3th WCSET-2014 at Nepal
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