The effect of temperature

Amer. Mineral.,
84, 1336-1345, 1999

The effect of temperature and bulk composition on the solution mechanism of phosphorus in peraluminous haplogranitic magma

B. O. Mysen +,
F. Holtz # *,
M. Pichavant #,
J.-M. Beny # and
J.-M. Montel ##

+ Geophysical Laboratory and Center for High Pressure Research, Carnegie Instn. Washington, 5251 Broad Branch Rd., NW, Washington DC 20015-1305, USA,

# CRSCM-CNRS, 1a, rue de la Ferollerie, 45071 Orleans, France

## Department de Geologie, URA 10 du CNRS, Universite Blaise Pascal, 5, rue Kessler, 63038 Clermont-Ferrand, France

* Now at: Inst. Mineralogie, Univ. Hannover, Welfengarten 1, D-30167 Hannover, Germany

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 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) and 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 complexes is positively correlated with peraluminosity and P2O5 content. Increasing temperature has the same structural effect. These relationships are coupled with decreasing polymerization of the melts. The latter effect is particularly evident in the temperature range where the glasses are transformed from glass to supercooled liquid.

SCOPE OF RESEARCH INTERESTS	RESEARCH INTERESTS	CURRENT RESEARCH ACTIVITIES
ABSTRACTS (LIST)	SCIENTIFIC PUBLICATIONS

[1], [2], [3], [4],
[5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18],
[19], [20], [21], [22], [23], [24], [25]

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Email: mysen@gl.ciw.edu