低温低压下沥青铀矿合成实验研究

前言在研究某地碳硅泥岩型铀矿地质特征和矿床成因过程中,重点研究了该矿床沥青铀矿形成的物理化学环境,并在实验室内模拟了沥青铀矿形成的主要条件。从我们调研的材料看出,早在四十年代美国原子能委员会(AEC)下设的科研机构就已做过沥青铀矿合成实验,苏联至五十年代末还发表过合成沥青铀矿的有关文章。然而就我们所知,前人的合成实验大多在高温高压下进行,也有人如 J.W.格鲁纳(1954年)提到了曾在     

黄铁矿与沥青铀矿的共生条件及在沥青铀矿形成过程中所起作用的实验研究

高价铁与高价铀混合溶液在还原场中形成了共生的黄铁矿与沥青铀矿,该过程必须在弱酸性-中性-碱性介质中进行,其中在弱酸性至中性介质中易形成大的黄铁矿单晶。高价铀溶液流经黄铁矿矿区时,若在高温高压条件下,有新生的黄铁矿或白铁矿与沥青铀矿共生。黄铁矿还原六价铀形成沥青铀矿时,起还原作用的是二价硫。赤铁矿常与沥青铀矿共生,但它们是热液演化过程中不同阶段的产物,赤铁矿形成于体系氧逸度高的氧化环境,沥青铀矿形成于体系氧逸度低的还原环境,赤铁矿形成于沥青铀矿之前。     

新疆萨瓦莆齐铀矿床沥青还原沥青铀矿的直接证据

许多含油气盆地均有铀矿床分布,油气在铀矿化中的作用及其与铀矿化的关系是广大铀矿工作者关注的问题。通过对新疆萨瓦莆齐铀矿床中铀矿石的偏光、荧光反射显微镜研究和电子探针分析测试,首次在矿石中发现沥青-沥青铀矿-黄铁矿脉,对脉体中沥青、沥青铀矿、黄铁矿的空间关系研究表明,沥青铀矿和黄铁矿均受沥青脉的控制,是脉体中还原能力较强的轻烃类物质与周围环境相互作用的产物,矿物中的铀和铁元素主要来自周围环境而非脉体本身。矿床可能存在多期油气活动,沥青铀矿可能主要形成于早期油气活动,晚期油气衍生的沥青质沿早期生成的沥青铀矿微裂隙充填改造。     

二连盆地与地沥青密切相关的砂岩型铀矿床微观矿物特征及成因分析

内蒙古二连盆地产在下白垩统碎屑岩系中的砂岩型铀矿床,其矿化与地沥青密切相关,有铀矿物存在之处必有地沥青;岩石中也普遍含地沥青。笔者通过蚀刻α径迹示踪,对铀含量在(200~1770)×10~(-6)的碎屑岩进行扫描电镜分析,采用分子量计算方法确定了该地区含铀碎屑岩中的铀是以多种超显微铀矿物形式存在。其中,以赛汉高毕铀矿床为代表,铀主要形成复成分磷钙铀矿。其它铀矿床也普遍有复成分磷钙铀矿产出:巴彦乌拉矿床样品因钙含量低、硅含量高,则铀石多于复成分磷钙铀矿;道尔苏矿床以铀石和磷铀矿为主,有少量沥青铀矿及复成分磷钙铀矿;哈达图矿床主要是沥青铀矿,未见复成分磷钙铀矿。除了地沥青之外,各矿床中与铀矿物共生的主要矿物还有草莓状、鲕粒状黄铁矿。由此推断,铀矿床的可能成因是:来自盆地深部的UH_3、PH_3、CaH_2、SiH_4、FeH_2、H_2S等在伴随油气向上运移过程中,由于温度、压力降低和氧化作用而发生分解及凝聚,形成草莓状、鲕粒状黄铁矿;同时派生出含U、P、Si、Ca等的氧化物的低温热水溶液,并最终结晶析出铀矿物,形成有大量黄铁矿共生的铀矿体;而油气经过长期挥发,最终演变成地沥青,成为铀矿物的载体。     

