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5930459 
Journal Article 
Geochemistry of canga (ferricrete) and evolution of the weathering profile developed on itabirite and iron ore in the Quadrilatero Ferrifero, Minas Gerais, Brazil 
Spier, CA; Levett, A; Rosiere, CA 
2019 
1 
Mineralium Deposita
ISSN: 0026-4598 
54 
7 
983-1010 
WOS:000485905800003 
Mineralogical and whole rock geochemical analyses for 60 elements on 31 samples of hard ferruginous crust (canga) provide insights into the evolution of the lateritic profile developed on itabirite. Canga can form in two environments: in situ canga that typically caps itabirite and transported canga that covers country rock. Both have similar mineralogical and chemical compositions. Detrital haematite and rare quartz inherited from the itabirite and iron ore comprise the matrix of canga, cemented by goethite, minor gibbsite, and rare manganese oxides and secondary phosphates. Fe2O3 represents more than 91% of its chemical composition and the concentrations of trace elements are low, generally less than 50 ppm. A comparison of the chemical weathering of dolomitic itabirite against the quartz itabirite shows that, although weathering processes are less effective in the former, the geochemical trends of major and trace elements are similar. Negative Ce anomalies (Ce/Ce* = 0.8) and U/Th ratios lower than 1.5 suggest that saprolite formation occurred under slightly anoxic and mildly acidic conditions, allowing rare earth elements (REEs) to remain in the saprolite and also the formation of secondary Al phosphates, instead of Fe phosphates. These conditions became more aggressive during the canga formation process, resulting in further removal of trace elements from the system. The canga formation (pedogenesis) and the chemical weathering of the itabirite (saprolite formation) are independent, but interrelated processes that have been occurring since the Palaeocene. 
Canga; Ferricrete; Geochemistry; Strengite; Iron ore; Quadrilatero Ferrifero