湘西柳林汊金矿带中钠长石的矿物学和地球化学特征

钠长石广泛分布于湘西柳林汊金矿带的含金脉体中,利用显微镜下鉴定、X荧光光谱(XRF)、X射线衍射(XRD)、电感耦合等离子体质谱(ICP-MS)等分析手段对该区金矿床的钠长石进行了系统的研究.结果表明:该区粉红色、肉红色钠长石镜下呈板条状、粒状,解理不发育,双晶以聚片双晶为主,负低突起,干涉色一级灰白到一级淡黄;钠长石的Ab、An、Or的变化范围分别为97.32%～99.74%、0.12%～2.5%、0.13%～0.47%;该区钠长石的平均有序度都大于0.905,形成温度均在226～395℃之间;钠长石稀土含量普遍较低,在不同程度上都有LREE的富集,无明显的Eu、Ce异常.钠长石矿物学、地球化学特征均反映了该含金钠长石-石英脉是由热液作用形成.     

甘肃阳山金矿区黄铁矿的赋存状态与分布特征

甘肃阳山金矿是迄今为止中国发现的最大金矿。已发现的6个矿段均赋存于泥盆系中,矿石中金属矿物主要为黄铁矿和毒砂。黄铁矿有3种类型:微细粒浸染状、半自形颗粒集合体、自形单晶大颗粒;主要分布在千枚岩、花岗闪长岩、石英脉里,具有多期次多类型的特点。根据黄铁矿的特征,金矿化与石英脉体中细粒浸染状的一期黄铁矿有关。黄铁矿为重要的载金矿物之一,自然金(Au)主要以微细粒的形式赋存于黄铁矿晶体的裂隙内以及晶体与晶体的空隙间。黄铁矿赋存状态和分布特征的研究,对矿区进一步找矿具有指导意义。     

甘肃省阳山金矿田金的赋存状态和金矿物特征

甘肃阳山金矿田属于类卡林型金矿床,金矿化类型主要有蚀变千枚岩、蚀变斜长花岗斑岩、蚀变砂岩、蚀变灰岩四种。金多呈独立金矿物形式出现,少许呈分散状,矿石中金矿物以自然金为主,其次是银金矿。金矿物以包体金、裂隙金、粒间金等形式嵌布于毒砂、黄铁矿、辉锑矿、粘土矿物等主要载金矿物中,且毒砂、黄铁矿、辉锑矿较其它金属硫化物中占优势。金矿物形态各样,粒度以微细粒为主。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、岩浆岩和地幔,成矿作用与印支晚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。     

海南抱板金矿带地质特征及矿床成因

抱板金矿带产于戈枕脆韧性剪切断裂带西侧中元古代花岗岩体内接触带上。有剪切带蚀变岩型、石英脉型和含金伟晶岩型三种主要类型的矿床，以前一类最为重要。经多年研究认为，不同类型矿床的成矿时代不同，具多期成矿的特点。含金伟晶岩型和石英脉型金矿形成于海西期，成矿物质主要来自同期岩浆热液；含金剪切带的糜棱岩型金矿化发生于印支期；剪切带蚀变岩型金矿床形成于燕山期，成矿物质主要来自于与燕山期安玄玢岩同源的深部岩浆，     

吉林夹皮沟金矿带岩脉和蚀变绢云母定年及金矿成矿时代

吉林夹皮沟金矿床的矿化年龄一直存在争议。采用先进的SHRIMP测年方法测得夹皮沟二道沟金矿床的花岗闪长岩脉锆石的2 0 6Pb/ 2 3 8U年龄为 (2 2 3± 2 )Ma ;八家子金矿床的石英正长斑岩锆石的2 0 6Pb/ 2 3 8U年龄为 (2 41± 6 )～ (2 18± 6 )Ma。这一结果与前人测得的K Ar年龄基本相符。这两条岩脉与含金石英脉同构造空间 ,形成时代相近 ,因此上述岩脉年龄大体反映了金矿化年龄。同时还测得八家子金矿床蚀变绢云母的 4 0 Ar 3 9Ar等时线年龄为(2 0 3 975± 0 5 2 7)Ma ,进一步证明金矿化发生在中生代印支期。矿石中含有大量的方铅矿 ,还存在矿物及元素的分带 ,这些特征表明夹皮沟金矿床不太可能是新太古代或元古代形成的变质热液矿床 ,更大可能是中生代与岩浆活动有关的岩浆热液矿床     

