ISSN:
1432-2021
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Abstract Room temperature and low temperature Mössbauer and optical absorption spectroscopic data on six natural chloritoids characterized by means of electron microprobe and X-ray powder diffraction techniques are presented. Two narrow quadrupole doublets with widths of 0.25–0.29 mm/s assigned to Fe2+ in a relatively large octahedral site and Fe3+ in a smaller octahedral site, are observed in the Mössbauer spectra. Polarized optical absorption spectra reveal three main absorption bands. A broad absorption band at 16,300 cm−1, which is strongly polarized in E‖X and E‖Y and shows a linear increase in integral absorption with increasing [Fe2+] [Fe3+] concentration product, is assigned to a Fe2++Fe3+→Fe3++Fe2+ charge transfer transition. This band displays also a temperature dependence different from that of single ion d−d transitions. Two absorption bands at 10,900 cm−1 and 8,000 cm−1 are, on the basis of compositional dependence and energy, assigned to Fe2+ in the large M(1B) octahedra of the brucite-type layer in chloritoid. Combined spectroscopic evidence and structural and chemical considerations support a distribution scheme for ferrous and ferric iron which orders the Fe2+ ions in the M(1B) octahedra and the Fe3+ ions in the small M(1A) octahedral sites. Both types of octahedra are found in the brucite type layer of chloritoid.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00308227
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