我国变质岩中改造型层控金矿床金的迁移和富集

根据现有的热力学数据计算,AuCl_2~-是预富集阶段金在矿源层中迁移的主要形式,而Au(Hs)_2~-则在热液成矿阶段起主要作用,计算表明,α_(Cl)->10~0的酸性含氯溶液以及α_(ΣS)>10~(-2)的富硫热液可分别作为预富集阶段和热液成矿阶段金的主要地球化学指标。     

四川东北寨微细浸染型金矿床成矿物理化学条件和成矿过程分析

东北寨金矿床是产于碳酸盐岩-碎屑岩建造中的微细浸染型(卡林型)金矿床。矿化严格受控于垮石崖断裂下盘富含有机质和成岩黄铁矿的黑色岩系地层。包裹体研究和热力学计算表明,成矿温度为220—120℃,压力为4.05×10~7—3.04×10~7Pa,形成深度小于2km。成矿流体具弱酸-弱碱性、还原性较强和Cl~-活度较低等特点。矿源层中的金以硫氢络合物Au(HS)_2~-形式活化进入溶液,促使金沉淀富集的机制是溶液中总硫活度的降低、氧逸度的下降和有机质的还原吸附作用等。矿床形成包括四个阶段。     

天然水,土壤和岩石中金与腐殖质的相互作用：地球化学和分析综述

对天然水，土壤和岩石中金与腐殖质相互作用的结果及Ａｕ－腐殖酸和ＡｕＣｌ４ˉ－腐殖酸在体系中相互作用的实验资料进行了研究。研究表明，金与腐殖酸有机质形成配合物的过程，乃是表生带中金的迁移和富集机制的一个重要方面，决定了从碳质矿石中萃取金的工艺特点，影响到岩石，矿石，土壤和天然水中金的测定准确性，进而对金矿质普查和评价的效率有决定性的影响。     

金在土壤中的存在形式及其预测意义

本文介绍了应用已知方法分离土壤(金含量由克拉克值水平到够矿石品位)中各种存在形式的金。查明金以自然金粒、矿物残留物和腐黑物的混入物、金富里酸和金胡敏酸络合物以及AuCl~-、Au(ClOH)~-、Au(OH)_2~-类无机络合物等形式存在于土壤中。对隐伏金矿床来说,金在土壤中的各种存在形式呈带状分布,建议在为预测目的而解释弱地球化学异常时予以利用。     

甘肃省阳山超大型金矿床的有机地球化学特征研究

甘肃省文县阳山金矿是我国地质勘查储量最大的卡林-类卡林型金矿床,赋矿地层为泥盆系一套碳-硅-泥质地层.矿区发育了大量碳质千枚岩,富含有机碳.本文研究了矿石和围岩可溶有机质的生物标志物、有机质的来源和成熟度、干酪根的碳同位素等,论述了阳山金矿床的有机地球化学特征及有机质与成矿的关系,查明了参与成矿的有机质主要是菌藻类等低等生物.生物标志化合物参数和干酪根的H/C-O/C原子比值指示阳山金矿有机质成熟度较高,达到了无烟煤的演化阶段.在热演化的过程中,有机质裂解产生的CH_4和C-2H_6等进入成矿流体中,参与了成矿过程.阳山金矿赋矿地层中含有生物成因的草莓状黄铁矿,显示生物-有机质参与了地层的预富集作用.有机碳含量、有机质的类型和金的丰度之间相关性不明显,说明在阳山金矿的成矿过程中有机质对金的沉淀贡献不大,但是有机质可能参与了金的预富集和运移.     

