Summary:
The Southeastern System mines are located in the Quadrilatero Femfero (Iron Quadrangle).
Ore reserves with high ratios of itabirite ore relative to hematite ore type. Itabirite ore has iron grade of 35-60%.
The Quadrilátero Ferrífero (QF) comprises an area of about 7000 km2 and hosts one of the largest concentrations of lateritic iron-ore deposits in the world. The QF is located in central Minas Gerais state, southeastern region of Brazil (Dorr, 1965). The QF has a quadrangular shape due to the dome and basin structures of the Minas Supergroup. Most of the iron ore in the QF are hosted in the oxidized, metamorphosed and heterogeneously deformed Banded Iron Formations (BIFs) of the Cauê Formation, the so-called itabirites. The BIFs are altered sedimentary deposits with laminated rocks formed by alternating layers of silica and hematite magnetite, as well as carbonates and iron silicates.
The Quadrilátero Ferrífero is located at the southeastern border of the São Francisco Craton, southeastern Brazil. According to Alkmim and Marshak (1998) the most important lithostratigraphic units of the Quadrilátero Ferrífero are: (1) the Archean crystalline basement, (2) the Rio das Velhas Supergroup, (3) the Minas Supergroup, (4) the Post-Minas Intrusives and (5) the Itacolomi Group.
Basement crystalline rocks include a gneiss/migmatite complex and two generations of voluminous Late Archean plutons: calk-alkaline and anorogenic granites (Alkmim and Marshak, 1998). The Rio das Velhas Supergroup consists of greenstone (basalt and komatiite), rhyolitic lava and intercalated sedimentary rocks. Sedimentary units of the Rio das Velhas Supergroup include Algoma-type banded-iron formations (BIFs), carbonates and siliciclastics. The Minas Supergroup is a metasedimentary unit that unconformably overlies the Rio das Velhas Supergroup. According to Alkmim and Marshak (1998), the Minas Supergroup strata resist erosion, forming ridges that tower above the regions which are underlain by less resistant basement or greenstone rocks. These characteristics of the Minas Supergroup shaped the geomorphology of the southern Brazil highlands giving rise to high relief in this region. Alluvial conglomerate and sandstone made up the basal units of the Minas Supergroup. These units grade upward into shallow-water marine pelites of the Tamanduá and Caraça Groups. The Lake Superior-type Cauê banded-iron Formation lies on Caraça metasediments. The Cauê Formation is a carbonate sequence of the Gandarela Formation. Lying locally unconformably on the Gandarela Formation, the Piracicaba Group comprises a thick pile of shallow-water and deltaic strata. Separated from the Piracicaba Group by an unconformity, the Sabará Group is a thick sequence of turbidites, tuffs, volcaniclastics, conglomerates and diamictites derived from a source to the east–southeast. The PostMinas intrusives comprise thin, undated, pegmatite veins cutting Minas rock (Alkmim and Marshak, 1998; Herz, 1970). Finally, the Itacolomi Group is a unit consisting of alluvial sandstones, conglomerates and minor pelites (Dorr, 1969) deposited in intramontane grabens (Alkmim and Martins-Neto, 2012).
The main iron ore types in the Iron Quadrangle are:
Hematite: Hematite represents the high-grade ore type within the iron deposit. The iron content varies from 65 to 67 percent. It is either massive or foliated in nature. The hematite is classified according to its physical and chemical characteristics as Compact Hematite, Friable Hematite, and Goethitic / Argilitic Hematite. Its origin is related to hydrothermal or metasomatic processes.
Itabirite: Itabirite is a term widely used in Brazil to denote a metamorphosed iron formation composed of iron oxides (hematite, magnetite, and martite), abundant quartz, very rarely mica, and other accessory minerals. It may be foliated or compact. The un-enriched (poor) itabirites from the Quadrilatero Ferrffero tend to have little magnetite, and composed principally of quartz-hematite, quartz-hematite-carbonate and hematite-carbonate. Itabirite represents the majority of reserves and resources of the Iron Quadrangle deposits. According to Vale, it was originated by silica leaching and residual iron-oxide enrichment process during post-metamorphic weathering cycles. The iron content averages about 45 percent, and occasionally it may reach up to 60 percent. The Itabirite ore is classified according to its physical and chemical characteristics as Compact Itabirite, Friable Itabirite, Goethitic / Argilitic Itabirite or Ochre.
Canga: Canga ore consists of unconsolidated talus material formed by the weathering of the iron formation. The iron content ranges significantly, with generally high concentration of phosphorous and alumina.
