沉积、成岩与铀成矿:中国砂岩型铀矿研究的创新发现与认知挑战

21世纪,中国在砂岩型铀矿勘查领域获得了前所未有的辉煌成就.砂岩型铀矿产出于沉积盆地,铀矿的形成必须经历由沉积埋藏到抬升成矿两个重要的演化阶段.其中,在抬升成矿阶段,大气降水和氧化-还原作用的参与和约束是最显著的成矿特征.显然,这是一种典型的表生成岩作用的产物,是铀储层复杂成岩序列中的重要一环,隶属于“外生成矿”的范畴.虽然,砂岩型铀矿的成矿作用遵循氧化还原与铀变价的普遍机理,但是特殊的沉积背景却导致了铀成矿作用的多样性和地区的专属性.一些由沉积作用、沉积环境和古气候造就的关键控矿要素,能够从“基因”上直接影响表生成岩阶段的铀成矿作用,由沉积、成岩到铀成矿是一个具有成因联系的地质过程,而盆山耦合机制始终是其最根本的原始驱动力.随着对铀成矿作用细节行为研究的深入,一些创新发现不断地冲击着以往固有的认识,诸如碳质碎屑与铀成矿的相互作用、黄铁矿复杂而有序的演化习性、碳酸盐胶结物与铀成矿的共生叠置、敏感矿物的流体示踪、铀储层非均质性制约下的铀成矿机理、双重还原介质制矿模型、铀成矿的复合地球化学障等.还有一些研究对传统地质学理论提出了认知挑战,诸如,铀储层开放成岩环境中碳质碎屑的“碳化作用机理”、黄铁矿溶蚀或者生长界面上的铀沉淀化学动力机制、干旱沉积背景的铀成矿机理等.同时,铀成矿机理和普遍规律的研究,也为砂岩型铀矿的衰变地质效应研究和盆地铀资源的系统探索奠定了良好的地质基础.相信,针对沉积盆地整装的系统的成矿机理与成因联系研究,必将释放巨大的盆地铀资源潜力和矿床产能,在进一步丰富铀成矿理论的同时助力实现“双碳目标”.      

相山铀矿田特富矿中铀磷关系的模拟实验研究

相山铀矿田中磷灰石对生成特富铀矿有着十分重要的作用。在研究特富矿体中含磷矿物的成分及矿物学特征,配合特富铀矿石硅酸盐化学分析结果的矿物计算及对特富铀矿石与蚀变岩、低品位铀矿石的化学成分比较的基础上,结合对铀成矿热液体系下一系列反应方程的热力学计算进行实验模拟。实验模拟的结果表明,氧化还原介质的变化不是磷灰石形成的重要条件,溶液体系中的pH值降低是特富矿形成的重要条件。磷灰石在弱酸性介质中吸附铀构成"铀磷共沉淀"之后,由于磷灰石的结晶,造成"铀、磷分离",从而使铀变得更富。这一研究成果很好地解释了富矿中磷灰石大量存在,而贫矿中磷灰石很少出现的客观地质事实。     

安徽庐枞火山盆地铀矿床类型研究

在收集整理前人成果基础上,着重分析了庐枞盆地铀成矿地质特征及地球化学特征。盆地内铀矿化与石英正长岩具密切时空关联,石英正长岩是与火山岩同源并有时空联系的潜火山岩;潜火山岩外带砂岩层间破碎带和贯通潜火山岩与砂岩的断裂及其旁侧裂隙密集带构造是主要控矿构造,隐爆角砾岩构造亦控矿;与铀矿物伴生的金属矿物为中低温热液矿床标型矿物,铀矿石伴生元素及矿床内普遍而强烈发育的硅化,与潜火山岩型金属矿床特征相似。认为火山盆地内铀矿床类型应归属于潜火山岩型矿床,并进而对今后的铀矿勘查工作提出了建议。     

