Organic Geochemistry of Sedimentary Rock-hosted Disseminated Gold Deposits in Southwestern Guizhou Province, China

Sedimentary rock-hosted disseminated gold (SRHDG) deposits in the Youjiang-Nanpanjiang Basin,southwestem Guizhou Province are commonly hosted by the same fold crests that commonly contain a remarkable amount of organic material. The total organic carbon (TOC) contents of the ores and host rocks are usually less than 1%. The reflectance of vitrinite and pyrobitumen in the ores and the host rocks ranges from 1.5% to 4.5%, often in the range of 2% to 3%. In the Lannigou deposit, the reflectance of vitrinite and pyrobitumen in the ores is usually somewhat higher than those within the host rocks, indicating a hydrothermal impact on the organic matter in the altered host rocks. On the contrary, the estimated maximum paleotemperatures of the Getang and Zimudang deposits are higher than the homogenization temperatures of the fluid inclusions in the ores, signifying that the organic matter maturation predated Au mineralization. No correlation between the organic matter contents and Au concentrations were recognized in the ores.However, the most striking observation is that there is a positive correlation between the $2 (a parameter of Rock-Eval analysis), Au and As contents of the ores in the Lannigou deposit. Organic matter maturation and migration is apparent from the TOC vs. HCI diagram. Furthermore, group analysis of the dichloromethane extractable organic component of the ores and host rocks shows that the maturation degree of the organic matter in the ores is slightly higher than that of the host rocks in the Lannigou gold deposit. However, the compositions of their alkanes, steranes and terpenes, which serve as biomarkers, are quite similar; this suggests that the organic matter found in the ores and host rocks has a common marine source. Organic matter probably contributed to the preconcentration of Au in the host rocks. Hydrocarbons in the system,on the other hand, clearly contributed to the emplacement of the gold mineralization through thermal sulfate reduction.Organic matter in the solution might have increased the potential of the hydrothermal solution to transport Au.     

贵州中三叠统烂泥沟金矿有机质的初步研究

烂泥沟金矿是以浊积岩为容矿岩石的微细浸染型金矿。有机岩石学分析表明,矿石与围岩中干酪根类型无明显差别,同属腐泥-腐植型。与围岩相比,矿石中干酪根成熟度(R₀=2.74%-3.06%)和含金性(6.15-24.8μg/g)均较高;干酪根总含金量在全岩中所占的比例是围岩高于矿石。氯仿沥青“A”的检测说明,矿石样品中可溶性有机质形成于强还原和高盐度环境,沥青质和含硫有机化合物发育。研究认为,干酪根含金性与碳的活化有关;不饱和的有机基因对金的动一定转换可能具有重要意义。     

黔西南卡林型金矿床中固体有机物质的有机岩石学研究

固体有机物质保留了金属矿床成矿过程的重要信息。本文以黔西南烂泥沟和戈塘两个典型金矿床为例,系统研究了其中的固体有机物质的有机岩石学特征,并探讨了固体有机质与金矿化的关系。烂泥沟金矿固体有机质由原生煤系有机质和异源焦沥青组成。煤系有机质为原生有机质,与成岩黄铁矿关系密切,没有直接参与热液成矿作用。焦沥青沿石英脉壁粘附或在细脉和纹层中呈带状分布,是热液成矿期原油热液蚀变的产物,原油搬运Au,遭受热液蚀变并参与热化学还原,导致Au 的释放和沉淀。戈塘金矿床中有机质主要是煤系有机质碎屑,与上覆的含煤层有成因联系。这些有机质在热液过程中遭受热液蚀变,还原硫酸盐,为硫化物的沉淀提供还原硫。     

