巴音塔拉凹陷呼和砂岩型铀矿床微量元素地球化学特征

巴音塔拉凹陷呼和砂岩型铀矿床矿体主要赋存于下白垩统赛汉组(K1bs)下段辫状河相砂体中。对该矿床的铀矿石、矿化岩石和围岩样品进行微量元素和稀土元素地球化学分析表明:铀矿石、矿化岩石和围岩中明显富集Mo、Cd、W和U,相对亏损V、Cr、Co、Ni等相容元素,Sr元素强烈亏损;U与其他微量元素相关性较差。铀矿石、矿化岩石和围岩表现出相似的稀土元素地球化学特征和配分模式。不同岩性的铀矿石表现出相近但有差异的微量元素地球化学特征。笔者认为,呼和铀矿床经历了沉积成岩和后期热液改造与沿断裂上升的含H2S油气的(二次)还原叠加两个阶段的成矿作用。     

REE地球化学在砂岩型铀成矿研究中的应用--以川北砂岩型铀矿床为例

本文在系统的取样分析基础上,总结了川北砂岩型铀矿床的稀土元素地球化学特征,分析研究了围岩、矿石、方解石脉和铀矿物的稀土元素组成、关系,讨论了岩、矿石沉积和成岩过程的稀土元素变化规律,与国内外典型的火山岩型和变质岩型热液成因铀矿床进行了对比,认为川北砂岩型铀矿具有热液（水）改造成矿作用的稀土元素地球化学特征,铀矿化经历了沉积成岩和热液改造富集两个阶段,为砂岩型铀矿成矿研究提供了新的思路。     

川北砂岩型铀矿稀土元素特征及铀成矿作用

在大量取样分析的基础上 ,本文系统分析研究了围岩、矿石、方解石脉和铀矿物的稀土元素组成 ,讨论了岩石、矿石沉积和成岩过程中的稀土元素变化规律 ,总结了川北砂岩型铀矿床的稀土元素地球化学特征。通过与典型的火山岩型和变质岩型热液成因铀矿床进行对比 ,认为川北砂岩型铀矿具有热液 (水 )改造成矿作用的稀土元素地球化学特点 ;铀矿化经历了沉积成岩和热液改造富集两个阶段。     

陕西省中部地区白水矿点铀矿化成因探讨

通过对白水矿点蚀变带中变价元素V,se,Mo.Re,Fe3 /Fe2 和素硫元素Cu,Pb,As.Cd,Sb与U 含量的配置分析,认为白水矿点的铀矿化经历了早期沉积成岩的预富集,后期发育层间氧化带型铀矿化的地球化学作用过程,并在断裂构造的沟通下叠加热液改造作用.     

内蒙古东胜大型砂岩型铀矿床稀土元素地球化学研究

东胜砂岩型铀矿位于鄂尔多斯盆地北部,矿化受灰绿色砂岩控制,不同于典型层间氧化带成矿模式。在前人研究的基础上,本文系统的总结了该铀矿床的稀土元素地球化学特征,讨论了水-岩反应过程中稀土元素地球化学行为。对围岩、矿化砂岩及铀矿石的稀土元素组成、关系及成因研究发现REE与U呈正相关性,对铀矿化具有指示意义,各类岩石稀土配分曲线形态相似但又存在差异,说明它们沉积成岩环境相同,形成不同品位铀矿体的流体具有不同来源和演化过程。元素等位线研究表明,稀土元素在不同成矿过程表现出不同的活动性,总体可以划分两个过程,一是低品位铀矿石的形成过程,稀土元素活动性较弱;一是高品位铀矿石的形成过程,稀土元素活动性明显增强。结合Ce、Eu异常和REE活动性特征,认为区内铀矿化流体以具低温及偏碱性特点的地下水为主,REE主要以[REE(CO_3)_3]~(3-)的形式迁移,pH、Eh及温度压力的降低是导致U和REE沉淀的重要因素。     

鄂尔多斯盆地南缘白水矿点铀矿化成因探讨

本文通过对白水矿点蚀变带中变价元素V、Se、Mo、Re、Fe3+/Fe2+和亲硫元素Cu、Pb、As、Cd、Sb与U含量的配置分析,认为白水矿点的铀矿化经历了早期沉积成岩的预富集,后期发育层间氧化带型铀矿化的地球化学作用过程,不排除叠加了热流改造作用的可能.     

钱家店铀矿床含矿建造后生改造作用探讨:来自蚀变特征及地球化学的证据

基于开鲁盆地钱家店铀矿床含矿砂岩的偏光显微镜、扫描电子镜显微镜下观察以及元素地球化学分析,探讨了该砂岩型铀矿的形成过程.镜下观察结果显示,该矿床矿石中存在5种矿物蚀变作用类型:高岭石化、褐铁矿化、碳酸盐化、重晶石化和水云母化;钻孔伴生元素特征表明,钱家店部分铀矿体在初次形成后,可能又遭受后期流体叠加改造作用;元素迁移特征表明,矿区总体可能经历了两期不同性质的成矿流体,前期流体导致矿化砂岩的形成,后期流体在此基础上叠加改造,使铀再次富集成高品位铀矿石.综合前人研究资料,认为钱家店铀矿床经历三阶段成矿流体作用:第一阶段为同生沉积铀成矿;第二阶段为油气/热液改造叠加成矿;第三阶段为层间氧化铀成矿.     

鄂尔多斯盆地北部延安组白色砂岩形成的稳定同位素示踪及其地质意义

鄂尔多斯盆地东北部延安组顶部存在大规模的白色砂岩,形成当地的大型高岭土矿床。该白色砂岩与东胜—杭锦旗一带发现的大型砂岩铀矿含矿层位直罗组相邻相近;研究表明白色化与铀矿的富集保存、控矿砂岩的绿色蚀变、碳酸盐化等空间关系密切,成因相似,均与盆地中部上古生界天然气向北运移耗散所导致的低温气-水热液流体中烃类还原的流-岩作用有关。文中重点从稳定同位素示踪白色砂岩形成的地球化学成因机制和过程,同时也指示了本区存在天然气耗散的动力学背景。高岭石氢氧同位素揭示白色化砂岩形成的高岭土矿床成因以低温热液作用为主,与东胜铀矿形成的低温热液作用为同一性质及事件;高岭石硅同位素与铀矿石中铀矿物铀石的硅同位素数据相近,而与成岩作用黏土的硅同位素特征相去甚远,进一步证明了白色砂岩与铀矿化是在同一低温热液事件作用下的产物。碳氧同位素说明白色砂岩形成的流体与有机质来源有关,结合东胜砂岩铀矿有机地球化学及本区天然气耗散地质事件的背景,认为该有机质来源于向北耗散的上古生界天然气。方解石包裹体氢氧同位素特征表明,流体中水的性质和来源为大气降水。系统总结和综合以上认识认为,本区白色砂岩的形成过程是,中部上古生界低温天然气向北运移耗散至浅部延安组—直罗组,与地下水一起构成低温"天然气-水"混合热液,该低温热液的烃类还原作用同时导致了本区延安组顶部白色砂岩的形成以及直罗组下部东胜铀矿的富集保存、砂岩的绿色化和碳酸盐化等蚀变现象,从而形成本区东胜超大型铀矿及大型高岭土矿床和相关的烃类还原蚀变现象,构成现今多种能源及相关资源同盆共存、共荣的局面。     

广西373铀矿床微量元素地球化学特征及其成因探讨

373铀矿床是我国南方典型碳硅泥岩型铀矿床之一,主要发育一套黑色弱硅化泥岩、粉砂岩,硅化生屑灰岩及其过渡型岩类地层,矿床明显受断裂发育影响,铀矿化于次级断裂带中.通过系统地球化学研究表明:3组不同期次脉体普遍亏损过渡元素Ti、Sc、Cr、Cu、Zn和高场强元素Nb、Ta、Zr和Hf;相对较富集Mn、Ni、As、Sr、Mo、Sb、Tl和U等微量元素.后期热液活动使脉体Ba、Sb、As和Mo等元素异常富集.后期热液叠加改造,使得岩石普遍亏损过渡元素Sc、Ti、Cr和高场强元素Nb、Ta、Zr、Hf,普遍富集Co、Ni、Zn、As、Sb、Mo、Cd、W、Tl、Pb、Bi和U,其中As、Sb、Mo、Tl和U尤为富集,富集系数平均达到100左右,U与W、As、Sb和Pb相关系数都在0.9左右,具有高度同源性,铀成矿与热液活动有关.典型剖面微量元素富集与硅化密切相关,当硅化达到一定程度后微量元素富集出现反转,即随着硅化强度增加而富集能力反而降低.V/Cr、V/Sc、Ni/Co、V/(V+Ni)、U/Th、δU、δEu和δCe等特征元素比值反应铀预富集形成于缺氧的古海洋环境.高丰度的As、Sb和Ba等元素,以及U-Th关系图解和Zn-Ni-Co三元图解均显示热水沉积成因.微量元素特征表明碳硅泥岩形成于缺氧的还原环境,铀预富集与热水沉积有关,铀成矿与热液叠加改造有关,后期热液沿运移通道上升进入储集空间,与铀预富集地层热液叠加成矿.     

