In situ measurements of sound velocities and densities across the orthopyroxene → high-pressure clinopyroxene transition in MgSiO3 at high pressure

Kung, Jennifer; Li, Baosheng; Uchida, Takeyuki; Wang, Yanbin; Neuville, Daniel R.; Liebermann, Robert C.

doi:10.1016/j.pepi.2004.05.008

Cited by 113 publications

(151 citation statements)

References 38 publications

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“…This is 7 consistent with the experimental observation that the high pressure OEn phase is not quenchable but gradually transforms back to OEn below 9 GPa (Lin 2003;Kung et al 2004). The failure of the MD simulation to stabilize HP-OEn2 underlines the difficulties in constructing accurate classical potentials for complex materials.…”

Section: Discussionsupporting

confidence: 90%

“…In order to compare the structural changes with experimental observations, energy dispersive x-ray diffraction patterns of the three orthoenstatites are plotted in Figure 5 together with experimental data from Kung et al (2004). For both high pressure phases, the (321) peaks merge into the (610) peak, which is in agreement with experiment (Kung et al 2004).…”

supporting

confidence: 75%

“…Kung et al (2004) observed a substantial softening of the bulk modulus above 10 GPa and before the intended transition from OEn to HP-CEn. The existence of a metastable phase was also deduced from Raman and x-ray diffraction data (Lin 2003;Lin et al 2005).…”

Section: Introductionmentioning

confidence: 87%

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High-pressure phase transitions in MgSiO3 orthoenstatite studied by atomistic computer simulation

Jahn

2008

American Mineralogist

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Molecular dynamics simulations and first principles electronic structure calculations are used to study the structural behavior of orthoenstatite, MgSiO 3 , at high pressures. The calculations suggest two possible high-pressure polymorphs of orthoenstatite, one with P2 1 ca and the other with Pbca symmetry. Both polymorphs are structurally related to orthoenstatite. Molecular dynamics simulations reveal the displacive nature of the phase transitions between the three phases. Electronic structure calculations predict a phase transition from orthoenstatite to the metastable P2 1 ca structure at 9 GPa, which may explain the anomalies in elastic and vibrational properties observed experimentally. A second metastable transition from the P2 1 ca to the high-pressure Pbca structure may be observable above 20 GPa.

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Section: Discussionsupporting

confidence: 90%

supporting

confidence: 75%

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High-pressure phase transitions in MgSiO3 orthoenstatite studied by atomistic computer simulation

Jahn

2008

American Mineralogist

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“…3 A, C, and D). Additional technical details about each element of such integrated experiments, and the wide range of experiments that can be conducted with these updated capabilities can be found in previous publications (32)(33)(34). By using these techniques, it is now possible to perform high-frequency (20-to 80-MHz) measurements of both P and S wave velocities with a precision of 0.3% on millimeter-sized polycrystalline or singlecrystal samples to pressures Ͼ20 GPa and simultaneous temperatures Ͼ1,500 K ( Fig.…”

Section: Sound Velocity Measurements At High Pressure and Temperaturementioning

confidence: 99%

Indoor seismology by probing the Earth's interior by using sound velocity measurements at high pressures and temperatures

Li¹,

Liebermann

2007

Proc. Natl. Acad. Sci. U.S.A.

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The adiabatic bulk (KS) and shear (G) moduli of mantle materials at high pressure and temperature can be obtained directly by measuring compressional and shear wave velocities in the laboratory with experimental techniques based on physical acoustics. We present the application of the current state-of-the-art experimental techniques by using ultrasonic interferometry in conjunction with synchrotron x radiation to study the elasticity of olivine and pyroxenes and their high-pressure phases. By using these updated thermoelasticity data for these phases, velocity and density profiles for a pyrolite model are constructed and compared with radial seismic models. We conclude that pyrolite provides an adequate explanation of the major seismic discontinuities at 410-and 660-km depths, the gradient in the transition zone, as well as the velocities in the lower mantle, if the uncertainties in the modeling and the variations in different seismic models are considered. The characteristics of the seismic scaling factors in response to thermal anomalies suggest that anticorrelations between bulk sound and shear wave velocities, as well as the large positive density anomalies observed in the lower mantle, cannot be explained fully without invoking chemical variations.elasticity ͉ mantle composition ͉ mantle heterogeneity ͉ ultrasonic interferometry ͉ pyrolite S eismological investigations provide the primary source of information about the properties and processes of the Earth's interior, especially for depths greater than a few hundreds of kilometers (i.e., depths below which rock samples have not yet reached the Earth's surface). In addition to regional studies that provide detailed velocity structures of the upper mantle and the transition zone, global Earth models of velocity and density profiles versus depths have been generated by compiling thousands of seismic records and data of different types, e.g., the Preliminary Earth Reference Model (1) and AK135 (2). The variations of compressional wave (P wave) and shear wave (S wave) wave velocities and densities in these models presumably reflect radial and lateral variations of chemical composition, mineralogy, pressure, and temperature. Successful interpretation of these seismic models in terms of the variables above requires experimental and theoretical information on the elasticity of Earth materials under the elevated conditions that characterize the Earth's interior. One of the petrological models that has been tested extensively in the literature is that of pyrolite, which was proposed by Ringwood (3) based on the compositions of mantle peridotites and oceanic basalts (4-8).We use the pyrolite model to compare with seismic models of both global and regional nature.Over the past 40 years or so, the elastic properties of many mantle minerals as well as their high-pressure phases have been studied by using static and shock compression and various spectroscopic techniques. Such approaches provide important information about the variation of density (hence compressibility) ...