甘肃省礼县上坝金矿床载金矿物特征及其矿床成因

礼县上坝金矿床是甘肃省近年来在南秦岭微板块发现的矿体规模较大、主要赋矿岩石为硅质岩、氧化带深度大、矿石可浸出性好、金成色高的岩金矿床。通过对上坝金矿床矿石组构、矿物共生组合及载金矿物特征研究发现：金矿物主要为自然金、银金矿、金银矿。载金矿物主要为石英。褐铁矿、粘土矿物和少量碳质矿物也含金。金的赋存形式为粒间金和裂隙金。金矿物的形成富集与硅化一硫化物交代充填作用关系密切,矿床成因为低温热液型金矿床。     

鄂东丰山矿田卡林型金矿地质地球化学特征

鄂东丰山矿田主要由丰山 (封山洞 )铜矿床、鸡笼山金铜矿床和李家湾铜矿床组成。经野外调查和室内研究 ,确认矿田内存在卡林型金矿 ,金平均品位约 5× 1 0 -6,远景储量在大型以上。该卡林型金矿的主要特征是 :(1 )分布于丰山斑岩体周围的中酸性岩脉发育区 ;(2 )容矿岩石为下三叠统大冶组薄层状 -纹层状和角砾状碳酸盐岩 ;(3)矿体主要受高角度断层控制 ,通常产于岩脉的一侧或附近 ;(4 )矿石普遍具白色细网脉状方解石化和碳泥化 ,裂面上常见黑色碳质被膜 ;(5 )金主要为次显微金 ;(6 )成矿物质主要来自矿源层 ,部分来自岩浆 ,成矿热液水主要来自大气降水     

黔西南金矿有机质地球化学研究

黔西南金矿矿石中有机碳含量与金品位之间没有相关关系。有机质为原生沉积形成的各种显微组分和较多成矿期进入的沥青，沥青在各种矿石中普遍出现，成因上具有储层沥青的性质，是石油烃类热演化的产物。沥青热成熟度高，油浸反射率（Ｒ°％）为１．９－４．５，已达晚期甲烷气阶段，估算受热温度为１５０－２４０℃。矿石中干酪根类型以腐泥－腐殖型为主，与石油沥青相比，富集重碳同位素。质子探针分析表明，矿石中沥青的微量元素组成在不同矿区样品中是不同的，同围岩有紧密联系。碳同位素和微量元素结果说明在成矿过程中存在沥青与围岩的物质交换。矿石可溶有机质含量低，由于成矿作用的影响，可能是有机质二次反应的产物，在族组成上同高成熟度碳酸盐岩相似。从烂泥沟金矿矿石有机抽提物芳烃中检出红色素。金矿有机地球化学研究为解释有机质在金矿形成中的作用提供了重要的依据。     

金在热液中的迁移形式

有关现代地热体系及金矿床的流体包裹体的化学组成的系统的研究,结合高温高压下金的溶解度实验表明:形成金矿化的热液具有弱酸—中性—弱碱性(pH=pH_n+1~pH_n—1)的特征,HS~-,Cl~-,HCO_3~-是形成金的配合物的重要配体。在通常的弱酸—中性—弱碱性介质中,金主要以[Au(HS)_2]~-形式迁移,而在高温、强酸性、强氧化介质中金以[AuCl_2]~-,[AuCl_4]~-,Au_2Cl_6(HCl)_2(气态)形式迁移。虽然产生金矿化的溶液仅含ppb级的金,但是在充分长的时间和合适地质环境中也能沉淀成矿。     

安徽铜陵马山金硫矿床稀土元素和稳定同位素地球化学研究

安徽铜陵铜官山铜矿田是中国长江中、下游铁、铜、硫、金成矿带中著名的矽卡岩型矿床。马山金硫矿床位于安徽铜陵铜官山矿田,侵入岩体为天鹅抱蛋山石英闪长岩。文章通过对马山金硫矿床的氢、氧、碳、硫、硅同位素组成和稀土元素地球化学特征研究,探讨成矿溶液中水、碳、硅和硫的来源以及成矿溶液的演化问题。研究表明,稀土元素球粒陨石标准化组成模式为右倾型,矿石的稀土配分曲线类似于天鹅抱蛋山石英闪长岩,认为形成该矿床的热液流体主要来源于闪长质熔体。马山金硫矿床矿石中石英的δ18OH2OV-SMOW变化范围为6.9‰~10.7‰,平均为8.7‰,与岩体的δ18OV-SMOW值(9.3‰~11.1‰,平均为10.0‰)比较接近,而矿石中石英的δDV-SMOW变化范围为-69‰~-62‰,表明矿石成矿流体主要来自岩浆。矿石中方解石的碳、氧同位素组成与矿区围岩的碳、氧同位素组成明显不同,其δ13CV-PDB、δ18OV-SMOW值分别为-5.2‰~-3.6‰和12.2‰~12.9‰,与岩浆作用形成的CO2的碳、氧同位素组成一致,表明矿石中方解石的碳、氧来源于岩浆作用。硅和硫具深部岩浆或岩浆热液水来源的特点。     

