Civil Engineering / Environmental / Architecture / Planning Session:

Title:            Genesis and paragenesis of the tetravalent Mn ores and Mn-Fe ores in secondary banded iron formations from Nigeria
Authors:       Sahr Fillie
Abstract:      The geology and petrography are presented for the Nigerian iron-formations and their supergene products. The iron formations which form alternate bedding with phyllite and mica schist consist of two mineralogic facies; oxides and silicates. Supergene alterations have affected these facies to varying degrees. Consequently, secondary minerals/phases in different proportions occur as replacement products of the dominantly pre-existing minerals (amphibole, garnet, magnetite, Mn-ilmenite and quartz) of the iron formations. They form either pseudomorphs after precursor minerals, veins or inhomogenous replacement textures that obliterate original structure. The principal secondary minerals are: todorokite (Mg-free and Mg-rich), nsutite, pyrolusite (formed also directly from manganomelane), asbolane, lithiophorite, Manganomelane (romanechite, cryptomelane; reflects higher), limonite and Mn-Fe hydroxides. The mode of association of the minerals and a detailed paragenesis have been established.

Pages:           318-328

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