豫西熊耳山地区槐树坪金矿岩石-土壤找矿指示元素的确定及其应用

槐树坪金矿床位于河南省洛阳市嵩县境内,是豫西熊耳山地区近年来新发现的大型金矿床。本次研究对槐树坪金矿区地表及井下不同类型的较新鲜围岩、蚀变岩和矿石以及地表1∶20000面积性土壤采样,分析29项微量元素,从岩石和土壤两种采样介质来确定槐树坪金矿床的地球化学找矿指示元素。一方面基于较新鲜围岩的元素含量特征确定每个微量元素在该区岩石中的异常下限,进而分别计算了蚀变岩和矿石中微量元素平均含量与异常下限的比值,即异常衬度。按照异常衬度大于1.4的标尺确定了蚀变岩与矿石中明显富集的微量元素组合。另一方面,基于Au与28项微量元素在较新鲜围岩、蚀变岩、矿石三种介质中含量关系散点图直观确定了指示金成矿的微量元素组合。综合二者确定出槐树坪金矿区岩石地球化学找矿的指示元素组合为Au、Ag、As、Sb、Hg、Sn、Mo、Bi、Cu、Pb、Zn、Cd、Nb计13项。针对地表1∶20000面积性土壤调查,采用上述岩石中异常衬度为1.4作为土壤异常下限绘制了槐树坪金矿区微量元素的地球化学异常剖析图,以槐树坪金矿区已探明鸡公山一带的主成矿段为模型确定了土壤地球化学找矿的指示元素组合为Au、Ag、As、Sb、Hg、Bi、Cu、Pb、Zn、Cd、B计11项。综合上述结果认为在找矿指示元素组合方面土壤对岩石具有明显的继承性。基于岩石与土壤介质中共同的10项找矿指示元素,构建了归一化的综合异常指标,以鸡公山矿段为标准对整个槐树坪矿区进行了综合评价,发现槐树坪矿区内马蹄沟、秦佛爷沟、姜疙瘩和天坪西4处具有类似鸡公山矿段的找矿潜力。     

有机质在卡林型金矿成矿过程中的作用

卡林型金矿与有机质之间存在着密切的联系。在表生过程中,有机质对金的溶解、吸附和生物吸收作用是沉积、成岩过程中金在赋矿层位中初步富集的重要地质营力,腐殖酸可能是表生金成矿过程中重要的迁移因素。在热液作用过程中,原油形成和二次运移不可能是金成矿迁移的主要因素,但成烃及成油后期有机质的热成熟和裂解作用所产生的有机酸及Ｈ２Ｓ可能对金的淋滤和迁移起着不可低估的作用。矿体及围岩中有机质的高成熟度,以及矿床及围     

区域生物成矿系统中分子化石来源的复杂性

在由单个热液金属矿床的生物——有机质成矿作用研究向区域生物——有机质成矿系统深入的今天,分子化石的重要性和复杂性日益显得突出。热液金属矿床成矿带往往属于有机质的过成熟区,分子化石的存在首先要考虑成矿后迁入事件的叠加,从中排除某些生物成矿作用假象,如川甘陕金三角区。除了最常见的吸附有机质外,晶包有机质可以是有机质过成熟的金属成矿区分子化石的一种不可忽视的新来源,可提供流体源或矿源的信息,如长江中下游多金属成矿区。赋矿岩与蚀变岩之间的某些分子化石差异则蕴含着与成矿有关的诸如还原作用等化学反应信息,如长江中下游多金属成矿区。     

滇东南底圩金矿床矿物学与地球化学研究

位于右江盆地南部的滇东南底圩金矿床是近年来新发现的一处金矿床,为理清其成因,对不同类型矿石和赋矿围岩进行了主、微量元素及硫化物的硫同位素分析。结果表明,相较于赋矿围岩,矿石中明显富集Au、As、Sb、Hg、Tl、S、K、C元素,应为热液带入;而Si、Mg、Fe、Zr和Th在矿石和围岩中变化不大,Fe主要来源于赋矿围岩。对矿床中的主要金属硫化物黄铁矿和毒砂进行的矿物学和硫同位素分析表明,载金矿物主要为含砷黄铁矿和毒砂,金可能主要以Au+的形式赋存在含砷黄铁矿和毒砂之中;含金硫化物具有较高的硫同位素组成(5.93‰~11.99‰),表明成矿所需的S主要为地壳来源。结合前人对于右江盆地南部相似金矿的研究,认为印支期造山作用使沉积物脱水形成的变质流体交代玄武岩,容矿岩石的硫化物化作用是底圩金矿床形成最重要的成矿作用之一。     

有机质在微细浸染型金矿化中的作用—以黔桂地区为例

黔桂地区微细浸染型金矿主要产于碳酸盐岩—碎屑岩混合沉积层序中,溶矿岩石以泥质岩、粉砂岩和碳酸盐岩为主,富含有机质。矿石中有沥青分布,含金石英中存在有机质裹体。碳质含金量较高,可达53.60×10~(-6),在黄铁矿型矿石中,碳质含量与金的富集具有同步消长的正相关关系,有机质与金矿化关系密切。有机质中对金的迁移和富集起主要作用的是Au(CN)_2~-,Au(CN)_1~-,Au(HS_2)~-等化合物,含金有机络合物在岩石的孔隙或裂隙中运移沉淀。     

Organic Geochemistry Characteristics in Ores and Host Rocks from Qixiashan Lead-Zinc Deposit, Nanjing, China