Geology,geochemistry and sulphur isotopes of the Hat Han gold–antimony deposit,NE Vietnam

The Song Hien Rift basin is considered as one of the important regions for gold deposits in North East Vietnam. Host rocks of a number gold deposits in the Song Hien Rift basin are mainly in Lower Triassic sedimentary formations. However, there is the Hat Han gold deposit hosted in fined-grained mafic magmatic rocks with similar characteristics as gold deposit hosted in the Triassic sediments. Sulphur isotopic compositions of sulphide are similar to those in carbonaceous shale, suggesting that the sulphur was ‘borrowed’ from sedimentary rocks in filling the rift basin. Gold-bearing sulphides (pyrite and arsenopyrite) are the main form of Au presence in the ore. Gold in pyrite is present as Au^+ 1, and a minor amount of as nanoparticles of native Au (Au⁰); whereas in arsenopyrite, gold is chemically bound as the octahedral complex AuAs₂. Analysis of geology, as well as geochemical and isotopic studies show that the genesis of the Hat Han gold deposit is not related to the Cao Bang mafic magmatism; instead the latter only serves as (ore) host rock. The geochemical results presented above suggest that the gabbro host rock only supplies iron needed for sulphide formation. With regard to ore genesis, the Hat Han gold deposit in the Song Hien rift basin was generated in the similar way as sediment-hosted gold deposit. There are many similar typomorphic features between the Hat Han deposit and Carlin-like deposits in the Nanpanjang sedimentary basin in China.     

Geology and geochemical patterns of the Birimian gold deposits, Ghana, West Africa

A major gold province of the world exists in the Proterozoic Birimian and Tarkwaian supracrustal rocks of West Africa. The bulk of the gold comes from the primary lode occurrences of the Birimian rocks of Ghana (formerly The Gold Coast). Birimian lithofacies is characterised by subaqueous fine-grained sediments with bimodal volcanic material. Metasedimentary rocks include phyllites and metawackes. Metavolcanic rocks are predominantly tholeiitic basalts. Komatiites and banded iron formations (BIF) are absent.Gold is in 5 parallel, evenly spaced, more than 300 km long, northeast-trending volcanic belts separated by basins containing pyroclastic and meta-sedimentary units. The most prominent is the Ashanti volcanic “greenstone” belt, which hosts the Ashanti Goldfields Corporation mines at Obuasi (more than 800,000 kg Au since 1896), the Billiton Bogosu Gold mine at Bogosu, and the State Gold Mining Corporation mines at Prestea, Bibiani and Konongo.Gold, ranging from 2 to 30 ppm, is in quartz veins of laterally extensive major orebodies which deeply penetrate fissures and shear zones at contacts between metasedimentary and metavolcanic rocks. The veins consists mainly of quartz with carbonate minerals, green sericite, carbonaceous partings and metallic sulfides and arsenides of Fe, As, Zn, Au, Cu, Sb, and Pb. Gold occurs in carbonate fillings in fractured quartz veins. Country rocks, which contain rutile, anatase and granular masses of leucoxene, along ore channels, have been hydrothermally altered to carbonates, sericite, silica and sulfide minerals. Fluid inclusion evidences suggest that mineral deposition took place at about 350°C and 140 bar from dilute aqueous solutions. Timing deduced from ore textures, however, show complex multi-stage mineralization events, with higher temperature minerals commonly having formed later than lower temperature ones. Geochemical studies of materials produced by tropical processes, especially soils, are essential in prospecting poorly exposed terranes of west Africa. Trace and major element distributions at mines and mineral occurrences can indicate mineralization otherwise difficult to detect.This paper highlights the features of the Ghanaian gold deposits that may aid the current search for new deposits along the gold belts. Exploration based on geochemistry is highly important, but should be integrated with data from accompanying geological, lithologic, mineralogical, and structural studies.     

