A strength softening phase transition observed in shocked (Mg-0.92,Fe-0.08)SiO3 perovskite at about 83 GPa

作者：He Lin^*; Gong Zi Zheng; Jing Fu Qian

来源：Chinese Physics Letters, 2008, 25(1): 332-335.

We report the experimental data of Hugoniot longitudinal sound velocity V-L for natural (Mg-0.92, Fe-0.08)SiO3 enstatite sample at about 40-140 GPa, consisting of three new data and five previously reported data but revised by our new Hugoniot 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 64 GPa, with a sharp increase of VL of about 21%, is judged to be a phase transition from enstatite to Pbmn perovskite (PV); while the second one at about 83 GPa, 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 clue 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.

• 出版日期2008-1
• 单位中国工程物理研究院; 西南交通大学; 中国工程物理研究院流体物理研究所; 四川师范大学