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中国北西部地区地浸砂岩型铀矿床的成矿条件与分布规律 总被引：2，自引：0，他引：2
罗梅 《物探化探计算技术》1996,(S5)
中亚地区发现大量可地浸砂岩型铀矿床引起了我国的重视 ,目前正在积极开展此类型铀矿的找矿工作。我国北西部是寻找类似中亚地区层间氧化带后生地浸砂岩型铀矿床最理想的地区 ,本文在论述了区域大地构造特征、地壳演化与区域铀成矿带形成的基础上 ,着重阐明了区域中新生代盆地地浸砂岩型铀矿床形成的铀源条件、盆地类型与结构及富铀性对形成地浸砂岩型铀矿的影响 ;并以区内已有层间氧化带地浸砂岩型铀矿床为例 (伊犁盆地、二连盆地与测老庙盆地砂岩型铀矿床 ) ,论述了盆地砂岩型铀矿床形成的岩相古地理条件、水文地质与层间氧化带发育条件及对铀成矿的影响 ;并阐述了本区层间氧化带地浸砂岩型铀矿床的分布规律 相似文献
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罗梅 《物探化探计算技术》1996,(Z1)
中亚地区发现大量可地浸砂岩型铀矿床引起了我国的重视，目前正在积极开展此类型铀矿的找矿工作。我国北西部是寻找类似中亚地区层间氧化带后生地浸砂岩型铀矿床最理想的地区，本文在论述了区城大地构造特征、地壳演化与区域铀成矿带形成的基础上，着重阐明了区域中新生代盆地地浸砂岩型铀矿床形成的铀源条件、盆地类型与结构及富铀性对形成地浸砂岩型铀矿的影响；并以区内已有层间氧化带地浸砂岩型铀矿床为例（伊犁盆地、二连盆地与测老庙盆地砂岩型铀矿床），论述了盆地砂岩型铀矿床形成的岩相古地理条件、水文地质与层间氧化带发育条件及对铀成矿的影响；并阐述了本区层间氧化带地浸砂岩型铀矿床的分布规律。 相似文献
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目前,世界上业已证实的可地浸砂岩型铀矿床及已实施地浸方法开采的铀矿床(层间氧化带型、古河道型)多为隐伏盲矿,铀矿体的原生晕、次生晕欠发育或不发育,含矿主岩以疏松、充水为特征,地表找矿特征不明显,目前尚没有普遍适用且非常有效的物化探方法用于勘查该类型矿床。因此,在可地浸砂岩型铀矿勘查中,钻探就成为最基本、最主要的工作手段。笔者对世界上十余个著名可地浸砂岩型铀矿床(包括层间氧化带型和古河道型铀矿床)的调研结果表明,钻探工作在可地浸砂岩型铀矿勘查中具有举足轻重的地位(表1)。表1 世界主要可地浸砂岩型铀矿床钻探工作量… 相似文献
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中国北东部中新生代盆地地浸砂岩型铀矿成矿条件及找矿方向 总被引：1，自引：1，他引：0
中国北东部中新生代盆地是地浸砂岩型铀矿的主要勘查区.自1996年开始,为了寻找地浸砂岩型铀矿床,对这些盆地开展了1:500 000-1:200 000铀矿区域地质调查,投入了大量钻探工作量.运用可地浸砂岩型铀矿评价准则,对松辽盆地、海拉尔盆地的成矿地质条件进行分析,提出成矿的有利层位和远景区、段,为该区寻找地浸砂岩型铀矿床提供了科学依据. 相似文献
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可地浸砂岩型铀矿床由于其上覆盖层较厚,地表异常信息十分微弱,找矿难度相当大。本文通过研究新疆伊犁盆地510、511、512等3个已知可地浸砂岩型铀矿床的航磁资料,发现这些矿床上方均存在微航磁异常,根据可地浸砂岩型铀矿的成矿地球化学机制,对微航磁异常的形成机理作了进一步探讨,结合试验区的实际预测成果,指出与氧化还原过渡带有关的可地浸砂岩型铀矿床上方存在微航磁异常,高精度航磁完全能探测到。微航磁异常是此类矿床的特征异常之一,可以作为一种重要标志信息运用于前期成矿预测。 相似文献
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滇西可地浸砂岩型铀矿特征,成因类型及成矿模式 总被引：7，自引：2，他引：5
文阐述了滇西新生代盆地可地浸砂岩型铀矿的矿床特征,讨论了铀矿床的成因类型,认为属“潜水顺层氧化带型”铀矿床。根据铀矿床的形成机制,对滇西地区新生代盆地的砂岩型铀矿成矿模式进行了探讨。 相似文献
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Discontinuities such as fractures or cracks are common in geo-materials. Connectivity is a comprehensive parameter that includes the influence of length, orientation and density of the discontinuities. The main objectives of this paper are to define connectivity based on the statistical geometrical parameters of a network of random discontinuities and to quantify the hydraulic properties of the network using connectivity. An analytical method is first proposed to evaluate connectivity through the density of degree of freedom (DDOF). The analytically estimated DDOF is verified using numerical analysis. DDOF increases with the increases in the mean length, relative orientation and density of the random discontinuity network. Connectivity becomes better and the permeability becomes larger with increasing DDOF. The representative element volume (REV) of a random discontinuity network can be estimated based on connectivity. When a discontinuity network is poorly connected, a REV does not exist when the size of the discontinuity network is smaller than 10 times of the mean length of the discontinuities. When a discontinuity network is normally connected, a REV exists when the REV size is smaller than 10 times of the mean length of the discontinuities. When the discontinuity network is highly connected, the REV size is only 2–4 times of the mean length of the discontinuities. The results indicate that DDOF is a good indicator to quantify the connectivity of a random discontinuity network and the relationship between connectivity and permeability. 相似文献
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新疆吉木萨尔大龙口非海相二叠系—三叠系界线层段古地磁特征 总被引：5，自引：0，他引：5
通过对吉木萨尔县大龙口非海相二叠系-三叠系界线上下地层磁性特征的研究,在梧桐沟组-锅底坑组共发现78个极性异常,其中以负极性为主,间隔了一系列的正极性和过渡极性.梧桐沟组上部以负极性为主,间隔了2个正极性和过渡极性.这可与巴基斯坦盐岭和四川广元上寺的大隆组下部对比,即相当于Da段.梧桐沟组顶部和锅底坑组底部,正、负极性变化频繁,极性特征可与巴基斯坦盐岭和四川广元上寺大隆组中部对比,即相当于Db段.锅底坑组下部以负极性为主,间隔了2个正极性段,可与四川广元上寺大隆组中上部对比,即相当于Dc段.锅底坑组中下部以负极性为主,上部夹1个正极性段,可与四川广元上寺大隆组上部磁性特征对比,即相当于Dd段.锅底坑组中上部以负极性为主,间隔了4个正极性段,可与四川广元上寺飞仙关组下部对比,即相当于Fa段.根据磁性段的划分对比,将二叠系三叠系界线置于Fa和Dd之间,即本次研究测制剖面的41层和42层之间.根据各岩组的古地磁特征求得岩组形成时的古地磁极:梧桐沟组79.1°N,238.1°;锅底坑组72.3°N,322.2°;下三叠统77.5°N,320.8°.古纬度基本一致,为32°～35°N. 相似文献
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Keitaro KUNUGIZA 《Resource Geology》1999,49(4):199-212