伊犁蒙其古尔铀矿床含矿层砂岩中黄铁矿形成机制及对铀成矿的指示意义

蒙其古尔铀矿床为伊犁盆地南缘大型层间氧化带砂岩型铀矿床,为查明该矿床含矿层中黄铁矿成因及其形成机制,探讨微生物参与铀成矿过程。文章对含矿层砂岩中黄铁矿与铀矿物矿物学特征、黄铁矿S同位素与碳酸盐胶结物的C-O同位素开展细致研究。研究表明:①蒙其古尔铀矿床中铀主要以铀矿物与吸附铀形式存在,吸附铀主要为有机质吸附铀,铀矿物以沥青铀矿为主,多与黄铁矿、炭屑共生;②蒙其古尔铀矿床含矿层砂岩中黄铁矿主要以自形晶、草莓状和不规则状集合体产出,多与沥青铀矿、碳酸盐胶结物共生,其中黄铁矿S同位素(δ~(34)S_(V-CDT)=-68.4‰～22.1‰)与碳酸盐胶结物的C-O同位素(δ~(13)C_(V-PDB)=-10.2‰～-7.4‰,δ~(18)O_(V-PDB)=-9.6‰～-5.8‰)分析表明黄铁矿具有细菌硫酸盐还原(BSR)与有机物热解2种成因,并探讨了这2种不同成因黄铁矿的形成机制。③结合前人研究成果,认为硫酸盐还原菌(SRB)参与蒙其古尔铀矿床铀成矿过程,以间接还原方式为主,在有机质、黏土矿物与颗粒表面吸附U(Ⅵ)的基础上,通过硫酸盐还原菌(SRB)还原SO_4~(2-)产生的H_2S将U(Ⅵ)被还原成U(Ⅳ),形成铀矿物。     

开鲁盆地砂岩型铀矿中黄铁矿与铀矿化成因关系探讨

开鲁盆地位于松辽盆地西南部,是中国北方砂岩型铀矿勘查的重点地区,自钱家店铀矿床发现以来,盆地内上白垩统姚家组目的层中相继发现了一些具有工业价值的铀矿床.为查明该层位中黄铁矿成因及其形成机制,探讨其与铀矿化之间的关系,本研究对含矿层砂岩中黄铁矿与铀矿物矿物学特征、黄铁矿S同位素开展细致研究.研究表明:(1)开鲁盆地姚家组砂岩中铀主要以独立铀矿物及吸附铀形式存在,独立铀矿物以沥青铀矿为主,含少量的钛铀矿及部分铀石,多数沿黄铁矿周边生长.吸附态的铀与黏土矿物密切相关.(2)姚家组砂岩中黄铁矿主要以草莓状、胶状及粒状产出,多与沥青铀矿共生,其中黄铁矿S同位素(d34S=–55.6‰～23.2‰),平均值–20.87‰,变化范围很大,说明硫的分馏程度较高,硫的来源范围较广.(3)分析表明黄铁矿具有细菌硫酸盐还原作用及热化学硫酸盐还原作用两种成因,并探讨了这2种成因黄铁矿的形成机制.综合前人研究,结合研究区成矿地质背景,认为黄铁矿为铀成矿作用提供了发生还原反应所需要的还原剂,且黄铁矿及铀矿物的形成与区内热流体存在紧密联系.     

铀的微生物Desulfovibrio desulfuricans DSM 642成矿作用:模拟实验及其意义

在我国首次报道用硫酸盐还原菌 Desulf ovibriodesulfuricans DSM 6 4 2 ,模拟我国层间氧化带砂岩型铀矿形成的主要物理化学条件 (35℃ ,p H=7.0～ 7.4 ) ,实验还原U( )和合成沥青铀矿。结果表明 ,实验经一周后 ,微生物成因沥青铀矿即生成于该菌胞表面。由此推断 ,在侏罗系砂岩中广泛繁衍的这种硫酸盐还原菌 ,可能参与了该类铀矿床的成矿作用。同时发现 ,由该实验菌实验还原生成的沥青铀矿 ,与在天然地质条件下生成的该铀矿物 ,其晶体结构的有序—无序性质存在重大差异 :在天然条件下藉长期和缓慢地沉淀、生长形成的沥青铀矿 ,其中纳米级…     

八面体晶质铀矿的人工合成实验研究

介绍了人工合成八面体晶质铀矿的实验成果,并对合成的晶质铀矿样品进行了矿物学研究,获取了重要数据:合成的晶质铀矿样品最大颗粒为2.5mm×3.5mm,黑色到乌黑色,沥青光泽到半金属光泽,密度为8.87~9.12g/cm3,反射光下为灰白色。实验表明,有利于晶质铀矿生长的条件是:强还原场、温度450℃、压力120 MPa、强酸性(pH4)、稀溶液(铀含量小于23.8mg/mL)。     

