A Mössbauer and X-ray diffraction study of annites synthesized at different oxygen fugacities and crystal chemical implications |
| |
Authors: | G. J. Redhammer A. Beran E. Dachs G. Amthauer |
| |
Affiliation: | 1. Institute of Mineralogy, University of Salzburg, Hellbrunnerstra?e 34, A-5020, Salzburg 2. Institute of Mineralogy and Crystallography, University of Vienna, Dr. Karl Lueger-Ring 1, A-1010, Vienna
|
| |
Abstract: | A refined set of Mössbauer parameters (isomer shifts, quadrupole splittings, Fe2+/Fe3+ ratios) and lattice parameters were obtained from annites synthesized hydrothermally at pressures between 3 and 5 kbars, temperatures ranging from 250 to 780° C and oxygen fugacities controlled by solid state buffers (NNO, QMF, IM, IQF). Mössbauer spectra showed Fe2+ and Fe3+ on both the M1 and the M2 site. A linear relationship between Fe3+ content and oxygen fugacity was observed. Towards low Fe3+ values this linear relationship ends at ≈10% of total iron showing that the Fe3+ content cannot be reduced further even if more reducing conditions are used. This indicates that in annite at least 10% Fe2+ are substituted by Fe3+ in order to match the larger octahedral layer to the smaller tetrahedral layer. IR spectra indicate that formation of octahedral vacancies plays an important role for charge balance through the substitution 3 Fe2+ → 2 Fe3+ + ?(oct). |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|