Petrogenesis of the EET 92023 achondrite and implications for early impact events

A. Yamaguchi, N. Shirai, C. Okamoto, Mitsuru Ebihara

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We report petrology and geochemistry of an achondrite EET 92023 and compare it with normal and anomalous eucrites. EET 92023 is an unbrecciated achondrite and shows a granular texture mainly composed of low-Ca pyroxene and plagioclase, petrologically similar to normal cumulate eucrites such as Moore County. However, this rock contains a significant amount of kamacite and taenite not common in unbrecciated, crystalline eucrites. EET 92023 contains a significant amount of platinum group elements (PGEs) (ca. 10% of CI), several orders of magnitude higher than those of monomict eucrites. We suggest that the metallic phases carrying PGEs were incorporated by a projectile during or before igneous crystallization and thermal metamorphism. The projectile was likely to be an iron meteorite rather than chondritic materials, as indicated by the lack of olivine and the presence of free silica. Therefore, the oxygen isotopic signature is indigenous, rather than due to contamination of the projectile material with different oxygen isotopic compositions. A significant thermal event involving partial melting and metamorphism after the impact event indicates that EET 92023 records early impact events which took place shortly after the crust formation on a differentiated protoplanet when the crust was still hot.

Original languageEnglish
Pages (from-to)709-721
Number of pages13
JournalMeteoritics and Planetary Science
Volume52
Issue number4
DOIs
Publication statusPublished - 2017 Apr 1
Externally publishedYes

Fingerprint

achondrites
achondrite
eucrite
petrogenesis
projectiles
crusts
platinum group element
platinum
kamacite
iron meteorites
petrology
metamorphism
protoplanets
oxygen
taenite
geochemistry
plagioclase
crust
olivine
iron meteorite

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

Cite this

Petrogenesis of the EET 92023 achondrite and implications for early impact events. / Yamaguchi, A.; Shirai, N.; Okamoto, C.; Ebihara, Mitsuru.

In: Meteoritics and Planetary Science, Vol. 52, No. 4, 01.04.2017, p. 709-721.

Research output: Contribution to journalArticle

@article{ee515825af894ecf9baa854984e48233,
title = "Petrogenesis of the EET 92023 achondrite and implications for early impact events",
abstract = "We report petrology and geochemistry of an achondrite EET 92023 and compare it with normal and anomalous eucrites. EET 92023 is an unbrecciated achondrite and shows a granular texture mainly composed of low-Ca pyroxene and plagioclase, petrologically similar to normal cumulate eucrites such as Moore County. However, this rock contains a significant amount of kamacite and taenite not common in unbrecciated, crystalline eucrites. EET 92023 contains a significant amount of platinum group elements (PGEs) (ca. 10{\%} of CI), several orders of magnitude higher than those of monomict eucrites. We suggest that the metallic phases carrying PGEs were incorporated by a projectile during or before igneous crystallization and thermal metamorphism. The projectile was likely to be an iron meteorite rather than chondritic materials, as indicated by the lack of olivine and the presence of free silica. Therefore, the oxygen isotopic signature is indigenous, rather than due to contamination of the projectile material with different oxygen isotopic compositions. A significant thermal event involving partial melting and metamorphism after the impact event indicates that EET 92023 records early impact events which took place shortly after the crust formation on a differentiated protoplanet when the crust was still hot.",
author = "A. Yamaguchi and N. Shirai and C. Okamoto and Mitsuru Ebihara",
year = "2017",
month = "4",
day = "1",
doi = "10.1111/maps.12821",
language = "English",
volume = "52",
pages = "709--721",
journal = "Meteoritics and Planetary Science",
issn = "1086-9379",
publisher = "The University of Arkansas Press",
number = "4",

}

TY - JOUR

T1 - Petrogenesis of the EET 92023 achondrite and implications for early impact events

AU - Yamaguchi, A.

AU - Shirai, N.

AU - Okamoto, C.

AU - Ebihara, Mitsuru

PY - 2017/4/1

Y1 - 2017/4/1

N2 - We report petrology and geochemistry of an achondrite EET 92023 and compare it with normal and anomalous eucrites. EET 92023 is an unbrecciated achondrite and shows a granular texture mainly composed of low-Ca pyroxene and plagioclase, petrologically similar to normal cumulate eucrites such as Moore County. However, this rock contains a significant amount of kamacite and taenite not common in unbrecciated, crystalline eucrites. EET 92023 contains a significant amount of platinum group elements (PGEs) (ca. 10% of CI), several orders of magnitude higher than those of monomict eucrites. We suggest that the metallic phases carrying PGEs were incorporated by a projectile during or before igneous crystallization and thermal metamorphism. The projectile was likely to be an iron meteorite rather than chondritic materials, as indicated by the lack of olivine and the presence of free silica. Therefore, the oxygen isotopic signature is indigenous, rather than due to contamination of the projectile material with different oxygen isotopic compositions. A significant thermal event involving partial melting and metamorphism after the impact event indicates that EET 92023 records early impact events which took place shortly after the crust formation on a differentiated protoplanet when the crust was still hot.

AB - We report petrology and geochemistry of an achondrite EET 92023 and compare it with normal and anomalous eucrites. EET 92023 is an unbrecciated achondrite and shows a granular texture mainly composed of low-Ca pyroxene and plagioclase, petrologically similar to normal cumulate eucrites such as Moore County. However, this rock contains a significant amount of kamacite and taenite not common in unbrecciated, crystalline eucrites. EET 92023 contains a significant amount of platinum group elements (PGEs) (ca. 10% of CI), several orders of magnitude higher than those of monomict eucrites. We suggest that the metallic phases carrying PGEs were incorporated by a projectile during or before igneous crystallization and thermal metamorphism. The projectile was likely to be an iron meteorite rather than chondritic materials, as indicated by the lack of olivine and the presence of free silica. Therefore, the oxygen isotopic signature is indigenous, rather than due to contamination of the projectile material with different oxygen isotopic compositions. A significant thermal event involving partial melting and metamorphism after the impact event indicates that EET 92023 records early impact events which took place shortly after the crust formation on a differentiated protoplanet when the crust was still hot.

UR - http://www.scopus.com/inward/record.url?scp=85011003025&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85011003025&partnerID=8YFLogxK

U2 - 10.1111/maps.12821

DO - 10.1111/maps.12821

M3 - Article

VL - 52

SP - 709

EP - 721

JO - Meteoritics and Planetary Science

JF - Meteoritics and Planetary Science

SN - 1086-9379

IS - 4

ER -