辽宁省本溪县杨家堡子金矿地质特征及成因浅析

本溪县杨家堡子金矿赋存于早古生代奥陶系马家沟组及寒武系凤山组内,矿体主要围岩为变质程度轻微的碎屑沉积岩及碳酸盐岩,矿体受断裂构造控制,金矿物及载金矿物——黄(褐)铁矿均呈稀疏浸染状分布,金成矿与燕山期二长花岗岩关系密切,具有"卡林型"金矿床地质特征。认为杨家堡子金矿是与早古生代寒武系、奥陶系地层、岩性、岩相(变质相)、断裂构造及燕山期岩浆活动有成因联系的金矿床,对矿体的矿物组合进行分析,初步确定矿化成因应属低温热液型金矿床。     

新疆伊犁盆地砂岩型铀矿床层间氧化带中粘土矿物特征及与铀矿化关系研究

新疆伊犁盆地砂岩型铀矿床,由于规模大、成矿环境和成矿条件好,在同类型矿床中具有良好的代表性,研究矿床的成矿作用对今后找矿勘查以及开采具有重要理论意义。本文在区域赋铀层位沉积环境研究基础上,以赋矿围岩为研究主体,对伊犁盆地典型铀矿床沉积序列和矿床的控矿层位开展研究,通过对赋矿沉积层位中粘土质对铀矿成矿的控制作用及与铀矿的空间联系和成因分析,开展系统的铀矿床学、能谱测试、显微结构、扫描电镜、地球化学、氢氧同位素等研究,特别是开展了富矿砂体中粘土矿物的种类、成分、结构、同位素、成因等的研究,对粘土质矿物对铀矿成矿的控制作用进行了系统研究。通过研究粘土矿物在伊犁盆地蒙其古尔砂岩型铀矿床成矿过程中的作用及与铀矿的空间联系和成因分析表明:粘土矿物在层间氧化带中分布较为广泛,在主要矿体的氧化还原过渡带中,尤其是部分具有强烈粘土蚀变的砂岩层中铀含量较其他层位要高,反映出粘土矿物与铀成矿是有成因关联的。通过系统的扫描电镜、能谱测试研究,从微观证明粘土矿物与铀成矿有相关关系;粘土矿物的存在导致在近地表含氧含铀水在经过砂岩孔隙时被具有较强吸附能力和巨大表面自由能的粘土矿物所吸附,形成了铀含量较高的片状,团块状的粘土矿物,其在铀成矿作用中起到了吸附和界面的作用,有利于赋矿空间的形成及定位。结合沉积作用、构造活动和后期流体成矿作用等因素,分析了成矿机制和成矿作用,赋矿层位中的粘土矿物、其它成矿条件如岩性(赋矿层和矿源层)、构造(对铀矿化的动力和对地下水径流及铀矿体)等共同控制了铀成矿作用。     

成矿区三维可视化与立体定量预测——以钦-杭成矿带庞西垌地区下园垌铅锌矿区为例

矿产资源是人类生存与社会进步的根本物质保障。近年来,随着地表矿、浅部矿产资源的日益枯竭,采用新技术、新方法的深部矿产资源预测成为地质勘查的主要研究方向。基于数字化、三维可视化及矿产定量预测为主的三维地质建模技术,为当前矿产资源远景预测与找矿工作提供了有力的工具。本文在现代成矿预测理论研究基础上,运用三维地质建模技术建立了钦杭成矿带下园垌矿区地质、地球物理、地球化学、钻孔等三维模型,揭示了区内构造地质特征、地球化学异常表征及地层岩体要素,据此探讨了矿床的成因及矿体分布特征。并在此基础上,采用证据权方法对研究区地质、地球物理、地球化学等多源信息进行融合,运用断裂缓冲区、地球化学异常、东岗岭组沉积岩地层等为证据因子来计算单位体积成矿后验概率,进行立体成矿预测,并圈定出铁锰矿、方铅闪锌矿、铅锌银综合矿等3处找矿有利靶区及估算出预测区内矿产资源储量总量为88710吨。研究结果表明:综合分析地质、地球物理、地球化学及钻孔数据进行矿区的三维地质空间定位、定量预测研究,可以有效的识别矿致异常信息,圈定找矿远景区,为成矿预测研究领域提供了新方向,可以将此方法应用至其他矿山。     

