贵州泥堡卡林型金矿热液蚀变矿物学研究及其地质意义

贵州泥堡卡林型金矿床是黔西南碳酸盐岩台地相区新发现的大型矿床,主要赋矿围岩为上二叠统峨眉山玄武岩组含钙质的玄武质沉火山角砾凝灰岩。因此,泥堡金矿一方面具有一般卡林型金矿的低温矿物组合和载金矿物特点,另一方面由于赋矿围岩的特殊性,还出现一些特征性的热液蚀变矿物。泥堡金矿主要载金矿物为环带状含砷黄铁矿和毒砂,其中黄铁矿可以分为6种类型:草莓状黄铁矿(Py0)为沉积成因,环带状黄铁矿核部的暗色麻点状黄铁矿(PyⅠ)为被热液改造的沉积成因,二者均以低w(As)为特点;环带状黄铁矿的内环(PyⅡ)为热液早期形成的黄铁矿,中间环带(PyⅢ)或者外环(PyⅣ)是热液活动高峰时期形成的含砷黄铁矿,具有典型的高As低S、Fe特点,是主要的含金部位。成矿晚阶段形成的黄铁矿(PyⅤ)与辉锑矿、闪锌矿共生。成矿过程中强烈的水岩交代作用下,峨眉山玄武岩组火山岩中的Ti、P、Cu等元素析出,在矿体中形成较多的锐钛矿、磷灰石、黄铜矿、黝铜矿等特征蚀变矿物。激光拉曼测试表明在低温成矿条件下形成的Ti O2矿物是锐钛矿而不是金红石,因此前人获得的金红石年龄能否代表金的成矿年龄值得商榷。相反,磷灰石、绢云母是主成矿阶段形成的新生热液矿物,其原位测年数据可大致代表金的成矿年龄,因此二者是较为合适的测年对象。成矿晚阶段出现重晶石和石膏等硫酸盐矿物,说明成矿环境更为氧化,同时由于同位素分馏,导致了与硫酸盐共生的硫化物如辉锑矿、雌黄和雄黄的δ34S值相比主成矿阶段的黄铁矿和毒砂更低。热液蚀变矿物学是探讨成矿作用过程的重要基础,在卡林型金矿研究中尤为重要。     

黔西南泥堡金矿床金的赋存状态研究

泥堡金矿床是黔西南地区重要的卡林型金矿床,其产出原生矿石和氧化型矿石。前人对各类矿石进行了较多研究,但尚不清晰金在矿石中的赋存状态。通过对泥堡矿区不同类型矿石进行物相分析,结果显示,原生矿石中游离金和碳酸盐中的包裹金含量较低,硫化物中包裹金和硅酸盐中的包裹金占了绝大多数,平均占有率可达42.23%和43.66%,表明金矿化与以黄铁矿、毒砂为代表的硫化物和以石英为代表的硅酸盐有直接关联。氧化矿中金的存在形式主要为游离金,其平均占有率可达79%。黄铁矿的Au-As图解中,不同类型黄铁矿均落在Au溶解线下部,说明硫化物中金存在形式为固溶体金。金在成矿流体中可能以Au(HS)-2的形式存在,金的沉淀机制主要归结为流体不混溶作用和硫化作用导致载金络合物的解耦作用,前者为主要成矿机制。     