Abstract: Boundaries between the cpx Zn-Pb ores of the Kamioka ore deposit and host clinopyroxene granitoid in the Hida metamorphic belt were examined to decipher the incipient stage of ore formation process. The boundaries are characterized by the compositional zoning of relic clinopyroxene with outward increase of XMg from 0. 5 to 0. 75 in the host rocks, and by the incline of XMg towards the ores, passing through the boundaries, reaching up to 0. 95. In the ores, relic clinopyroxene is rimmed by hedenbergite. Both clinopyroxenes show compositional zoning with outward decrease and increase of XMg and MnO, down to 0. 02 and to 3. 2 wt%, respectively. The presence of high magnesian clinopyroxene can be explained if hydrothermal fluid flow had leached hedenbergite component of relic clinopyroxene. The incline of XMg of clinopyroxene toward the ores was attributed to the degree of dissolution of clinopyroxene, and thus the total amounts of fluid to have passed. The outward decrease of XMg of clinopyroxenes in the ores was due to crystal-fluid fractionation during precipitation. These mineralogical changes at the boundaries indicate the time-integrated phenomena of hydrothermal ore forming process. Firstly, leaching of ore components by infiltrating fluid proceeded in host rocks, and enhanced the formation of a fluid channel. The condition of fluid changes through the fluid channel in P-T space, and hence ore forming minerals precipitate at a remote place from the leaching one. This in turn caused the physicochemical change of fluid condition anyhow, and accelerated the precipitation of the minerals. This leaching-precipitation sequence appears a basic process of hydrothermal ore-forming system, and characterizes the incipient stage of ore formation process of the Kamioka Zn-Pb ore deposit. Compositional zoning of clinopyroxenes defines Z-shaped compositional trend in the Di–Hd–Jo diagram, each arm of which corresponds to the leaching and the precipitation stages, and the secondary dissolution of precipitated clinopyroxene. 相似文献
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贵州罗甸二叠纪末生物大灭绝事件后沉积的微生物岩时代和沉积学特征 总被引：9，自引：1，他引：8
二叠纪末期发生的显生宙以来最大的生物绝灭事件,使海洋生态系统和陆地生态系统均受到重创之后,微生物岩广泛分布于全球正常浅海地区。研究认为,扬子地台在二叠纪末期存在一次海平面降低的事件,造成研究区二叠纪地层与早三叠世微生物岩之间存在沉积间断或剥蚀,并使三叠纪牙形石混入二叠纪末期的沉积物中。二叠-三叠系界线位于微生物岩层的底界;微生物岩形成于早三叠世最早期,相当于Hindeodus parvus带,是早三叠世最早期开始的海侵事件为其提供生长所需的可容纳空间。在Isarcicella staeschei带-I. isarcica带早期再次发生相对海平面降低事件,之后海平面开始快速上升。研究区早三叠世早期的微生物岩以凝块构造发育为特征,具有斑状、层状、枝状和网状凝块构造4种典型中型构造。结合前人的工作,认为微生物群落通过生物沉积和物理沉积作用形成球状体,球状体汇聚形成不同的中型凝块构造。研究扬子地台早三叠世凝块石的确切时代和结构、构造类型特征,为准确恢复生物大灭绝事件前后的环境变迁以及生物演化事件与环境变化的相互作用关系提供重要的证据。 相似文献
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A. Yu. Antonov 《Russian Journal of Pacific Geology》2007,1(2):153-175
This paper summarizes the results of long-term geological, petrological, and geochemical investigations of the Mesozoic-Cenozoic complexes of the Stanovoy Range in order to determine the main reasons for their generation and evolution. The analysis of this material showed that the compositionally variable Late Mesozoic igneous complexes of the Stanovoy Range were formed in various depth facies, from abyssal to surficial. The majority of their salic complexes show minor compositional variations, whereas the mafic complexes are more variable, especially in the southeast of the region. The southeastern Stanovoy Range comprises comparable amounts of both subalkaline and low-alkali igneous rocks, whereas the central part is dominated by subalkaline rocks, and the northwestern part contains rocks only of the shoshonite-latite series. This zoning is fundamentally different from that of typical island arcs, which are characterized by the occurrence of volcanic rocks of similar alkalinity in each zone. Extrusive and intrusive rocks with similar alkali and silica contents (and schlieren-like inclusions in the granitoids of the region) were formed from common magmas of corresponding chemical compositions. In addition, the mafic and most of the salic magmas were formed as independent melting products, whereas the magmas of intermediate composition