Carbon polymorphism in shocked meteorites: Evidence for new natural ultrahard phases

Tristan Ferroir, Leonid Dubrovinsky, Ahmed El Goresy, Alexandre Simionovici, Tomoki Nakamura, Philippe Gillet

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

A slice of the Haverö meteorite which belongs to the ureilite class known to contain graphite and diamond was cut and then polished as a thin section using a diamond paste. We identified two carbonaceous areas which were standing out by more than 10 μm in relief over the surface of the silicate matrix suggesting that the carbonaceous phases were not easily polishable by a diamond paste and would therefore imply larger polishing hardness. These areas were investigated by reflected light microscopy, high-resolution Field Emission SEM (FESEM), energy-dispersive X-ray (EDX) analysis, Raman spectroscopy, and were subsequently extracted for in situ synchrotron microbeam X-ray fluorescence (XRF), imaging and X-ray diffraction (XRD). We report here the natural occurrences of one new ultrahard rhombohedral carbon polymorph of the R3m space group which structure is very close to diamond but with a partial occupancy of some of the carbon sites. We also report the natural occurrence of the theoretically predicted 21R diamond polytype with lattice parameters very close to what has been modelized. These findings are of great interests for better understanding the world of carbon polymorphs and diamond polytypes giving new natural materials to investigate. These natural samples demonstrate that the carbon system is even more complex than what is currently thought based on ab initio static lattice calculations and high-pressure experiments since this new ultrahard polymorph has never been predicted nor synthesized.

Original languageEnglish
Pages (from-to)150-154
Number of pages5
JournalEarth and Planetary Science Letters
Volume290
Issue number1-2
DOIs
Publication statusPublished - 2010 Feb 15
Externally publishedYes

Keywords

  • Haverö
  • diamond
  • diamond polytype
  • shock
  • ultrahard carbon
  • ureilite

ASJC Scopus subject areas

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

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