Influences of Mineralogy and Water Content on the Mechanical Properties of Argillite

Callovo-Oxfordian (Cox) argillite was investigated in the context of feasibility studies for an underground repository for nuclear waste. In this study, the influence of mineralogical composition and water content on the mechanical properties of the Cox argillite was investigated. The samples were drilled from three representative depths at which the rock formations have different mineralogical compositions. Micro-indentation and mini-compression tests were performed on samples with different water contents. The elastic and failure properties of argillite were determined and were found to be related to the mineralogical composition and water content. Both the elastic modulus and strength decrease with increasing clay and water contents.     

南秦岭千家坪钒矿床地质地球化学特征与钒的富集规律

千家坪钒矿床产于南秦岭下寒武统水沟口组(缀1sh)黑色岩系中,该黑色岩系由黑色含炭硅质岩、含炭硅质岩夹泥岩和泥岩等组成。钒矿体呈层状产出,矿石以黑色硅质岩夹泥岩型为主,含钒矿物主要为钒云母。黑色岩系岩石主要成分为SiO2、Al2O3、K2O等,富集TFe、Ba、Zn、P、Cu、Ni、Cr、Sr、Zr、Ag、Ti、Mn、V等多种元素。黑色岩系n(V)/n(Cr)=5.92～30.64、n(V)/n(V+Ni)=0.88～0.99、δU1,判断其为缺氧沉积环境。黑色硅质岩n(SiO2)/n(Al2O3)=238.81,U/Th1以及δ30Si=-0.1‰～0.5‰、δ18O=20.2‰～25.8‰,判断其为半深海滞留沉积盆地热水沉积成因。泥岩n(SiO2)/n(Al2O3)=5.69,n(Al)/n(Al+Fe+Mn)=0.63,n(Si)/n(Si+Al+Fe)=0.74～0.76判断其物源为陆源,但受到热水作用影响。钒矿化受下寒武世古隆起边缘断陷滞留盆地中形成的黑色岩系层位所控制。钒明显趋向在炭硅质岩所夹的泥岩或硅质岩附近的泥岩中富集,在炭硅质岩夹泥岩段向泥岩段过渡层位,常常含结核,钒元素含量达到峰值,其他Cu、Pb、Zn、As、W、Mo等元素富集规律与V元素基本一致。该矿床成矿物质主要来源于深部热水,泥岩的吸附作用对钒的富集具有重要作用。综合地质、地球化学特征,认为该矿床为热水喷流沉积成因。     

Shear strength behaviour of compacted clayey soils percolated with an alkaline solution

In the French model of deep nuclear wastes repositories, the galleries should be backfilled with excavated argillite after the site has been filled. After thousands of years, the degradation of the concrete lining of the galleries will generate an alkaline solute (pH > 12) that would circulate through the backfill. The goal of this paper is to describe the impact of such solute circulation on the properties of compacted argillite. Since additives (bentonite, sand or lime) are often introduced in the remoulded argillite for the backfill, such mixtures were also studied. Saturated-portlandite water was circulated through compacted samples for 3, 6 and 12 months at 60 °C. The shear strength behaviour of the samples was determined with triaxial tests. The microstructure of the samples was analysed via mercury intrusion porosimetry tests and scanning electron microscopy. The results showed that the influence of the alkaline fluid on the properties of the argillite is a function of the nature of the additive. In the case of the calcareous sand, no major changes were observed. The pure argillite underwent a slight decrease in its cohesion due to limited dissolution of its clayey particles. Conversely, intense alteration of the bentonite–argillite mixture was observed, and the shear strength behaviour was modified. Lime addition improved the mechanical characteristics of the argillite.     

包含变质岩分类三要素的主要变质岩分类表

变质岩分类的三要素是:变质岩的物质成分(化学成分、矿物成分)、变质岩的组构(结构、构造)和变质岩的成因(变质作用类型和形成变质岩的物理化学条件).由于变质岩的化学成分、矿物成分、组构特征和形成变质岩的地质环境十分复杂,致使至今尚无以变质岩分类三要素为基础的、内容比较完善的分类方案.本文中主要变质岩的分类是以其分类三要素为基础编制的,首次将不同成因的变质岩类并列于同一表中、将鉴定变质岩的主要标志性矿物成分和组构特征列入同一分类表中.该分类对鉴定变质岩石具有可操作性和实用性,分类表中涵盖了自然界主要的变质岩石.     