鄂尔多斯盆地东胜铀矿田铀源示踪及其地质意义

笔者以鄂尔多斯盆地东胜铀矿田的典型矿床——纳岭沟铀矿床为主要研究对象,通过铀矿体及围岩岩石地球化学、电子探针及稳定同位素测试等方法,综合分析了东胜砂岩型铀矿田的铀源及其地质意义。结果表明:主要含矿目标层中侏罗统直罗组在同生沉积过程中,铀预富集达212.45×10~(-6),围岩达41.34×10~(-6);预富集铀主要来自于盆地北缘蚀源区;铀矿体及围岩REE配分曲线总体具一致性,右倾,个别δEu正异常,富集重稀土,两者铀源具一致性;含铀砂岩δ~(13)C_(V-PDB)=-9.7‰,δ~(18)O_(SMOW)=18.9‰,黄铁矿δ~(34)S_(v-CDT)=-27.46‰,经历了强烈的有机地质作用;铀石围绕炭屑、星散状黄铁矿产出,被胶状黄铁矿肢解,铀富集于成岩作用后期。由此认为,直罗组同生沉积过程中预富集的铀为主要成矿铀源,东胜铀矿田属直罗组预富铀重新分配的产物。     

赣南双坑铀矿床围岩蚀变及其地球化学特征

文章阐述了赣南双坑铀矿床的近矿围岩蚀变特征,指出与成矿密切相关的围岩蚀变主要有赤铁矿化、水云母化、绿泥石化和碳酸盐化。双坑铀矿床的矿化蚀变岩石元素地球化学研究表明,从矿化中心至围岩,V、Mo、Bi、Cu含量变化趋势与 U 一致,具有正相关性;与铀密切相关的元素为 V、Sb、Pb、Bi、HREE、Be、Co等。这些元素可作为该区铀成矿的地球化学标志。     

云南牟定戌街地区铀矿化特征及成因探讨

云南牟定戌街1101铀矿区位于扬子地台西南缘,康滇地轴中南段,是我国西南地区产于元古界变质岩中的铀矿之一。通过对矿化区岩石及矿石的岩石学、矿物学、地球化学及年代学特征进行研究,分析了铀矿的形成条件,揭示了铀成矿规律。研究发现:①牟定戌街地区铀矿化赋存于斜长角闪岩、角闪斜长片麻岩和二云母石英片岩等变质混合岩中,主要铀矿物为晶质铀矿、钛铀矿及次生铀矿,含铀矿物有榍石、锆石,硫化物丰富,围岩蚀变主要为硅化、赤铁矿化、碱交代等;②牟定1101铀矿化地区混合岩化岩石的地球化学特征表现为高钾钙碱性-钙碱性系列岩石;③研究区混合岩形成于1 056 Ma左右,铀矿形成于845 Ma左右,为新元古代产物;④牟定1101地区铀成矿受构造、岩性控制,与混合岩化作用、构造热液活动及碱交代作用关系密切,属热液成因铀矿。     

内蒙古东胜地区中侏罗统砂岩沉积物源的地球化学证据

基于显微薄片观察、稀土和微量元素分析探讨了鄂尔多斯盆地北部东胜地区中侏罗统直罗组砂岩的物源和铀矿化的地球化学特征。砂岩样品含有多种的变质岩岩屑应来自盆地北部的变质岩,那里的花岗片麻岩和斜长角闪岩分析显示:花岗片麻岩LREE/HREE为19.02,斜长角闪岩LREE/HREE为4.47。这两类母岩LREE/HREE比值分别接近于砂岩最高和最低LREE/HREE比值,其稀土配分曲线模式与砂岩LREE/HREE比值端元岩样可以对比,说明砂岩的母岩主要来自这两类变质岩。花岗片麻岩Th/U高,表明发生铀丢失,可作为本区铀成矿的重要铀源。有意义的是,铀含量高的样品,其LREE/HREE比值高,铀含量与亲硫的微量元素Pb、Zn和Mo具有相关关系,这些特征可作为铀矿化的重要标志。     

Geological and Geochemical Characteristics of the Zhiluo Formation in the Bayinqinggeli Uranium Deposit, Northern Ordos Basin: Significance for Uranium Mineralization

