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Mysen, B. O.1,
F. Holtz 2,4, M. Pichavant 2, J.-M. Beny,2
and J.-M. Montel 3 |
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1 Geophysical Laboratory
5251 Broad Branch Rd., NW
Washington, DC 20015-1305, USA
2 CRSCM-CNRS, 1a rue de la Ferollerie, 45071 Orleans,
FRANCE
3 Department de Geologie, URA 10 du CNRS, universite
Blaise Pascal, 5, rue Kessler, 63038 Clermont-Ferrand, FRANCE
4 Now at-- Inst. Mineralogie, Univ. Hanover, Welfengarten
1, D-30167 Hanover, GERMANY
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Abstract
Solution mechanisms of phosphorus in peraluminous
glasses and melts in the system CaO-Na2O-K2O-Al2O3-SiO2-P2O5 have been examined with microRaman spectroscopy,
in-situ, from ambient temperature to near 1200°C. The principal
aim was to examine relative stability of phosphate complexes
as a function of phosphorus content, peraluminosity, and temperature.
Increasing peraluminosity was accomplished by increasing Al3+ and Ca2+ proportions with constant SiO2 content. The molar ratio Al2O3/(CaO+Na2O+K2O) (A/CNK) ranged from ~1 to ~1.3.
In all compositions P5+
is bonded to Al3+
to form AlPO4 complexes.
In addition, there is evidence for pyrophosphate complexing (P2O7). In the melts with the highest (Ca+Na+K)/P, there
is probably also a small fraction of orthophosphate complexes
present. The relative importance of AlPO4-like complexes is positively correlated with peraluminosity
(A/CNK), P2O5, content, and increasing
temperature at temperatures above that of the glass transition.
These structural relationships among phosphate complexes are
coupled with decreasing polymerization of the aluminosilicate
melts.
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