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Evidence for metre-scale variations in hematite composition within the Palaeoproterozoic Itabira Iron Formation, Minas Gerais, Brazil

Published online by Cambridge University Press:  05 July 2018

A. R. Cabral ,
B. Lehmann ,
H. F. Galbiatti  and
O. G. Rocha Filho
A. R. Cabral*
Affiliation:
Department of Exploration Geology, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa
B. Lehmann
Affiliation:
Institut für Mineralogie und Mineralische Rohstoffe, Technische Universität Clausthal, Adolph-Roemer-Str. 2A, Clausthal-Zellerfeld, D-38678, Germany
H. F. Galbiatti
Affiliation:
Companhia Vale do Rio Doce, Itabira–MG, 35900-900, Brazil
O. G. Rocha Filho
Affiliation:
Companhia Vale do Rio Doce, Fazenda Gongo Soco, Barão de Cocais–MG, 35970-000, Brazil
*
*E-mail: A.Cabral@ru.ac.za
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Abstract

Hematite is a mineral the chemical composition of which rarely differs significantly from stoichiometric Fe2O3. As such, little attention has been paid to the mineral chemistry of hematite in Precambrian iron formations, where hematite forms monomineralic high-grade orebodies. Electron microprobe analysis of hematite from two iron-ore deposits, Cauê (Itabira district) and Gongo Soco, in the Palaeoproterozoic Itabira Iron Formation, Quadrilátero Ferrífero of Minas Gerais, Brazil, has revealed distinct variations in chemical composition with respect to Ti and Cr. Hematite containing Ti and/or Cr is of very local occurrence in the itabirite unit and shows a spatial relationship to hematitic, palladiferous gold-bearing veins (known as ‘jacutinga’), occurring either within the veins (adjacent to, or included in, palladiferous gold grains) or in their vicinity. Where present, titaniferous hematite (to ∼1.3 wt.% TiO2) is lepidoblastic and defines a pervasive tectonic foliation (S1). In contrast, Ti-free, chromiferous hematite (to ∼6.4 wt.% Cr2O3) characteristically occurs as inclusions in palladiferous gold within S1-truncating ‘jacutinga’. Replacement of granoblastic, Ti-free, chromiferous martite with relicts of magnetite by lepidoblastic, Cr-depleted, titaniferous hematite proves that Cr and Ti were mobile during metamorphism. Chromium was ultimately fractionated into the hematite found in auriferous aggregates within cross-cutting ‘jacutinga’. A positive correlation between Cr and Pt in bulk-rock samples from the Itabira district suggests that Cr is a potential prospective guide for Au-Pd-Pt-bearing hematitic veins (‘jacutinga’).

Keywords

mineral chemistry of hematitehigh-grade hematite depositspalladiferous gold mineralizationPalaeoproterozoic Itabira Iron FormationQuadrilátero FerríferoMinas GeraisBrazil
Type
Research Article
Information
Mineralogical Magazine , Volume 70 , Issue 5 , October 2006 , pp. 591 - 602
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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References

