共查询到20条相似文献，搜索用时 31 毫秒
1.
G. C. Capitani H. Leroux J. C. Doukhan S. Ríos M. Zhang E. K. H. Salje 《Physics and Chemistry of Minerals》2000,27(8):545-556
The nature of the amorphous regions and their recovery processes in two natural metamict zircon samples from Sri Lanka have
been studied by high resolution and analytical transmission electron microscopy. Samples untreated and annealed at different
temperatures were investigated. Nanoprobe analyses on untreated samples and samples annealed at 1000 K show that within experimental
uncertainties, no chemical segregation occurred. In samples annealed at higher temperatures (≥1100 K) recovery occurs in a
two-stage process and leads to different microstructures, which depended on the initial amount of metamictization. In highly
amorphized samples, recrystallization starts at 1200 K. Randomly oriented ZrO2 grains embedded in a silica-rich matrix are detected. At higher temperature (16 h at 1600 K), the assemblage transforms into
a polygonal texture of small zircon grains. Some untransformed zirconia grains and pockets of silica-rich glass are still
present, however. In partially metamict samples, recovery starts at 1100 K. The small surviving oriented zircon domains grow
at the expense of the surrounding amorphous material. At 1200 K, new zirconia grains nucleate with random orientations. After
1 h annealing at 1400 K, the zircon structure is restored and the microstructure coarse-grained. The proportion of crystalline
zirconia and silica-rich glass has dramatically decreased.
Received: 15 November 1999 / Accepted: 1 March 2000 相似文献
2.
岩石显微构造分析现代技术——EBSD技术及应用 总被引：10，自引：0，他引：10
EBSD技术的发展,为岩石显微构造分析开辟了一个全新的领域。它与现代扫描电子显微镜和能谱分析等设备配合,可以同时对块状样品进行晶体结构与成分分析,从而使显微构造、微区成分与结晶学数据分析有机结合起来。
EBSD技术可以精确、快速定量标定包括各种晶系晶体颗粒的晶格方位和描述晶体颗粒的边界、形态等特征,对于具有低角度边界的晶体颗粒提供精确数据,为阐述岩石变形机制提供重要约束,并为高级晶族和不透明矿物结晶学组构与变形机制研究提供了有效的手段。EBSD尤其使获取微米级甚至纳米级尺度上颗粒（亚颗粒）或相之间的定向差别（达到20 nm的空间分辨率和0.3度角度分辨率）成为可能。EBSD技术在矿物相鉴定、亚微域内的应变分析、矿物出溶作用等方面的应用,进一步证明了这一新技术在显微构造分析及相关领域的应用前景。其广泛应用必将带来岩石显微构造研究的新突破,也将成为未来岩石变形机制与岩石圈流变学研究取得飞速发展不可或缺的技术手段。 相似文献
3.
Grain shape is a key factor affecting the mechanical properties of granular materials. However, grain shape quantification techniques to distinguish one granular material from another have not reached a stage of development for inclusion in modeling the behavior of granular materials. Part of the problem is the equipment of choice for grain shape measurement is the scanning electron microscopes. This is a relatively expensive and complex device. In this paper, we investigate a practical approach using light microscopy to quantify grain shape and to identify the key shape parameters that can distinguish grains. A light microscope was found to produce grain images with sufficient quality for the purpose of observing the grain shape profile. Several grain shape parameters were determined for eight different sands. We found Circularity, Roundness, Compactness, Sphericity, Aspect Ratio and ModRatio to be the key shape parameters that differentiate these sand grains. 相似文献
4.
The microstructure of halite from the subhorizontal, bedded Main Röt Evaporite Member at Hengelo, The Netherlands (AKZO well 382, depth interval of 420–460 m), was studied by transmitted and reflected light microscopy of gamma-irradiation decorated samples. Primary microstructures compare favourably with those found in recent ephemeral salt pans. Large, blocky, fluid-inclusion-poor halite grains and elongated chevrons are interpreted to have formed in the saline lake stage, while void-filling clear halite is interpreted to have formed during the desiccation stage of the salt pan. In addition, in all layers the grains are rich in deformation-related substructures such as slip bands and subgrains indicating strains of a few percent. The study of gamma-irradiation decorated thin sections shows that the main recrystallization mechanism is grain boundary migration. Grain boundary migration removes primary fluid inclusions and produces clear, strain-free new grains. Differential stresses as determined by subgrain size piezometry were 0.45–0.97 MPa. The deformation of the salt layers is probably related to Cretaceous inversion in the area. 相似文献
5.
