大新矿床构造地球化学分带及铀多金属成矿规律研究

大新矿床产出于直接覆于上寒武统之上泥盆系间的构造破碎带中。笔者对该破碎带进行了详细地质调查和系统取样分析,研究表明,该破碎带发育从原岩带→碎裂岩带→构造泥→糜棱岩带→构造角砾岩带的构造地球化学分带规律。随着构造破碎带破碎程度的增强,U、Mo、As、Sb、Re和Tl等元素同步增高。铀多金属矿化对围岩无选择性,仅与破碎带的存在相关联,而且矿化程度与破碎强度呈同步消长关系,由此认为,大新矿床属于受构造破碎带控制的铀多金属热液矿床。     

青海都兰红旗沟金矿床构造叠加晕深部找矿预测

红旗沟金矿床是青海省五龙沟矿集区Ⅸ号含金破碎蚀变带中的典型金矿床。文章通过对矿床元素组合、元素相关变化特点及主矿体赋矿构造中原生晕分布、组分分带、垂(轴)向分带序列变化规律、原生晕叠加特点等地球化学特征的综合分析,探讨了该矿床成矿热液活动地球化学规律和找矿标志模型,圈定了矿床深部第二富集带及矿化带深部有利盲矿赋矿空间,预测矿区深部具有较大的找矿潜力。     

甘肃龙首山革命沟矿床铀矿化特征及成因探讨

革命沟矿床位于龙首山成矿带芨岭岩体的北带,矿石种类较多,通过对主要矿石进行研究表明,不同矿石具有不同的地球化学特征,也发育不同的矿化蚀变组合,但均表现为强烈硅化为主的酸性热液蚀变特征,硅含量明显增加,主要形成沥青铀矿物。综合分析认为,革命沟矿床是以充填裂隙和热交代作用为主的热液成因矿床;铀矿化受革命沟断裂及其次级断裂和构造角砾岩、大理岩与角闪岩岩性界面及硅化蚀变带所控制。     

胶东大尹格庄金矿床构造蚀变分带特征与成矿关系

大尹格庄金矿床是胶西北地区的特大型金矿床,为典型的破碎带蚀变岩型金矿床。研究大尹格庄金矿构造蚀变分带规律,对胶西北地区矿床研究及深部外围找矿有重要意义。通过对大尹格庄金矿床构造蚀变分带特征,以及各带岩石的岩相学、岩石地球化学、构造应力测算的系统研究,揭示大尹格庄金矿构造蚀变成矿的构造地球化学和构造物理化学过程。研究表明,(1)矿床断裂下盘由远矿围岩到矿体的构造蚀变分带模式为：弱钾化花岗质蚀变岩带→强钾化花岗质蚀变岩带→绢英岩化钾化花岗质蚀变岩带→黄铁绢英岩带(金矿主要发育带);(2)金矿由远矿蚀变带→黄铁绢英岩带,古构造差应力值呈现由小到大的变化趋势;(3)由远矿蚀变带→黄铁绢英岩带,Si、Na、Ba、Sr迁出,K、Fe、Cu、Zn、Pb迁入,Au含量不断增加,在未蚀变到弱钾化阶段,元素总体含量变化幅度较小,而在强钾和绢英岩化阶段变化幅度较大。成矿过程中构造应力场与岩石组分迁移具有耦合关系,绢英岩化阶段古构造差应力值较大,岩石破碎产生张性空间,同时元素含量变化幅度大,热液活动强烈,易富集成矿。     

准噶尔盆地东部将军庙地区砂岩型铀矿层间氧化带地球化学特征初步研究

通过对目的层层间氧化分带岩石学、地球化学指标、常量元素及其变化规律的分析,初步研究了准噶尔盆地东部将军庙地区砂岩型铀矿的地质地球化学特征。研究认为:(1)将军庙地区的层间氧化带可分为强氧化亚带、弱氧化亚带、过渡带和原生还原带;(2)研究区氧化作用存在长时期间断,造成过渡带铀富集较弱,矿带范围较局限;(3)SiO_2、MgO和TiO_2与铀元素的富集具一定相关性。     