贵州三穗铀矿床矿石矿物学特征及其对找矿的指示

三穗铀矿床位于黔中—湘西北铀成矿带内,产于震旦—寒武系老堡组炭质泥岩中,是贵州省近年勘查发现的第一个大型铀矿床。[研究目的]鉴于黔东地区铀矿成矿规律、富集机理及矿石矿物学等研究程度低,查明典型铀矿床矿石矿物组合及化学组分,探讨成矿环境,揭示成矿过程,深化成矿理论认识,将为促进区域成矿预测、扩大找矿勘查成果及丰富该类型铀矿成矿理论提供科学依据。[研究方法]基于三穗铀矿床地质、地球化学特征,通过电子探针、扫描电镜等测试,分析了铀成矿机理及成岩成矿的环境演化。[研究结果]本区含铀岩系老堡组形成于震旦纪/寒武纪转折期的陆缘裂谷和陆缘裂陷缺氧还原环境,铀成矿初始物源与海底火山活动有关;铀矿石主要由铀矿物、铁矿物、黏土矿物、有机质及白云石、石英（或玉髓）、重晶石、方解石等组成,呈微晶—隐晶结构、微晶—粉晶晶粒状结构,层状、纹层状构造;铀矿物丰富,主要有沥青铀矿、硅钙铀矿、硒铅铀矿、钛铀矿、磷铀矿及水碳铀等,以纳米—微米级粒状、柱状（粒径多<10 μm）、细脉状、或隐晶质形式赋存于有机质、铁质、黏土矿物等聚铀矿物中。[结论]三穗铀矿床形成物源具有多源性,与雪峰期海底火山作用带来部分成矿物质、燕山—喜马拉雅期成矿流体在运移的途中不断浸取地层内的成矿物质密切相关,经历了铀初始富集、氧化淋滤及热液叠加再富集过程,成因属典型的碳硅泥岩型。三穗铀矿床中发现大量铀矿物显示,铀富集程度高、成矿作用强,找矿远景好、潜力大。创新点：基于三穗铀矿床地质地球化学特征,通过电子探针、扫描电镜等矿物学研究,揭示本区铀成岩成矿的环境演化及成矿机理,探讨了找矿远景。     

Iron redistribution during postore stage at uranium deposits of the Khiagda ore field,Vitim district

The localization conditions of mineralization at uranium deposits of the Khiagda ore field related to the economic sandstone type in paleovalleys are considered in this paper. These conditions allow different genetic treatments. Uncertainty in genetic estimates is caused by localization of orebodies in both gray sedimentary rocks at the boundary with bleached rocks and in the bleached rocks themselves. The results of mineralogical and geochemical studies have shown that bleaching is related to iron redistribution at the postore stage. Obvious evidence in favor of this conclusion has been obtained from statistical processing of quantitative soluble iron determinations in various geochemical types of host rocks. The postore bleaching is superposed on earlier oxidized and ore-bearing gray rocks, obliterating the coloration inherent to redox ore-controlling zoning.     

辽东地区太古宙绿岩带铁-铀型铀矿及其找矿前景

简叙辽东地区太古宙绿岩带地质背景,并结合太古宙绿岩带铁-铀型铀矿成矿地质特征的阐述,提出太古宙绿岩带铀成矿作用具有明显的前寒武纪主期性。讨论太古宙富铀钾质花岗岩相关的太古宙残留体内构造-蚀变岩控制铀矿的观点：提出古韧性剪切-破碎断裂带、太古宙基底岩体顶上凸起带之凹洼中的＂突触＂与碱交代岩等三位一体的构造空间和构造-蚀变岩定位层间-不整合破裂带关联-碱交代热液型铀矿的成矿模式,并且太古宙绿岩带铁-铀型铀矿围岩蚀变清楚,铀成矿谱系反映为初贫后富-叠加再造成矿的矿物组合;以复杂-叠加、脉络清楚的太古宙绿岩带构造环境相关的铀矿聚集区为例,探讨太古宙绿岩带铀成矿作用的多期性。并认为太古宙绿岩带铁-铀型铀矿矿体埋藏深、隐伏性强、盲矿体多,潜在的找矿前景相当可观。     

