TITLE:
Meaning of Rocks Basic Enclaves in the Eburnean Granitoids of Mako Area (Kédougou-Kéniéba Inlier, Senegal): Petrogenetic Implications
AUTHORS:
Ibrahima Gassama, Moussa Dabo, Mamadou Ndiaye, Emmanuel Tama Samoura, Fatou Bop Ndong
KEYWORDS:
Paleoproterozoic, Kédougou-Kéniéba, Mako, Granitoids, Basic Enclave, Birimian
JOURNAL NAME:
International Journal of Geosciences,
Vol.12 No.1,
January
29,
2021
ABSTRACT: The Mako
area, located in eastern Sénégal, constitutes a segment of Paleoproterozoic (Birimian) formations of the
Kédougou-Kéniéba Inliers (KKI) in the western part of the West African craton. The basic
volcanism of the Birimian formations of the KKI has long been considered to be
related to a single magmatic event associated with a Mid Oceanic Ridge Basalts
(MORB) setting. The aim of this paper is to demonstrate on the basis of the architectural
characteristics of the granitoids dark enclaves, the occurrence of at least two
distinct phases of basic Magamtism in the Birimian of the KKI. The
methodology consists of a cartography, a petrographic and architectural
characterization of the dark enclaves within the Mako granitoids, in order to
constrain their spatial and temporal relationships with the granitic magma. The
results obtained are compared with those of the bibliography. We have
pinpointed two types of enclaves depending on their shapes and the
characteristics of their edge with the enclosing rocks: angular enclaves with
straight edges (ante-granitoids) and the soft enclaves with uneven edges
(syn-granitoids). The enclaves with straight and well-defined rectilinear edges
(ante-granitoids) would be linked to a basic magma which is already
consolidated before being fragmented, torn and carried away as enclaves in the
granitoids. These enclaves would come from enclosing outcrops of metabasalts
and metagabbros which are locally cross-cut by the
granitoids. The soft enclaves with uneven edges (syn-granitoids) were co-magmatic and
not solid during their incorporation into the granitoids. They come from a
basic magma which is contemporaneous to the granitic one. Thus, the
occurrence of two generations of dark enclaves is related
to, at last, two different phases of basic magmatism in the Birimian formations
of the KKI.