TY - JOUR
T1 - High-pressure polymorphs in Yamato-790729 L6 chondrite and their significance for collisional conditions
AU - Kato, Yukako
AU - Sekine, Toshimori
AU - Kayama, Masahiko
AU - Miyahara, Masaaki
AU - Yamaguchi, Akira
N1 - Funding Information:
Acknowledgments—Profs. Z. Xie and S. Jaret are acknowledged for their comments on an earlier version of this manuscript. Profs. H. Hidaka, E. Ohtani, T. Sato, Dr. M. Maeda, and Y. Shibata are acknowledged for their technical support and useful comments. We thank A.E. Christian Koeberl for his useful comments. This work was partly supported by JSPS KAKENHI Grant Number 15H05748. This study was also supported by the National Institute of Polar Research (NIPR) through General Collaboration Project no. 26–31 and KP-307.
Publisher Copyright:
© The Meteoritical Society, 2017.
PY - 2017/12
Y1 - 2017/12
N2 - Shock pressure recorded in Yamato (Y)-790729, classified as L6 type ordinary chondrite, was evaluated based on high-pressure polymorph assemblages and cathodoluminescence (CL) spectra of maskelynite. The host-rock of Y-790729 consists mainly of olivine, low-Ca pyroxene, plagioclase, metallic Fe-Ni, and iron-sulfide with minor amounts of phosphate and chromite. A shock-melt vein was observed in the hostrock. Ringwoodite, majorite, akimotoite, lingunite, tuite, and xieite occurred in and around the shock-melt vein. The shock pressure in the shock-melt vein is about 14–23 GPa based on the phase equilibrium diagrams of high-pressure polymorphs. Some plagioclase portions in the host-rock occurred as maskelynite. Sixteen different CL spectra of maskelynite portions were deconvolved using three assigned emission components (centered at 2.95, 3.26, and 3.88 eV). The intensity of emission component at 2.95 eV was selected as a calibrated barometer to estimate shock pressure, and the results indicate pressures of about 11–19 GPa. The difference in pressure between the shock-melt vein and host-rock might suggest heterogeneous shock conditions. Assuming an average shock pressure of 18 GPa, the impact velocity of the parent-body of Y-790729 is calculated to be ~1.90 km s−1. The parent-body would be at least ~10 km in size based on the incoherent formation mechanism of ringwoodite in Y-790729.
AB - Shock pressure recorded in Yamato (Y)-790729, classified as L6 type ordinary chondrite, was evaluated based on high-pressure polymorph assemblages and cathodoluminescence (CL) spectra of maskelynite. The host-rock of Y-790729 consists mainly of olivine, low-Ca pyroxene, plagioclase, metallic Fe-Ni, and iron-sulfide with minor amounts of phosphate and chromite. A shock-melt vein was observed in the hostrock. Ringwoodite, majorite, akimotoite, lingunite, tuite, and xieite occurred in and around the shock-melt vein. The shock pressure in the shock-melt vein is about 14–23 GPa based on the phase equilibrium diagrams of high-pressure polymorphs. Some plagioclase portions in the host-rock occurred as maskelynite. Sixteen different CL spectra of maskelynite portions were deconvolved using three assigned emission components (centered at 2.95, 3.26, and 3.88 eV). The intensity of emission component at 2.95 eV was selected as a calibrated barometer to estimate shock pressure, and the results indicate pressures of about 11–19 GPa. The difference in pressure between the shock-melt vein and host-rock might suggest heterogeneous shock conditions. Assuming an average shock pressure of 18 GPa, the impact velocity of the parent-body of Y-790729 is calculated to be ~1.90 km s−1. The parent-body would be at least ~10 km in size based on the incoherent formation mechanism of ringwoodite in Y-790729.
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U2 - 10.1111/maps.12957
DO - 10.1111/maps.12957
M3 - Article
AN - SCOPUS:85030256301
SN - 1086-9379
VL - 52
SP - 2570
EP - 2585
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
IS - 12
ER -