黔西南普安泥堡大型金矿床黄铁矿与毒砂标型特征及金的赋存状态

通过系统的显微镜鉴定及扫描电镜观察,将黔西南普安泥堡金矿床中的黄铁矿按形貌特征划分为6种类型,即立方体状、草莓状、细粒状、粗粒状、环带状及长条状黄铁矿。黄铁矿电子探针分析结果表明,主要载金矿物为含砷黄铁矿(环带状黄铁矿、细粒状黄铁矿)和毒砂。环带状黄铁矿核部和环带形成于不同的成岩、成矿阶段,其核部贫Au、As,富Fe、S,属成岩期的产物;环带富Au、As,贫Fe、S,形成于主成矿期。黄铁矿环带中Au与As具有正对应关系,在一定的楔形空间呈正相关,高Au含量往往与中等As含量(2%~6%)相对应;而As与S呈明显负相关,说明富砷环带是As取代S而进入黄铁矿晶格所致。细粒状黄铁矿具有高Au、As,低Fe、S的特点,类似于环带状黄铁矿环带部位的特征,推测富As环带与细粒状黄铁矿同属主成矿阶段的产物。毒砂常穿插或沿含砷黄铁矿边缘分布,表明其形成晚于热液期含砷黄铁矿。因此,泥堡金矿床中载金矿物的结晶顺序大致为:贫砷沉积成因黄铁矿(核部)→富砷黄铁矿环带和细粒状黄铁矿→毒砂。电子探针点分析和面波普扫描显示,Au在载金矿物含砷黄铁矿和毒砂中具有不均匀分布的特征,根据Au的溶解度极限(Au/As 0.02)和lgw(As)—lgw(Au)图解,推测Au主要以"不可见"固溶体(Au~(+1))形式赋存于含砷黄铁矿和毒砂中,极少量可能为纳米级自然金(Au~0)。     

新疆西准噶尔灰绿山金矿地质特征初步研究

灰绿山金矿由热液脉型和浸染状矿石组成。围岩蚀变矿物为石英、黄铁矿、绿泥石和碳酸盐,其中黄铁矿和碳酸盐与成矿作用密切相关。其主要矿石矿物有黄铁矿、毒砂、黄铜矿、闪锌矿、方铅矿和自然金。热液成矿作用划分为石英-钠长石-碳酸盐、粗粒石英、黄铁矿-毒砂、黄铁矿-碳酸盐、石英-方解石5个阶段。不同蚀变围岩具相似稀土分布模式,大离子亲石元素、高场强元素和稀土元素在围岩与成矿流体反应中发生了迁移。     

黔西南架底金矿床载金黄铁矿的矿物学特征及金的赋存规律研究

黔西南地区是中国卡林型金矿的主要产地之一,架底金矿作为黔西南地区近年来在玄武岩中新发现的卡林型金矿床,其金的赋存状态一直备受关注。前人研究表明,含砷黄铁矿是架底金矿的主要载金矿物,然而对架底金矿载金黄铁矿以及金的赋存规律一直缺乏深入的研究。文章结合野外实际调研以及室内显微岩相观察研究,首先对矿区黄铁矿进行了期次的划分;然后利用电子探针微区成分分析方法对不同期次的黄铁矿进行研究,结果显示:架底金矿的黄铁矿中,S、As具有明显的负相关性,Au、As存在一定的相关关系,成矿前黄铁矿与成矿期、成矿后的黄铁矿核部具高S、Fe,低As、Au等相似的特征,成矿期黄铁矿的环带具高As、Au的特征,与成矿后的环带(高As不含Au)相比较具明显差异,两者属于不同的热液事件。据此判断矿区载金黄铁矿的结晶顺序为:草莓状低砷无环带黄铁矿→含砷环带黄铁矿(含金)以及均质无环带的细粒黄铁矿→高砷环带黄铁矿(不含金)。这一结论对架底金矿找矿勘查工作具有一定的指示意义。     

江西金山金矿床黄铁矿与金成矿关系的模拟实验研究

金山金矿床明显受金山—西蒋剪切带控制,金矿体产于剪切糜棱岩带中。金矿石的物质成分比较简单,黄铁矿是主要金属矿物,也是矿石中自然金的主要载金矿物,统计及分析结果表明,矿物中仅占2.51％的黄铁矿中所含的金却占矿石金总量的80.80％,可见分散浸染黄铁矿与金矿化关系密切。为了深入研究黄铁矿与金成矿的关系,作者进行了载金矿物黄铁矿活化、迁移及成分变化的模拟实验。实验结果表明,在构造作用的高温高压条件下,黄铁矿可以产生活化、迁移,其中的成矿元素含量有所升高,而且在多期构造应力作用下,可使成矿元素Cu、Au叠加富集。     