浙西开化石龙头金矿含金黄铁矿的成分标型及硫同位素特征研究

浙西开化石龙头金矿位于皖浙赣断褶带中,矿体明显受断裂控制。为了解含金黄铁矿的矿物学特征及其对金矿化作用的指示,对矿床中黄铁矿进行了X射线衍射、电子探针及其硫同位素分析。结果显示,矿石中主要金属矿物为黄铁矿和毒砂,含少量褐铁矿和磁黄铁矿,脉石矿物有石英、绢云母、伊利石和白云石等。黄铁矿的Fe/(S+As)值在0.777～0.886之间,平均为0.828,说明其在中深部环境生成;Co含量(64×10^-6～111×10^-6)及Au/Ag值(3.6～17.8)指示其形成于中低温环境;Co/Ni值为1.95～4.47,平均为3.59,指示其为热液成因;较高的As含量和As-Co-Ni相对含量三角图显示成矿流体与岩浆热液有关,具有地下热卤水的特征;硫同位素值介于6.14‰～8.27‰之间,偏离陨石硫的范围,而与超镁铁质岩的硫同位素值相近,表明成矿流体来自深部,后期受壳源物质影响。     

辽宁生金皋和赵家堡子金矿黄铁矿的找矿标志

在辽宁生金皋地区和赵家堡子地区的找金过程中,采用黄铁矿矿物学方法,对黄铁矿晶体的形态、主要成份和微量元素特征等进行分析。结果表明以五角十二面体晶形为特征的半自形细粒状黄铁矿含金性较高;黄铁矿主成份S、Fe含量相对低,而黄铁矿中Cu、Pb、Zn、Au、Ag等微量元素总量相对高的黄铁矿分布区域与金矿化关系密切;提出赵家堡子地区具备找到一处中型以上金矿的前景,而在生金皋地区找到大型金矿床的可能性很小,但有望找到伴生金矿床。     

LA-ICP-MS trace element analysis of pyrite from the Xiaoqinling gold district, China: Implications for ore genesis

The Xiaoqinling district, the second largest gold producing district in China, is located on the southern margin of the North China Craton. It consists of three ore belts, namely, the northern ore belt, the middle ore belt and the southern ore belt. Pyrite from the Dahu gold deposit in the northern ore belt and Wenyu and Yinxin gold deposits in the southern ore belt were investigated using a combination of ore microscopy and in-situ laser-ablation inductively-coupled plasma-mass spectrometry (LA-ICP-MS). A range of trace elements was analyzed, including Au, Te, Ag, Pb, Bi, Cu, Co, Ni, Zn, Mo, Hg, As and Si. The results show that there are no systematic differences between the trace element compositions of pyrite in the three deposits from different ore belts. In general, Au concentrations in pyrite are low (from < 0.01 ppm to 2.2 ppm) but Ni concentrations are rather high (up to 8425 ppm). A four-stage mineralization process is indicated by microscopic and field observations and this can be related to the systematic trace element differences between distinct generations of pyrite. Stage I precedes the main gold mineralization stage; pyrite of this stage has the lowest Au concentrations. Stages II and III contributed most of the gold to the ore-forming system. The corresponding pyrite yielded the highest concentrations of Au and Ni. Our microscopic observations suggest that pyrite in the main gold mineralization stage precipitated simultaneously with molybdenite that has been previously dated as Indosinian (~ 218 Ma by Re–Os molybdenite dating), indicating the Indosinian as the main gold mineralization stage. The Indosinian mineralization age and the geological and geochemical features of these gold deposits (e.g., low salinity, CO₂-rich ore fluids; spatial association with large-scale compressional structures of the Qinling orogen; δ¹⁸O and δD data suggestive of mixing between metamorphic and meteoric waters; δ³⁴S and Pb-isotopic data that point to a mixed crustal-mantle source) all point to typical orogenic-type gold deposits. High Ni concentrations (up to 8425 ppm) of pyrite possibly linked to deep-seated mafic/ultramafic metamorphic rocks provide further evidence on the orogenic gold deposit affinity, but against the model of a granitic derivation of the mineralizing fluid as previously suggested by some workers. Generally low Au concentration in pyrite is also consistent with those from worldwide orogenic gold deposits. Therefore, the gold mineralization in the Xiaoqinling district is described as orogenic type, and is probably related to Indosinian collision between the North China Craton and the Yangtze Craton.     