秦岭凤太地区金矿床成矿地质条件与时空分布特征

秦岭凤太地区金矿床产于商丹板块对接带和南秦岭边缘海盆区,含金建造为火山碎屑岩和细碎屑(热水)沉积建造,赋矿围岩以绿片岩相细碎屑岩为主。区内的金矿床主成矿年龄为220~170Ma,属晚印支期,主成矿期后叠加燕山期构造热液。空间上金矿带与铅锌矿带呈平行展布,金矿与韧性构造关系密切,显示了构造边界对金矿带的控制,具有继承性特征的脆韧性剪切带为含矿构造,北北东向与近东西向(北西西向)断裂的复合是金矿富集的主要构造特征。     

微细浸染型（卡林型）金矿成矿过程中碳和有机质的作用

在众多关于黔滇桂微细浸染型（卡林型）金矿研究成果的基础上，本文通过本类型金矿含碳及有机质的特征；金能形成金属有机化合物及原子簇化合物的特征的研究。提出金以金属有机化合物形式在本区上二叠统富含生物成因有机质的煤系地层中形成预富集；在区域热变质作用中，金以气相金属有机化合物方式向上运移，蓄积在上二叠统至中三叠统各层位的背斜和穹隆部位；动力变质带的断裂活动引起物理化学突变，使金的气相金属有机化合物在构造断裂带解体、裂化从而形成了含细分散碳质的微细浸染型含金硫化物原生矿化；并探讨了主成矿期后与有机质解体有关的叠加热液活动和表生氧化作用对原生矿化的改造。从而从有机质演化角度初步建立了此类型的成矿模式     

北山地区金矿床金的赋存状态和金矿物特征

甘肃北山地区金矿床主要有岩浆热液型金矿床和与韧性剪切带有关的金矿床,矿化类型为石英脉型和蚀变岩型。金多呈独立金矿物形式出现,少放许呈分散状;金矿物以银金矿为主,次为自然金,平均成色７７２;金矿物以粒间金、裂隙金、连生金、连生金和包体金等形成嵌布于石英、黄铁矿、方铅矿及闪锌矿等主要载物较为发育。金矿物特征反映出本区金矿床的成矿物质主要来源于变质岩,华力西－印支期中酸性岩浆活动是主要的动力源。     

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。     

金窝子金矿金的赋存状态和金矿物特征

金窝子金矿属于岩浆热液型金矿床,金矿化类型有石英脉型和蚀变糜棱岩型.金多呈独立金矿物形式出现,少许呈分散状,以银金矿为主,次为自然金,平均成色782.金矿物以粒间金、裂隙金、连生金和包体金等形式嵌布于黄铁矿、石英、方铅矿及闪锌矿等主要载金矿物中,且黄铁矿、石英较金属硫化物中占优势,黄铜矿中未见金矿物.金矿物形态各样,粒度以中细粒为主.金矿物特征反映出本区金矿床的成矿物质主要来源于变质岩,成矿作用与华力西、燕山期中酸性侵入岩有关.这与地质地球化学研究所获得的矿床成因认识相一致.     

Alteration and mineralization styles of the orogenic disseminated Zhenyuan gold deposit,southeastern Tibet: Contrast with carlin gold deposit