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“…The data are in good agreement. Recently Kung et al (2004) published the results of very thorough and innovative experiments on elastic wave velocities at the orthopyroxene -HCEn transformation, as a systematic continuation of the measurements of Flesch et al (1998) with orthopyroxene up 10 GPa. Different from our experiments an OEn sample entered the HCEn-stability field at much higher pressures and temperatures of about 16 GPa/6508C.…”

Section: Clinoenstatitementioning

confidence: 99%

Simultaneous determination of elastic and structural properties under simulated mantle conditions using multi-anvil device MAX80

Mueller¹,

Lathe²,

Schilling³

2005

Advances in High-Pressure Technology for Geophysical Applications

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An ultrasonic interferometry high-pressure set-up for elastic wave velocity measurements under simulated Earth's mantle conditions has been developed. A DIA-type multi-anvil apparatus MAX80 permanently located at HASYLAB, Hamburg, Germany for X-ray diffraction (XRD) under in situ condition was equipped for simultaneous ultrasonic measurements. Two of the six anvils were equipped with lithium niobate P-and S-wave transducers of 33.3 MHz natural frequency. The pressure and temperature limits of the high-pressure apparatus were not reduced as a side effect of the modification. The ultrasonic configuration allows all kinds of interferometric measurements with compressional and shear waves. In addition to the classical ultrasonic interferometry the newly developed data transfer function technique (DTF), first described in [J. Phys. Condens. Matter 14 (2002) 11337], is discussed in detail to give the readers the chance to use this valuable and important new method.The results for natural San Carlos olivine up to 3 GPa pressure are compared with published data of several authors. The data for hot-isostatic-pressed anorthite solved discrepancies between published high-pressure and normal-pressure data for polycrystalline anorthite leading to v p ¼ 7.28 km/s, v s ¼ 3.93 km/s at ambient conditions and dv p =dp ¼ 0.027 km/s GPa, dv s =dp ¼ 0.001 km/s GPa. The obtained data sets correspond to published results within the accuracy of the method.As an example for unquenchable phase transitions we measured the elastic wave velocities at the high-pressure clinoenstatite (MgSiO 3 , HCEn) -low-pressure (LCEn) transition at high pressure, high temperature conditions in conjunction with in situ XRD. For ultrasonic interferometry experiments LCEn powder synthesized at ambient pressure was hot-isostatic-pressed at 0.4 GPa and 14008C for 2 h in MAX80 to obtain low-porosity samples. The elastic wave velocities v p and v s of the CEn sample were measured in situ using the classical interferometric technique as well as the recently developed ultrasonic data transfer function (DTF) technique for the elastic wave velocities as a function of pressure at 7008C. To compare the results, v p and v s were measured at 6.7 and 7.5 GPa using both interferometric techniques. The results correspond within the limits of less than 1%.

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In situ measurements of sound velocities and densities across the orthopyroxene → high-pressure clinopyroxene transition in MgSiO3 at high pressure

Cited by 113 publications

References 38 publications

High-pressure phase transitions in MgSiO3 orthoenstatite studied by atomistic computer simulation

High-pressure phase transitions in MgSiO3 orthoenstatite studied by atomistic computer simulation

Indoor seismology by probing the Earth's interior by using sound velocity measurements at high pressures and temperatures

Simultaneous determination of elastic and structural properties under simulated mantle conditions using multi-anvil device MAX80

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