Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

P (Space and Planetary Sciences ) » P-CG Complex & General

[P-CG22] Shock responses of planetary materials elucidated from meteorites and dynamic compression experiments

Tue. May 28, 2019 1:45 PM - 3:15 PM A03 (TOKYO BAY MAKUHARI HALL)

convener:Toshimori Sekine(Center for High Pressure Science and Technology Advanced Research), Takuo Okuchi(Institute for Planetary Materials, Okayama University), Chairperson:Toshimori Sekine(HPSTAR & Osaka University), Ai-Cheng Zhang(Nanjing University)

2:30 PM - 2:45 PM

[PCG22-04] Linking occurrence and texture of dense silicate minerals in shocked meteorites with laser-shock experimental results of Mg2SiO4 analyzed by XFEL probe

*Takuo Okuchi1, Narangoo Purevjav1, Norimasa Ozaki2, Takeshi Matsuoka2, Yusuke Seto3, Yoshinori Tange4, Toshinori Yabuuchi5, Naotaka Tomioka6, Toshimori Sekine7, Ryosuke Kodama2 (1.Institute for Planetary Materials, Okayama University, 2.Graduate School of Engineering, Osaka University, 3.Graduate School of Science, Kobe University, 4.Japan Synchrotron Radiation Research Institute, 5.RIKEN Harima Branch, 6.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 7.Center for High Pressure Science and Technology Advanced Research)

Keywords:dense silicate minerals, laser shock experiments, shock metamorphism, Mg2SiO4

Primitive meteorites often show features of shock metamorphism, including occurrences of dense polymorphs of major mineral phases. By previous transmission electron microscopy studies it was demonstrated that olivine (alpha-Mg2SiO4) often had transformed into its denser polymorphs such as ringwoodite (gamma-Mg2SiO4), and as a recently-discovered new structure (epsilon-Mg2SiO4: Tomioka and Okuchi, Sci. Rep. 2017). The impact events that produced these polymorphs played essential roles in the history of early solar system evolution. Here we tried to reproduce such a dynamic transformation process starting from forsterite olivine single crystals by using very strong laser beam and x-ray free electron laser (XFEL) beam in combination at SACLA, SPring-8, Japan. A transformation process has been successfully observed with sub-nanosecond resolution by x-ray diffraction using femtosecond XFEL pulses. We discovered an ultrafast transformation process completing only within few nanoseconds, which was not expected to occur during shock metamorphism of meteorites. It can be a shear-induced fast lattice slipping proceeding without any atomic diffusion process. We conclude that formation processes and environments of some of dense Mg2SiO4 polymorphs in heavily shocked meteorites are needed to be reconsidered to involve this fast process.