ABSTRACT The study of sediment microfabric is fundamental to the understanding of various sediment properties including shear strength, compressibility, and permeability, evaluating depositional environments and investigating clay diagenesis. A technique is presented which preserves the particle integrity of fine-grained sediments while permitting examination of the same sample using light and electron microscopy techniques. The technique involves drying the sediment sample using a critical point drying apparatus and then impregnating it using low viscosity SPURR epoxy. Standard thin sectioning techniques are used for light microscopy, whereas ultrathin sections are made using a microtome for transmission electron microscopy work. Scanning electron microscopy investigations are performed on samples prior to impregnating. 相似文献
6.
This work contributes to the experimental investigations of the origin and 3-D orientation of micropores in low porosity crystalline rocks. The origin and spatial orientation of microporosity in two eclogites with different microstructures were studied by 1) quantitative and qualitative microstructural analysis of grains and grain boundaries, 2) measurement of lattice preferred orientation using the SEM-EBSD method and 3) experimental measurement of velocity of elastic P-waves in spherical samples in 132 directions under confining pressures up to 400 MPa. Results show good correlation between the elastic properties and the orientation of grain boundaries and cleavage planes in clinopyroxene. The magnitude and anisotropy of velocity change with pressure shows that microporosity in the fine-grained sample is relatively large and strongly preferentially oriented, whereas it is significantly lower and less preferentially oriented in the coarse-grained sample. Seeing that the lattice preferred orientation of clinopyroxene is similar in both samples we can deduce from velocity changes that the grain size of the rock forming minerals controls the amount of microporosity. Also, the orientation of microporosity depends mostly on preferred orientation of grain boundaries and somewhat less on the orientation of cleavage planes. Grain boundaries are therefore the most important contributors to the bulk microporosity in the studied rocks. 相似文献
7.
Zsolt Schléder János L. Urai Sofie Nollet Christoph Hilgers 《International Journal of Earth Sciences》2008,97(5):1045-1056
Zechstein (Z1) rocksalt from the Fulda basin, from the immediate vicinity of the Hessen potash bed is folded into tight to
isoclinal folds which are cut by an undeformed, 1 cm thick, coarse-grained halite vein. Microstructures were investigated
in etched, gamma-irradiated thin sections from both the wall rock and the vein. The lack of synsedimentary dissolution structures
and the widespread occurrence of plate-shaped and hopper grains in the wall-rock suggests that the sedimentary environment
was perennial lake. Deformation microstructures are in good agreement with solution-precipitation creep process, and salt
flow under very low differential stress. Strength contrast between anhydrite-rich and anhydrite-poor layers caused the small
scale folding in the halite beds. The vein is completely sealed and composed mainly of euhedral to subhedral halite grains,
which often overgrow the wall-rock grains. Those microstructures, together with the presence of occasional fluid inclusion
bands, suggest that the crystals grew into a solution-filled open space. Based on considerations on the maximum value of in-situ
differential stress, the dilatancy criteria, the amount of released fluids from the potash bed during metamorphism and the
volume change, it is proposed that the crack was generated by hydrofracturing of the rocksalt due to the presence of the salt-metamorphic
fluid at near-lithostatic pressure. 相似文献
8.