贵州泥堡金矿床热液方解石地球化学特征及地质意义

已有研究表明,右江盆地卡林型金矿成矿期方解石具有独特的中稀土元素富集特点,但其成因还存在诸多争议。贵州泥堡金矿存在成矿期和非成矿期2种热液方解石脉,其中成矿期方解石脉多出现在矿化凝灰质细砾岩与凝灰质（粉）砂岩中,矿物组合为含砷黄铁矿+毒砂+石英+方解石;非成矿期方解石脉在未蚀变灰岩、矿化凝灰质细砾岩与凝灰质（粉）砂岩中均发育,且常穿切成矿期含硫化物方解石脉。文章通过对2种类型方解石脉开展稀土元素与碳、氧同位素、成矿期方解石脉内金属硫化物电子探针与微区原位LA-ICP-MS元素分析,发现与成矿期方解石脉共生的黄铁矿具典型的环带结构,黄铁矿环带和毒砂富Au、As、Sb、Hg、Cu、Co、Ni等元素。成矿期方解石脉显示中稀土元素富集模式和Eu正异常特征,表明金成矿流体为还原性流体,明显不同于非成矿期方解石脉的轻稀土元素富集模式和Eu负异常特征。泥堡金矿成矿期热液方解石的中稀土元素富集模式,与中国西南低温Au-Sb矿床成矿期方解石、萤石、磷灰石等矿物的稀土元素组成特征一致,酸性成矿流体的稀土元素组成可能是导致该金矿区成矿期方解石富集中稀土元素的主要原因。该区热液方解石特有的地球化学特征,使其在低温热液金矿床成矿年代学研究及深部找矿应用方面具有重要前景。     

滇黔桂“金三角”卡林型金矿含砷黄铁矿和毒砂的矿物学研究

滇黔桂"金三角"卡林型金矿不同矿床亚类的典型矿床硫化物显微镜下观察和电子探针显微分析(EP-MA)表明,含砷黄铁矿和毒砂是主要的载金矿物.载金黄铁矿主要以环带状含砷黄铁矿、细粒自形含砷黄铁矿为主.环带状黄铁矿核部贫As、Au,富S、Fe,而环带则相反,且Au与As具有正相关关系.核部贫As的黄铁矿成因复杂,既有成矿早阶段的热液成因,又有受热液蚀变交代的沉积成因.核部和环带是不同成矿阶段的产物.元素的相关关系表明环带中As主要取代S的位置.多环带的特点还表明,热液活动是脉动式的,含矿流体化学成分也是在不断变化的.不论是核部还是环带,均有Au含量高出检出限的测点,但环带是主要的载金部位.细粒含砷黄铁矿为均质结构,具有高As、Au,低S、Fe的特点,类似环带状黄铁矿的环带特征,推测与富砷环带是同期热液活动形成的.毒砂-黄铁矿集合体中的黄铁矿分为环带结构和均质结构2种,并分别具有上述2种黄铁矿的特点.载金毒砂可以细分为3个世代,具均质结构,热液成因.各世代毒砂Au含量均有高出检出限的测点,同时Au、As、S、Fe的含量变化不大,均为主成矿阶段的产物.载金矿物的结晶顺序为:贫砷的沉积成因或早阶段热液成因黄铁矿→富砷的细粒黄铁矿颗粒和富砷黄铁矿环带→毒砂.黄铁矿和毒砂中的Au在EPMA微束的分辨率下均显示分布是不均匀的,环带状黄铁矿中Au元素图出现的均匀结构可能为一种假象,说明金主要以"不可见"的纳米级超显微包裹金形式存在,少量为"不可见"晶格金和微米级显微"可见金".整个滇黔桂"金三角"卡林型金矿不同亚类矿床之间的载金矿物特征和金的赋存状态没有本质区别,说明它们具有相同的成矿作用过程和成矿背景.     

