Radiation-induced defects in quartz. IV. Thermal properties and implications

The thermal stabilities and decay kinetics of three peroxy radicals (Centers #1, B and B′) and three other radiation-induced defects (#3, C′ and E₁′) in natural quartz from the high-grade McArthur River uranium deposit (Athabasca basin, Canada) have been investigated by isochronal and isothermal annealing experiments and electron paramagnetic resonance (EPR) spectroscopy. Single-crystal EPR spectra of isochronally (2 h) annealed quartz show that these centers all grow in intensity to 280°C and then decay with further increase in temperature, but their disappearance temperatures differ markedly and depend on the initial concentrations (e.g., Center #1 in a dark smoky quartz is annealed out at 380°C, B and B′ at 420°C and #3 and C′ at 580°C). The isothermal decay processes of these centers are all of the second order type. The calculated activation energies for the peroxy radicals [#1 and B + B′ at 0.36 (9) and 0.83 (8) eV, respectively] are smaller than those of Centers #3, C′ and E₁′ [1.09 (8), 1.24 (8) and 1.45 (7) eV, respectively]. Gamma-ray irradiations of thermally bleached quartz restore a fraction of the peroxy radicals, suggesting that their diamagnetic precursors are stable up to at least 800°C. The unusual decay characteristics of “peroxy radicals” in quartz reported in the literature are shown to most likely arise from multiple radiation-induced defects. These results have implications for not only applications of peroxy radicals in quartz for EPR dating but also better understanding of thermoluminescence and cathodoluminescence spectra of this mineral.     

沉积盆地油气与砂岩型铀矿成矿关系研究

国内外许多砂岩型铀矿产于含油气盆地,油气参与砂岩型铀成矿作用越来越受到人们的重视;沉积盆地控制着油气田和砂岩型铀矿床的分布,多数盆地总体形成内部油气-边部铀矿、下部油气-上部铀矿的分布规律。文章认为油气藏与砂岩铀矿床相互联系的储集层系统及盆地有机/无机成因流体是两者同盆共存的物质基础,吸附作用和还原作用是油气参与砂岩型铀矿成矿的两种主要作用方式,重力流驱动的含铀流体与油气成藏过程中油气扩散形成的烃类流体相互混合是铀成矿作用的主要动力学机制,构造则是两种流体联系的纽带;油气与铀矿相互共生、相互作用,为"以铀找油"和"以油找铀"提供了基础。根据油气与铀的成因联系,结合石油勘探开发资料,提出利用油气田资料"二次开发"寻找砂岩型铀矿的思路和方法。利用油气田资料来寻找砂岩型铀矿,可节约大量勘探资金,提高油气田经济效益,经济价值高。     

地浸砂岩型铀矿成矿年代学研究

本文提出用铀矿石样品U-Ra平衡系数修正样品的铀含量,再进行U-Pb等时线拟合,从而获得产铀盆地中地浸砂岩型铀矿的成矿年龄。通过对中国北方主要产铀盆地砂岩型铀矿成矿年代学研究,发现砂岩型铀矿的成矿作用具有“幕式”及多阶段性特征。不同构造单元的盆地铀成矿时代有差异,表明了铀的成矿作用与盆地构造抬升的演化历史及古气候关系密切。     

Conditions of localization of Mesozoic auriferous metasomatites in crystalline base of Central Aldan region

We investigated the distribution of electron hole centers produced by natural radioactivity in arkoses and their principal components (quartz-feldspar intergrowths, white and smoky quartz, and feldspars) using the electron paramagnetic resonance method. The relation between the concentrations of the Ecenters and uranium content in the rock provides information on the genetic characteristics of uranium mineralization. —Authors.     