古生界海陆过渡相黑色泥质岩系显微组分特征及生气潜力评价

本文对华北和下扬子区两种类型的海陆过渡相地层进行详细的有机岩学工作，研究了泥质岩系中有机显微组合的岩石学特征、有机显微组成特征，表明壳质组是重要的生气母质。根据气源岩中有机显微组分组成特征，结合模拟实验结果提出产气指数的计算方法，并根据产气指数判断气源岩的生气潜力，下扬子区泥岩为好的生气源岩，华北地区的泥岩为较好的生气源岩，它们比煤具更大的生气能力。     

Study of the Anisotropic Properties of Argillite Under Moisture and Mechanical Loads

Due to various factors, such as sedimentation, layered morphology of clay minerals, in situ stress, etc., argillite rocks often exhibit anisotropic behavior. In order to study the anisotropic properties of the Callovo-Oxfordian (COx) argillite of the Meuse–Haute-Marne site in France considered as a possible host rock for high-level radioactive nuclear waste repository, a series of tests including uniaxial compression and dehydration and hydration at different constant applied stress levels are carried out. In this study, a specific setup combining moisture and mechanical loading with optical observation is used and it allows to continuously capture surface images from which the full-field strains are determined by using Digital Image Correlation techniques. The results show evidence of the mechanical and hydric anisotropy of the material. The anisotropy parameters are identified, assuming the studied argillite as transversely isotropic. The shrinkage and swelling depend on the applied stress and the angle with respect to the vertical direction of the mechanical load and the stratification plane, and this dependence is quantified. The non-linearity and the hysteresis observed during dehydration and hydration cycles are discussed.     

The Composition Microstructure and Physico-chemical Properties of Marine Soil in South China Sea

In this paper, mineral composition, microstructure, cementing materials, physico-chemical properties of marine soil are systematically investigated and chemical composition of sea water are analysed. Soil samples for this study are obtained from three areas: Weizhou Island, Hainan Island, Nansa Islands in South China Sea. Experimental results indicate that the mineral composition of marine soil mainly consists of ellite, chlorite, kaolinite and quartz, the cementing materials contains free oxides, carbonate and organic matter, the variety of microstructure is also revealed. The properties mentioned above would be the main causes of special engineering characters of marine soil.     

南海海洋土的成份结构和物化性质

本文系统地研究了海洋土的矿物组成、微观结构、胶结物质、物化性质和海水的化学成份。研究的土样采自南海三个海域:涠洲岛、南沙群岛和海南岛。研究结果表明,南海海洋土的矿物成份主要为伊利石、绿泥石、高岭石和石英;主要胶结物质是游离氧化物、碳酸盐和有机质;微观结构复杂多变。以上这些特征是形成海洋土特殊工程性质的主要原因。     

Results of mineralogical–geochemical researches of two high-mountain kudurs within territory of Caucasus

The article focuses on the development of the reasons of the consumption by the wild herbivorous animals of the subsurface rocks in the apical part of Alous and Atamagu mountains, situated on the territory of the Caucasian State Biosphere Reserve. It was investigated the mineralogical and geochemical peculiarities of the eaten and not eaten rocks, the chemical composition of their water extracts and also the chemical composition of vegetation. It was determined that the consumed rocks mainly consist of the clay mineral illite, crystalline silica, hydrous micas and chlorites and are the derivatives of eolation of the Paleozoic granitoids in one case, and argillite–aleurolites of the Jurassic age in the second case. The chemical composition of the aqueous extracts demonstrated the relatively low contents of natrium and other macrocomponents in comparison with the non-consumed rocks, and also the increased content of lanthanides. The elicited facts are not compatible with the hypothesis that the pursuance for geophagia in animals at Caucasus can be connected with the peculiarities of elements change from lanthanide group in the organism.     

In situ investigations and reactive transport modelling of cement paste/argillite interactions in a saturated context and outside an excavated disturbed zone

The interactions between cementitious materials and a clayey deep formation were investigated by studying the specific in situ context of the Tournemire Underground Research Laboratory (URL) of the French Institute for Radioprotection and Nuclear Safety and by reactive transport modelling using the HYTEC code. The study forms part of the safety assessment framework for the deep geological disposal of high to intermediate level long-lived radioactive waste. The in situ context investigated in the Tournemire URL corresponds to an engineered cemented borehole crosscutting the Toarcian argillite formation. The argillite/CEM II cement paste contacts have been in place over 18 a and were sampled in a saturated context outside the excavated disturbed zone (EDZ). Studies of the mineralogy (XRD, carbonatometry, SEM and TEM), petrophysical properties (BET) and geochemistry (TOC, Sr contents, C, O and Sr isotopes, EDS analyses) were carried out both on the argillite and on the cement paste in contact. Alteration of the cement paste is clearly expressed by decalcification and the opening of macroporosity. These modifications are mainly due to the dissolution of portlandite. The neoformation of C–S–H phases was identified in the first few micrometre next to the argillite interface, along with secondary carbonates at the outermost contact. Geochemical measurements argue for the introduction of a sedimentary fluid into the macroporosity of the cement paste to explain the formation of part of these secondary phases. This hypothesis is considered and tested using the HYTEC code, which indicates that such transport could have occurred near the argillite/cement paste contact at a very early stage. After this stage, the transport was reversed and ‘cementitious’ fluids flowed from the cement paste to the argillite. The changes brought about by these fluids are observed over a thickness of 11–13 mm in a so-called ‘black rim’, in which carbonates and C–S–H secondary phases are identified in the matrix of the sediment. An illitization process may also be observed in this altered rim, reaching its maximum development towards the inner part. Geochemical analyses show that the argillite disturbances are strictly confined to the black rim. Theoretical mineralogical profiles based on thermodynamic equilibria defined by the HYTEC code are in good agreement with the observations, and are used to achieve a better understanding of transport processes.     