胶西北金城金矿床物质组成及矿床成因研究

研究了金城金矿床蚀变岩石的常量元素和微量元素、蚀变矿物的金含量和化学组成，并首次对铁碳酸盐化及煌斑岩杏仁体的组成进行了研究。结果表明，形成不同类型金矿化的成矿流体组成有差异，但总体以富Fe、Si、K、Au、Ag、Bi、Co、Cu等为特征；黄铁矿为主要载金矿物，石英为金的洁净矿物；铁碳酸盐与黄铁矿、黄铜矿的沉淀关系密切；煌斑岩岩浆晚期残余气液与成矿流体组成相近、沉淀次序相同，表明它们可能有成因联系。     

贵州贞丰水银洞金矿矿床成因与成矿模式:来自载金黄铁矿NanoSIMS多元素Mapping及原位微区硫同位素的证据

贵州贞丰水银洞金矿是中国"滇黔桂"金三角地区最具代表性的超大型卡林型金矿床之一。黄铁矿和毒砂是水银洞金矿的主要载金矿物。背散射电子图像和NanoSIMS高分辨率元素面扫描分析显示载金黄铁矿普遍发育环带结构,不同环带的微量元素种类和含量有显著差别。如增生环带富集Au、Cu、As元素,而核部则相对贫这些元素,富Se。同时,即使在富Au环带中,Au和微量元素也并非均匀分布,环带之中又发育次一级环带。这表明热液来源呈现阶段性和"脉冲式"特征。在元素面扫描分析(Mapping)基础上,本次研究对载金黄铁矿中不同成分特征的核部和环带分别进行了原位硫同位素分析。结果表明:黄铁矿核部的δ34S值变化范围为1.3‰~6.5‰,而富金环带的δ34S值为-3.5‰~7.4‰。与国内外同类矿床的硫同位素特征比较之后发现,这些硫同位素显示岩浆硫特征,暗示载金黄铁矿的硫主要来源于深源岩浆。计算表明,有部分沉积硫混入了成矿流体。最终,我们为水银洞金矿建立了岩浆-热液模式:从深源岩浆分异出的超临界气-液流体携带Au、As等元素沿区域深断裂上升,在区域不整合面和灰家堡背斜轴部破碎带等构造薄弱部位,通过充填、交代围岩的方式沉淀成矿。大气降水的淋滤和渗透在一定程度上有利于金矿化。     

Visible gold in arsenian pyrite at the Shuiyindong Carlin-type gold deposit, Guizhou, China: Implications for the environment and processes of ore formation

Carlin-type gold deposits are best known for the scarcity of visible gold in their ores. It has long been recognized that the majority of gold is “invisible”, such that it cannot be resolved by conventional microscopy, and resides in arsenian pyrite. Shuiyindong differs in that sub-μm to μm-sized native gold is present in arsenian pyrite veinlets and disseminations. It is also the largest (55 tonnes) and highest grade (7 to 18 ppm), stratabound, Carlin-type gold deposit in Guizhou, China and has produced 5 tonnes of gold from sulfide refractory ores extracted by underground mining methods. In this study, an electron microprobe analyzer (EMPA) was used to map the spatial distribution of “invisible” gold and sub-μm to μm-size visible gold particles in arsenian pyrite in high-grade ore samples from the Shuiyindong. The samples studied are hosted in Permian bioclastic ferroan limestone of the Longtan Formation and exhibit evidence of decarbonation, silicification and sulfidation. Arsenian pyrite with detectable Au (> 400 to 3800 ppm) is disseminated in altered limestone and was deposited in two stages separated by an episode of corrosion in a veinlet.The results show that there are two populations of native gold in arsenian pyrite. One is comprised of sub-μm size gold particles (0.1 to 0.2 μm) that are occasionally present in the gold-bearing arsenian pyrite disseminated in the host rocks. This arsenian pyrite is interpreted to have been formed by sulfidation of ferroan calcite and dolomite. Another is comprised of coarser (1 to 6 μm) native gold grains present in the arsenian pyrite veinlet, either on the first stage where it has been corroded or on the second stage. The lack of fluid inclusion or other evidence of boiling and the low iron content of fluid inclusions in quartz, suggest the veinlet formed by sulfidation of another fluid containing Fe. The Fe-bearing fluid may be a depleted ore fluid that gained Fe by dissolution of ferroan limestone after H₂S had been consumed. The association of the largest visible gold grains with an episode of corrosion suggests that fluids episodically became undersaturated with arsenian pyrite while remaining saturated with gold (e.g., pH decrease or an increase in the oxidation state). This may have resulted from incursion of relatively acidic or oxidized fluids that were able to dissolve arsenian pyrite and remain saturated with gold. In this case, sulfidation of iron from the host rock, was the most important depositional mechanism for Au-bearing arsenian pyrite with, or without, grains of native gold.     

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.     

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.     

The Nature of Ore‐forming Fluids of the Carlin‐type Gold Deposit in Southwest China: A Case from the Zimudang Gold Deposit

The Zimudang gold deposit is a large Carlin‐type gold deposit in the Southwest Guizhou Province, China, with an average Au content of 6.2 g/t. Gold is mainly hosted in the fault zone and surrounding strata of the F1 fault and Permian Longtan Formation, and the ore bodies are strictly controlled by both the faults and strata. Detailed mineralogy and geochemistry studies are conducted to help judge the nature of ore‐forming fluids. The results indicate that the Au is generally rich in the sulfides of both ores and wall rocks in the deposit, and the arsenian pyrite and arsenopyrite are the main gold‐bearing sulfides. Four subtypes of arsenian pyrite are found in the deposit, including the euhedral and subhedral pyrite, framboidal pyrite, pyrite aggregates and pyrite veins. The euhedral and subhedral pyrite, which can take up about 80% of total pyrite grains, is the dominant type. Au distributed unevenly in the euhedral and subhedral pyrite, and the content of the Au in the rim is relatively higher than in the core. Au in the pyrite veins and pyrite aggregates is lower than the euhedral and subhedral pyrite. No Au has been detected in the points of framboidal pyrites in this study. An obvious highly enriched As rim exists in the X‐ray images of euhedral pyrites, implying the ore‐forming fluids may be rich in As. The relationship between Au and As reveals that the Au may host as a solid solution (Au⁺) and nanoparticles of native gold (Au⁰) in the sulfides. The high Co/Ni ratio (>1) of sulfides and the enrichment of W in the ores all reflect that the gold‐bearing minerals and ore‐forming process were mainly related to the hydrothermal fluids, but the magmatic and volcanic activities cannot be neglected. The general existence of Au and As in the sulfides of both ores and wall rocks and the REE results suggest that the ore‐forming fluids may mainly be derived from the basin itself. The enrichment of Tl suggests that the ore‐forming fluids may be enriched in Cl. The Ce and Eu show slightly or apparently negative anomalies, which means the ore fluids were probably formed under reducing environment. The Y/Ho ratios of ore samples fluctuate around 28, implying the bicarbonate complexation and fluorine were both involved in the ore‐forming process. Combined with the previous studies and our results, we infer that the ore‐forming fluids enriched Au, As, HS^? and halogen (F, Cl) were derived from the mixture of reducing basinal fluids and magmatic or volcanic hydrothermal fluids.     

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...     

贵州泥堡大型金矿床金的三维富集规律及成矿模式探讨

泥堡金矿床是黔西南近些年发现的大型金矿床之一，前人对金的富集规律及成矿过程开展了大量的研究，但从金的三维富集规律方面探讨金的成矿模式尚未研究。本文利用3Dmine软件对泥堡金矿床的地层、断层和矿体进行三维可视化地质建模。结果显示，矿体呈顺层状和沿断层产状产出，Au主要富集层位为上二叠 统龙潭组二段和一段（P3l2、P3l1），赋存位置为构造蚀变体（Sbt）、F1断层内、F1断层两侧、背斜轴面附近、背斜轴面与断层F1之间，背斜轴面倾向一侧的背斜翼部，且Au含量具有斑块状分布和带状连续分布特点，表现出Au在局部斑块处含量高，并向四周持续递减。据此，本文结合Au的物质来源、流体来源、以及矿床中的地层岩性、断层和背斜组合等特征，获取了矿床形成的流体流向路径，提出了“S型”和“断层+背斜轴面”的成矿模式，这对于泥堡金矿床及类似的矿床开展下一步找矿和成矿预测具有一定的参考意义。     

