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Effects of chemical composition and temperature on transport properties of silica-rich glasses and melts

Anne M. Hofmeister, Alan G. Whittington, Jonas Goldsand and Reinhardt G. Criss
Effects of chemical composition and temperature on transport properties of silica-rich glasses and melts
American Mineralogist (April 2014) 99 (4): 564-577

Abstract

Combining new measurements of thermal diffusivity (D) and viscosity (eta ) of 13 silica-rich glasses and their melts with previous data reveals specific effects of Al, Ca, and Fe cations on heat and mass transport for diverse glasses and melts. We investigated rhyolites, tektites, leucogranite, haplogranite, and chemically complex commercial glasses. Highly polymerized samples, with high-Al but low-Ca contents, yield high values for eta , D, and glass transition temperatures (T (sub g,12) ), whereas less polymerized samples with high-Ca but low-Al contents, have low eta , D, and T (sub g,12) . Upon crossing the glass transition, D decreases substantially, to approximately 0.35 mm (super 2) /s for Ca-rich melts, but D decreases only weakly, to approximately 0.52 mm (super 2) /s for Al-rich melts. The magnitude of the decrease in D at T (sub g,12) correlates with the melt fragility, and also to the configurational heat capacity. High-Ca contents result in low D for glasses and melts, whether or not Al is present. At high T, theta D/theta T is positive for glasses and melts containing Fe (super 2+) , which we attribute to diffusive radiative transfer involving electronic-vibronic coupling. Thermal conductivity of all glasses increases with T, flattening out as the transition is approached. For melts with >1 wt% FeO (sub total) , theta k/theta T is positive. We predict that upon melting, I-type arc granite liquids should have lower thermal diffusivity than calcium-poor A- or S-types, and calc-alkaline basalts will have lower D than tholeiitic basalts, such that D of granitic melts is approximately 0.2 mm (super 2) s (super -2) higher than basaltic. Ferrous iron enhancing heat transport could alter the predicted order at higher temperatures.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 99
Serial Issue: 4
Title: Effects of chemical composition and temperature on transport properties of silica-rich glasses and melts
Affiliation: Washington University at St. Louis, Department of Earth and Planetary Sciences, St. Louis, MO, United States
Pages: 564-577
Published: 201404
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 55
Accession Number: 2014-030292
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables
Secondary Affiliation: University of Missouri, USA, United StatesHorton-Watkins High School, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201419
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