Hematite from a mining area in the east border of Quadrilátero
Ferrı́fero, Minas Gerais, Brazil
A.R. Passos Pereira,1, 2 J.D. Fabris,1 F.J. Rios,2 C.A. Rosière,1
P.R. da Costan Couceiro,3 F. Furlan,4 and L.M. Menezes1
1
Departamento de Quı́mica, Universidade Federal de Minas Gerais,
31270-901 Belo Horizonte, Minas Gerais, Brazil
2
Centro de Desenvolvimento da Tecnologia Nuclear,
31270-901 Belo Horizonte, Minas Gerais, Brazil
3
Departamento de Quı́mica, Universidade Federal do Amazonas, Manaus, Brazil
4
Laboratório Nacional de Luz Sı́ncrotron, Campinas, São Paulo, Brazil
Iron oxides may be a very important scientific and technological issue in economicallybased agriculture practices or for industrial mining activities[1], particularly to countries
for which ore commodities represent an important item in its macro-economy. Knowing the mineral transformation pathways in natural systems is the first fundament for
planning exploitation, prospecting new mining areas, predicting ore deposit reserves and
directing geological researches with technological interest[2]. The main purpose of this
ongoing work is to contribute to a better understanding of the main chemical and mineralogical pathways related to the iron oxides formation and transformations involving
hematite in an iron oxide-rich geo-domain. Nine samples collected from a mining area for
iron (geographical coordinates of the sampling site, 20o 07´ 51.71´´ S 43o 25´ 00.09´´
W), in the east border of Quadrilátero Ferrı́fero, state of Minas Gerais, Brazil, were
analyzed with powder X-ray diffractometry from a synchrotron source, 57 Fe Mössbauer
spectroscopy, conventional chemical analytical methods, as redox volumetry, for total iron
contents, and saturation magnetization measurements. The iron content varied from 65
to 69 mass% Fe; from DRX data hematite is actually the major mineral for all samples;
only in few of them characteristic reflections of goethite and magnetite also appeared.
For two samples, the saturation magnetization values were found to be significantly high:
σ = 6.9 and 2.1 J T−1 kg−1 . 298 K-Mössbauer data also confirmed that hematite is the
dominant mineralogical phase. 110 K-Mössbauer spectra and XRD Rietveld refinement
for variable temperatures data allow now a consistent proposition of an overall model for
the main transformation pathways involving hematite, either as product from alteration
of magnetite or as precursor for other iron-bearing species in this geo-system.
Acknowledgments: work supported by FAPEMIG, CNPq (Brazil) and Brazilian National Laboratory of Synchrotron Light.
[1] Fabris, J.D. & Coey, J.M.D. Espectroscopia Mössbauer do 57Fe e Medidas
Magnéticas na Análise de Geomateriais. Tópicos em Ciências do Solo. Viçosa, Sociedade
Brasileira de Ciência do Solo, 2:47-102, 2002 (in Portuguese).
[2] Rosière, C. A. & Chemale Jr, F. Itabiritos e Minérios de Ferro de Alto Teor do
Quadrilátero Ferrı́fero - Uma Visão Geral. Geonomos 8 (2): 27-43, 2000.
e-mail: [email protected]
Keywords: Iron oxides, Synchrotron light, Magnetization