17—115℃沥青铀矿的合成及其形成速度的实验研究

本文介绍了17—115℃沥青铀矿合成的方法及对产品的鉴定结果。实验是在只有六价铀与硫代乙酰胺存在的非常简单的体系中进行的。合成的最低温度为17℃。沥青铀矿的结晶速度在不同的温度和pH条件下是不同的。温度越高,结晶速度越快。在酸性溶液中沥青铀矿结晶速度快,中性中较慢,碱性中最慢。但随着温度的提高,酸、中、碱性溶液结晶速度的差值迅速缩小。82℃时,无论酸、中、碱性溶液中的沥青铀矿均能在半小时内结晶出来。     

热液型铀成矿氧化还原条件研究：来自特征矿物的指示

通过对典型热液型铀矿床铀-赤铁矿型、铀-黄铁矿型铀矿石矿物组合特征、时空分布特征的研究,探讨了热液型铀成矿的氧化还原条件。相山矿田碱交代成因的铀-赤铁矿型矿石矿物组合为沥青铀矿-赤铁矿-钠长石-磷灰石-碳酸盐;长江矿田酸交代成因的铀-赤铁矿型矿石矿物组合为沥青铀矿-赤铁矿-微晶石英。铀-黄铁矿型矿石矿物组合为沥青铀矿-黄铁矿-微晶石英-萤石。铀-赤铁矿型较铀-黄铁矿型形成早,两种类型铀矿石在矿田深部及浅部均有大量富集,垂向上呈现相互叠置的分布特征。沥青铀矿形成并能稳定存在的氧化还原条件为黄铁矿至黄铁矿与赤铁矿共存区,黄铁矿存在有利于沥青铀矿富集,完全的赤铁矿区不利于沥青铀矿的形成及保存。     

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.     

Biomineralization of Uranium: A Simulated Experiment and Its Significance

A simulated experimental reduction of U^v1 and the synthesis of uraninite by a sulfate-reducing bacteria,Desulfovibrio desulfuricans DSM 642, are first reported. The simulated physicochemical experimental conditions were:35℃, pH=7.0-7.4, corresponding to the environments of formation of the sandstone-hosted interlayer oxidation-zone type uranium deposits in Xinjiang, NW China. Uraninite was formed on the surface of the host bacteria after a one-week‘s incubation. Therefore, sulfate-reducing bacteria, which existed extensively in Jurassic sandstone-producing environments,might have participated in the biomineralization of this uranium deposit. There is an important difference in the orderdisorder of the crystalline structure between the uraninite produced by Desulfovibrio desulfuricans and naturally occurring uraninite. Long time and slow precipitation and growth of uraninite in the geological environment might have resulted in larger uraninite crystals, with uraninite nanocrystals arranged in order, whereas the experimentally produced uraninite is composed of unordered uraninite nanocrystals which, in contrast, result from the short time span of formation and rapid precipitation and growth of uraninite. The discovery has important implications for understanding genetic significance in mineralogy, and also indicates that in-situ bioremediation of U-contaminated environments and use of biotechnology in the treatment of radioactive liquid waste is being contemplated.     

Uraniferous bitumen nodules in the Talvivaara Ni–Zn–Cu–Co deposit (Finland): influence of metamorphism on uranium mineralization in black shales

In the central part of the Fennoscandian Shield, the Talvivaara Ni–Zn–Cu–Co deposit, hosted by Palaeoproterozoic metamorphosed black schists, contains low uranium concentrations ranging from 10 to 30 ppm. The Talvivaara black schists were deposited 2.0–1.9 Ga ago and underwent subsequent metamorphism during the 1.9–1.79 Ga Svecofennian orogeny. Anhedral uraninite crystals rimmed by bitumen constitute the main host of uranium. U–Pb secondary ion mass spectrometry dating indicates that uraninite crystals were formed between 1,878?±?17 and 1,871?±?43 Ma, during peak metamorphism. Rare earth element patterns and high Th content (average 6.38 wt%) in disseminated uraninite crystals indicate that U was concentrated during high temperature metamorphism (>400 °C). The formation of bitumen rims around uraninite may be explained by two distinct scenarios: (a) a transport of U coincident with the migration of hydrocarbons or (b) post-metamorphic formation of bitumen rims, through radiolytic polymerization of gaseous hydrocarbons at the contact with uraninite.     

