The gold-telluride connection:Evidence for multiple fluid pulses in the Jinqingding telluride-rich gold deposit of Jiaodong Peninsula,Eastern China

The mechanism of gold migration,enrichment,and precipitation in forming world-class gold deposits has been a topic of wide interest,particularly where these deposits are abundant in tellurides.The Jiaodong Peninsula in eastern China hosts some of the world-class gold deposits among which the Jinqingding deposit is one of the best examples with substantial telluride mineralization and thus provides opportunity to investigate the genetic connection between tellurium and gold mineralization.The orebody in this deposit is hosted in the NE-NNE-trending Jiangjunshi-Quhezhuang fault with the Jurassic Kunyushan granitic pluton as wall rock.The deposit involved three mineralization stages as inferred from assemblages and crosscutting relationships between veins.These stages are:(I)pre-ore gold-poor quartz-pyrite veins,(II)main ore auriferous quartz-pyrite-Te/Bi-minerals±sphalerite±chalcopyrite±barite±marcasite veins,and(III)post-ore quartz-calcite veins.We present here the textural,isotopic,and geochemical variations of different stages/generations of pyrite based on scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS),electron probe microanalysis(EPMA),and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).Pyrite in the Jinqingding deposit displays distinct characteristics.Py1a shows a porous and dissolution-reprecipitation texture in the core,whereas Py1b exhibits a smooth and flat rim.Geochemical analysis reveals contrasting elemental compositions,with Py1a characterized by low Au(avg.0.14 ppm),As(avg.15.57 ppm),Ag(avg.17.71 ppm),and Te(avg.19.22 ppm)contents,but elevated Co(avg.1068.10 ppm)and Ni(224.12 ppm)concentrations,and variable sulfur isotopic composition(δ^(34)SV-CDT=9.54‰-12.12‰).Conversely,Py1b displays increased concentrations of these elements and a more concentratedδ^(34)SV-CDT value(11.99‰-12.23‰),possibly associated with weak coupled dissolution-reprecipitation(CDR)processes.In Stage II,pyrite can be further categorized into two generations:the porous core(Py2a)and the smooth periphery(Py2b).Notably,Stage II exhibits increased contents of Au(Py2a:avg.0.47 ppm;Py2b:avg.5.57 ppm),As(Py2a:avg.1265.20 ppm;Py2b:1049.46 ppm),Ag(Py2a:avg.5.43 ppm;Py2b:avg.65.23),and Te(Py2a:avg.21.47 ppm;Py2b:avg.51.66 ppm),δ^(34)SV-CDT value exhibits minor changes(Py2a:11.48‰-13.05‰;Py2b:11.79‰-12.80‰).These changes potentially indicate the involvement of a fluid pulse characterized by low fO2:−34.9 to−30.2,medium fTe2:−14.7 to−10.9 and fS2:−11.4 to−6.9.Despite the dissolution-reprecipitation textures present in the ores,gold did not undergo remobilization,except for a possible weak contribution in Stage II.The presence of abundant Bi/Te-minerals underscores the significant role of low-melting point chalcophile elements in gold migration and enrichment.By compiling and analyzing sulfur isotopic composition of gold deposits across the entire Jiaodong Peninsula,which shows the reduction of marine sulfates as a crucial mechanism for sulfur enrichment.We conclude that the Jinqingding gold deposit,characterized by abundant tellurium,along with episodic pulses of ore-forming fluids,and exhibit subtle distinctions compared to other gold deposits within the Jiaodong Peninsula.

东坪式金矿的金银碲化物及其载金性

运用反光显微镜、电子显微镜及其能谱、波谱分析技术 ,对东坪式金矿矿石中的Au、Ag碲化物的共生组合、产状和化学成分进行了系统普查 ,发现除自然金外 ,还有碲金矿、碲金银矿和碲银矿等碲化物 ,它们主要与自然金、黄铜矿连生 ,并包裹于石英型金矿石中的黄铁矿、方铅矿和闪锌矿的表面、孔洞或裂隙。这些碲化物形成于硫化物 石英阶段 ( 2 2 0～ 390℃ ) ,为该阶段金矿化的主要特征 ,对形成石英脉型矿体的原生富金矿石及其Au Te元素组合起决定作用。

Au-(Ag)-Te-Se成矿系统与成矿作用

根据金矿床中碲、硒赋存特点与富集程度,可将Au-(Ag)-Te-Se成矿系统的矿床成因类型划分为:(1)浅成低温热液型金-银矿床;(2)造山型金矿床;(3)卡林-类卡林型金矿床;(4)碱性-偏碱性侵入岩型金矿床;(5)斑岩型(铜)金矿床;(6)夕卡岩型(铜)金矿床;(7) VMS型金多金属矿床。碲、硒都是亲地幔的元素,侵入岩与火山岩是Au-(Ag)-Te-Se成矿系统中碲、硒的重要来源,黑色岩系也是硒的重要来源。温度、pH、氧逸度等是控制Te、Se的迁移与富集的重要因素。Au-(Ag)-Te-Se成矿系统的成矿机制与岩浆脱气、流体-熔体分离、水-岩反应、流体沸腾与混合、有机作用密切相关。其中岩浆脱气、流体-熔体分离、流体沸腾与流体混合是碲化物型金矿床的重要成矿机制,而水-岩反应、流体混合、有机作用是硒化物型金矿床的重要成矿机制。在成矿过程中,先期形成一些亚稳定或不稳定的过渡态矿物易发生固溶体分离作用,或是不饱和流体与已形成的矿物发生溶解-再沉淀作用,导致矿石具有丰富的物质组成和结构特点。