Alkmim, F. F. and Marshak, S. (1998) Transamazonian orogeny in the Southern São Francisco craton region, Minas Gerais, Brazil: evidence for Paleoproterozoic collision and collapse in the Quadrilátero Ferrífero. Precambrian Research, 90, 29–58.CrossRefGoogle Scholar
Babinski, M., Chemale, F. Jr. and Van Schmus, W. R. (1995) The Pb/Pb age of the Minas Supergroup carbonate rocks, Quadrilátero Ferrífero, Brazil. Precambrian Research, 72, 235–245.CrossRefGoogle Scholar
Barbosa, A. L. M. and Grossi Sad, J. H. (1973) Tectonic control of sedimentation and trace-element distribution in iron ores of central Minas Gerais (Brazil). Proceedings of the Kiev Symposium, 1970, UNESCO, Earth Sciences, 9, 125–131.Google Scholar
Beukes, N. J., Gutzmer, J. and Mukhopadhyay, J. (2003) The geology and genesis of high-grade hematite iron ore deposits. Applied Earth Science (Transactions of the Institution of Mining and Metallurgy B), 112, B18-B25.CrossRefGoogle Scholar
Bustillo, M. A., Garcia-Guinea, J., Martinez-Frias, J. and Delgado, A. (1999) Unusual sedimentary geodes filled by gold-bearing hematite laths. Geological Magazine, 136, 671–679.CrossRefGoogle Scholar
Cabral, A. R. (2003) Spessartine-tourmaline-bearing manganiferous itabirite at Miguel Congo: petrographic evidence for a Mn-rich meta-exhalite in the Quadrilátero Ferrífero of Minas Gerais, Brazil. Applied Earth Science (Transactions of the Institution of Mining and Metallurgy B), 112, B313–B318.CrossRefGoogle Scholar
Cabral, A. R. (in press) Palladiferous Gold Mineralisation (ouro preto) in Brazil: Gongo Soco, Itabira and Serra Pelada. Geologisches Jahrbuch, Sonderhefte, Reihe D, Heft SD 8, E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.Google Scholar
Cabral, A. R. and Lehmann, B. (2003) A two-stage process of native palladium formation at low temperatures: evidence from a palladian gold nugget (Gongo Soco iron ore mine, Minas Gerais, Brazil). Mineralogical Magazine, 67, 453–463.CrossRefGoogle Scholar
Cabral, A. R., Lehmann, B., Kwitko, R. and Jones, R. D. (2002 a) Palladian gold and palladium arsenide-antimonide minerals from Gongo Soco iron ore mine, Quadrilátero Ferrífero, Minas Gerais, Brazil. Applied Earth Science (Transactions of the Institution of Mining and Metallurgy B), 111, B74–B80.CrossRefGoogle Scholar
Cabral, A. R., Lehmann, B., Kwitko, R., Galbiatti, H. F. and Pereira, M. C. (2002 b) Palladseite and its oxidation: evidence from Au-Pd vein-type mineralization (jacutinga), Cauê iron-ore mine, Quadrilátero Ferrífero, Minas Gerais, Brazil. Mineralogical Magazine, 66, 327–336.CrossRefGoogle Scholar
Cabral, A. R., Lehmann, B., Kwitko, R., Jones, R. D. and Rocha Filho, O. G. (2003 a) On the association of palladium-bearing gold, hematite and gypsum in an ouro preto nugget. The Canadian Mineralogist, 41, 473–478.CrossRefGoogle Scholar
Cabral, A. R., Rocha Filho, O. G. and Jones, R. D. (2003 b) Hydrothermal origin of soft hematite ore in the Quadrilátero Ferrífero of Minas Gerais, Brazil: petrographic evidence from the Gongo Soco iron ore deposit. Applied Earth Science (Transactions of the Institution of Mining and Metallurgy B), 112, B279–B286.CrossRefGoogle Scholar
Cabral, A. R., Suh, C. E., Kwitko-Ribeiro, R. and Rocha Filho, O. G. (in press) Brittle microstructures in gold nuggets: a descriptive study using backscattered electron imaging. Ore Geology Reviews. Google Scholar
Chauvet, A., Faure, M., Dossin, I. and Charvet, J. (1994) A three-stage structural evolution of the Quadrilátero Ferrífero: consequences for the Neoproterozoic age and the formation of gold concentrations of the Ouro Preto area, Minas Gerais, Brazil. Precambrian Research, 68, 139–167.CrossRefGoogle Scholar
Chemale, F. Jr., Quade, H. and Carbonari, F. S. (1987) Economic and structural geology of the Itabira Iron District, Minas Gerais, Brazil. Zentralblatt für Geologie und Paläontologie Teil I, 7/8, 743–752.Google Scholar
Chemale, F. Jr., Rosière, C. A. and Endo, I. (1994) The tectonic evolution of the Quadrilátero Ferrífero, Minas Gerais, Brazil. Precambrian Research, 65, 25–54.CrossRefGoogle Scholar
Dorr, J. V. N. (1965) Nature and origin of the high-grade hematite ores of Minas Gerais, Brazil. Economic Geology, 60, 1–46.CrossRefGoogle Scholar
Dorr, J. V. N. (1969) Physiographic, stratigraphic and structural development of the Quadrilátero Ferrífero, Minas Gerais, Brazil. United States Geological Survey Professional Paper, 641-A, 110 pp.Google Scholar
Dorr, J. V. N. and Barbosa, A. L. M. (1963) Geology and ore deposits of the Itabira district, Minas Gerais, Brazil. United States Geological Survey Professional Paper, 341-C, 110 pp.Google Scholar