广西大厂锡矿成因研究综述

从矿床的地质、地球化学特征出发,同时又兼顾大厂超大型矿床形成的长期性及多阶段性,认为大厂锡矿是热水沉积－叠生矿床,早期是泥盆纪的热水同生沉积成矿作用,晚期是燕山期花岗岩浆热液成矿作用,该矿是热水沉积成矿作用与岩热液成矿作用叠加成矿的产物。     

The role of the thermal convection of fluids in the formation of unconformity-type uranium deposits: the Athabasca Basin,Canada

In the global production of uranium, ~18% belong to the unconformity-type Canadian deposits localized in the Athabasca Basin. These deposits, which are unique in terms of their ore quality, were primarily studied by Canadian and French scientists. They have elaborated the diagenetic–hydrothermal hypothesis of ore formation, which suggests that (1) the deposits were formed within a sedimentary basin near an unconformity surface dividing the folded Archean–Proterozoic metamorphic basement and a gently dipping sedimentary cover, which is not affected by metamorphism; (2) the spatial accommodation of the deposits is controlled by the rejuvenated faults in the basement at their exit into the overlying sedimentary sequence; the ore bodies are localized above and below the unconformity surface; (3) the occurrence of graphite-bearing rocks is an important factor in controlling the local structural mineralization; (4) the ore bodies are the products of uranium precipitation on a reducing barrier. The mechanism that drives the circulation of ore-forming hydrothermal solutions has remained one of the main unclear questions in the general genetic concept. The ore was deposited above the surface of the unconformity due to the upflow discharge of the solution from the fault zones into the overlying conglomerate and sandstone. The ore formation below this surface is a result of the downflow migration of the solutions along the fault zones from sandstone into the basement rocks. A thermal convective system with the conjugated convection cells in the basement and sedimentary fill of the basin may be a possible explanation of why the hydrotherms circulate in the opposite directions. The results of our computations in the model setting of the free thermal convection of fluids are consistent with the conceptual reasoning about the conditions of the formation of unique uranium deposits in the Athabasca Basin. The calculated rates of the focused solution circulation through the fault zones in the upflow and downflow branches of a convection cell allow us to evaluate the time of ore formation up to the first hundreds of thousands years.     

南岭成矿带铀矿地质特征、成矿规律与全位成矿模式

南岭成矿带是中国重要的铀矿基地,产出的铀矿床以花岗岩型为主,其次为碳硅泥岩型和少量砂岩型。本文通过搜集整理前人找矿勘查和科研成果,认为南岭成矿带多期多阶段构造演化为铀成矿作用提供了初始铀源、产铀花岗岩、断裂网络和含铀热液等有利的成矿条件。产铀花岗岩大多是由高硅、过铝、偏钾高碱的S型花岗岩,沿断裂分布的构造碎裂岩、蚀变岩和还原性地质体是有利的赋矿围岩。矿化与蚀变中心带发育沥青铀矿、黑色微晶玉髓、紫黑色萤石、胶状黄铁矿、赤铁矿、绿泥石等矿物组合。铀矿体形态多样,以中小规模、中低工业品位为主。南岭成矿带中新生代多阶段区域性拉张过程中形成了多阶段铀矿化。花岗岩型铀矿床分布于加里东隆起区花岗岩内部构造结和岩体接触带附近,矿体沿断裂与蚀变体一起赋存于氧化-还原界面和脆韧性构造转换面之间的"成矿壳层"内。南岭成矿带中新生代"空间全位"铀成矿模式显示,不同的构造层、不同的建造、不同的岩性及不同的部位均有铀成矿潜力,但由于具体成矿条件的不同组合而产出不同类型、不同规模、不同时间和不同强度的铀矿化。也就是说,难以排除某一空间部位不成矿的可能性。根据这一"全位"成矿的认识,从不同的角度对南岭成矿带中新生代铀成矿作用进行全面分析,找出尚未落实的"缺位",再根据工作区具体成矿条件指导铀矿找矿新突破。     

