TY - JOUR
T1 - Elucidation of impact event recorded in the lherzolitic shergottite NWA 7397
AU - Yoshida, Masashi
AU - Miyahara, Masaaki
AU - Suga, Hiroki
AU - Yamaguchi, Akira
AU - Tomioka, Naotaka
AU - Sakai, Takeshi
AU - Ohfuji, Hiroaki
AU - Maeda, Fumiya
AU - Ohira, Itaru
AU - Ohtani, Eiji
AU - Kamada, Seiji
AU - Ohigashi, Takuji
AU - Inagaki, Yuichi
AU - Kodama, Yu
AU - Hirao, Naohisa
N1 - Funding Information:
We appreciate the very helpful comments and suggestions by Associate Editor Adrian Brearley as well as an anonymous reviewer. This study was supported by a grant-in-aid for Scientific Research, No. 18H01269 and No. 15H05748 by MEXT to M.M. and E.O., respectively. This work was supported by the Joint Usage/Research Center PRIUS, Ehime University. This work was performed under the approvals of UVSOR (S-16-MS-2006, 2023, 30-539). This study was also supported by the National Institute of Polar Research (NIPR), Japan, through General Collaboration Project no. 26-31 and KP-307.
Funding Information:
We appreciate the very helpful comments and suggestions by Associate Editor Adrian Brearley as well as an anonymous reviewer. This study was supported by a grant‐in‐aid for Scientific Research, No. 18H01269 and No. 15H05748 by MEXT to M.M. and E.O., respectively. This work was supported by the Joint Usage/Research Center PRIUS, Ehime University. This work was performed under the approvals of UVSOR (S‐16‐MS‐2006, 2023, 30‐539). This study was also supported by the National Institute of Polar Research (NIPR), Japan, through General Collaboration Project no. 26‐31 and KP‐307.
Publisher Copyright:
© 2021 The Meteoritical Society (MET)
PY - 2021/9
Y1 - 2021/9
N2 - The (plagioclase) lherzolitic shergottite Northwest Africa (NWA) 7397 consists of poikilitic and non-poikilitic lithologies. Coarse-grained low-Ca pyroxene oikocrysts enclose olivine and chromite grains in the poikilitic lithology. The major constituents of the non-poikilitic lithology are olivine, Ca-pyroxene, and plagioclase. Minor amounts of chromite, ilmenite, alkali feldspar, Ca-phosphate, and iron-sulfide are included in the non-poikilitic lithology. Most plagioclase grains in the non-poikilitic lithology have become maskelynite. A melt pocket occurs in the non-poikilitic lithology. Plagioclase in contact with the melt pocket has dissociated into zagamiite + stishovite. Apatite and merrillite entrained in the melt pocket have transformed into tuite. Olivine in contact with the melt pocket has dissociated into bridgmanite (almost vitrified) + ferroan-periclase. Alteration products, iron oxides and hydroxides, also occur in the dissociated olivine although it is not clear when the aqueous alteration occurred. The dissociation reactions of olivine and plagioclase into the high-pressure polymorphs (bridgmanite, ferroan-periclase, zagamiite, and stishovite) are found from lherzolitic shergottites for the first time. The estimated peak shock-pressure and -temperature conditions recorded in melt pockets of NWA 7397 are ˜23 GPa and 2,000 °C at least, respectively, based on the high-pressure mineral assemblages.
AB - The (plagioclase) lherzolitic shergottite Northwest Africa (NWA) 7397 consists of poikilitic and non-poikilitic lithologies. Coarse-grained low-Ca pyroxene oikocrysts enclose olivine and chromite grains in the poikilitic lithology. The major constituents of the non-poikilitic lithology are olivine, Ca-pyroxene, and plagioclase. Minor amounts of chromite, ilmenite, alkali feldspar, Ca-phosphate, and iron-sulfide are included in the non-poikilitic lithology. Most plagioclase grains in the non-poikilitic lithology have become maskelynite. A melt pocket occurs in the non-poikilitic lithology. Plagioclase in contact with the melt pocket has dissociated into zagamiite + stishovite. Apatite and merrillite entrained in the melt pocket have transformed into tuite. Olivine in contact with the melt pocket has dissociated into bridgmanite (almost vitrified) + ferroan-periclase. Alteration products, iron oxides and hydroxides, also occur in the dissociated olivine although it is not clear when the aqueous alteration occurred. The dissociation reactions of olivine and plagioclase into the high-pressure polymorphs (bridgmanite, ferroan-periclase, zagamiite, and stishovite) are found from lherzolitic shergottites for the first time. The estimated peak shock-pressure and -temperature conditions recorded in melt pockets of NWA 7397 are ˜23 GPa and 2,000 °C at least, respectively, based on the high-pressure mineral assemblages.
UR - http://www.scopus.com/inward/record.url?scp=85113753765&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85113753765&partnerID=8YFLogxK
U2 - 10.1111/maps.13735
DO - 10.1111/maps.13735
M3 - Article
AN - SCOPUS:85113753765
VL - 56
SP - 1729
EP - 1743
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
SN - 1086-9379
IS - 9
ER -