Evidence for multiple dynamic events and subsequent decompression stage recorded in a shock vein

Masaaki Miyahara, Eiji Ohtani, Makoto Kimura, Shin Ozawa, Toshiro Nagase, Masahiko Nishijima, Kenji Hiraga

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

We investigated a shock vein of the Yamato 791384 L6 chondrite to clarify the nature and sequence of the dynamic processes that resulted from the shock events. The chondritic host-rock of Y-791384 mainly consists of olivine (Fa24-25), low-Ca pyroxene (Fs18-22), albitic feldspar (An9-10Ab84-86Or5-7), troilite and metallic Fe-Ni. The shock vein contains majorite (or majorite-pyropess) and magnesiowüstite (+ minor jadeite) as high-pressure polymorphs. Two different dynamic events were recorded in the shock vein. The majorite grain contained vitrified (Mg,Fe)SiO3-perovskite inclusions. The (Mg,Fe)SiO3-perovskite was crystallized from a chondritic melt, and is a remnant of a first dynamic event. The majorite and magnesiowüstite were also crystallized directly from a chondritic melt but induced by a second dynamic event. The pressure condition for the first and second dynamic events would be >~24GPa and <~22GPa, respectively. Pervasive feather-shaped olivine (Fa16) nucleated on the magnesiowüstite and majorite. This feather-shaped olivine is evidence for rapidly grown olivine from the melt related to the shock event. Phase relations deduced from high-pressure melting experiments of the Allende meteorite and peridotite indicate that the magnesiowüstite and majorite+olivine pair cannot coexist at equilibrium condition. The disequilibrium assemblage reflects a decompression stage. These features demonstrate the complexity of events during a natural dynamic process.

Original languageEnglish
Pages (from-to)361-368
Number of pages8
JournalEarth and Planetary Science Letters
Volume307
Issue number3-4
DOIs
Publication statusPublished - 2011 Jul 15

Keywords

  • Decompression
  • Melting
  • Olivine dendrite
  • Shocked meteorite
  • TEM

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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