高铁路基粗颗粒土水力学参数测试方法研究 总被引：1，自引：0，他引：1
高铁路基粗颗粒土的水力学特性对路基内部水分运移及路基的长期累积变形有重要影响。而对这种高压实度的粗颗粒土,常规非饱和土试验仪器存在试样尺寸小、制样难度大的缺点,难以应用。介绍了一种用于测试高压实度路基粗颗粒土-水力学参数的试验装置,利用张力计和时域反射计量器,分别测量路基粗颗粒土在浸湿、干燥阶段不同高度处土体基质吸力、介电常数的变化情况,获得高压实度下高铁路基粗颗粒土土-水特征曲线;并通过瞬态剖面法获得路基粗颗粒土非饱和渗透系数与基质吸力的关系。试验结果表明,该套装置能够适用于最大粒径为20 mm的粗颗粒土,试样压实度最大可达到0.95。通过对一组试验结果分析,并结合Ekblad等试验结果,发现随着填料细颗粒含量增大,?（与进气值有关的参数）值逐渐减小,土体进气值增加;粒径越大,细颗粒含量越低,土体储水能力越低,对应n（与排水程度有关的参数）值越大。为路基粗颗粒土-水力学参数的测定提供了方法。 相似文献
9.
The Egyptian black sands contain several economic minerals, especially ilmenite. Monazite can reach concentrations up to 0.6 wt.%. The majority of monazite grains have light to deep canary and lemon yellow colors, whereas enigmatic monazite grains have brown, red, resinous, yellow and colorless to pinkish colors. The behavior of monazite with the electrostatic field setting of the roll-type electrostatic separator was studied for the different variables of the separator. Most of the monazite grains are reversible negative and are attracted towards the positively charged static electrode. Using wet gravity concentration, both low and high intensity magnetic separation, and electrostatic separation techniques, a high grade concentrate assaying 97 wt. % monazite with a recovery of 76.8% can be obtained. The Egyptian beach monazite contains high concentrations of Ce, La and Nd in addition to minor amounts of Y, Pr, Sm, Gd, Dy and Eu. It is particularly rich in the lighter rare earth elements (cerium subgroup). By a new method of ion exchange technique after chemically dissolving the mineral with sulfuric acid, both of REEs, Th and U, could be individually separated. The efficiency of the separation has been tested with sulfuric acid concentration at 2M H2SO4 where the thorium and uranium could be obtained with a cation exchange synthetic resin column, while rare earth metal ions are adsorbed and then individually separated. A highly pure thorium product could be obtained by oxalate precipitation followed by uranium precipitation as diuranate using NaOH. 相似文献
10.
Paul R.D. Mason Kym E. Jarvis Hilary Downes Riccardo Vannucci 《Geostandards and Geoanalytical Research》1999,23(2):157-172
Incompatible trace element abundances have been determined in mantle-derived clinopyroxenes by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in a comparative study with established microanalytical and bulk techniques. Individual clinopyroxene grains were sampled for the laser ablation study from sieved mineral separate fractions, from which similar mineral grains had been previously extracted for microprobe (SIMS) and bulk (INAA and ID-TIMS) analysis. Mineral grains were ablated with variable degrees of surface spatial resolution (50-200 μm) in order to maximise ICP-MS analyte count rates and to improve detection limits. A comparison of results from the different techniques reveals that for the most homogeneous samples LA-ICP-MS can achieve excellent levels of agreement with other techniques (10%) and good precision for most of the studied elements (1-5% RSD). Variations in calculated concentrations by LA-ICP-MS confirm inter- and intra-mineral heterogeneity determined by SIMS, reflecting changes in sample composition and texture. The long-term reproducibility of the technique is shown by the consistency of results for one sample analysed on thirteen occasions over a period of nine months. 相似文献
11.