Uraninite recrystallization and Pb loss in the Oklo and Bangombé natural fission reactors, Gabon

The Oklo and Bangombé natural fossil fission reactors formed ca. 2 Ga ago in the Franceville basin, Gabon. The response of uraninite in the natural reactors to different geological conditions has implications for the disposal of the UO₂ in spent nuclear fuel. Uraninite and galena from two reactor zones, RZ16 at Oklo and RZB at Bangombé, were studied to clarify the chronology and effect of alteration events on the reactor zones. In addition, ion microprobe U-Pb analysis of zircons from a dolerite dyke in the Oklo deposit were completed to better constrain the age of the dyke, and thereby testing the link between the dyke and an important alteration event in the reactor zones.The analyzed uraninite from RZ16 and RZB contains ca. 6 wt% PbO, indicating a substantial loss of radiogenic Pb. Transmission electron microscopy showed that microscopic uraninite grains in the reactor zones consist of mainly defect-free nanocrystalline to microcrystalline aggregates. However, the nanocrystalline regions have elevated Si contents and lower Pb contents than coarser uraninite crystallites. Single stage model ages of large, millimeter-sized galena grains at both RZ16 and RZB correlate well with the age of the Oklo dolerite dyke, 860 ± 39 Ma (2σ). Thus, the first major Pb loss from uraninite occurred at both Oklo and Bangombé during regional extension and the intrusion of a dyke swarm in the Franceville basin, ∼860-890 Ma ago. Uraninite Pb isotopes from RZ16 and RZB give lower ages of ca. 500 Ma. These ages agree with the “chemical” ages of the uraninite, and show that an ancient Pb loss occurred after the intrusion of the dolerite dykes. The presence of nanocrystallites in the reactor uraninite indicates internal recrystallization, which may have occurred around 500 Ma, resulting in the 6wt% PbO uraninite. It is suggested that leaching by fluid interaction triggered by the Pan-African orogeny was important during this second Pb-loss event. Thus, there are indications that uraninite at both the Oklo and Bangombé natural reactors has experienced at least two ancient episodes of Pb loss associated with internal recrystallization. These recrystallization events have occurred without significantly depleting the 2 Ga fission products compatible with the uraninite structure.     

电子探针化学测年在攀枝花大田晶质铀矿中的应用及其意义

晶质铀矿和沥青铀矿是热液铀矿床的主要工业铀矿物,在研究热液铀矿床成因及成矿规律方面具有重要的意义。攀枝花大田地区是我国混合岩型热液铀矿分布区,已发现粗粒特富铀矿滚石(铀含量10%)及较富基岩矿石(铀含量为0.1%~2%),主要铀矿物为晶质铀矿,对两种晶质铀矿成分及形成时代的研究对该区混合岩型热液铀矿成矿规律研究具有重要的价值。本文通过对大田地区滚石中的晶质铀矿和基岩矿石中的晶质铀矿进行矿物学及电子探针分析,研究了晶质铀矿的成分及形成时代。结果表明:(1)大田地区滚石和基岩矿石中的晶质铀矿除铅之外化学成分较为相似,两类矿石晶质铀矿中UO_2含量为77.36%~84.04%,ThO_2含量为0.98%~5.59%,PbO含量为1.79%~8.8%,其中滚石晶质铀矿中的铅含量低于基岩晶质铀矿,钍含量高于基岩晶质铀矿;(2)电子探针化学定年结果表明,基岩矿石晶质铀矿的形成时代为774.9~785.5 Ma,滚石晶质铀矿的形成时代为783.7 Ma,与传统同位素测年结果(775~777.6 Ma)非常一致,一方面说明滚石晶质铀矿和基岩晶质铀矿为同一时代的产物,另一方面说明电子探针原位测年方法是可靠的;(3)在后期的热液蚀变中,晶质铀矿先后发生了硅化、碳酸盐化及赤铁矿化,蚀变发生的时间分别为730.6Ma、699.8 Ma和664.0 Ma。此结论对研究攀枝花大田地区热液铀矿成矿时代及成矿作用过程提供了依据。     

