The crystal structures of synthetic Re- and PGE-bearing magnesioferrite spinels: Implications for impacts, accretion and the mantle

Kevin Righter, Robert T Downs

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34 Citations (Scopus)

Abstract

Re- and PGE-bearing magnesioferrite spinels were synthesized at oxidizing conditions between 0.1 MPa and 5.0 GPa, and 1150 to 1600 °C in equilibrium with Re- or PGE-bearing metals and/or oxides. Electron microprobe analysis and single crystal X-ray diffraction techniques were employed to determine the composition, crystal structures and site occupancies, indicating that the magnesioferrite structure can accommodate wt% levels of Re and the platinum group elements (PGE) at oxidized conditions. These results suggest that magnesioferrite spinels found in K-T boundary samples worldwide could be an important host phase for the Ir, Ru, Os, Re, and Rh anomalies found in the boundary layer. Higher Ru/Ir values in Pacific magnesioferrite-bearing samples may be a reflection of higher condensation temperatures of the oxides. The distribution of PGE's in mantle and magmatic rocks may depend on the stability of spinel-structure oxides, especially those with a high magnesioferrite component. Finally, magnetite-rich meteorite fusion crusts may hold PGEs in oxidized form.

Original languageEnglish (US)
Pages (from-to)619-622
Number of pages4
JournalGeophysical Research Letters
Volume28
Issue number4
DOIs
StatePublished - Feb 15 2001

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platinum group element
crystal structure
Earth mantle
platinum
accretion
mantle
oxides
Cretaceous-Tertiary boundary
oxide
meteorites
magnetite
spinel
boundary layers
crusts
condensation
fusion
rocks
anomalies
electron probe analysis
meteorite

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

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abstract = "Re- and PGE-bearing magnesioferrite spinels were synthesized at oxidizing conditions between 0.1 MPa and 5.0 GPa, and 1150 to 1600 °C in equilibrium with Re- or PGE-bearing metals and/or oxides. Electron microprobe analysis and single crystal X-ray diffraction techniques were employed to determine the composition, crystal structures and site occupancies, indicating that the magnesioferrite structure can accommodate wt{\%} levels of Re and the platinum group elements (PGE) at oxidized conditions. These results suggest that magnesioferrite spinels found in K-T boundary samples worldwide could be an important host phase for the Ir, Ru, Os, Re, and Rh anomalies found in the boundary layer. Higher Ru/Ir values in Pacific magnesioferrite-bearing samples may be a reflection of higher condensation temperatures of the oxides. The distribution of PGE's in mantle and magmatic rocks may depend on the stability of spinel-structure oxides, especially those with a high magnesioferrite component. Finally, magnetite-rich meteorite fusion crusts may hold PGEs in oxidized form.",
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AB - Re- and PGE-bearing magnesioferrite spinels were synthesized at oxidizing conditions between 0.1 MPa and 5.0 GPa, and 1150 to 1600 °C in equilibrium with Re- or PGE-bearing metals and/or oxides. Electron microprobe analysis and single crystal X-ray diffraction techniques were employed to determine the composition, crystal structures and site occupancies, indicating that the magnesioferrite structure can accommodate wt% levels of Re and the platinum group elements (PGE) at oxidized conditions. These results suggest that magnesioferrite spinels found in K-T boundary samples worldwide could be an important host phase for the Ir, Ru, Os, Re, and Rh anomalies found in the boundary layer. Higher Ru/Ir values in Pacific magnesioferrite-bearing samples may be a reflection of higher condensation temperatures of the oxides. The distribution of PGE's in mantle and magmatic rocks may depend on the stability of spinel-structure oxides, especially those with a high magnesioferrite component. Finally, magnetite-rich meteorite fusion crusts may hold PGEs in oxidized form.

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