Orogenic disseminated and Carlin gold deposits share much similarity in alteration and mineralization.The disseminated orogenic Zhenyuan Au deposit along the Ailaoshan shear zone,southeastern Tibet,was selected to clarify their difference.The alteration and mineralization from the different lithologies,including meta-quartz sandstone,carbonaceous slate,meta-(ultra)mafic rock,quartz porphyry and lamprophyre were researched.According to the mineral assemblage and replacement relationship in all types of host rocks,two reactions show general control on gold deposition:(1)replacement of earlier magnetite by pyrite and carbonaceous material;(2)alteration of biotite and phlogopite phenocrysts in quartz porphyry and lamprophyre into dolomite/ankerite and sericite.Despite the lamprophyre is volumetrically minor and much less fractured than other host rocks,it contains a large portion of Au reserve,indicating that the chemically active lithology has played a more important role in gold precipitation compared to structure.LA-ICP-MS analysis shows that Au mainly occurs as invisible gold in fine-grained pyrite disseminated in the host rocks,with Au content reaching to 258.95 ppm.The diagenetic core of pyrite in meta-quartz sandstone enriched in Co,Ni,Mo,Ag and Hg is wrapped by hydrothermal pyrite enriched in Cu,As,Sb,Au,Tl,Pb and Bi.Different host rock lithology has much impact on the alteration and mineralization features.Carbonate and sericite in altered lamprophyre show they have higher Mg than those developed in other of host rocks denoting that the carbonate and sericite incorporated Mg from phlogopite phenocrysts in the primary lamprophyre during alteration.The ore fluid activated the diagenetic pyrite in meta-quartz sandstone leading the hydrothermal pyrite enriched in Cu,Mo,Ag,Sb,Te,Hg,Tl,Pb and Bi,but the hydrothermal pyrite in meta-(ultra)mafic rock is enriched in Co and Ni as the meta-(ultra)mafic rock host rock contain high content of Co and Ni.However,Au and As shear similar range in both types of host rocks indicating that these two elements most likely come from the deep source fluid rather than the host rocks.It was shown in the disseminated orogenic gold deposit that similar hydrothermal alteration with mineral assemblage of carbonate(mainly dolomite and ankerite),sericite,pyrite and arsenopyrite develops in all types of host rocks.This is different from the Nevada Carlin type,in which alteration is mainly dissolution and silicification of carbonate host rock.On the other hand,Au mainly occur as invisible gold in both disseminated orogenic and Carlin gold deposits.     

福建尤溪肖板金矿床金的赋存状态及金矿物特征

肖板金矿床属受构造控制的中低温岩浆热液矿床,矿化类型为构造蚀变岩型。金多呈独立金矿物形式出现,少许呈分散状;金矿物以自然金为主,平均成色９３０,有少量银金矿和碲金矿。金矿物以包体金、裂隙金、连生金和粒间金等形式嵌布于黄铁矿、黄铜矿、石英、方铅矿及方解石等主要载金矿物中,且石英、方解石中较金属硫化物中占优势。金矿物形态各异,粒度以中细粒为主。     

黑龙江省太平岭地区下二叠统双桥子组岩石地球化学特征及其成矿意义

太平岭成矿带是黑龙江省重要的铜金多金属成矿带,矿床类型主要为中温热液脉型,也发育斑岩型、浅成低温热液型和岩浆熔离型.区内广泛发育的下二叠统双桥子组（P₁s）由泥质岩、粉砂岩及砂岩夹多层中酸性火山岩等组成.地层中Au、P、Fe等元素含量较高,近年来,在东宁县及穆棱市境内相继发现了陆角岭、五道沟-二十三公里等小型金矿床,金矿体均呈脉状产于P₁s中,但品位较低,直接影响到下一步找矿决策.在野外调查的基础上,利用岩石地球化学、X射线粉晶衍射以及有机碳分析等手段,对该地层岩石类型、沉积物源以及Au等成矿元素来源进行了分析,结果表明:岩石主量元素含量稳定,与PAAS相比,轻度亏损Al₂O₃、P₂O₅、CaO和MnO₂,中度亏损Na₂O、MgO、TiO₂和Fe₂O₃;微量元素除了Zn外,其他元素含量都较低;稀土元素总量与北美页岩相当,轻重稀土元素分异略低于北美页岩;主要矿物为粘土矿物（伊利石、绿泥石）和石英,另有不等量的钠长石、少量的碳酸盐矿物和黄铁矿,岩石TOC含量为0.22%~2.52%,平均值为1.10%;岩石中Au的含量与TOC和粘土矿物含量之间没有相关性.认为区内P₁s为碳质砂板岩,沉积物主要来源于石英质沉积岩的风化产物,少量来源于镁铁质和长英质火成岩,沉积于近岸环境,地层中高含量的金并不是成岩之后由流体携带而来并被岩石中富含的有机物或粘土矿物所吸附,而是同样来源于陆源风化产物,指示该区产于P₁s中的金矿并非层控型金矿床,而是受断层控制的热液脉型金矿床.