Spectroscopic and structural properties of synthetic micas on the annite-siderophyllite binary: Synthesis, crystal structure refinement, Mössbauer, and infrared spectroscopy
-
Günther J. Redhammer
,
Anton Beran
Abstract
The effect of the incorporation of Al-Tschermak’s molecule to the trioctahedral potassium mica annite {K}[Fe3]<AlSi3>O10(OH)2 on local and average structure has been investigated by hydrothermal synthesis, structure refinement of X-ray powder diffraction data, Mössbauer and infrared spectroscopy. The various types of brackets indicate different structural sites. Samples with compositions {K}[Fe3-xAlx]<Al1+xSi3-x>O10(OH)2 were prepared by hydrothermal techniques. The maximum solubility of Al3+ is limited to x = 0.92 at 500 °C and to x = 0.82 at 700 °C. The main factor controlling the substitution limits is the ditrigonal distortion of the tetrahedral rings. Lattice parameters decrease linearly with increasing Al3+ content of the mica. A considerable decrease of M2-O and nearly no change of M1-O bond lengths with increasing Al3+ contents is indicative of preferred occupation of the M2 site by [Al3+]. Changes in K-O distances are also very pronounced and reflect the ditrigonal distortion of the tetrahedral sheet. The bimodal ferrous quadrupole splitting distribution (QSD) in annite, extracted from Mössbauer spectra, becomes narrower and more centered around 2.60 mm/s with increasing Al3+ contents, and its evolution suggests an increasing deviation from ideal octahedral coordination of Fe by O, illustrated by the increasing octahedral flattening angle y. The population of individual QSD components proves that it is impossible to resolve cis and trans M-sites in micas by Mössbauer spectroscopy. In the hydroxyl stretching region, up to 7 bands are observed in the infra-red spectra which correspond to OH groups adjacent to 3 Fe2+ (N-bands), to OH groups coordinated by Fe2+, Al3+, and Fe3+ (I-bands) and to configurations having one octahedral vacancy (V-bands). N- and I-type bands are shifted toward lower wavenumbers with increasing Al3+ content because of increasing OH···Otet interactions.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Iron concentration and the physical processes of dynamic oxidation in an alkaline earth aluminosilicate glass
- A crystal chemical re-evaluation of amphibole/melt and amphibole/clinopyroxene DTi values in petrogenetic studies
- Mineralogy of mafic xenoliths and their reaction zones in the olivine lamproite from Prairie Creek Arkansas and the paragenesis of haggertyite, Ba [Fe6Ti5Mg]O19
- Magmatic anhydrite in granitic rocks: First occurrence and potential petrologic consequences
- Crystal chemistry of Al-rich biotites coexisting with muscovites in peraluminous granites
- Spectroscopic and structural properties of synthetic micas on the annite-siderophyllite binary: Synthesis, crystal structure refinement, Mössbauer, and infrared spectroscopy
- Thermodynamic properties of tremolite: A correction and some comments
- Raman spectroscopic characteristics of Mg-Fe-Ca pyroxenes
- Hydrogen in diopside: Diffusion profiles
- Diffusion of C and O in calcite at 100 MPa
- Solubility and stability of zeolites in aqueous solution: II. Calcic clinoptilolite and mordenite
- TEM and SFM of exsolution and twinning in an alkali feldspar
- Equation of state of magnetite and its high-pressure modification: Thermodynamics of the Fe-O system at high pressure
- Optimization of site occupancies in minerals using quadratic programming
- Leverage analysis and structure refinement of minerals
- The absolute energy positions of conduction and valence bands of selected semiconducting minerals
- Antiferroelectric phase transition in titanite: Excess entropy and short range order
- P4/n and P4nc long-range ordering in low-temperature vesuvianites
- Tetrahedral vacancies and cation ordering in low-temperature Mn-bearing vesuvianites: Indication of a hydrogarnet-like substitution
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- The crystal structure of peprossiite-(Ce), an anhydrous REE and Al mica-like borate with square-pyramidal coordination for Al
- Crystal chemistry of the new mineral brandholzite, Mg(H2O)6[Sb(OH)6]2, and of the synthetic analogues M2+(H2O)6[Sb(OH)6]2 (M2+ = Mg, Co)
- Letters. In-situ Raman spectra of dissolved silica species in aqueous fluids to 900 °C and 14 kbar
- Quetzalcoatlite: A new octahedral-tetrahedral structure from a 2 × 2 × 40 μm3 crystal at the Advanced Photon Source-GSE-CARS Facility
- Bonding and dynamics of Mg in pyrope: a theoretical investigation
- Structure of a new Al-rich phase, [K, Na]0.9[Mg, Fe]2[Mg, Fe, Al, Si]6O12, synthesized at 24 GPa
- Core level electron binding energies of realgar (As4S4)
- Oxidation of {100} and {111} surfaces of pyrite: Effects of preparation method
