The Statherian itabirite-bearing sequence from the Morro Escuro Ridge,Santa Maria de Itabira,Minas Gerais,Brazil |
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| Institution: | 1. Graduate Program, Instituto de Geociências, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil;2. Instituto de Geociências, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil;3. Departamento de Geologia, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil;4. Graduate Program, Instituto de Geociências, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil;5. Centre for Exploration Targeting, University of Western Australia, Perth, Australia;6. Curtin University of Technology, Perth, Australia;1. Department of Mineral Processing, Iron Ore, Vale S.A., Brazil;2. Department of Mining and Petroleum Engineering, Universidade de São Paulo, Brazil;3. JKMRC-SMI, The University of Queensland, Australia;4. Department of Metallurgical and Materials Engineering, Universidade Federal do Rio de Janeiro – COPPE/UFRJ, Brazil;1. Departamento de Geologia, Escola de Minas, Universidade Federal de Ouro Preto, Morro do Cruzeiro, 35.400-000 Ouro Preto, MG, Brazil;2. Petra Energia S.A. Alameda Oscar Niemeyer, 500- Vila da Serra, 34.000-000 Nova Lima, MG, Brazil;1. Instituto de Geociências-CPMTC, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Campus Pampulha, 30130-009 Belo Horizonte, Minas Gerais, Brazil;2. Instituto de Geociências, Universidade de Brasília, Campus Darcy Ribeiro ICC, Ala Central, 70910-900, Brasília, Distrito Federal, Brazil;3. Instituto de Geociências, Universidade Federal da Bahia, Av. Caetano Moura, S/N, Federação, 40000-000 Salvador, Bahia, Brazil;4. Centre de Recherche en Géochimie et en Géochronologie, GEOTOP, Université du Québec a Montréal, CP 8888 Succ. A, Montréal, Quebec H3C 3P8, Canada;5. Departamento de Geologia, Universidade Federal de Ouro Preto, Morro do Cruzeiro, Bauxita, 45400-000 Ouro Preto, Minas Gerais, Brazil;1. Universidade Federal dos Vales do Jequitinhonha e Mucuri, Programa de Pós-Graduação em Geologia, CeGeo-ICT, Campus JK - Rodovia BR 367, Km 583, n° 5000, Alto da Jacuba, 39100-000 Diamantina, MG, Brazil;2. Laboratório de Estudos Tectônicos, CeGeo-ICT, Campus JK - Rodovia BR 367, Km 583, n° 5000, Alto da Jacuba, 39100-000 Diamantina, MG, Brazil;3. Universidade Federal de Minas Gerais, Programa de Pós-Graduação em Geologia, CPMTC-IGC, Campus Pampulha - Av. Antônio Carlos, 6627, Pampulha, 31270-901 Belo Horizonte, MG, Brazil;1. Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, São Paulo, SP 05508-090, Brazil;2. Instituto de Geociências, Universidade de São Paulo, São Paulo, Rua do Lago, 562, SP 05508-080, Brazil |
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| Abstract: | The itabirite-bearing metasedimentary sequence from Morro Escuro Ridge comprises the basal units of the Espinhaço Supergroup and makes up a small tectonic inlier developed during one of the Brasiliano orogenic events (800-500 Ma), amongst horses of the Archean TTG gneisses, including sheared granites of the anorogenic Borrachudos Suite (∼1700 Ma). The metasedimentary rocks are comprised of low-to intermediate-amphibolite facies schists, quartzites, conglomerates and banded iron formation (itabirite) correlatable with the sequences of the Serro Group, which underlies the metasedimentary rocks of the Espinhaço Supergroup in the Serra da Serpentina Ridge. A maximum Statherian deposition age (1668 Ma) was established using SHRIMP U–Pb isotopic constraints on zircon grains from conglomerate and quartzite units overlying the itabirite. The itabirite is predominantly hematitic and its geochemical characteristics are typical of a Lake Superior-type BIF deposited in a platformal, suboxic to anoxic environment distant from Fe-bearing hydrothermal vents. Close to the contact zone with amphibolites of the Early Neoproterozoic Pedro Lessa mafic suite, an increase of the magnetite content and crystallization of metasomatic Mg-hornblende and Ce-allanite can be observed. These mineralogical changes developed preferentially along the igneous contact zone but are probably co-genetic with the formation of alteration haloes in zircon grains during the Neoproterozoic Brasiliano orogeny (506 ± 6 Ma). |
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| Keywords: | Morro Escuro Ridge Serro group Itabirite Geochemistry |
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