Characterization of uraninite nanoparticles produced by Shewanella oneidensis MR-1

The reduction of uranium(VI) by Shewanella oneidensis MR-1 was studied to examine the effects of bioreduction kinetics and background electrolyte on the physical properties and reactivity to re-oxidation of the biogenic uraninite, UO_2(s). Bioreduction experiments were conducted with uranyl acetate as the electron acceptor and sodium lactate as the electron donor under resting cell conditions in a 30 mM NaHCO₃ buffer, and in a PIPES-buffered artificial groundwater (PBAGW). MR-1 was cultured in batch mode in a defined minimal medium with a specified air-to-medium volume ratio such that electron acceptor (O₂) limiting conditions were reached just when cells were harvested for subsequent experiments. The rate of U(VI) bioreduction was manipulated by varying the cell density and the incubation temperature (1.0 × 10⁸ cell ml⁻¹ at 20 °C or 2.0 × 10⁸ cell ml⁻¹ at 37 °C) to generate U(IV) solids at “fast” and “slow” rates in the two different buffers. The presence of Ca in PBAGW buffer altered U(VI) speciation and solubility, and significantly decreased U(VI) bioreduction kinetics. High resolution transmission electron microscopy was used to measure uraninite particle size distributions produced under the four different conditions. The most common primary particle size was 2.9-3.0 nm regardless of U(VI) bioreduction rate or background electrolyte. Extended X-ray absorption fine-structure spectroscopy was also used to estimate uraninite particle size and was consistent with TEM results. The reactivity of the biogenic uraninite products with dissolved oxygen was tested, and neither U(VI) bioreduction rate nor background electrolyte had any statistical effect on oxidation rates. With MR-1, uraninite particle size was not controlled by the bioreduction rate of U(VI) or the background electrolyte. These results for MR-1, where U(VI) bioreduction rate had no discernible effect on uraninite particle size or oxidation rate, contrast with our recent research with Shewanella putrefaciens CN32, where U(VI) bioreduction rate strongly influenced both uraninite particle size and oxidation rate. These two studies with Shewanella species can be viewed as consistent if one assumes that particle size controls oxidation rates, so the similar uraninite particle sizes produced by MR-1 regardless of U(VI) bioreduction rate would result in similar oxidation rates. Factors that might explain why U(VI) bioreduction rate was an important control on uraninite particle size for CN32 but not for MR-1 are discussed.     

Fate of trace elements during alteration of uraninite in a hydrothermal vein-type U-deposit from Marshall Pass, Colorado, USA

Alteration of uraninite from a hydrothermal vein-type U-deposit in Marshall Pass, Colorado, has been examined by electron microprobe analysis in order to investigate the release and migration of trace elements W, As, Mo, Zr, Pb, Ba, Ce, Y, Ca, Ti, P, Th, Fe, Si, Al, during alteration, under both reducing and oxidizing conditions. The release of trace elements from uraninite is used to establish constraints on the release of fission product elements from the UO₂ in spent nuclear fuels. Uraninite occurs with two different textures: (1) colloform uraninite and (2) fine-grained uraninite. The colloform uraninite contains 1.04-1.75 wt% of WO₃, 0.16-1.70 wt% of As₂O₃, 0.06-0.88 wt% of MoO₃; whereas, the fine-grained uraninite retains 2.25-4.93 wt% of WO₃, up to 5.76 wt% of MoO₃, and 0.26-0.60 wt% of As₂O₃. The near constant concentration of incompatible W in the colloform uraninite suggests W-incorporation into the uraninite structure or homogeneous distribution of W-rich nano-domains. Incorporation of W and Mo into the uraninite and subsequent precipitation of uranyl phases bearing these elements are critically important to understanding the release and migration of Cs during the corrosion of spent nuclear fuel, as there is a strong affinity of Cs with W and Mo. Zoning in the colloform texture is attributed to variation in the amount of impurities in uraninite. For unaltered zones, the calculated amount of oxygen ranges from 2.08 to 2.32 [apfu, (atom per formula unit)] and defines the stoichiometry as UO_2+x and U₄O₉; whereas, for the altered zones of the colloform texture, the oxygen content is 2.37-2.48 [apfu], which is probably due to the inclusion of secondary uranyl phases, mainly schoepite. The supergene alteration resulted in precipitation of secondary uranyl minerals at the expense of uraninite. Four stages of colloform uraninite alteration are proposed: (i) formation of an oxidized layer at the rim, (ii) corrosion of the oxidized layer, (iii) precipitation of U⁶⁺-phases with well-defined cleavage, and (iv) fracture of the uraninite surface along the cleavage planes of the U⁶⁺-phases.     