Organic matter, associated with ores, host rocks, ore source rocks and present in fluid inclusions in the Qixiashan lead-zinc polymetailic deposit hosted in Upper Carboniferous dolomites and limestones in East China, was systematically analyzed using Fourier transform infrared spectroscopy, gas chromatography (GC), GC/mass spectrometry and proton-induced X-ray emission. The biomarker ratios of nC21^--/n22^ -alkanes, C23-tricydic/C30-hopane and the tricyclic terpane parameters induding C21/C23, C19-10/C21-29 and C19-25/C26-29 can effectively discriminate ores from host rocks. Extractable organic matter present in fluid inclusions displays similariUes to those enclosed in the ore source rocks in the biomarker ratios, suggesting that a proportion of orphic matter was introduced into the deposit from the ore source strata. The presence of copper and zinc in stage Ⅱ pyrobitumen indicates that some metals may have been transported by an organic fluid or removed from an aqueous fluid by organic matter.     

Migration paths and precipitation mechanisms of ore-forming fluids at the Shuiyindong Carlin-type gold deposit,Guizhou, China

Shuiyindong is one of the largest and highest grade stratabound Carlin-type gold deposits in China. This paper reports on the results of petrographic studies, electron microprobe analyses (EMPA) of arsenian pyrite, and the mass transfer during mineralization and alteration, and it presents the deposit-scale distributions of Au, As, Sb, Hg, Tl, and trace elements in a representative cross section across the Shuiyindong Carlin-type gold deposit, Guizhou Province. The main objectives were to identify the precipitation mechanisms of minerals, or elements from fluids, and the migration paths of ore-forming fluids.Petrographic and EMPA studies indicate that gold in the primary ores is mainly hosted by arsenian pyrite. Mass transfer associated with alteration and mineralization shows that Au, As, Sb, Hg, Tl, and S were significantly added to all mineralized rocks, Fe₂O₃ and SiO₂ were immobile in the main orebodies that are hosted in bioclastic limestone, and CaO, Na₂O, Sr, and Li were removed from country rocks. The relations between Fe and S indicate that the sedimentary rocks at the Shuiyindong deposit contain more iron than is needed to combine with all of their contained sulfur to form pyrite. This suggests that sulfidation and decarbonation were the principal mechanism of gold precipitation at the Shuiyindong deposit. Hg, Sb, and As commonly formed sulfide minerals, such as stibnite, realgar, and orpiment, in late-stage quartz–calcite veins, or absorbed by organic matter in argillite. Fluid cooling presumably led to depositions of stibnite, realgar, and orpiment in late-stage quartz–calcite veins. Organic matter likely served as a reductant in argillite for the ore fluids, causing the precipitation of As, Sb, Hg, and S, as well as Au.Deposit-scale distributions of gold and other relevant elements reflect the passage of fluids through the rocks. Rock strata and structures allowed the ore-forming fluids to migrate horizontally along the unconformity surface of the Middle–Upper Permian, converge on the high position of an anticline, and then ascend into the overlying strata along the anticlinal axis. The distributions of the major and trace elements show that elements that accompanied the ore-forming fluids include Au, As, Sb, Hg, Tl, and S, and that Na₂O and Li were exhausted in the Longtan Formation at the anticlinal core during gold mineralization. The enrichment of Co, Cr, and Ni in the Longtan Formation at the anticlinal core might be associated with deformation that formed the anticline, or with gold mineralization. Different host rocks were preferentially mineralized by different elements. The bioclastic limestone is commonly enriched in Au, whereas the argillite is preferentially enriched in As, Hg, Sb, and Tl. The zonation of ore-forming elements in the deposit appears to be Sb–Tl–As–Hg–Au–Hg–As (from bottom to top). Enrichment of Au, As, Sb, Hg, and Tl provides useful guidance for the exploration for Carlin-type gold deposits in Guizhou. Anomalies of As and Hg in soil or stream sediment might be an important clue and these elements can be used as indicator elements. Ore-forming fluids migrated along the unconformity surface of the Middle–Upper Permian and the anticlinal axis, so these are favorable sites for exploration for Carlin-type gold deposits in Guizhou.     

陕西二台子金矿地球化学特征及其成因

在前人矿床地质和找矿勘探研究基础上，结合较新工程地质揭露认识以及较新分析测试资料，二台子金矿床显示Au-As-Cu-Sb-Mn-Ba的成矿元素与示踪元素组合；矿石中S同位素组成富集重S，不出现塔式效应，具多种混合S的来源特征；H、O同位素组成显示大气降水的强烈参予；矿化蚀变矿物稀土元素配分模式显示出矿床形成对容矿岩石组分的明显继承；矿床地质地球化学特征与美国卡林金矿床存在许多可类比之处。二台子金矿属于具有沉积－改造成因特征的“秦岭式”卡林型金矿床。     

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.     

