TY - JOUR
T1 - Coherent and subsequent incoherent ringwoodite growth in olivine of shocked L6 chondrites
AU - Miyahara, Masaaki
AU - Ohtani, Eiji
AU - Kimura, Makoto
AU - El Goresy, Ahmed
AU - Ozawa, Shin
AU - Nagase, Toshiro
AU - Nishijima, Masahiko
AU - Hiraga, Kenji
N1 - Funding Information:
François Guyot and an anonymous reviewer are acknowledged for their constructive comments that improved an early version of this manuscript. We thank the National Institute of the Polar Research for providing us a chance to study the shocked L6 chondrite Y-791384 sample. We appreciate the help of Ito, Y. and Kawanobe, Y. for EMPA analysis. A part of this work was supported by the “Nanotechnology Support Project” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan . This study was also partly supported by the Scientific Research of Priority Area (No. 16075202 ) and grants-in-aid for the Scientific Research of MEXT (No. 18654091 and 18104009 ) to E.O. and grants-in-aid for the Scientific Research of MEXT (No. 19540500 ) to M.K. This work was conducted as a part of Tohoku University Global COE program “Global Education and Research Center for Earth and Planetary Dynamics”.
PY - 2010/6
Y1 - 2010/6
N2 - Pervasive replacement of original olivine grains by ringwoodite adjacent to a shock-melt vein of Yamato 791384L6 chondrite was observed with a FEG-SEM. In these olivines, we observed three distinct olivine-ringwoodite textures arranged in a spatially successive arrangement from the wall of the shock-melt vein into the olivine grains: (1) polycrystalline ringwoodite, (2) oriented several sets of ringwoodite lamellae and (3) oriented single lamellae. TEM images show that the polycrystalline and oriented several sets of lamellae parts consist of polycrystalline ringwoodite, indicating that phase transformation from olivine to ringwoodite is controlled by incoherent growth mechanism. On the other hand, the set of oriented single lamellae consists of thin ringwoodite platelets (<~10nm in thickness) depicting, as observed here for the first time in nature, coherent crystallographic orientation: (100)Ol//{111}Rgt. Previous TEM studies reported that only the incoherent growth mechanism was active during the transformation in the shocked chondrite. However, our TEM studies revealed evidence for formation of the coherent intracrystalline lamella growth mechanism then followed by incoherent growth in the shocked chondrite in nature, thus allowing to constrain a robust time scale of the shock and at the origin of the veins.
AB - Pervasive replacement of original olivine grains by ringwoodite adjacent to a shock-melt vein of Yamato 791384L6 chondrite was observed with a FEG-SEM. In these olivines, we observed three distinct olivine-ringwoodite textures arranged in a spatially successive arrangement from the wall of the shock-melt vein into the olivine grains: (1) polycrystalline ringwoodite, (2) oriented several sets of ringwoodite lamellae and (3) oriented single lamellae. TEM images show that the polycrystalline and oriented several sets of lamellae parts consist of polycrystalline ringwoodite, indicating that phase transformation from olivine to ringwoodite is controlled by incoherent growth mechanism. On the other hand, the set of oriented single lamellae consists of thin ringwoodite platelets (<~10nm in thickness) depicting, as observed here for the first time in nature, coherent crystallographic orientation: (100)Ol//{111}Rgt. Previous TEM studies reported that only the incoherent growth mechanism was active during the transformation in the shocked chondrite. However, our TEM studies revealed evidence for formation of the coherent intracrystalline lamella growth mechanism then followed by incoherent growth in the shocked chondrite in nature, thus allowing to constrain a robust time scale of the shock and at the origin of the veins.
KW - FIB
KW - Olivine
KW - Ringwoodite
KW - Shocked chondrite
KW - TEM
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U2 - 10.1016/j.epsl.2010.04.023
DO - 10.1016/j.epsl.2010.04.023
M3 - Article
AN - SCOPUS:77953027172
VL - 295
SP - 321
EP - 327
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
SN - 0012-821X
IS - 1-2
ER -