The Bayinqinggeli deposit in the northern Ordos Basin, northwestern of China, is a recently discovered sandstone-type uranium deposit. The uranium (U) orebodies are generally hosted in the lower member of the Jurassic Zhiluo Formation (Fm.), and are primarily tabular or irregular in shape. In the study area, 23 sandstone samples were collected from the Zhiluo Fm. and analyzed for major, trace, and rare earth elements (REEs). The geochemical characteristics of these sandstones are used to evaluate the factors controlling U mineralization. The source rocks of the Zhiluo Fm. sandstones are mainly volcanic and felsic magmatic rocks formed in continental arc and active continental-marginal arc environments, and they provided the material required for the mineralization. The index of compositional variability ranges from 1.02 to 3.29 (average1.38), indicating that the Zhiluo Fm. sandstones are immature and composed of first-cycle sediments. The corrected chemical index of alteration averages 56, suggesting that the source rocks underwent weak chemical weathering. The ore host rocks are loose, providing favorable conditions for epigenetic oxidation and U precipitation and enrichment. Ferrous iron in minerals such as chlorite, biotite, ilmenite, and pyrite might have played a role either in adsorbing or reducing the uranium.     

Geochemical indicators of gold-rich zones in the La Josefina epithermal deposit,Deseado Massif,Argentina

The gold deposit at La Josefina, in the Deseado Massif of Argentina, is a low-sulfidation epithermal deposit with some features of the intermediate sulfidation style; the Au occurs in quartz veins and hydrothermal breccias hosted by acid pyroclastic rocks produced by Jurassic bimodal volcanism. Exploration for this deposit type uses geochemical data for vectoring to mineralized rocks. Although a general suite of elements with anomalous concentrations around low-sulfidation deposits is known, that suite varies amongst individual deposits, which should be studied individually. The aim of this study was to determine, in the La Josefina deposit, geochemical indicators of Au-rich rocks at different scales and to assess the effects of weathering on those indicators. To reach these objectives, a mineralized zone (hosting Au-rich veins) and a non-mineralized zone (hosting barren veins) were compared in terms of vein mineralogy, alteration minerals and geochemistry. These zones were also compared with estimated element concentrations of the protolith. Element concentrations in the mineralized zone were then plotted against distance to the Au-rich veins, separating the dataset into two subsets: one from strongly oxidized rocks and the other from weakly oxidized rocks, considering the degree of oxidation as indicative of relative degree of weathering. Based on alteration and vein mineralogy, we interpret that the mineralized zone was hydrothermally active before, during and after Au-mineralization, while the non-mineralized zone was active only before Au-mineralization. Therefore, differences in element concentrations between the estimated protolith and the non-mineralized zone represent geochemical changes produced before mineralization, whereas differences between mineralized and non-mineralized zones represent changes produced during and after mineralization. We conclude that in rhyolitic to rhyodacitic pyroclastic rocks of the study area, affected by predominantly argillic and silicic hydrothermal alterations, high concentrations of Au, Cu, Hg, V, Co and P, and low concentrations of Ba are probably the best deposit-scale geochemical indicators to distinguish Au-mineralized zones from non-mineralized zones. High concentrations of As, Mn, Fe, Pb, Cr, Ni, MgO and Zn (as well as high values of chlorite-carbonate-pyrite index), and low concentrations of Be and CaO can also distinguish mineralized from non-mineralized zones. High concentrations of Au, Cu, Pb, As, Hg, and Co indicate Au-rich zones, independently of lithology and alteration, because they were introduced into the veins and host rocks together with Au. At detailed-scale, the concentrations of 15 elements vary with distance to Au-rich veins; therefore, those elements are considered potential indicators of proximity to Au-rich veins. Of those elements, Au, P, Cu, Pb, Hg, Ba and MgO are the strongest indicators of proximity to the Au-rich veins. In strongly oxidized rocks, some indicators of mineralized zones (Co, Mn, Pb, Zn and MgO) and some indicators of proximity to Au-rich veins (P, Au, Cu, Hg and Ba) should be used with caution or be avoided because weathering modifies their quality as indicators.     