鄂尔多斯盆地东胜砂岩型铀矿微量和稀土元素地球化学特征

鄂尔多斯盆地东胜砂岩型铀矿的微量和稀土元素能为铀矿勘查提供地球化学标志。以东胜铀矿层位侏罗系及其中铀矿化为对象,针对砂岩型铀矿石、铀矿化砂岩和围岩几类地质体进行元素地球化学对比研究。东胜砂岩型铀矿微量元素地球化学特征表明,Pb、Mo与U关系极为密切,它们在铀矿石中最富集,铀矿化砂岩中次富集,砂质和泥质围岩中不富集;Pb和Mo可以作为东胜铀矿床矿化的指示元素,Pb、U和Mo蛛网图上构成的"W"式样可作为东胜地区砂岩铀矿化的指示模型。铀矿石、铀矿化砂岩、砂岩以及泥岩表现出相似的REE地球化学特征和配分模式,推断其具有统一的物源、沉积环境和构造背景。部分铀矿石明显富集HREE,显然在沉积成岩后期经历了(热液)改造作用。东胜铀矿化经历了沉积成岩和热液改造作用两个成矿阶段。     

内蒙古狼山中部糜棱岩化硅质条带状灰岩地球化学特征研究

狼山构造带是华北地台北缘巨型造山带的重要组成部分,韧性剪切带是狼山构造带内的主要构造形式之一,是地壳深层次构造的反映.对狼山Ⅱ号韧性剪切带西南缘糜棱岩化硅质条带状灰岩进行地球化学特征研究,以探讨不同变形强度的糜棱岩化硅质条带状灰岩与原岩的成分变异规律.常量元素、微量元素和稀土元素分析结果表明,与原岩中常量元素和微量元素含量相比较,变形强度不同的硅质条带状灰岩存在着差异变化.变形岩石中常量元素仅CaO为带出组分,其他均为带入组分;微量元素中富集Rr、Sr、Ba、Pb、Ti、Cr、Cu、Nb、Ta、Zr、Hf元素,Ni元素相对亏损.变形的硅质条带状灰岩与原岩的稀土元素配分模式图基本一致,表现为轻稀土元素富集、重稀土元素亏损的右倾斜曲线,具有明显的负Eu异常特征,表明稀土元素在韧性剪切过程中具有一定的相对稳定性和同源性.     

扬子-华夏接合带的韧性剪切与金的迁移富集关系

扬子与华夏地块间发育一条近东西向展布的巨型板块缝合带--华南中部复合混杂岩带,对其次级北东向剪切带(进贤-婺源韧性剪切带)进行的构造地球化学剖面研究发现:①剪切带中构造岩金元素含量总体上高于原岩中金元素含量,从剪切带边部至中心,从原岩带至糜棱岩化带、糜棱岩带,随剪切程度的逐渐增强,金元素含量逐渐增高;②金元素有2个峰值点,1个出现在韧性剪切最强的糜棱岩中,另1个出现在叠加于早期韧性剪切糜棱岩化岩石之上的晚期脆性破裂张性构造角砾岩中;③叠加在原岩(千枚岩、砾岩)上的晚期脆性破裂张性构造角砾岩金元素没有出现富集作用.说明韧性剪切及叠加在韧性剪切之上的脆性破裂均有利于金的富集成矿.     

粤北302铀矿床围岩蚀变的地球化学特征和成因研究

以粤北302铀矿床ZK23-2钻孔为研究对象,通过显微镜下薄片鉴定、岩石地球化学和流体包裹体分析等对该矿床的围岩蚀变进行研究。结果表明,302矿床蚀变种类繁多,蚀变类型主要有:碱性长石化、硅化、绢云母化、红化、绿泥石化、绿(褐)帘石化、碳酸盐化、高岭石化等。矿床表现出明显的垂直分带和水平分带特征。从上至下,将ZK23-2划分为4个蚀变带:红化、绢云母化带→硅化、红化、强绢云母化带(铀富集带)→绿泥石化、绢云母化带→弱蚀变或正常花岗岩带。岩石的主量元素、微量元素和稀土元素均规律变化,微量元素分布模式和稀土元素配分模式均与赋矿围岩长江岩体的趋势一致,说明蚀变作用对它们的影响小,致使蚀变岩石基本保持原岩的地球化学特征。各蚀变带包裹体的均一温度均低于220℃,属于中低温热液,惰性气体N2在各蚀变带包裹体中普遍存在,强蚀变带的包裹体气相成分中均含CO2,表明在铀矿的形成过程中,铀的溶解、迁移以及富集成矿作用与CO2气体密切相关并发生在N2环境中。此外,成矿期脉石矿物包裹体的均一温度和压力为正相关的平滑曲线,表明围岩蚀变的分带特征主要是由成矿热液流体的混合作用引起的。     

