Abstract
We have revised the structure model of antigorite so that they conform to observations made using high-resolution transmission electron microscopy (HRTEM) images and selected-area electron diffraction. The new models retain the original half-wave configuration proposed by Kunze (1956). The Kunze model, and all subsequent research, assumes the occurrence of four- and eightmembered silicate rings in one of the two places where there are reversals of tetrahedron orientations in the tetrahedral sheets. However, TEM images at sufficiently high resolution show no traces of such rings and only half the number of octahedral-sheet offsets as occur in the Kunze model. Using our measurements and models, we generated atom positions for antigorite unit cells having various modulation lengths and then calculated the corresponding images, which provide good matches with our experimental HRTEM images. We also characterized and described antigorite structures with different modulation wavelengths and stacking sequences. Depending on the number of polyhedra in a unit cell and the presence or absence of b/3 shifts between adjoining tetrahedral and octahedral sheets, the antigorite crystals have monoclinic or triclinic symmetry, which we call antigorite-M and antigorite-T, respectively. By resolving the tetrahedral and octahedral positions, we were able to make a direct estimate of the compositions of specific antigorite samples.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Atomic-scale observations of franckeite surface morphology
- Surface control vs. diffusion control during calcite dissolution: Dependence of step-edge velocity upon solution pH
- First-principles calculation of the infrared spectrum of lizardite
- Hard-mode infrared spectroscopy of perovskites across the CaTiO3-SrTiO3 solid solution
- Spectroscopic studies of spessartine from Brazilian pegmatites
- Order/disorder in natrolite group zeolites: A 29Si and 27Al MAS NMR study
- Evolution of local electronic structure in alabandite and niningerite solid solutions [(Mn,Fe)S, (Mg,Mn)S, (Mg,Fe)S] using sulfur K- and L-edge XANES spectroscopy
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part III. Structural characterization of sub-ppm-level Gd and Mn in minerals at W-band frequency
- Experimental determination of the equilibria: rutile + magnesite = geikielite + CO2 and zircon + 2 magnesite = baddeleyite + forsterite + 2 CO2
- Symplectites derived from metastable phases in martian basaltic meteorites
- Copper speciation in vapor-phase fluid inclusions from the Mole Granite, Australia
- Trace-element partitioning between vacancy-rich eclogitic clinopyroxene and silicate melt
- Fluorite particles inducing butterfly aggregates of incipient microperthite in alkali feldspar from a syenite, the Patagonian Andes, southern Chile
- Thermal stability and spectroscopic studies of zemkorite: A carbonate from the Venkatampalle kimberlite of southern India
- Temperatures from triple-junction angles in sulfides
- Experimental determination of calcite solubility in H2O-NaCl solutions at deep crust/ upper mantle pressures and temperatures: Implications for metasomatic processes in shear zones
- Compressibility of stottite, FeGe(OH)6: An octahedral framework with protonated O atoms
- High-pressure behavior of bikitaite: An integrated theoretical and experimental approach
- Raman spectroscopic study of H2O in bikitaite: “One-dimensional ice”
- Hydrogen, lithium, and boron in mantle-derived olivine: The role of coupled substitutions
- Crystal chemistry of three tourmalines by SREF, EMPA, and SIMS
- Revised structure models for antigorite: An HRTEM study
- The structure of Mn-rich tuperssuatsiaite: A palygorskite-related mineral
- Single-crystal structure refinements and crystal chemistry of synthetic trioctahedral micas KM3(Al3+,Si4+)4O10(OH)2, where M = Ni2+, Mg2+, Co2+, Fe2+, or Al3+
- SIMS matrix effects in the analysis of light elements in silicate minerals: Comparison with SREF and EMPA data
- Letters. Equation of state of Al-bearing stishovite to 40 GPa at 300 K
- Order parameter behavior at the structural phase transition in cummingtonite from Mössbauer spectroscopy
- Deciphering Ni sequestration in soil ferromanganese nodules by combining X-ray fluorescence, absorption, and diffraction at micrometer scales of resolution
- Use of the spindle stage for orientation of single crystals for microXAS: Isotropy and anisotropy in Fe-XANES spectra
- A technique for mounting and polishing melt inclusions in small (<1 mm) crystals