Quantitative X-ray diffraction analysis of clay-bearing rocks from random preparations (original) (raw)
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Radiation Physics and Chemistry, 2014
Diffraction and spectroscopic techniques have been shown to be suitable for obtaining physical and mineralogical properties in polycrystalline soil samples, and also in their precursor compounds. For instance, the X-ray fluorescence (XRF) spectroscopy allows obtaining the elemental composition of an investigated sample, while the X-ray diffraction (XRD) technique permits obtaining qualitative and quantitative composition of the soil minerals through the Rietveld method (RM). In this study Yellow Latosol (Oxisol), Yellow Argisol (Ultisol) and Gray Argisol (Ultisol) soil samples, classified as ''hardsetting soils'', extracted from areas located at Northeast and Southeast of Brazilian coast were investigated. The soils and their fractions were analyzed in an EDX-700 and an XRD-6000 (Cu K a radiation). XRF results indicate high percentages of Si and Al, and small percentage of Fe and Ti in the investigated samples. The DRX data and RM indicate that there was a predominance of kaolinite and halloysite minerals (kaolin group minerals) in the clay fractions, which are presumably responsible for the formation of kaolinitic plasma in these soils. Also, the obtained results showed that the XRF, XRD techniques and RM were very helpful for investigating the mineralogical composition of a hardsetting soil. (L.V. Prandel).
Clays and Clay Minerals, 1984
As part of a laboratory study of the hydrothermal alteration of kimberlite, a mass balance procedure has been developed for estimating the relative proportions of synthetic phyllosilicate phases-chlorite, vermiculite, smectite, kaolinite and serpentine-present in reaction products. The procedure is based on a combination of X-ray powder diffraction (XRD) measurements (for phase identification), atomic absorption determinations (for total Si, A1, Fe, and Mg) and published analyses of clay minerals (for stoichiometric deductions). It centers on the computer inversion of a 4 x 4 matrix form of four simultaneous equations representing the mass balance of Si, A1, Fe, and Mg in four chosen minerals and incorporates a systematic routine for selecting from all possible permutations of high and low estimates of the mineral chemical analyses acceptable sets of product stoichiometries and phase proportions consistent with the total metal analyses. To minimize uncertainties and computing time, the program takes account of elemental relationships and water mass balances associated with phyllosilicates. It also accommodates data relevant to poorly crystalline phases for which a range of theoretical type-analyses modeled on aluminum oxyhydroxides and 9-1 l-A, 2:1 layered aluminosilicates are employed. The procedure produces reliable trends in phase proportions consistent with the intensities of characteristic XRD peaks of clay minerals present in the analyzed mixture; for example, increases in estimated kaolinite proportions correspond with larger 7-/k (and other) peaks in analyzed samples. A precision of 7-25% has been routinely achievable.
Clay Mineralogy: Spectroscopic and Chemical Determinative Methods
Journal of Environmental Quality, 1995
Of the determinative methods used to study clay minerals, chemical analysis is the oldest and most established. Before the development of the earliest instrumental techniques, such as X-ray diffraction and thermal methods, the identification of clay-mineral phases was accomplished by chemical analysis, supplemented where possible by optical data and physical characteristics such as specific gravity, colour, hardness, etc. However, fine-grained materials cannot be characterized reliably using these methods alone, and misidentifications were common. With the routine application of infrared spectroscopy and electron microscopy, in addition to X-ray diffraction and thermal analysis, instrumental techniques are now unquestionably superior to chemical analysis for clay-mineral identification and a clay is often described and identified without recourse to chemical analysis. Nevertheless, for complete characterization, a chemical analysis is still essential, as this is the only way that a structural formula can be calculated and the distribution of cations in the structure defined directly. A full characterization should include the determination of all the major and minor elements (with the proportion of the iron present in the ferrous and ferric forms) and also the determination of the cation-exchange capacity and, if possible, the anion-exchange capacity. Classification of clay minerals has always depended heavily on chemical data, and many clay-mineral groups, such as smectites, illites and chlorites, are subdivided according to composition. The characterization of a clay mineral as 'dioctahedral' or 'trioctahedral' can be determined from a b-dimension measurement using X-ray or electron-diffraction techniques, but these terms also have a chemical connotation, indicating the valency of the cations occupying the octahedral sheets. The type and Clay Mineralogy: Spectroscopic and Chemical Determinative Methods.
BASELINE STUDIES OF THE CLAY MINERALS SOCIETY SOURCE CLAYS BY X-RAY PHOTOELECTRON SPECTROSCOPY
Clay Science, 2018
This paper presents an overview of the chemical analyses of the Clay Mineral Society Source Clays based on X-ray Photoelectron Spectroscopy. This technique does not require any detailed sample preparation and is therefore easy to perform. In contrast to other common chemical analytical techniques fluorine and chlorine can be analysed together with all the major elements. In addition, the high resolution spectra reveal some details about the local environment of different cations in the clay structure, such as the presence of water, distinction between octahedral and tetrahedral aluminium and the presence of two types of Mg in the octahedral sheets.
