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Thermal diffusivity of clinopyroxenes at elevated temperature

Anne M. Hofmeister and Maik Pertermann
Thermal diffusivity of clinopyroxenes at elevated temperature
European Journal of Mineralogy (August 2008) 20 (4): 537-549

Abstract

The phonon component of thermal diffusivity (D) was measured from 8 single-crystals and 2 polycrystalline clinopyroxene samples at temperatures (T) up to a maximum of approximately 1000 to 1600 K, using laser-flash analysis. Electron microprobe analysis shows that we have two samples of near end-member diopside, two augites, one end-member and one impure jadeite, aegerine, and three near end-member spodumenes. Hydroxyl contents determined from near-IR spectroscopy range from approximately 0 to 70 ppm as H (sub 2) O. Two directions constrain D for clinopyroxenes, consistent with phonon symmetry. Anisotropy = (D (sub perpendicular c) -D (sub c) )/D (sub c) is near 40% for all samples and independent of T, where and perpendicular indicate the direction heat flows relative to the c-axis. Thermal diffusivity decreases with increasing T and approaches a constant (D (sub sat) ) near 1400 K. The temperature dependence of 1/D is well described by low-order polynomial fits. At 298 K and for near end-member compositions, cation mass and bond lengths strongly affect D (sub perpendicular c) whereas D (sub c) is essentially constant and large, 3.9 mm (super 2) s (super -1) . For solid solutions, D at 298 K decreases from end-member values as impurity content increases, but D at saturation is little affected. Excluding Li-rich clinopyroxenes, D (sub perpendicular c,sat) approximately 0.5 mm (super 2) s (super -1) and D (sub c,sat) approximately 0.9 mm (super 2) s (super -1) . The values pertain to lithospheric and mantle compositions of clinopyroxene above 1400 K, and lead to bulk thermal conductivity at saturation being 2.4 W m (super -1) K (super -1) . Pressure derivatives are predicted from models as delta (ln k)/P = 4.2 to 4.7 %GPa (super -1) .


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 20
Serial Issue: 4
Title: Thermal diffusivity of clinopyroxenes at elevated temperature
Affiliation: Washington University, Department of Earth and Planetary Sciences, St. Louis, MO, United States
Pages: 537-549
Published: 200808
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 42
Accession Number: 2008-114903
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Rice University, USA, United States
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200843
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