TY - JOUR
T1 - Back-transformation mechanisms of ringwoodite and majorite in an ordinary chondrite
AU - Fukimoto, Kanta
AU - Miyahara, Masaaki
AU - Sakai, Takeshi
AU - Ohfuji, Hiroaki
AU - Tomioka, Naotaka
AU - Kodama, Yu
AU - Ohtani, Eiji
AU - Yamaguchi, Akira
N1 - Funding Information:
Lin Y., an anonymous reviewer, and associated editor Kevin R. are acknowledged for their comments that improved an earlier version of this manuscript. This study was supported by Grants-in-Aid for Scientific Research, nos 15H05748 and 18H01269, from the Ministry of Education, Culture Sports, Science and Technology (MEXT) to E.O. and M.M., respectively. This study was also financially supported by NIPR through General Collaboration Projects nos 26-31 and KP-307. Parts of the FE-SEM and Raman experiments were supported by the Joint Usage/Research Center at the Premier Research Institute for Ultrahigh-pressure Sciences (PRIUS), Ehime University.
Funding Information:
Lin Y., an anonymous reviewer, and associated editor Kevin R. are acknowledged for their comments that improved an earlier version of this manuscript. This study was supported by Grants‐in‐Aid for Scientific Research, nos 15H05748 and 18H01269, from the Ministry of Education, Culture Sports, Science and Technology (MEXT) to E.O. and M.M., respectively. This study was also financially supported by NIPR through General Collaboration Projects nos 26‐31 and KP‐307. Parts of the FE‐SEM and Raman experiments were supported by the Joint Usage/Research Center at the Premier Research Institute for Ultrahigh‐pressure Sciences (PRIUS), Ehime University.
Publisher Copyright:
© The Meteoritical Society, 2020.
PY - 2020/8/1
Y1 - 2020/8/1
N2 - We investigated the back-transformation mechanisms of ringwoodite and majorite occurring in a shock-melt vein (SMV) of the Yamato 75267 H6 ordinary chondrite during atmospheric entry heating. Ringwoodite and majorite in the shock melt near the fusion crust have back-transformed into olivine and enstatite, respectively. Ringwoodite (Fa~18) occurs in the SMV as a fine-grained polycrystalline assemblage. Approaching the fusion crust, fine-grained polycrystalline olivine becomes dominant instead of ringwoodite. The back-transformation from ringwoodite to olivine proceeds by incoherent nucleation and by an interface-controlled growth mechanism: nucleation occurs on the grain boundaries of ringwoodite, and subsequently olivine grains grow. Majorite (Fs16–17En82–83Wo1) occurs in the SMV as a fine-grained polycrystalline assemblage. Approaching the fusion crust, the majorite grains become vitrified. Approaching the fusion crust even more, clino/orthoenstatite grains occur in the vitrified majorite. The back-transformation from majorite to enstatite is initiated by the vitrification, and growth continues by the subsequent nucleation in the vitrified majorite.
AB - We investigated the back-transformation mechanisms of ringwoodite and majorite occurring in a shock-melt vein (SMV) of the Yamato 75267 H6 ordinary chondrite during atmospheric entry heating. Ringwoodite and majorite in the shock melt near the fusion crust have back-transformed into olivine and enstatite, respectively. Ringwoodite (Fa~18) occurs in the SMV as a fine-grained polycrystalline assemblage. Approaching the fusion crust, fine-grained polycrystalline olivine becomes dominant instead of ringwoodite. The back-transformation from ringwoodite to olivine proceeds by incoherent nucleation and by an interface-controlled growth mechanism: nucleation occurs on the grain boundaries of ringwoodite, and subsequently olivine grains grow. Majorite (Fs16–17En82–83Wo1) occurs in the SMV as a fine-grained polycrystalline assemblage. Approaching the fusion crust, the majorite grains become vitrified. Approaching the fusion crust even more, clino/orthoenstatite grains occur in the vitrified majorite. The back-transformation from majorite to enstatite is initiated by the vitrification, and growth continues by the subsequent nucleation in the vitrified majorite.
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U2 - 10.1111/maps.13543
DO - 10.1111/maps.13543
M3 - Article
AN - SCOPUS:85088580161
SN - 1086-9379
VL - 55
SP - 1749
EP - 1763
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
IS - 8
ER -