HR: 0800h
AN: V41A-1350    [Abstracts]
TI: Partial Molar Volumes for Lanthanide Sesquioxides in Sodium Silicate Melts
AU: * Courtial, P
EM: courtial@min.uni-muenchen.de
AF: Department of Earth and Environmental Sciences - Ludwig-maximilians University, Theresienstrasse 41/III, Munich, 80333 Germany
AU: Dingwell, D B
EM: dingwell@lmu.de
AF: Department of Earth and Environmental Sciences - Ludwig-maximilians University, Theresienstrasse 41/III, Munich, 80333 Germany
AB: Lanthanides are of great interest in igneous petrology as trace indicators of magmatic processes that control the origin and evolution of igneous rocks. A key to the petrogenetic modelling of magmatic processes and to determine the phase diagrams of lanthanide host phases is the accurate determination of the physico-chemical and thermodynamic properties of lanthanide-containing materials, such as the volumetric properties of lanthanide-bearing silicate melts. Therefore, we have undertaken to provide a new reliable volumetric data set for lanthanide-bearing silicate melts which allows the available models in the literature to be extended to lanthanide-bearing melts. For this purpose, the densities of various lanthanide-bearing silicate melts distributed along various pseudo-binary joins, where the end-members are Na-disilicate and one of the lanthanide sesquioxides (i.e., Ce$_{2}$O$_{3}$, Pr$_{2}$O$_{3}$, Nd$_{2}$O$_{3}$, Sm$_{2}$O$_{3}$, Eu$_{2}$O$_{3}$, Gd$_{2}$O$_{3}$, Tb$_{2}$O$_{3}$, Dy$_{2}$O$_{3}$, Ho$_{2}$O$_{3}$, Er$_{2}$O$_{3}$, Tm$_{2}$O$_{3}$ and Yb$_{2}$O$_{3}$), have been measured using the double-bob Archimedean method. The present results show that the addition of any lanthanide to Na-disilicate leads to an increase in the melt density and that the melt density increases with increasing atomic number of the lanthanide. From the present density data set, the molar volumes of these melts have been calculated and the partial molar volumes of each lanthanide sesquioxide in these melts have been determined using a linear regression through each pseudo-binary join (i.e., Na-disilicate - lanthanide sesquioxide). This study indicates ideal behaviour with respect to the molar volume (i.e., a linear variation of the molar volume along each pseudo-binary join) for Na-silicate melts containing up to 10 mol% of lanthanide oxide. Comparison between the partial molar volumes of lanthanide sesquioxides obtained in this study and the molar volumes of molten lanthanide sesquioxides given in the literature raise the possibility however that this ideality is not maintained along the entire Na-disilicate - lanthanide sesquioxide pseudo-binary joins. Excess volumes of mixing appear to be required to describe the combined volumetric data set.
DE: 3630 Experimental mineralogy and petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting