Figure 1.
Geological map of the Iron Quadrangle, with São Francisco Craton location (A) and Mineiro Belt (B).
Figure 2.
Caraça Group: (A) MOE1 facies - polymictic conglomerate - outcrop (X = 605,202; Y = 7,775,277; Z = 1,384 m); (B) MOE2 facies hand specimen - Au-bearing conglomerate with rounded detrital pyrites (Ouro Fino Mine - Jaguar Mining Inc.); (C) MOE4 facies - poorly sorted sandstone with trough cross-bedding - outcrop (X = 609,027.087; Y = 7,756,449.81; Z = 1,243.7 m); (D) MOE3 facies - poorly sorted sandstone with tabular cross-bedding and tangential foresets - outcrop (X = 604,540.709; Y = 7,779,506.869; Z = 1,343.9 m). Coordinates are in UTM and WGS84 datum.
Figure 3.
Itabira Group: (A) CAU1 facies - itabirite (X = 638,416.18; Y = 7,807,618.25; Z = 1,713 m); (B) GDR1 and GDR3 facies - dolomite and dolomitic mudstone (X = 643,411.603; Y = 7,746,329.701; Z = 1,081.6 m); (C) GDR1 facies - iron-rich dolomite (X = 638,900.029; Y = 7,781,831.391; Z = 1,383.2 m); (D) GDR2 facies - microbial mats dolomite hand specimen with well-preserved domal and laterally linked hemispheroids stromatolites and oncolites (X = 638,928.07; Y = 7,781,028.66; Z = 1,270 m). Coordinates are in UTM and WGS84 datum.
Figure 4.
Piracicaba Group: (A) CCD1, CCD4, and CCD5 facies - carbonaceous shale, ferruginous sandstone, and quartz sandstone (X = 640,038.668; Y = 7,741,900.304; Z = 1,274.5 m); (B) CCD6 facies - rithmite with hummocky cross-stratification (X = 611,172.722; Y = 7,792,421.984; Z = 1,107.6 m); (C and D) FF2 facies hand specimen - stromatolite (X = 636,590.210; Y = 7,742,150.558; Z = 1,103.0 m); (E) FF4 facies - rhythmite with hummocky cross-stratification (X = 612,218.012; Y = 7,768,982.647; Z = 1,245.2 m); (F) FF2 and FF1 facies - dolomite lens within mudstones (X = 645,411.412; Y = 7,745,965.808; Z = 1,145.5 m). Coordinates are in UTM and WGS84 datum.
Figure 5.
Sabará Group: (A) SAB5 facies - very crenulated rhythmite, or distal turbidite (X = 655,490.229; Y = 7,741,168.287; Z = 1,365.5 m); (B) SAB3 and SAB5 facies - laminated mudstone and rhythmite, or distal turbidites (X = 655,498.996; Y = 7,741,106.157; Z = 1,384.3 m); (C) SAB4 (sandstone / wacke) and SAB2 (diamictite) facies contact (X = 655,498.996; Y = 7,741,106.157; Z = 1,384.3 m); (D) SAB1 gravelly conglomerate with graded bedding, deposited by turbidity currents (X = 614,564.714; Y = 7,767,873.112; Z = 1,241.1 m). Coordinates are in UTM and WGS84 datum.
Figure 6.
Itacolomi Group: (A) ITA3 facies - gravelly sandstone with planar stratification (X = 657,277.655; Y = 7,739,784.725; Z = 1,586.1 m); (B) ITA5 facies - gravelly sandstone with trough cross-bedding (X = 641,790.022; Y = 7,731,895.969; Z = 1,322.7 m). Coordinates are in UTM and WGS84 datum.
Figure 7.
Palaeogeography of the rift stage of the Minas Basin: Moeda Formation. Compass and rose diagrams indicate sediment flow direction based on current day geographic coordinates (A is from Moeda Syncline; B is from Curral Ridge; C is from Gandarela Syncline). Palaeocurrent data are from the authors’ fieldworks, interpretations of facies lateral variations, and Villaça (1981Villaça J.N. 1981. Alguns aspectos sedimentares da Formação Moeda. Boletim, 2. Minas Gerais: Sociedade Brasileira de Geologia, Núcleo Minas Gerais.).
Figure 8.
Passive margin sedimentation within Minas Basin.
Figure 9.
Sabará Group foreland (flysch) sedimentation. São Francisco palaeo-craton lies to NW and orogenic belt to SE. Compass indicates sediment flow direction based on current day geographic coordinates.
Figure 10.
Itacolomi Group foreland (molasse) sedimentation. Reverse faults represent the Mineiro Belt orogenesis. Compass indicates sediment flow direction based on current day geographic coordinates.
Figure 11.
Foreland Basin Sequence Stratigraphy proposition and its application in Sabará and Itacolomi Groups within Minas Basin (Underfilled and Overfilled Foreland, respectively).
Figure 12.
Chronostratigraphic chart of Minas-Itacolomi Basins. Ages for the stratigraphic units are according to
Alkmim and Martins-Neto (2012Alkmim F.F., Martins-Neto M.A. 2012. Proterozoic first-order sedimentary sequences of the São Francisco craton, eastern Brazil. Marine and Petroleum Geology, 33(1):127-139. https://doi.org/10.1016/j.marpetgeo.2011.08.011
https://doi.org/https://doi.org/10.1016/...
). Black triangles indicate sea-level rise (triangle pointing upwards) and fall (pointing downwards)
.
Figure 13.
Detrital zircon U-Pb ages statistics: histograms, adaptive Kernel Density Estimates (KDEs), and Probability Density Plots (PDPs). (A) Moeda Formation. (B) Batatal Formation. (C) Cauê Formation. (D) Cercadinho Formation. (E) Sabará Group. (F) Itacolomi Group.
Figure 14.
Detrital zircon U-Pb ages statistics: histograms, adaptive Kernel Density Estimates (KDEs), and Probability Density Plots (PDPs). (A) Rift stage. (B) Passive margin stage. (C) Foreland stage.
Table 1.
Iron Quadrangle lithostratigraphic summary.
Table 2.
Main geological events in Quadrilátero Ferrífero.
Table 3.
Caraça Group facies and sedimentary processes.
Table 4.
Itabira Group facies and sedimentary processes.
Table 5.
Piracicaba Group facies and sedimentary processes.
Table 6.
Sabará Group facies and sedimentary processes.
Table 7.
Itacolomi Group facies and sedimentary processes.