玻利维亚Laurani斑岩-浅成低温热液矿床地质特征及控矿因素

Laurani矿床是玻利维亚Altiplano盆地内典型的高硫化浅成低温热液矿床,发现和开采历史悠久,但研究程度低,控矿因素和找矿潜力不清。通过矿床地质特征精细解剖,文章查明了该矿床控矿因素,分析了深部找矿潜力。研究表明,构造-岩浆作用为其主导性控矿因素。火山穹窿构造与环状断裂约束了矿床的定位,侵入接触构造、爆破角砾岩筒和NE向断裂裂隙控制了矿体(脉)的形成和展布。岩浆岩为二长花岗斑岩、英安岩/英安斑岩和凝灰岩组合,属于高钾钙碱性、钾玄岩系列,具有较一致的锆石U-Pb年龄(约7.5 Ma),反映它们为晚中新世同期岩浆活动的产物。该矿床发育斑岩型Au-Cu、爆破角砾岩型Au-Cu、接触带型Cu-Au-Ag和热液脉型Au-Ag-Cu-Pb-Zn四类不同产出特征的矿(化)体。成矿元素组合分带显著,平面上Huari Humana断裂上盘为Au-Ag-Cu-Pb-Zn组合,下盘为Ag-Pb-Zn组合;垂向上深部为Au-Cu元素组合,浅部为Au-Ag-Cu-Pb-Zn元素组合。热液蚀变强且分带明显,平面上以英安斑岩为中心,从内至外依次为黄铁绢英岩化带→青磐岩化带→碳酸盐化带,泥化带不同程度地叠加在黄铁绢英岩化带和青磐岩化带内,石英-明矾石化-重晶石化主要沿热液脉型矿体及其旁侧分布;垂向上从深至浅依次为黄铁绢英岩化带→青磐岩化带→泥化带;钾硅酸盐化带目前尚未揭露,可能产在深部。成矿后弱构造作用使矿床得以较好保存,结合钻孔揭露深部存在斑岩型、爆破角砾岩型矿化,笔者认为Laurani矿床深部具有寻找斑岩型矿体的较大潜力。     

Structural and biological control of the Cenozoic epithermal uranium concentrations from the Sierra Pe?a Blanca, Mexico

Epithermal uranium deposits of the Sierra Pe?a Blanca are classic examples of volcanic-hosted deposits and have been used as natural analogs for radionuclide migration in volcanic settings. We present a new genetic model that incorporates both geochemical and tectonic features of these deposits, including one of the few documented cases of a geochemical signature of biogenic reducing conditions favoring uranium mineralization in an epithermal deposit. Four tectono-magmatic faulting events affected the volcanic pile. Uranium occurrences are associated with breccia zones at the intersection of fault systems. Periodic reactivation of these structures associated with Basin and Range and Rio Grande tectonic events resulted in the mobilization of U and other elements by meteoric fluids heated by geothermal activity. Focused along breccia zones, these fluids precipitated under reducing conditions several generations of pyrite and uraninite together with kaolinite. Oxygen isotopic data indicate a low formation temperature of uraninite, 45–55°C for the uraninite from the ore body and ～20°C for late uraninite hosted by the underlying conglomerate. There is geochemical evidence for biological activity being at the origin of these reducing conditions, as shown by low δ³⁴S values (～?24.5‰) in pyrites and the presence of low δ¹³C (～?24‰) values in microbial patches intimately associated with uraninite. These data show that tectonic activity coupled with microbial activity can play a major role in the formation of epithermal uranium deposits in unusual near-surface environments.     