西准噶尔白杨河铍铀矿床中铍与铀成生关系初探——来自围岩蚀变和矿石矿物接触关系的证据

与高硅富氟火成岩(流纹岩或花岗斑岩)有关的铍矿床中常伴有铀矿化,其成矿特色明显,是认识岩浆-岩浆热液-热液演化过程中铍与铀地球化学行为异同的理想对象,但其中铍与铀成矿的时空关系及成因关系尚不清楚。为了理解该类矿床中铍与铀的成生关系,并为区域内铍与铀的找矿勘查提供理论支撑,本文选取该类矿床的典型代表—西准噶尔白杨河铍铀矿床为研究对象,通过镜下观察、扫描电镜能谱和激光拉曼光谱分析,对矿区内单铍矿石、单铀矿石和铍铀矿石开展了系统的岩相和矿相学研究。结果显示,与铍矿化相关的围岩蚀变为钠长石化、电气石化、白云母化、萤石化、碳酸盐化和绿泥石化,与铀矿化相关的围岩蚀变为硅化、赤铁矿化、萤石化、伊利石化和锰矿化(含少量铅),且铍铀矿石中可见沥青铀矿切穿羟硅铍石的现象。结合铍与铀的地球化学行为和前人研究成果,认为白杨河铍铀矿床中铍矿化与铀矿化应是不同期热液作用的结果:铍矿化可能是花岗斑岩深部岩浆房分异的岩浆热液在不断演化过程中形成的,而铀矿化可能与后期流体(如幔源流体、加热循环的大气降水等)的淋滤作用有关。     

Mobile Pb-isotopes in Proterozoic sedimentary basins as guides for exploration of uranium deposits

Lead isotope ratios and associated trace element concentrations (U, Th and Pb) extracted by partial-leaching with 2% nitric acid from Proterozoic sandstones and basement rocks reveal much about the fluid evolution of sedimentary basins hosting unconformity-type uranium deposits. In addition, these techniques have great potential as a guide for exploration of uranium and other types of deposits in basins of any age. Isotope ratios of Pb in Proterozoic sandstones from basins known to contain high-grade uranium deposits are radiogenic at key geological localities and settings distal to known mineralization and particularly in altered zones proximal to mineralization. Sandstones completely cemented by quartz overgrowths typically have non-radiogenic Pb isotope ratios, indicating early closure of porosity and isolation of these rocks from later fluid events. Alternatively, the unconformity served as both a source of uranium and radiogenic Pb as well as an avenue for late-stage (<250–900 Ma) fluid flow. The mafic volcanic units, which are relatively reducing lithologies and therefore have removed uranium from basinal brines, have uranium-supported radiogenic Pb isotope ratios. Comparison of ²³⁸U/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁴Pb ratios is useful in determining the timing and nature of U and Pb migration before, during and after mineralization in these basins. This comparison can be used to delineate the presence of radiogenic Pb isotope ratios that are not internally supported by uranium and thorium in rocks, eventually providing the explorationist with geochemical vectors that point toward sites of high potential for economic uranium mineralization.     

豫西嵩县上庄坪铅锌银矿床地球化学特征及地质意义

上庄坪铅锌银矿床是新一轮国土资源大调查中在北秦岭二郎坪群发现的硫化物矿床。笔者通过对矿床矿石、容矿同岩、重晶石岩的微量、稀土元素地球化学特征分析和地质特征研究,探讨成矿构造环境、成矿物质来源及矿床成因问题。研究表明.矿石和容矿围岩稀土元素球粒陨石标准化组成模式均为右倾型.矿石与围岩在Cu-Pb-Zn判别图解中投点区域一致.矿石Zn/(Zn Pb)与冲绳海槽和上向黑矿矿石特征相似、与TAG和EPR13°N区硫化物存在差异.矿石具较高As、Sb和Pb与低Cu、Cd和Se元素特征.认为该矿床成矿元素来源于壳幔混合、但以壳源为主的围岩变(石英)角斑岩和变细碧岩。矿石稀土元素、微量元素地球化学特征、矿床地质特征及与热水沉积重晶石岩和硅质岩的紧密共生关系说明,上庄坪矿床是弧后盆地构造环境海底热液喷流成岩成矿作用的产物。重晶石岩、硅质岩、矿床纵向和横向分带是寻找和勘探该类矿床的重要标志和依据。     

内蒙赤峰安家营子金矿微量元素特征

通过对未蚀变岩石、近矿蚀变围岩及矿区内产出的黄铁矿中微量元素的分析对比，指出本区最佳指示元素是Ａｕ、Ｃｕ、Ｂｉ、Ｐｂ、Ｍｏ、Ａｓ；矿区产出的黄铁矿都富含Ａｓ、Ｓｂ、Ｂｉ，但富金黄铁矿中还富含Ｃｕ、Ｚｎ、Ｐｂ；成矿温度影响着含金黄铁矿中微量元素含量，成矿温度高的矿床中黄铁矿之Ａｓ、Ｓｂ、Ｈｇ、Ｚｎ含量低，而更富金