Iron Formations in Brazil A Focus in the Iron Quadrangle Tectonic Map of South America Carajas District Urucum District Location of the four cratons Quadrilatero Ferrifero 1
Location of the main BIF-bearing Basins at 2.0 Ga. K. Rog Kursk Labrador F Derik Nimba, Simandou Bailadilla Hamersley Naberu L. Superior Carajás QF Goa Orissa Middleback Kapvaal The São Francisco Craton and Surrounding Orogenic Belts 2
QF Geologic Structural Map Minas Supergroup Classic Stratigraphy 3
Stratigraphy QF x HP 4
NW-SE Basin 2.8 Ga Consolidation of the Pilbara G-G G T. 2.8 2.6 Ga Fortescue Volcanism 5
First record of the MSG ~2.45 Ga Beginning of break up of Late Archean supercontinents Rifting, Dyke swarm injection 2449? 3 Ma Large Igneous Province (Woongara) Opening of the Minas Basin and BIF Deposition 6
NE-SW Basin ~2.6 Ga Deposition of the Hamersley Group Fm. Moeda Fm. Batatal Fm. Cauê Minas Supergroup Classic Stratigraphy 7
Platformal Where is the Rift Sequence? Environment on a Passive Margin Classic Minas SG starts with widespread fluvio-deltaic environment Minas SG Rift Sequence Candidates? 8
Batatal & Cauê Formations Carbonaceous Phyllite, Sericite Phyllite, Chert, Carbonates. Turbidites? Pyrite Nodules (Oxidized to Hematite) Slump folds in sandstones Batatal Formation 9
Deposition of Iron Formations Itabira Group (Cauê/Gandarela) Single unit Key layer Association Pelagites (Batatal)/IF (Cauê) Hamersley Gp: Marra Mamba, Brockman, Weeli Wolli, Bolgeeda ~3x thickness Sub-volcanic/ volcanic/vulcanoclastics in Itabirite Hamersley: Woongara LIP Local sills and volcanoclastic layers 10
Plagioclase / fluidal fabric (500x) Euhedral quartz with shards (500X) Hematitized shards (1000x) Ignimbrite clast in chlorite matrix (500x) Different types of Itabirite! Not necessarily Facies! 11
Dolomitic Itabirite REE-signature from itabirites 12
Dolomitic Itabirite 750µ 13
Isotopes in Carbonates Kuruman BIFs Dolomitic Itabirite Griquatown BIFs Gandarela Dolomite Organic C Goethitic Itabirite 100m 100m 750m 14
Amphibolitic/ Goethitic Itabirite 750m Pisoliths in Itabirite 15
Fm Gandarela Fm. Cercadinho Disc. angular e erosiva Ferruginous Oncoliths in Dolomite 16
The gradation from iron formation to dolomitic iron formation and the presence of two stratigraphic levels of intraformational conglomerate and pelitesindicate indicate two uplift events of the basin related to its incomplete inversion with very weak and local development of intraformational fold structures, specially in the iron formation layer D 2 Deformation/McGrath Trough/Foreland Basin Cercadinho Cgl/Piracicaba Gp Uplift aborted orogenesis? 17
Lower Piracicaba Group (Cercadinho Fm) Erosional unconformity that separates the Itabira from the Cercadinho Fm/Piracicaba Group with the development of BIF-Pebble conglomerate, Fe -rich sandstones and small supergene ore bodies. Piracicaba Group L. Wyloo Group Turbidites, Carbonates, Chert Dolomites, Iron Formations Iron rich Quartzite BIF-Pebbles Conglomerate Dolomites Continental Basalts (Cheela Springs) Shallow marine/fluvial Quartzite BIF-Pebbles Conglomerate Rifting in the Hamersley Basin 2,2Ga old mafic sills 18
Piracicaba Group Sabará - The Foreland Basin 2.12 2.13 Ga (?) Submarine fan with NW- ward debris flow and turbidity currents 19
Structural Geology of the Quadrilátero Ferrífero Schematic Cross- Section W Western Low-Strain Domain Bonfim Gneiss Dome Moeda Syncline Bação Gneiss Dome Eastern High-Strain Domain Thrusts from the Cambotas-Fundão System Santa Rita Syncline E Minas Supergroup Rio das Velhas Supergroup Granite-Gneiss Complex Transamazonian Faults Brasiliano Faults 20
Neoproterozoic sediments 21
