Abstract
Mössbauer spectra for a variety of analysed spinel phases, representing a very wide range in both total iron content and Fe3+/(Fe2++Fe3+) ratio, indicate an essentially ordered arrangement of iron atoms in the crystal structures of natural chromite and Cr-bearing spinels. All of the Mössbauer spectra have been rationalised by fitting just two doublets, assigned to Fe2+ in the tetrahedral (T) cation site and Fe3+ in the octahedral (M) site, using initial Mössbauer parameters for synthetic end-member compositions. Calculated Fe3+ to Fe2+ ratios agree well with wet chemical data. This ideal Fe2+ (T site) -Fe3+ (M site) ordering scheme has been disregarded in recent Mössbauer studies on chromite, and complex fits and explanations have been proposed. However, we find no evidence in the Mössbauer spectra of the spinels investigated in this study of T site Fe3+ and M site Fe2+ or of electron delocalization (or chargehopping) effects.
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References
Aldridge LP, Bancroft GM, Fleet ME, Herzberg CT (1978) Omphacite studies II. Mössbauer spectra of C2/c and P2/n omphacites. Am Mineral 63:1107–1115
Bacon GE (1952) A neutron-diffraction study of magnesium aluminum oxide. Acta Crystallogr 5:685–686
Bancroft GM (1973) Mössbauer spectroscopy: An introduction for inorganic chemists and geochemists. McGraw-Hill, England, Wiley, New York
Carmichael ISE (1967) The iron-titanium oxides of salic volcanic rocks and their associated ferromagnesian silicates. Contrib Mineral Petrol 14:36–64
Da Silva EG, Abras A, Sette Camara AOR (1976) Mössbauer effect study of cation distribution in natural chromites. J Phys 12:783–785
Da Silva EG, Abras A, Speziali L (1980) Mössbauer effect study of natural chromites of Brazilian and Philippine origin. Appl Phys 22:389–392
Dowty E, Lindsley DH (1973) Mössbauer spectra of synthetic heden-bergite-ferrosilite pyroxenes. Am Mineral 58:850–868
Fatseas GA, Dormann JL, Blanchard H (1976) Study of the Fe3+/Fe2+ ratio in natural chromites (Fex,Mg1−x) (Cr1−y−z, Fey,Alz)O4. J Phys 12:787–792
Fleet ME (1981) The crystal structure of magnetite. Acta Crystallogr B37:917–920
Greenwood NN (1968) Ionic crystals, lattice defects and nonstoichiometry. Butterworths, London
Herzberg CT (1978) Pyroxene geothermometry and geobarometry: Experimental and thermodynamic evaluation of some subsolidus phase relations involving pyroxenes in the system CaO-MgO-Al2O3-SiO2. Geochim Cosmochim Acta 42:945–957
Huggins FE (1975) Mössbauer effect studies of iron minerals under pressures of up to 200 kbars. Ph.D. thesis, Massachusetts Institute of Technology
Irvine TN (1965) Chromian spinel as a petrogenetic indicator, Part 1, Theory. Can J Earth Sci 2:648–672
Jackson ED (1969) Chemical variation in coexisting chromite and olivine in chromitite zones of the Stillwater complex. Econ Geol Mon 4:41–71
McCammon CA (1978) A study of the oxidation and thermal decomposition of vivianite using Mössbauer and optical absorption spectroscopy. B.Sc. (hons.) thesis, Massachusetts Institute of Technology
Mizoguchi T, Tanaka M (1963) The nuclear quadrupole interaction of 57Fe in spinel type oxides. J Phys Soc Japan 18:1301–1306
Navrotsky A, Kleppa OJ (1967) The thermodynamics of cation distributions in simple spinels. J Inorg Nucl Chem 29:2701–2714
Navrotsky A, Kleppa OJ (1968) Thermodynamics of formation of simple spinels. J Inorg Nucl Chem 30:479–498
Newton RC (1977) Thermochemistry of garnets and aluminous pyroxenes in the CMAS system. In: Frazer DG (ed) Thermodynamics in geology. D. Reidel Publishing, Dordrecht-Holland
Osborne MD, Bancroft GM, Fleet ME (1981) (in preparation)
Robbins M, Wertheim GK, Sherwood RC, Buchanan DNE (1971) Magnetic properties and site distributions in the system FeCr2O4-Fe3O4 (Fe2+Cr2−xFe 3+x O4). J Phys Chem Solids 32:717–729
Ruby SL (1973) Why MISFIT when you already have χ2. In: Gruverman J (ed) Mössbauer effect methodology, vol 9. Plenum Press, New York
Sawatzky GA (1969) Recoiless-fraction ratios for 57Fe in octahedral and tetrahedral sites of a spinel and a garnet. Phys Rev 183:383–386
Stone AJ, Augard HJ, Fenger J (1971) MOSSPEC: Program for resolving Mössbauer spectra. Publ Danish Atomic Energy Comm R150-M-1348
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Osborne, M.D., Fleet, M.E. & Michael Bancroft, G. Fe2+ -Fe3+ ordering in chromite and Cr-bearing spinels. Contr. Mineral. and Petrol. 77, 251–255 (1981). https://doi.org/10.1007/BF00373539
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DOI: https://doi.org/10.1007/BF00373539