Contact metamorphic mineral assemblages,late Triassic Newark group,New Jersey

Essentially isochemical thermal metamorphism of soda-rich Stockton, Lockatong and Brunswick formations of the Newark Group by diabase sills produced unusually varied and unique mineral assemblages, most of which are predominantly Na. feldspar and biotite. Within a meter of a sill Stockton arkose was altered to quartzo-feldspathic hornfels with common diopside and sphene. Within 50 m of a sill Lockatong calcitic and dolomitic mudstone formed calc-silicate hornfels with differing combinations of diopside-hedenbergite, andradite and grossular, prehnite, datolite, idocrase and wollastonite. Within a meter of a sill metamorphosed Lockatong calcareous feldspathic argillite contains sanidine-anorthoclase, aegirine, aegirine-augite, riebeckite and scapolite. Lockatong analcime-dolomite argillite was altered to unique feldspathoidal assemblages containing cancrinite, natrolite-thomsonite and rarely sodalite within 134 m, and nepheline within 30 m of the Byram Sill. Reddish-brown Brunswick mudstone produced spotted pelitic hornfels within a few 10's of meters of a sill.Response to thermal metamorphism varied directly with diminishing grain size. In both sandstone and mudstone Na. feldspar increases and K. feldspar decreases toward intrusions; quartz is rare or absent in highest-grade hornfels. Development of biotite was retarded by detrital clay minerals and hematite pigment, as well as by low temperature. Minor differences in composition among carbonate-rich and analcime-rich Lockatong deposits led to a diversity of closely associated assemblages. Aqueous solutions and relatively low temperature, probably in part during retrogressive metamorphism, produced hydrous minerals. Datolite, tourmaline, scapolite and fluorite suggest minor additions of volatiles, but the widespread feldspathoids were made from soda-rich sedimentary rocks without significant additions from an igneous source.     

A micromechanical-based elasto-viscoplastic model for the Callovo-Oxfordian argillite: Algorithms,validations, and applications

For a potential geological barrier of high-level radioactive waste repositories in France, the long-term mechanical behavior of the Callovo-Oxfordian (COx) argillite is the most concern for engineers. In this paper, a micromechanical-based elasto-viscoplastic model is proposed, and its numerical realization is our main object. The COx argillite is considered as a three-phase composite consists of porous clay, quartz, and calcite. By assigning appropriate constitutive laws to those constituents, the macroscopic elasto-viscoplastic behavior of the COx argillite is determined with an extended Hill's incremental approach. The numerical aspects includes (a) a new formulation is proposed for the plastic multiplier when adopting the overstress (Perzyna) model to define the viscoplastic strain. Meanwhile, a new formulation is also proposed to solve it within the framework of an implicit returning mapping scheme. (b) The corresponding consistent tangent moduli are strictly derived by extending the method proposed for solving plastic problems; (c) the efficiency of the proposed integration algorithms for the local constitutive equations and the homogenization procedure are validated, receptively, by a built-in porous plasticity model of a commercial finite element (FE) program ABAQUS and by FE computations of a two-phase unit cell; and (d) the proposed micromechanical model is finally applied to simulate experiment data in short-term triaxial compression tests and long-term triaxial creep tests. And the numerical results show that it is able to reflect the variation of the mechanical behavior with respect to the varied mineralogical compositions.     

南极中山站区电气石及其与变质作用的关系

南极中山站区的巨晶“电气石”实际上是柱晶石。电气石的确存在,但颗粒细小,含量较低。根据其颜色、成分和产出特征,至少可分为三种类型,不同的电气石与变质作用发展的不同阶段有关。电气石在麻粒岩相变质作用条件下能够稳定存在,与其它硼硅酸盐矿物（即硅硼镁铝矿和柱晶石）的缓冲作用有关。     

Knowledge of the three French underground laboratory sites

From March 1994 to August 1996, ANDRA conducted a large reconnaissance work on three sites for possible underground research laboratories. These surveys highlighted for each site the presence of a geological formation, the properties of which meet the requirements of the French Fundamental Safety Rules. On the East site, the selected formation is a 130 m thick argillite layer. On the Gard site the layer is composed of close-packed siltites which are 200–400 m thick. On the Vienne site a hercynian granodiorite batholith was found under a 160 m thick jurassic overdurden.     