比如盆地地质特征与铀矿找矿方向

比如盆地位于青藏高原中东部,是一个经历了多期构造活动、挤压叠合改造,以地层与断裂为界的中生代盆地。燕山晚期一喜山期以来,盆地由于经历了剧烈的构造变形,地层急剧抬升,并均已遭受区域变质,大多发生板岩化。盆地中未发现有疏松砂岩层,这对地浸砂岩型铀矿成矿不利。但从已发现的铀异常点、带及水系沉积物异常来看,表明盆地还是有热液型、变质岩型、花岗岩型铀矿的找矿前景。     

吐哈盆地西南缘砂岩型铀矿地质地球化学基本特征

文章通过对含矿目的层及其渗透性的分析、与成矿作用有关的常量和微量元素及部分特征性地球化学指标如有机碳含量、全硫含量、三价铁和二价铁比值的分析，以及流体包裹体成分和物理化学参数的测试，配合铀、铅、碳、氧、硫同位素的分析等方法，综合分析研究区内砂岩型铀矿的地质地球化学基本特征，认为：吐哈盆地西南缘砂泥岩互层地层结构完整且延伸稳定，属弱渗透一渗透性地层，对砂岩型铀矿成矿比较有利。据常量和微量元素分析，认为铀成矿存在着明显的地球化学分带性，其中，氧化带以有机碳和全硫(∑s)含量低、Th／u和Fe2O3／FeO及Ra／U比值高为特征；过渡带(成矿带)以Th／U比值低、∑S、Mo、Re含量高为特征；还原带则以明显的低Fe2O3／FeO、Ra／U比值，高有机碳含量为其特征。其他微量元素如Cu、Pb、Zn、Cr、Co、Ni、zr等及稀土元素在成矿过程中并未得到明显富集。经对相关岩石的铀．镭平衡、气液包裹体及相关同位素的研究，认为铀成矿具有多期次、年代新且集中于第三纪的特点；含矿目的层煤成气提供了成矿所需的还原环境；成矿作用铀源主要来自于含矿目的层本身；铀成矿古流体属低温浅成热液且主要来源于大气降水。     

下庄矿田气热高温铀成矿特征及年龄研究

本文报道了在下庄矿田花岗岩体接触带附近的剪切构造糜棱岩带中,存在受深色蚀变岩制约的气热高温型铀成矿,它是下庄矿田发生于晚侏罗世的一次重要铀成矿作用。文中指出了韧性剪切带及气热交代蚀变岩是铀成矿的共同控制因素,同时划分了４种气热高温矿石组合类型,对各组合电子探针分析的化学成分作了较详细介绍。文章还披露了作者所测的３个矿石晶质铀矿Ｕ－Ｐｂ同位素年龄（为１６５—１４６Ｍａ）,表明属晚侏罗世成矿。此外,对以往所划分的成矿期次提出了修改的商榷意见。     

鄂尔多斯盆地东北部纳岭沟铀矿床元素地球化学特征及其地质意义

纳岭沟铀矿床位于鄂尔多斯盆地北部,是我国目前已发现的可地浸砂岩型铀矿床之一。其受古层间氧化带控制,呈板状产于中侏罗统直罗组下段辫状河砂体中。笔者从元素地球化学分析入手,通过对不同蚀变砂岩的地球化学特征进行对比,认为蚀变砂岩主要化学成分的变化受成岩作用、水-岩作用,以及油气二次还原作用等影响,并且有机碳含量在矿化砂岩中较高,说明铀矿化与有机质关系密切。矿化砂岩中的微量元素相对富集或亏损明显,可能与成岩后期(热液)的改造作用有关。蚀变砂岩均表现出壳型花岗岩的微量和稀土元素特征,LREE相对富集,说明盆地北部的阴山、大青山古陆壳富铀花岗岩体是直罗组的主要物源。此外,δEu和δCe特征也表明纳岭沟铀矿床是在弱氧化-弱还原过渡性环境下形成。这些特征可作为找矿勘探的重要指示或标志。     

Geochemical soil sampling for deeply-buried mineralized breccia pipes,northwestern Arizona

