Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4742681 | Physics of the Earth and Planetary Interiors | 2007 | 10 Pages |
Abstract
New, high quality data are presented on the elastic properties of β-Mg2SiO4 (wadsleyite) from 295 to 660 K at ambient pressure. Elasticity measurements were carried out on a sintered polycrystal using resonant ultrasound spectroscopy (RUS). Room temperature values for the adiabatic bulk (KS) and shear (G) moduli are 170.2(1.9) and 113.9(0.7) GPa, respectively. The KS data exhibit linear dependence on temperature (T) with (âKS/âT)P = â1.71(5) Ã 10â2 GPa Kâ1. Our result for (âKS/âT)P is consistent with a relatively high magnitude for this derivative which contrasts with â1.20 Ã 10â2 to â1.30 Ã 10â2 GPa Kâ1 reported in some earlier studies. The average (âG/âT)P = â1.57(3) Ã 10â2 GPa Kâ1 over the temperature range studied. This result is consistent with most earlier measurements of (âG/âT)P for wadsleyite. The (âKS/âT)P and average (âG/âT)P for wadsleyite over 295-660 K are not measurably affected by the presence of iron as seen from comparing our results with those from a RUS study on β-(Mg0.91Fe0.09)2SiO4. Further, our results for (âKS/âT)P and average (âG/âT)P are consistent with olivine content of 44-54% at 410-km depth in Earth, given other assumptions made in recent studies about properties of the α- and β-olivine phases for P, T conditions at that depth. Our G(T) data appear to exhibit small, but persistent, nonlinear behavior; the magnitude of (âG/âT)P increases with T. We discuss the important implications on upper mantle mineralogy if this nonlinear effect is confirmed and is demonstrated to apply when extrapolating beyond the temperature range of 295-660 K.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Donald G. Isaak, Gabriel D. Gwanmesia, Derek Falde, Michael G. Davis, Richard S. Triplett, Liping Wang,