5/15/2009. Carajas District. Urucum District. Quadrilatero Ferrifero. Location of the four cratons

Transcrição

1 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

2 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

3 QF Geologic Structural Map Minas Supergroup Classic Stratigraphy 3

4 Stratigraphy QF x HP 4

5 NW-SE Basin 2.8 Ga Consolidation of the Pilbara G-G G T Ga Fortescue Volcanism 5

6 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

7 NE-SW Basin ~2.6 Ga Deposition of the Hamersley Group Fm. Moeda Fm. Batatal Fm. Cauê Minas Supergroup Classic Stratigraphy 7

8 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

9 Batatal & Cauê Formations Carbonaceous Phyllite, Sericite Phyllite, Chert, Carbonates. Turbidites? Pyrite Nodules (Oxidized to Hematite) Slump folds in sandstones Batatal Formation 9

10 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

11 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

12 Dolomitic Itabirite REE-signature from itabirites 12

13 Dolomitic Itabirite 750µ 13

14 Isotopes in Carbonates Kuruman BIFs Dolomitic Itabirite Griquatown BIFs Gandarela Dolomite Organic C Goethitic Itabirite 100m 100m 750m 14

15 Amphibolitic/ Goethitic Itabirite 750m Pisoliths in Itabirite 15

16 Fm Gandarela Fm. Cercadinho Disc. angular e erosiva Ferruginous Oncoliths in Dolomite 16

17 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

18 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

19 Piracicaba Group Sabará - The Foreland Basin Ga (?) Submarine fan with NW- ward debris flow and turbidity currents 19

20 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

21 Neoproterozoic sediments 21

22 Transamazonian Orogeny 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

23 Tectonic Axes in the Hamersley Basin Ophtalmian Orogeny/ Panhandel Folding Taylor et al., 2001, vs. Müller et al.,

24 Uplift and Erosion Uplift of Gnaisse Domes Orogenic Collapse? 24

25 The Formation of Fe- High-Grade Ores! Fe -Mineralization Fe -Mineralization 2 Fe -Mineralization 1 25

26 Deformation and Folding The folding mechanism (flexural- slip folding) was very important for the development of suitable sites for mineralization Deformation and Folding 26

27 Hypogene Ores: Low Strain Domains Hypogene Ores 27

28 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 km ESCALA N GALINHEIRO P I C O SAPECADO 28

29 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

30 Curvas de nível de 100 em 100 metros Córrego do Tijuco km km 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 E Córrego da Estiva 1000 CórregoLaranjeira 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 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 metros Escala Original: 1: 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: Cemig 1986 Leonardo MORATO Mapas Topográficos Fecho do Funil e Ibirité 1: IBGE DEPARTAMENTO DE GEOLOGIA IGC/UFMG ESCALA ORIGINAL: 1: A A 30

31 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?? ?????????? ??????? /15/2009 Bocaina N N??? β ??? Bocaina Velha N β ?????? Aterro Aterro 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 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 ( Structure of the Serra dos Franceses A B 31

32 Tamanduá 32

33 Ores Fabrics in Western Domain Ores Fabrics in Western Domain 33

34 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

35 Plot of ice-melting temperatures versus temperatures of homogenisation 35

36 High-grade ore from dolomitic itabirite Fe-Rich Dolomite Register of Fe- mineralization 36

37 High-grade ore from dolomitic itabirite 37

38 Hypogene Ore: High Strain Hypogene Ore: High Strain 38

39 Ores Fabrics from the Eastern Domain 39

40 Deformation and Precipitation Fabrics 40

41 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 o C High salinity 40µ 41

42 Diagram of Fluid Evolution Total melting of solid phase T >350 o C Agua Quente Fault 42

43 Hematite N 20 Piracicaba Group BIF Lineations/ minor fold hinges Cauê 25 Nova Lima Group and older Poles to S1a (contoured) Chacrinha Poles to S2 Lineations/ minor fold hinges Onça Dois Córregos Syncline (F/F) 1b 2 Poles to S1a (contoured) 80 Periquito 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) m The Itabira Syncline 43

44 Conceição Structurally thickened BIF in refolded fold The Conceição Iron Ore Deposit 44

45 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

46 The Brasiliano Orogeny Cauê Fm. The Cambotas Fundão Thrust Espinhaco SG. 46

47 Fe-Mobilization in the Espinhaço SG 47

48 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

49 Uplift and Minor Formation Iron of Remobilization Present Configuration High-Grade Iron Orebodies Part II 500 ma. Hematite Ga erosion present day surface Brasiliano Orogeny 49