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Rythmic changes in crystal chemistry of trioctahedral Cr-chlorites and Cr entrapment: a SEM, EM and Raman study

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Prieto Colorado, A.C. and Boiron, Marie Christine and Cathelineau, Michel and Mosser-Ruck, R. and López García, José Ángel and García, C. (2003) Rythmic changes in crystal chemistry of trioctahedral Cr-chlorites and Cr entrapment: a SEM, EM and Raman study. Clay minerals, 38 . pp. 339-352. ISSN 0009-8558

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Official URL: http://www.minersoc.org/pages/e_journals/clay.html



Abstract

Back-scattered scanning electron microscopy (SEM) images of Cr-chlorite crystals
from Erzerum (Turkey) reveal that the crystals are chemically inhomogeneous and display complex
but well defined crystal zoning characterized by growth bands with contrasting chemical features.
The chemical zoning has been investigated at the micron scale using an integrated approach,
combining BSEM images, in situ chemical analysis by electron microprobe and Raman
spectroscopy. Enrichment in Cr, due to octahedral Al substitution, reaches up to 0.7 atoms per
half formula, especially in bands where the Mg content is depleted. These substitutions are also
depicted at the micron scale on Raman spectra by changes in the n(OH) band intensities and
positions that correlate with the Cr content. The Cr-enrichment occurs thus during specific stages of
crystal growth, probably in response to changes in the fluid chemistry controlling the relative
availability of Cr, Mg and Al in solution.


Item Type:Article
Uncontrolled Keywords:Chlorite, Cr, Electron microprobe, Raman spectroscopy, SEM
Subjects:Sciences > Geology > Crystallography
ID Code:20186
Deposited On:28 Feb 2013 13:22
Last Modified:11 Dec 2018 08:46

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