Transamazonian Orogeny 2. 2 2.0 Ga (?) NE-SW-trending Folds and superposed ~ NW-SE Folding Hamersley - The Ophtalmian Orogeny 2.14 Ga Ophtalmian Fold Belt/ Panhandel Folding? Lower Panhandel Wyloo Folding Group Extension/Rifting Ophtalmian Orogeny Mafic sills/rifting Synorogenic sedimentation Sabará Foreland Basin Transamazonian Upper Piracicaba Orogeny Group 22
Tectonic Axes in the Hamersley Basin Ophtalmian Orogeny/ Panhandel Folding Taylor et al., 2001, vs. Müller et al., 2005 23
Uplift and Erosion Uplift of Gnaisse Domes Orogenic Collapse? 24
The Formation of Fe- High-Grade Ores! Fe -Mineralization Fe -Mineralization 2 Fe -Mineralization 1 25
Deformation and Folding The folding mechanism (flexural- slip folding) was very important for the development of suitable sites for mineralization Deformation and Folding 26
Hypogene Ores: Low Strain Domains Hypogene Ores 27
F 1 ^ F 2 Folds Weakly or locally developed Schistosity Loci for Fe- mineralization The Mutuca Fault! Channelway for the fluids? CAPÃO XAVIER MUTUCA JANGADA MAR AZUL MUTUCA Fault TAMANDUÁ FEIJÃO SERRA DA MOEDA BELO HORIZONTE CAPITÃO DO MATO ABÓBORAS Tectonic Control in the Western Domain 0 10 20 30 km ESCALA N GALINHEIRO P I C O SAPECADO 28
Córrego do Feijão Original surface Córrego do Feijão Structural Cross- Section Amphibolitic itabirites High-grade ore Dolomitic itabirites Dolomitic phyllite Banded phyllite Bonfim Complex (granite-gneisses) 29
800 800 800 800 Curvas de nível de 100 em 100 metros 800 800 900 800 900 1000 1100 70 65 60 Córrego do Tijuco 900 5 72 84 60 65 40 35 1000 80 45 5 km 5 5 5 5 5 5 5 900 800 65 35 1400 1200 1000 800 600 900 1200 50 80 65 1300 75 70 30 1300 1100 35 40 1200 900 35 900 40 1000 45 1400 900 60 65 60 30 40 40 60 62 50 50 800 900 1200 900 1000 1200 1100 1200 1000 1400 1200 1000 800 600 7 7 7 7 km 40 60 80 Indiviso: xistos e filitos intemperizados Formação Barreiro: filitos grafitosos Formação Taboões: ortoquartzitos Formação Cercadinho: quartzitos e filitos ferruginosos Formação Gandarela: dolomitos e filitos dolomíticos Formação Batatal: filitos sericíticos a grafitosos Formação Moeda: filitos,quartzitos e quartzo xistos Contato, tracejado quando inferido Falha, tracejada quando inferida. Anticlinal, traço do plano axial e caimento do eixo Sinclinal, traço do plano axial e caimento do eixo Direção e mergulho de camadas Direção e mergulho de foliação Direção e mergulho de camadas invertidas Mina Drenagens Estradas principais Estradas secundárias 5/15/2009 Serra do Curral Model of Structural Evolution Metassediments (Minas Sg) Gneisses (Bonfim Cplx) Serra do Curral W Segment Rio Paraopeba MAPA GEOLÓGICO E SEÇÃO DO SEGMENTO OESTE DA SERRA DO CURRAL, QUADRILÁTERO FERRÍFERO, MG 1100 1000 900 1200 82 E 84 86 88 90 92 94 96 Córrego da Estiva 1000 CórregoLaranjeira 800 1100 Córrego do Engenho Seco Córrego dos Três Irmãos A A 900 Córrego Valongo SERRA DOS TRÊS IRMÃOS 1000 Córrego do Feijão 1100 Córrego Laranjeiras 800 Ribeirão Casa Branca 80 78 76 74 N TERCIÁRIO E QUATERNÁRIO PROTEROZÓICO ARQUEANO Supergrupo Minas Grupo Sabará Grupo Piracicaba Grupo Itabira Grupo Caraça Complexo Bonfim Coluna Estratigráfica Rolados: depósitos, constituídos de blocos de hematita compacta e itabiritos Canga: colúvio de itabirito e hematita cimentada por óxidos de Fe Formação Fecho do Funil: filitos dolomíticos e metasiltitos Formação Cauê: itabiritos silicosos e anfiboliticos com lentes de hematita Gnaisse Souza Noschese: gnáisses, granitos e milonitos CONVENÇÕES 1000 0 1000 2000 metros Escala Original: 1: 25.000 Mapeamento Geológico do segmento oeste da Serra do Curral; Quadrilátero Ferrífero - MG DESENHO: Mapa Geológico-Estrutural Provisório REFERENCIAS: AUTORES: Júlio D ALESSANDRO; Luedson MANDUCA; Fotos aéreas 1:30.000 Cemig 1986 Leonardo MORATO Mapas Topográficos Fecho do Funil e Ibirité 1:25.000 - IBGE DEPARTAMENTO DE GEOLOGIA IGC/UFMG ESCALA ORIGINAL: 1:25.000 A A 30