陕西山阳县黑色岩系中中村—银花钒矿床地质特征

秦岭黑色岩系中带的钒矿构成超大型规模,中村-银花钒矿是大型钒矿的典型代表,产于下寒武统水沟口组中段硅质板岩-泥板岩-粘土质泥板岩岩性转换过渡层位中.矿石根据岩性划分为硅板岩型、粘土质泥板岩型和硅质泥板岩型3种类型.矿层延长及厚度稳定,V2O5品位为0.70%～1.17%.研究查明,钒与粘土质、泥质板岩密切相关,钒在粘土泥板岩中相对富集.钒与铝、钾、铁存在较密切的地球化学共生关系.钒以钒酸盐、磷酸盐及吸附状态存在于高岭石、水云母中.研究认为,含钒黑色岩系是扬子大陆向华北大陆俯冲启动下,于早寒武世扬子大陆北缘斜坡出现在拉伸裂谷式沉积环境,发育滞留深水环境下的炭-泥-灰-重晶石-硅质含钒沉积建造,含钒的炭质硅板岩-炭质泥板岩层具有热水沉积产物的特征.     

氩同位素用于库车坳陷天然气主力气源岩判识

稀有气体是天然气中指示其地球化学特征的重要组分,放射成因氩( Arr)的年代积累效应广泛应用于同位素定年和天然气的气源对比.本文系统地讨论了 40Ar的形成机理及其运移进入气藏的过程,利用 40Ar的母体元素 K在煤和煤系泥岩中的丰度差异,分析了以煤和煤系泥岩为母源的天然气 40Ar/36Ar同位素组成上的不同,并利用这种差异对煤系中煤岩或煤系泥岩为源岩的天然气藏的主力源岩进行了判识,继而建立了利用氩同位素组成判识煤系烃源岩主力源岩的方法.利用此方法对塔里木盆地库车坳陷三叠系-侏罗系煤与煤系泥岩互层的烃源岩进行了探讨, 数学计算结果表明该区主力源岩为煤系泥岩, 煤对天然气藏的贡献较小.     

吉林四平山门银矿工艺矿物学

运用综合方法对四平山门银矿进行了工艺矿物学研究，查明了矿石的物质成分，矿物种类，银矿物的嵌布特征以及银在各类矿物中的分配，并在此基础上，阐明了影响选矿工艺的矿物学因素，为选矿流程结构的确立，产品方案的选择以及精矿品位的提高和有害杂质砷对质量影响程度的估计都起到了有效的指导作用。     

Numerical modelling of in situ behaviour of the Callovo–Oxfordian argillite subjected to the thermal loading

To enhance the understanding of thermal impact on the in situ behaviour of the Callovo–Oxfordian argillite, this paper presents an interpretation of an in situ heating experiment carried out in the Meuse/Haute Marne Underground Research Laboratory (M/HM URL). The argillite was heated successively by two constant heating powers: 277 W and 925 W. When subjected to thermal loading, the argillite exhibits an important volume change and a strong pore pressure response that significantly affect its hydraulic and mechanical behaviour. Numerical analysis has been performed by using a coupled theoretical formulation that incorporates a constitutive model especially developed for this material. Based on Biot's theory, this model includes the influence of interstitial pressure on the mechanical behaviour. The simulation obtained reproduces satisfactorily the results of the in situ experiment and the main observed patterns of behaviour. The interpretation and discussion of numerical results provide additional data that can help us to understand the thermo-hydromechanical behaviour concepts of saturated argillite formation.     

A Study on Microstructure Composition of Unsaturated Red Mud and its Impact on Hydraulic Characteristics

Micro-test approaches like XRF, XRD and SEM and routine soil tests were applied to analyze the chemical composition, mineral composition, microstructure and basic physical property indicators of three kinds of red mud, which were the Bayer red mud, sintering red mud as well as the mixed red mud prepared by sintering red mud and the Bayer red mud at the mixture ratio of 1:1. On this basis, in the dehumidification-moisture absorption process, the relationship among matric suction, hydraulic conductivity and moisture content of the three types of red mud was studied by transient hydraulic characteristic cyclic test of unsaturated mud. The results indicated: physicochemical properties of the three kinds of red mud, such as mineral composition, microstructure and size grading varied remarkably; on the condition of the same moisture content, SWCC and HCFC of the three kinds of red mud demonstrated obvious hysteresis effect, which is the most significant on the Bayer mud, less on the sintering red mud and the least on the mixed mud; the Bayer red mud possess smaller hydraulic conductivity, worse drainage and stability.