Repository logo

Infoscience

  • English
  • French
Log In
Logo EPFL, École polytechnique fédérale de Lausanne

Infoscience

  • English
  • French
Log In
  1. Home
  2. Academic and Research Output
  3. Journal articles
  4. Ferrous silicate spherules with euhedral iron-nickel metal grains from CH carbonaceous chondrites: Evidence for supercooling and condensation under oxidizing conditions
 
research article

Ferrous silicate spherules with euhedral iron-nickel metal grains from CH carbonaceous chondrites: Evidence for supercooling and condensation under oxidizing conditions

Meibom, A.  
•
Petaev, M.I.
•
Keil, K.
Show more
2000
Meteoritics & Planetary Science

The CH carbonaceous chondrites contain a population of ferrous (Fe/(Fe + Mg) approximate to 0.1-0.4) silicate spherules (chondrules), about 15-30 mum in apparent diameter, composed of cryptocrystalline olivine-pyroxene normative material, +/-SiO2-rich glass, and rounded-to-euhedral Fe,Ni metal grains. The silicate portions of the spherules are highly depleted in refractory lithophile elements (CaO, Al2O3, and TiO2 <0.04 wt%) and enriched in FeO, MnO, Cr2O3, and Na2O relative to the dominant, volatile-poor, magnesian chondrules from CH chondrites. The Fe/(Fe + Mg) ratio in the silicate portions of the spherules is positively correlated with Fe concentration in metal grains, which suggests that this correlation is not due to oxidation, reduction, or both of iron (FeOsil Fe-met) during melting of metal-silicate solid precursors. Rather, we suggest that this is a condensation signature of the precursors formed under oxidizing conditions. Each metal grain is compositionally uniform, but there are significant intergrain compositional variations: about 8-18 wt% Ni, <0.09 wt% Cr, and a sub-solar Co/Ni ratio. The precursor materials of these spherules were thus characterized by extreme elemental fractionations, which have not been observed in chondritic materials before. Particularly striking is the fractionation of Ni and Co in the rounded-to-euhedral metal grains, which has resulted in a Co/Ni ratio significantly below solar. The liquidus temperatures of the euhedral Fe,Ni metal grains are lower than those of the coexisting ferrous silicates, and we infer that the former crystallized in supercooled silicate melts. The metal grains are compositionally metastable; they are not decomposed into taenite and kamacite, which suggests fast postcrystallization cooling at temperatures below 970 K and lack of subsequent prolonged thermal metamorphism at temperatures above 400-500 K.

  • Details
  • Metrics
Type
research article
DOI
10.1111/j.1945-5100.2000.tb01513.x
Web of Science ID

WOS:000166005400012

Author(s)
Meibom, A.  
Petaev, M.I.
Keil, K.
Zolensky, M.E.
Saito, A.
Mukai, M.
Ohsumi, K.
Krot, A.N.
Date Issued

2000

Published in
Meteoritics & Planetary Science
Volume

35

Start page

1249

End page

1258

Subjects

Porphyritic Pyroxene Chondrules

•

Feo-Rich

•

Model

•

Petrology

•

Alh85085

•

Crystallization

•

Systems

•

Poor

•

Cr

Editorial or Peer reviewed

REVIEWED

Written at

OTHER

EPFL units
LGB  
Available on Infoscience
May 15, 2012
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/80351
Logo EPFL, École polytechnique fédérale de Lausanne
  • Contact
  • infoscience@epfl.ch

  • Follow us on Facebook
  • Follow us on Instagram
  • Follow us on LinkedIn
  • Follow us on X
  • Follow us on Youtube
AccessibilityLegal noticePrivacy policyCookie settingsEnd User AgreementGet helpFeedback

Infoscience is a service managed and provided by the Library and IT Services of EPFL. © EPFL, tous droits réservés