Tubular symplectic inclusions in olivine from the fukang pallasite

Michael R. Stevens, David R. Bell, P R Buseck

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Olivine from the Fukang meteorite, like that from many other pallasites, contains distinctive arrays of parallel, straight, tubular inclusions. They differ in their extension and linearity from those in terrestrial olivines. They comprise approximately 1% of the total volume. Most have lens-shaped cross-sections, but some are rounded. The major axis of the lens-shaped inclusions is rigorously oriented along olivine [001], and the rounded ones lie along olivine [010] and a few along [100]. The linear nature and orientations of the inclusions suggest that they nucleated on screw dislocations, perhaps formed through shock triggering. High-resolution transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy show that the inclusions consist of symplectic intergrowths of chromite, diopside, and silica that appear to have formed by exsolution from the host olivine. The symplectites consist of chromite lamellae with approximately 35-nm spacings that grew outward from a central plane, with interstitial diopside and silica. Contrast modulations having an average spacing of 4.4 nm occur within the chromite lamellae. Using a reaction-front model, we estimate that exsolution occurred over a period of 30 to 100 min, suggesting rapid cooling at high temperature. The crystallographic observations and inferences on growth rate are consistent with the hypothesis that the inclusions nucleated during heating following dislocation formation in a shock event, perhaps concurrent with that proposed to have disrupted the pallasite parent body.

Original languageEnglish (US)
Pages (from-to)899-910
Number of pages12
JournalMeteoritics and Planetary Science
Volume45
Issue number5
DOIs
StatePublished - May 2010

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olivine
chromites
inclusions
chromite
exsolution
diopside
lamella
dislocation
spacing
silica
shock
lenses
silicon dioxide
screw dislocations
parent body
meteorites
linearity
inference
meteorite
x ray spectroscopy

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

Cite this

Tubular symplectic inclusions in olivine from the fukang pallasite. / Stevens, Michael R.; Bell, David R.; Buseck, P R.

In: Meteoritics and Planetary Science, Vol. 45, No. 5, 05.2010, p. 899-910.

Research output: Contribution to journalArticle

Stevens, Michael R. ; Bell, David R. ; Buseck, P R. / Tubular symplectic inclusions in olivine from the fukang pallasite. In: Meteoritics and Planetary Science. 2010 ; Vol. 45, No. 5. pp. 899-910.
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