重砂找矿中的地球化学方法

重矿物除了作矿物鉴定以外,还可进行单矿物的微量元素测定,给地球化学勘查提供有用的信息,使化探采样的对象扩大到重矿物领域。重砂矿物中除了主要元素外,还含有多种杂质元素,这些杂质元素的种类、含量高低及元素间的比值变化,是受矿物生成时的地质环境制约的。据此可以知道矿物生成时的温度、岩石和矿床的类型以及岩体的含矿性。本文综述了十几种重砂矿物中微量元素的变化与地质,岩石和矿床的关系,及用于地球化学找矿的可能性。     

砂岩型铀矿中铀矿物U-Pb年代学研究现状及研究方向

该文基于中国地质调查局天津地质调查中心研究团队近年来的研究工作及对相关文献的综合研究,对砂岩型铀矿中一些重要铀矿物如沥青铀矿(晶质铀矿)、铀石、钛铀矿等的微区原位成因矿物学和U-Pb年代学研究现状进行了深入分析,提出新的研究方向,即通过采用二次离子质谱法、激光剥蚀多接收器电感耦合等离子体质谱法与电子探针化学分析法和同位素稀释热电离质谱法相结合的方式,综合研究砂岩型铀矿中沥青铀矿(晶质铀矿)、铀石、钛铀矿等铀矿物和金红石、磷灰石等含铀矿物的微区原位成因矿物学和U-Pb年代学,探索砂岩型铀矿中矿石矿物的U-Pb同位素测年新方法,获取更精确的砂岩型铀矿成岩成矿的年代学信息。这对于全面准确地认识砂岩型铀矿床的生成和演化历史,建立砂岩型铀矿床的成矿新理论具有十分重要的科学意义。铀矿物测年新方法在砂岩型铀矿床的地质勘探中也有广阔的应用前景。     

Formation conditions of paleovalley uranium deposits hosted in upper Eocene–lower Oligocene rocks of Bulgaria

The uranium deposits of Bulgaria related to the Late Alpine tectonomagmatic reactivation are subdivided into two groups: exogenic–epigenetic paleovalley deposits related to the basins filled with upper Eocene–lower Oligocene volcanic–sedimentary rocks and the hydrothermal deposits hosted in the coeval depressions. The geological and lithofacies conditions of their localization, the epigenetic alteration of rocks, mineralogy and geochemistry of uranium ore are exemplified in thoroughly studied paleovalley deposits of the Maritsa ore district. Argumentation of the genetic concepts providing insights into both sedimentation–diagenetic and exogenic–epigenetic mineralization with development of stratal oxidation zones is discussed. A new exfiltration model has been proposed to explain the origin of the aforementioned deposits on the basis of additional analysis with consideration of archival factual data and possible causes of specific ningyoite uranium ore composition.     

A catastrophe mathematical model for uranium mineralization of hot-water origin

Presented in this paper are some primary data on the temperature, stratigraphical altitude and thickness of a certain uranium ore deposit. Taking these data as the parameters for the temperature, pressure and geochemical conditions of uranium mineralization under ideal geological conditions which constitute a finite variable series, in conjunction with the catastrophe theory developed by Rene Thom (1968), we have proposed a swallow-tail model fit to uranium mineralization. This model provides insight into the mechanism of uranium mineralization. Our study shows that the process of uranium mineralization is a discontinuous or catastrophic event. Temperature and pressure are considered important thermodynamic conditions which control the distribution pattern of uranium mineralization, and the principle of temperature-pressure correspondence for uranium mineralization has been also derived. Geological bodies of minerogenetic importance serve as favourable geochemical media for capturing ore-forming materials. Uranium mineralization of commercial importance depends on a delicate coupling between temperature,pressure, and geochemical condition. The loci of uranium mineralization in the model constitute the surfaceK, referred to as the surface of enrichment-mineralization, on which minerogenetic domain is expected. The model provides quantitatively clues to the process of uranium mineralization, i.e., a process from quantitative to qualitative changes.     

