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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
Source Normalized Impact per Paper (SNIP) 2017: 1.059

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1945-3027
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Volume 92, Issue 10

Issues

Ferric iron in Al-bearing akimotoite coexisting with iron-nickel metal in a shock-melt vein in an L-6 chondrite

Nobuyoshi Miyajima / Ahmed El Goresy / Catherine Dupas-Bruzek
  • Centre d'Etudes et de Recherches Lasers et Applications, Universite des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq Cedex, France
  • Other articles by this author:
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/ Friedrich Seifert / David C. Rubie / Ming Chen / Xiande Xie
Published Online: 2015-04-01 | DOI: https://doi.org/10.2138/am.2007.2546

Abstract

We report evidence for high ferric iron to total iron (Fe3+/ΣFe) ratios in Al-bearing akimotoite coexisting with other high-pressure silicates and Fe-Ni metal from shock melt-veins in the Sixiangkou (L-6) chondrite. The measurements were made using electron energy-loss near-edge structure (ELNES) spectroscopy. The results demonstrate that akimotoite in shock-melt veins of this meteorite has high proportions of Fe3+, with a Fe3+/ΣFe ratio of 0.67(3). In contrast, the coexisting majoritic garnet and ringwoodite, which are the typical Fe-bearing phases in shock veins in this meteorite, are enriched in Fe2+ rather than Fe3+, with Fe3+/ΣFe ratios of 0.10(5) and 0.15(5), respectively. We conclude that the higher affinity of Fe3+ for akimotoite, rather than for the other dense silicate phases, is related strongly to the substitution mechanism of trivalent cations. This mechanism is described as VI(A)Fe3+ + VI(B)Al3+ = VI(A)Mg2+ + VI(B)Si4+ in the ABO3 structural formula of MgSiO3-ilmenite under high pressures and temperatures, and operates even at a low oxygen fugacity where Fe-Ni metal is stable.

Keywords: Meteorite; L-6 chondrite; electron microscopy; Fe-bearing silicates; akimotoite; high pressure; shock-melt vein

About the article

Received: 2006-12-28

Accepted: 2007-05-02

Published Online: 2015-04-01

Published in Print: 2007-10-01


Citation Information: American Mineralogist, Volume 92, Issue 10, Pages 1545–1549, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2007.2546.

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