273700 273800 Saprólito argiloso laminado - intercalado no quartzo itabirito Quartzo Itabirito e Brechas Silicificados Quartzo Itabirito - l imonítico Filito Carbonoso - localmente mineralizado com ocorrência de veios Minério Friável Minério Compacto Soleiras e Corpos Irregulares saprólito - de rocha intrusiva xistosa?? 273900?????????? 274000??????? 274100 274200 274300 274400 274500 274600 274700 274800 5/15/2009 Bocaina N 2777300 N??? β 2777200 20??? Bocaina Velha N β 2777100 70?????? Aterro 2777000 Aterro 2776900 CENOZÓICO CONVENÇÕES fanglomerados com argila, matacões e blocos diversos de hematita compacta e itabirito Formação Cauê Bocaina Nova 50 Quartzo Itabiritos Goethíticos - localmente com intercalações de níveis argilosos laminados e pseudomorfos de anfibólios PROTEROZÓICO 2776800 SupergrupoMinas Grupo Itabira Quartzo Itabirito Rico - limonítico, mineralizado em ferro, localmente apresenta intercalações argilosas Filito Mineralizado - filito de origem indefinida, intensamente mineralizado em Ferro Limite Inferior d ) Rochas Intrusivas a Forma inferido eco Cauz ( 2776700 Structure of the Serra dos Franceses A B 31
Tamanduá 32
Ores Fabrics in Western Domain Ores Fabrics in Western Domain 33
Hematite I Hematite II polygonal overgrowth FI-2 Hm II Hm II FI-2 Infrared Images - Fl in Hematite II Th = 115 to 145 o C Low to intermediate salinity FI-2 Hm II FI-1 FI-1 Hm II 34
Plot of ice-melting temperatures versus temperatures of homogenisation 35
High-grade ore from dolomitic itabirite Fe-Rich Dolomite Register of Fe- mineralization 36
High-grade ore from dolomitic itabirite 37
Hypogene Ore: High Strain Hypogene Ore: High Strain 38
Ores Fabrics from the Eastern Domain 39
Deformation and Precipitation Fabrics 40
FI (001) Tab Hem Infrared Images - Tab. Hematite Specularite twinning lamellae qtz Hm aggreg. Spec. Hm aggreg. Infrared Images Fl in Tab. Hematite Th = 120 to 140 o C High salinity Specularite Th prob. 350 400 o C High salinity 40µ 41
Diagram of Fluid Evolution Total melting of solid phase T >350 o C Agua Quente Fault 42
Hematite N 20 Piracicaba Group BIF Lineations/ minor fold hinges Cauê 25 Nova Lima Group and older Poles to S1a (contoured) Chacrinha 44 76 Poles to S2 Lineations/ minor fold hinges Onça Dois Córregos 55 84 Syncline (F/F) 1b 2 Poles to S1a (contoured) 80 Periquito 44 70 Syncline (F) 1a Thrust (D) 1 Conceição 65 Dolerite dike Source: CVRD Structural data: de Melo et al. (1986) Chemale (1987) and Rosiere (pers com) 0 2000m The Itabira Syncline 43
Conceição Structurally thickened BIF in refolded fold The Conceição Iron Ore Deposit 44
Dois Córregos NW Folded thrust stack F1-F1 a b SE Hematite Soft BIF Piracicaba Group BIF Nova Lima Group and older Length between pin lines: 104m Original bed length: 42m Shortening: 75% NW Present Section E 21 source: CVRD/ de Melo (1986) SE 0 400m Imbricate thrust stack, F1 a Preserved Eroded NW Pin Pin SE Reconstructed undisturbed section Site of future hematite formation N-S Basin 45
The Brasiliano Orogeny Cauê Fm. The Cambotas Fundão Thrust Espinhaco SG. 46
Fe-Mobilization in the Espinhaço SG 47
Formation of High-Grade Iron Orebodies Part I Magnetite and Fe-Dolomite 2.2 Ga? prob. Metamorphic Fluids Formation of High-Grade Iron Orebodies Part II Hematite 48
Uplift and Minor Formation Iron of Remobilization Present Configuration High-Grade Iron Orebodies Part II 500 ma. Hematite 2.12 2.16 Ga erosion present day surface Brasiliano Orogeny 49