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Nature and mechanism of ilmenite alteration: a Mössbauer and X-ray diffraction study of oxidized ilmenite from the Beja-Acebuches Ophiolite Complex (SE Portugal)

Published online by Cambridge University Press:  05 July 2018

J. C. Waerenborgh ,
J. Figueiras ,
A. Mateus  and
M. Gonçalves
J. C. Waerenborgh*
Affiliation:
Departamento de Química, Instituto Tecnológico e Nuclear, P-2686-953 Sacavém, Portugal
J. Figueiras
Affiliation:
Departamento de Geologia and CREMINER, Faculdade de Ciências da Universidade de Lisboa, P-1749-016 Lisbon, Portugal
A. Mateus
Affiliation:
Departamento de Geologia and CREMINER, Faculdade de Ciências da Universidade de Lisboa, P-1749-016 Lisbon, Portugal
M. Gonçalves
Affiliation:
Departamento de Geologia and CREMINER, Faculdade de Ciências da Universidade de Lisboa, P-1749-016 Lisbon, Portugal
*
*E-mail: jcarlos@itn1.itn.pt
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Abstract

Ilmenites from the least-altered rocks of the Beja-Acebuches Ophiolite Complex (SE Portugal), with low Ti values and excess Fe, despite rare optical evidence of hematite exsolution, were studied by 57Fe Mössbauer spectroscopy and X-ray diffraction. According to single-crystal XRD the sequence of alternate layers characteristic of the ideal ilmenite structure is preserved, the excess Fe being accommodated in the Ti layers. No superparamagnetic oxides were detected by 57Fe Mössbauer spectroscopy. The typical spectra of bulk αFe2O3 and of Fe3+-containing ilmenite, in the paramagnetic state above 49 K and magnetically ordered at 6 K, are observed. The average degree of oxidation of the ilmenites, estimated from the chemical analysis assuming ideally stoichiometric full cation site occupancies, is also confirmed by 57Fe Mössbauer data. Since our crystal chemistry study gave no evidence of crypto-exsolution textures within the ilmenite with the observed compositions, fast cooling from magmatic temperatures and decomposition of ilmenite in supergene conditions is suggested.

Keywords

ilmeniteFe-Ti oxidescrystal chemistry57Fe Mössbauer spectroscopysingle-crystal X-ray diffraction
Type
Research Article
Information
Mineralogical Magazine , Volume 66 , Issue 3 , June 2002 , pp. 421 - 430
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

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References

Bayliss, P., Erd, R.C., Mrose, M., Roberts, A.C. and Sabina, A.P. (1993) Mineral Powder Diffraction File Databook. International Centre for Diffraction Data, Park Lane, Pennsylvania, USA, 774 pp.Google Scholar
Belkasmi, M., Cuney, M., Pollard, P.J. and Bastoul, A. (2000) Chemistry of the Ta-Nb-Sn-W oxide minerals from the Yichun rare metal granite (SE China): genetic implications and comparison with Moroccan and French Hercynian examples. Mineralogical Magazine, 64, 507–523.CrossRefGoogle Scholar
Bowen, L.H., De Grave, E. and Vandenberghe, R.E. (1993) Mössbauer effect studies of magnetic soils and sediments. Pp. 115–159 in: Mössbauer Spectroscopy Applied to Magnetism and Materials Science, Vol. 1 (Long, G.J. and Grandjean, F., editors). Plenum Press, New York.CrossRefGoogle Scholar
Fair, C.K. (1990) MOLEN. Enraf-Nonius, Delft, The Netherlands.Google Scholar
Figueiras, J., Mateus, A., Gonçalves, M., Waerenborgh, J.C. and Fonseca, P. (2002) Geodynamical evolution of the South Variscan Iberian Suture as recorded by mineral transformations. Geodynamica Acta, 15, 45–61.CrossRefGoogle Scholar
Grant, R.W., Housley, R.M. and Geller, S. (1972) Hyperfine interaction of Fe2+ in ilmenite. Physical Review B, 5,1700–1704.CrossRefGoogle Scholar
Harrison, R.J., Redfern, S.A.T. and Smith, R.I. (2000) In-situ study of the R to R c phase transition in the ilmenite-hematite solid solution using time-of-flight neutron power diffraction. American Mineralogist, 85, 194–205.CrossRefGoogle Scholar
Hovestreydt, E. (1983) On the atomic scattering factor for O2- . Acta Crystallographica A, 39, 268–269.CrossRefGoogle Scholar
Ibers, J.A. and Hamilton, W.C. (1974) International Tables for X-ray Crystallography. Vol. 4. Revised and sup plementary tables. Kynoch Press, Birmingham, England, 854 pp.Google Scholar
Lindsley, D.H. (1976) The crystal chemistry and structure of oxide minerals as exemplified by the Fe-Ti oxides. Pp. L1–L60 in: Oxide Minerals (Rumble, D. III, editor). Reviews in Mineralogy, 3, BookCrafters Inc., Chelsea, Michigan, USA.Google Scholar
Mitra, S. (1992) Applied Mössbauer Spectroscopy. Theory and Practice for Geochemists and Archaelogists. Pergamon Press, Oxford, UK, 381 pp.Google Scholar
Mordberg, L.E., Stanley, C.J., and Germann, K. (2001) Mineralogy and geochemistry of trace elements in bauxites: The Devonian Schugorsk deposit, Russia. Mineralogical Magazine, 65, 81–101.CrossRefGoogle Scholar
Murad, E. and Johnston, J.H. (1987) Iron oxides and hydroxides. Pp. 507–582 in: Mössbauer Spectroscopy Applied to Inorganic Chemistry Vol. 2 (Long, G.J., editor). Plenum Press, New York.Google Scholar
North, A.C.T., Phillips, D.C. and Mathews, F.S. (1968) A semi-empirical method of absorption correction. Acta Crystallographica A, 24, 351–359.CrossRefGoogle Scholar
Shannon, R.D. (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica A, 32, 751–767.CrossRefGoogle Scholar
Sheldrick, G.M. (1993) SHELXL-93: Program for Crystal Structure Refinement. Univers ity of Göttingen, Germany, 109 pp.Google Scholar
Virgo, D., Luth, R.W., Moats, M.A. and Ulmer, G.C. (1988) Constraints on the oxidation of the mantle: an electrochemical and 57Fe Mössbauer study of mantle derived ilmenites. Geochimica et Cosmochimica Acta, 52, 1781–1794.CrossRefGoogle Scholar
Waerenborgh, J.C., Figueiredo, M.O., Cabral, J.M.P. and Pereira, L.C.J. (1994) Powder XRD structure Refinement and 57Fe Mössbauer effect study of synthetic Zn1-xFexAl2O4 (0 < x ⩽ 1) spinels annealed at different temperatures. Physics and Chemistry of Minerals, 21, 460–468.CrossRefGoogle Scholar
Young, R.A., Sakthivel, A., Moss, T.S. and Paiva-Santos, C.O. (1995) DBWS-9411 – an upgrade of the DBWS programs for Rietveld Refinement with PC and mainframe computers. Journal of Applied Crystallography, 28, 366–367.CrossRefGoogle Scholar