Geology and geochemistry of the águas Claras and Pico Iron Mines, Quadrilátero Ferrífero, Minas Gerais, Brazil

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• 作者：Carlos Alberto Spier ; Sonia Maria Barros de Oliveira and Carlos Alberto Rosière
• 关键词：Banded iron ; formation ; Itabirite ; Iron ore ; Quadril&aacute ; tero Ferr&iacute ; fero ; &Aacute ; guas Claras ; Pico
• 刊名：Mineralium Deposita
• 出版年：2003
• 出版时间：September 2003
• 年：2003
• 卷：38
• 期：6
• 页码：751-774
• 全文大小：2,712 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geology
  Mineral Resources
  Mineralogy
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-1866

文摘

The &Aacute;guas Claras and Pico Mines are two world-class iron-ore mines hosted within the Lower- Proterozoic banded iron-formations (locally known as itabirites) of the Minas Supergroup located in the Quadril&aacute;tero Ferr&iacute;fero district, Minas Gerais, Brazil. The Águas Claras orebody consists of a 2,500-m-long roughly tabular-shaped lens hosted within the dolomitic itabirite of the Cau&ecirc; Formation. Dolomitic itabirite is the protore of the soft high-grade iron ore, which is the main ore type of the Águas Claras orebody, representing about 85% of the 284 Mt mined since 1973, with the remaining 15% comprising hard high-grade ore. Hematite is the main constituent of the iron ores. It occurs as martite, granular hematite and locally as specularite. Magnetite appears subordinately as relicts within martite and hematite crystals. Gangue minerals are very rare. These consist of dolomite, chlorite, talc, and apatite, and are especially common in contact with the protore. This virtual absence of gangue minerals is reflected in the chemistry of ores that are characterized by very high Fe contents (an average of 68.2% Fe).The Pico orebody is a continuous ~3,000-m-long body of a lenticular shape hosted within siliceous itabirite, which is the protore of the soft high- and low-grade ores at the Pico Mine. The soft high-grade ores, together with the low-grade ores, called iron-rich itabirite, are the main types of ore, and respectively represent approximately 51 and 29% of the reserves. The remaining 20% consists of hard high-grade ore. The iron oxide mineralogy is the same as that of the Águas Claras Mine, but in different proportions. Gangue minerals are very rare in the high-grade ores, but are slightly more common in the iron-rich itabirite. Quartz is the dominant gangue mineral, and is found with minor quantities of chlorite. The chemistry of the high-grade ores is characterized by high Fe contents (an average of 67.0%) and low P, Al<sub>2sub>O<sub>3sub>, and SiO<sub>2sub>, which are concentrated in the fines. Iron-rich itabirites average 58.6% Fe and 13.5% SiO<sub>2sub>.