Japan Geoscience Union Meeting 2015

Presentation information


Symbol P (Space and Planetary Sciences) » P-PS Planetary Sciences

[P-PS22] Formation and evolution of planetary materials in the solar system

Thu. May 28, 2015 2:15 PM - 4:00 PM A02 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Shoichi Itoh(Graduate school of Science, Kyoto University), Tomohiro Usui(Department of Earth and Planetary Sciences,Tokyo Institute of Technology), Yusuke Seto(Graduate School of Science, Kobe University), Masaaki Miyahara(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Makoto Kimura(Faculty of Science, Ibaraki University), Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University), Hitoshi Miura(Graduate School of Natural Sciences, Department of Information and Biological Sciences, Nagoya City University), Hikaru Yabuta(Osaka University, Department of Earth and Space Science), Chair:Masaaki Miyahara(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University)

2:45 PM - 3:00 PM

[PPS22-15] Experimental confirmation of ringwoodite crystallization from shock-induced melts

Daiki MUTOU1, *Toshimori SEKINE1, Takamichi KOBAYASHI2, Tsutomu MASHIMO3, Hiroaki OHFUJI4 (1.Hiroshima University, 2.NIMS, 3.Kumamoto University, 4.Ehime University)

Keywords:ringwoodite, shock-induced melt, crystallization, recovery shots

Many high-pressure phases have been identified in meteorites that experienced heavy collisions. The presence of high-pressure phase may provide an estimate of pressure condition. However, the dynamic formation conditions may not be equal to those at static pressures and there is no firm experimental report to indicate the ringwoodite formation at dynamic pressures, although there are Hugoniot data and trials to synthesize ringwoodite by shock compressions. We tried to confirm the ringwoodite formation by hypervelocity impacts from two powdered mixtures of biotite and cristobalite (sample A) and phlogopite and cristobalite (sample B) for Fe-rich and Mg-rich ringwoodites, respectively. When we used stainless steel containers for recovery, the container had reacted with the biotite melt to form chromite spinels. No spinel phase was observed in sample B. When we used copper containers for sample A, X-ray diffraction data on the recovered samples indicated a spinel phase (a =0.8257 nm). Because the lattice constant is greater than that of Fe2SiO4 (ahrensite) and significantly less than those of magnesioferrite and magnetite, the composition can be a Fe-rich ringwoodite. However, detailed scanning electron microscopy indicated no obvious crystals on the polished surface where there were many spherical voids. Finally the Raman spectroscopy investigations detected spectra similar to Fe-rich ringwoodite in the voids. We will try to investigate the spinel phase using analytical transmission electron microscopy.
The present experimental results confirm the formation of ringwoodite from shock-induced melts. Further studies need to provide Mg-rich ringwoodite formation and the minimum dynamic pressures required to the formation. If such experiments are extended to the other high-pressure phases present in meteorites, the shock pressure estimation will be more powerful and helpful than the present.