Transport properties of high albite crystals,near-endmember feldspar and pyroxene glasses,and their melts to high temperature |
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| Authors: | Anne M Hofmeister Alan G Whittington Maik Pertermann |
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| Institution: | (1) Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA;(2) Department of Geological Sciences, University of Missouri, Columbia, MO 65201, USA;(3) Department of Earth Science, Rice University, Houston, TX 77005, USA |
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| Abstract: | Thermal diffusivity (D) was measured using laser-flash analysis (LFA) from oriented single-crystal albite and glasses near LiAlSi3O8, NaAlSi3O8, CaAl2Si2O8, LiAlSi2O6 and CaMgSi2O6 compositions. Viscosity measurements of the supercooled liquids, over 2.6 × 108 to 8.9 × 1012 Pa s, confirm strongly non-Arrhenian behavior for CaAl2Si2O8, and CaMgSi2O6, and near-Arrhenian behavior for the others. As T increases, D
glass decreases, approaching a constant near 1,000 K. Upon crossing the glass transition, D decreases rapidly. For feldspars, D for the melt is ~15% below D of the bulk crystal, whereas for pyroxenes, this difference is ~40%. Thermal conductivity (k
lat = ρC
P
D) of crystals decreases with increasing T, but k
lat of glasses increases with T because heat capacity (C
P
) increases with T more strongly than density (ρ) and D decrease. For feldspars, k
lat for the melt is ~10% below that of the bulk crystal or glass, whereas this decrease for pyroxene is ~50%. Therefore, melting
substantially impedes heat transport, providing positive thermal feedback that could promote further melting. |
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| Keywords: | Laser-flash analysis High-temperature Thermal diffusivity Viscosity Density Albite Anorthite Diopside Spodumene LiAlSi3O8 Glass Melt |
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