热液矿床中萤石的稀土元素地球化学及其地质意义

萤石是许多热液矿床中重要的脉石矿物,其稀土元素含量及相关参数(如∑REE、LREE/HREE、Eu/Eu*、Ce/Ce*、Y/La、Tb/Ca-Tb/La图解等),能为揭示成矿流体性质、来源与演化,建立成矿模式,评价区域成矿潜力等提供重要信息。然而,随着微区分析技术的日趋成熟,原位实测数据显示,萤石中微量元素(包括稀土元素)的分配在显微尺度上可能具有不均一性,致使依据萤石溶液法获得的稀土元素含量所反映地质信息的可靠性受到质疑。因此,在应用萤石稀土元素地球化学探讨相关地质问题前,有必要加强萤石微观结构的观察和配套的流体包裹体以及相关同位素组成分析。本文在综述萤石稀土元素地球化学研究基础上,初步探讨了影响萤石稀土元素不均一分配的主要机制,以期为萤石稀土元素在热液矿床成因研究中的应用提供借鉴。     

萤石颜色与微量元素关系研究

萤石是一种重要的战略性非金属矿产资源,自然产出的萤石颜色丰富,包括紫色、绿色、蓝色、黄色、无色等。萤石颜色可能与杂质元素、晶体缺陷和有机质有关。本文通过搜集有关萤石微量元素和稀土元素的国内外文献,试图讨论萤石颜色与微量元素和稀土元素之间可能存在的关系。结果表明:(1)不同颜色萤石与微量元素和稀土元素总量之间没有相关性;(2)同一颜色萤石不同深浅色调与微量元素和稀土元素总量之间也没有相关性。萤石颜色主要与Y、Ce、Sm等几个特定的稀土元素有关,且萤石颜色可能主要受稀土元素种类控制,与稀土元素含量无关。紫色萤石相对富集U、Th、Rb、Nb元素,绿色萤石相对富集Ba元素,蓝色萤石相对富集Zr元素。另外,萤石颜色与温度和矿床成因之间不存在明显关系。     

南岭东段北部花岗岩的萤石成矿专属性研究

为了探讨花岗岩的萤石成矿专属性特征,在系统搜集前人成果基础上,对南岭东段北部产萤石花岗岩和非产萤石花岗岩开展了元素地球化学测试和黑云母电子探针分析(EPMA)与对比。结果表明:产萤石花岗岩主要为黑云母花岗岩,属于高钾钙碱性系列,副矿物组合中常见萤石;加里东期、印支期和燕山期的花岗岩均具有形成萤石矿床的可能性,以燕山早期花岗岩的潜力最大。与非产萤石花岗岩相比,产萤石花岗岩具较高的Mo含量和较低的Th/U比值;其黑云母主要为铁质黑云母和铁叶云母,比非产萤石花岗岩的黑云母(主要为铁白云母和铁叶云母)更富TiO2、MgO、Cl、F而贫Al2O3、FeO+Fe2O3;黑云母的F与Cl含量呈正相关,而与Al2O3含量呈负相关;产萤石花岗岩形成于相对高温、低压和高氧逸度的环境,岩浆来源主要为地壳,但有少量幔源,与钨多金属矿床关系较为密切。     

中国萤石矿预测评价模型与资源潜力分析

中国萤石矿资源较丰富,探明资源量居世界前列。我国的萤石矿研究工作主要围绕大中型萤石矿床的地质特征、物质来源、成因、区域成矿规律和少数省级萤石矿成矿远景区划、区域萤石矿资源潜力评价展开。为摸清萤石矿资源家底,制定科学合理的经济产业政策,亟需开展系统的、全国性的萤石矿成矿规律和资源潜力评价。依据中国萤石矿资源潜力评价报告数据和成果,文章分析了中国萤石矿矿床类型、矿床地质特征和时空分布特征,划分了成矿区带;在各省区建立的典型矿床预测模型和区域预测模型基础上,以成矿系列理论为指导,突出总结萤石矿成矿要素和预测要素,归纳、汇总、提出了热液充填型和沉积改造型萤石矿矿床预测评价模型;以各省区圈定的最小预测区、归并的2级预测区和估算的资源量为基础,依据预测要素和区域预测模型,归并、圈定了198个3级预测区,汇总估算了全国萤石矿预测资源量,提出了中国萤石矿预测远景区。中国萤石矿资源丰富,找矿潜力大,预测资源量（CaF2）约9.5亿t,其中单一萤石矿预测资源量约4.3亿t,以热液充填型预测资源量为主。预测远景区主要分布于中国东部,四子王旗、冀北-辽西、豫南、皖南-浙西、浙中、闽北-粤东等地区成矿条件好,资源潜力大,是萤石矿预测资源量较大的地区。     

黔西南萤石矿床流体包裹体地球化学特征

对黔西南州普安、晴隆、贞丰和望谟等地4个代表性萤石矿床的成矿特征及其萤石流体包裹体地球化学特征等进行了系统研究。黔西南地区的萤石矿床主要受二叠系茅口组和玄武岩组之间的"大厂层"控制,少量发育于玄武岩及其上覆、下伏灰岩断裂带中。四个典型萤石矿床中不同类型(颜色)萤石流体包裹体地球化学特征存在较大差异,表现为紫色萤石具有相对较高的均一温度和盐度,均一温度为157～264℃,平均190℃,盐度变化在4.03%～5.26%NaCl equiv.;浅色萤石具有相对较低的均一温度和盐度,均一温度为100～176℃,平均140℃,盐度变化在1.91%～5.86%NaCl equiv.。显微激光拉曼光谱分析显示,不同类型(颜色)萤石流体包裹体中的气相成分相似,主要为H_2、H_2S、CH_4和少量的CO_2及烃类有机物,液相成分主要为H_2O(L)、HCO~(3-)和HS~-。流体包裹体地球化学特征显示,黔西南地区萤石矿床成矿流体具有中低温、低盐度特点,流体体系主体属于NaCl-H_2O体系。结合前人研究资料,本文认为萤石矿床的成矿流体与区域上的Sb矿床甚至Au矿床属于同一成矿流体,只是萤石矿床属于这一流体晚期成矿的产物,即晚期流体通过混合作用和水-岩相互作用等过程在"大厂层"形成似层状、透镜状萤石矿体,在玄武岩和灰岩断裂带中形成脉状萤石矿体。     

江西省万安县林山背萤石矿地质特征及成因探讨

林山背矿区萤石矿为中—低温热液充填型矿床,矿石类型主要为萤石型和萤石—石英型。通过对区域地质背景、矿区地质特征和矿体特征进行研究,笔者发现矿区内矿体发育于燕山早期侵入的黑云母花岗岩体内硅化破碎带中,矿体形态严格受区域性断裂构造F2控制。受后期断裂构造F3切割,分割成V1与V2两个萤石矿体。笔者提出林山背矿区萤石成矿物质来源于岩浆热液,早期形成的萤石在构造应力作用下发生破碎,显示出多期次成矿的特点。对萤石矿体的成因分析以及硅化、绢云母化等找矿标志,为进一步萤石矿的勘查开发提供了理论依据和找矿指导。     

相山铀矿稀土元素地球化学特征

<正>萤石是一种存在于较为广泛的地质环境中的含钙矿物,由于稀土元素的离子半径和Ca2+相近,Ca2+常被Y和Ce等稀土元素替代。因此通过对萤石中稀土元素的分析可以了解关于萤石矿化作用过程中地质流体等方面的重要信息。相山铀矿矿石的脉石矿物组成比较简单,主要有萤石、方解石等。本文通过对相山铀矿的萤石的稀土元素研究,进而进一步探究相山铀矿田的成     

拉拉IOCG矿床萤石的微量元素地球化学特征及其指示意义

康滇地区元古宙拉拉IOCG矿床中有与铜、钼矿化密切相关的萤石产出,其中,变质期有萤石(I)和萤石(II)2个世代萤石产出,前者与鳞片状辉钼矿共生,后者与条带状辉钼矿共生;热液期萤石(III)呈脉状穿插含变质期萤石的矿石;萤石的微量元素记录了成矿流体来源方面的重要信息。通过ICP-MS方法分析矿床中2期萤石样品的微量元素组成,运用微量元素含量、比值及蛛网图探讨微量元素特征、成矿流体来源及性质。结果表明:变质期萤石中各微量元素含量有一定的变化范围,热液期中各微量元素含量比较稳定,元素在萤石中的含量主要由元素在原始流体中的含量及元素本身性质所决定。结论认为:1变质期萤石(I)和萤石(II)为同源流体不同阶段演化产物,成矿流体来自于围岩,为具有高F-,Cu,Mo和Y含量的低p H值海水相流体,活动范围有限,没有发生大规模流动或迁移;2热液期萤石(III)与变质期萤石不同源,成矿流体由大气降水或地下水渗透淋滤围岩形成,为具有低F-含量的高p H值大陆淡水相流体,可能发生较远距离的渗入性流体流动或迁移。     

四川某稀土矿尾矿中回收萤石的试验研究

四川某稀土尾矿中CaF2品位为24.67%,属于中低品位伴生萤石矿资源,具有一定的经济回收价值。根据该尾矿中主要脉石矿物组成及嵌布特性,经选矿试验研究,获取最佳萤石回收工艺流程。结果表明,在一段磨矿细度-0.074mm占60.16%条件下,采用调整剂碳酸钠、抑制剂酸化水玻璃、捕收剂OZ,经“1次粗选、2次粗精选、1次扫选”的试验流程得到萤石粗精矿;萤石粗精矿在二段磨矿细度-0.074 mm占79.26%条件下,采用抑制剂WS,捕收剂油酸,经“1次精粗选、7次精选、2次扫选”的闭路试验流程,最终获得含CaF2含量97.43%、回收率50.72%的萤石精矿1,CaF2含量93.25%、回收率25.97%的萤石精矿2,萤石总回收率76.69%,实现了对该稀土矿尾矿中萤石的回收。     

辐射损伤与萤石颜色的初步研究

由于萤石(CaF_2)的钙离子半径(1.06)与钍离子半径(1.10)、特别是与四价铀离子半径(1.05)相似,所以铀和钍常常置换萤石中的钙而进入萤石晶格。此外,铀和钍还能以吸附形式赋存在萤石裂隙中或其表面上,或者成为独立的矿物以固体包体形式存在于萤石中。因此,萤石常含有铀和钍,加之周围岩石中也经常含有放射性元素,从而形成了放射场。萤     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861