Essarraj, S., Boiron, M.-C., Cathelineau, M. and Fourcade, S. (2001) Multistage deformation of Au-quartz veins (Laurieras, French Massif Central): evidence for late gold introduction from micro-structural, isotopic and fluid inclusion studies. Tectonophysics, 336, 79–99.CrossRefGoogle Scholar
Galbiatti, H. F. (1999) Natureza e Controle Estrutural da Mineralização Aurifera (Jacutinga) na Mina do Cauê, Itabira, MG. M.Sc. thesis (unpublished), Departamento de Geologia, Universidade Federal de Ouro Preto, Ouro Preto, Brazil, 150 pp.Google Scholar
Harder, E. C. and Chamberlin, R. T. (1915) The geology of central Minas Geraes, Brazil. Journal of Geology, 23,341–378, 385-424.CrossRefGoogle Scholar
Henwood, W. J. (1871) On the gold mines of Minas Geraes, in Brazil. Transactions of the Royal Geological Society of Cornwall, 8, 168–370.Google Scholar
Hippertt, J. and Davis, B. (2000) Dome emplacement and formation of kilometre-scale synclines in a granite-greenstone terrain (Quadrilátero Ferrífero, southeastern Brazil). Precambrian Research, 102, 99–121.CrossRefGoogle Scholar
Hoefs, J., Müller, G. and Schuster, A. K. (1982) Polymetamorphic relations in iron ores from the Iron Quadrangle, Brazil: the correlation of oxygen isotope variations with deformation history. Contributions to Mineralogy and Petrology, 79, 241–251.CrossRefGoogle Scholar
Hussak, E. (1904) über das Vorkommen von Palladium und Platin in Brasilien. Sitzungsberichte der mathematisch-naturwissenschaftlichen Klasse der Kaiserlichen Akademie der Wissenschaften, 113, 379–468.Google Scholar
Jedwab, J. and Cassedanne, J. (1998) Historical observations on oxygen-bearing compounds of platinum and palladium in Minas Gerais, Brazil. The Canadian Mineralogist, 36, 887–893.Google Scholar
Johnson, P. N. and Lampadius, W. A. (1837) Ueber brasilianisches Palladgold und dessen Ausbringen und Scheidung. Journal für praktische Chemie, 11, 309–315.Google Scholar
Kessler, W. and Müller, G. (1988) Minor and trace-element data of iron oxides from iron-formations of the Iron Quadrangle, Minas Gerais, Brazil. Mineralogy and Petrology, 39, 245–250.CrossRefGoogle Scholar
Klein, C. and Ladeira, E. A. (2000) Geochemistry and petrology of some Proterozoic banded iron-formations of the Quadrilátero Ferrífero, Minas Gerais, Brazil. Economic Geology, 95, 405–428.CrossRefGoogle Scholar
Lagoeiro, L. E. (1998) Transformation of magnetite to hematite and its influence on the dissolution of iron oxide minerals. Journal of Metamorphic Geology, 16, 415–423.CrossRefGoogle Scholar
Lobato, L. M., Ribeiro-Rodrigues, L. C., Zucchetti, M., Noce, C. M., Baltazar, O. F., Silva, L. C. and Pinto, C. P. (2001) Brazil's premier gold province. Part I: The tectonic, magmatic, and structural setting of the Archean Rio da Velhas greenstone belt, Quadrilátero Ferrífero. Mineralium Deposita, 36, 228–248.CrossRefGoogle Scholar
Lüders, V., Romer, R. L., Cabral, A. R., Schmidt, C., Banks, D. A. and Schneider, J. (2005) Genesis of itabirite-hosted Au-Pd-Pt-bearing hematite-(quartz) veins, Quadrilátero Ferrífero, Minas Gerais, Brazil: constraints from fluid inclusion infrared microther-mometry, bulk crush-leach analysis and U-Pb systematics. Mineralium Deposita, 40, 289–306.CrossRefGoogle Scholar
Mücke, A. (2005) The Nigerian manganese-rich iron-formations and their host rocks – from sedimentation to metamorphism. Journal of African Earth Sciences, 41, 407–436.CrossRefGoogle Scholar
Olivo, G. R., Gauthier, M., Bardoux, M., Sá, E. L., Fonseca, J. T. F. and Santana, F. C. (1995) Palladium-bearing gold deposit hosted by Proterozoie Lake Superior-type iron-formation at the Cauê iron mine, Itabira district, southern São Francisco craton, Brazil: geologic and structural controls. Economic Geology, 90, 118–134.CrossRefGoogle Scholar
Pires, F. R. M. (1995) Textural and mineralogical variations during metamorphism of the Proterozoie Itabira Iron Formation in the Quadrilátero Ferrífero, Minas Gerais, Brazil. Anais da Academia Brasileira de Ciências, 67, 77–105.Google Scholar
Rosière, C. A. and Rios, F. J. (2004) The origin of hematite in high-grade iron ores based on infrared microscopy and fluid inclusion studies: the example of the Conceição mine, Quadrilátero Ferrífero, Brazil. Economic Geology, 99, 611–624.CrossRefGoogle Scholar
Rosière, C. A., Siemes, H., Quade, H., Brokmeier, H.-G. and Jansen, E. M. (2001) Microstructures, textures and deformation mechanisms in hematite. Journal of Structural Geology, 23, 1429–1440.CrossRefGoogle Scholar
Touzeau, E. M. (1892) Gold-mining in Brazil. Transactions of the Federated Institution of Mining Engineers, 4, 219–232.Google Scholar