REE geochemistry of primitive ore fluids in Ailaoshan gold belt, Southwest China

The REE patterns of primitive ore solutions in the Ailaoshan gold belt are characterized by significant enrichment of LREE, a weak negative anomaly of Eu and a rather strong negative anomaly of Ce. In conjunction with the tension crust in the region, the ore solutions are thought to be originated from a CQ₂-rich fluid as a result of mantle degassing. This research project was financially supported by A-30 project under the State Climbing Program.     

陕西省铧厂沟金矿床主矿带黄铁矿热电性特征及其地质意义

陕西省铧厂沟金矿是一个主要赋存于海底基性火山喷流细碧岩中的金矿床.文中系统研究了该矿床主矿带黄铁矿的热电性特征.主矿带成矿温度主要集中在130～330℃,属中—低温矿床;黄铁矿导电类型从早期到晚期由N型向P型转变;P型黄铁矿出现频率从浅部到深部呈减小趋势;金品位高值区与P型黄铁矿的高值区及热电系数离散度的低值区相对应;主矿带黄铁矿热电导型及热电性参数特征反映出主矿带开采区位于矿体中部偏下,向深处仍有一定规模的延伸.综合分析认为,0至2勘探线深部以及22～26勘探线深部发现新的富矿段的可能性较大.     

河南桐柏老湾金矿带地质特征

老湾金矿带分布于桐柏 - 大别山(北坡)金银成矿带南亚带,北以松扒韧性剪切带与秦岭岩群毗邻,南以鸿仪河韧性剪切带为界和浒湾岩组相接,金矿带受龟山岩组、老湾花岗岩和区域韧性剪切带的共同控制,形成长23 Km、宽0.8~1.3 Km、呈NWW向带状延伸的金矿带.金矿带赋存于中元古代龟山岩组中的下岩性段白云石英片岩中,中上部岩性段斜长角闪片岩脆性构造破碎带中有脉状金矿体产出.老湾花岗岩与其在北侧的金矿体关系密切.     

西藏西部马攸木金矿床成矿流体的特征

马攸木金矿床是西藏最近发现的独立岩金矿床.对马攸木金矿床热液成矿期各矿化阶段石英中的流体包裹体温度与压力、盐度与密度、包裹体成分和H、O同位素诸方面的初步研究表明,成矿流体属中低温(198～259℃)、低盐度(3.10～7.08%NaCl)、低密度(0.85～0.93g/cm3)的流体,属(SO24-)Cl--(K )Na 水化学类型,成矿环境为低压(22.7～26.7 MPa)浅成(0.825～0.971 km)环境.成矿流体可能主要来源于与大气降水有成因联系的地下热水.马攸木金矿床可能是与热泉相关的浅成中低温热液矿床.     

