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Elastic moduli of rock glasses under pressure to 8 kilobars and geophysical implications.

Journal of Geophysical Research

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Abstract

Shear and longitudinal velocities were measured by the ultrasonic phase comparison method as a function of pressure to 8 kbar on synthetic glasses of basalt, andesite, rhyolite, and quartz composition and on natural obsidian. Velocities of most of the glasses decrease anomalously with pressure, but increasingly more-normal behavior occurs with decrease in SiO2 content. The pressure derivatives of rigidity and bulk modulus increase linearly, from -3.39 to -0.26 and from -5.91 to +2.09, respectively, with decrease in SiO2 content from 100 to 49%. The change from negative to positive in the pressure derivatives of both moduli and observed at Poisson's ratio of about 0.25 is consitent with the Smyth model for the anomalous elastic behavior of glass. If the temperature in the upper mantle is about 1500oC, tholeiitic basalt would be molten in accordance with the partial melt explanation for the low-velocity zone; at 1300oC and below, basalt would be in the glassy state, especially if more felsic than tholeiite. -Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Elastic moduli of rock glasses under pressure to 8 kilobars and geophysical implications.
Series title:
Journal of Geophysical Research
Volume
85
Issue:
B11
Year Published:
1980
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research
First page:
6461
Last page:
6470
Number of Pages:
10