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Aguas Claras, Pico |
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Minas Gerais, Brazil |
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Fe
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Super Porphyry Cu and Au
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The Aguas Claras and Pico Mines are two iron-ore mines hosted by Palaeoproterozoic banded iron-formations (itabirites) of the Minas Supergroup in the Quadrilátero Ferrífero district of Minas Gerais, near Belo Horizonte, Brazil.
For detail of the regional setting, geology and stratigraphy of the host sequence and district see the Quadrilatero Ferrifero Iron Province
The Aguas Claras orebody is a 2500 m long, roughly tabular-shaped lens hosted within the dolomitic itabirite of the Caue Formation. The dolomitic itabirite protore of the soft high grade iron ore - which represents approximately 85% of the 284 Mt mined since 1973. The remaining 15% comprised hard high-grade ore.
Hematite is the main ore mineral, occurring as martite, granular hematite and locally as specularite. Magnetite is subordinately, found as relicts within martite and hematite crystals. Gangue minerals are very rare and comprise dolomite, chlorite, talc, and apatite, mainly found at the contact with the un-enriched protore. This average grade is 68.2% Fe.
The Pico orebody is a continuous, lenticular shaped body, about 3000 m long. It is hosted within siliceous itabirite, the protore of soft high- and low-grade ores at this mine. The soft high-grade ores, together with the low-grade ores, called iron-rich itabirite, are the main types of ore, and represent approximately 51 and 29% of the reserves respectively. The remaining 20% comprises of high-grade hard ore. The iron oxide mineralogy is the same as that of the Aguas Claras Mine, but in different proportions. Gangue minerals are very rare in the high-grade ores, but are a little more common in the iron-rich itabirite. Quartz is the dominant gangue occurring with minor amounts of chlorite. The high-grade ores is characterised by an average of 67.0% Fe with low P, Al2O3, and SiO2, which are concentrated in the fines. Iron-rich itabirites average 58.6% Fe and 13.5% SiO2.
The soft high-grade ores and iron-rich itabirites are interpreted to have been the result of supergene processes whereby ground water leached the gangue minerals leaving the residual iron oxides of the itabirites. This process was favoured by the tropical climate and topographic situation. The original composition of the itabirites and the presence of structures controlling the circulation of the groundwater have influenced the degree of iron enrichment. The hard high-grade ores are believed to have a hypogene origin. Their genesis is attributed to hydrothermal solutions that leached the gangue minerals and filled the spaces with hematite.
The most recent source geological information used to prepare this decription was dated: 2003.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Spier C A, De Oliveira S M B, Rosiere C A 2003 - Geology and geochemistry of the Aguas Claras and Pico Iron Mines, Quadrilatero Ferrifero, Minas Gerais, Brazil: in Mineralium Deposita v38 pp 751-774
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Spier C A, de Oliveira S M B, Rosiere C A and Ardisson J D, 2008 - Mineralogy and trace-element geochemistry of the high-grade iron ores of the Aguas Claras Mine and comparison with the Capao Xavier and Tamandua iron ore deposits, Quadrilatero Ferrifero, Brazil : in Mineralium Deposita v43 pp 229-254
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Spier C A, de Oliveira S M B, Sial A N and Rios F J, 2007 - Geochemistry and genesis of the banded iron formations of the Caue Formation, Quadrilatero Ferrifero, Minas Gerais, Brazil: in Precambrian Research v152 pp 170-206
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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