Discovery of coesite and stishovite in eucrite

Masaaki Miyahara, Eiji Otani, Akira Yamaguchi, Shin Ozawa, Takeshi Sakai, Naohisa Hirao

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Howardite-eucrite-diogenite meteorites (HEDs) probably originated from the asteroid 4 Vesta. We investigated one eucrite, Béréba, to clarify a dynamic event that occurred on 4 Vesta using a shock-induced high-pressure polymorph. We discovered high-pressure polymorphs of silica, coesite, and stishovite originating from quartz and/or cristobalite in and around the shock-melt veins of Béréba. Lamellar stishovite formed in silica grains through a solid-state phase transition. A network-like rupture was formed and melting took place along the rupture in the silica grains. Nanosized granular coesite grains crystallized from the silica melt. Based on shock-induced high-pressure polymorphs, the estimated shock-pressure condition ranged from ∼8 to ∼13 GPa. Considering radiometric ages and shock features, the dynamic event that led to the formation of coesite and stishovite occurred ca. 4.1 Ga ago, which corresponds to the late heavy bombardment period (ca. 3.8-4.1 Ga), deduced from the lunar cataclysm. There are two giant impact basins around the south pole of 4 Vesta. Although the origin of HEDs is thought to be related to dynamic events that formed the basins ca. 1.0 Ga ago, our findings are at variance with that idea.

Original languageEnglish
Pages (from-to)10939-10942
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume111
Issue number30
DOIs
Publication statusPublished - 2014 Jan 1

Keywords

  • Meteoroid impact
  • Shock metamorphism

ASJC Scopus subject areas

  • General

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