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Non-integral hybrid ions in tourmaline: buffering and geo-thermometry

Ferrow, Embaie LU (2009) In European Journal of Mineralogy 21(1). p.241-250
Abstract
The tourmaline group of minerals is indeed an enigma. Experimental data from optical spectroscopy, electron microscopy, and Mossbauer spectroscopy reveal a host of physical properties that lack a common structural clarification. For example, tourmaline samples change colour when irradiated with X-ray and gamma-ray radiations some reverting back when heated in air; exhibit simultaneous oxidation and reduction on annealing in an atmosphere of H-2; display different plane group symmetries under TEM; possess the most complicated Mossbauer spectra of all Fe-bearing silicates. In this study, four Brazilian samples were chosen for detailed study by Mossbauer spectroscopy to find out a common structural factor to the physical anomalies reported in... (More)
The tourmaline group of minerals is indeed an enigma. Experimental data from optical spectroscopy, electron microscopy, and Mossbauer spectroscopy reveal a host of physical properties that lack a common structural clarification. For example, tourmaline samples change colour when irradiated with X-ray and gamma-ray radiations some reverting back when heated in air; exhibit simultaneous oxidation and reduction on annealing in an atmosphere of H-2; display different plane group symmetries under TEM; possess the most complicated Mossbauer spectra of all Fe-bearing silicates. In this study, four Brazilian samples were chosen for detailed study by Mossbauer spectroscopy to find out a common structural factor to the physical anomalies reported in the literature. It was found out that the tourmaline group of minerals contain multi-valence elements that are involved in electron exchange between the edge-sharing asymmetric Y and Z crystallographic sites. It is conceivable that the host of physical properties recorded in the literature could be due to the inherent structural misfit between the Y and Z sites and the mechanisms adopted to reduce the strain associated along the shared edges. The complexity of non-integral oxidation states possible - due to electron sharing among the different multi-valence elements present in the structure - further enhances the diverse physical properties observed. Moreover, on heating in air, no net oxidation or reduction takes place in the tourmaline group of minerals over a temperature range as long as there are electron donors and acceptors left in the structure, serving simultaneously as potential single-phase buffers and geo-thermometers. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
hybrid ions, tourmaline, Mossbauer, buffer, geo-thermometer
in
European Journal of Mineralogy
volume
21
issue
1
pages
241 - 250
publisher
E Schweizerbartsche Verlags
external identifiers
  • wos:000263454400023
  • scopus:78650202301
ISSN
1617-4011
DOI
10.1127/0935-1221/2009/0021-1863
language
English
LU publication?
yes
id
378d0048-cb11-4c55-94dd-899836764666 (old id 1372509)
date added to LUP
2009-05-08 15:43:30
date last changed
2017-01-01 05:03:40
@article{378d0048-cb11-4c55-94dd-899836764666,
  abstract     = {The tourmaline group of minerals is indeed an enigma. Experimental data from optical spectroscopy, electron microscopy, and Mossbauer spectroscopy reveal a host of physical properties that lack a common structural clarification. For example, tourmaline samples change colour when irradiated with X-ray and gamma-ray radiations some reverting back when heated in air; exhibit simultaneous oxidation and reduction on annealing in an atmosphere of H-2; display different plane group symmetries under TEM; possess the most complicated Mossbauer spectra of all Fe-bearing silicates. In this study, four Brazilian samples were chosen for detailed study by Mossbauer spectroscopy to find out a common structural factor to the physical anomalies reported in the literature. It was found out that the tourmaline group of minerals contain multi-valence elements that are involved in electron exchange between the edge-sharing asymmetric Y and Z crystallographic sites. It is conceivable that the host of physical properties recorded in the literature could be due to the inherent structural misfit between the Y and Z sites and the mechanisms adopted to reduce the strain associated along the shared edges. The complexity of non-integral oxidation states possible - due to electron sharing among the different multi-valence elements present in the structure - further enhances the diverse physical properties observed. Moreover, on heating in air, no net oxidation or reduction takes place in the tourmaline group of minerals over a temperature range as long as there are electron donors and acceptors left in the structure, serving simultaneously as potential single-phase buffers and geo-thermometers.},
  author       = {Ferrow, Embaie},
  issn         = {1617-4011},
  keyword      = {hybrid ions,tourmaline,Mossbauer,buffer,geo-thermometer},
  language     = {eng},
  number       = {1},
  pages        = {241--250},
  publisher    = {E Schweizerbartsche Verlags},
  series       = {European Journal of Mineralogy},
  title        = {Non-integral hybrid ions in tourmaline: buffering and geo-thermometry},
  url          = {http://dx.doi.org/10.1127/0935-1221/2009/0021-1863},
  volume       = {21},
  year         = {2009},
}