金矿床主要产于轻微变质的寒武系至三叠系沉积岩中,明显受地层、岩性和构造控制。金矿床中的金以超显微金和存在于含砷黄铁矿与毒砂晶格中的固溶体金为主。成矿元素组合为Au-As-Hg-Sb-Ba。成矿流体由早期形成的地层水被后期大气降水补给活化形成,也有部分岩浆水或变质水的加入。在伸展背景下大气降水通过循环演化形成了较浅层次的流体系统,导致Au等成矿元素发生沉淀而形成浸染状矿石。西秦岭地区类卡林型金矿床主要产于浅变质沉积岩建造中,受脆韧性剪切带的控制,并形成于花岗岩岩体附近。与造山型、卡林型金矿床最大的不同之处在于,类卡林型金矿床的形成与同时期的岩浆活动有密切的成因关系。矿石中存在显微自然金,载金矿物主要为黄铁矿、含砷黄铁矿和碲化物。成矿热液主要是岩浆水与变质水、建造水的混合流体。与造山型金矿床类似,流体不混溶导致类卡林型金矿床的形成。     

新疆西南天山金矿床主要类型、特征及成矿作用

文章在总结前人研究成果的基础上,综合论述了西南天山金矿的成矿地质背景、金矿床的时空分布和基本特征。根据矿床地质特征和控矿因素,将西南天山的金矿划分为与剪切带有关的金矿床、与侵入岩有关的金矿床(包括斑岩型)、石英-重晶石脉型金矿床、与火山岩有关的金矿床和矽卡岩型金矿床5类,其中与剪切带有关的金矿床是最重要的矿床类型。探讨了西南天山金矿的成矿时代、成矿物质和成矿流体来源,以及成矿地球动力学机制。提出与剪切带有关的金矿床成矿物质主要来源于岩浆和海相碳酸盐岩,成矿流体主要来源于岩浆水或主要来自大气降水,混合少量岩浆水。石英-重晶石脉型金矿床成矿物质来自容矿地层,成矿流体主要来源于沉积建造水。与剪切带有关的金矿、与侵入岩有关的金矿、石英重晶石脉型金矿和矽卡岩型金矿成矿时代主要集中在二叠纪—三叠纪,形成于后碰撞构造演化阶段。斑岩型和浅成低温热液型金矿床形成于岛弧挤压环境。     

胶东地区破碎带蚀变岩型金矿时代的测定及其地质意义

通过对胶东半岛西北部超大型破碎带蚀变岩型金矿 -新城金矿的强烈热液交代成因黄铁绢英岩 Rb- Sr等时线法测年 ,获得 116 .6± 5 .3Ma成矿年龄。结合本区焦家、仓上等大型 -超大型金矿蚀变矿物、石英流体包裹体的 Rb- Sr等时线年龄、K- Ar年龄 (10 5± 7Ma;10 6± 2 Ma;113.5± 0 .6 Ma)等前人成果 ,确定胶东半岛西北部破碎带蚀变岩型金矿成矿时代主要集中在 10 0～ 117Ma。与围岩花岗岩、花岗闪长岩的成岩年龄 (16 0～ 15 0 Ma;130～ 12 6 Ma)存在着近 10 Ma的时差 ,并根据(87Sr/ 86 Sr) i比值以及已有的 C、H、O稳定同位素资料表明 ,即使成矿物质部分来源于围岩花岗岩类 ,但成矿作用与岩浆活动无明显的成因关系 ,而是深部循环的大气降水或幔源 C- H - O流体参与成矿作用的结果     

墨江金矿成矿流体的形成演化机制

笔者利用矿物流体包裹体、稳定同位素、微量元素和稀土元素地球化学等手段，研究了墨江金矿成矿流体的地球化学特征，成矿物质来源和形成演化机制。研究结果表明，墨江金矿为中低温热液金矿床，成矿流体属于中性－弱碱性的钠质溶液，其中的水为大气降和岩浆水混合成因，矿化剂主要来源于深部，金主要来源于海西期超基性岩和志留系金厂组浅变质岩。     

Physicochemical parameters and geochemical features of fluids of precamrbian gold deposits

This paper analyzes literature data on physicochemical parameters and chemical composition of fluids of Precambrian endogenous gold deposits. The average values and ranges of temperature, pressure, and salinity of fluids from the Archean and Proterozoic gold deposits are estimated. It is revealed that fluids of Archean deposits are dominated by methane, while those of Proterozoic deposits, by nitrogen. It is proposed that the accumulation of nitrogen in the atmosphere is related to the intense nitrogen degassing from the Earth’s interior. The highest pressures of endogenous fluids in this period could reflect specifics of deep geodynamics of the planet in the Proterozoic. The large gold deposits (>100 tons) are characterized by narrower range of physicochemical parameters as compared to small deposits. The contribution of heated chloride brines in the formation of majority of large Proterozoic deposits is established.     

胶东金矿床碳酸盐矿物的碳-氧和锶-钕同位素地球化学研究

对胶东四类金矿床(盆地边缘砾岩型、斑岩型-浅成热液型、石英脉型和破碎带蚀变岩型)矿石中的碳酸盐矿物开展了系统的碳-氧同位素和锶-钕同位素地球化学研究。研究结果表明，与宏观的成矿地质条件和矿床地质特征相对应，山东金矿床可能有亲岩浆岩和亲沉积盆地两个不同的成矿系统。前者包括斑岩型-浅成热液型、石英脉型和破碎带蚀变岩型三类金矿床，后者指盆地边缘砾岩型金矿床，二者具有不同的碳-氧和锶-钕同位素地球化学特征。山东亲岩浆岩系列的金矿床，其锶-钕同位素与同时代的幔源岩浆岩一致，碳同位素显示幔源碳和岩浆碳的特征，氧同位素则显示初生水与大气降水不同比例混合的可能性，因此有可能是以CO2为主、富合成矿金属的地幔流体与浅部下渗大气降水相互作用的结果。而与岩浆岩关系不密切、主要受盆地边缘断裂控制的盆地边缘砾岩型金矿床，其碳-氧和锶-钕同位素组成均较分散，可能主要与地壳浅部下渗大气降水对上地壳各种岩石淋滤萃取演化而成的成矿流体有关。