A Strength Softening Phase Transition Observed in Shocked (Mg0.92,Fe0.08)SiO3 Perovskite at About 83GPa
HE Lin1,2, GONG Zi-Zheng1, JING Fu-Qian 1,3
1Institute of High Pressure Physics, Southwest Jiaotong University, Chengdu 6100312College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 6100663Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, China Academy of Engineering Physics, PO Box 919-111, Mianyang 621900
A Strength Softening Phase Transition Observed in Shocked (Mg0.92,Fe0.08)SiO3 Perovskite at About 83GPa
HE Lin1,2;GONG Zi-Zheng1;JING Fu-Qian 1,3
1Institute of High Pressure Physics, Southwest Jiaotong University, Chengdu 6100312College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 6100663Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, China Academy of Engineering Physics, PO Box 919-111, Mianyang 621900
摘要We report the experimental data of Hügoniot longitudinal sound velocity VL for natural (Mg0.92,Fe0.08)SiO3 enstatite sample at about 40--140GPa, consisting of three new data and five previously reported data but revised by our new Hügoniot equation of state parameters. Three segments, separated by two discontinuities, appear in the VL--pH (shock pressure) plot. Analyses show that the first discontinuity at about 64GPa, with a sharp increase of VL of about 21%, is judged to be a phase transition from enstatite to Pbnm perovskite (PV); while the second one at about 83GPa, with a dramatic decrease of VL of about 23%, is likely caused by a subtle structural change from Pbnm PV to tetragonal PV, accompanied by material strength softening due to melting of oxygen sublattices. This strength softening evidence is obtained first from shock wave experiments, and probably has profound implications for probing into the origin of low seismic velocity anomaly in the Earth's lower mantle and thus constraining the geophysical and geochemical models for the Earth's lower mantle.
Abstract：We report the experimental data of Hügoniot longitudinal sound velocity VL for natural (Mg0.92,Fe0.08)SiO3 enstatite sample at about 40--140GPa, consisting of three new data and five previously reported data but revised by our new Hügoniot equation of state parameters. Three segments, separated by two discontinuities, appear in the VL--pH (shock pressure) plot. Analyses show that the first discontinuity at about 64GPa, with a sharp increase of VL of about 21%, is judged to be a phase transition from enstatite to Pbnm perovskite (PV); while the second one at about 83GPa, with a dramatic decrease of VL of about 23%, is likely caused by a subtle structural change from Pbnm PV to tetragonal PV, accompanied by material strength softening due to melting of oxygen sublattices. This strength softening evidence is obtained first from shock wave experiments, and probably has profound implications for probing into the origin of low seismic velocity anomaly in the Earth's lower mantle and thus constraining the geophysical and geochemical models for the Earth's lower mantle.
(Structure of the Earth's interior below the upper mantle)
引用本文:
HE Lin;GONG Zi-Zheng;JING Fu-Qian;. A Strength Softening Phase Transition Observed in Shocked (Mg0.92,Fe0.08)SiO3 Perovskite at About 83GPa[J]. 中国物理快报, 2008, 25(1): 332-335.
HE Lin, GONG Zi-Zheng, JING Fu-Qian,. A Strength Softening Phase Transition Observed in Shocked (Mg0.92,Fe0.08)SiO3 Perovskite at About 83GPa. Chin. Phys. Lett., 2008, 25(1): 332-335.
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