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Iron oxides of Fazendão Deposit, East Border of Quadrilátero Ferrífero, Minas Gerais, Brazil

This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2010 J. Phys.: Conf. Ser. 217 012059 (http://iopscience.iop.org/1742-6596/217/1/012059) View the table of contents forthis issue, or go to the journal homepage for more

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International Conference on the Applications of the Mössbauer Effect (ICAME 2009) IOP Publishing Journal of Physics: Conference Series 217 (2010) 012059 doi:10.1088/1742-6596/217/1/012059

IronOxides of Fazendão Deposit, East Border of Quadrilátero Ferrífero, Minas Gerais, Brazil
A R P Pereira1,2, F J Rios2, C A Rosière3, J D Fabris1
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Departamento de Química – Universidade Federal de Minas Gerais, Brasil Centro de Desenvolvimento da Tecnologia Nuclear – CDTN, Minas Gerais, Brasil 3 Instituto de Geociências – Universidade Federal de Minas Gerais, Brasil
2

E-mail:arpp@qui.dout.ufmg.br

Abstract. The iron oxides highly influence the soil structure and aggregation of mineral particles in soil. They also play an important role in some economical variables, as those related to the use of land for agriculture practices or mineral exploitation, in ore mining activities. About 60 % of all industrial activities on iron processing in Brazil is based on ores mined in the geodomainof Quadrilátero Ferrífero, state of Minas Gerais, Brazil. Samples of a mining area for iron, the Fazendão Deposit in the east border of Quadrilátero Ferrífero have been studied in an attempt to contribute to a better understanding of the key chemical and mineralogical pathways related to the formation and transformation of iron oxides, involving hematite. From powder diffraction patterns, it isconfirmed that hematite is the main mineralogical phase in all samples. The total iron contents were found to range between 65.15 and 70.00 mass%. The saturation magnetization values, σ = 6.9 and 2.1 J T-1 kg-1, are significantly measurable only for the two samples showing some evidences of magnetite. 298 K-Mössbauer data confirmed the dominant occurrence of hematite in all samples, along withmagnetite for the two samples showing non-zero magnetization. 110 K-Mössbauer data indicate that the hematite in all samples undergoes the Morin transition (TM ≈ 260 K), as expected for the relatively pure oxide. Maghemite could not be detected in any sample. New numerical analysis are now being performed, using Rietveld refinement of XRD data, in an attempt to obtain crystallographic results thatcould indicate more reliable evidences about the mechanisms of formation of hematite, particularly in the magnetic samples, for which the precursor is presumably magnetite.

1. Introduction Iron oxides are found in large proportions in nature, being the most abundant metal oxides in soils. They rank second in the mineralogical occurrence order in the clay fraction of tropical and subtropicalpedosystems, following the kaolinite group [1]. Iron oxides play an important influence on some critical properties of the geo-superficial layer, such those related to the use of land for agriculture practices or involved in the genesis of iron ore deposits [2]. About 60 % of all starting material used in industrial processing of iron in Brazil comes from exploitation of mines in the geodomain broadlyknown as Quadrilátero Ferrífero, in the state of Minas Gerais, Brazil. Itabirite is the dominant metamorphical hematite-rich rock of that area [3]. The

c 2010 IOP Publishing Ltd

1

International Conference on the Applications of the Mössbauer Effect (ICAME 2009) IOP Publishing Journal of Physics: Conference Series 217 (2010) 012059 doi:10.1088/1742-6596/217/1/012059

name “itabirite”...
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