江西省峡江-广丰地区白垩纪红盆-火山盆地对铀成矿的制约探讨

江西峡江-广丰地区产铀盆地常具有特殊的三元结构:含铀火山岩发育在燕山早期的断陷区内,火山岩之下为一(几)套煤系地层,火山岩系之上为一套红色碎屑岩层,构成“黑-灰-红”特色三层结构的叠合式盆地。本文在总结前人工作的基础上,分析了该区叠合式盆地的空间分布、组成结构、形成演化和矿化等特征,并探讨区域构造演化对铀成矿富集的控制作用,以期为研究区铀矿勘查提供新的思路。研究表明:(1)叠合式盆地主要由多旋回的火山岩及其上部的巨厚红层组成,发育在前寒武系变质基底及较薄的峡山群(D2X)、安源群(T3A,含煤层)和林山群(J1L)之上。下白垩统武夷群(K1W)与火把山群(K1H)之间存在构造挤压事件,时限约为132~110 Ma,主要表现为近SN向的挤压和区域性抬升剥蚀,并导致NE和NW向两组共轭断裂分别发生左行和右行压扭,派生的近SN向断裂以张性为主。这些断裂构造是主要的控矿-赋矿构造,特别是近SN向张性断裂,富大矿体均赋存其中;(2)铀矿化时代晚于火山岩围岩的成岩时代,与红层沉积时代有很大程度上的重叠,暗示红盆发育过程对区内铀成矿起重要控制作用;(3)与铀矿物相伴生的萤石、石英中H、O、C同位素指示大气水对铀成矿的贡献,大气水对红层中的Fe^3+、F、Cl、H2S、(U)等进行淋滤,并携带至火山岩的构造裂隙中,在与深部来源流体共同作用下,使火山岩普遍发育水云母化、铀矿化等,因而成矿作用应滞后于火山作用。     

The investigation of defects in shock-metamorphosed quartz

The shock-metamorphosed quartz exhibits thermal luminescence (TL) with maxima at 365 nm, 470 nm and 610–680 nm. By electron paramagnetic resonance (EPR) analysis E₁ type electron centers and hole centers have been found which originate from vacancies including those from the substitution of Al³⁺ and/or Fe³⁺, for Si⁴⁺. The EPR and TL spectra may be interpreted mainly in terms of vacancy type defects associated with dislocations in the crystal structure of quartz.     

中国北方兴蒙地区叠合盆地砂岩型铀成矿特征及勘查方法综述

中国北方兴蒙地区发育多个中大型叠合盆地,盆地内均发现大型、特大型铀矿床,且最近又有许多新的找矿突破。兴蒙地区叠合盆地在铀成矿及勘查方法等方面具有很多共性。研究发现,铀成矿作用受特定的构造样式和构造演化阶段控制,有利的沉积相主要发育于盆地发展的坳陷期,局部为断陷期,在断陷期和断坳转换期形成了盆地内铀成矿的还原介质,在挤压隆升剥蚀期,构造反转、地层掀斜剥蚀形成剥蚀窗口,有利于含矿流体的运移。盆地内铀成矿作用的类型为:①潜水、潜水-层间和层间氧化作用;②同沉积成矿;③构造热事件叠加成矿;④多种流体混合作用成矿。根据这些成矿特征,盆地内的铀矿勘查可通过以下方式进行:①铀源体可通过源-汇系统进行厘定;②成矿流场和成矿通道通过反转抬升剥蚀窗口和有利沉积相厘定;③沉积建造、油气逸散场可利用其物性特征(电性、放射性等)进行厘定。地质及物化探方法组合可有效地完成上述勘查。     

鄂尔多斯盆地东北部砂岩型铀矿伴生矿物组合及其地质意义

特征矿物是地质作用的直接记录,研究铀矿物伴生组合类型和特征为探讨铀矿床成因提供直接信息.本文以鄂尔多斯盆地东北部杭锦旗-纳岭沟地区含铀岩系中侏罗统直罗组为研究对象,通过岩心观察、显微观察、扫描电镜和电子探针分析等,系统研究了含铀砂岩中铀矿物种类、赋存特征及典型矿物伴生组合类型,在此基础上,结合铀成矿过程中流体作用探讨了...     

