Tracking silica in Earth's upper mantle using new sound velocity data for coesite to 5.8 GPa and 1073 K

Abstract

The compressional and shear wave velocities for coesite have been measured simultaneously up to 5.8 GPa and 1073 K by ultrasonic interferometry for the first time. The shear wave velocity decreases with pressure along all isotherms. The resulting contrasts between coesite and stishovite reach ~34% and ~45% for P and S wave velocities, respectively, and ~64% and ~75% for their impedance at mantle conditions. The large velocity and impedance contrasts across coesite‐stishovite transition imply that to generate the velocity and impedance contrasts observed at the X‐discontinuity, only a small amount of silica would be required. The velocity jump dependences on silica, d(lnVP)/d(SiO2) = 0.38 (wt %)−1 and d(lnVS)/d(SiO2) = 0.52 (wt %)−1, are utilized to place constraints on the amount of silica in the upper mantle and provide a geophysical approach to track mantle eclogite materials and ancient subducted oceanic slabs.

An Extended Semianalytical Approach for Thermoelasticity of Monoclinic Crystals: Application to Diopside

“…Elastic properties of minerals at high pressure and temperature (PT) are essential for constraining the chemical composition and dynamics of the Earth's interior. In spite of great advancements in high-pressure experimental techniques, it is still a considerable challenge to measure the elasticity of minerals at the conditions of the Earth's deep mantle (e.g., Bass et al, 2008;Chen et al, 2017;Li & Liebermann, 2007;Li et al, 2016). Elastic coefficients at high PT can also be obtained by ab initio quasi-harmonic (QHA; e.g., Karki et al, 1999;Wentzcovitch et al, 2004Wentzcovitch et al, , 2006 and ab initio molecular dynamics simulation (e.g., Oganov et al, 2001).…”

The Birth of Mineral Physics at the ANU in the 1970s

“…In the most recent collaboration between the ANU and Stony Brook, Ting Chen and her colleagues measured the sound velocities of polycrystalline coesite at high pressure and temperature in Baosheng Li's laboratory [40] using a specimen hot-pressed by the author in a girdle-anvil apparatus in 1975, and so very "well-aged" [23]. As part of her doctoral research at the ANU, Jennifer Kung spent six months at Stony Brook on the synthesis of polycrystalline specimens of ScAlO 3 -perovskite with the aid of Gabriel Gwanmesia [36,37].…”

“…(Ted) Ringwood who offered me a research position at the ANU in 1970 and provided technical support and scientific advice over the ensuing 6 years (and, only in exceptional cases, requested to be a co-author). I am grateful to Alan Major, Bill Hibberson and Doug Mayson for their technical contributions to our ultrasonic laboratory and to Ian Jackson and Leonie In the most recent collaboration between the ANU and Stony Brook, Ting Chen and her colleagues measured the sound velocities of polycrystalline coesite at high pressure and temperature in Baosheng Li's laboratory [40] using a specimen hot-pressed by the author in a girdle-anvil apparatus in 1975, and so very "well-aged" [23].…”

My Career as a Mineral Physicist at Stony Brook: 1976–2019

“…Energy (such as Brookhaven National Lab) [45]; (b) Three Chinese women who were working with my colleague Baosheng Li (Professor in the Department of Geosciences) on projects to utilize ultrasonic interferometry in conjunction with synchrotron X-radiation to measure sound velocities of minerals at high pressures and temperatures [46][47][48]. All six of these graduate students took my Solid-State Geophysics course in the Fall 2013 semester (see Figure 14), which was my last semester of teaching at Stony Brook as I formally retired in 2014 and was then appointed as a Research Professor in the Department of Geosciences and the Mineral Physics Institute.…”

“…All six of these graduate students took my Solid-State Geophysics course in the Fall 2013 semester (see Figure 14), which was my last semester of teaching at Stony Brook as I formally retired in 2014 and was then appointed as a Research Professor in the Department of Geosciences and the Mineral Physics Institute. velocities of minerals at high pressures and temperatures [46][47][48]. All six of these graduate students took my Solid-State Geophysics course in the Fall 2013 semester (see Figure 14), which was my last semester of teaching at Stony Brook as I formally retired in 2014 and was then appointed as a Research Professor in the Department of Geosciences and the Mineral Physics Institute.…”