Thousands of solution-collapse breccia pipes crop out in the canyons and on the plateaus of northwestern Arizona; some host high-grade uranium deposits. The mineralized pipes are enriched in Ag, As, Ba, Co, Cu, Mo, Ni, Pb, Sb, Se, V and Zn. These breccia pipes formed as sedimentary strata collapsed into solution caverns within the underlying Mississippian Redwall Limestone. A typical pipe is approximately 100 m (300 ft) in diameter and extends upward from the Redwall Limestone as much as 1000 m (3000 ft).Unmineralized gypsum and limestone collapses rooted in the Lower Permian Kaibab Limestone or Toroweap Formation also occur throughout this area. Hence, development of geochemical tools that can distinguish these unmineralized collapse structures, as well as unmineralized breccia pipes, from mineralized breccia pipes could significantly reduce drilling costs for these orebodies commonly buried 300–360 m (1000–1200 ft) below the plateau surface.Design and interpretation of soil sampling surveys over breccia pipes are plagued with several complications. (1) The plateau-capping Kaibab Limestone and Moenkopi Formation are made up of diverse lithologies. Thus, because different breccia pipes are capped by different lithologies, each pipe needs to be treated as a separate geochemical survey with its own background samples. (2) Ascertaining true background is difficult because of uncertainties in locations of poorly-exposed collapse cones and ring fracture zones that surround the pipes.Soil geochemical surveys were completed on 50 collapse structures, three of which are known mineralized breccia pipes. Each collapse structure was treated as an independent geochemical survey. Geochemical data from each collapse feature were plotted on single-element geochemical maps and processed by multivariate factor analysis. To contrast the results between geochemical surveys (collapse structures), a means of quantifying the anomalousness of elements at each site was developed. This degree of anomalousness, named the “correlation value”, was used to rank collapse features by their potential to overlie a deeply-buried mineralized breccia pipe.Soil geochemical results from the three mineralized breccia pipes (the only three of the 50 that had previously been drilled) show that: (1) Soils above the SBF pipe contain significant enrichment of Ag, Al, As, Ba, Ga, K, La, Mo, Nd, Ni, Pb, Sc, Th, U and Zn, and depletion in Ca, Mg and Sr, in contrast to soils outside the topographic and structural rim; (2) Soils over the inner treeless zone of the Canyon pipe show Mo and Pb enrichment anf As and Ga depletion, in contrast to soils from the surrounding forest; and (3) The soil survey of the Mohawk Canyon pipe was a failure because of the rocky terrane and lack of a B soil horizon, or because the pipe plunges. At least 11 of the 47 other collapse structures studied contain anomalous soil enrichments similar to the SBF uranium ore-bearing pipe, and thus have good potential as exploration targets for uranium. One of these 11, #1102, does contain surface mineralized rock. These surveys suggest that soil geochemical sampling is a useful tool for the recognition of many collapse structures with underlying ore-bearing breccia pipes.     

Geochemical controls on the formation of unconformity-type Au–U deposits (Northern Transbaikalia)

This study provides geochemical, mineralogical, and isotope data for rocks and ores from Lower Proterozoic black shale formations of the Kodar–Udokan structural and formational zone, which host the Khadatkanda gold—uranium deposit. The results indicate that the uranium and gold mineralizations were formed at different times in relation to different geodynamic settings. The gold mineralization is associated with the inception of the Syulban fault and has a juvenile source. The later Th–U mineralization originated during tectonic rejuvenation of the Syulban fault zone, while the sources of radioactive elements were presumably the underlying sediments of the Kodar Group, which are widespread throughout the area of the Baikal mountain region (BMR). Based on the above results, the Au–U mineralization in the study area can be recognized as unconformity-type deposits, analogous to the well-known deposits of Australia and Canada. In this connection, the Baikal mountain region has a good potential for the discovery of Au—U deposits.     

江西玉华山地区铀矿综合信息找矿模型研究

玉华山地区是赣杭构造带西南段重要的铀矿找矿远景区之一,毗邻中国最大的火山岩型铀矿田——相山铀矿田。玉华山地区基底变质岩、岩浆岩、断裂构造、热液活动和铀矿化特征指示区内具有较大的找矿潜力。与相山矿田对比,两者成矿条件基本相同,但在火山活动、晚期热液活动强度、剥蚀程度等方面存在较大差异。玉华山地区地球化学与地球物理异常特征表明,区内U-Th-Mo化探综合异常、正负磁异常交替和放射性正异常等异常叠加区是铀矿勘查的重点区域。同时,在成矿条件、地球化学条件与地球物理条件的基础上,构建了研究区综合信息找矿模型,为区内铀矿勘查工作提供了理论与实践依据。笔者认为为山—筒山断裂带是今后资源量突破所在,建议部署相关勘探工程,查明铀资源量。