集宁以东火山岩铀成矿带区域成矿条件和远景初析

集宁以东火山岩铀成矿带是一个较有远景的成矿带。本文在概要的阐述区域地质背景的基础上,着重讨论了该带的火山作用及其与板块活动的关系,提出了火山盆地分类和命名的基本原则。根据这些原则对本区火山盆地进行了较系统的分类,并归纳和总结了它们的基本特征及区域铀矿化的主要特点。指出本区铀成矿的火山盆地是上叠塌陷式、上叠沉陷式和上叠断陷式火山盆地,并分析了它们成矿的有利条件。在上述分析讨论的基础上,对本区区域成矿条件进行了综合分析,预测了一类成矿远景区有六个火山盆地,二类远景区有八个火山盆地,并指出了它们的找矿方向。     

四川盆地东北部砂岩型铀矿石及铀的存在形式特征研究

四川盆地东北部砂岩型铀矿含铀层位为下白垩统苍溪组,主要矿化产在苍溪组第一韵律层下部砂岩或砾岩层中.岩矿鉴定表明,主要含矿岩性为细—中粒砂岩,砂岩矿物碎屑主要为石英,胶结物主要为方解石,含少量黄铁矿.扫描电镜和电子探针分析表明,含矿岩石中除了矿物碎屑石英、胶结物方解石和黄铁矿外,还含有钛铁矿、方铅矿和铀石.铀石为岩石中铀...     

基于便携式色度、X荧光及高光谱的砂岩铀成矿环境研究——以鄂尔多斯盆地西北部特拉敖包铀矿产地为例

选取经济高效、轻便无损的分析技术是当前砂岩型铀矿绿色勘查和研究的现实需求。本文基于便携式色度、X荧光（XRF）、高光谱的光谱学技术,全面表征了鄂尔多斯盆地西北部特拉敖包铀矿产地环河组红杂色含矿建造的地质地球化学特征;构建了不同颜色砂岩的定量标准色度区间,查明了红色砂岩具有赤红色强氧化、褐（紫）红色较强的差异后生氧化作用;过渡带褐灰色和灰绿色砂岩普遍具有一定的弱氧化性,红度a的曲线发生多次渐变过渡,矿带内部存在多个氧化还原的地球化学界面,形成了多段的铀-钼-钒-铌等变价元素的共伴生富集。以上信息指示了研究区氧化还原作用的主成矿机制;绿色还原砂岩的红度值最小,是后期碱性还原流体渗出改造的产物。流体活动导致环河组地层发育绿泥石化、铁的还原-迁出、局部碳酸盐化等蚀变。该研究为沉积盆地不同地球化学性质含铀建造多尺度的铀成矿环境快速评价提供了案例及重要参考。     

二连盆地隆起带阿其图乌拉凹陷铀成矿环境与远景预测

阿其图乌拉凹陷为二连盆地隆起带上众多的含铀山间盆地之一。本文首次在现有钻探资料的基础上,结合区域地质特征,对阿其图乌拉凹陷赛汉组的铀成矿环境进行了详细分析,并综合铀储层、后生蚀变和铀源等因素对铀成矿前景进行了预测。研究认为,研究区目的层具有来自北部苏尼特隆起的丰富铀源,且铀源近。赛汉组上段和下段均具有完整的利于成矿的"泥-砂-泥"结构,发育大型呈泛连通的辫状砂体,发育潜水-层间氧化带,且控制矿体的产出等。赛汉组上段及下段均具有非常有利的铀成矿环境。远景区处于辫状河三角洲砂带中部的氧化-还原过渡带及灰色残留体上,资源潜力较大。     

隆起对砂岩型铀矿成矿的控制及找矿启示

沉积盆地古隆起对油气成藏起到明显控制作用,对砂岩型铀矿成矿的制约也不可忽视。砂岩型铀矿通常就位于盆地边缘构造斜坡带和盆地内部隆起附近。隆起对砂岩型铀矿成矿的控制具体体现在:控制地下水补-径-排体系、控制层间氧化作用、控制沉积相带发育、伴生断裂促进物质输运以及为成矿供给铀等。中国北方沉积盆地中新生代以来经历复杂的构造活动,盆地域内非均衡发展而多形成隆起,因此我国铀矿找矿尤其需要重视隆起对铀成矿的控制。其中,盆地内部找矿应重点关注被大幅抬升的隆起,而盆地边缘构造斜坡带上找矿需重视微隆起以及基底上覆地层的褶皱。将隆起作为关键控矿要素,优选适用的攻深找盲方法,精细刻画盆地基底隆升形成的背斜、褶皱及伴生断裂,可有效提高铀矿找矿效率并拓展铀矿找矿空间。     

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.     

