钨在矿物/熔体和溶液/熔体中的分配行为及其对成矿作用的影响

总结了钨(W)在地球不同圈层、不同相以及不同集合体之间的分配行为,并据此来探讨与花岗岩有关的热液型钨矿床的某些成因机制,并将W矿化所需的较高的浓集系数归因于这一系列不均匀分配行为的累积。同时强调了W在溶液/熔体体系,尤其是富F体系中的分配行为是理解其成矿机理的关键。热液中W主要以钨酸(根)和碱性钨酸盐离子存在,后因流经理化条件(温度、盐度、p H值)骤变而沉淀成矿。     

江西大湖塘超大型钨矿初始岩浆流体出溶——来自似伟晶岩壳的记录

江西大湖塘地区是江南造山带中段九岭矿集区内近年查明的世界级超大型钨矿产地,白钨矿体主要呈细脉浸染状缓倾于中粗粒黑云母花岗闪长岩中。位于区内一矿带的成矿母岩顶部发育完好的似伟晶岩壳,壳层的组构特征明显,由母岩向含矿围岩,依次为似斑状黑云母花岗岩→长英质细晶岩→石英长石似伟晶岩→长石石英似伟晶岩→含白钨矿黑云母花岗闪长岩。壳内石英的阴极发光岩相学研究显示,石英巨晶、斑晶、基质和石英脉大多经历了早阶段主晶石英,中阶段扩散交代石英和晚阶段渗滤充填石英3个生长阶段。微量元素研究表明,早阶段石英的生长是一个流体加速沉淀的过程,中阶段和晚阶段流体对主晶石英均有叠加改造,其微量元素呈降低趋势。各类石英均表现为富碱金属元素、中高温（≥483℃）、低Li/Al（0.01~0.50,大多小于0.24）的地球化学特征,反映了成矿流体为岩浆水来源,石英的生长具有岩浆—热液过渡性质。综合研究表明,大湖塘一矿带似伟晶岩壳是初始含矿岩浆流体出溶的产物,其形成过程中动态的物理化学条件促进了成矿元素W由母岩向围岩搬运富集。     

The crystal structure of (Fe<Subscript>4</Subscript>Cr<Subscript>4</Subscript>Ni)<Subscript>9</Subscript>C<Subscript>4</Subscript>

(Fe4Cr4Ni)9C4 is a metal carbide mineral formed by combination of Fe, Cr and Ni with C. It occurs in a chromite deposit in the Luobusha ophiolite, Tibet. Based on the determination of its crystal structure, the empirical formula is (Fe4.12Cr3.84Ni0.96)8.92C3.70 and the simplified formula is (Fe4Cr4Ni)4C9. The mineral is hexagonal with a = 1.38392(2) nm, c = 0.44690(9) nm, pace group P63 m c, Z=6 and the calculated specific gravity Dx = 7.089 g/cm3. Fe, Cr and Ni occupy different crystallographic sites and their coordination numbers are approximately 12, forming an alternate stacking sequence of flat and puckered layers along the c axis. Some metallic atoms have a defect structure. The interatomic distances of Fe, Cr and Ni are 0.2525-0.2666 nm, and the distances between Fe, Cr, Ni and C are 0.1893-0.2169 nm. The coordination number of carbon is 6. It occurs in interstices of the metallic atoms Fe, Cr and Ni to form trigonalprismatically coordinated polyhedra. These coordination polyhedra are linked with each other via shared corners or shared edges into a new type of metal carbide structure.     