分散元素——金矿床中应引起注意的地球化学信息

分散元素Te、Se、Cd、Tl在某些类型金矿中可以富集,是黄金找矿的重要指示元素,甚至是最重要的指示元素。Te、Se主要富集在与碱性岩浆活动有关的金矿中,Cd主要富集在火山热液型金矿和古老结晶基底内的糜棱岩型金矿中,而Tl则在卡林型金矿中富集。分散元素在金矿床中的地球化学信息丰富了黄金找矿方法理论,拓宽了找矿思路。

次氯酸钠-碘化物浸金的实验研究

针对辽宁五龙金矿四道沟分矿的金矿石，研究了影响OCl^- -I^-浸金体系的主要因素。得出了OCl^- -I^-体系浸出的最佳条件是：次氯酸钠的用量占矿浆体积的7％-9％，碘化钾浓度不小于0．25mol／L，pH值为偏酸性至中性，浸出时间为4h，在此条件下金浸出率可达85％以上。

东坪金矿“芥末金”及其类型

对中国河北东坪金 -碲化物型金矿的成分及性质复杂多样的金矿物的研究表明 ,东坪金矿产有由不同尺寸微粒金与碲酸盐 /亚碲酸盐 /含水氧化物组成的一些特殊的混合相 ,具芥末状或胶状结构 ,沿用“芥末金”之称。研究所获众多的分析数据得以对这些成分复杂的物质进行鉴别和分类。并按碲金矿蚀变模式 ,利用孔隙中充填的针铁矿、水硫碲铅石、绿碲铁矿、黄碲矿、黄碲铁石、碲酸等 (或一些未知混合相 )对铁芥末金、碲铅芥末金、碲铁芥末金、锰铅芥末金等各类型的化学组成及性质进行模式化。与前人资料进行了对比 ,对蔡长金、田澍章等描述过的金的碲酸盐或氧化物矿物做出了新的解释 ,提出其中某些未定名的新矿物应解释为芥末金的变种。根据电子能谱学数据推测 ,芥末金中可能存在金的纳米级团簇。

东坪金矿矿石碲、金分布及其相关性

用原子吸收、原子荧光法分别系统测定矿石Au、Te含量表明 ,东坪金矿具有典型的Au -Te元素组合。Te/Au比值平均为 0 .71,且随矿石Au丰度的加富而增加 ,它们的相关系数增大。Au、Te含量对数值的统计分布差异和矿物组合、元素赋存状态的微束分析结果表明 ,Au、Te均以独立矿物为主要赋存状态 ,但Au的矿化表现出多期次特征 ,而Te主要在硅化 -硫化物阶段 ,二者可能具有不同的母源。上述结论对提高金的回收率。

山东平邑归来庄金矿床岩浆演化与成矿物理化学条件

介绍了归来庄金矿床次火山岩的岩浆演化特征，并对隐爆角砾岩带的特征和隐爆机制以及碲金型金矿形成的物理化学条件进行了探讨。研究表明归来庄金矿床是与碱性次火山岩有关。

从沉金后液中回收碲的试验探索

大冶稀贵车间从沉金后液中回收碲,工艺流程长,生产成本高,碲直收率仅有38.68%,公司欲改进此工艺。由于沉金后液中的碲有一部分是正六价形态存在,而正六价碲易溶于热水,不溶于碱液,正四价碲溶于碱液,基于此,本文设计了还原沉碲-碱浸还原渣-碱浸液除杂-中和沉碲工艺路线,并进行了调pH值Na2SO3还原沉碲和直接Na2SO3还原沉碲两类试验,实验结果表明:沉金后液调pH至1.9时,沉碲效果最好,碲浸出率76.9%,产品中TeO2含量64.6%,碲直收率达到54.95%;pH调整过高,会有正六价碲析出,降低碲回收率;pH调整过低,会有单质碲析出,导致碲的碱浸率降低;贵金属Pt、Pd分散损失很少,在碱浸渣中得到很好的富集;低的碱浓度有利于碲的浸出;提高NaOH浓度,碱浸液中的杂质含量显著升高;Na2S、CaCl2能较好的除去碱浸液中重金属杂质。该试验工艺不仅缩短了碲的回收工艺流程,降低生产成本,而且可以提高碲的直收率。