were formed mainly by mixing of chemically contrasting liquids (i.e., salic and basic). It was shown that the available information on the magmatism of the region is best interpreted in terms of the model of mantle diapirism. In particular, mantle diapirs ascended rather slowly during the Mesozoic and occurred over the whole territory of the Stanovoy Range during the Jurassic-Cretaceous stage (J3-K1), when alkaline and subalkaline basalts were formed. During the Early-Late Cretaceous stage, mantle diapirs produced alkali-poor basalts in the central and eastern parts. During the Cenozoic, the diapir ascended rather rapidly but only in a small area in the eastern part of the region forming alkali basalts. In contrast to the Cenozoic, the Earth’s crust was strongly affected by mantle diapirs and related mafic magmas in the Mesozoic. As a result, crustal sequences were reworked by fluids and subsequently yielded tremendous volumes of compositionally corresponding salic magmas, which interacted and mixed with mafic magmas producing the corresponding chemical zoning. The maximum generation of crustal magmas was confined to the axial zones of ascending diapirs, where the highest energy effects took place, whereas the role of autochthonous gneissic granites increased away from the axis at the expense of typical intrusive complexes. 相似文献
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Investigation of the Upper Callovian to Lower Kimmeridgian microfossils from the Makar’yev reference section (Unzha River, East European Platform) has been carried out. The section is characterized by ammonite debris and abundant associations of benthic and planktic foraminifers. It is a perfect object for stratigraphic and paleoecological researches. The biostratigraphic distribution of foraminifers from the Makar’yev section allows one to identify standard foraminifera zones of the East European Platform, as well as to upgrade some of them. The analysis of vertical and lateral ammonites and foraminiferal distribution, completed with litho stratigraphy, has precised the stratigraphic volume and position of boundaries of several lithological units.An improved stratigraphic scheme for the Kostroma area of the Moscow Depression is proposed. Analysis of the composition, structure, and dynamic changes of the foraminiferal assemblages has been performed. The morphofunctional analysis of foraminiferal genera has for the first time identified how foraminiferal morphogroups differing in their life style and feeding strategy varied with short-term paleoenvironmental changes. These morphogroup changes allow establishing four ecostratigraphic levels. These paleoecological data have been calibrated along with geochemical factors. They have shown a crisis of foraminiferal association during the Late Oxfordian and Early Kimmeridgian. A similar crisis has also been discovered in the north of Siberia, which may be an argument for its global distribution. The analysis of the taxonomic composition and the density of foraminiferal associations, in parallel with the structure of the association, has revealed a succession of transgressive and regressive events during the Late Callovian-Early Kimmeridgian. It allows the typification of each assemblage in relation with each event and underlines the occurrence of second-order sea-level fluctuations (middle part of the Middle Oxfordian and the earliest Kimmeridgian). 相似文献
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The Atlas of Palaeogeography of China was published in 1955. This paper will introduce the impor- tant historical background of the compilation and publishing of the atlas. Actually it was a direct outcome of the famous Main geological structural units of China written by Huang Jiqing in 1945. Confined by the status of geological development of that stage, the atlas mainly presents the variation of the distribution of old landmasses and oceans during different geological stages. The compilation was based on facies types, palaeontological species , and features of regional fauna assemblages . The basic scale of the atlas was 1:1 000 000. There are totally 20 maps, spanning from the Sinian to Triassic of the Mesozoic. The compila-tion was finished in more than three years. The outline of landmasses and oceans, main direction of trans-gression and regression, distribution of fossils, crustal deformation, mineral deposits, as well as volcanic and glacial activities are shown with various patterns and colors 相似文献