我国含铀煤矿床的某些地球化学特征

我国含铀煤矿床主要产于中-新生代陆相沉积盆地中。盆地基底为华力西至燕山期花岗岩(黑云母花岗岩、二云母花岗岩等),或酸性火山岩(火山碎屑岩),或二者均有,其含铀丰度大于8ppm,高于酸性岩克拉克值的3-10倍。基底含铀丰度高为成矿提供了丰富的铀源。铀矿区内的地下水一般为弱酸至弱碱性,重碳酸钾-钠型,硫酸、重碳酸钙(钾)一钠型等，pH值6 -7.5，含铀丰度为n.10-7n.10-6克/升，干旱地区为n。10-6-n.10-5克/升。矿体一般为层状，似层状及透镜状与煤层整合产出。     

滇西新生代盆地与砂岩型铀矿成矿

滇西新生代盆地内蕴藏着丰富的铀资源,现已探明8个中、小型砂岩型铀矿床,是中国重要的砂岩型铀矿成矿带之一。本文在收集研究前人施工钻孔资料1200个,施工钻孔25个的基础上,编制岩性-岩相-地球化学剖面图66张,研究了滇西新生代盆地与砂岩型铀矿成矿。认为滇西地区存在2种类型的新生代盆地,其盆地沉积演化、火山活动、地貌景观等不同,砂岩型铀矿成矿条件亦存在差异,成矿的专属性体现在于盆地的差异性。砂岩型铀矿成矿最有利的是北部腾冲地区找矿目的层上覆地层发育了区域性隔水层、存在火山活动、深切割低山-丘陵-河谷阶地地貌的新生代盆地。     

Patterns of ore localization and the mineral composition of ores and ore-bearing rocks of the Koretkonde uranium deposit (Vitim ore-bearing region)

This work presents the geological structure of the Neogen uranium-bearing ore sedimentary strata that filled the paleovalleys of the Koretkonde deposit. As a result of work we carried out, productive deposits were stratigraphically divided, the patterns of the localization of uranium mineralization were studied, and lithological and mineralogical ore-controlling factors were revealed. The main mineral phases of uranium were identified with scanning-electron microscopy and microprobe studies. In the future, a more detailed study of the deposits is planned in order to reveal methods for improving the efficiency of their exploration and organize the search for uranium deposits of such a type within the Vitim uranium-bearing ore region to expand the mineral resource base of Russia.     

鄂尔多斯盆地南缘彬县地区铀成矿关键时期的古地貌特征

中侏罗世为直罗组下段沉积期,辫状河道为有利的铀储层砂体,铀矿(化)体主要赋存于辫状河砂体中,受沉积古地貌控制,主要发育在低洼区。晚侏罗世、早白垩世-古新世、始新世-中新世是砂岩型铀成矿期,古地貌控制了地下古水流的流向,控制着氧化还原带的分布和铀矿的富集:晚侏罗世铀预成矿期,古隆起区受到潜水淋滤,含铀物质向斜坡和低洼区迁移;早白垩世-古新世铀主成矿期,古地貌控制了含氧含铀水的水流方向,氧化还原带主要分布在古地貌斜坡区。     

相山铀矿床多期石英的天然热释光及EPR特征

本文对采自江西相山铀矿床不同成矿期的石英进行了天然热释光测定，并结合ＸＲＦＳ（Ｘ射线荧光光谱）、ＥＰＲ（电子顺磁共振）等分析数据对所取样品的天然热释光特征进行了研究。研究结果表明：不同成矿期石英的天然热释光在发光强度、发光谱线的峰形特征等方面存在明显差异；导致石英热发光的中心是ＳｉＯ３－３型电子心，电子心的多少与Ｕ、Ｔｈ总量有关；石英热释光强度与石英本身的颜色呈反消长关系；热释光发光谱线上的峰形特