赣南漂塘钨矿花岗岩成岩年龄与成矿年龄的精确测定

漂塘钨矿是赣南著名的钨锡多金属矿床,由漂塘本区、木梓园和大龙山三个矿段组成。多年以来,有关漂塘花岗岩成岩年龄,大多是利用邻近的西华山花岗岩的数据进行推断,而已有的年龄测试数据精度很难保证。对该矿床的成矿年龄则报道更少。本文利用单颗粒锆石U-Pb法对漂塘本区和木梓园的成矿花岗岩进行定年,获得了两条很好的U-Pb年龄谐和线,漂塘本区和木梓园成矿花岗岩的年龄分别为161.8±1Ma和 153.3±1. 9Ma。利用矿石中的白云母40Ar/39Ar同位素定年获得了漂塘本区成矿年龄为152±1.9Ma,利用矿石中的辉钼矿Re-Os同位素定年获得木梓园成矿年龄为151.1±8.5Ma。 以上年龄数据表明,矿床的成矿作用或与花岗岩侵位基本同时发生,或稍晚于花岗岩。赣南其他矿集区的一些代表性钨矿如淘锡坑、大吉山等的成矿与成岩也有这两种情况,可见这种成矿方式在赣南地区具有代表性。本文的年龄测定和近年来发表的一些年龄数据表明,赣南钨锡矿床属于华南燕山中期第一阶段陆壳重熔型花岗岩类大规模活动及其伴随的钨锡等金属大规模成矿作用的产物。     

粤东塘唇石英脉型钨(锡)矿床地质特征、成矿时代及其找矿意义

塘唇钨(锡)矿是近年来新发现的一个具有大型规模找矿潜力的石英脉型矿床.矿床产于粤东龙窝花岗闪长岩岩体西部外接触带,赋矿地层为下侏罗统金鸡组碎屑岩,该层位是南岭及邻区石英脉型钨锡矿的最新赋矿地层.在详细的野外地质调查基础上,对矿床含钨石英脉中的白云母进行⁴⁰Ar-³⁹Ar测年,获得白云母⁴⁰Ar-³⁹Ar坪年龄为150±1 Ma,等时线年龄为149±2 Ma(MSWD=1.20),它们在误差范围内一致,为南岭地区燕山早期大规模成岩成矿作用高峰期的产物.塘唇钨(锡)矿的发现,不仅拓宽了石英脉型钨锡矿的找矿视野,还有助于完善石英脉型钨锡矿成矿规律和成矿模式,对区域下一步找矿具有重要指导意义.     

湖南临湘虎形山矿区蚀变地球化学过程研究

湖南省临湘市虎形山钨矿是近年来新发现的大型钨铍矿床。矿区内围岩蚀变类型较多,主要有云英岩化、硅化、绢云母化、碳酸盐化、绿泥石化等。为了探究矿区围岩蚀变与成矿的关系,对蚀变硅质板岩分别作了主微量元素分析,通过元素相关性分析探究了各元素的迁移特征,并探讨了主要蚀变过程中出现的矿化类型以及矿化过程中一些金属矿物的生成顺序;利用标准化Isocon图解法,对围岩蚀变过程中组分的带入带出进行质量平衡计算。研究结果表明,板岩中组分迁移受绢云母化影响强烈,其中云英岩化与成矿关系最为密切,碳酸盐化与钨矿化也有一定联系。通过对湘东北地区、虎形山矿区冷家溪群和上地壳W、Cu、Pb、Zn、As、Sb丰度值的对比,反映了矿区地层富含成矿物质,但并未给成矿提供物质来源。     

雪峰弧形构造带南段牛角界钨矿区花岗岩地球化学特征

湖南牛角界钨矿区花岗岩体位于雪峰弧形构造带南段。岩体主要由细粒黑云母二长花岗岩、中细粒黑云母二长花岗岩、中粗粒黑云母二长花岗岩组成,其中钨矿化与细粒、中细粒花岗岩有关。岩石地球化学特征表明,富碱[ω(Na2O+K2O)=7.58~8.23wt%)],富钾(K2O/Na2O=1.41~1.56),A/CNK=1.45~1.55,属过铝质高钾“S”型花岗岩。稀土元素总量较低(66.29×10^-6~107.78×10^-6),富集轻稀土,LREE/HREE为4.59~8.51,呈右倾型。δEu含量为0.13~0.48,远小于1,显示明显的负异常。在微量元素配分模式中,岩石富集K、W、Ba、Cs、Rb等大离子亲石元素,亏损Th、Nb、Ta、P、Zr、Yb等高场强元素。岩体形成于碰撞造山后环境,并且对牛角界钨矿的形成具有一定的贡献。     

