TITLE:
Geochemical and Petrological Insights into the Neoproterozoic Moumba Metabasites: Implications for Crustal Processes in the West Congo Belt (Republic of Congo)
AUTHORS:
Ulrich Verne Matiaba-Bazika, Nelson Lekeba Makamba, Vicky Tendresse Télange Bouénitéla, Nicy Carmelle Bazebizonza Tchiguina, Timothée Miyouna, Florent Boudzoumou
KEYWORDS:
Mayombe, Metabasites, Moumba, Mantle Plume, Continental Rifting, Basalts Flood Continental
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.12 No.2,
February
7,
2024
ABSTRACT: The West Congo Belt contains in its rocks of Neoproterozoic age from
Nemba complex outcropping in the Moumba River. This West Congo belt is made up
of a crustal segment of the Arcuaï-West Congo orogen which extends from
southwest Gabon to the northeast of Angola. This study aims to constrain the geochemical signature
Nemba complex of West Congo belt from the petrograhic and geochemical study on
the whole rock. The petrographic data from this study show the
Moumba metabasites are made up of amphibolites, metagabbros, epidotites and
greenschists interstratified in the Eburnean metasediments and affected by
mesozonal to epizonal metamorphism characterized by the retromorphosis of
intermediate amphibolite facies minerals into greenschist facies. Whole-rock
geochemical data indicate that these metabasites are continental flood basalts
(CFB) of basic nature and transitional affinity emplaced in intraplate context.
These continental flood basalts are
generated from magma originating from a significantly enriched shallow mantle
plume and this magma then contaminated by the continental crust during their
ascent. The reconstruction of tectonic signature suggests that West Congo belt
would result from closure of an ocean basin with subduction phenomena. This
collision would be marked by the establishment of ophiolite complex. We show
that this model is incompatible with the CFB nature of metabasites and the
orogenic evolution of Neoproterozoic. It does not seem that we can evoke a
genetic link with a subduction of oceanic crust, because the paleogeography of
Neoproterozoic (Rodinia) is marked by intracontinental rifts linked to opening
of Rodinia. We therefore suggest the non-existence of ophiolitic complex in
western Congo belt and reject the collisional model published by certain
authors. We confirm the currently available intracontinental orogen model.