Rolados: A second detrital mineralization type. Consists of a ferruginous or lateritic matrix with fragments and blocks of different materials such as hematite, itabirite, quartz; high Fe grade, with high contaminant levels, such as P and Al203.s.
The Itabira complex is located in the northeastern corner of the Quadrilatero Femfero (Iron Quadrangle). It is enclosed by a local geologic structure that appears separated from the regional Iron Formation. The geologic structure consists of a 14-kilometer long, NE-trending range that shows three main synclines at both extremes (Conceicao and Caue) and middle (Minas do Meio) sections. The synclines branch out to the west from the general structure, and have created appropriate conditions to hold massive concentrations of the iron mineralization.
High-grade ores of Hematite and Itabirite, in continuous occurrence, are extracted along the structure, from the Conceicao mine at the southwest end to the Caue mine in the NE side of the range. The ore reserves at the Caue have been depleted. The Minas do Meio mine consists of numerous deposits located along the geologic structure, such as the Corpo D, Periquito, Dois Corregos, Onca, and Chacrinha.
The Minas Centrais Complex includes the northern portion of the Quadrilatero Ferrifero (Iron Quadrangle), due east from the city of Belo Horizonte. It includes three NE-SW trending branches of the Formacion Ferrifera outcroppings, with a projected total extension of approximately 115 kilometers. The main branch, over 60 kilometers long, holds the deposits of Brucutu in the northern portion, Gongo Soco in the central part, and the Maquine project in the southern extension. The Bau deposit is located in the middle branch of the Formacion Ferrifera outcroppings, which represents a folded extension of the main branch. The Agua Limpa f Cururu mine is enclosed by an independent branch of the Formacion Ferrifera outcroppings, to the east of the Complex area.
Summary:
The Itabira Mining Complex has three major beneficiation plants. Minas Centrais Complex has two major beneficiation plants and one secondary plant. Mariana complex has three major beneficiation plants.
The beneficiation process for the run of mine consists of standard crushing, classification and concentration steps, producing sinter feed, lump ore and pellet feed.
The typical mineral processing operations for iron ore include ore size reduction via crushing and milling, classification by sieves or cyclones, mineral recovery (concentration) via gravity separation, flotation and/or magnetic separation, and dewatering (filtering). On a particle size basis, there can be four (interconnected) processing streams: coarse (e.g. +8 mm), medium (+1-8 mm), fine (+0.15-1 mm), and very fine (-0.15 mm). These may result in the production of iron ore concentrates in the form of lumps (coarse), sinter feed fines (fine to medium), and pellet feed fines (fine and very fine). The fines products have to undergo an additional agglomeration step, at the plant or elsewhere, such as sintering and pelletizing respectively, resulting in improved mechanical properties as well as a partial change in the chemical content. Iron ore fines products typically have higher iron content and attract a premium price.
As at 2020, in addition to wet processing, a number of enterprises such as Brucutu, Alegria, Fábrica Nova, Fazendão also use dry processing.
The plants that use dry processing in Minas depend on the availability of high-grade ore - around 60% - that can be found in some mines of the state.
Dry processing is associated with the quality of the iron ore from the mine face. In some mines of Minas Gerais, the average content is 40% iron in rocks known as itabirite. To increase its grade, the ore is concentrated through processing with water, and the tailings are disposed of in dams. Then, the high-grade ore resulting from this process can be transformed into pellets at the pelletizing plants to increase the added value of the product.
Capanema Maximization project:
Capanema project increases flexibility in the Southeastern System with Brazilian Blend Fines (BRBF) feed addition.
- 18 Mtpy capacity of sinter feed production using natural moisture processing
- Increasing operational flexibility of Timbopeba
- Start-up in 1H25.
Tailings filtration plants:
In order to treat the tailings from wet processing, we are investing in tailings filtration systems to allow the reduction of disposal of tailings in dams and also to operate certain mines and plants without using tailings dams. Vargem Grande Complex, Itabira Complex and Brucutu to be operated with tailings filtration systems and dry stacking tailings disposal, which consists of filtering and stacking of partially dewatered tailings, reducing our reliance on tailings dams. In 2023, Vale invested US$144 million in tailings filtration system and dry stacking tailings disposal, and Vale started the operation of the Itabira Complex (Cauê and Conceição) and Brucutu filtration plants.
Recoveries & Grades:
| Commodity | Parameter | 2023 | 2022 | 2021 |
|
Iron Ore
|
Recovery Rate, %
| 66.1 | 69.6 | 71 |