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Horace Moo-Young Tommy Myers Barbara Tardy Richard Ledbetter Wipawi Vanadit-Ellis Tae-Hyung Kim 《Engineering Geology》2003,70(3-4):249-258
Marine sediment capping is a technique where clean sand or sediment is placed over contaminated sediment to reduce the migration of contaminants to the environment. Environmental regulations have limited the use of in situ sediment capping due to concerns about the contaminant migration through the cap. A series of centrifuge tests were conducted to simulate the effects of consolidation settlement of capped marine sediment. This study describes the testing and monitoring of the centrifuge tests. The results from the centrifuge tests are interpreted and compared to predictions made by the PSDDF computer program, which can qualitatively estimate the consolidation settlement of capped marine sediment.
Centrifuge tests were utilized to predict the consolidation of marine sediment caused by the placement of a capping layer. The centrifuge tests used the modeling of models technique to verify that correct modeling procedures were utilized. In this study, the maximum deviation between the centrifuge test results and PSDDF prediction was 20%. Thus, designers should utilize PSDDF consolidation settlement results with caution. Dye tracer studies showed the importance of consolidation-induced advective transport of contaminants. Thus, the capping layer must be appropriately designed to reduce the effects of consolidation-induced advective transport. This may be accomplished by adding a reactive barrier or geosynthetic barrier layer to the cap design. 相似文献
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The post-glacial environmental history of Voua de la Motte, a small pond, was studied by the lipid geochemistry of a 6 m long core. Palynological studies show that the deepest part of the core goes back to 10,000 yr BP corresponding to the time of formation of the lake following the retreat of the Rhodanian glacier. Hydrocarbons, aldehydes, linear alcohols, sterols, monocarboxylic and monohydroxy fatty acids, were determined throughout the core both in the free and bound lipid fractions, as well as in the tightly bound fraction for the carboxylic acids. There is no clear evidence of a transformation from the unbound to the bound form, except perhaps for the α-hydroxy acids.Qualitative as well as quantitative fluctuations in the distributions of these lipid classes were observed upward in the core. An attempt is made to correlate these fluctuations with the bioenvironmental and climatological evolution of the Basin on the basis of information obtained from palynology. 相似文献
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Jean-Christophe Maréchal Robert Wyns Patrick Lachassagne Kambhampati Subrahmanyam Frédéric Touchard 《Comptes Rendus Geoscience》2003,335(5):451-460
Pumping tests carried out in the fissured layer of a granitic hard-rock aquifer, interpreted at the observation wells by means of the analytical solution of Neuman and at the pumping wells with that of Gringarten show the existence of a strong vertical anisotropy of this layer of the aquifer; the horizontal permeability is clearly and systematically higher than the vertical one. These results agree perfectly with the geological observations, the fissured layer of the weathered granite profile showing the existence of many sub-horizontal fissures. It confirms that, within the fissured layer, the permeability of sub-horizontal fissures due to the weathering process dominates over that of sub-vertical fissures of tectonic origin. To cite this article: J.-C. Maréchal et al., C. R. Geoscience 335 (2003).To cite this article: J.-C. Maréchal et al., C. R. Geoscience 335 (2003). 相似文献