Ore Genesis and Tectonic Significance of the Xiaojiashan Tungsten Deposit,Eastern Tianshan,Xinjiang, China: Evidence from Geology,Fluid Inclusions,and Stable Isotope Geochemistry

The Xiaojiashan tungsten deposit is located about 200 km northwest of Hami City, the Eastern Tianshan orogenic belt, Xinjiang, northwestern China, and is a quartz vein‐type tungsten deposit. Combined fluid inclusion microthermometry, host rock geochemistry, and H–O isotopic compositions are used to constrain the ore genesis and tectonic setting of the Xiaojiashan tungsten deposit. The orebodies occur in granite intrusions adjacent to the metamorphic crystal tuff, which consists of the second lithological section of the first Sub‐Formation of the Dananhu Formation (D₂d ₁²). Biotite granite is the most widely distributed intrusive bodies in the Xiaojiashan tungsten deposit. Altered diorite and metamorphic crystal tuff are the main surrounding rocks. The granite belongs to peraluminous A‐type granite with high potassic calc‐alkaline series, and all rocks show light Rare Earth Element (REE)‐enriched patterns. The trace element characters suggest that crystallization differentiation might even occur in the diagenetic process. The granite belongs to postcollisional extension granite, and the rocks formed in an extensional tectonic environment, which might result from magma activity in such an extensional tectonic environment. Tungsten‐bearing quartz veins are divided into gray quartz vein and white quartz veins. Based on petrography observation, fluid inclusions in both kinds of vein quartz are mainly aqueous inclusions. Microthermometry shows that gray quartz veins have 143–354°C of T_h, and white quartz veins have 154–312°C of T_h. The laser‐Raman test shows that CO₂ is found in fluid inclusions of the tungsten‐bearing quartz veins. Quadrupole mass spectrometry reveals that fluid inclusions contain major vapor‐phase contents of CO₂, H₂O. Meanwhile, fluid inclusions contain major liquid‐phase contents of Cl^?, Na⁺. It can be speculated that the ore‐forming fluid of the Xiaojiashan tungsten deposit is characterized by an H₂O–CO₂, low salinity, and H₂O–CO₂–NaCl system. The range of hydrogen and oxygen isotope compositions indicated that the ore‐forming fluids of the tungsten deposit were mainly magmatic water. The ore‐forming age of the Xiaojiashan deposit should to be ~227 Ma. During the ore‐forming process, the magmatic water had separated from magmatic intrusions, and the ore‐bearing complex was taken to a portion where tungsten‐bearing ores could be mineralized. The magmatic fluid was mixed by meteoric water in the late stage.     

江西东坪石英脉型黑钨矿矿床地质特征、控矿因素及找矿标志

东坪钨矿床是近年在赣北地区新发现的首个超大型石英脉型黑钨矿矿床,位于长江中下游成矿带幕阜山地区东坪-香炉山钨矿找矿远景区东部。矿床赋矿层位为新元古代双桥山群安乐林组浅变质岩系,北东向断裂及其两侧的次级裂隙为区内主要控矿构造、容矿构造,隐伏的燕山晚期黑云母二长花岗岩为成矿岩体,与区内钨多金属成矿关系密切的为石英脉状硅化;两个矿带的钨矿体均产于成矿岩体外接触带,呈现了石英脉型黑钨矿矿床典型的"五层楼"分带特征,矿石工业类型主要为黑钨矿矿石;明确了构造和岩浆岩等主要控矿因素;总结出地表微细裂隙云英岩化-黄铁矿化蚀变带、含硫化物石英细脉带、石英脉、重砂及地球化学异常为区内主要找矿标志。     

ROCKS & MINERALS DETERMINATION AND ANALYSIS

正20141456 Chen Juan(Laboratory of High Temperature and High Pressure Study of the Earth’s Interior,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang550002,China);Tang Hongfeng Progress in Analytical Methods of Tungsten Isotope and Experimental Research on Digestion of Whole