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The x-ray identification and crystal structures of clay minerals
01 Jan 1961-
About: The article was published on 1961-01-01 and is currently open access. It has received 966 citations till now. The article focuses on the topics: Clay minerals.
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TL;DR: The boundary between the last two geological epochs, the Pleistocene and the Holocene, is placed at the date 10,000 B.P., measured in radiocarbon years as discussed by the authors.
Abstract: The boundary between the last two geological epochs, the Pleistocene and the Holocene, is placed at ‘the date 10,000 B.P., measured in radiocarbon years’. In the European chronostratigraphy, this corresponds to the Younger Dryas/Preboreal boundary, the pollen zone III/IV boundary and the Late Glacial/Postglacial boundary. The stratal sequence in the Botanical Garden of Gothenburg is proposed as a suitable boundary-stratotype of the Pleistocene/Holocene that fulfils the stratigraphical rules of marine environment and accessibility. A core, labelled B 873, has been analyzed for multiple parameters by various authors. The suggested Pleistocene/Holocene boundary in Core B 873 is indicated by a lithologic boundary, a palynological change tentatively correlated with the pollen zone III/IV boundary, and a distinct palaeomagnetic intensity maximum, the ‘Galon Magnetic Intensity Maximum’, identified in numerous other cores at the Younger Dryas/Preboreal boundary and at the drainage of the Baltic Ice Lake in varved clay sequences (with the peak dated at the drainage ±4 varves). This boundary is closely radiocarbon dated at 10,000 B.P. (10,000–9950 B.P.) in terrestrial-lacustrine sequences within the proposed type area in Gothenburg and in Southern Sweden, the established type region for the Pleistocene/Holocene boundary. The corresponding varve date is 9965 varves B.P. (De Geer's varve –1073). The various parameters directly and indirectly connected with the study of Core B 873 make global correlations possible. Because every region has its own local characteristics, however, it will be necessary to establish regional type sections, hypostratotypes.
35 citations
TL;DR: In this paper, the first finding of berthierine and chamosite in Mexico was reported, and the identification of magnetite nanoparticles supports the hypothesis of a marine environment, specifically exhalative sedimentary (SEDEX) for the berthierines.
Abstract: We report the first finding of berthierine and chamosite in Mexico. They occur in the iron-ore deposit of Pena Colorada, Colima. Their genetic characteristics show two different mineralization events associated mainly to the magnetite ore. Berthierine is an Fe-rich and Mg-low 1:1 layer phyllosilicate of hydrothermal sedimentary origin. Its structure is 7 A, dhkl [10 0] basal spacing and low degree structural ordering. The phyllosilicate has been identified by a lack of 14 A basal reflection on X-ray diffraction (XRD) patterns. These data were supported by High Resolution Transmision Electron Microscopy (HRTEM) images that show thick packets of berthierine in well defined parallel plates. From the analysis of Fast Fourier Transform (FFT), we found around [1 0 0] reflections of berhierine 7.12 A and corresponding angles of hexagonal crystalline structure. Berthierine has a microcrystalline structure, dark green color, and high refraction index (1.64 to 1.65). Birefringence is low, near 0.007 to null and it is associated to nanoparticles (<15 nm) and microparticles of magnetite (<25 μm), fine grain siderite, and organic matter. Its texture is intergranular-interstratified with colloform banding. The chamosite Mg-rich is of hydrothermal epigenetic origin affected by low-degree metamorphism. It is an Fe-rich 2:1 layer silicate, with basal space of 14 A, dhkl [0 0 1]. The chamosite occurs as lamellar in sizes ranging from 50 to 150 μm. It has intense green color and refraction index from 1.64 to 1.65. The birefringence is near 0.008, with biaxial (-) orientation and a 2V small. It is associated mainly to sericite, epidote, clay, feldspar, and magnetite. Chamosite is emplaced in open spaces filling and linings. Mossbauer spectra of berthierine and chamosite are similar. They show the typical spectra of paramagnetic substances, with two well defined unfoldings corresponding to the oxidation state of Fe+2 and Fe+3. Chemical composition of both minerals was obtained by an electron probe X-ray micro-analyzer (EPMA). The radio Fe+Mg+Mn vs Si and Al show similar chemical compositions and different XRD patterns in the crystalline structure provoked by the environmental conditions of emplacement. A hydrothermal environment was predominant, occurring before, during, and after the magnetite mineralization. The identification of magnetite nanoparticles supports the hypothesis of a marine environment, specifically exhalative sedimentary (SEDEX) for the berthierine.
34 citations
Cites methods from "The x-ray identification and crysta..."
...Using the heating method (Brindley, 1961; Carroll, 1970), we observed that chamosite did not collapse at 550◦C, the chlorite value d=14 Å increased, and d=7 Å decreased (Fig....
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TL;DR: In this article, homoionic-montmorillonites were characterized by interlayer spacing measurements and the surface area of the Montmorillonite, before and after being saturated with Na+, K+, H+, Ca2+ and Al3+ ions, to analyse their O2, N2, CO, CH4, C2H2 and CO2 gas retentions at 25°C and 0.1 MPa.
34 citations
TL;DR: In this article, the X-ray diffraction patterns were well defined, showing δ-alumina and α-chromia as major phases, and θ- alumina as a minor phase.
Abstract: Pure and mixed aluminium and chromium oxides have been prepared by passage of the halides through a radio-frequency oxidising plasma. The nature of the materials produced has been assessed by electron microscopy, electron diffraction, X-ray diffraction, magnetic susceptibility, and electron spin resonance. The products ware finely divided solids, containing mostly spherical particles in the size ranga 0.01 to 0.15μm; however, the chromia particles were often hexagonal platelets up to 0.4μm in diameter. The X-ray diffraction patterns were well defined, showingδ-alumina andα-chromia as major phases, andθ-alumina as a minor phase. The maximum degree of solid solution of chromium ions in theδ-alumina was limited to about 6% of the total cation content; solid solution of aluminium ions in theα-chromia phase was below the detection limit of 10%. The nature of the particles, the phases produced, and the degree of solid solution are shown to be consistent with a sequence of condensation which can be predicted from thermodynamic data.
34 citations
Journal Article•
TL;DR: A natural mineral from Santa Marta-Colombia used as the starting material in the synthesis of pillared clays has been characterized by several techniques, including X-ray diffraction, Xray fluorescence, electronic paramagnetic resonance, aluminum nuclear magnetic resonance and scanning electron microscopy as discussed by the authors.
Abstract: A natural mineral from Santa Marta-Colombia used as the starting material in the synthesis of pillared clays has been characterized by several techniques, including X-ray diffraction, X-ray fluorescence, electronic paramagnetic resonance, aluminum nuclear magnetic resonance and scanning electron mi croscopy. The information revealed that the mineral corresponds to trioctahedral vermiculite.The identification of this mineral is valuable in the control of reductioncharge and pillaring processes on thesematerials to obtain more complex solids like the ones required to specific catalytic applications.
33 citations