X-Ray Diffraction in Mineralogical Research
Journal of ISAS
A brief account of role of X-ray diffraction (XRD) in mineralogical research with special reference to radioactive and atomic minerals is given. Aspects of research methodology such as sample preparation, analysis time, limitations, search match methods for identification, and complimentary techniques are also given. The most common applications of XRD in mineralogical researches related to radioactive/atomic minerals include identification of primary and secondary uranium and associated ore and gangue minerals, determination of the oxidation grade of uraninites, identification of Th, Nb, Ta, Sn, Be, Li, Zr, Hf, Ti, rare-earth elements (REE) minerals, investigations on degree of structural disordering in Nb-Ta minerals, X-ray crystallographic and substitutional solid solution studies, clay minerals, triclinicity of K-feldspar, metamict minerals and influence of the degree of metamictisation on uranium beneficiation, characterisation of leached residue, beneficiated, heat-treated pro...
Rietveld-based mineralogical quantitation of deferrified oxisol clays
Australian Journal of Soil Research, 2007
Although the mineralogical quantitative analysis of the soil clay fraction can provide useful information for the improvement of soil management practices, the quantitation of all clay components normally requires a combination of different analytical techniques, which makes this determination expensive and time-consuming. One alternative for more expeditious mineralogical quantitations consists of using the Rietveld method for the treatment of X-ray diffraction (XRD) data. In this study we evaluate the accuracy of the mineralogical quantitative analyses of oxisol deferrified clays carried out with the application of the Rietveld method to XRD data obtained for both non-spray- and spray-dried samples. Linear regression analyses were carried out for comparing the XRD-Rietveld results with those calculated from X-ray fluorescence spectroscopy (XRF) data. Correspondence was observed between the XRD-Rietveld and XRF-derived data, confirming the potential utility of the Rietveld method f...
Journal of Soils and Sediments, 2017
Purpose Brazilian soils that present extremely hard sub-superficial horizons when dry and friable when humid are similar to the Australian and South African hardsetting horizons whose hardness can be mainly related to low crystallinity. Studies involving refinement by the Rietveld method with X-ray diffraction (RM-XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and their relation have not been carried out in hardsetting horizon soils. Thus, the objective of this study is to obtain information about the kaolinite in the hardsetting horizon of a Yellow Argisol clay fraction, taking into consideration the results of isomorphic substitution, crystallite average size, and microstrains, relating them to particle image analysis regarding their morphology and size. Materials and methods Soil samples were collected in the hardsetting horizon of a Yellow Argisol in the Coastal Tablelands region, which covers the whole Brazilian Northeast coast and part of the Southeast region. The sample was powdered, sieved, and submitted to dispersion and physical fractioning process by sedimentation. The clay fraction was analyzed by RM-XRD, AFM, and SEM techniques. Results and discussion The RM-XRD provided improvement of indices with isomorphic substitutions in the goethite [Fe 0.70 Al 0.30 O(OH)], kaolinite [Al 1.44 Fe 0.56 Si 2 O 5 (OH) 4 ], and halloysite [Al 1.42 Fe 0.58 Si 2 O 5 (OH) 4 ]; 29 nm crystallite average size; 5 × 10 −3 microstrain; and 49.5% kaolinite. AFM analyses indicated particle average size from 80 to 250 nm and average height from 60 to 80 nm. By relating this data, it was possible to estimate that the particles under analysis are kaolinite composed of 3 to 9 crystallites and stacking of 88 to 112 layers. Conclusions The process, analyses, and comparisons such as crystallographic and morphologic information about the kaolinite mineral particles contribute to the comprehension of the hardsetting horizon soil nature as well as other soils that present minerals with a high degree of isomorphic substitution.
Identification of Clay Minerals and Micas in Sedimentary Rocks
2005
Real possibilities of FTIR-spectroscopy application along with thermal analysis (TG/DTA) for examining clay minerals in rocks are presented. These methods were used for determination of mineral composition in sedimentary rock samples from the shaft No.4 Frenstat -West, Northern Moravia, CZ. Previously, the samples representing the basic clay mineral specimen were investigated by means of the following methods. In order to provide an adequate characterization of these samples, X-ray diffraction and X-ray fluorescence spectroscopy were utilized. As the individual clay minerals often occur in a form of mixed-layer clay minerals with various ratios of individual components, IR spectra and TG/DTA curves of mixtures (either natural or synthetic) were recorded, too. Clay minerals represented mainly by fine-crystalline illite (muscovite) with traces of kaolinite were predominant. Besides, carbonates (calcite, ankerite) and silica minerals occured in these samples, too. A presence of pyrites...