Age and origin of uranium mineralization in the Camie River deposit (Otish Basin,Québec,Canada)

The Camie River uranium deposit is located in the southeastern part of the Paleoproterozoic Otish Basin (Québec). The uranium mineralization consists of disseminated and vein uraninite and brannerite precipitated close to the unconformity between Paleoproterozoic fluviatile, pervasively altered, sandstones and conglomerates of the Matoush Formation and the underlying sulfide-bearing graphitic schists of the Archean Hippocampe greenstone belt. Diagenetic orange/pink feldspathic alteration of the Matoush Formation consists of authigenic albite cement partly replaced by later orthoclase cement, with the Na₂O content of clastic rocks increasing with depth. Basin-wide green muscovite alteration affected both the Matoush Formation and the top of the basement Tichegami Group. Uraninite with minor brannerite is mainly hosted by subvertical reverse faults in basement graphitic metapelites ± sulfides and overlying sandstones and conglomerates. Uranium mineralization is associated with chlorite veins and alteration with temperatures near 320 °C, that are paragenetically late relative to the diagenetic feldspathic and muscovite alterations. Re-Os geochronology of molybdenite intergrown with uraninite yields an age of 1724.0 ± 4.9 Ma, whereas uraninite yields an identical, although slightly discordant, 1724 ± 29 Ma SIMS U-Pb age. Uraninite has high concentrations in REE with flat REE spectra resembling those of uraninite formed from metamorphic fluids, rather than the bell-shaped patterns typical of unconformity-related uraninite. Paragenesis and geochronology therefore show that the uranium mineralization formed approximately 440 million years after intrusion of the Otish Gabbro dykes and sills at ∼2176 Ma, which constrains the minimum age for the sedimentary host rocks. The post-diagenetic stage of uraninite after feldspathic and muscovite alterations, the paragenetic sequence and the brannerite-uraninite assemblage, the relatively high temperature for the mineralizing event (∼320 °C) following the diagenetic Na- and K-dominated alteration, lack of evidence for brines typical of unconformity-related U deposits, the older age of the Otish Basin compared to worldwide basins hosting unconformity-related uranium deposits, the large age difference between basin fill and mineralization, the older age of the uranium oxide compared to ages for worldwide unconformity-related U deposits, and the flat REE spectra of uraninite do not support the previous interpretation that the Camie River deposit is an unconformity-associated uranium deposit. Rather, the evidence is more consistent with a PaleoProterozoic, higher-temperature hydrothermal event at 1724 Ma, whose origin remains speculative.     

不同温度后红砂岩力学性质及微观结构变化规律试验研究

对20℃、70℃、140℃、200℃、300℃、400℃、600℃、800℃等8种不同温度后红砂岩的力学特性进行了试验研究,结合压汞、SEM扫描电镜微观试验分析不同温度后红砂岩孔隙结构变化及微裂纹产生规律,并对红砂岩的不同温度劣化微观机制作初步探讨。研究表明：（1）不同温度后红砂岩单轴抗压强度在300℃达到峰值为常温的1.4倍;红砂岩劣化阀值温度为600℃,单轴抗压强度降幅达32.5%;（2）不同温度后红砂岩产生的裂纹宽度绝对多数分布在0～0.01 μm区间内,该区间内各阶段裂缝的分布比值与单轴抗压强度呈较好的相关性;（3）沿晶和穿晶裂纹产生以及裂纹均质性变差是红砂岩劣化的主要影响因素。     

晶质铀矿中稀土元素的岩石学意义

本文通过诸广山岩体、黄龙庙岩体的岩石及其中晶质铀矿稀土元素的研究,得出以下几点认识:晶质铀矿中稀土元素的丰度与其源岩的稀土元素丰度呈正消长关系;晶质铀矿中稀土元素的配分特点与源岩的酸性程度有关;晶质铀矿中稀土元素分馏程度反映了源岩的分异演化程度。