Structural behavior of Al3+ in peralkaline, metaluminous, and peraluminous silicate melts and glasses at ambient pressure
-
Bjorn O. Mysen
and
Michael J. Toplis
Abstract
Peralkaline and peraluminous glasses close to the metaluminous join in the systems Na2O-Al2O3-SiO2 (NAS), CaO-Al2O3-SiO2 (CAS), and MgO-Al2O3-SiO2 (MAS) have been examined with Raman spectroscopy. At least three different SiO2 contents in each of the systems (NAS, CAS, and MAS) have been studied. Each series of glasses spans the metaluminous join at constant silica content. The spectra of glasses in all three systems show changes consistent with a continuous decrease in abundance of depolymerized species and an increase in fully polymerized species as compositions change from peralkaline to peraluminous. There is no evidence for maxima or minima of these abundances across the metaluminous joins for any of the studied series. These observations confirm previous suggestions that non-bridging O atoms are a general feature of .fully polymerized. glasses, and that a population of Al exists in the melt structure that is not associated with a charge-balancing cation, even in peralkaline compositions.
With decreasing peralkalinity, new components appear in the Raman spectra of peraluminous NAS and CAS glasses, but such changes are much less obvious in the MAS system. These additional components are most likely related to the presence of “excess” Al (i.e., Al not associated with a chargebalancing cation). The structural role of this “excess” Al could be in the form of (Al, Si)-triclusters with different Al/Si-ratios depending on composition, but simple distorted AlO4-tetrahedra and possibly higher-coordinate Al3+ cannot be ruled out from the Raman spectra alone. The implications of these results for isothermal variations in viscosity are considered. It is concluded that the diversity and complexity of viscosity variations observed in different aluminosilicate systems may be a consequence of the fact that the difference in bond strength between bridging and non-bridging O atoms in the Ca and Mg-bearing systems is small compared to that in the Na-bearing system.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Single-crystal FTIR and X-ray study of vishnevite, ideally [Na6(SO4)][Na2(H2O)2](Si6Al6O24)
- Crystallographic texture and microstructure of terebratulide brachiopod shell calcite: An optimized materials design with hierarchical architecture
- High-temperature phase relations and topological constraints in the quaternary system MgO-Al2O3-SiO2-Cr2O3: An experimental study
- Tilt and buckling modes, and acoustic anisotropy in layers with post-perovskite connectivity
- Optical absorption study of natural garnets of almandine-skiagite composition showing intervalence Fe2+ + Fe3+ → Fe3+ + Fe2+ charge-transfer transition
- Deriving formation constants for aqueous metal complexes from XANES spectra: Zn2+ and Fe2+ chloride complexes in hypersaline solutions
- Birnessite polytype systematics and identiÞ cation by powder X-ray diffraction
- Improved measurement of fission-track annealing in apatite using c-axis projection
- Improved modeling of fission-track annealing in apatite
- Intercalibration of FTIR and SIMS for hydrogen measurements in glasses and nominally anhydrous minerals
- Order and miscibility in the otavite–magnesite solid solution
- An infrared investigation of the otavite-magnesite solid solution
- Partitioning of calcium, magnesium, and transition metals between olivine and melt governed by the structure of the silicate melt at ambient pressure
- The geometric effects of VFe2+ for VMg substitution on the crystal structures of the grandidierite-ominelite series
- The iron oxidation state of garnet by electron microprobe: Its determination with the flank method combined with major-element analysis
- Gram-Charlier development of the atomic displacement factors into mineral structures: The case of samsonite, Ag4MnSb2S6
- Superstructure of Challis mordenite with doubled monoclinic unit cell
- Biopyribole evolution during tremolite synthesis from dolomite and quartz in CO2-H2O fluid
- The evolution of diamond morphology in the process of dissolution: Experimental data
- The pearceite-polybasite group of minerals: Crystal chemistry and new nomenclature rules
- Determination of layer stacking microstructures and intralayer transition of illite polytypes by high-resolution transmission electron microscopy (HRTEM)
- Structural behavior of Al3+ in peralkaline, metaluminous, and peraluminous silicate melts and glasses at ambient pressure
- The crystal structure of ingersonite, Ca3Mn2+Sb45+O14, and its relationships with pyrochlore
- Chemical composition, statistical analysis of the unit cell, and electrostatic modeling of the structure of Al-saturated chlorite from metamorphosed rocks
- XANES study of the oxidation state of Cr in lower mantle phases: Periclase and magnesium silicate perovskite
- Crystal chemistry of hydration in aluminous orthopyroxene
