Morphological and compositional characterization
of gold contained in ferricretes of a weathered
profile (Minvoul greenstone belt, Gabon)
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Publication date
2018
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Sociedad Española de Mineralogía
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Abstract
This study presents the quantification and morphological
characterization of particles and nuggets of almost pure
gold found in the iron duricrust of a weathering profile
of the Archean greenstone belt of Minvoul (Republic of
Gabon). The weathered profile on the area (Figure 1)
was defined through pits and trenches and consists, from
bottom to top, on saprolite, mottled clay zone, iron
duricrust, pisolitic gravels and yellow latosol. The iron
duricrust constitutes a hard continuous layer, which is
concretionary and pisolitic and consists of cemented
nodules of goethite, hematite and other iron oxides and
hydroxides. Samples from this horizon contain abundant
particles of gold. The study of morphology and
microchemical composition of gold grains has been
widely used as a tool for the understanding of the
dissolution, dispersion and gold concentration processes
in supergene environments, and for determining the
primary or secondary origin of gold grains across the
lateritic horizons (Webster and Mann, 1984; Butt and
Hough, 2006). Moreover, the results obtained represent
a contribution for the knowledge of the gold-potential of
the Ntem complex greenstone belts where
mineralization on bedrock remains unknown.