Recent developments in the application of x-ray micro-tomography in laboratory geomechanics have allowed all the individual
grains of sand in a test sample to be seen and identified uniquely in 3D. Combining such imaging capabilities with experiments
carried out “in situ” within an imaging set-up has led to the possibility of directly observing the mechanisms of deformation
as they happen. The challenge has thus become extracting pertinent, quantified information from these rich time-lapse 3D images
to elucidate the mechanics at play. This paper presents a new approach (ID-Track) for the quantification of individual grain
kinematics (displacements and rotations) of large quantities of sand grains (tens of thousands) in a test sample undergoing
loading. With ID-Track, grains are tracked between images based on some geometrical feature(s) that allow their unique identification
and matching between images. This differs from Digital Image Correlation (DIC), which makes measurements by recognising patterns
between images. Since ID-Track does not use the image of a grain for tracking, it is significantly faster than DIC. The technique
is detailed in the paper, and is shown to be fast and simple, giving good measurements of displacements, but suffering in
the measurement of rotations when compared with Discrete DIC. Subsequently, results are presented from successful applications
of ID-track to triaxial tests on two quite different sands: the angular Hostun sand and the rounded Caicos Ooids. This reveals
details on the performance of the technique for different grain shapes and insight into the differences in the grain-scale
mechanisms occurring in these two sands as they exhibit strain localisation under triaxial loading. 相似文献
12.
Daniel Buscombe 《Sedimentology》2013,60(7):1709-1732
In images of sedimentary or granular material, or simulations of binary (two‐phase) granular media, in which the individual grains are resolved, the complete size distribution of apparent grain axes is well‐approximated by the global power spectral density function derived using a Morlet wavelet. This approach overcomes many limitations of previous automated methods for estimating the grain‐size distribution from images, all of which rely on either: identification and segmentation of individual grains; calibration and/or relatively large sample sizes. The new method presented here is tested using: (i) various types of simulations of two‐phase media with a size distribution, with and without preferred orientation; (ii) 300 sample images drawn from 46 populations of sands and gravels from around the world, displaying a wide variability in origin (biogenic and mineralogical), size, surface texture and shape; (iii) petrographic thin section samples from nine populations of sedimentary rock; (iv) high‐resolution scans of marine sediment cores; and (v) non‐sedimentary natural granular patterns including sea ice and patterned ground. The grain‐size distribution obtained is equivalent to the distribution of apparent intermediate grain diameters, grid by number style. For images containing sufficient well‐resolved grains, root mean square errors are within tens of percent for percentiles across the entire grain‐size distribution. As such, this method is the first of its type which is completely transferable, unmodified, without calibration, for both consolidated and unconsolidated sediment, isotropic and anisotropic two‐phase media, and even non‐sedimentary granular patterns. The success of the wavelet approach is due, in part, to it quantifying both spectral and spatial information from the sediment image simultaneously, something which no previously developed technique is able to do. 相似文献
13.
Yu. V. Plotkina E. B. Sal’nikova A. B. Kotov M. D. Tolkachev M. R. Pavlov 《Petrology》2006,14(2):201-208
The paper reports results obtained by the complex studying of zircon crystals from rocks of various genesis. Zircon is one of the minerals most often used as geochronometers. It also provides genetic information on superimposed processes that is “recorded” in the external and internal morphology of its crystals. This mineral is thoroughly examined to select its unaltered crystals for U-Pb dating by the single-grain method. Zircon grains are selected with the use of optical and electron microscopy and cathodoluminescence. This publication presents the first results obtained by examining zircon by computer microtomography (μCT) and the results of the studying of the external and internal structure by conventional techniques ([optical microscopy and SEM (SE and CL)]. The paper demonstrates the advantages of the application of the μCT techniques to the selection of targets for U-Pb zircon dating: there is no need for the special preparation of the samples and no material is destructed. However, this technique may be not informative enough if the zircon contains inherited core whose density does not differ from the density of the surrounding mineral. 相似文献
14.
In this paper, we examine whether till grain size affects the range and occurrence of micromorphological features associated with subglacial shear. Our till samples were collected from two glaciers in Iceland, and varied in texture from a coarse, sandy clast-rich till (Fjallsjökull) to a fine-grained silty-sandy till (Vestari-Hagafellsjökull). We found a wide range of deformational microstructures that included skelsepic plasmic fabric, intraclasts of pre-existing eroded bedrock (basalt) and weathered clay and ‘mini-shear zones’ between clasts. We classified our micromorphological data into three classes; rotational, intermediate and linear. In addition to these observations, we performed extensive microfabric analysis at different scales on all of our samples. We found that the coarse-grained till contained a greater number and variety of microstructures than the fine-grained till. In addition, the fine-grained till showed a distinct lack of rotational structures that we attribute to the lack of significantly sized clasts in the matrix. We argue that the varied texture of the coarse-grained till provides a greater degree of perturbation within the shearing layer and so more distinct microstructures form. In a more fine-grained till, shearing is more homogeneous since there are less perturbations in the matrix and this leads to a more singular kind of microstructure. Our observations suggest that subglacial shear occurs within a multi-layered patchwork of different grain sizes, competence and pore water pressures. It is these factors that are so crucial in determining the occurrence and type of microstructural evidence we see in subglacial tills. 相似文献
15.