陕西镇安丘岭卡林型金矿金的赋存状态和富集机理

丘岭金矿床是西秦岭地区重要的卡林型金矿之一, 金矿化赋存于上泥盆统南阳山组和下石炭统袁家沟组地层中, 容矿岩石的岩性为钙质粉砂岩、粉砂质页岩和泥质灰岩.金矿石中主要金属矿物为黄铁矿和毒砂, 非金属矿物则以石英、方解石和绢云母为主.通过对矿石矿物黄铁矿和毒砂的扫描电镜-能谱分析、电子探针分析和激光剥蚀电感耦合等离子体质谱分析, 对丘岭金矿床金的赋存形式和富集机理进行了较为详细的研究.结果表明, 丘岭金矿床中金主要以次显微不可见金的形式存在, 其次为显微可见金.次显微金包括: (1)固溶体金(Au+), 主要存在于环带状细粒黄铁矿的含砷增生边区域和毒砂中, 少量存在于环带状黄铁矿的核部不含砷区域; (2)纳米级自然金颗粒(Au0), 存在于粗晶黄铁矿中.环带状细粒黄铁矿核部的次显微金可能主要以胶体吸附的形式存在, 暗示容矿岩石在沉积成岩过程中有金的初步富集, 而环带状黄铁矿幔部和毒砂中的Au则主要来源于成矿流体, 以S和As的络合物形式搬运.显微可见金主要分布在细粒黄铁矿的晶体边缘和热液蚀变绢云母、石英及方解石中, 粒径通常小于3~5 μm, 其形成可能与成矿流体中金的局部过饱和及成矿流体对细粒黄铁矿和毒砂中次显微金的活化和再次富集有关.      

吉尔吉斯斯坦Taldybulak Levoberezhny(左岸)金矿地质特征及金属矿物学研究

Taldybulak Levoberezhny(又称左岸)矿床位于吉尔吉斯斯坦北天山东段,是区内第三大金矿(金储量130 t,平均品位6.9 g/t)。长期以来,该矿床矿物学研究薄弱,成因类型存在争议,已有观点包括斑岩型、造山型、多阶段叠加成矿等。野外地质调查及室内岩相学鉴定发现：金矿化同时受韧性剪切带和岩体控制,局部显示一定的顺层特征;常见矿石类型包括浸染细脉浸染型、石英电气石硫化物型、块状硫化物型、稀疏浸染型、方解石硫化物脉型等;相关围岩蚀变以硅化、绢云母化、电气石化、碳酸盐化最为强烈,可见绿泥石化、绿帘石化、泥化等。电子探针分析发现,左岸金矿同时发育可见金和不可见金。前者包括银金矿(w(Au)=67.90%~80.86%,w(Ag)=14.24%~30.76%)、含银自然金(w(Au)=88.95%,w(Ag)=8.09%)等,以包体金、裂隙金或粒间金形式赋存于黄铁矿中。后者可赋存于黄铁矿和黄铜矿中(w(Au)=0.16%~0.33%)。不同类型矿石中黄铁矿的形态、结构、成分存在一定差异,显示了叠加成矿的可能性。浸染状细脉浸染型矿石中黄铁矿以中粗粒(30~1 300 μm,多数>200 μm)、半自形自形立方体为主,基本无碎裂或碎裂不明显,可含有自然金、银金矿或硅酸盐包体;成分上具有中等的As(0.03%~1.72%,平均0.66%)、Co(0.06%~0.19%,平均0.13%)、Te(0.03%~0.06%,平均0.04%)含量和As/S、Fe/S、Co/As比值,基本不含Cu、Pb、Zn、Ag。石英电气石硫化物型矿石中黄铁矿多呈中粗粒(30~2 000 μm)、半自形它形粒状,往往发生碎裂,并被黄铜矿、方铅矿等矿物交代;部分颗粒可含有银金矿或硅酸盐包体;总体具有较高的As(0.05%~2.05%,平均0.97%)、Co(0.05%~0.34%,平均0.15%)含量和As/S、Fe/S比值,Co/As比值较低。块状硫化物型矿石中黄铁矿多呈半自形它形粒状产出,但粒度变化较大(250~3 000 μm或者30~300 μm);化学成分上以较高的As(0.05%~2.20%,平均1.21%)、Te(0.04%~0.09%,平均0.06%)含量,高的As/S、Fe/S比值和低的Co/As比值为特征。稀疏浸染型矿石中黄铁矿呈中粒(集中于50~200 μm)、半自形它形粒状产出,内部可含有硫化物、硅酸盐、银金矿、自然金等包体;可发生碎裂并被黄铜矿等沿裂隙充填交代;化学成分变化较大,总体具有较高的Co(0.08%~1.04%,平均0.35%)含量和Co/As比值,几乎不含Te、Cu、Zn。方解石硫化物脉型矿石中黄铁矿呈中粗粒(40~480 μm)、半自形它形粒状产出,内部往往含硅酸盐等包体;黄铁矿以显著低的As(0.04%~0.08%,平均0.06%)、Co含量(0.04%~0.20%,平均0.10%)以及As/S、Fe/S比值为特征,Co/As比值较高,且不含Zn。从上述左岸金矿的控矿构造、矿化类型、围岩蚀变以及不同类型矿石中黄铁矿形态、结构、成分的差异等4方面特征显示,左岸金矿可能存在多期次矿化、叠加成矿。     