滇西老王寨金矿床黄铁矿形貌特征与化学组成

老王寨金矿床是三江特提斯成矿域中已探明规模最大的造山型金矿床,黄铁矿是其最主要的载金矿物,依据矿(化)脉切割关系、矿石结构构造及矿物共生组合,该矿床成岩-成矿期共发育5个世代黄铁矿。沉积-成岩期草莓状黄铁矿含Pb、Zn、Mn、Co、Ni和Bi。热液金成矿期可划分为:Ⅰ石英-绢云母-黄铁矿、Ⅱ石英-多金属硫化物、Ⅲ方解石-石英-毒砂-黄铁矿和Ⅳ方解石-石英-辉锑矿-黄铁矿四个阶段,其黄铁矿分别以粗粒他形、立方体、五角十二面体和立方体为主,总体继承了沉积-成岩期黄铁矿含Pb、Zn、Mn、Co、Ni和Bi的特征,Au、As、Sb和Cu也有不同程度富集,显示成矿流体成分复杂。Ⅲ阶段为金的主成矿阶段,以发育五角十二面体黄铁矿为特征,富集Au、As、Sb、Pb、Zn、Cu、Co、Ni和Bi,其中,Au与As构成 [Au, As]^2-和[Au(As, S₃)]^2-等络合物以类质同象的形式替代[S²]^2-而进入到黄铁矿中,两者呈正相关,成矿系统处于中-低温、流体过饱和度(硫逸度)高,且缓慢冷却,矿质来源充足的环境。     

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。     

湘西沃溪钨锑金矿床黄铁矿中发现Au-Sb矿物相

利用扫描电镜和电子探针等方法,对沃溪钨锑金矿床中产于(块状白钨矿-石英脉中的)黄铁矿微裂隙中的自然金和Au-Sb矿物相进行了较详细的观察和研究。结果表明,黄铁矿中Au-Sb矿物相除了有前人已经鉴定出的方锑金矿(AuSb2.13)外,还新发现有锑金矿(Au1.02Sb)矿物相。二者以显微颗粒的形式存在于黄铁矿显微裂隙中。黄铁矿微裂隙中Au-Sb矿物相的存在,指示矿床成矿在黄铁矿形成之后存在Au-Sb混溶的成矿流体。自然金、方锑金矿、锑金矿等矿物的沉淀析出可能是Au-Sb混溶流体从高温(高于350℃)向低温(250℃)演变的结果。此外,Au-Sb矿物相的发现对改进矿石冶炼中Au、Sb的分离技术有参考价值。     

湘西地区脉状钨锑金矿床的矿体侧伏与板柱状赋存规律

湘西地区脉状钨锑金矿床矿体严格受构造控制,并普遍具有沿倾向发育较深、侧伏和板柱状赋存的规律。文章阐述了矿体侧伏的控制因素,并以沃溪金矿和泥潭冲金矿为例,分析了褶皱和断裂控制的板柱状矿床(体)的构造特点,总结了矿体板柱状赋存的成因以及矿体侧伏和板柱状赋存的规律,认为应该利用矿体的侧伏和板柱状赋存的规律指导勘查工作。     

甘肃鹿儿坝金矿床金赋存状态研究

甘肃鹿儿坝金矿处在西秦岭“岷礼金矿带”上,是我国卡林型金矿“西北金三角”组成部分。该矿床赋存于洮河复向斜北东翼之中三叠统浅变质浊积岩建造中,矿体受NWW向断裂构造控制明显,矿石以中-低温热液蚀变矿物组合为特征,是一个正在开发但难选的大型金矿床。为了解金的赋存状态,文章通过中-高倍矿相显微镜、金化学物相分析及电子探针(EMPA)测试等手段,研究了金在矿石中的赋存状态。结果表明,三类矿石中金的分布型式基本一致,载金矿物主要为毒砂、石英、黄铁矿和铁白云石;金以矿物包裹金为主,总占比达96.31%,其中硫化物包裹的金占61.45%~89.01%、硅酸盐中的金占有率为7.28%~25.49%,独立存在的金矿物较少,占1.03%~9.01%;独立金矿物主要以矿物粒间单体金形式存在,金成色987.05‰,为自然金,粒度以0.0009 mm×0.0061 mm~0.0078 mm×0.0114 mm为主。这为矿床研究提供了基础信息,并为改善矿山生产提供了一定的理论依据。     

