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The mainland of Equatorial Guinea (Rio Muni) offers the wide variety
of mineral potential that is expected on an Archaean cratonic
setting with later Pan-African overprinting; with possibilities
for gold, diamond, columbo-tantalite, platinum-group elements,
bauxite and base metals.
Rio Muni comprises the Archaean terranes of the Ntem Complex and
the Monts de Cristal Massif of the northern Congo Craton, both
of which were partly re-worked during the Paleoproterozoic Eburnian
orogeny. They consist of largely granitic gneisses, charnockites, mafic
intrusions and broad mylonitic shear zones (including an Eburnian
terrane boundary), with subordinate amounts of banded ironstones,
metasediments, and post-orogenic intrusions. Pan African transpressional
structures are common in the west and are associated with granitic
intrusions and pegmatite bodies, which also occur throughout the
interior. Sub-greenschist shales, argillaceous dolomites, and
quartzites occur in the southwest. Higher-grade sedimentary packages,
also attributed to the Pan-African, are found along the northern
border of the country where they are associated with major strike-slip
and thrust faults and post-tectonic granitic intrusions.
The coastal strip of Rio Muni comprises Cretaceous sands, shales,
and carbonates with basal conglomerates, all deposited during
the rifting phase of Atlantic opening. Trans-Atlantic fracture
zones link to major onshore lineaments, at least one of which
shows evidence of Cenozoic rifting (the Benito Rift). |