贵州泥堡大型金矿床金的三维富集规律及成矿模式探讨

泥堡金矿床是黔西南近些年发现的大型金矿床之一,前人对金的富集规律及成矿过程开展了大量的研究,但从金的三维富集规律方面探讨金的成矿模式尚未研究。本文利用3Dmine软件对泥堡金矿床的地层、断层和矿体进行三维可视化地质建模。结果显示,矿体呈顺层状和沿断层产状产出,Au主要富集层位为上二叠 统龙潭组二段和一段（P3l2、P3l1）,赋存位置为构造蚀变体（Sbt）、F1断层内、F1断层两侧、背斜轴面附近、背斜轴面与断层F1之间,背斜轴面倾向一侧的背斜翼部,且Au含量具有斑块状分布和带状连续分布特点,表现出Au在局部斑块处含量高,并向四周持续递减。据此,本文结合Au的物质来源、流体来源、以及矿床中的地层岩性、断层和背斜组合等特征,获取了矿床形成的流体流向路径,提出了“S型”和“断层+背斜轴面”的成矿模式,这对于泥堡金矿床及类似的矿床开展下一步找矿和成矿预测具有一定的参考意义。     

Fluid Inclusion and Stable Isotope Studies at Don Sixto,a Precious Metal Low Sulfidation Deposit in Mendoza Province,Argentina

The Don Sixto mining area in Mendoza province, central‐western Argentina, contains an epithermal low sulfidation Au–Ag deposit. It is a small deposit (～4 km²), with a gold resource of 36 t. In Don Sixto, ore minerals are disseminated in the hydrothermal quartz veins and hydrothermally altered volcanic‐pyroclastic rock units of Permian–Triassic age. On the basis of the texture, ore mineral paragenesis and cross cutting relationship of gangue minerals, seven stages of mineralization were recognized and described. The first six stages are characterized by quartz veins with minor amounts of base metal minerals and the last stage is represented by fluorite veins with minimal quantities of base metal minerals; the precious metal mineralization is mainly related to the fourth stage. The hydrothermal veins exhibit mainly massive, crustiform and comb infilling textures; the presence of bladed quartz replacement textures and quartz veins with adularia crystals are indicative of boiling processes in the system. Fluid inclusion and complementary stable isotope studies were performed in quartz, fluorite, and pyrite samples from the vein systems. The microthermometric data were obtained from primary, biphasic (liquid‐vapor) fluid inclusion assemblages in quartz and fluorite. The maximum values for salinity and homogenization temperature (T_h) came from the stage IV where quartz with petrographic evidence of boiling has average values of 4.96 wt% NaCl_equiv. and 286.9°C respectively. The lower values are related to the last stage of mineralization, where the fluid inclusions in fluorite have average salinities of 1.05 wt% NaCl_equiv. and average homogenization temperatures of 173.1°C. The oxygen and sulfur isotopic fractionation was analyzed in quartz and pyrite. The calculated isotopic fractionation for oxygen in the hydrothermal fluid is in the range of δ¹⁸O_H2O = ?6.92 up to ?3.08‰, which indicates dominance of a meteoric source for the water, while sulfur reaches δ³⁴S_H2S = 1.09‰, which could be reflecting a possible magmatic, or even a mixed source.