I. Kh. Shumilov 《Geology of Ore Deposits》2008,50(8):763-771
Copper sulfide pseudomorphs after phytodetritus in ore-bearing sedimentary rocks of the Middle Timan region were studied by ore microscopy, X-ray methods, electron scanning microscopy (microprobe), and chemical analysis. It was established that jurleite rather than chalcocite, as was previously assumed, is the major copper sulfide in pseudomorphs. Other copper sulfides detected in microscopic amounts are inferior to jurleite in abundance. Two types of jurleite—white and light blue—can be distinguished under an ore microscope. In addition to color, jurleite varieties differ in size of crystals and hardness. White jurleite occurs as large grains in superficial crusts and pith pseudomorphs or fills contraction fissures in plant tissue. Light blue jurleite segregations are combined with microgranular units and altered wood. Part of the light blue jurleite replaces the white variety. Light blue jurleite has a higher relief on a polished surface. The common crystallographic orientation of sulfide grains in pseudomorphs was noted for all modes of occurrence of jurleite. Jurleite grains of various shapes and different hardness may be detected in the same sample. In general, copper sulfides were formed in the following sequence: (i) filling of fissures and interstices in wood, (ii) formation of superficial crusts composed of white jurleite, (iii) joining of fissures by pseudomorphs after organic matter and partial replacement of white jurleite with the light blue variety, and (iv) secondary transformation of light blue jurleite with partial redistribution of its constituents between less frequent copper sulfides. 相似文献
16.
17.
Texture development of recrystallised quartz polycrystals unravelled by orientation and misorientation characteristics 总被引：1，自引：0，他引：1
The development of microstructures and textures (i.e. crystallographic preferred orientations) during recrystallisation of naturally deformed quartz polycrystals has been studied via electron diffraction techniques in the scanning electron microscope. In the investigated sample series of quartz-rich rocks originating from different deformation regimes, the microstructural and textural changes in quartz have been significantly influenced by dynamic recrystallisation. Based on microstructural observations paired with orientation and misorientation analyses down to the scale of grains and subgrains, criteria could be established which characterise the dominant recrystallisation process and its influence on texture development. It is shown that the texture development during dynamic recrystallisation is controlled by a differential activation of slip systems in grains of ‘soft’ and ‘hard’ orientations. The analyses provide further evidence that specific grain orientations are preferred during crystal plastic deformation, recrystallisation and grain growth. The influence of twinning after the Dauphiné law was also investigated. Observations of a progressive reduction in the population of Dauphiné-twin boundaries during recrystallisation and a penetrative deformation in both hosts and twins indicate a generation prior to deformation and recrystallisation. A mechanical origin for twinning and possible influence on texture development was therefore discarded. 相似文献
18.
CLSM技术应用于化石硅藻微构造的尝试研究 总被引：2，自引：1，他引：1
首次采用激光扫描共聚焦显微系统(Confocal Laser Scanaing Microsystem)的新方法对西藏化石硅藻进行了微构造的尝试研究,通过对标本不同层面的系列扫描和三维重组立体图像的观察,揭示了采自西藏阿里地区和山南地区湖相沉积剖面的化石硅藻的微构造及形态特征,发现了某些对硅藻分类、示相特征的新标识,并在CLSM技术的应用方面获得了新的认识. 相似文献
19.