Paragenesis and geochemistry of ore minerals in the epizonal gold deposits of the Yangshan gold belt,West Qinling,China

Six epizonal gold deposits in the 30-km-long Yangshan gold belt, Gansu Province are estimated to contain more than 300 t of gold at an average grade of 4.76 g/t and thus define one of China's largest gold resources. Detailed paragenetic studies have recognized five stages of sulfide mineral precipitation in the deposits of the belt. Syngenetic/diagenetic pyrite (Py₀) has a framboidal or colloform texture and is disseminated in the metasedimentary host rocks. Early hydrothermal pyrite (Py₁) in quartz veins is disseminated in metasedimentary rocks and dikes and also occurs as semi-massive pyrite aggregates or bedding-parallel pyrite bands in phyllite. The main ore stage pyrite (Py₂) commonly overgrows Py₁ and is typically associated with main ore stage arsenopyrite (Apy₂). Late ore stage pyrite (Py₃), arsenopyrite (Apy₃), and stibnite occur in quartz ± calcite veins or are disseminated in country rocks. Post-ore stage pyrite (Py₄) occurs in quartz ± calcite veins that cut all earlier formed mineralization. Electron probe microanalyses and laser ablation-inductively coupled plasma mass spectrometry analyses reveal that different generations of sulfides have characteristic of major and trace element patterns, which can be used as a proxy for the distinct hydrothermal events. Syngenetic/diagenetic pyrite has high concentrations of As, Au, Bi, Co, Cu, Mn, Ni, Pb, Sb, and Zn. The Py₀ also retains a sedimentary Co/Ni ratio, which is distinct from hydrothermal ore-related pyrite. Early hydrothermal Py₁ has high contents of Ag, As, Au, Bi, Cu, Fe, Sb, and V, and it reflects elevated levels of these elements in the earliest mineralizing metamorphic fluids. The main ore stage Py₂ has a very high content of As (median value of 2.96 wt%) and Au (median value of 47.5 ppm) and slightly elevated Cu, but relatively low values for other trace elements. Arsenic in the main ore stage Py₂ occurs in solid solution. Late ore stage Py₃, formed coevally with stibnite, contains relatively high As (median value of 1.44 wt%), Au, Fe, Mn, Mo, Sb, and Zn and low Bi, Co, Ni, and Pb. The main ore stage Apy₂, compared to late ore stage arsenopyrite, is relatively enriched in As, whereas the later Apy₃ has high concentrations of S, Fe, and Sb, which is consistent with element patterns in associated main and late ore stage pyrite generations. Compared with pyrite from other stages, the post-ore stage Py₄ has relatively low concentrations of Fe and S, whereas As remains elevated (2.05～3.20 wt%), which could be interpreted by the substitution of As^? for S in the pyrite structure. These results suggest that syngenetic/diagenetic pyrite is the main metal source for the Yangshan gold deposits where such pyrite was metamorphosed at depth below presently exposed levels. The ore-forming elements were concentrated into the hydrothermal fluids during metamorphic devolatilization, and subsequently, during extensive fluid–rock interaction at shallower levels, these elements were precipitated via widespread sulfidation during the main ore stage.     

湘西南金矿床地球化学特征及其成因

对湘西南金矿床的研究表明,五强溪组为金的主要矿源层,其形成的大地构造 活动大陆边缘;金矿床中Ｐｂ、Ｓ、Ｓｒ的同位素特征反映它们均来自赋矿围岩;成矿流体的和Ｈ、Ｏ同位素特征指示其主要来自大气降水;成矿流体显法出低温,低盐度、呈中性－弱碱性的特征;成矿时代为加里东期,而 传统认识中的武陵,雪峰期;矿床成因为大气降水热液改造成因。