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Title: Confirming a pyrolitic lower mantle using self-consistent pressure scales and new constraints on CaSiO 3 perovskite: A Pyrolitic Lower Mantle

Authors:
 [1];  [2];  [1];  [3];  [4];  [5]
  1. Laboratory of Seismology and Physics of Earth's Interior, School of Earth and Planetary Sciences, University of Science and Technology of China, Hefei China
  2. Laboratory of Seismology and Physics of Earth's Interior, School of Earth and Planetary Sciences, University of Science and Technology of China, Hefei China; National Geophysics Observatory, Mengcheng China
  3. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan China
  4. Center for Advanced Radiation Sources, University of Chicago, Chicago Illinois USA
  5. Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin Texas USA; Center for High Pressure Science and Technology Advanced Research, Shanghai China
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFFOREIGN
OSTI Identifier:
1329403
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research. Solid Earth; Journal Volume: 121; Journal Issue: 7
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Sun, Ningyu, Mao, Zhu, Yan, Shuai, Wu, Xiang, Prakapenka, Vitali B., and Lin, Jung-Fu. Confirming a pyrolitic lower mantle using self-consistent pressure scales and new constraints on CaSiO 3 perovskite: A Pyrolitic Lower Mantle. United States: N. p., 2016. Web. doi:10.1002/2016JB013062.
Sun, Ningyu, Mao, Zhu, Yan, Shuai, Wu, Xiang, Prakapenka, Vitali B., & Lin, Jung-Fu. Confirming a pyrolitic lower mantle using self-consistent pressure scales and new constraints on CaSiO 3 perovskite: A Pyrolitic Lower Mantle. United States. doi:10.1002/2016JB013062.
Sun, Ningyu, Mao, Zhu, Yan, Shuai, Wu, Xiang, Prakapenka, Vitali B., and Lin, Jung-Fu. Fri . "Confirming a pyrolitic lower mantle using self-consistent pressure scales and new constraints on CaSiO 3 perovskite: A Pyrolitic Lower Mantle". United States. doi:10.1002/2016JB013062.
@article{osti_1329403,
title = {Confirming a pyrolitic lower mantle using self-consistent pressure scales and new constraints on CaSiO 3 perovskite: A Pyrolitic Lower Mantle},
author = {Sun, Ningyu and Mao, Zhu and Yan, Shuai and Wu, Xiang and Prakapenka, Vitali B. and Lin, Jung-Fu},
abstractNote = {},
doi = {10.1002/2016JB013062},
journal = {Journal of Geophysical Research. Solid Earth},
number = 7,
volume = 121,
place = {United States},
year = {Fri Jul 01 00:00:00 EDT 2016},
month = {Fri Jul 01 00:00:00 EDT 2016}
}
  • The mineralogical constitution of the Earth's mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D" layer contains ferromagnesian silicate [(Mg,Fe)SiO 3] with nominally 10 mole percent Fe. On the basis of experiments in laser-heated diamond anvil cells, at pressures of 95 to 101 gigapascals and temperatures of 2200 to 2400 kelvin, we found that such perovskite is unstable; it loses its Fe and disproportionates to a nearly Fe-free MgSiO 3 perovskite phase and anmore » Fe-rich phase with a hexagonal structure. This observation has implications for enigmatic seismic features beyond ~2000 kilometers depth and suggests that the lower mantle may contain previously unidentified major phases.« less
  • Combined synthesis experiments and first-principles calculations show that MgSiO 3-perovskite with minor Al or Fe does not incorporate significant OH under lower mantle conditions. Perovskite, stishovite, and residual melt were synthesized from natural Bamble enstatite samples (Mg/(Fe+Mg) = 0.89 and 0.93; Al 2O 3 < 0.1 wt% with 35 and 2065 ppm wt H 2O, respectively) in the laser-heated diamond anvil cell at 1600-2000 K and 25-65 GPa. Combined Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction, and ex-situ transmission electron microscopy (TEM) analysis demonstrates little difference in the resulting perovskite as a function of initial water content. Four distinct OHmore » vibrational stretching bands are evident upon cooling below 100 K (3576, 3378, 3274, and 3078 cm -1), suggesting 4 potential bonding sites for OH in perovskite with a maximum water content of 220 ppm wt H 2O, and likely no more than 10 ppm wt H 2O. Complementary, Fe-free, first-principles calculations predict multiple potential bonding sites for hydrogen in perovskite, each with significant solution enthalpy (0.2 eV/defect). We calculate that perovskite can dissolve less than 37 ppm wt H 2O (400 ppm H/Si) at the top of the lower mantle, decreasing to 31 ppm wt H 2O (340 ppm H/Si) at 125 GPa and 3000 K in the absence of a melt or fluid phase. Here, we propose that these results resolve a long-standing debate of the perovskite melting curve and explain the order of magnitude increase in viscosity from upper to lower mantle.« less
  • Highlights: • CaSiO{sub 3}:Pr{sup 3+} was prepared by facile low temperature solution combustion method. • The crystalline phase of the product is obtained by adopting sintering method. • Samples prepared at 500 °C and calcined at 900 °C for 3 h showed β-phase. • The Pr{sup 3+} doped CaSiO{sub 3} shows “unusual results”. • The electrical microstructure has been accepted to be of internal barrier layer capacitor. - Abstract: CaSiO{sub 3} nano-ceramic powder doped with Pr{sup 3+} has been prepared by solution combustion method. The powder Ca{sub 0.95}Pr{sub 0.05}SiO{sub 3} is investigated for its dielectric and electrical properties at roommore » temperature to study the effect of doping. The sample is characterized by X-ray diffraction and infrared spectroscopy. The size of either of volume elements of CaSiO{sub 3}:Pr{sup 3+} estimated from transmission electron microscopy is about 180–200 nm. The sample shows colossal dielectric response at room temperature. This colossal dielectric behaviour follows Debye-type relaxation and can be explained by Maxwell–Wagner (MW) polarization. However, analysis of impedance and electric modulus data using Cole–Cole plot shows that it deviates from ideal Debye behaviour resulting from the distribution of relaxation times. The distribution in the relaxation times may be attributed to existence of electrically heterogeneous grains, insulating grain boundary, and electrode contact regions. Doping, thus, results in substantial modifications in the dielectric and electrical properties of the nano-ceramic CaSiO{sub 3}.« less