Marthinus Cloete Rodger J. Hart Herbert K. Schmid Martyn Drury Chris M. Demanet K. Vijaya Sankar 《Contributions to Mineralogy and Petrology》1999,137(3):232-245
Submicroscopic opaque particles from highly shocked granite-gneisses close to the core of the Vredefort impact structure
have been investigated by means of micro-analytical techniques with high spatial resolution such as electron diffraction,
orientation contrast imagery and magnetic force microscopy. The opaque particles have been identified as nano- to micro-sized
magnetite that occur in several distinct modes. In one sample magnetite occurs along relict planar deformation features (PDFs)
in quartz, generally accepted as typical shock lamellae. The magnetite particles along shock lamellae in quartz grains virtually
all show uniform crystallographic orientations. In most instances, the groups of magnetite within different quartz grains
are systematically misorientated such that they share a subparallel <101> direction. The magnetite groups of all measured
quartz grains thus appear to have a crystallographic preferred orientation in space. In a second sample, orientations of magnetite
particles have been measured in microfractures (non-diagnostic of shock) of quartz, albite and in the alteration halos, (e.g.
biotite grains breaking down to chlorite). The crystallographic orientations of magnetite particles are diverse, with only
a minor portion having a preferred orientation. Scanning electron microscopy shows that magnetite along the relict PDFs is
invariably associated with other microcrystalline phases such as quartz, K-feldspar and biotite. Petrographic observations
suggest that these microcrystalline phases crystallized from locally formed micro-melts that intruded zones of weakness such
as microfractures and PDFs shortly after the shock event. The extremely narrow widths of the PDFs suggest that heat may have
dissipated rapidly resulting in melts crystallizing relatively close to where they were generated. Magnetic force microscopy
confirms the presence of magnetic particles along PDFs. The smallest particles, <5 μm with high aspect ratios 15:1 usually
exhibit intense, uniform magnetic signals characteristic of single-domain magnetite. Consistent offsets between attractive
and repulsive magnetic signals of individual single-domain particles suggest consistent directions of magnetization for a
large proportion of particles.
Received: 16 November 1998 / Accepted: 17 May 1999 相似文献
20.
Transmission electron microscopy (TEM) was used to study the microtextural and mineralogical characteristics of fine-grained rims in the unbrecciated CM2 chondrites, Y-791198 and ALHA81002, in an effort to provide constraints on the origins of the rims themselves. Our TEM observations show that the rims in Y-791198 are composed of two distinct types of region, sulfide-poor and sulfide-rich, that are intermixed in a complex manner at the micron to submicron level. The sulfide-poor regions are largely composed of amorphous silicate material or nanocrystalline serpentine, but rare fibrous and coarse-grained serpentine grains have also been identified. No fine-grained cronstedtite or tochilinite were observed, although coarse-grained lumps of tochilinite are present in the rims. In contrast, the sulfide-rich regions are characterized by the presence of a myriad, nanometer-sized Fe, Ni sulfide grains (pentlandite with some Ni-rich pyrrhotite) embedded within an amorphous silicate similar in composition to that of the sulfide-poor regions. The sulfide-rich regions also contain rare phases such as olivine, and Fe, Ni metal grains with grain sizes that are always >100 nm in size. Z-contrast scanning transmission electron microscopy (STEM) reveals that the fine-grained rims consist of a mosaic of irregularly-shaped sulfide-poor and sulfide-rich-regions with sizes of about 0.2-0.5 μm, that have been compacted together during parent body lithification. Despite aqueous alteration, the distinct mineralogical characteristics of these different regions are preserved on a fine-scale and probably represent primitive heterogeneity in the dust from which these rims formed.Serpentine is much better developed and more widespread in the fine-grained rims of ALHA81002 than Y-791198. Complex mats of serpentine fibers are commonly found and cronstedtite and tochilinite are plentiful. Anhydrous minerals such as olivine are rare and have usually been replaced by serpentine. Like Y-791198, all the fine-grained rims studied in ALHA81002 show the same mineral assemblages and textural characteristics throughout and between rims. The homogeneity of the mineralogy, textural relationships and degree of hydration in the rims of these two chondrites is more consistent with parent-body alteration than with pre-accretionary alteration. 相似文献