Carbonatitic Volcanic Genesis of Hetaoqing Fe-Cu Deposit in Central Yunnan, China

Abstract. The Kunyang rift on western margin of Yangtze Platform is a continental rift, and also a rare Precambrian Fe-Cu mineralization zone in China. The Wuding-Lufeng mineralization area in the middle section of the rift is an important part of the zone, and an elliptic-shaped volcanic collapsed basin, controlled by a ring fracture system with carbonatitic volcanic rocks mainly occurring along the northwestern edge of the basin. The Hetaoqing Fe-Cu ore deposit at the western side of the basin is hosted in carbonatitic volcanic rocks and pyroclastic sedimentary rocks. The original ore bodies occur as layers, bands and lenses conformable to the host carbonatitic rocks. The ores usually appear as massive, impregnated and granular in carbonatitic rocks, and as brecciform and sandy in pyroclastic sedimentary rocks. Ore-forming minerals are magnetite, hematite, chalcopy-rite, bornite, pyrite, carrollite, molybdenite, cobaltite and skinnerite, and secondary minerals limonite, chalcocite, azurite, malachite and tenorite. Gangue minerals are calcite, dolomite, ankerite, common hornblende, arfvedsonite, augite, aegirine-augite, albite, phlogopite, biotite, chlorite and apatite. Evidences of mineral chemistry, trace elements and isotopic ratios of ores, as well as geological features, suggest that the original ores are igneous in origin. Chemical features of magnetites in the deposit belong to carbonatite type, and are similar to those from the Bayan Obo carbonatites. The ores are rich in iron, titanium, rare earth elements, niobium, tantalum, gold, silver, phosphor and sulfur. These features indicate that the Fe-Cu deposit associated with volcanic activity in the Wuding-Lufeng basin is alkali-carbonatite volcanic type.     

湖南省成矿地质事件纲要

[研究目的]湖南省矿产资源丰富,矿种及成因类型繁多,但对各类矿产形成的时代和构造背景尚缺乏系统归纳和总结.[研究方法]本文在既有区域矿产资料基础上,结合近些年区域构造演化、成岩成矿年龄、矿床成因机制等研究成果,对湖南省成矿地质事件及各期成矿事件的构造背景、矿床成因、矿产发育和分布特征等进行了系统探讨和总结.[研究结果]...     

甘肃阿尔金南缘白石头沟石墨矿地质特征、成矿条件及找矿标志

甘肃白石头沟石墨矿位于阿尔金南缘敦煌地块,赋存于前寒武纪敦煌岩群大理岩和石英片岩之中,目前圈定矿体33条,主要矿体2条。作为研究白石头沟石墨矿理想地层的敦煌岩群,是一套以变质碎屑沉积岩和变质基性岩为主的变质岩浆杂岩。本文从矿床角度出发,立足于区域地质勘查资料,结合前人研究成果,在对白石头沟石墨矿成矿地质背景、矿床及矿体特征、组合样化学分析、矿石矿物赋存状态及特征研究的基础上,对矿床的成因进行初步探讨并归纳区域找矿标志。研究表明,白石头沟石墨矿可分为大理岩型和石英片岩型两种类型,是古元古代经历区域动力热液变质作用而形成的沉积变质型矿床,成矿物质主要来源于变质碎屑沉积岩类的原岩（海相陆源碎屑岩和碳酸盐岩）本身,成矿环境为古老活动大陆边缘。找矿标志具有特定层位、岩性、矿化及物探特征。     

西藏纳木错—嘉黎断裂带铜多金属矿化特征及找矿模型

西藏纳木错—嘉黎断裂带是狮泉河-申扎-嘉黎结合带的重要组成部分,该断裂带为区内的控岩控界断裂,具有规模大、切割深的特点,是西藏念青唐古拉山地区铜多金属成矿的重要导矿构造.断裂带西起纳木错,东至嘉黎县城以东,全长320km以上,沿该带及两侧分布有大量地化异常及大、中型矿床(点).通过对区内地、物、化、遥资料的综合研究,分...