Back-transformation of high-pressure phases in a shock melt vein of an H-chondrite during atmospheric passage: Implications for the survival of high-pressure phases after decompression

M. Kimura, M. Chen, Y. Yoshida, A. El Goresy, E. Ohtani

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

We investigated the H6-chondrite Yamato 75267, in which a fusion crust cuts a shock melt vein. The shock vein region, more than 280 μm from the fusion crust, contains high-pressure phases, such as ringwoodite, majorite-pyropess garnet and NaAlSi3O8 hollandite. However, the shock vein close to the fusion crust entirely consists of the low-pressure polymorphs, olivine, low-Ca pyroxene and plagioclase glass. The boundary between low- and high-pressure phase regions is parallel to the fusion crust. During the atmospheric passage, the peripheral part of the chondrite was melted to form the fusion crust. Our microscopic, laser micro-Raman, electron microprobe investigations and calculations indicate an area up to 300 μm from the fusion crust experienced a temperature of 1400°C after 3 s during the melting of the peripheral part. The high-pressure phases would, at this conditions, quickly transform back to their low-pressure polymorphs. The result obtained here indicates that post-shock temperatures in the interior part of the veins were much lower than 1400°C, thus leading to the survival of high-pressure phases in heavily shocked chondrites.

Original languageEnglish
Pages (from-to)141-150
Number of pages10
JournalEarth and Planetary Science Letters
Volume217
Issue number1-2
DOIs
Publication statusPublished - 2004 Jan 1

Keywords

  • Back-transformation
  • Fusion crust
  • H-chondrite
  • Ringwoodite
  • Shock event

ASJC Scopus subject areas

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

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