新疆富蕴县乔夏哈拉铜(铁)金矿床地质与微量元素地球化学

笔者简单介绍了乔夏哈拉铜(铁)金矿床的基本成矿及其微量元素地球化学特征,指出其主矿体具有“垂向分带”及“铜、金向下同步富集”的特点,认为其容矿火山岩与中基性侵入岩脉具有基本相似的微量元素地球化学行为,铜、金矿石同其容矿火山岩相比具有相对贫K、Rb、Th、Ba,相对富W、Ni、Co、As、Sb、Zn及明显偏低的Th／Ta、La／Yb值。研究稀土元素地球化学,发现铜、金矿石具有明显不同于其容矿火山岩的强Eu富集,后期形成的地质体一般具有相对更为偏低的∑REE值。综合分析表明,该铜(铁)金矿床为一与“层状夕卡岩”有关的火山热液型“层控”矿床。     

丹寨汞金矿床成矿构造地球化学模拟实验

位于贵州省内的丹寨汞金矿床是一典型卡林型金矿床。矿床赋在于上寒武统含有机质的海相泥质碳酸盐岩之中。成矿元素Ａｕ、Ｈｇ、Ａｓ、ｓｂ、Ｂａ密切共生，但汞矿体与金矿体的产出有一定分离。金为微细粒自然金，它与黄铁矿、含砷黄铁矿和粘土矿物有关，在碳质物中，金含量也可提高。有机质（有机碳和沥青）与Ｈｇ－Ａｕ矿化有一定关系。矿床受构造控制明显，矿体主要产出在具压性、压扭性特征的多次构造活动造成的破碎带之中。成矿作用主要是在中低温（１１０－２９０℃）和低压条件下进行的。     

西秦岭金龙山卡林型金矿床地质-地球化学及矿床成因研究

金龙山金矿床位于南秦岭造山带的复理石褶冲带中,赋矿围岩为碎屑岩-碳酸盐建造,矿化明显受地层岩性与韧-脆性构造发育程度的控制。矿床稀土元素地球化学研究表明,地层岩石、矿石和热液矿物的轻重稀土分异程度和特征参数基本一致,表明成矿流体应主要来自于赋矿地层。铅同位素研究表明,地层岩石、矿石和热液矿物均具有较高的放射性成因的铅同位素组成,且均落入南秦岭造山带的泥盆系范围内,暗示铅也主要来自赋矿地层。对前人已有的碳-氧-硫-氢同位素组成和流体包裹体数据综合分析表明,碳和氧应主要来自海相碳酸盐的溶解作用,硫主要来自海相硫酸盐的热化学还原反应;从成矿早阶段到晚阶段,成矿流体的δ18O及δD值向大气降水线＂漂移＂,指示成矿流体以盆地建造水和变质水为主,在晚阶段有大气降水加入。金龙山金矿床与卡林型金矿床的矿床地质-地球化学特征相似,应属于卡林型金矿床,其形成于秦岭造山带陆内造山作用过程中,多层次陆壳叠置加厚的地球动力学背景,是陆内碰撞造山作用的产物。     

云南金顶铅锌矿床中有机质的生物标志化合物特征及其意义

云南金顶铅锌矿床中有机质的生物标志化合物特征研究表明:正构烷烃碳数分布范围较宽,有两种峰型,具弱奇偶优势;萜烷化合物相对丰度五环三萜烷三环萜烷四环萜烷;甾烷以规则甾烷为主,规则甾烷C27-C28-C29呈不对称"V"字型分布;有机质的母质来源以低等水生生源的海藻类为主,伴随有一定量的陆源高等植物组分;有机质沉积于弱氧化-弱还原低盐度环境,其成熟度较高;样品均遭受了一定程度的热解,这可能与成矿热液的热力作用有关,部分样品还遭受了生物降解作用,砂岩型矿石共生有机质的成熟度略高于角砾状矿石赋存的有机质;生物标志化合物多参数对比表明有机质来源于三叠系三合洞组碳酸盐岩地层。     

微细浸染型金矿床矿体与围岩对比研究

桂西北凤山金牙中三叠统微细浸染型金矿床产于浊积岩中，矿床中的有机质含有丰富的流体运移和载Au信息，这种信息可以通过矿体与围岩的对比分析进行揭示，采购与无机地球化学分析所揭示的矿体与围岩有机质丰度，氢指数，C有效，降解率，生物标志物和Au含量等存在着差异，这些差异由含烃成矿流体活动引起，运移烃类的叠加不仅使矿体C有机含量明显增加，而且对Au在矿体部位的富集也有直接的贡献，有机质在桂西北凤山金牙中三叠统浊积岩型金矿床的成矿过程中也起了重要作用。     

‘Indicator’ carbonaceous phyllite/graphitic schist in the Archean Kundarkocha gold deposit,Singhbhum orogenic belt,eastern India: Implications for gold mineralization vis-a-vis organic matter

Carbonaceous rocks in the form of graphitic schist and carbonaceous phyllite are the major host rocks of the gold mineralization in Kundarkocha gold deposit of the Precambrian Singhbhum orogenic belt in eastern India. The detection of organic carbon, essentially in the carbonaceous phyllite and graphitized schist within the Precambrian terrain, is noted from this deposit. A very close relationship exists between gold mineralization and ubiquitous carbonaceous rocks containing organic carbon that seems to play a vital role in the deposition of gold in a Precambrian terrain in India and important metallogenetic implications for such type of deposits elsewhere. However, the role played by organic matter in a Precambrian gold deposit is debatable and the mechanism of precipitation of gold and other metals by organic carbon has been reported elsewhere. Fourier transform infrared spectroscopy (FTIR) results and total organic carbon (TOC) values suggest that at least part of the organic material acted as a possible source for the reduction that played a significant role in the precipitation of gold. Lithological, electron probe analysis (EPMA), fluid inclusions associated with gold mineralization, Total Carbon (TC), TOC and FTIR results suggest that the gold mineralization is spatially and genetically associated with graphitic schist, carbonaceous phyllite/shale that are constituted of immature organic carbon or kerogen. Nano-scale gold inclusions along with free milling gold are associated with sulfide mineral phases present within the carbonaceous host rocks as well as in mineralized quartz-carbonate veins. Deposition of gold could have been facilitated due to the organic redox reactions and the graphitic schist and carbonaceous phyllite zone may be considered as the indicator zone.     

南秦岭山阳—柞水矿集区夏家店金矿床微量-铂族元素地球化学特征及其对矿床成因的指示

夏家店金矿床位于南秦岭造山带内,是一个受构造和地层控制的大型金矿床,矿石类型为角砾岩型、碎裂岩型和石英脉型3种类型,赋矿围岩主要为寒武系水沟口组的炭泥质板岩、炭硅质板岩、硅质岩及白云岩,次为泥盆系西岔河组的角砾岩。本文对夏家店金矿床中矿石（角砾状炭硅质板岩、碎裂硅化白云岩、碎裂炭泥质板岩和石英脉状矿化的硅质岩）和围岩（硅质岩、硅化白云岩和硅质板岩）的微量元素、铂族元素（PGE）质量分数进行测试,进而探讨成矿物质来源以及矿床成因。结果表明：不同类型的矿石与其各自的围岩具有高度的相似性,均富集Sr、Ga、Zr等元素;不同类型的矿石稀土总量均高于各类围岩,但是两者具有相似的稀土配分模式,轻稀土富集,重稀土亏损,均表现出负Eu异常（δEu值为0.51~0.63）;不同类型的矿石PGE总量（7.71×10^-9~38.30×10^-9,平均值23.00×10^-9）均明显大于各类围岩PGE总量（1.28×10^-9~2.44×10^-9,平均值1.86×10^-9）,相比上地壳,不同类型的矿石均明显富集Os、Ir、Pt和Pd,亏损Ru、Rh,而各类围岩均富集Os,亏损Pt、Ru、Rh、Pd,但两者的铂族元素配分曲线具有高度相似性,呈Ru亏损的V型,为地壳的（Os）-Pt-Pd型配分模式。以上特征表明不同类型的矿石和围岩具有明显的微量、稀土元素和PGE地球化学继承性,暗示夏家店下寒武统有可能是重要的矿源层之一。同时,所有矿石和围岩的Au/Ir值（分别为4 821~299 666）和406~8 050）及Pd/Ir值（分别为16.9~588.0和15.2~47.5）变化范围均较大,两者Au/Ir值远高于炭质球粒陨石和原始地幔值、Pd/Ir值远高于岩浆成因矿石值,且夏家店金矿床矿石和围岩的PGE配分曲线与典型热液成因矿床一致。这些特征显示夏家店金矿床具有明显的热液成因,是构造-热液流体成矿作用的产物。     

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.